Oncocytes are cells that have abundant eosinophilic cytoplasm due to the accumulation of mitochondria; they are also known as oxyphils. In the thyroid they have been called Hürthle cells but this is a misnomer, since Hürthle described C cells; for this reason, we propose the use of “oncocyte” as a scientific term rather than an incorrect eponym. Oncocytic change occurs in nontumorous thyroid disorders, in benign and malignant tumors of thyroid follicular cells, in tumors composed of thyroid C cells, and intrathyroidal parathyroid proliferations as well as in metastatic lesions. The morphology of primary oncocytic thyroid tumors is similar to that of their non-oncocytic counterparts but also is complicated by the cytologic features of these cells that include both abundant eosinophilic cytoplasm and large cherry red nucleoli. The molecular alterations in oncocytic thyroid tumors echo those of their non-oncocytic counterparts but in addition feature mitochondrial DNA mutations as well as chromosomal gains and losses. In this review we emphasize the importance of recognition of the spectrum of oncocytic thyroid pathology. The cell of origin, morphologic features including architecture, nuclear atypia and invasive growth, as well as high grade features such as mitoses and necrosis, enable accurate classification of these lesions. The molecular alterations underlying the pathological entity are associated with genetic alterations associated with oncocytic change. The arbitrary cut-off of 75% oncocytic change to classify a lesion as an oncocytic variant brings another complexity to the classification scheme of tumors that frequently have mixed oncocytic and non-oncocytic components. This controversial and often confusing area of thyroid pathology requires thoughtful and cautious investigation to clarify accurate diagnosis, prognosis and prediction for patients with oncocytic thyroid lesions. The term “oncocyte” was applied to describe cells that have abundant eosinophilic cytoplasm due to the accumulation of mitochondria. The term “oxyphil” has also been used, because of their acidophilic cytoplasm, but this term is less specific since other mechanisms can lead to cytoplasmic acidophilia. “Oncocytosis” derives from the Greek word for swelling or mass, forming the basis for the discipline of oncology. In pathology, oncocytic change is a proliferation of mitochondria within the cell.This metaplastic change occurs normally with aging in many organs; the prime example is the parathyroid gland where oncocytes are not seen at birth but increase with age , 2. The Oncocytes in the thyroid have been called Hürthle cells but this is a misnomer. Hürthle described the clear cells found associated with thyroid follicles that we now recognize as calcitonin-producing neuroendocrine C cells of the thyroid gland; he did not describe oncocytes . In factGene associated with Retinoid-Interferon-induced Mortality (GRIM)-19 -19 . AdditioThis review will discuss the phenomenon of oncocytic change in thyroid cells in various pathological conditions and the implications it brings to diagnosis, prognosis and prediction.Oncocytic change is a characteristic feature of chronic lymphocytic thyroiditis (Hashimoto thyroiditis)  Figure . They are distinguished based on the degree of nuclear atypia, which is considered to be mild in follicular carcinoma, and is more evident in FVPTC , 28. TumMolecular analyses have shown that follicular carcinoma and encapsulated follicular variant papillary carcinoma are both RAS-like lesions , 30 thatFollicular patterned neoplasms including follicular carcinoma and FVPTC, can exhibit oncocytic cytology Figure 52), creating potential challenges that may explain relatively lower rates of RAS-like molecular profiles and higher rates of high-risk molecular alterations in these studies ; solid growth also encompasses trabecular and insular/nested architecture. These oncocytic forms of solid variant papillary thyroid carcinomas can be difficult to recognize as papillary carcinomas due to the difficulty of appreciating the extent of nuclear atypia of papillary thyroid carcinoma in oncocytes; however, there is often a papillary and/or follicular growth component as well. The differential diagnosis is oncocytic poorly differentiated carcinoma, as the solid growth may indicate dedifferentiation, but the distinction is based on lack of necrosis and mitoses that are characteristic of high-grade malignancies. Importantly, the differential diagnosis of oncocytic solid variant papillary thyroid carcinoma includes oncocytic medullary thyroid carcinoma , 50 and TERT promoter mutations and occasional mutations of ATRX and/or DAXX (TERT promoter mutation portents a more aggressive clinical course with distant metastatic spread, and reduced iodine uptake. The clinical relevance of recognizing this tumor classification has been highlighted by a recent study showing a distinctive immune-related gene expression profile of oncocytic poorly differentiated thyroid carcinomas, not only confirming that this is a more aggressive cancer subtype but also pointing to a potential role for immunotherapy in the management of these high-grade malignancies (A subset of classical “Hürthle cell carcinoma” actually represents a poorly differentiated tumor with predominant solid growth and widely invasive behaviour 9, often/or DAXX , 37. As gnancies .The existence of oncocytic medullary thyroid carcinoma is well documented , 12, 18 RET mutations and less common RAS mutations that occur in non-oncocytic medullary thyroid carcinomas.Little is known about the molecular alterations that underlie the oncocytic variant in addition to the frequent The presence of oncocytic change is not unique to thyroid, as indicated above. Therefore, the identification of an oncocytic tumor in thyroid must also include consideration of a possible metastatic oncocytic neoplasm, including renal and other primary sites, as well as an infiltrating oncocytic tumor, such as a parathyroid, salivary gland or thymic tumor arising in the region of the thyroid.This review has identified the unique features of oncocytic cells and tumors in the thyroid but has also emphasized the importance of recognizing the similarities of oncocytic pathologies in this gland with those of their non-oncocytic counterparts.A critical issue to remember is that most oncocytic lesions can be diffusely or focally oncocytic with variable non-oncocytic components , 17. IntThe data point to heterogeneity of oncocytic thyroid lesions and significant overlap between oncocytic and non-oncocytic lesions, both morphologically and at the molecular level, with additional complexities of the morphologic and molecular alterations of oncocytic change. This complexity has created confusion both for pathologists who must classify these lesions and for clinicians who must treat the patients. Thus, we emphasize the importance of recognition of the spectrum of oncocytic change in thyroid pathology, based on cell of origin, morphology that includes architecture, nuclear atypia and invasion, as well as high grade features such as mitoses and necrosis, and the molecular alterations underlying both the pathological entity as well as the oncocytic change. Only with such a thoughtful and cautious approach will it be possible to clarify accurate diagnosis, prognosis and prediction for patients with oncocytic thyroid pathology.SA and OM: substantial contributions to conception and design, acquisition of data or analysis and interpretation of data, drafting the article or revising it critically for important intellectual content. All authors contributed to the article and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


The major aim of radiation therapy is to provide curative or palliative treatment to cancerous malignancies while minimizing damage to healthy tissues. Charged particle radiotherapy utilizing carbon ions or protons is uniquely suited for this task due to its ability to achieve highly conformal dose distributions around the tumor volume. For these treatment modalities, uncertainties in the localization of patient anatomy due to inter- and intra-fractional motion present a heightened risk of undesired dose delivery. A diverse range of mitigation strategies have been developed and clinically implemented in various disease sites to monitor and correct for patient motion, but much work remains. This review provides an overview of current clinical practices for inter and intra-fractional motion management in charged particle therapy, including motion control, current imaging and motion tracking modalities, as well as treatment planning and delivery techniques. We also cover progress to date on emerging technologies including particle-based radiography imaging, novel treatment delivery methods such as tumor tracking and FLASH, and artificial intelligence and discuss their potential impact towards improving or increasing the challenge of motion mitigation in charged particle therapy. The use of charged particles for radiation therapy (RT) represents a valuable treatment paradigm because their unique dose deposition properties, including maximum dose deposition at the Bragg peak and rapid distal falloff, allow for dose to be conformed tightly around the tumor while sparing normal tissues –6. HowevCTV <97%) in comparison with IMRT, but interplay effects had an increasingly negative impact on the dose distribution as the number of simulated fractions was decreased below 10  prevent or reduce anatomical motion, or 2) adapt treatment to motion during planning or delivery. The success of these strategies depends on access to imaging techniques which allow motion and/or dose deposition to be faithfully monitored and quantified. While much work has been done to address challenges in motion related to charged particle therapy, currently there is limited standardization of treatment protocols, with many centers developing their own unique standard of procedures and best practices . For exaThis review seeks to provide an overview of current clinical practices for intra- and inter-fractional motion management in charged particle therapy as well as progress to date on emerging technologies that have potential to be used for or impact motion management. The remainder of this review is organized as follows: Section 2 provides an overview of the current state of the art in motion management implemented in clinical charged particle therapy, including motion reduction techniques at the major anatomical sites, imaging techniques for monitoring intra- and inter-fractional motion, as well as treatment planning, delivery, and plan evaluation mitigation strategies; Section 3 discusses promising ongoing research and emerging technologies in charged particle therapy which will either directly benefit or necessitate further innovations in motion management.Motion control techniques consist of methods which seek to reduce patient motion and ensure consistent geometrical orientation during and between fractions.voluntary, in which the patient is in control of their breathing  . Breath-reathing , or acti a valve . A widel a valve –34. High a valve . Not all a valve .Abdominal compression (AC) belts are a relatively inexpensive and easy-to-implement option for minimizing intra-fractional motion from respiration. For charged particle therapy, thin belts made of homogenous materials are preferred to ensure that the belt has a minimal and reproducible impact on the charged particle range . For PBSFor the lower abdomen and pelvic regions, positioning techniques focus on reducing motion caused by volume changes in the rectum and bladder. Consistency of the position of bladder and rectal volume across and during treatment can be improved through hydration and voiding schedules , 41. Recvia indirectly by imaging markers placed in tissue, e.g., fiducial markers. Computed tomography (CT) images are the gold-standard modality for treatment planning; however, CT images acquired during free breathing can suffer from motion artifacts, leading to uncertainty in the true delineation of boundaries between tumor, normal tissues, and organs at risk  and magnetic resonance imaging (MRI) for target delineation. 4DPET provides information on tumor motion in addition to the metabolic information about the tumor structure and has been shown to be a valuable tool for target delineation in lung cancers . 4DMRI pConventional cone-beam CT (CBCT) was first implemented for proton therapy for patient setup in 2012 . Daily CInternal tumor motion during delivery can be monitored through implanted markers, such as electromagnetic sensors –61 and fFluoroscopy with implanted markers can produce 2D images with high spatial and temporal resolution. Researchers at Hokkaido University in Japan have pioneered the clinical implementation of a gated proton PBS treatment system that utilizes fluoroscopy for real time tumor tracking through an internally placed gold fiducial marker –67. AsidAnother strategy for assessing tumor motion is to measure the patient’s surface motion, which can then be used as a surrogate to infer the position and movement of the internal target . SurfaceMany different strategies exist to account for patient motion during the treatment planning process or delivery itself. Mitigation during treatment planning and delivery is characterized by an approach of working with or around existing patient motion. These strategies rely on additional information input from imaging, either during simulation (in the case of treatment planning) or in real time during treatment delivery.One of the most widely used planning methods to account for expected patient motion in charged particle therapy is to delineate an additional margin around the tumor target, commonly denoted the internal target volume (ITV), which is defined as the overlay of boundaries for all (or a select subset of) CTV positions collected during 4DCT . While tA unique challenge for particle therapy in the face of intra-fractional motion is the additional dose uncertainty caused by interplay effects between patient anatomical motion and the delivery sequence of the scanning beam. A mitigation method is to use repainting, which refers to a treatment delivery method applied for PBS by rescanning over the same spot positions multiple times  , 82. StuIn treatment planning, beam angle selection can help to minimize dose deviations by selecting beam orientations that are robust to motion. Proton range is sensitive to tissue variations along the beam path. Movement can cause tissue variation uncertainties that lead to dose deposition uncertainties. Thus, in selecting beam angles for proton therapy, it is advantageous to avoid large tissue density gradients in the beam path and to try to keep the beam angle parallel to the dominant direction of tumor motion . It is aThe pencil beam spot size, defined as the full width at half-maximum of the beam spot in air, has been identified as an additional beam parameter that impacts dosimetric deviations in PBS proton therapy , 63, 76.via external surface imaging  can be used during the treatment planning process to design plans which are robust to the uncertainties associated with treatment delivery, including setup errors and patient motion. Traditionally for photons, such uncertainties in treatment planning have been accounted for by using an expanded margin around the CTV, called the planning target volume (PTV). In proton therapy, the additional presence of range uncertainties and, in the case of PBS, uncertainties from the interplay effect render the use of traditional margin-based solutions insufficient.3DRO refers to a class of robust optimization techniques which account for patient setup and range uncertainties during treatment plan optimization. Implementations of 3DRO include probabilistic treatment planning, scenario-wise mini-max RO, and voxel-wise worst-case RO. In probabilistic optimization, setup and range uncertainty scenarios are randomly sampled from an assumed probability distribution to produce a large set of potential dose distributions , 97. ThiStudies have been performed for carbon ion 4D dose reconstruction and optimization. Reconstruction of the delivered 4D RBE dose needs to consider the tumor motion and temporal structure of the beam delivery . Eley etDue to the interplay effect in proton PBS delivery, special considerations should be taken in evaluating PBS proton plans to ensure that the intended dose distribution can be delivered faithfully under conditions of anatomical motion. The guidelines provided by the Particle Therapy Co-Operative Group (PTCOG) Thoracic and Lymphoma Subcommittee recommended the use of a 4D phantom to evaluate motion interplay effects and the effectiveness of planned motion mitigation techniques, though at this time such a protocol is admittedly out of reach for most centers due to the expense of 4D phantoms , which hin vivo observation of internal anatomic structures during treatment fractions. 4D-CBCT has been recognized as a promising emerging technology in identifying intra-fractional motion at the time of treatment and has been investigated for photon therapy . PR involves measuring the residual energy of high energy protons after they have passed through the patient to construct a 2D image where each pixel represents the WET of the patient along the beam path at that position. PR has been proposed as a tool for quality control through in vivo proton range verification, as an aid for pre-treatment patient positioning, and even as a means to guide online plan adaptations  during treatment delivery through the measurement of gamma rays created from nuclear interactions with protons passing through tissue. The in vivo human applications of prompt gamma with passive scattering and PBS proton beams were reported (8) exceeds the number of photons generated in most pencil beams for RT treatment. Potential solutions to this challenge include re-optimizing the treatment plan such that several of the pencil beams are boosted to reach this counting threshold, or aggregating the statistics from multiple neighbour pencil beams (at the cost of reduced resolution) (Prompt gamma (PG) imaging is a technology that allows for reported , 149. Onolution) . A recenolution) .Detection of the secondary charged particle emission in light-ions such as carbon ion beams was also proposed for beam range monitoring purposes ; the capin vivo range verification is protoacoustics. Protoacoustics works by measuring the thermoacoustic pressure waves generated by the energy deposition of therapeutic protons in tissue. Like prompt gamma, protoacoustics is an attractive option for range verification in that it is derives its signal from the treatment beam itself, essentially utilizing free information from the patient’s internal anatomy without the need for additional dose. In addition, a protoacoustic system can be implemented at low cost compared with other methods , FLASH RT has been shown for  control –179. Mul control  includin control , 182 wer control –185. ShoArc therapy is an emerging technology in proton therapy in which the gantry is rotated continuously through a pre-selected arc during treatment delivery. ARC therapy for photons (VMAT) is a standard clinical tool with several different commercial systems available . In 2021Artificial intelligence (AI) refers to technologies or machines which can perform tasks/calculations with human-like skill and cognition. Machine learning (ML) is a subcategory of AI relating to computer algorithms which can “learn” to perform a task without being explicitly programmed to do so. Machine learning, and in particular deep learning (DL), has found tremendous success in the past decade in many diverse fields, ranging from finance to automotive technologies, and to medicine . DL als. There iDeep learning applications have been investigated for inter-fractional motion management in charged particle therapy. Van der Heyden et al. presented a single detector, multi-energy proton radiography system which relied on artificial intelligence to filter out proton scatter . In addiRelating to intra-fractional motion management, many studies have been published which apply deep machine learning towards challenges of real-time target tracking for both charged particles as well as photons. For example, Hirai et al. introduced a CNN-based model for marker-less real-time tumor tracking which was tested retrospectively on lung and liver cancer patients who received fluoroscopic imaging during carbon ion therapy . MylonasA substantial roadblock to implementing deep learning models in the clinical workflow stems from issues relating to model interpretability. Specifically, the inherent complexity of deep learning algorithms makes it difficult to understand how the models think (hence why DL models are often referred to as “black boxes”) . Though In this review, we provided an overview of the current clinical treatment methods for motion management in charged particle therapy as well as future emerging technologies and methodologies. As the use of charged particle therapy becomes more widespread and new treatment delivery modalities arise, further work will be necessary to ensure robust and accurate dose delivery. For the case of inter-fractional motion, further progress is also necessary to develop adaptive planning protocols which are triggered for clinically significant anatomical changes and can be implemented within the time and resource constraints of a clinical setting. Another important task in this field is to continue the development of imaging and tracking systems which allow for accurate localization of the tumor and internal anatomy delivery at the treatment couch prior to delivery and in real time. One limitation of most studies on motion mitigation methods is that dosimetry is used the primary evaluation metric. Future studies which can connect motion mitigation methods to clinical outcomes would aid in accelerating standardization of care.JP and WZ drafted the manuscript. AK, LD, and AR contributed with discussions, coordination, and critical revision of the manuscript. All authors contributed to the article and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


Nocardiosis is an extremely rare, opportunistic, Gram-positive bacterial infection that has a high mortality rate in those patients who are immunocompromised in the presence of disseminated disease.We describe a case of an elderly lady being treated with high-dose corticosteroids for giant cell arteritis that presented with ischaemic optic atrophy. Subsequent deterioration was accompanied by the development of subretinal lesions. Further extensive evaluation discovered she had pulmonary nocardiosis with widespread dissemination. The case has several learning points, in particular:Subretinal abscesses maybe a harbinger of serious hitherto undiagnosed infection which portend a poor prognosis.Vital signs in the immunocompromised may appear to be normal in the presence of serious infection. Ocular infections due to nocardia are uncommon and likely to be exogenous, contracted directly through trauma, surgery, or contact lens use. Endogenous infection via the haematogenous route is very rarely reported and is usually unilateral.This case was bilateral and is being reported here in order to help raise the clinician’s index of suspicion when subretinal abscess is seen, as the prognosis can be poor if this condition is not diagnosed rapidly, and especially in any form of immunocompromise. Time to presentation can also be delayed in the presence of any immunosuppression, and in this case the patient’s only other non-ophthalmic symptom was some weight loss. The case is an 82-year-old female who was originally investigated via gastroenterology for unintentional weight loss and raised inflammatory markers, with normal CT scan of thorax, abdomen and pelvis. She was subsequently diagnosed with giant cell arteritis (biopsy positive) after she presented to the eye clinic with right arteritic ischaemic optic neuropathy and jaw claudication. She received 3 pulses of intravenous methylprednisolone only to be re-admitted 2 weeks later with what was thought to be a flare of her disease. This resulted in her receiving a further 3 pulses of the same corticosteroid.She was reviewed in the neuro-ophthalmology clinic 3 weeks later appearing unwell despite normal vital signs and unremarkable physical examination. Her CRP had increased and dilated ocular fundus exam revealed bilateral subretinal lesions, which were choroidal abscesses Figure 1 .Nocardia cyriacigeorgica and imaging revealed dissemination to multiple organs. Chest x-ray now showed segmental consolidation, MRI brain showed multiple punctate lesions consistent with disseminated CNS nocardiosis; high resolution CT chest now showed scattered lung nodules, MRI spine showed appearances suggestive of a right-sided psoas abscess secondary to discitis of L4/5, and normal transoesophageal echocardiography (Figure 3 She was admitted from clinic and underwent an extensive array of investigations. Three positive blood cultures confirmed that she was suffering from Figure 3 .Despite receiving a course of intravenous antibiotics, there was no improvement in her general condition, and after discussion with family, treatment was subsequently withdrawn. The patient was transferred to the local hospice for palliative care where she died.Nocardia was named after a French microbiologist Edmund Nocard, describing veterinary infections in the nineteenth century. This opportunistic Gram-positive bacterium causes human infection mainly in the immunocompromised. The most common species that can infect humans are found in the soil, and when they cause infections, they are mostly self-limiting, unless in the immunocompromised.The genus of bacteria Nocardia infections are more often exogenous, such as corneal infection after eye trauma, but endogenous cases spread by the haematogenous route usually present as choroidal abscess in immunocompromised patients with pneumonia-like symptoms. Making the diagnosis can be challenging, so treatment might be delayed, and this case displays that there may be very little in the way of physical signs.Ocular Nocardia infections disseminate in the bloodstream, particularly intracranial lesions [It is felt that 50% of pulmonary  lesions . Dissemi lesions .Nocardia are still very rare, and in fact barely 40 cases have been reported in the literature in the past 50 years [Nocardia must be included in the differential diagnosis of patients that present with signs of intraocular infection, who are immunosuppressed [Nocardia endophthalmitis can occur in the immunocompetent but is less common [Endogenous ocular deposits of 50 years . It is wppressed . Nocardis common . Diagnoss common .In our immunosuppressed patient, her vital signs were normal for a long time in the face of severe underlying infection. Her choroidal abscesses were the first sign of her underlying problem, and so a particularly high index of suspicion is needed in immunosuppressed patients in view of the high mortality rate.Learning points in this case included that subretinal abscesses may be a harbinger of serious hitherto undiagnosed infection which portend a poor prognosis. Furthermore, it must be noted that vital signs in the immunocompromised may appear to be normal in the presence of serious infection.The authors declare that they have no competing interests.


Cognitive assessment is a cornerstone of geriatric care. Cognitive impairment has the potential to significantly impact multiple phases of a person’s cancer care experience. Accurately identifying this vulnerability is a challenge for many cancer care clinicians, thus the use of validated cognitive assessment tools are recommended. As international cancer guidelines for older adults recommend Geriatric Assessment (GA) which includes an evaluation of cognition, clinicians need to be familiar with the overall interpretation of the commonly used cognitive assessment tools. This rapid review investigated the cognitive assessment tools that were most frequently recommended by Geriatric Oncology guidelines: Blessed Orientation-Memory-Concentration test (BOMC), Clock Drawing Test (CDT), Mini-Cog, Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), and Short Portable Mental Status Questionnaire (SPMSQ). A detailed appraisal of the strengths and limitations of each tool was conducted, with a focus on practical aspects of implementing cognitive assessment tools into real-world clinical settings. Finally, recommendations on choosing an assessment tool and the additional considerations beyond screening are discussed. Cognitive impairment affects various aspects of care in older adults with cancer, such as the ability to participate in clinical decision-making, cope with treatment, and self-manage treatment regimens, as well as being associated with worse cancer and non-cancer outcomes ,2,3,4,5.At diagnosis, a patient is expected to participate in often complex decision-making that requires the ability to consider concepts which are multidimensional, as well as be able to weigh up potential trade-offs, such as quality of life and anticipated prognosis ,2,5. MorThe term cognitive impairment encompasses a variety of neurocognitive conditions, including dementia, delirium, and Cancer-Related Cognitive Decline (CRCD). Cognitive impairment disorders range from Mild Cognitive Impairment (MCI) to dementia. MCI is a modest cognitive decline in one or more cognitive domains in history and formal testing, without change in functional independence  . DementiCognitive assessment is typically incorporated into the broader Geriatric Assessment (GA) of the older person with cancer. The GA evaluates various domains  with a view to guide interventions to improve the care of and outcomes for older adults with cancer ,14. GA hThis rapid review seeks to evaluate cognitive assessment tools routinely used in older adults with cancer to provide clinical and practical information for cancer care clinicians. While the increased assessment of cognition in oncology is advocated, all cognitive assessment tools have inherent strengths and limitations. Awareness of these characteristics will aid the selection of a tool appropriate to the clinical setting and reduce the chances of misinterpretation of assessment results. This narrative literature review consists of two components: (1) Identification of the recommended cognitive assessment tools; and (2) focused review of the evidence underpinning the identified tools.A search was conducted to identify recent Oncology guidelines focused on geriatric assessment, both within the published literature and the web-based “grey literature”. Searches were limited to guidelines published in the last 5 years.PubMed and Ovid Medline were searched using the terms in To identify guidelines that may not be published in the peer-reviewed literature, a systematic search using predefined search terms was undertaken using the Google search engine to identify the most commonly viewed resources. The search strategy was refined after piloting to (cancer OR oncology) AND (geriatric OR elderly OR “older adult” OR “senior adult”) AND (guideline OR “position statement” OR “consensus statement” or recommendation). The first 100 websites featured in the results for the search were screened.Published between 1 July 2016 and 1 July 2021;Available in English;Guidelines, position statements, consensus statements or recommendations;Primary focus is the assessment of older adults with cancer;Authored or published by a national or international Medical or Oncological Society or Organization; andRefer to specific cognitive assessment tools.Opinion pieces, research articles, and review articles;Authored or published by a single institution;Related to a single cancer type or groups of cancers of a single body system or organ; andTools designed specifically for screening or assessing acute confusional states or delirium.Where there was uncertainty about whether an article/website met the inclusion/exclusion criteria, this was discussed by the research team, and a consensus decision was reached.Clinical practice guidelines: Evidence-based statements that include recommendations intended to optimize patient care and assist health care practitioners to make decisions on the appropriate health care for specific clinical circumstances .Cognitive assessment tool: Any instrument, tool or survey, developed or utilized to assess or screen cognitive function in adults.Any tools or instruments recommended for cognitive assessment or cognitive screening in these guidelines were identified. For this rapid review, the following operational definitions were adopted:Characteristics of interest for the cognitive assessment tools were determined by an iterative consensus process among the authors. A focused search using PubMed and Medline was conducted for each cognitive assessment tool identified in Part 1 to establish their characteristics . This waEight guidelines on the assessment of older adults with cancer  were ideThe Blessed Information Memory Concentration (BOMC) , also knThe Clock Draw Test (CDT)  is a welThe Mini-Cog incorporates the CDT and adds the three-item recall, thus adding a memory domain . MoreoveThe Mini-Mental Status Examination (MMSE) is a well-established test . It is wThe Montreal Cognitive Assessment (MoCA) is one of the longer assessment tools in the guidelines, taking approximately 10 minutes to complete . It coveThe Short Portable Mental Status Questionnaire (SPMSQ)  is a briIt can be challenging for cancer care clinicians to choose from the plethora of the available cognitive assessment tools. Of the six cognitive assessment tools that were recommended by geriatric oncology guidelines, the MOCA , MMSE 4, and MinAn initial consideration is whether a brief cognitive screen or a more detailed cognitive assessment is required and practical. The identified tools include brief screening tools  and short tools  that do not require specific training. In a busy oncology clinic, these may be most feasible. If a more detailed cognitive assessment is accessible through referral pathways, then a brief screen is likely to be adequate. However, in geriatric assessment clinics, clinicians may well prefer to utilize one of the longer recommended tools, the MoCA or MMSE, to evaluate a broader range of cognitive domains.The choice of cognitive assessment tool should be influenced by the demographics of the patient population, as patient factors must be considered when undertaking any cognitive assessment. Patients from culturally and linguistically diverse backgrounds require tools validated in these populations and languages. The MoCA, MMSE, and Mini-Cog have been translated and validated in many languages ,74,78. TPragmatic considerations will often determine the cognitive assessment tool chosen in a particular setting. An organization may have a preferred tool or may not have licensing for certain tools. In addition, clinicians may not have training for particular tools. For telephone consultations, the BOMC or SPMSQ can be used without adaptation, while the Mini-Cog or CDT cannot be utilized. If a tool has been utilized in an individual before, repeating the same tool allows for a longitudinal comparison. However, alternate versions should be used if the tool is repeated at time intervals below the recommended test-retest interval to counteract the practice effect ,104. TheA brief screening tool such as the Mini-Cog could be implemented into routine oncology clinic appointments for older people. Abnormal screening results could be followed by a more detailed assessment or on-referral. Based on our own practices, the authors recommend the Mini-Cog for brief screening and the MMSE or MOCA for more detailed testing where time permits. Moreover, this selection corresponds with the most endorsed tools by the guidelines. Where screening via phone is required, the BOMC could be used rather than the Mini-Cog and the telephone version of the MoCA could be used if more detailed testing is required. Clinicians who are assessing cognition in older adults frequently may wish to familiarize themselves with a small number of tools to provide a cognitive screening “tool-kit”, which allows the clinician to select a tool to suit the individual patient and the clinical setting.An abnormal result on cognitive screening requires further evaluation. Likewise, cognitive concerns in the context of a normal cognitive assessment tool result also warrant further assessment. To contextualize the abnormal cognitive screen, the clinician needs to obtain a broad understanding of a person’s level of function and the presence of longitudinal change in cognition ,6. A detThe assessment can be complemented by an occupational therapist review to assess function-based cognition . A physiDepending on the available services, referral for more comprehensive neurocognitive testing either in a designated memory care clinic or referral to a Geriatrician for a Comprehensive Geriatric Assessment (CGA), whereby other geriatric domains can be reviewed in detail, is recommended ,113. GerA limitation of this review pertains to the narrow focus on pre-existing cognitive impairment at cancer diagnosis. It is important to demarcate this from other cognitive conditions associated with cancer, which were outside the scope of this review. Literature on the entity of CRCD is expanding, referring to the deterioration in cognitive domains  during and following the treatment for cancer ,6. AgainThere is a high prevalence of cognitive impairment in older cancer survivors, thus while we have considered screening for cognitive impairment at an initial assessment, a longitudinal review is also important . This isThis study was a rapid review rather than a systematic review. We intended for our search to be broad and incorporate various international guidelines to make our study more generally applicable, but we acknowledge that our inclusion criteria required the availability of an English version of the guideline. Moreover, we note that our resulting guidelines originated in countries of similar global economic rankings and did not incorporate developing nations. Similarly, our practicalities and suggestions are more representative of the geriatric oncology practices described in the current geriatric oncology research , which tend to focus on developed countries without incorporating the unique challenges of developing nations.While we strongly advocate for routine cognitive screening, future research is needed to evaluate the optimal methods for routine cognitive screening and the associated interventions to support older adults with cancer and their caregivers. Moreover, it would be interesting to explore the varying models of care across geriatric oncology services and how cognitive assessment tools influence the service access and multidisciplinary team involvement in older adults with cancer with pre-existing cognitive impairment.Cognitive impairment significantly impacts older cancer patients and their caregivers. International guidelines and position statements for older adults with cancer recommend the routine use of cognitive assessment tools, including the BOMC, CDT, Mini-Cog, MMSE, MoCA, and SPMSQ, to detect cognitive problems. Tool selection is influenced by the clinical environment and patient factors. Clinicians should be familiar with utilizing various tools and their limitations. Every effort should be made to ensure older adults with cancer receive the appropriate cognitive work-up when screening is abnormal.


We systematically review 26 papers investigating subjective, behavioral, and psychophysiological correlates of subliminal exposure to phobic stimuli in phobic patients. Stimulations were found to elicit: (1) cardiac defense responses, (2) specific brain activations of both subcortical  and cortical structures, (3) skin conductance reactions, only when stimuli lasted >20 ms and were administered with intertrial interval >20 s. While not inducing the distress caused by current  exposure therapies, exposure to subliminal phobic stimuli still results in successful extinction of both psychophysiological and behavioral correlates: however, it hardly improves subjective fear. We integrate those results with recent bifactorial models of emotional regulation, proposing a new form of exposure therapy whose effectiveness and acceptability should be maximized by a preliminary subliminal stimulation. Systematic Review Registration: identifier [CRD42021129234]. Specific phobias are a prototypical example of emotional dysregulation, being characterized by marked and disproportionate fear for specific objects or situations . A minority of the included papers  are based on a reduced duration of stimulus exposure and/or on a manipulation of attentional focus Wiens, . BackwarThe feasibility of therapeutic approach based on subliminal stimulations was suggested in a seminal paper by Öhman and Soares  showing The aim of this paper is to systematically review the scientific literature concerning subliminal presentation of phobic stimuli to individuals affected by a specific phobia. Emphasis is given to the understanding of methodological variables that influence the acquisition and extinction of phobic reactions and their psychophysiological correlates, in order to provide methodological guidelines.We take into account the different correlates of subliminal phobic stimulation, the physiological , the behavioral , and the subjective  ones. We aim at disentangling correlates that can be considered as the expression of a defensive survival circuit from those that can be considered as the expression of a cognitive circuit accounting for the conscious feeling of fear. Using this approach, we reconsider what fear is, how it is (dys)regulated in specific phobias, and we propose a therapeutic model based on a combination of subliminal and supraliminal desensitization procedures.https://www.crd.york.ac.uk/prospero/).This systematic review has been created according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines  worksheet .The selected articles resulting from the PUBMED and SCOPUS search were merged into a non-redundant database. Duplicates were removed using Mendeley desktop reference manager  checked the pool of 13,174 abstracts collected from PUBMED and SCOPUS search engine outputs (excluding duplicates): any disagreement was discussed with DM as arbiter. Titles and abstracts were screened, and 13,045 studies were removed because they met one or more exclusion criteria for the systematic review . No exisBelow, findings from the retrieved articles will be considered in relation to the following themes: heterogeneity in experimental paradigms, physiological correlates to subliminal phobic stimulus and assessment of subjective  fear caused by subliminal phobic stimulus presentation.Several procedures allowed subliminal presentation of a phobic stimulus see . Using bBesides backward masking, other approaches have been retrieved for making a phobic stimulus subliminal. Carretié et al.  made stiFinally, a recent paper by Taschereau-Dumouchel et al.  deservesOther paradigms that modulate awareness of phobic stimulus were excluded from this review because they did not satisfy the inclusion criteria requiring complete unawareness of the stimulus.All studies considered in this review used questionnaires measuring subjective fear for a specific animal, in order to assess phobia severity see . The majConcerning the effect of subliminal stimulation on subjective fear, some studies used self-report measures, including the Subjective Units of Distress Scale (SUDs), the Behavioral Avoidance Test (BAT), the Disgust Scale – Revised  was reported , produced a reduction in disgust levels (as assessed through DS-R) but not in fear levels (as assessed through BAT and SUDs).Gutner et al.  reportedGranado et al.  reportedA few studies have examined the association between self-report and objective measures in phobic participants exposed to subliminal phobic stimuli. Siegel et al. measured the effect of subliminal exposure on subjective fear of phobic subjects after previous supraliminal exposure , electroencephalography (EEG) or positron emission tomography (PET). PET scans during subliminal stimulation showed undifferentiated left amygdala responses for both phobic and fear-relevant (but non-phobic) stimuli; during supraliminal stimulation, both right and left amygdala were activated by phobic stimuli  but not by fear-relevant stimuli awareness is necessary.All studies had to cope with the issue of assessing awareness for masked stimuli Wiens, . The retPsychophysiological reactions to threat have been widely studied in healthy subjects by means of overt stimulation paradigms and they typically relate to sympathetic activation as observable on skin conductance, heart rate and startle responses. Similar responses are reliably enhanced in phobic subjects exposed to overt phobic stimuli  while seven studies reported negative results . On balaThe relationship shown in Other methodological differences that could account for contrasting results were considered , but no effect emerged. For example, task schedule  is known to affect timing and efficacy of conditioning and extinction procedures, and could eventually affect the results listed in Psychophysiological research has long recognized that specific cardiac defense reactions occur in the presence of potential injury or death  reported significant symptom reduction and showed reduced brain activations to supraliminal but not to subliminal phobic stimuli  is not uncommon  subliminal exposure; (2) single-stimulus supraliminal exposure  subjectively reported by patients could affect onset and maintenance of phobic fear, it could be used also to reduce it in protocols involving a subliminal exposure. To this regard, in the Conclusion section we propose a model for addressing different correlates of fear elicited by subliminal exposure to phobic stimuli and for quantifying their contribution to the final subjective level of the consciously experienced fear.Based on papers examined in the review, we propose the following theoretical agreements and methodological standards for designing experimental protocols that involve subliminal phobic stimuli:the concept of phobic reaction must not be overlapped to the concept of subjective fear LeDoux, . Overlapconsider that awareness threshold varies as a function of the salience that each stimulus has for each subject  must consider effects of methodological parameters on the psychophysiological correlates . We found that a stimulus duration smaller than 20 ms and an intertrial stimulus interval smaller than 20 s can hardly lead to significant skin conductance responses, probably due to the physiological features of such correlate. Finally, also the number of trials should be considered when designing the experimental protocol as suggested by results concerning habituation effect  seems to be affected by subliminal exposure only when its assessment follows also a conscious exposition to phobic stimulus . As a first step, a subliminal exposure reduces physiological and behavioral responses to unconsciously perceived phobic stimuli: at this stage, it represents a latent desensitization. As a second step, patients are guided to become aware of the reduced physiological feedbacks when facing an overt phobic stimulus, this allowing a cognitive remodeling that will result in an enhanced reduction of fear. Such a two-step protocol will likely benefit from the strengths of both subliminal (tB) and supraliminal (tA) exposure, hopefully resulting in a more acceptable and effective treatment.The present systematic review adheres to standardized protocols for selecting and evaluating papers to include, as reported in Methods section and meticulously detailed in The strict inclusion criteria adopted resulted in the exclusion of a huge number of papers that didn't clearly measure the effectiveness of subliminal paradigm used to administer the phobic stimuli. This was made necessary by the lax interpretation that scientific literature used to give to the concept of subliminal stimulation, that led to methodological and terminological confusion Wiens,  and mislAll these limitations considered, the conclusions drawn by the present systematic review need to be confirmed by further studies. In particular, the integrated model proposed should rely on direct empirical demonstration that will hopefully be provided in future experiments.The aim of this review was to address scientific literature studying subjective, behavioral and psychophysiological correlates of subliminal phobic stimuli, and the consequent theoretical and therapeutic implications. Overall, the papers considered in this review—after being systematized and analyzed—provide new elements to develop a better theory of what specific phobias are, why they arise, how they maintain, and which are the best therapies to treat them. Subliminal exposure seems to represent a promising tool for the treatment of specific phobias, even if it shows some limits. From a methodological point of view, analysis of experimental procedures allowed us to find some relevant methodological parameters contributing to explain the contrasting results reported in the literature concerning skin conductance responses as reliable reactions elicited by subliminal phobic stimuli: only studies using intertrial interval (ITI) greater than to 20 s and stimulus duration > 20 ms successfully yielded skin conductance reactions to subliminal phobic stimuli .Integrating the main evidence coming from the studies included in this review, we can draw a partially unexpected pattern of reactions induced by subliminal phobic stimuli. A phobic stimulus administered in subliminal paradigms is processed way more deeply than expected. In <33 ms , a phobic subject distinguishes a phobic stimulus from a stimulus sharing similar perceptual features (e.g., a spider from a crab, in Sebastiani et al., Psychophysiological correlates and behavioral measures can be modulated by the subliminal exposure, but this is not reflected in a reduction of subjective distress when consciously facing the phobic stimulus see . This diImprovements in facing a consciously perceived phobic stimulus—when assessed—suggest a more complex truth, as we show in the integrated defensive-cognitive therapeutic model proposed in section Toward an Integrated Defensive-Cognitive Therapeutic Model: subliminal and supraliminal exposure to phobic stimuli seems to affect two distinct systems , both ofThe original contributions presented in the study are included in the article/SF and DM participated in all phases of the work. PH contributed in writing and reviewing the work. AZ contributed in reviewing the work. AG contributed in conceiving and reviewing the work. All authors contributed to the article and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Chemoprevention strategies reduce malaria disease and death, but the efficacy of anti-malarial drugs used for chemoprevention is perennially threatened by drug resistance. This review examines the current impact of chemoprevention on the emergence and spread of drug resistant malaria, and the impact of drug resistance on the efficacy of each of the chemoprevention strategies currently recommended by the World Health Organization, namely, intermittent preventive treatment in pregnancy (IPTp); intermittent preventive treatment in infants (IPTi); seasonal malaria chemoprevention (SMC); and mass drug administration (MDA) for the reduction of disease burden in emergency situations. While the use of drugs to prevent malaria often results in increased prevalence of genetic mutations associated with resistance, malaria chemoprevention interventions do not inevitably lead to meaningful increases in resistance, and even high rates of resistance do not necessarily impair chemoprevention efficacy. At the same time, it can reasonably be anticipated that, over time, as drugs are widely used, resistance will generally increase and efficacy will eventually be lost. Decisions about whether, where and when chemoprevention strategies should be deployed or changed will continue to need to be made on the basis of imperfect evidence, but practical considerations such as prevalence patterns of resistance markers can help guide policy recommendations. After decades of dramatic reductions in malaria cases and deaths worldwide, progress toward malaria control and elimination had plateaued before the COVID-19 pandemic . FurtherThe chemoprevention strategies currently recommended by the World Health Organization (WHO) include intermittent preventive treatment in pregnancy (IPTp), intermittent preventive treatment in infants (IPTi), seasonal malaria chemoprevention (SMC), and mass drug administration (MDA) for the reduction of disease burden in emergency situations Table . From thAs they have been developed and implemented, each chemoprevention strategy has been evaluated in complex prospective, controlled trials that typically randomly assign either individuals or clusters  to receive either the drug prevention regimen being tested, or an alternative regimen, or no preventive regimen. Because their primary outcome measures are affected by a number of host and parasite factors in addition to parasite resistance, efficacy trials do not directly measure drug resistance per se, but these prospective studies remain the gold standard for measuring the chemoprevention efficacy.The efficacy of drugs used to treat malaria is monitored worldwide in single-arm clinical trials known as WHO Therapeutic Efficacy Studies (TES), which follow standardized protocols to provide direct evidence of drug efficacy to guide policy decisions . Unlike Because anti-malarial drug resistance is considered paramount among the many host, parasite, pharmacological and other factors that affect the efficacy of anti-malarial drugs, methods for detecting the presence of resistant parasites have long been employed as a surrogate for efficacy trials.In vitro assays for measuring drug resistance provide a direct measure of parasite response to drugs , but havPlasmodium falciparum resistance to the antifolates made it possible to define the determinants of in vivo resistance to these drugs, and to develop simple assays for molecular markers of antifolate resistance that can potentially serve as surrogate indicators of drug efficacy. Pyrimethamine and other antifolates such as proguanil (via its metabolite cycloguanil) and trimethoprim target P. falciparum dihydrofolate reductase (DHFR), while sulfadoxine and other sulfas target dihydropteroate synthase (DHPS). Resistance to DHFR inhibitors and sulfa drugs in vitro is conferred by single nucleotide polymorphisms (SNPs) in P. falciparum DHFR and DHPS, respectively  up to XX% but not in a setting with a [resistance marker] of YY%. The relationship between efficacy and mutation frequencies between XX% and YY% remains unknown. Resistance may not have been the only factor influencing efficacy in these settings.”When selecting thresholds for recommending where and when chemoprevention strategies should be used, practical factors unrelated to evidence about resistance and efficacy should also be considered, such as whether or not current or future treatment drugs share resistance mechanisms with chemoprevention drugs, or whether a given threshold might result in confusing situations such as different recommendations in adjacent areas with similar malaria epidemiologies that happen to have resistance prevalences just above and below the threshold.These limitations can be mitigated to some extent by standardizing study designs and coordinating multi-centre trials and pooled analyses, as has been done by consortia that have formed to test and implement some chemoprevention strategies. The WHO recommendations on research priorities can also guide researchers to conduct studies that will yield data useful to policy makers, to the extent that researchers are made aware of and follow such recommendations. For example, a standardized protocol for “Preventive Efficacy Studies (PES)” akin to TES studies is currently being developed by the WHO Global Malaria Programme.It is somewhat encouraging that malaria chemoprevention does not inevitably lead to meaningful increases in resistance, and even high rates of resistance do not necessarily impair chemoprevention efficacy. At the same time, it can reasonably be anticipated that, over time, as drugs are widely used, resistance will generally increase, and sooner or later efficacy will be lost. Decisions about whether, where and when chemoprevention strategies should be deployed will continue to need to be made on the basis of imperfect evidence. It is hoped that this assessment of what is known about the relationships between resistance and chemoprevention will be useful as the WHO evaluates and updates its chemoprevention recommendations.


Malignant pleural mesothelioma (MPM) is a highly aggressive pleural tumour which has been epidemiologically linked to occupational exposure to asbestos. MPM is often associated with pleural effusion, which is a common cause of morbidity and whose management remains a clinical challenge. In this review, we analysed the literature regarding the diagnosis and therapeutic options of pleural effusion secondary to mesothelioma. Our aim was to provide a comprehensive view on this subject, and a new algorithm was proposed as a practical aid to clinicians dealing with patients suffering from pleural effusion. Malignant pleural mesothelioma (MPM) is a highly aggressive tumour of the pleura, which has been epidemiologically linked to occupational exposure to asbestos , whose iPleural effusion remains a common clinical condition, affecting more than 1.5 million patients per year in the USA alone . In geneIn this review, we will focus on malignant pleural effusion secondary to pleural mesothelioma: we analysed the literature on the diagnosis and therapeutic options of pleural effusion secondary to MPM. Our aim was to provide a comprehensive view on this interesting topic; then, we try to draw a new and comprehensive algorithm for the diagnosis and management of these patients.We searched PUBMED using the following search string: (“Mesothelioma” [Mesh: NoExp]) AND .Articles in languages other than English and case reports were excluded. All articles retrieved were then selected by two authors  based on title and abstract; the final selection was carried out after reading the full text.Pleural effusion has a wide variety of aetiologies, which can be classified according to the nature of the pleural fluid: transudative  or exudative . Pleural fluid is classified as transudate or exudate based on the Light’s criteria. Pleural effusion can be further categorized as benign or malignant. Malignant pleural effusion is the second most common cause of exudative pleural effusion after parapneumonic effusion . It accoPleural effusion usually occurs early in the mesothelioma course, and it is, therefore, responsible for the presenting symptoms. The most common symptoms are a progressively worsening dyspnoea, weight loss, fatigue, chest pain and discomfort, and cough. The severity of the dyspnoea is associated both with the amount of pleural fluid and with the rate of fluid accumulation, but it is also affected by underlying cardiologic and respiratory comorbidities.Imaging has a relevant role in determining MPM as the cause of pleural effusion, mainly because it allows for the detection of those coexisting findings which are suggestive for malignancy. Pleural effusion is often demonstrated for the first time by performing a chest X-ray: a 200 mL pleural effusion can be detected on chest X-ray in the posterior-anterior view. A massive pleural effusion is frequently related to malignancy. In case of effusion with no history of cardiopathy and a normal heart size on chest X-ray, cancer should be considered as a likely diagnosis, even though systemic lupus and pleural effusion due to liver failure can have a similar clinical presentation. Except for direct invasion by lung or breast cancer, which are frequently associated with ipsilateral pleural effusion, bilateral effusion is more common in case of other metastatic primary tumours . In maliThe analysis of pleural fluid may provide data suggesting the diagnosis of mesothelioma, but has a quite poor sensitivity . Cytology remains, however, the least invasive and most used first-line diagnostic test in case of pleural effusion and suspected malignancy. The diagnostic accuracy of cytological analysis is increased in case of visceral pleural invasion in epithelioid mesothelioma. Immunocytochemical analysis, which can be performed on cell-block sections when a large amount of pleural fluid is sent for evaluation, is often required in order to obtain a diagnosis . It has A valid alternative that makes it possible to biopsy pleural irregularities under direct vision is pleuroscopy, also known as medical thoracoscopy: it can be performed with local anaesthesia and under mild sedation and has a low rate of complications. However, minimally invasive surgery, such as video-assisted thoracic surgery (VATS) and thoracoscopy, is the preferred approach in most centres, and particularly by thoracic surgical centres. In fact, this technique it enables to perform multiple biopsies, to better assess the involvement of the different pleural surfaces  and of the mediastinal region, and to perform therapeutic procedures  during the same operation. It is recommended to perform multiple and deep biopsies of both pleural abnormalities and macroscopically normal tissue, in order to reduce the risk of false negatives and obtain samples of fat and muscle tissue ,16. The An interesting issue is the high potential of patient-derived xenografts (PDXs) in testing new therapies against MPM, as reported by Affatato et al. .Management of recurrent pleural effusion in malignant pleural mesothelioma still remains a challenge for clinicians, especially when patients suffer from progressive breathlessness and impaired quality of life. The best clinical approach should take into account the extension of the disease, the performance status and the expected survival of the patient, and it should aim to relieve symptoms, reduce hospitalization and improve quality of life with minimally invasive procedures.Various medical and surgical procedures are available to reduce pleural fluid recurrence and to relieve symptoms: in particular, these include both mechanical and chemical pleurodesis with sclerosing agents, indwelling pleural catheter placement (IPC). If the patient can tolerate a surgical procedure, pleural biopsies and chemical or mechanical pleurodesis may be performed during the same thoracoscopic intervention, after a frozen section diagnosis or confirmation of pleural malignancy.Chemical pleurodesis is a procedure intended to create a symphysis between the parietal and visceral pleura by intrapleural administration of various chemical agents, such as talc, doxycycline, tetracycline and bleomycin, with a consequent inflammatory response between visceral and parietal pleura that leads to the obliteration of pleural space and prevents effusion recurrence. Among various available sclerosing materials, sterile talc is the most common and the most successful chemical agent for performing pleurodesis. It can be applied under direct vision during thoracoscopy or may be instilled through the pleural drainage ; while the former technique can be used only during a surgical procedure, the latter can be administered in suspension form at the bedside through the chest tube and can be also used in patients who are unfit for surgery. In the case of talc slurry, recent studies suggest that higher pleurodesis success rates may be obtained using large (24 Ch) compared to small-calibre chest tubes . VATS plFysh et al. published a retrospective analysis of 390 patients comparing the success rate of surgical and bedside chemical pleurodesis in MPM pleural effusion, reporting no significant differences in efficacy, patient survival, and total time spent in hospital after the procedure, even though patients who underwent surgical pleurodesis were significantly younger than the bedside group . PleurodOther described sclerosing agents are some antibiotics such as bleomycin, tetracycline and doxycycline, and Corynebacterium parvum, an inactivated anaerobic gram-positive bacterium associated with an intense immunostimulation.Mechanical pleurodesis is a surgical procedure aimed at obtaining pleural symphysis by creating abrasions on the parietal pleura and causing an inflammatory process and a scar between parietal and visceral pleura. It is less used than chemical pleurodesis for recurrent malignant pleural effusion.General contraindications to pleurodesis are conditions in which there is not enough contact between the visceral and parietal pleura, and therefore pleural space cannot be obliterated: in MPM this condition is commonly found in case of non-expandable lung. In these cases, the visceral pleural disease associated with recurrent effusion traps the lung, thus preventing its complete expansion after fluid removal.Non-expandable lung is common in MPM: a prospective observational cohort study by Bibby et al. including 192 MPM patients with pleural effusion described 64 cases of non-expandable lung (33.3%), associated with significant symptomatology, shorter survival, and a hazard ratio for mortality of 1.80, compared with MPM patients without trapped lung .In these clinical conditions, in which both chemical and mechanical pleurodesis are ineffective, an alternative treatment option can be represented by indwelling pleural catheter placement. Indwelling pleural catheters are small silicone flexible tubes with calibres around 15 Fr, in which the distal part  is inserted in the pleural space, while the medial portion is designed to be located in a subcutaneous tissue tunnel and to create a fibrous reaction that allows the long-term maintenance of the device; the proximal end is connected to a one-way valve through which the patient can periodically (in most cases daily) drain the pleural fluid without any medical supervision. Indications for IPC placement are recurrent malignant pleural effusions in which pleurodesis procedures have been ineffective, and cases on non-expandable lung; IPC should also be considered as a palliative solution when recurrent effusion causes a serious deterioration of clinical conditions and quality of life. IPC also can be placed under local anaesthesia at the bedside or in an outpatient setting: the main advantages are the easy management of the device in out-of-hospital scenarios too, the reduction of hospital stays and readmissions, and the significative improvement in symptoms and patients’ quality of life . GeneralVATS partial pleurectomy (VAT-PP), a surgical manoeuvre of debulking performing parietal pleurectomy with or without decortication can be proposed in selected cases, but some evidence show that VAT-PP does not improve overall survival if compared with talc pleurodesis. In particular, a multicentre RCT comparing VAT-PP and talc pleurodesis in patients with MPE due to MPM reported higher complication rates  and a longer hospital stay in patients treated with VAT-PP, with no survival advantage in this group of patients. However, VAT-PP surviving patients at 6 and 12 months showed a better EQ-5D-assessed quality of life score, suggesting that this option might have a role in patients with at least 6 months life expectancy .Recently, new medical therapeutic options are being proposed not only for palliation of MPE, but also to treat the underlying causes of effusion recurrence: in particular VEGF has been recognized as an important factor promoting cancer and mesothelial cells production of secretions and playing a relevant role in the process of MPE formation. In this setting, Chan et al. proposed a novel therapeutic option combining systemic chemotherapy (pemetrexed and cisplatin) with intrapleural injection of pemetrexed and bevacizumab (anti-VEGF antibody). In the 23 patients enrolled, the combined systemic and local chemotherapy effectively reduced effusion, thus relieving symptoms and improving quality of life . Few advPleural effusion in MPM often represents the first clinical presentation of the disease, is associated with symptoms such as dyspnoea, progressive breathlessness, worsening of general conditions and quality of life, and still remains a clinical challenge in terms of both therapeutic approach and long-term management. An algorithm for the management of pleural effusion in MPM is depicted in Various conditions should be taken into account in order to offer the most effective and patient-centred therapeutic option: several surgical procedures may be performed to reduce effusion recurrence and relieve symptoms; thoracentesis and chest drainage are the first-line diagnostic and therapeutic options recommended by international guidelines, but it should be considered that cytologic evaluation alone has a poor diagnostic value especially for MPM .In case of recurrence, a definitive pleural intervention is advised: among the above mentioned procedures, talc pleurodesis is the standard treatment if patient’s life expectancy is higher than 3 months : talc caRegarding quality of life, data between the selected studies cannot be compared: nevertheless, two studies reported no significant differences and one reported better quality of life scores in the pleurodesis group, underlying how the question is still under debate and how many factors can affect this hardly measurable endpoint.Recurrent pleural effusion in malignant pleural mesothelioma is a clinical challenge in terms of diagnostic approach and long-term management: even though international guidelines have an essential role in clinical decision-making, the best therapeutic option should be patient-tailored, considering also quality of life and time spent in hospitals, given the poor prognosis and life expectancy of these patients, who are often severely symptomatic. In this scenario, we proposed our point of view and our diagnostic-therapeutic approach to MPE in MPM, which can be a helpful practical tool for clinicians dealing with this type of patients. Further research is needed to completely understand MPE pathogenesis, to apply in everyday clinical practice new promising diagnostic and prognostic biomarkers and to provide the best therapeutic or palliative surgical and medical options for each patient.


With the advent of stem cell therapy for spinal cord injuries, stroke, burns, macular degeneration, heart diseases, diabetes, rheumatoid arthritis and osteoarthritis; the need to track the survival, migration pathways, spatial destination and differentiation of transplanted stem cells in a clinical setting has gained increased relevance. Indeed, getting regulatory approval to use these therapies in the clinic depends on biodistribution studies. Although optoacoustic imaging (OAI) or photoacoustic imaging can detect functional information of cell activities in real-time, the selection and application of suitable contrast agents is essential to achieve optimal sensitivity and contrast for sensing at clinically relevant depths and can even provide information about molecular activity. This review explores OAI methodologies in conjunction with the specific application of exogenous contrast agents in comparison to other imaging modalities and describes the properties of exogenous contrast agents for quantitative and qualitative monitoring of stem cells. Specific characteristics such as biocompatibility, the absorption coefficient, and surface functionalization are compared and how the labelling efficiency translates to both short and long-term visualization of mesenchymal stem cells is explored. An overview of novel properties of recently developed optoacoustic contrast agents and their capability to detect disease and recovery progression in clinical settings is provided which includes newly developed exogenous contrast agents to monitor stem cells in real-time for multimodal sensing. Stem cell therapies have shown immense potential for treating various degenerative diseases in pre-clinical settings and clinical trials. However, for the successful quantitative and qualitative monitoring of stem cells and the understanding of their regenerative mechanisms and pathways, stem cell labelling and tracking are crucial. Differentiating cells of interest from the host cells using contrast agents and visualising the in vivo distribution and migration to the targeted site using suitable imaging modalities is of utmost importance from a therapeutic point of view. Determining the location and quantity of the cells, monitoring the delivery of cells to the target tissues and their long-term fate and biodistribution is possible with available imaging modalities , 2.The advantages and limitations of currently available imaging modalities for stem cell tracking applications has been extensively reviewed –5. AmongPhotoacoustic imaging (PAI) or optoacoustic imaging (OAI) has been gaining popularity since 1990 with the increase in their significance to different biomedical imaging applications. With the advent of stem cell therapy, the interest in stem cell labelling seemed to increase in parallel with OAI, although the trend shows a dip around 2012 , often referred to as photoacoustic imaging is based on the photoacoustic effect, which is the conversion of pulsed light into ultrasound waves in optically absorbing samples. OAI is carried out by illuminating a sample with an intense nanosecond pulsed laser source. This causes the photons to propagate and diffuse through the tissue. Optically absorbing molecules absorb some of this light, which is then partially converted to heat. This results in a rapid thermoexpansion and contraction in the tissue, which generates a pressure wave. An ultrasonic transducer detects this pressure wave, and subsequent digital processing converts the ultrasonic signal into images revealing molecular and structural properties of the sample. OAI utilises either an ultrasound detector array or a single scanned detector and an inverse algorithm to reconstruct cross-sectional or three-dimensional images of the sample, which can be a biological specimen or even human tissue. The acoustic pressure waves are proportional to the absorption coefficient of the medium being irradiated mentclass2pt{minimExogenous contrast agents are utilised to improve the contrast between the region of interest and background, to detect structures that are otherwise difficult to target and to reach tissues at a greater depth. They aid in gathering information regarding a disease state, detection of biomarkers or biochemical and cellular processes with high sensitivity, specificity and signal-to-noise ratio (SNR). There is some flexibility when it comes to developing a contrast agent for OAI, as any molecule that absorbs light, efficiently transferring the energy to the surrounding tissue, causing a thermoelastic expansion in order to generate a pressure wave is a candidate . IdeallyStem cells cannot be visualised directly by OAI as they do not have an adequate optical absorption coefficient; they must be labelled with efficient contrast agents. Before monitoring stem cells in a clinical setting, it is essential to optimize the labelling efficiency and investigate the cytotoxicity of contrast agents as they are highly dependent on the contrast agent composition, shape, size, concentration, and surface functional groups. Moreover, these factors indirectly affect the viability, differentiation, distribution, migration and engraftment of stem cells.Adult stem cells such as mesenchymal stem cells (MSCs) are important because of their capability to maintain and repair their tissue of origin. MSCs can differentiate into tissue- specific cell types while maintaining their capacity for self-renewal, migrate to injured tissues naturally to promote vascularization  and immuStudies have reported that less than 10% of administered stem cells have been successfully engrafted in target tissues, while the remainder were either trapped in reticulo-endothelial organs or underwent apoptosis shortly after implantation , 30. SinClinical translation from a pre-clinical setting for stem cell tracking applications critically requires monitoring of the spatial destination, the migration pathway and final distribution of the transplanted stem cells using non-invasive, longitudinal, and repetitive imaging. Engineering a contrast agent with desirable characteristics for stem cell tracking can monitor if the stem cells have reached the target tissue and survived after transplantation for efficient therapeutic activity. Table For any biomedical and clinical studies that rely on stem cell tracking, it is crucial to design and develop exogenous contrast agents that can be produced reproducibly in large volumes. To ensure a prolonged half-life for in vivo longitudinal tracking in therapeutic studies, these contrast agents must be colloidally stable. Moreover, they must be biocompatible to avoid adverse immune responses and negative reactions in the vascular system, kidneys and blood-brain barrier. They should be designed with a surface that can be efficiently modified to bind to molecular probes like antibodies or peptides to be able to target specific receptors in cells and tissues of interest. For efficient optoacoustic tracking of stem cells, the exogenous contrast agents should be optimized to have a high light to acoustic signal conversion efficiency in the NIR region. Specifically, for stem cells, it is vital to ensure that the contrast agent does not affect the rate of proliferation and the differentiation potential of the cell. The surface charge of the contrast agent could also be perfected to facilitate higher cellular uptake, which directly translates to a higher contrast-to-noise ratio for effective imaging.Biocompatibility defines a substance that does not disturb the biochemical process in living cells or organisms with no or minimal toxicity. Moreover, such substances should elicit no or minimal immunological response or minimal physiological reaction. A material is colloidally stable when it is resistant to changes in the chemical, physical or biochemical environment and does not physically disintegrate upon introduction of external stimuli. Upon cellular uptake of exogenous contrast agents after incubation in a biological medium, aggregation and agglomeration of contrast agents are induced because of their interaction with proteins. Biocompatibility and colloidal stability of the contrast agent can be improved by integrating or coating them with materials that make the surface of the contrast agent more neutral or hydrophilic.For optoacoustic contrast agents, the chemical structure of NIR dyes can be optimised for colloidal stability by introducing hydrophilic groups, triplet state quenchers and stabilising groups. Indocyanine Green (ICG) is a tricarbocyanine dye that has a 10% fluorescence quantum yield in water, thus able to release 90% of its excited non-radiative energy in the form of thermoelastic expansion, an advantage for optoacoustic imaging. Filippi et al. studied FDA approved ICG contrast agents to track MSC in vivo due to its excellent absorption properties and biocompatibility . The stu of MSCs . The staFor any type of biomedical application such as stem cell tracking, biocompatibility and colloidal stability of contrast agents are critical. Already available FDA-approved dyes like ICG which have a consistent intracellular uptake have been utilised for stem cell labelling and tracking. Coating nanoparticles with polymers can increase their colloidal stability for long periods of time at high ionic concentrations.OAI is a non-invasive and non-ionising biomedical imaging modality which is used for tracking stem cells, and it does not affect the proliferation and function of stem cells. On the other hand, contrast agents could have detrimental effects on functioning and differentiation potential of stem cells depending upon its chemical composition. Therefore, it is crucial to design OAI contrast agents which are biocompatible and non-toxic, and which do not have any undesirable effects on the proliferation, function, and safety of the labelled stem cells. Characterisation of contrast agent is critical to estimate the level of aggregation, change in surface charge and adsorption of proteins to the nanoparticle before and after interaction with biological media. Additionally, utmost care is taken to monitor the viability, toxicity and genetic stability of labelled cells in vitro before using these molecular probes for pre-clinical studies. For clinical applications, toxicology testing of the contrast agents on their own and in stem cells should be carried out under GLP conditions and in vivo (using mouse models) to assess any tumorigenic, hepatotoxic or neurotoxic potential . The safThe physicochemical properties such as the size, morphology and surface charge of contrast agents directly influence their cellular uptake mechanism and intracellular trafficking . High thSilica coating is an alternative approach in enhancing the cellular uptake of contrast agents like gold nanoparticles. Not only is silica biocompatible, but it also has added benefits of preventing the aggregation of particles in cells. Jokerst et al. reported real-time and non-invasive imaging of a guided stem cell therapy for muscular dystrophy using silica-coated gold nanorods (SiGNRs) . It was Nanoparticles can be optimised with labelling enhancers like CPPs and surface coatings to promote cellular uptake and retention. To image stem cells with high sensitivity and contrast, there is a need to label MSCs with an optimal concentration of the contrast agent without affecting the cell’s normal function.Long-term longitudinal monitoring of stem cells in vivo is imperative to understand the regenerative pathway of stem cells. Longitudinal studies can be particularly useful for evaluating the development of a regenerative disease, biodistribution of stem cells after transplantation and the outcomes of treatments over time. Unlike photon-emitting contrast agents, optoacoustic contrast agents can be optimised for long-term longitudinal monitoring of stem cells, as their signal does not depend on radioactive decay. Easy renal clearance is possible with nanoparticles smaller than 5.5 nm but that limits their long-term longitudinal capabilities .Modifying the surfaces of inorganic nanoparticles can increase their circulation time in blood and increase their water solubility. Citrate-coated Prussian blue particles (PBPs) were used by Li to monitor traumatic brain injury (TBI) and track the progress of disease recovery . The reaRapid clearance of contrast agents from the cell prohibits long-term monitoring and longitudinal studies of stem cells. Developing contrast agents with physicochemical characteristics that enable them to be retained in the cells and delivering labelled stem cells using 3D model systems can facilitate stem cell tracking for longer periods of time. Depending on the retention capability and colloidal stability of the contrast agents used for stem cell labelling, OAI can efficiently track the stem cells in real-time at the time of delivery and can provide longitudinal monitoring after transplantation as long as the signal from the contrast agent is above the detection threshold. In pre-clinical studies, researchers have reported two weeks of longitudinal monitoring of stem cells using nanoparticles as contrast agents , 40, 44.The development of exogenous contrast agents that provide high imaging contrast is vital to ensure that the signal does not attenuate drastically during imaging process due to background noise and clutter signals as a result of light scattering from tissues. Labelling cells with higher concentrations of contrast agents will enhance the signal to noise ratio but result in cytotoxicity.Contrast agents with optical absorption in the near-infrared (NIR) wavelengths, where tissue absorption is minimal can be utilised for OAI. With less autofluorescence at NIR compared to visible wavelengths, NIR dyes can be used as optoacoustic contrast agents. For example, 1,1’-dioctadecyl-3,3,3’,3’tetramethylindotricarbo-cyanine-iodide (DiR) was used to label bone-marrow- derived MSCs by Berninger et al. for cell-based cardiac regenerative therapy tracking using MSOT . Due to  surface . The resVarying the aspect ratio or changing the dimensions can help tune the relative scattering to absorption contribution of nanoparticles. Stem cell delivery to a trabecular meshwork (TM), a fluid drainage tissue in the anterior eye was studied using gold nanosphere (AuNS) labelled MSCs by Kubelick et al. . ReducedWhen anisotropy is introduced to nanoparticles, the SPR peak can be strongly enhanced and tuned as a function of aspect ratio. Anisotropic nanoparticles, due to their versatile geometries have large extinction cross-sections. This ensures that high optical absorption in the NIR region where deep-tissue imaging with a high signal-to-noise ratio (SNR) is possible. Quantitative tracking of human MSCs labelled with Gold Nanocages (AuNCs) used the strong optical absorption and two- and three-photon luminescence properties of AuNCs . The holPhoton absorption and scattering in biological tissue is characterized by many factors such as cell size, water content, electrolyte concentration and blood oxygenation. Absorption and scattering also depends on the wavelength range and is minimal around 1300 nm and 1700 nm .The laset 800 nm . Dual plt 800 nm . For lont 800 nm . Since wDesigning exogenous contrast agents in the NIR-II window include challenges such as favourable clearance profiles, biocompatibility and photothermal conversion efficiency of NIR-II contrast agents similar to clinically approved NIR-I contrast agents. NIR-II contrast agents tend to have complex geometrical structures leading to production issues such as reproducibility and homogeneity. Organic semiconducting polymer nanoparticle probes  upon cell death could act as stimuli for detection.Viability of stem cells was monitored by Yoo et al. using ICG due to its’ relatively high optical absorption at 800 nm (NIR) and its ability to clear out of stem cells after cellular death through diffusion . ContinuFalse positive signals can originate from the contrast agent either trapped in dead cells or engulfed by macrophages could yield incorrect results during in vivo stem cell tracking. Dyes like ICG diffuses out if the labelled cell undergoes apoptosis. Contrast agents that can detect ROS generation or a change in pH can be engineered for real-time in vivo monitoring of stem cell viability.As combining imaging modalities is advantageous in extracting detailed morphological and molecular information, a huge array of complex multimodal exogenous contrast agents is being developed. This exercise will reduce the potential drawbacks of using each imaging modality alone and modality-specific strengths can be integrated to form a more complete picture of each transplantation. While selecting imaging modalities for stem cell tracking, it is important that the multimodal imaging contributes to relevant and specific information during stem cell transplantation such as stem cell localisation, viability, quantification, and functionality. Although multimodal imaging systems can yield more information per sample or subject, it is important to consider the number of imaging sessions required, imaging time, cost and repeated or frequent anaesthetic use in pre-clinical imaging studies. Moreover, false positive or false negative results could be cross-checked using multimodal imaging. Imaging techniques utilizing multimodal contrast agents can provide more insight as they can easily compensate for limitations from a single imaging modality.Nanoparticles are ideal as multimodal contrast agents as they have large surface areas that can be easily functionalised with different components to support multimodal imaging. Different molecular components can also be encapsulated or embedded into single nanoparticles. The molecular constituents can be attached to the carrier nanoparticle by electrostatic forces, covalent or conjugated bonding, and can allow the incorporation of chemicals into the nanoparticle core. Magnetic resonance imaging (MRI) is a well-established imaging modality for stem-cell tracking as it provides detailed morphological and functional information and allows high resolution and accurate localization of cells. MRI contrast agents can be classified based on their chemical composition, magnetic properties, the presence or absence of metal atoms, effects on MR images and their biodistribution. However, not all patients can be imaged using this expensive and complex procedure. Also, MRI’s limited sensitivity and inability to quantify the cell population can be compensated using OAI. Human MSCs labelled with multifunctional nanoparticles containing superparamagnetic iron oxide with a gold coating (SPIO@Au), which have a maximum absorbance at 810 nm, were used by Qiao et al. for imaging brain tumours Fig. a–f 67]..67]. Theherapies . Their uUltrasound imaging (USI) and OAI can be combined to provide guidance for accurate stem cell transplantation. Exact co-registration of USI and OA images can be attained by using the same transducers for detection. The limited contrast and 3D capabilities of USI can be compensated with OAI. USI in turn can assist OAI by providing structural and morphological tissue information. This aids the acquisition of information regarding the position and depth of the labelled stem cells. Donnelly et al. used the hybrid OA/US imaging system to guide the delivery of plasmonic gold nanosphere (AuNS)-labelled MSCs to the spinal cord for treating neurodegenerative diseases and traumatic injuries . This reFor stem cell therapy, monitoring different stages of cell migration and progress of cell differentiation may be monitored using multimodal imaging methods. To decide which imaging modalities are best suited for specific applications, it is vital to consider what relevant and specific information each imaging modality can provide. Once the imaging modalities are chosen, the careful design of the contrast agent is an essential step for multimodal detection.Stem cell therapies are currently being investigated for cardiovascular diseases such as ischemic heart disease, glaucoma, neurological diseases such as cerebral ischemia, Parkinson’s disease, liver diseases and degenerative musculoskeletal disorders such as osteoarthritis. Thus, it is imperative to optimize the delivery of stem cells and improve the efficacy of these therapies by using exogenous contrast agents in future clinical trials.One of the most challenging issues for successful stem cell therapy is the efficient delivery of stem cells to the tissue of interest without damaging the host tissue. The real-time imaging capabilities of OAI can aid the physician in the clinic regarding the delivery of labelled stem cells to the implantation site. OAI can thus overcome this limitation of MRI by providing real-time guidance during transplantation. Yao et al. developed a trimodal theragnostic probe that increased efficacy of stem cell therapy of ischemic stroke and used OAI to guide intracerebral injection . KubelicOAI demonstrates an immense potential for clinical applications of stem cell tracking due to its ability to provide structural, molecular, functional and kinetic information from endogenous contrast agents like hemoglobin, melanin, lipid and water in addition to labelled cells. OAI can differentiate between oxygenated and deoxygenated blood and allows monitoring of blood oxygenation saturation, thereby making it an attractive imaging technique for stem cell therapies for ischemic diseases.Along with stem cell tracking, OAI also offers immense potential for musculoskeletal diseases due to its additional capacity to identify and characterize soft-tissue inflammation based on the detection of hemodynamic changes. Early detection and grading of inflammation can be beneficial for arthritic patients, as they could be advised to consider a more targeted treatment regime or timely stem cell therapy treatments or to improve their quality of life, for example. Moreover, non-responders could be identified, and treatment modifications could be implemented earlier on a case-by-case basis.The detection and therapeutic monitoring of breast cancer has been a primary focus for employing OAI in the clinic and this has been reviewed in detail . As stemThe main limitations for translating stem cell tracking to the clinic are long term cytotoxic effects of contrast agents, signal dilution as a result of cell proliferation, the insufficient capability of monitoring the viability and functionality of labelled stem cells in vivo and the possibility of uptake of contrast agents by macrophages following stem cell apoptosis. Focusing efforts on the development of biocompatible and multifunctional OAI contrast agents can lead to their rapid clinical translation for stem cell therapy applications. Fundamental information regarding dose optimization, engraftment site preference and the timely delivery of stem cells could be evaluated during long-term in vivo preclinical experiments and can tailor stem cell treatments for individual patients. Moreover, the OAI technology can be used in conjunction with US and MRI as it demonstrates excellent capacity to guide and provide additional information for improving stem cell therapies and allows personal patient management in the clinic.Engineering suitable exogenous contrast agents for stem cell tracking is essential to perform and evaluate therapeutic stem cell delivery and retention in clinical applications. For safe and efficient stem cell therapeutic practices, the ability to monitor the biodistribution of cells and to determine their survival rate after transplantation is an important goal. Furthermore, suitable contrast agents allow monitoring of long-term effects of stem cell transplantation, such as the host immune response and undesired proliferation of implanted cells. At present, there is no imaging modality that can monitor all aspects of therapeutic intervention using stem cells in the clinical setting.While MRI and other imaging modalities have proven successful in tracking stem cells, OAI is of particular interest as a hybrid imaging modality that combines the high contrast of optical imaging with the large depth of ultrasound imaging. Stem cells can be imaged using OAI by labelling them with exogenous contrast agents. The emission and absorption properties of contrast agents used for labelling stem cells allow the extraction of additional molecular information within the imaging voxels. Colloidal stability and biocompatibility of contrast agents reduces the labelled cell’s probability of being detected as a foreign substance in the body after transplantation. Molecular probes that can be easily surface modified for bio-conjugation should be engineered to improve target specificity and long-term stability. The size and geometry of the contrast agent along with its surface charge and functionalization could result in protein adsorption or formation of a protein corona onto the surface of the contrast agent, which in turn could affect its cellular uptake.Is biocompatible and colloidally stableAllows easy surface modificationEnhances cellular uptakeAllows long-term longitudinal monitoringAllows imaging in the second near infrared window (1000–1400 nm)Can detect stem cell viability in real timeCan facilitate multimodal imagingFor future stem cell tracking applications, multimodal and multifunctional contrast agents are an important research area.For OAI, contrast agents that have a high light-to-ultrasound conversion efficiency and a high optical absorption in the NIR optical window are highly advantageous for deeper penetration into biological tissue. Optimal imaging depth can be achieved at 730 nm, or at 1064 nm, which is less sensitive to blood and melanin concentration. A further advantage of the latter is that the MPE for skin is 100 mJ/cm