Nanoparticles with oligonucleotides bound to the outside or incorporated into the matrix can be used for gene editing or to modulate gene expression in the CNS. These nanocarriers are usually optimised for transfection of neurons or glia. They can also facilitate transcytosis across the brain endothelium to circumvent the blood-brain barrier. This review examines the different formulations of nanocarriers and their oligonucleotide cargoes, in relation to their ability to enter the brain and modulate gene expression or disease. The size of the nanocarrier is critical in determining the rate of clearance from the plasma as well as the intracellular routes of endothelial transcytosis. The surface charge is important in determining how it interacts with the endothelium and the target cell. The structure of the oligonucleotide affects its stability and rate of degradation, while the chemical formulation of the nanocarrier primarily controls the location and rate of cargo release. Due to the major anatomical differences between humans and animal models of disease, successful gene therapy with oligonucleotides in humans has required intrathecal injection. In animal models, some progress has been made with intraventricular or intravenous injection of oligonucleotides on nanocarriers. However, getting significant amounts of nanocarriers across the blood-brain barrier in humans will likely require targeting endothelial solute carriers or vesicular transport systems. The development of gene therapy has opened up prospects for the treatment of diseases that affect the central nervous system ,2. Many Several approaches are available for the treatment of monogenic diseases. The complete replacement of a defective gene involves delivery of a large segment of double-stranded genomic DNA 5–10 kBa) to target cells in the CNS. The gene may be integrated into the host cell DNA or act as an episome. Viral vectors are most suitable for delivery of entire genes to cells of the CNS, and this approach has achieved some success particularly with adeno-associated viruses (AAVs), which can hold up to 5 kBa DNA . Nucleic–10 kBa tA number of non-viral delivery systems have also been investigated. Initially, these methods were based on biochemical reagents and intended to produce maximum transfection of the target cells . The useProtect the nucleic acid against enzymatic degradation,Non-toxic and low immunogenicity,Selective internalisation into the target cells of the CNS,Release of the nucleic acid and appropriate expression or activity in that cell type.Nanocarriers are well suited to the transport of oligonucleotides, although they have also been used for entire genes. The requirements for such a nanocarrier can be summarised as:The nanocarriers must not be cleared through the kidney, or removed by mononuclear phagocytes in the liver and spleen, before they have had time to interact with the brain endothelium,They should selectively target the brain endothelium, in comparison with endothelium in other tissues,They must cross the brain endothelial cells with their nucleic acid cargo intact and in sufficient quantity to have a biological effect.These considerations apply to any nanocarrier that is directly injected into the CNS. However, nanocarriers injected intrathecally are limited to the site of injection and if injected into ventricles, they preferentially distribute to areas around the ventricles . IdeallyTo produce a nanocarrier that fulfils all of these requirements is extremely challenging . ProgresParacellular movement through the junctions between endothelial cells.Direct movement across the apical plasma membrane, cytosolic transport or diffusion across the cell and transfer across the basal plasma membrane.Vesicular transcytosis—endocytosis at the apical (blood) surface of the endothelium and exocytosis at the basal (brain) surface.The blood-brain barrier presents both an anatomical and biochemical barrier for movement of large biomolecules from the capillaries to the brain parenchyma ,14. AnatEach of these routes is highly restrictive. The continuous, tight junctions between brain endothelial cells are formed by fusion of the outer membrane leaflets of adjacent cells by occludin and members of the claudin family including claudin-5. The multiple strands of tight junction proteins extend over 200–500 nm and they prevent paracellular diffusion of the great majority of polar molecules >1 kDa molecular weight. The smallest nanocarriers are 2–3 nm in diameter and 20–30 kDa—a similar size to plasma proteins—and they are unable to move through the intercellular junctions. In some circumstances, the junctions can become leaky—for example, at sites of inflammation—in response to inflammatory cytokines and chemokines  . Viral iSome very small nanoparticles can directly cross the plasma membrane by a mechanism called ‘snorkelling’. This involves temporary integration into the plasma membrane and reorganisation of the surface ligands on the nanoparticle . This efVesicular transcytosis is potentially the best route for bulk transfer of large molecules or nanocarriers across the brain endothelium . CaveolaTransport vesicles are generally selective in terms of the material they transport. Specific transport can be absorptive or receptor-mediated. In absorptive transport, the cargo interacts with the endothelial glycocalyx or surface glycoproteins at specialised zones of the plasma membrane called lipid rafts. In the brain endothelium, the glycocalyx has a particularly high negative charge due to sulphation of carbohydrates, and this promotes binding of positively charged serum molecules or nanoparticles .In receptor-mediated transport, the specific ligand binds to the receptor on the endothelial surface before internalisation. Many solute carriers are present on the brain endothelium for transport of small metabolites required by the CNS. The solute carriers generally transport small molecules across the apical plasma membrane to the cytosol, and therefore, are not suitable for direct transport of nanocarriers. However, the solute carriers can be used for selective targeting of nanoparticles to the brain endothelium. More relevant for vesicular transcytosis are the receptors that transport large biomolecules to the CNS, including the transferrin-receptor (TfR1) LDL-receptor (LRP1) and insulin receptor. The targeting of nanocarriers is outlined in more detail in In some areas of the brain, the endothelium is fenestrated and nanoparticles can cross the endothelium by the paracellular route. These areas, lacking a conventional blood-brain barrier, are located near ventricles (circumventricular organs); they occur in areas of the CNS that respond to substances in the blood. Larger serum proteins and small nanoparticles pass the endothelial barrier in these regions although they may be blocked at the glial barrier. The choroid plexus is one example of an area lacking an endothelial barrier, but in this case, a barrier with tight junctions is present on the choroid plexus epithelium. Even if nanoparticles reach the cerebrospinal fluid, they still cannot directly access the brain parenchyma because of the ependymal/glial barrier. Only a tiny proportion of drugs injected into the blood or ventricles normally reaches the brain parenchyma; for this reason, it is essential when quantitating transport to verify exactly where in the brain the drug/treatment is located .In summary, the treatment of CNS diseases by gene therapy with oligonucleotides has great potential, but gene delivery is the limiting factor. This is particularly true if the nanocarrier must cross the blood-brain barrier to provide widespread distribution in the CNS. Considerable progress has been made with the delivery of smaller therapeutic agents to the CNS by encapsulation within nanoparticles , but anyAltering splicing of the primary RNA transcript, to include or exclude specific exons.Increasing the degradation of mRNA by inhibiting methylation of the 5′-cap on mRNA.Inhibiting the nuclear export of mRNA by preventing addition of the poly-A tail. This also promotes its breakdown by 3′ exonucleases.Blocking the translation of mRNA by inhibiting ribosome attachment or progress down the mRNA strand.Increasing mRNA’s availability by blocking its interaction with long non-coding RNAs (lncRNA).Forming DNA-RNA hybrids or dsRNA, which are substrates for RNAse H.Promoting the breakdown of mRNA by micro-RNAs (MiRs) or short interfering RNA (siRNA)Acting as guide RNA (gRNA) for gene-editing by CRISPR/Cas9.Oligonucleotides (10–50 bp) are too small to encode proteins. They can act at different points in the cell by modulating the production or translation of host mRNA. The ways in which oligonucleotides can act include:Some of these mechanisms are directly due to blocking of active sites on the RNA transcript or mRNA , whereasSome cellular processes, including RNA splicing and mRNA breakdown by MiRs and siRNA, specifically require complementary RNA as their substrate. The action of MiRs and siRNA both involve recognition of dsRNA by the cytoplasmic RNA-induced silencing complex (RISC). This complex includes the RNAse argonaute, which selects a guide strand from the MiR or siRNA. The single-stranded RNA binds to complementary sites in the 3′ untranslated region of mRNA and promotes breakdown of the mRNA by removal of the poly-A tail and subsequent loss of the 5′ cap. These processes taking place in the RISC are RNA-specific.Similarly, gene-editing by CRISPR/Cas9 requires gRNA as a guide to target the complex to the specific point in the genome that is to be edited .The problem of oligonucleotide stability has been partly solved by chemical modification of the nucleotides, in order to increase resistance to nucleases . The firFor treatment of single gene disorders, it may only be necessary to deliver a small number of oligonucleotides to the target cell. For example, correction of a single nuclear gene by gene editing would require a single treatment with a relatively small number of guide oligonucleotides. Conversely, treatment of a condition to reduce cytoplasmic mRNA by binding of ASOs, MiRs or siRNA to the mRNA requires many oligonucleotides to be targeted to individual cells. The same consideration applies for treatments aimed at altering RNA splicing. Moreover, in all of these cases, repeated treatments may be required as the defective nuclear gene continues to produce defective RNA. The problem can partly be overcome if the oligonucleotide is transcribed from a therapeutic transgene integrated into the host cell. However, this in itself requires transfection of the cells with longer gene segments than the therapeutic oligonucleotide, usually with viral vectors.Many oligonucleotides have been examined in vitro and in animal models of CNS disease for their ability to modulate target gene expression or alleviate disease symptoms. At this time, a small number of oligonucleotide treatments have been approved for use in humans, including treatments for amyotrophic lateral sclerosis (ALS)  and spinA number of other oligonucleotides have shown potential in animal models of disease ,34,35,36The selection of the sequence of the oligonucleotide and its nucleotide composition is clearly critically important in determining how the oligonucleotide will act within the cell and whether it will be therapeutically useful. In particular, for conditions such as Huntington’s disease, gene editing must specifically target the mutant allele with an allele-specific oligonucleotide . HoweverA large variety of nanoparticle-oligonucleotides have been tested for their ability to transfect cells and for treatment of disease models . NanoparFor delivery of oligonucleotides to the CNS, various small nanocarriers have been synthesised with cores consisting of gold, silica or iron ,43,44,45Gold glyconanoparticles have a core of 2–4 nm and a surface coat of thiolated sugar residues  attached to the core via their sulphur atom . These nMesoporous silica nanoparticles have been regularly used for transport of small drugs, but the pore size is normally too small to accommodate oligonucleotides.  For gene therapy, silica nanoparticles are usually first coated with cationic molecules and the nucleic acids are non-covalently bound on the outside .Iron oxide nanoparticles with a core of 5–11 nm have been used for imaging in the CNS and to deliver peptides across the blood-brain barrier. The major advantage of these nanoparticles is that they are paramagnetic and can be used for imaging and theranostics.  External magnetic fields can then be used to induce movement across the brain endothelium ,50. HoweCyclodextrins that can form molecular cages containing siRNA have been used in vitro .Liposomes vary greatly in size depending on the number of layers of phospholipid in the shell and on the size and composition of the core, which contains the oligonucleotides (see below).For larger nanocarriers, the cargo is usually incorporated into the core, and is not covalently attached to the nanoparticle. This allows a progressive controlled release, which is more useful for small drugs. More important is that the nucleic acids are better protected from enzymic degradation. Larger carriers can also incorporate targeting antibodies or peptides on the outside, and/or fluorescent or magnetic trackers, to improve localisation to target cells or imaging. Because of their size, these carriers are generally less able to cross the blood-brain barrier, although there are exceptions. Initially, the formulation of these nanoparticles has followed standard practise intended to optimise transfection of the target cell . For thePolymer nanocarriers include polyethyleneimine (PEI), poly-(lactic coglycolic acid) PLGA, chitosan and collagen . PolyethCationic liposomes containing DNA or RNA are small spherical vesicles composed of a hydrophilic core enclosed by a single or multiple phospholipid bilayers . They caProtein nanoparticles  coated with apolipoprotein-A can cross the blood brain barrier and move rapidly within the CNS . HoweverLipid nanoparticles in the range of 20–100 nm have potential for transport across the brain endothelium, particularly if suitably modified . siRNA hNanocarrier size has a major effect on their tissue distribution following intravenous injection ,67. In tDue to the very low penetration of the brain by nanocarriers, several methods have been proposed to improve their uptake and/or transport . SurfaceThe brain endothelium has numerous solute carriers for small metabolites, which could, in theory, act as targets for the initial selective binding of circulating nanocarriers to the brain endothelium. The glucose-transporter Glut-1, strongly expressed on the brain endothelium, is a potential target. However, most nanocarriers and oligonucleotides cannot be transported by the physiological transport actions of the solute carriers as the nanoparticles are too large. It is, however, possible to modify an oligonucleotide or a nanoparticle containing oligonucleotides with the substrate  so they can engage with the receptors ,74. In tBecause of the limitations of the solute carriers, targeting of nanoparticles has focussed on transporters of larger biomolecules, which are taken up by endocytosis and which may then be released at the basal surface of the endothelium . The priTfR1 is involved in uptake of the iron-transport protein transferrin, and is expressed particularly on dividing cells. It recycles between the apical membrane of the brain endothelium and endosomes where the transferrin is uncoupled. A smaller proportion of the receptors transfer to the basal membrane. The receptor has been targeted by antibodies, antibody fragments and peptides ,78. InteThe LDL receptor LRP1 transports cholesterol and lipids for neurons and glia, but it is also involved in removal of amyloid-β from the brain. As such, it shuttles between the apical and basal membranes of the endothelium and can bind nanoparticles with surface apoE . CholestBoth TfR1 and LRP1 have been targeted for transport of nanoparticles into the brain by attaching receptor-binding polypeptides to the outer surface of the nanoparticles . It is iFinally, a number of physical methods have been used to enhance nanoparticle delivery in vivo, including a focussed ultrasound to increase the transport of gold nanoparticles  and magnDelivery of large therapeutic biomolecules to the CNS is difficult. For proteins and peptides injected intravenously, the concentration in the brain intercellular space is usually much less than 0.5% of the level in serum, but is dependent on the size, shape and charge of the biomolecule . SimilarStudies on intraventricular injection of RNA in animals have shown that it spreads over a surprisingly large distance into the tissue. In humans, the success of treatments for ALS and SMA as well as observation of post-mortem tissue implies that a significant dose of oligonucleotide can reach cells in the spinal cord, presumably by diffusion of CSF through the subarachnoid space and central canal and transfer across ependymal cells . HoweverA small number of studies have used the olfactory route to deliver oligonucleotides  or nanopBecause of these anatomic factors, it would be very desirable to deliver nanocarriers across the blood-brain barrier when treating conditions in humans where large areas of the brain are affected. It is estimated that all cells of the CNS lie within 100 µm of a capillary. Consequently, if the blood-brain barrier can be overcome, the diffusion distance for nanocarriers within the brain is relatively small. It might be thought that the tortuous intercellular spaces within the brain would still make the diffusion pathway for nanoparticles much longer than the direct distance from the capillary to the target cell. However, with both lipid nanoparticles and gold nanoparticles, it appears that nanoparticles that have crossed the blood-brain barrier can move relatively quickly within cells of the brain parenchyma (up to 5 µm per minute), possibly using intracellular transport systems ,80.When crossing the brain endothelium, nanocarriers can move via the transmembrane/cytosolic route or by vesicular transcytosis . Those eThe intracellular route taken by a nanocarrier depends on its size, charge and surface ligands. Electron microscope studies imply that some small nanoparticles and larger lipophilic nanoparticles are taken up directly into the cytoplasm—no membrane is visible around the nanoparticle. More often for nanoparticles in the range of 10–100 nm, they are initially taken up into membrane-bound vesicles, usually caveolae.A potential problem during transcytosis is loss of the nanocarrier and cargo by diversion of endosomes to the endothelial lysosomes . The extUltimately, transported oligonucleotides must enter the cytoplasm of the target cells. As noted earlier, nanocarriers used for direct intrathecal injection have usually been optimised for their transfection efficiency. However, nanocarriers optimised for transport across the brain endothelium by vesicular transport also appear to enter endosomes in target cells, and they must escape into the cytoplasm before they can have a biological effect.Nanocarriers offer several advantages for the delivery of therapeutic oligonucleotides to the CNS by protecting the nucleic acid, increasing transport across the blood-brain barrier and improving transfection of the target cells. A great variety of nanocarriers have been used for this purpose, varying in chemical formulation, size, charge and carrying capacity. No single nanocarrier has the best characteristics for transport into the brain and transfection efficiency. Moreover, any nanocarrier injected intravenously has to first avoid removal via the kidney or clearance by mononuclear phagocytes in the spleen or liver. For this reason, all oligonucleotide treatments approved for use in humans to date are delivered by intrathecal injection. Several nanocarriers with oligonucleotide cargoes have shown effective CNS gene modulation in experimental animal models of disease. This suggests that intravenous delivery of nanocarriers may also be possible in humans. However, the anatomical differences between humans and rodents mean that gene delivery across the blood-brain barrier is both more desirable in humans than intrathecal injection and also considerably more difficult.


Lipedema is a chronic disorder of the adipose tissue that affects mainly women, characterised by symmetrical, excessive fatty tissue on the legs and pain. Standard conservative treatment is long-term comprehensive decongestive therapy (CDT) to alleviate lipedema-related pain and to improve psychosocial well-being, mobility and physical activity. Patients may benefit from surgical removal of abnormally propagated adipose tissue by liposuction. The LIPLEG trial evaluates the efficacy and safety of liposuction compared to standard CDT.n=405) without previous liposuction will be allocated 2:1 to liposuction or CDT. The primary outcome of the trial is leg pain reduction by ≥2 points on a visual analogue scale ranging 0–10 at 12 months on CDT or post-completion of liposuction. Secondary outcomes include changes in leg pain severity, health-related quality of life, depression tendency, haematoma tendency, prevalence of oedema, modification physical therapy scope, body fat percentage, leg circumference and movement restriction.LIPLEG is a randomised controlled multicentre investigator-blinded trial. Women with lipedema (The primary analysis bases on intention-to-treat. Success proportions are compared using the Mantel-Haenszel test stratified by lipedema stage at a 5% two-sided significance level. If this test is statistically significant, the equality of the response proportions in the separate strata is evaluated by Fisher’s exact test in a hierarchical test strategy.LIPLEG assesses whether surgical treatment of lipedema is safe and effective to reduce pain and other lipedema-related health issues. The findings of this trial have the potential to change the standard of care in lipedema.ClinicalTrials.gov NCT04272827. Registered on February 14, 2020.Protocol version is 02_0, December 17, 2019The online version contains supplementary material available at 10.1186/s13063-021-05727-2. Lipedema was first described in 1940 by Allen and Hines   is part of the standard conservative treatment . OriginaCDT consists of a combination of lymphatic drainage, compression therapy , skin care and physical activity. It is unclear whether CDT influences the progression of pain in addition to the abovementioned benefits. However, the specific fat accumulation and distribution with the accompanying pain and tendency to form haematomas remain . PhysicaStarting in the 1990s, liposuction has emerged as the most important surgical intervention for lipedema. The pathologically altered subcutaneous fatty tissue is surgically removed without damaging the lymphatic system. Liposuction methods are tumescent anaesthesia (TA) and water-assisted liposuction (WAL). In TA, several litres of an anaesthetic solution are infused into the subcutaneous area (‘wet technique’) so that the fat cells swell and vessels constrict. Then, the subcutaneous fat is suctioned off by a very fine, blunt, vibrating cannula . In WAL, a jet of water releases the fat cells from the connective tissue and a mixture of fat cells, water and tumescent solution is aspirated –16. ThisLiposuction leads to reduction of lipedema-specific fat accumulation and distribution, pain sensitivity, edema, tendency to haematoma and restriction of movement , 19. An Liposuction is therefore discussed as a useful addition to or even alternative therapy for CDT, especially in the early stages of lipedema in order to prevent possible long-term effects such as the development of secondary lymphedema and disease progression, to improve the quality of life and to reduce the need for CDT , 20–22.In summary, clinical experiences as well as small trials demonstrate a positive effect of liposuction in lipedema with respect to pain, movement improvement and quality of life. However, controlled and randomised clinical trials comparing conservative and surgical treatments with valid statistical methods are missing. There is no evidence that surgical treatment is equivalent or even superior to conservative treatment with respect to pain in lipedema stages I, II and III. Therefore, a large-scale randomised controlled investigator-blinded trial will be performed with the aim to provide a definitive answer.Complex decongestive therapy is the standard of care for patients with lipedema. Liposuction is a non-standard alternative. The rationale of the LIPLEG trial is to compare effectiveness using leg pain reduction as the primary outcome in the two treatment groups.The primary objective of the trial is to investigate whether the surgical treatment (treatment A) is superior to conservative treatment (treatment B) by comparing leg pain after 12 months. The secondary objective is to estimate the potential benefit of liposuction for the patient by evaluating changes in the severity of pain in the legs, health-related quality of life, depression and haematoma tendency, prevalence of edema, modification in the scope of conservative therapy, body fat percentage, leg circumference and movement restriction.The primary outcome is the reduction of pain in the legs 12 months after completion of liposuction or after 12 months of treatment by CDT upon randomisation, respectively .Change in the severity of the pain in the legsChange in health-related quality of life according to Short Form 36 (SF-36), Dermatology Life Quality Index (DLQI) and World Health Organization Quality of Life-abbreviated version of the WHOQOL 10 (WHOQOL-BREF)Altered depression tendency according to Patient Health Questionnaire-9 (PHQ-9)Altered haematoma tendencyPrevalence of edemaModification in the scope of physical therapyBody fat percentageChange of leg circumferenceReduction of the movement restriction Occurrence of (serious) adverse events during the trialLIPLEG is a multicentre, controlled, randomised, investigator-blinded trial. Female patients with lipedema interested in participating in the trial could register in an online portal until the end of December 2019. The patients are randomly drawn and assigned to a trial site according to the nearest post code. Then, the patients will be contacted by the trial sites and assessed for eligibility by telephone interview. If the patient is assessed as eligible, a screening visit on-site will take place in order to check the inclusion and exclusion criteria. Patients will be considered for enrolment when all inclusion criteria are confirmed, and none of the exclusion criteria is fulfilled. Four hundred five patients are planned to be included in the trial and assigned in a ratio of 2:1 to treatment group A (liposuction) or B (CDT). The investigator assessing the primary and secondary outcomes will be blinded. The surgeon, patients and further investigators will not be blinded for the allocated treatment. Since lipedema mainly affects females, males will not be included in the study.ClinicalTrials.gov NCT04272827.The trial will be performed in > 10 trial sites in Germany, which are listed on Only specialised trial sites (Dermatology or Plastic Surgery) are eligible for participation in the trial. Only principal investigators (PI) and participating trial sites that meet the necessary requirements, with qualifications and experience to conduct a clinical trial, are selected for the trial. Furthermore, only surgeons with sufficient experience in liposuction surgery can perform the liposuction in the trial. The sponsor designates the PI at each trial site, who selects qualified and experienced personnel to conduct the trial.All trial sites will be trained during the initiation visit by the clinical research associate (CRA).Inclusion criteriaSigned informed consent formFemaleAge ≥18 yearsLipedema of the legs stages I, II or IIIAverage pain in the legs over the last 4 weeks ≥ 4 points on a numerical rating scaleDocumentation of an insufficient complaint relief by conservative methodsWillingness and ability to take conservative measures according to the study plan, during and, if necessary, after the liposuction treatmentFull legal capacityExclusion criteriaSimultaneous lipedema of the arms and legs in which the involvement of the arms influences the primary outcomePrevious liposuctionsDiseases affecting operability Diseases influencing adequate CDT, e.g. heart failure (volume stress), lack of physical ability to wear compression stockings .Primary obesity without disproportion and without reference to lipedemaSecondary obesityFat distribution disorders of other genesis Other edema causing diseases Lack of willingness to provide adequate contraceptionPositive pregnancy testLactation periodUsage of a lymphomatParticipation in other clinical trialsCosmetic motivation for participation in the trialIn order to establish same starting conditions for all patients before randomisation, the trial participants initially receive CDT as recommended by the investigator in a run-in phase. The first part (phase I) of the run-in phase serves to eliminate edema within a maximum period of 4 weeks, followed by the second part (phase II), in which patients are treated with standardised CDT for a further 6 months to maintain the results achieved in phase I. Patients are then randomly assigned to one of the two treatment groups  provided that all inclusion criteria are still met (and no exclusion criterion is fulfilled).In the liposuction group, patients receive liposuction treatment using the wet technique. Techniques such as vibration (PAL) or water jet (WAL) can support the procedure depending on the amount of fat that is to be removed. A maximum of four surgical sessions is possible. CDT therapy is continued to the necessary extent for progression prophylaxis.The CDT group is treated with CDT alone for further 12 months upon randomisation to maintain at least the results obtained at the end of the run-in phase. After this period, patients will be offered liposuction treatment provided all inclusion and exclusion criteria are still valid.A screening visit (baseline visit) on site will be performed by the investigator including written informed consent, check of inclusion and exclusion criteria, and medical history. The following parameters are recorded on the screening visit as well as on the subsequent visits: weight, supplementary medications, leg circumference, occurrence of leg edema, haematoma tendency, validated questionnaires for the determination of pain (German pain questionnaire), quality of life , depression (PHQ-9), overall impairment modified according to Schmeller  and funcFor the optional ancillary treatment of lipedema, physical activities, especially water sports, are permitted, as recommended in the guidelines. However, the type and intensity of these should not be changed for the duration of the study. The supportive use of lymphomatics, on the other hand, is not permitted in the context of a desired homogeneous group of patients. After the end of the clinical trial, participants will be treated according to standard of care.Patients can withdraw at any time during the trial without providing a reason and without any personal disadvantage. A patient may also be withdrawn if, on the basis of the investigator’s judgement, continuation of the trial may be detrimental to the participant’s health. Further reasons for the investigator to discontinue a patient’s trial participation includes, e.g. insufficient compliance, patient becomes pregnant before reaching the primary outcome, inclusion and exclusion criteria are no longer met after the run-in phase. Reasons for all withdrawals will be recorded in the patient’s medical file and their electronic case report forms (eCRFs). All data will be analysed according to the intention-to-treat principle.Efficacy assessments include the primary and secondary outcomes described above. The choice of these measuring instruments is based on the fact that lipedema has far-reaching effects on various socially relevant areas of the patient’s life that are covered by these measuring instruments.Data will be recorded on eCRF. The primary outcome, pain in the legs, is collected either 12 months after the final liposuction surgery in the liposuction group or 12 months after randomisation in the CDT group by using the German Pain Questionnaire . OccurreAccording to the results of Schmeller et al. , 23, thePatients are randomly assigned to the treatment groups  centrally using the 24/7 Internet randomisation service ALEA  in a 2:1 ratio  based on permuted blocks of varying length as provided by ALEA using a pseudo-random number generator. Assignment is stratified by stage of lipedema and trial site. The randomisation service is set up and maintained by the Institute of Medical Statistics and Computational Biology, University of Cologne. Programming (using a web-interface) and validation of the service are done according to the Institute’s SOPs. The assignment of the groups can be made by all investigators, except the investigator (blinded investigator) carrying out the clinical assessments and questionnaires after surgery who should not be aware of who is receiving liposuction or CDT. The randomisation sequence is concealed from all clinical staff, i.e. only ALEA service administrators have access to the sequence.This study is a single-blind (investigator-blinded) trial. After randomisation, all examinations will be conducted by an investigator who will be blinded to the treatment allocation. Therefore, the surgical scars are taped by unblinded study personnel before each visit (dummy patches in the control group) and patients are asked not to disclose the received therapy to the blinded investigator. The blinded examination of the patient must not be performed by a surgeon or an unblinded investigator. The blinded investigator is not allowed to access the database and is informed that he is not allowed to view the patient’s file of the patient he is examining (except in an emergency). The data collected by the blinded investigator are documented on working sheets and entered into the eCRF by unblinded study personnel in a timely manner.The analysing statistician will also be kept masked to treatment assignment until the final statistical analysis is completed.The IT infrastructure and data management are provided by the Clinical Trials Centre Cologne (CTCC).TM (Anjusoftware.com) is used as a data management system, ensuring data safety by a firewall and backup system and including multiple data storage sites. The data are backed up daily.The trial database is developed and validated by CTCC on the basis of standard operating procedures. All changes made to the data will be documented in an audit trail. The commercial online software TrialMasterAll relevant trial data collected during the trial are documented soon after data gaining and entered into the eCRF by the responsible investigators or a person authorised by the principal investigator (exception of the blinded investigator).This includes all outcomes measures and questionnaires. Automatic plausibility checks are run during data entry to immediately detect discrepancies. Data management of the CTCC carries out checks on the completeness and plausibility of the study data and clarifies all queries with the study centre electronically via the trial software. These queries must be answered promptly by the study centre. The eCRFs are signed by the principal investigator at the end of a patient’s trial participation to confirm the accuracy of the data. After completion and cleaning of the data, the database is closed and the data will be exported for statistical analysis.To monitor risks and ensure the data quality of the trial, a central quality control process (CQC) is set up.Using CQC, the performance of the trial sites indicating the documentation rate, documentation quality, and recruitment rate will be evaluated. In the case of conspicuous data (e.g. incorrect or insufficient documentation), this quality control process allows for early intervention and correction of errors.The provisions of the EU data protection basic regulation and data protection laws including their national implementation in Germany are observed. It is ensured that all investigational materials and data are pseudonymised in accordance with data protection regulations before scientific processing.Patients will be informed that their pseudonymised data will be passed on in accordance with provisions for documentation and notification pursuant to § 12 and § 13 of the Good Clinical Practice (GCP) regulations to the recipients described there. Patients, who do not agree to the data handling as described in the informed consent, will not be included in the trial.0: odds ratio = 1 vs. HA: odds ratio ≠ 1). If this test is statistically significant, the equality of the success rates in the separate stages is evaluated by Fisher’s exact test . A missing primary outcome or change of the randomly assigned treatment is counted as failure. No interim analysis is planned. Secondary is the analysis of patients treated and observed per protocol . Secondary and further outcomes are evaluated without adjusting for multiple hypothesis testing . Distributions of quantitative variables are described as mean (standard deviation) and percentiles , qualitative variables are summarised by count and percentage. The impact of missing outcome data is assessed by sensitivity analyses based on single/multiple imputation. The information on AEs is assessed , coded and summarised by contingency tables. Subgroup analysis is done by patient age, study centre and surgeon.The primary analysis is according to the intention-to-treat. The primary outcome ‘success’ is evaluated by the stratified (by stage) Mantel-Haenszel test  at two-sThe trial sites will be monitored closely to ensure patient’s safety and the quality of the data collected. Monitoring is performed risk-based. The CRA will review informed consent forms, verify the completeness and accuracy of the patient data collected and ensure that the trial is conducted in accordance with the protocol, ICH-GCP principles and legal requirements.Each trial site received a site selection visit to ensure staff qualification and experience, and sufficient capacity and equipment. The initial training of each site was performed during an initiation visit prior to trial start. A total of 140 regular monitoring visits are planned. The frequency of the regular monitoring visits at the trial site depends on the recruitment rate and the quality of the documented data at the trial site. Each site will also receive a close-out visit, for formal termination of the trial at the respective trial site.A Data Monitoring Committee (DMC) oversees the safety of the patients in the trial by periodically assessing selected trial safety datasets and their influence on the risk-benefit assessment for patients and the justifiability of further trial conduct. The DMC receives a list of AEs and SAEs at regular intervals. As described in a separate DMC manual, the assessment of SAEs is based on the absolute rates, and the difference in rates and the temporal development of the SAEs that occurred. Based on this, the DMC will make recommendations on continuation, modifications or even termination of the trial to the sponsor. It consists of two physicians and a statistician, who are independent experts, not otherwise involved in the conduct of the trial, and operate based on an agreed charter.All AEs and SAEs occurring during the trial will be documented in the patient’s medical records and the eCRF, including date and time of onset and resolution, severity, causal relationship with CDT/liposuction, seriousness and measures. In addition, SAEs are immediately sent to the principal coordinating investigator (PCI) via an automatic e-mail notification directly from the database. The risk-benefit ratio will be checked by the PCI based on a list of AEs that have occurred up to that point, which is made available at regular intervals by the CTCC. All safety-relevant events will be promptly reported to the Ethics Committees and the DMC.No auditing is planned during the trial. However, the sponsor has the right to carry out quality assurance audits at the trial site and other institutions that may be involved in the study, whenever deemed necessary. The aim of audits is to check the validity, verifiability and completeness of the data and the credibility of the clinical study as well as to check whether patients’ rights and safety are guaranteed. The sponsor can commission people who are otherwise not involved in the clinical trial (auditors). They are permitted to inspect all trial-related documents .The sponsor and all participating trial sites commit to support auditors and, in this context, to grant the authorised persons access to the original documents.All auditors commit to treat personal and other data confidentially.The trial was approved by the following Ethics Committees: Ethics Committee of the Hesse State Chambers of Physicians , Ethics Committee of the Medical Association of North Rhine (reference number: 2019316), the Ethics Committee of the Saxon State Chambers of Physicians (reference number: EK-BR-76/19-1), Ethics Committee of the Brandenburg State Chambers of Physicians (reference number: AS 117(bB)/2019), Medical Ethics Committee of the University of Oldenburg (reference number: 2020-009), and Ethics Committee of the Baden-Württemberg State Chambers of Physicians (reference number: B-F-2019-075). The ethics committee of the University of Regensburg and of Bavarian Medical Association does not require an additional ethics vote, after the study protocol has been approved by other German ethics boards. In case of important protocol modifications, the PCI will inform the PIs of all trial sites. They will then forward the amendments to the associated ethics committees and trial participants. Written informed consent is provided by all participants prior to any trial procedure. A patient insurance policy is taken out for all included patients. Address, insurance number, telephone and fax number of the insurance company are included in the informed consent. In addition, patients will be insured for travel to the way to the regarding trial site.The trial is conducted in accordance with the International Conference on Harmonisation for Good Clinical Practice (ICH-GCP). The trial will always comply with the Declaration of Helsinki.The results of this trial will be submitted for publication in peer-reviewed scientific journals and presented at national and international conferences.Lipedema, first described by Allen and Hines in 1940 .The phenotype is characterised by a typical bilateral disproportionate distribution of adipose tissue on the extremities. Main symptoms include a progressive symmetrical non-pitting, fatty swelling of the extremities, with recessing of the hands/feet, easy bruising, pain and lack of response to weight reducing diets .Up to now, there are no curative therapies for lipedema. As an insufficiently managed lipedema will likely progress to lipo-lymphedema, the management of the disease is crucial and consists of two main goals: firstly, improvement of the subjective discomforts (e.g. pain) and secondly, the prevention of further complications  .Conservative treatment such as manual lymph drainage, multi-layered short stretch bandaging or medical compression stockings can ameliorate the pain of lipedema patients and prevent a concomitant edema formation . A reducLiposuction as a surgical intervention is an accepted therapeutic approach for the treatment of lipedema, especially when conservative therapies are insufficient or have failed , 28. LipUp to now, conclusive long-term data are still missing, but short-term results seem promising, especially when the intervention is performed in an early stage of the disease in wet-technique with blunt cannulas , 22, 29.The LIPLEG trial assesses whether surgical treatment of lipedema is safe and effective to reduce pain and other lipedema-related health problems.Moreover, this study is the first randomised controlled and blinded study to compare conservative to surgical treatment. The findings of this trial will potentially influence standard of care in lipedema.ClinicalTrials.gov Identifier: NCT04272827, registered on 14 February 2020). Recruitment of participants is expected in December 2020, last patient’s last visit is expected in summer 2025.The authors confirm that the trial was registered prior to the submission of this manuscript (Additional file 1. SPIRIT 2013 Checklist


Ultrasound computed tomography (USCT) systems based on capacitive micromachined ultrasonic transducer (CMUT) arrays have a wide range of application prospects. For this paper, a high-precision image reconstruction method based on the propagation path of ultrasound in breast tissue are designed for the CMUT ring array; that is, time-reversal algorithms and FBP algorithms are respectively used to reconstruct sound speed distribution and acoustic attenuation distribution. The feasibility of this reconstruction method is verified by numerical simulation and breast model experiments. According to reconstruction results, sound speed distribution reconstruction deviation can be reduced by 53.15% through a time-reversal algorithm based on wave propagation theory. The attenuation coefficient distribution reconstruction deviation can be reduced by 61.53% through FBP based on ray propagation theory. The research results in this paper will provide key technological support for a new generation of ultrasound computed tomography systems. High-sensitivity transducer arrays and high-precision acoustic parameter reconstruction methods are the key factors of high-performance USCT systems. In terms of ultrasonic transducers, piezoelectric transducers are most commonly used in the USCT system. However, the image resolution is limited by the consistency of transducers. CMUT fabricated by MEMS micromachining technology has the advantages of broadband, high sensitivity, low power consumption, low cost, high consistency, and high integration, which can meet the needs of developing a USCT system with higher resolution . In the In terms of the acoustic parameter reconstruction method, USCT uses both transmission and reflection data to provide quantitative images of breast tissue acoustic properties ,3,4,5,6.In view of the above problems in the reconstruction of breast tissue acoustic parameters, this paper proposes a reconstruction method based on ultrasound propagation characteristics in breast tissue oriented to the CMUT ring array. The time-reversal algorithm and FBP algorithm, respectively, are used to reconstruct the sound speed image and the acoustic attenuation image. The projection data required by the two methods can be obtained from the same received signals, which not only ensures the accuracy of image reconstruction but also reduces the calculation time. This method is possible to accelerate the clinical application of breast USCT systems. In the following contents, the structure of CMUT and ultrasonic tomography systems based on the CMUT ring array are introduced initially. Subsequently, taking a CMUT ring array as an example, a reconstruction algorithm of sound speed and acoustic attenuation is given, and an actual implementation method is proposed under the background of USCT. Lastly, numerical experiments and breast model experiments are implemented to verify the accuracy and feasibility of using wave theory to reconstruct sound speed and ray theory to reconstruct acoustic attenuation. The research results in this paper lay a good theoretical and practical foundation for the new generation of USCT systems.In this paper, a novel ultrasonic tomography system based on a CMUT ring array is designed  primarilThe system is mainly composed of a 1024-element cylindrical array detector, an ultrasonic signal transmitting and receiving control circuit, and a computer workstation. The structure of the CMUT cell is shown in A high computing efficiency and high-resolution reconstruction method for breast tissue acoustic characteristics is proposed, oriented to the CMUT ring array. This has both the advantages and disadvantages of existing acoustic parameter reconstruction algorithms and is required for accurate and rapid detection of small lesions in early breast cancer. Ultrasound propagation models based on wave theory are used to reconstruct sound speed, that is, the arrival time of ultrasound signals is recorded by all elements of the ring array. Ultrasound propagation models based on ray theory are used to reconstruct the attenuation coefficient, that is, the amplitude attenuation of ultrasound signals is recorded by the elements of the three-quarter ring array that are directly opposite to the transmitting element.Ultrasound transducer ring arrays composed of The ring array surrounds the breast tissue for which the acoustic properties need to be imaged. In this part, the propagation speed of the ultrasound signal in breast tissue is estimated . In the It maps the objective function The goal of reconstruction algorithm is to solve the above nonlinear equations, that is, to recover the objective function In order to solve the nonlinear Equation (3), the following cost functions need to be minimized:With a linear relationship, the following update equation can be used to minimize the total cost function (4):When Algorithm 1 Sound Speed Inversion1. Propagate the signal Compute the residual between the measured signal Propagate the residual in a time-reversed manner to obtain the field 2. For each source m,3. ε, stop. Otherwise, go to step 2.4. Ultrasound transducer ring arrays composed of The attenuation coefficient of breast tissue was reconstructed by a filtered back-projection reconstruction method based on equiangular fan beam scanning. The parameter relationship of this method is shown in Therefore, the reconstruction formula of attenuation coefficient expressed by fan beam projection data and variables is as followsAlgorithm 2 summarizes the reconstruction method of attenuation coefficient, as shown in Algorithm 2.Algorithm 2 Attenuation Coefficient InversionInput: projection data (amplitude attenuation) 1. 2. 3. Loop the coordinate of each pixel to be reconstructed in the main cycle, and loop from 0 to 360° in a sub-cycle, representing different angles between the central ray and the 4. 5. 6. 7. Interpolate linearly, and accumulate the projection data after filtering.8. End the sub-cycle and obtain the parameter value at that point through the cumulative sum.9. End the main cycle and obtain the parameter values of each point of the image through the cumulative sum.Output: Image of breast tissue attenuation coefficient.In order to verify the effectiveness of the reconstruction method proposed in this paper, projection data of ultrasound tomography imaging using the CMUT ring array are simulated by using the finite element simulation method. The ultrasound imaging system model shown in Reconstructed sound speed distributions and attenuation coefficient distributions are shown in It can be seen from the reconstruction results of breast phantom that sound speed distribution can be recovered with higher precision through the time-reversal algorithm based on wave propagation theory than through FBP based on ray propagation theory. The attenuation coefficient distribution can be recovered with shorter calculation time and higher precision through FBP based on ray propagation theory than with a time-reversal algorithm based on wave propagation theory. According to the reconstruction result of sound speed , deviatiIn order to further verify the effectiveness of the reconstruction method proposed in this paper, the experimental platform shown in In order to further quantify the quality of reconstruction, the average and standard deviation of pixel values in mass located in the breast model are obtained and compared with the expected values of the acoustic characteristics . AccordiIn this work, a high-precision, low time cost reconstruction method of breast tissue acoustic attenuation was proposed, in which the time-reversal reconstruction method and the ray acoustic method were used to reconstruct sound speed and acoustic attenuation, respectively. This method is designed for the application of the CMUT ring array in breast ultrasound computed tomography (CT) in order to realize rapid and high-resolution imaging of micro-lesions in early breast cancer, which has the advantages of high specificity and abundant information, because it is based on the propagation law of ultrasound in realistic breast tissue. First, the wave acoustic is the exact solution to a two-dimensional wave equation. Therefore, it can significantly improve the image resolution and realize accurate detection of small lesions by establishing an accurate ultrasound propagation to reconstruct the sound speed distribution of breast tissue. Second, acoustic attenuation is also an important acoustic characteristic to quantify structural characteristics of different breast tissues, which changes more with the tissue type and can provide enhanced contrast for different types of tissues. For these reasons, this paper focused on the reconstruction method of the breast attenuation coefficient. In addition, projection data required by the two methods can be obtained from the same received signals, which not only ensures the accuracy of image reconstruction but also improves the computational efficiency. It provides the possibility to accelerate the clinical application of breast USCT systems. In conclusion, the research results in this paper lay a good theoretical and practical foundation for the realization of a new generation of breast ultrasound tomography systems in the future.


Although non-surgical treatment is effective for mild anal stenosis, surgical reconstruction is unavoidable for moderate to severe anal stenosis that causes distressing, severe anal pain, and inability to defecate. The problem in anal stenosis, unlike anal fissure, is that the skin does not stretch as a result of chronic fibrosis due to surgery. Therefore, the application of lateral internal sphincterotomy does not provide satisfactory results in the treatment of anal stenosis. Surgical treatment methods are based on the use of flaps of different shapes and sizes to reconstruct the anal caliber and flexibility. This article aims to summarize most-used surgical techniques for anal stenosis regarding functional and surgical outcomes.Anal stenosis, which develops as a result of aggressive excisional hemorrhoidectomy, especially with the stoutly use of advanced technologies (LigaSure Anal stenosis (AS) is defined as anatomical or functional narrowing of the anal canal, which can result from inflammatory bowel diseases, radiation therapy, congenital malformations, or excisional hemorrhoidectomy ,2. The aThe incidence of AS is reported to be as high as 5%, and patients usually present with burdensome symptoms such as severe constipation, outlet obstruction, and anal pain, which cannot be alleviated with stool softeners or dietary changes ,5,6. TheMilsom and Mazier described a classification system for the postsurgical AS that defines the treatment options based on the severity and the level of the stricture  7]. Non. Non7]. This article aims to review the operative treatment methods regarding functional results, postoperative care, and complications.Several flap techniques have been described for the treatment of AS, and they can mainly be classified as advancement, island (adjacent tissue transfer), or rotational flaps  Table 2Table 2. On the other hand, there is significant heterogeneity in the reported studies in terms of sample sizes (ranging from 4 to 149 patients), subjective assessment of functional outcomes (good-fair-poor) without the use of standardized scoring systems, and the evaluation of healing ,16,17,18a. Mucosal advancement flapThe mucosal advancement flap is mainly preferred for the treatment of mid-level AS. Good functional outcomes have been reported by a couple of studies that include different samples sizes ,19. RakhTechnical notes of Mucosal advancement flap:The technique starts with the excision of the scar tissue; then, a transverse incision is made proximally to the dentate line. The rectal mucosa is dissected to the level of submucosa and advanced to the anal canal to cover the excised stricture area. The exterior wound is preferred to be left open to minimize the ectropion formation . b. House flapThe house flap is recommended if the stenosis extends from the dentate line to the perianal skin. The creation of a wide-based flap increases the anal canal diameter along its length and allows primary closure of the donor site . Alver eTechnical notes of House flap:The patient is placed in the prone jack-knife position. The longitudinal incision is made from the dentate line to the end of the stenosis. Then the flap is designed as in the house shape, with the length of the “walls” of the flap corresponding to the length of the incision and the “roof” of the flap reaching the healthy perianal skin . The flac. Diamond flapThe diamond flap was first described by Caplin and Kodner in 1986 and has been performed for the treatment of moderate and severe AS . AlthougTechnical notes of Diamond flap:The patient is placed in the prone jack-knife position. The incision is made on the scar tissue longitudinally until it reaches the dentate line. The anal caliber is recommended to be checked during this step, and the external sphincter should be spared . The diad. Y-V flap/V-Y flapThe Y-V advancement flap is performed for low and localized strictures below the dentate line, whereas the V-Y flap is used for mild to severe stricture at the dentate line . Maria eTechnical notes of Y-V flap/V-Y flap:Initially, the vertical limb of the Y is performed to the area of stricture. The incision is extended to the perianal skin in two directions creating a V shape. Then, the tip of the V is advanced to the vertical limb of the Y incision. It can also be done in either a lateral position or just in the posterior midline. The main disadvantage regarding this technique is the tip of the V flap being prone to ischemic necrosis .For the V-Y advancement flap, the first few steps are the same as the Y-V flap, but in this procedure, the wider base of the triangular Y flap is sutured to the dentate line. Then the perianal skin is approximated with sutures longitudinally behind the V shape to form the Y shape .a. Rhomboid flap/Modified rhomboid flapThe rhomboid flap has been modified in terms of the flap size to be adjusted to each patient. Sloane et al. observed good functional results in a case series including nine patients, eight of whom underwent bilateral rhomboid flap with complete resolution of symptoms . The modTechnical notes of Rhomboid flap/Modified rhomboid flap:The size of the rhomboid flap can vary between 8 to 9 cm in length and 5 cm in width at its largest point. A minimal left/right internal sphincterotomy can be performed by paying careful attention to the external sphincter. Then, the flap is relocated in the anal canal and fixed with a single-layer suture of absorbable stitches to the distal rectum. The skin sutures should be adequately spaced to avoid excessive tension with subsequent ischemia .a. U-flapThe U-flap technique is mainly used for the treatment of AS with mucosal ectropion. The disadvantage of this technique is that the donor site is left open . Pearl eTechnical notes of U-flap:The procedure starts with the excision of the ectropion; then, a U-shaped incision is made at the adjacent perianal skin. The U flap is advanced into the anal canal to cover the wide defect resulting from the excised area of ectropion.b. Rotational S-plastyRotational S-plasty was first described by Ferguson in 1959 for the repair of the whitehead deformity of the anus . Corman Technical notes of Rotational S-plasty:The technique starts with outlining the semicircular incision in the perianal skin, with a length of 12 to 13 cm. The base of the incision should not be shorter than its length. Then skin incision is done to the layer of subcutaneous fat lobules to preserve the blood supply of the skin flaps. The flap is then rotated and fixed to the mucosa by interrupted sutures .Patients are usually discharged on postoperative day 1, with recommendations of daily sitz baths or showers for comfort and hygiene. Prophylactic antibiotics with metronidazole and ciprofloxacin or cephalosporins can be continued in the postoperative setting. The postoperative complications encountered commonly are urinary retention, wound dehiscence, wound infection, flap ischemia, and bleeding ,19,20,27The AS due to overzealous hemorrhoidectomy is an entirely preventable disease when performed under skilled and experienced hands . With beNevertheless, anoplasty techniques should be in the armamentarium of colorectal surgeons. The basis of these techniques includes excision or incision of the scar tissue, preparation of the flap with careful attention to the vascular supply, advancement of the flap, and fixating the flap without tension into the anal canal. Following these steps carefully would result in a significant decrease in anoplasty complications.As for the better technique regarding functional outcomes, we need more high-quality studies objectively evaluating patients’ quality of life and functional outcomes using standardized scoring systems and questionnaires.


Vehicle parameters are essential for dynamic analysis and control systems. One problem of the current estimation algorithm for vehicles’ parameters is that: real-time estimation methods only identify parts of vehicle parameters, whereas other parameters such as suspension damping coefficients and suspension and tire stiffnesses are assumed to be known in advance by means of an inertial parameter measurement device (IPMD). In this study, a fusion algorithm is proposed for identifying comprehensive vehicle parameters without the help of an IPMD, and vehicle parameters are divided into time-independent parameters (TIPs) and time-dependent parameters (TDPs) based on whether they change over time. TIPs are identified by a hybrid-mass state-variable (HMSV). A dual unscented Kalman filter (DUKF) is applied to update both TDPs and online states. The experiment is conducted on a real two-axle vehicle and the test data are used to estimate both TIPs and TDPs to validate the accuracy of the proposed algorithm. Numerical simulations are performed to further investigate the algorithm’s performance in terms of sprung mass variation, model error because of linearization and various road conditions. The results from both the experiment and simulation show that the proposed algorithm can estimate TIPs as well as update TDPs and online states with high accuracy and quick convergence, and no requirement of road information. Parameters are very important for dynamic analysis and control systems , as the An inertial parameter measurement device (IPMD) is a highly specialized test device for the measurement of vehicle TIPs, and thus is expensive . GeneralRelatively, TDPs’ estimation is more challenging as an online process is necessary. For example, although the mass and CG can be calculated using a static weighing scale, the online information of the vehicle mass is hard to know due to pick-ups or drop-offs during a trip and dynamic behaviors in motion. Rozyn and Zhang  suggesteReal-time estimation methods for some of the vehicle parameters have been suggested by numerous studies. Recursive least square (RLS) is a popular one for vehicle mass, which utilizes maximum likelihood theory ,11,12,13The vehicle parameter estimation methodologies can also be classified based on the vehicle models used: longitudinal, yaw, roll and bounce. The most prevalent methods in preview studies are based on the longitudinal one ,12,13,28Taking into consideration all the previous ideas, the primary objective of this study is to propose a comprehensive algorithm estimating TIPs as well as updating TDPs and online states with high accuracy and quick convergence. The contributions that clearly distinguish our endeavor from the aforementioned literature are that vehicle parameters are properly divided into TIPs and TDPs according to the requirement for updates, and consequently, different methods are formulated. TIPs can be determined offline based on the identification of modal parameters, while TDPs can be estimated online based on a real-time dual unscented Kalman filter (DUKF).The outline of the paper is as follows. A full vehicle model comprising two axles is illustrated in T” denotes the transposition of a vector or matrix, “diag” stands for diagonal matrix and the matrices The seven DOF vehicle model can be described by the following dynamic equationIn this section, the time-independent parameters (TIPs), listed in The basic concept of HMSV is identifying parameters through modal parameters, and thus the state-variable (SV) method is embedded to determine the modal parameters, firstly.Introducing state vector During the free decay response, the road input is e models , therefoN is the column number of Solving the eigenvalue problem of the transition matrix The matrix The state matrix e system , formingBoth Combining Equation (28) and Equation (29), there isAs the additional mass and position can be measured, In this section, the estimation process for TDPs and states using a DUKF method are formulated in detail. For a changing loading condition, all TDPs—The additional mass o and added mass, respectively. As As shown in Using the parallel-axis theorem, the new MIs can be calculated asa and b asSubstituting Equation (31) and The structure of the DUKF is detailed herein based on the system model formulated in The system equation for the states UKF is: of TDPs . The staIn this way, the road profile inputs d,rp,rd) . The outUT is a method for calculating the statistics of a random variable that undergoes a nonlinear transformation, which is detailed in A comprehensive algorithm is proposed to estimate TIPs as well as update TDPs and online states. A flowchart of the proposed algorithm is shown in A stage-drop experiment by a real vehicle was performed, and the proposed algorithm, illustrated in An experiment was performed on a two-axle vehicle equipped with a National Instruments Data Acquisition, enabling the synchronization and the evaluation of the logged data. There are four accelerometers and four linear variable differential transformer (LVDT) sensors used to provide data in the tests. The accelerometers are PCB PIEZOTRONICS’s 356A17 model, providing accurate measurements of three-axis accelerations with a resolution of 0.1 mg. In this work, only the vertical acceleration is taken into consideration. Four accelerometers are mounted on the chassis near four springs. Four LVDT sensors are mounted at each suspension to collect the dynamic deflections. The resolution of LVDT is about 0.1 um. One each of the mounted accelerometers and LVDTs are shown in The free-decay tests are dividing into two groups, with or without loading. Each group of tests includes a bounce test, pitch test and roll test of the vehicle. In the bounce test, four wheels of the vehicle are dropped simultaneously off stages with the same height. In the pitch test, the front or rear wheels are dropped off stages to carry out the pitch mode. Similarly, in the roll test, the left or right wheels are dropped off stages to carry out the roll mode.The wheel distance These determinable distances are listed in 2 and 2381 kg·m2, respectively. The estimated Based on above test data, TIPs can be estimated by the HMSV part, as are listed in In this section, further studies of the proposed algorithm are analyzed in terms of their ability to recognize the change of TDPs during a trip, the effect of nonlinear suspension properties and the performance on various road conditions, respectively. The simulations are implemented based on the vehicle model in A simulation is performed for the shedding load at 4 s during the trip, with a driving speed 40 km/h on a rough road defined as road class B according to ISO 8608. Before shedding of the load happens, the load mass is 300 kg and corresponding Comparisons of the The dynamic deflections for the four suspensions can be estimated by DUKF, and their values in the mass change scenario are illustrated in The suspension velocity can be estimated by the states UKF of the DUKF part in Tire deflection can also be estimated by the DUKF part without road information. The PSDs of tire deflection for the simulation and estimation are shown in The vehicle model given in essed as :(42)fi={RE) between the estimation and simulation values can be expressed asIn the simulations, the nonlinear parts of the suspension—RE between the estimation and simulation represents the accuracy of the proposed estimation algorithm, and the maximum REs of the TDPs are illustrated in RE (below 1%), whereas larger nonlinear damping causes higher RE values for TDPs. This means that disregard for nonlinear damping rather than nonlinear stiffness in the estimation process would affect the accuracy of TDPs. The reason could be that suspension deflections can be determined directly by the measured compressions, but the suspension velocity cannot. Accordingly, the incorrect stiffness value can be partly improved by the accurate suspension deflections with the help of the DUKF, whereas both the suspension velocity and the damping values are not accurate, which would lead to a large error eventually.The RE values are calculated based on the simulation and estimation results, and the maximum REs are illustrated in REs of below 5% until road roughness level F. Even though the maximum REs of REs of RE is below 2%. REs of below 2% for road roughness level F and speed bump height 0.07 m, under 40 km/h.In order to study the performance of the proposed estimation method under various road conditions, the simulations are implemented on various road roughness levels (according to ISO 8608) and speed bump heights. After that, the estimation process is performed based on the simulated results. A driving speed of 40 km/h and sprung mass of 2000 kg are considered for all cases. The  40 km/h . For theThe feasibility of the proposed algorithm from the implementation and computational point in practice is a very important question, and it is necessary to be studied. Therefore, we have illustrated a pitch velocity with real data in a simulation and estimated the results using the DUKF in For the 10 s simulation, the estimation of the DUKF uses 10.083 s to finish the estimation. It means the DUKF has a high possibility of updating TDPs online in practice. However, for the same simulation, the DEKF costs 2499.167 s. The most time-consuming process is the derivation of Jacobian matrices (2490.985 s) as there are fifteen variants in our state vector (Equation (36)), three variants in our parameter vector (Equation (38)) and twelve variants in our output vector (Equation (39)).Identification of vehicle parameters is essential for dynamic analysis and control systems. This study is aimed to propose a fusion algorithm for identifying comprehensive vehicle parameters without the help of an inertial parameter measurement device (IPMD). This paper divides the parameters of the vehicle into time-independent parameters (TIPs) and time-dependent parameters (TDPs) based on whether or not they change over time. The novelty of this paper is providing a comprehensive algorithm to estimate TIPs as well as update TDPs and online states for vehicle. TIPs were identified firstly by means of a hybrid-mass state-variable (HMSV) method. With the estimated values of TIPs, a dual unscented Kalman filter (DUKF), consisting of two parallel layers running simultaneously, was constructed to estimate both TDPs and online states. Experiments were conducted to estimate both TIPs and TDPs and so as to validate the accuracy of proposed algorithm. Numerical simulations were performed to further investigate the DUKF’s performance in terms of sprung mass variation, model error during linearizing and various road conditions. The results from both the experiment and the simulation showed that the proposed algorithm could estimate TIPs as well as update TDPs and online states with high accuracy and no requirement of the road information.With the proposed method, vehicle parameters can be identified separately and accurately. TIPs can be identified offline and stored for further use, while only TDPs are updated online, which improves the efficiency of estimation. In addition, it worth noting that by including the relationship between dynamic states and compression, the accuracy of the proposed method is quite high except for under significant dynamics caused by very bad road conditions, such as Class G roads or high bumps. We are now interested in extending the method for other mechanical systems in the future.


Environment perception is one of the major challenges in the vehicle industry nowadays, as acknowledging the intentions of the surrounding traffic participants can profoundly decrease the occurrence of accidents. Consequently, this paper focuses on comparing different motion models, acknowledging their role in the performance of maneuver classification. In particular, this paper proposes utilizing the Interacting Multiple Model framework complemented with constrained Kalman filtering in this domain that enables the comparisons of the different motions models’ accuracy. The performance of the proposed method with different motion models is thoroughly evaluated in a simulation environment, including an observer and observed vehicle. Environment perception is vital for safe functionality as the decision-making layer relies solely on its awareness of the given traffic scenario. Based on the current global trend, the number of autonomous vehicles is expected to increase, requiring solutions for new types of problems ,2. At prIn the case of vehicle tracking, the next maneuver of the tracked object is unknown; therefore, it cannot be decided in advance which motion model should be used during the estimation, despite that the performance of the estimators relies highly on it . Motion The performance of the Kalman filter can be further increased by using state constraints. For example, suppose any boundaries limit the desired safe states. In that case, those limits can be inserted in the filtering process as state constraints and improve its performance with this additional information .Kalman filter can handle state-space representations where both the measurement and the transition equations are linear with Gaussian noise. Vehicle tracking tasks can also be approached by Particle Filters (PF) , which iEven though a significant number of Kalman Filter-based methods can be found that use the pre-fit residual, only a few apply the post-fit residual. Ormsby et al. presented a solution, where they combined the traditional pre-fit and the post-fit residual, which serves as a solution for other Multiple Model methods, like Multiple Model Adaptive Estimator (MMAE) . HendersThis work examines and compares four motion models , considering a maneuver classification method using constrained Kalman filtering with multi-model estimation. The measurements come from radar and camera sources, and the maneuvers of a road vehicle are detected and classified using various complexity of motion models. Later, the models are evaluated and compared based on their performance. The constrained filters are arranged in the structure of the interacting multiple model estimator. Constraints customize each filter to match a specific type of maneuver. The quality of a filter is determined by examining the post-fit residual.The current study only uses linear constraints, which enables the utilization of the Kalman method. Therefore, the particle filtering approach is not necessary. On the other hand, the primary purpose, to compare the motion models, gives the same problem for all filtering paradigms.The paper is structured as follows. k:k:f and the measurement prediction h.In this study, multiple motion models are used for performance comparison purposes. Therefore, the considered system is described in double measure concerning the motion model; thus, the system can be described by a linear discrete-time dynamic model or a nonlinear model . The desKalman Filter, which is the base of this study, is a linear recursive estimator . For nonThe essential concept of the Kalman Filter is the following: a posteriori state estimate and error covariance are given by (12) and (13) For the Extended Kalman Filter (7) and (9) should be replaced withIn  and (8),The estimation quality is defined by a zero-mean PDF, using the pre-fit residual and its covariance:The estimation quality can also be defined with the help of the post-fit residual and its covariance:The Kalman filtering method is one of the most acknowledged filtering approaches; however, occasionally, it is not robust enough . In diffLinear equality constraints are formulated as follows:W is a positive definite symmetric weighting matrix, which is chosen as One of the solutions to the problem is the estimation projection . It inveD and d corresponding to the active constraints are chosen if x violates those; thus, a newly formulated constraint matrix and vector are created, with which  approach helps to reduce the uncertainties of the model, which assumes that the system behaves according to one of a finite number of models . The funEach model calculates its likelihood based on its constrained post-fit residual and the corresponding covariance designed using –24) in  in 24) iThe zero-mean PDF is defined with the help of . In the Constant Velocity (CV) and Constant Acceleration (CA) models, which are linear models, and Constant Turn Rate and Velocity (CTRV) and Constant Turn Rate and Acceleration (CTRA), which are curvilinear models (see Vehicle tracking must provide a decent position estimation. The two assets of the motion models predict the vehicle’s future position and describe the dynamic behavior . The perdels see .Constant Velocity (CV) and Constant Acceleration (CA) models. Linear models have the benefit of ensuring a great state probability distribution, yet both of these models presume straight motions only; thus, the state vectors are as follows:a can be derived from the velocity v, of which lateral and longitudinal components are calculated using the heading angle Constant Turn Rate and Velocity (CTRV) and Constant Turn Rate and Acceleration (CTRA) are on a level above, which can take into account the rotations. The state vectors are as follows:The lowest level motion models based on their complexities are Extended Kalman Filter (EKF) is used for that objective.However, for the utilization of these models, due to their nonlinearity, a filter is needed, which can manage it. Therefore, in this study, the previously mentioned This section presents the case study of the maneuver classification method using constrained Kalman filtering and IMM. The study is implemented in Simulink, using Automated Driving Toolbox provided by Matlab. In the scenario, two actors take place see . The obsv, and distance r between the two actors. The state space is represented in various forms based on the used motion model. Four types of motion models are used and compared in this study: the previously mentioned CV, CA, CTRV, and CTRA. The state-space representations are described in ; th; thγ, veThe yaw rate is derived from camera information, which allows detecting lane line as a polynomial. Camera measures the curvature derivative v is the doppler velocity and x is the longitudinal component of the distance measurement.Yaw rate F and matrices H are the following, where For each motion model, position error and maneuver probabilities are calculated. The maneuver probabilities are collected using IMM, which allows running the corresponding filters parallel, where each filter exemplifies a constrained specified maneuver. The filters are implemented in Simulink. The state transition matrices F and matrix H. Furthermore, heading angle a are not measured, only predicted; thus, ignored likewise in matrix H.The yaw rate F and measurement H matrices for the CTRV model areThe state transition F and measurement H matrices for the CTRA model areThe state transition a is ignored likewise in the case of linear models. The noise for the motion model is a discrete white noise, which is denoted by covariance Q:T is the sampling interval.Curvilinear motion models  allow yaw rate and require nonlinear filters; therefore, Extended Kalman Filter is used. Thus, linearization is mandatory, which is described above. The heading angle Three lateral  and fourFour distinctive longitudinal maneuvers are introduced in the study based on the distance and velocity difference as follows:Velocity and distance constraints are applied in various longitudinal maneuvers. Losing distance occurs when the observer is faster with at least 1 The longitudinal constraints are implemented as follows :The initial velocity of the observed vehicle is 30 Finding the correct parameters for the transition matrix always represents a significant concern. Consequently, trial and error based heuristic searches are conducted to capture the proper parameters for our research.Losing distance corresponding to the first row and column corresponds to a gaining distance maneuver associated with the second, following the distance keeping prerogative. The last row and column are responsible for collision warnings. The probabilities of the observed maneuvers using the CTRA motion model can be seen in The accuracy of the model prediction is computed as follows. The most probable model for each motion model is considered the estimated maneuver at each timestep. These values, which are weighted by the mode probability, are compared to the predefined maneuvers—described in The position error of the unconstrained filters using a specific motion model is calculated in the Euclidean space and presented in The unconstrained estimators’ root mean square error (RMSE) is applied on both position components and presented in The two curvilinear motion models overcome the nonlinear models. CTRA and CTRV models present the best estimation with approximately 0.5 m error in the X and Y direction. In contrast, the estimation of the CV model comprises 1.5 m error. Even though the curvilinear motion models return with the best estimate, thus the lowest error, it is perceivable in This paper presents a scenario-independent maneuver classification method, and its main purpose is to evaluate four different motion models in the given framework. The measurement and the state vectors must match, while the constraints must be defined separately. The presented algorithm utilizes the post-fit residual that profoundly enhances the accuracy of maneuver prediction. It is also combined with the IMM framework that enables the evaluation and comparison of the different motion models in a parallel manner. The algorithm uses constrained filters in the IMM structure and detects various maneuvers of an observed vehicle. The results of the maneuver classification are examined and evaluated based on four different motion models. It highlights the idea that from the aspect of the RMSE it is crucial to use the suitable motion model as the curvilinear models provide a significantly better position estimation than the linear. However, it is comprehensible that there is a modest difference between the models when constraints are applied as they alone reduce model uncertainty, as mentioned earlier.A flexible solution is implemented; thus, the algorithm can be efficiently extended with new maneuvers. The IMM can face problems when the dimension of the various state spaces are not identical. In this study, a dimension extension method is introduced, where the state vector is extended to the same dimension with zero value. An other solution is mixing different dimension state vectors; thus, a more flexible system is implemented . With no