Lophosteus superbus, which are argued here to represent an early form of the osteichthyan inner dental arcade, display a previously unknown and presumably primitive mode of tooth shedding by basal hard tissue resorption. They carry regularly spaced, recumbent, gently recurved teeth arranged in transverse tooth files that diverge towards the lingual margin of the cushion. Three-dimensional reconstruction from propagation phase-contrast synchrotron microtomography (PPC-SRµCT) reveals remnants of the first-generation teeth embedded in the basal plate, a feature never previously observed in any taxon. These teeth were shed by semi-basal resorption with the periphery of their bases retained as dentine rings. The rings are highly overlapped, which evidences tooth shedding prior to adding the next first-generation tooth at the growing edge of the plate. The first generation of teeth is thus diachronous. Successor teeth at the same sites underwent cyclical replacing and shedding through basal resorption, producing stacks of buried resorption surfaces separated by bone of attachment. The number and spatial arrangement of resorption surfaces elucidates that basal resorption of replacement teeth had taken place at the older tooth sites before the addition of the youngest first-generation teeth at the lingual margin. Thus, the replacement tooth buds cannot have been generated by a single permanent dental lamina at the lingual edge of the tooth cushion, but must have arisen either from successional dental laminae associated with the individual predecessor teeth, or directly from the dental epithelium of these teeth. The virtual histological dissection of these Late Silurian microfossils broadens our understanding of the development of the gnathostome dental systems and the acquisition of the osteichthyan-type of tooth replacement.The numerous cushion-shaped tooth-bearing plates attributed to the stem group osteichthyan  However, teeth and tooth-bearing bones are only known from the type locality material of L. superbus, while the other new species are mainly based on scales, spines and head plates [Lophosteus has continued to attract the interest of researchers to the present day, partly because of the superb histological preservation of the Ohesaare material, and partly because of its distinctive character complement that suggests membership of the osteichthyan stem group. studied –4. Lophoet al. [Andreolepis and Lophosteus, and interpreted them as potential members of this stem group. In 2010, Friedman & Brazeau [Lophosteus, interpreted by Friedman and Brazeau as a possible (but not definite) stem osteichthyan, is in fact the only known member of the osteichthyan stem group.For many decades, the earliest and most basal osteichthyans (bony fishes plus tetrapods) were interpreted as either actinopterygians (ray-finned fishes) or sarcopterygians (lobe-finned fishes), leaving the osteichthyan stem group vacant . Howeveret al.  describe Brazeau  establis Brazeau  revised Lophosteus as an osteichthyan rather than an acanthodian on the basis of detached teeth that showed traces of resorption and resembled crown osteichthyan teeth in the shape of their pulp cavities and arrangement of dentine tubules [Besides scales and dermal plates, another common type of detached material that carries phylogenetic significance is dental elements. Osteichthyans have a unique mode of tooth replacement involving shedding through basal resorption of the dental tissues . Gross i tubules ,3,9. How tubules , probablAndreolepis [Andreolepis do not stand in longitudinal rows, but instead form a tooth field with an undulating labial boundary. They are most probably arranged in alternate transverse files, following the pattern of a more labial set of tooth-like non-shedding odontodes, which seem to have been used for food capture prior to the development of the shedding dentition. A well-organized linear longitudinal tooth row, with repeated basal resorption of the shedding teeth, is classically regarded as unique to osteichthyans. The dental development of Andreolepis suggests that the shedding cycle evolved before the emergence of the linear tooth row [The study of early vertebrate dental systems has recently been revolutionized by the application of propagation phase-contrast synchrotron microtomography (PPC-SRµCT), which allows the internal architecture of dental elements, including features such as buried resorption-overgrowth surfaces, to be visualized in three dimensions with micrometre-scale resolution without damaging the specimens ,11. Usinreolepis . The sheooth row .Lophosteus superbus, which has been greatly expanded by a recent collecting programme led by H.B. includes marginal jawbones [Andreolepis as well [Entelognathus from the Silurian of Yunnan, China, which combine an overall placoderm-like morphology with marginal jawbones similar to those of osteichthyans [Entelognathus and a second recently discovered form from the Silurian of Yunnan, Qilinyu, which both have maxilla, premaxilla and dentary, have no inner dental arcade at all [Lophosteus and Andreolepis, referred to below as ‘tooth cushions’, are certainly internal to the margins of the jaws and could thus, in principle, represent either the inner dental arcade, that is to say the coronoid-dermopalatine series, or still more internal elements such as branchial dental plates, or both. We return to this question in the Discussion, where we argue that they are more likely to belong to the inner dental arcade.The Ohesaare material of jawbones  and numejawbones . Similar as well ,13. The chthyans . Traditie at all . This suLophosteus by PPC-SRμCT at submicrometre resolution. As already illustrated in Andreolepis [We present here the first investigation of the tooth cushions of reolepis . This grreolepis , which a2.Lophosteus, Ohesaare cliff, in Saaremaa Island, Estonia. Acetic acid dissolution and extraction of the microremains were, respectively, carried out at the Department of Earth Sciences of Lund University and the Department of Organismal Biology of Uppsala University, Sweden. All specimens are registered to the Geological Institute, Tallinn, Estonia under the designation GIT 760.Fallen blocks of limestone totalling several hundred kilograms were collected from the type locality of Lophosteus on the basis of a characteristic bone histology with very large osteocyte lacunae that is shared with scales, spines and bones of Lophosteus from the same locality [Lophosteus without difficulty.More than 130 tooth cushions were found among the microremains, displaying variation in size and morphology. The specimens can be confidently assigned to locality ,16. The locality , which cLophosteus tooth cushions show evidence of transportation and abrasion. Most tooth cusps were broken, leaving a cluster of rings of the dentinal bases, and thus the cushions acquired a honeycomb appearance . But this has no influence on the excellent preservation of histology, which yields a wealth of details and allows the growth history to be reconstructed with confidence. Dentine and bone can easily be distinguished and there is no visible recrystallization of either tissue (figures 2j–8a and 11a). Vascular canals, osteocyte lacunae, dentine tubule and fibre traces are all clearly visible and show no evidence of distortion or enlargement by post-mortem erosion.Ohesaare cliff represents an open shoal environment with high energy , and man2.1.Selected specimens were photographed by dissection microscope each at 20–30 focus points. These separate frames were combined by the Auto-Blend Layers command of Photoshop to composite an image in which the whole specimen is in focus .2.2.Three specimens were imaged at beamline ID19 of the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, using propagation phase-contrast synchrotron radiation microtomography (PPC-SRµCT) adapted to fossil bone histology ,19 tabl.Table 1The scan that the three-dimensional virtual dissection figures –11 was bData for ontogenetic comparisons figures –6 are frThe virtual thin sections of the sample in the form of stacks of images were segmented into three-dimensional sub-volumes through the software VG Studio 2.2. Embedded subtle structures, such as the surfaces of resorption and dentine, were traced manually.3.Lophosteus has a complex growth mode that includes both the addition of new teeth to the ends of existing tooth files, thus creating new tooth sites, and the repeated shedding and replacement of the teeth at existing sites. In order to express this organization unambiguously in writing, the following terminology is used throughout: tooth file—a linear arrangement of teeth, oriented labio-lingually with new teeth added at the lingual margin; first-generation tooth—the first tooth to grow at any tooth site; pioneer teeth—the earliest first-generation teeth; previous, next—terms denoting order of deposition of first-generation teeth within a file; tooth site—a location initially established by a first-generation tooth, later maintained by a replacement sequence of successor teeth; predecessor, successor—terms denoting time sequence of teeth within a replacement sequence at a single tooth site.The tooth cushion dentition of 3.1.ba, bone of attachment;bb, bony base;bc, radial canal of bony base;bo, basal canal opening;den, dentine ;gc, growth center of bony base;gl, growth line;lr, labial rim;ol, osteocyte lacunae;pf, pulp cavity of the first-generation tooth;pn, pulpal neck linking the pulp cavities of the first-generation and the functional replacement teeth;pr, pulp cavity of the replacement tooth;rc, root canal of the first-generation tooth;rl, resorption line;rv, ascending vessel radiating from pulp cavity ;tr, tooth of replacement (the numbers of pf and tr indicate the corresponding tooth sites between first-generation and replacement teeth).3.2. first-generation teeth first-generation pulp cavities replacement  teeth replacement teeth pulp cavities semi-basal resorption surfaces basal resorption surfaces radial vessels of pulp cavities radial canals of bony base osteocyte lacunae4.4.1.i–l and 2b,d), is believed to be the growth centre of the bony plate. The apex is not located at the centre of the tooth cushion, which grows faster in the (assumed) lingual direction. The labial edge of the tooth cushion is especially thin, free of vascular openings and tooth covering . It seems the tooth cushion is in contact with another bone  labially by a rim of basal bone, and the growth of bone in this direction is limited. The majority of the specimens are ovoid in shape, with the labial rim at the narrow end and the thicker vascularized edges at the broad end , but there are exceptions that are oriented the other way around . Sometimes the narrow end is pointed, or the labial rim is straightened ; in some specimens, all the edges are straightened, making the tooth cushion approximately rhomboidal . Rarely, the tooth cushions may be further elongated into a rectangular shape (c). Most cushions are obviously (though not grossly) asymmetrical, but one specimen  is bilaterally symmetrical and could represent a symphysial plate.The apex of the tooth cushion, surrounded by appositional growth increments . The oldest tooth sites are aligned along the labial rim . If the labial rim is at the narrow end of the tooth cushion, the tooth files radiate lingually from there towards the thicker edges symmetrically (f); but the labial rim is more commonly at one side of the narrow end, and the tooth rows are arranged in an asymmetric pattern such that the direction of the median tooth file is not parallel to the long axis of the tooth cushion . Teeth are closely spaced and recurved towards the direction of addition . New tooth files may originate between the diverging original tooth files, about halfway towards the broad end of the tooth cushion. New teeth become larger and larger as well. The number of tooth sites varies greatly among specimens, but not necessarily depending on size. The largest specimens can carry about 14 rows and 120 functional teeth (b), but both the smallest (figures 1a and 2c) and medium-sized ones (figures 1c–h and 2a) can carry a wide range, between 40 and 60 teeth.Interestingly, the pioneer teeth are not situated above the growth centre of the bony plate . The multi-layered resorption features separating the tooth sets are the product of repeated tooth shedding and replacement at these sites.The general organization of the tooth cushion is that of a domed basal plate of bone, with a convex external surface and a concave internal surface, carrying on its external surface a tissue layer containing a complex array of multi-layered resorption features, sandwiched between two sets of teeth. The upper set comprises the functional teeth protruding from the external surface; the lower set consists of the retained bases of the first-generation teeth, lying directly on the bony base. Both sets contain the same number of tooth sites  are actually filled by stacks of the bone of attachment that surrounded preceding generations of shed teeth.The bony base contains numerous osteocyte lacunae , consistent with their probable derivation from the same odontogenic population of mesenchyme cells within the dental papilla [The teeth consist of orthodentine and lack enamel. The bone of attachment and dentine grade into each other in a transition zone without any sharp boundaries , where they are truncated obliquely. There are at least two more layers of these radial basal canals running parallel to the curvature of the bone, inside the bony base and between the bony base and the tooth division , with a scatter between these areas (i). We interpret them as housing the arteries and veins that supply the complex vascular system of the dental layer as well as the overlying soft tissue. A single pulp cavity (a tooth site) at the cushion margin can connect up to seven basal canals of the bony base by its root canals, and all the oval-shaped pulp cavities are elongated in the direction of the radial basal canals .The imprint of large vascular canals can be found on the internal surface radiating from the apex of the tooth cushion to the bone margin . Occasional vertical canals rising from the root canals show that they remained connected to the vasculature of the overlying soft tissue.The pulp cavities of functioning replacement teeth figures –6, where9a, 7a and 11a). However, the youngest generations of replacement teeth are formed in a substantially more lingual position than their predecessors (figures d–f), and show two separate sets of deep canals connecting to the first-generation pulp cavities of the two tooth sites (figures 7a and 10h). The replacement teeth at the youngest tooth sites may have one set of deep canals coming up through the marginal bone of the base plate , apart from the one arising out of the predecessor pulp cavity. In this instance, it appears that the site of the replacement tooth bud straddled the margin of the underlying base plate, such that it was able to attract vessels both from the predecessor pulp cavity and from the soft tissue bordering the base plate.Replacement teeth have a dual vascular supply with deep and superficial components. The deep component normally came up through the (now open-topped) pulp cavity of the predecessor tooth . The openings of these canals lie within the bone of attachment and form a ring round each standing tooth, which also characterizes the shedding teeth on the tooth cushion of Andreolepis, and the marginal jawbones of Lophosteus and Andreolepis [e–j). The few examples that were captured in this way presumably represent vessels that failed to initiate osteoclast activity. The openings are often shared by the radial vessels of neighbouring teeth. If the openings are covered by a new tooth of its own or adjacent tooth site, the radial canals will join to the bottom of the new pulp cavity . However, the few radial vessels belonging to the older generations of pulp cavities can still communicate with the soft tissue in places where there is no overgrowing of new teeth. The radial canals can also give off straight branches that connect down to the root canal network directly.In addition to these deep components, each replacement tooth has a ring of more superficial vessels, represented by radial canals emerging from a higher level of the pulp cavity, which in life connected to the vasculature of the thin soft tissue overlying the tooth cushion , the bases of their pulp cavities together with the dentine became embedded by the bone of attachment of the following generations of teeth. The pulp cavities of the next generations lay on the pre-existing ones, connecting to the vascular networks of the bony base through the old chambers. But as all the younger generations of teeth were shed basally, their pulp cavities were not preserved. After the replacement of several generations of teeth and the stacking of bone of attachment, a neck is formed linking the pulp cavities of the first generation and those of the functional teeth  does not coincide with the growth centre (the apex) of the bone, tooth addition correlates with the growth of the basal plate. Teeth are arranged so tightly that, in a radial row, a younger larger first-generation tooth overlaps the preceding tooth site for at least a quarter of the tooth length, and even overlaps on two preceding teeth. As a result, the preceding tooth has to be shed to make way for the next tooth, which allows the root canals of the new tooth to join those of the preceding tooth from above . It leaves the periphery of the tooth base that, before shedding, has probably been incorporated into the basal plate, embedded in the bony tissue to some extent, as well as overlapped by a newly added tooth of the adjacent row. The marginal first-generation teeth, the final tooth sites of the tooth files, also undergo semi-basal resorption.The overlapping relationship between the first-generation teeth shows that they are added sequentially towards the growing margin of the tooth cushion in an alternate pattern figures –11. Alth2In situ tooth replacement is thus required to produce new sharp teeth on the surface of the tooth cushion. This has apparently already happened to the oldest tooth sites before the addition of the last first-generation teeth to the bone margin, because the larger number of resorption surfaces at the labial tooth sites documents that they have been replaced more times . The addition of the replacement teeth follows the same sequence as the addition of the first-generation teeth, judging by the number of resorption surfaces beneath them. Thus, it seems that the replacement of each generation of teeth is a diachronous event that proceeds like a wave across the tooth cushion, starting at the labial margin; the functional dentition is at any one time composed of teeth of more than one generation, and the whole tooth field maintains functional teeth all the time.After the addition of the first-generation teeth is finished, the tooth cushion continues growing wider; however, the number of tooth sites does not increase.  figures j–6. Amonc). On top of the dentine ring the resorption surface takes the form of a circular platform that hardly extends out of the tooth into the surrounding bony tissue. Internally, it extends deeply into the base of the first-generation tooth (d). Hence the following generations of replacement teeth, along with their bone of attachment, can insert into the hollow, right at the same tooth site, and even the basal resorption surfaces of replacement teeth extend into the hollow too, like a funnel (figures f–j). But since the tooth cushion has grown wider and thicker, with a larger external surface, the replacement teeth do not overlap each other. The following generations of teeth even have to become larger and shift towards the lingual margin of the cushion in order to fill up the increasing space . No dentine remnant is found between these resorption surfaces, indicating that all the replacement teeth are shed completely by basal resorption. The resorption surface is centred on the predecessor tooth that was shed by the resorption event. The position, orientation and size of a resorption surface thus illuminates that of a shed tooth, and the stack of resorption surfaces reflects the track of the cyclical shedding. The position of the new tooth usually deviates from the resorption cup left by its predecessor, as it is larger and located more lingually . Because both the semi-basal and basal resorption surfaces are funnel-shaped, this lateral displacement prevents them from ‘stacking’ neatly; each new tooth will be raised up, because it straddles the rim of the underlying resorption pit, and its bone of attachment will thicken the bony plate. Accordingly, the basal resorption of the new tooth will partially encroach the resorption surfaces the tooth rests upon, the resorption surfaces at the next more lingual tooth site, and even the buried dentine rings of the first-generation teeth , producing a new wider resorption surface. The encroachment by later resorption events is most obvious at the lingual side of the resorption surfaces or dentine rings located at the lingual margin, as the marginal replacement teeth incline lingually and this inclination is increasing in their successors. The bone of attachment sandwiched by the resorption surfaces is thus thicker at the labial side, and consists of the tissue between tooth sites (c–f). It may imply that the developmental domain of tooth shedding of each tooth row is clearly demarcated.At least three or four resorption surfaces are stacked at each tooth site in the assumed lingual region of the thinner specimens figures a, 8–11 bth sites c–f. It m5.5.1.Amia [Eusthenopteron [Lophosteus have been identified in the past as branchial dental plates [Before examining the significance of the cushions and their dentition in detail, we need to consider their precise identification. In some extant actinopterygians such as Amia  the entinopteron , indicatl plates , but we Lophosteus material from Ohesaare comprises hundreds of specimens, all the non-marginal dental elements are tooth cushions of the type described here. There is no trace of large flat denticle-bearing bones, either entire or as fragments, or of any small elements that diverge from the stereotypic concavo-convex tooth cushion morphology. We conclude that the tooth cushions are the only dental elements in the oropharyngeal cavity of Lophosteus. The maxillate placoderms Entelognathus [Qilinyu [Lophosteus, it is unlikely that tooth cushions occupied all the areas covered by categories (i)–(iv) in crown osteichthyans, because they do not show a degree of morphological variation commensurate with this hypothesis.Even though the ognathus  and Qili[Qilinyu , which cLophosteus covered only part of the oropharyngeal cavity. But which part? Clues are provided by their morphology  end of the whorl, and post-functional teeth will be lost by basal resorption immediately before the resorption of the anterior end of the whorl itself [The teeth on the tooth cushion are not randomly distributed in an irregular tooth field, but neatly arranged in tooth files. Thus the tooth cushion could be described as a multi-file tooth whorl or tooth plate. On the tooth whorls lining the jaw or in the symphysis of acanthodians and early chondrichthyans, successive teeth of increasing size are added lingually ,38. The l itself ,44. Shedl itself . All theLophosteus, all the tooth sites are active throughout life. There is no post-functional position (away from the biting region) that the worn teeth can be moved to. Although continued growth is observed at the active margin of the tooth cushion even when the number of tooth sites does not increase any more, neither significant bone resorption or abrasion at the primary zone, nor movement of the functional sites associated with the remodelling of the basal plate is observed. The basal plate of the cushion is relatively static. Resorption only relates to particular teeth and the teeth can only be renewed via in situ replacement. Furthermore, the older tooth sites undergo more cycles of replacement than the younger ones . If the tooth buds of one generation are all generated by a single, lingually positioned dental lamina, a marginal functional tooth will block the addition of the next generation of teeth to the preceding tooth sites. This suggests that each tooth site has its own clock of replacement and the cyclic shedding is autonomous. In addition, there is no space for a proper dental lamina to situate deeply at the side of each tooth site, considering that the replacement teeth are added superficially, similar to those on the jawbone of Andreolepis [Lophosteus does not depend on a permanent dental lamina, and give further support to the emerging consensus that the permanent dental laminae of chondrichthyans and tetrapods are convergent [However, a single lingually positioned dental lamina of the kind seen in sharks cannot explain the tooth addition and replacement mechanism of the tooth cushion. On the tooth cushion of  figures –6, thus  figures e,f. If treolepis . The repreolepis –48. All nvergent ,49–51.Lophosteus distinctive relative to all other dental elements known so far is the combination of semi-basal and basal resorption. While the post-functional teeth of other tooth whorls or tooth plates are either shed or not, the first-generation teeth of Lophosteus tooth cushion are shed semi-basally. The resorption actually extends deep down to the vascularized base of the tooth, in order to allow the replacement teeth to insert into the ring of dentine remnant (figures What makes the tooth cushion of  figures  and 12. Lophosteus tooth cushion is reminiscent of the non-shedding first-generation odontodes on the marginal jawbone of Andreolepis [Lophosteus the first-generation teeth directly set up the shedding dentition in situ. Although the semi-basal resorption cannot remove the entire teeth, it is site-specific and initiated from inside. This is presumably because the odontoclasts, probably the only clast cells involved in the semi-basal resorption, differentiated within the pulp cavity of a tooth and only affected the dentine of this tooth. Semi-basal resorption might be an initial form of osteichthyan-type tooth resorption, and it may have evolved into a real basal resorption by recruiting osteoclasts to resorb the bone of attachment of the tooth, as displayed by the successive generations of replacement teeth on the tooth cushion of Lophosteus.The semi-basal shedding nature of the first-generation teeth of the reolepis . Howeverreolepis . The shereolepis , whereasAndreolepis and first-generation teeth on the tooth cushion of Lophosteus, both resemble the addition of teeth in non-shedding dentitions such as the jawbones of arthrodires and ischnacanthid acanthodians [Lophosteus provides a clue about the evolutionary relationship between non-shedding tooth addition and osteichthyan-type tooth replacement. Especially, it casts light on the origin and the development of the tooth fields internal to the marginal jawbones of osteichthyan fish.The pattern of addition of first-generation odontodes on the marginal jawbone of thodians , which m


One of the key technologies that lays behind the human–machine interaction and human motion diagnosis is the limbs motion tracking. To make the limbs tracking efficient, it must be able to estimate a precise and unambiguous position of each tracked human joint and resulting body part pose. In recent years, body pose estimation became very popular and broadly available for home users because of easy access to cheap tracking devices. Their robustness can be improved by different tracking modes data fusion. The paper defines the novel approach—orientation based data fusion—instead of dominating in literature position based approach, for two classes of tracking devices: depth sensors  and inertial measurement units (IMU). The detailed analysis of their working characteristics allowed to elaborate a new method that let fuse more precisely limbs orientation data from both devices and compensates their imprecisions. The paper presents the series of performed experiments that verified the method’s accuracy. This novel approach allowed to outperform the precision of position-based joints tracking, the methods dominating in the literature, of up to 18%. Human limbs motion tracking can be defined as a process of unambiguous limbs joints spatial positioning, devoid of significant delays. Nowadays, it might be exploited within several areas, such as entertainment issues, virtual environments interaction or medical rehabilitation treatment . HoweverSince 1973, when Gunnar Johanson invented his motion capture system , such teMicrosoft Kinect represents a broad group i.e. PrimeSense Carmine , ASUS Xtion  of mono-view markerless depth sensors that exploit structural light patterns to reconstruct the depth of the scene and track perceived objects, with special attention put to human limbs and body parts tracking . This group reveals similar constraints and limits that were usually compensated by sophisticated algorithms of other modes controllers  .An easy access to the motion capture has been additionally supplemented and magnified by the fact that inertial devices such as gyroscopes and accelerometers  have become an integral and mandatory part of current electronic devices. These units are built in almost every smartphone device and they are used in various applications like pedometers ,7, screeInertial measurement units (IMU) are also used as measuring devices in non-optical, inertial human limbs motion tracking systems i.e., XSense ,10. DespSpine joint position of the Kinect’s originated skeleton model. The data from the accelerometer, gyroscope and magnetometer were fused with Madgwick’s filter . Th. ThRMSE)r between the difference of r ratio has been presented. Based on the results presented in The overall error of both methods, for each test exercise, has been calculated as a mean of Equation  and exprEquation ). In thiTracked state joints. Moreover, even if the occlusion doesn’t occur, the estimation of angles between selected bones turns to be more stable in time than the estimation of joint positions. This means that the estimation of bone rotation is more reliable than joint position estimation. Furthermore, the bone rotation is the information available from both signal sources with minimal raw data processing, which has an impact on the quality of data used in the fusion.The authors presented a new, orientation-based method for skeleton joint positioning, which compensates devices’ imperfections and considers the context of the motion. It was tested on a set of right hand movements, which appeared to be demanding for measurement devices. Results were compared with those gathered from the position-based fusion method and the reference, professional, ground truth Vicon tracking system. Presented results prove that the newly elaborated, complex approach reduces joint position estimation error. The principle reason of such estimation improvement, identified by the authors, is related to the better stability of bone rotation estimation in reference to the position-based method, as well as the diminished inaccuracy of bone length measurements and the lack of the fixed skeleton model definition support. Moreover, the authors have found that the introduced complementary fusion of the signals, measured by both devices, reduces the influence of source signals’ imperfections on the final result. In the case of IMU devices, the information about their 3D space orientation  was the default and required less complex data processing. The estimation of the joints’ positions, based on IMU measurements, required additional measurement of the selected bone length and additional geometric transformations (geometric transformations required to estimate the joint position based on IMU measurement has been described in detail in ), which What differentiates the proposed method from the already known methods described in the literature is the fact that it takes into consideration characteristics of the classes of chosen measurement devices, and provides the complex compensation of detectable errors that exist in their data. It also allows for improving the quality of the source data before their fusion. It is important that many of the characteristics described in this article adaptively respect the context of the performed motion. As an example, the variable accuracy of the distance measured between Kinect and the user, or the human rotation angle relative to the surface of Kinect, has an impact on the stability and reliability of Kinect’s data.The goal of the conducted research was to find the method of human limbs motion tracking, which would take into consideration elaborated characteristics and would reduce joint position estimation error significantly. The proposed method, tested on the example of the upper limbs motion, has met this goal. The results obtained by the authors’ method have been compared with the results of the position-based data fusion method with the highest declared accuracy. Three parameters estimated by both methods have been compared: the elbow joint position error, the wrist joint position error and the elbow angle  motions  used to The results of the comparison of the elbow joint position estimation error are presented in the chart in Obtained results prove that the novel data fusion approach, based on skeletal bone rotations, might be considered as an improved alternative to the well-known, joint position-based methods.


In this article, we briefly describe the design, construction, and functional verification of a hybrid multichannel fiber-optic sensor system for basic vital sign monitoring. This sensor uses a novel non-invasive measurement probe based on the fiber Bragg grating (FBG). The probe is composed of two FBGs encapsulated inside a polydimethylsiloxane polymer (PDMS). The PDMS is non-reactive to human skin and resistant to electromagnetic waves, UV absorption, and radiation. We emphasize the construction of the probe to be specifically used for basic vital sign monitoring such as body temperature, respiratory rate and heart rate. The proposed sensor system can continuously process incoming signals from up to 128 individuals. We first present the overall design of this novel multichannel sensor and then elaborate on how it has the potential to simplify vital sign monitoring and consequently improve the comfort level of patients in long-term health care facilities, hospitals and clinics. The reference ECG signal was acquired with the use of standard gel electrodes fixed to the monitored person’s chest using a real-time monitoring system for ECG signals with virtual instrumentation. The outcomes of these experiments have unambiguously proved the functionality of the sensor system and will be used to inform our future research in this fast developing and emerging field. Current trends in the development of vital sign monitoring technologies demonstrate that the future points in the direction of the introduction of sophisticated diagnostic devices that integrate several diagnostic measures in one all-purpose instrument or probe.Here, we introduce the concept of a novel sensor system, which offers the potential of continuously monitoring the vital signs of up to 128 individuals by using a fiber optic probe. This patent-pending probe, which functions on the basis of the fiber Bragg grating, was designed, constructed, and validated by the authors in the Czech Republic. The advantage of the proposed multichannel fiber-optic sensor system is the possibility of monitoring patients in the harsh magnetic resonance (MR) environment .The authors have developed a measurement probe that allows for monitoring the mechanical vibrations of human body evoked by living activities: breathing and heart rate . The bodRecent years have witnessed a growing increase in the utilization of Optical Sensors (OS) for a variety of emerging biomedical applications ,3. A numTextiles can be used to encapsulate sensors and measure heartbeat and respiration rate simultaneously. Several techniques, such as wrap and weft knitting, weaving and stitching, can be used to embed the fiber sensing elements into textile fabrics ,21,31,32Our novel measurement probe (described below) allows measurement of body temperature in addition to other advantages offered by the sensors described in the above articles. Based on our comprehensive literature and patent search, we can safely claim that our presented solution is innovative.In general, there are three types of Optical Sensors: (1) non-invasive sensors, which come into direct contact with the human skin; (2) minimally-invasive sensors, which are used for measurements carried out in body cavities; and (3) invasive sensors, which are used for measurements made inside organs or in the bloodstream (intravascular). Desirable characteristic features of Optical Sensors include their independence from an active power supply and a high immunity to electromagnetic interference. Thanks to these attributes, Optical Sensors can be used with other electronic equipment without generating electric noise that may compromise the quality of vital sign monitoring and potentially lead into patient safety concerns. Optical Sensors are gaining more popularity due to their flexibility, improved functionality, and reliability. The very small dimensions of optical fibers allow them to be encapsulated inside very thin catheters and injection needles, thereby enabling localized and minimally-invasive monitoring. Biocompatibility is a very important consideration in the acquisition and evaluation of high quality data from sensors coming into contact with living tissue. As Optical Sensors are biocompatible and do not influence the patient’s body in any major way, they offer a great level of patient comfort during vital sign monitoring.The major aim of this article is to introduce our novel vital sign measurement probe  and its associated sensor system. In this limited space, we do not intend to compare our system with other existing sensors. The comprehensive characterization of our novel sensor system and its comparison with other existing sensors will be the focus of our future articles with detailed signal processing.The FBG is characterized by a periodic change of the refractive index in the fiber’s core . When weExternal effects like deformation or temperature influence the Bragg wavelength and the period of changes of the refractive index in a linear fashion, which translates into a linear shift in the Bragg wavelength. To describe the Bragg grating sensitivity in a quartz optical fiber, we use the normalized deformation coefficient (at constant temperature) as:.3 pm/°C .As FBGs are single-point sensors, with multiplexing techniques, we can easily connect them together and obtain a multi-point measurement probe. The most common methods are the wavelength-division multiplexing (WDM) and time-division multiplexing (TDM). The analysis of the capacity of these multiplexing methods is described in . The mosTo apply the wavelength-division multiplexing method, it is necessary to avoid the overlapping of neighboring spectrums. For this reason, each FBG probe is assigned a specific measurement window, whose size is given by a sensitivity coefficient as well as the expected maximal influence of the measured value.Our novel measurement probe is based on two FBGs encapsulated inside a polydimethylsiloxane (PDMS) polymer . As FBGsWe chose the PDMS polymer to increase the temperature sensitivity of our probe and ensure its non-reactivity to the human skin. The encapsulation of the measurement probe was realized by PDMS with the designation of Sylgard 184. Sylgard 184 is a two-component casting compound: the A component creates its own pre-polymer and the B component is a curing agent. Both components are mixed together according to a datasheet in a weight ratio of 10:1 (A:B). Bubbles and microbubbles that result from the combination of the pre-polymer and the curing agent can be removed using an ultrasonic bath. Homogeneity of the connection is realized using a laboratory shaker. The measurement probe contains two connectors of EURO 2000 type. The first connector is plugged into the measurement system or a preceding probe, and the second one is plugged into a succeeding probe.The multichannel hybrid fiber-optic sensor system  is basedReflected signals from each measurement channel are projected through the circulator into an optical spectrum analyzer. The signal is then processed in the Digital Signal Processing (DSP) Unit. The Electronic Control Unit controls the parameters of each individual optical unit such as the capacity of the light source, the switching speed of the optical switch and the sensitivity of the optical spectrum analyzer.n-th sensor, The experimental solution proposed in this article uses the fiber Bragg gratings encapsulated into PDMS polymer to monitor patient’s vital signs. Individual sensors are detected by one optical fiber. To distinguish individual readings from FBGs the wavelength division multiplexing method is used. Each FBG sensor is assigned a specific measurement window. The fiber Bragg gratings of individual sensors belonging to a specific type of spectral model  are giveMovements of the thoracic cavity (its expansion or contraction) depend on the way of breathing  and particularly on its capacity. Due to this fact, a series of measurements were carried out to set the input parameters  in a room with the temperature of 24 °C. The tested persons were between 20 and 45 years of age, their weight was between 55 and 115 kg and their height was between 155 and 192 cm. No significant differences were found in the quality of the received signal depending on the age, weight, and height. The experiments were carried out in a lab environment and they were discussed with the senior doctor of the long-term health care department of the University Hospital in Brno, Czech Republic. The vital sign monitoring probe was placed around the pulmonic area on the chest and fixed into the position by a contact elastic strap . The subf and produce the rates in cycles or respirations per minute (rpm) by using Equation (6).i-th maximum (of breathing and pulse progress), f is a dominant frequency obtained using the Fourier transform.Two approaches were used to evaluate the heart and respiratory rates. The first approach allows for the determination of these rates in the time domain by identifying the periodic cycles in the form of local maximum Equation (5). Whereas in the second approach, the Fourier transform is applied on obtained measurements to calculate the dominant frequency The measurements are based on monitoring the movements of the thoracic cavity of a subject while breathing. The mechanical strain is transferred to the FBG by a thoracic elastic strap. The body temperature as well as respiratory and heart rates were obtained by the spectral evaluation of the measured signals.An application software was developed in Matlab  to perform a variety of tasks including: (1) calculation of the breathing rate based upon the acquired breathing data, (2) controlling the measurement process and setting up the constant parameters necessary to for breathing rate calculations, (3) carrying out the final analysis and evaluation of the breathing rate measurement error. The software also produced a bar chart which was updated based upon previously set parameters such as duration of the measurement and durations of breathing in (inspiration) and breathing out (expiration). The bar charts clearly validated that the subject under test was breathing and ensured the determination of a relatively constant breathing rate. The application also produced the final value of the respiratory rate, which was used for data processing and determination of the system error rate.The multichannel measurement system (including our novel probe) was used to monitor the subject’s breathing activity (measured as cyles or respirations per minute) with a sampling frequency of 300 Hz. For example, the Bragg wavelength shift for the subject M1 is shown in The key experimental results of breathing measurements are summarized in The acquired data for the blood pressure heart rate measurement were processed by using a Butterworth second order band-pass filter with corner frequencies Using Fourier series analysis , we deteIn order to compare the differences between the reference heart rate (HR) and heart rhythm estimated using the signal from the sensor, the Bland–Altman plot was utilized . The difThe key experimental results of cardiac activity measurements are summarized in D is the discriminant which must be non-zero and is given in the following equation:As the FBG is sensitive to both temperature and deformation, one possible way to detect both simultaneously is to use two FBGs with different thermal and deformation sensitivitities . Our novUsing the above-mentioned Equations (7) and (8), it is possible to determine the extent of deformation and temperature from the two FBG wavelengths. Our novel probe and its associated multichannel system offer the possibility of continuous monitoring of the basic vital signs  in up to 128 patients altogether. The creation of a totally non-invasive, electrically safe (can be used in the magnetic resonance imaging environment), cost-effective, and patient-friendly technology that enables large scale vital sign monitoring, and data collection, and analysis is indeed exciting. Such technology could prove very useful for long-term health care facilities, hospitals and clinics. Our novel non-invasive biocompatible measurement probe ensures maximum electrical safety and patient comfort. The functionality of the proposed system was verified by a series of real experimental measurements of basic vital signs.Due to space limitation, we do not intend to consider all aspects of the design and implementation of our novel sensor system here. This short article should serve as a gateway into and an initial step towards the introduction of a new field of non-invasive and cost-effective patient monitoring which is in its infancy and has not been comprehensively explored. For any new biomedical technology like our novel sensor system and its underlying methodologies to qualify as an effective scientific instrument, and more importantly, gain clinical acceptance and find daily utilization in common clinical practice, it is essential to carry out extensive clinical research to validate its safety and efficacy. These important requirements compel us to set comprehensive research goals for clinical trials in the near future.It is important to emphasize that the PDMS offers a unique set of desirable characteristics suitable for biomedical applications. Its non-reactivity to human skin, its mechanical and thermal resistance, its immunity to electromagnetic noise, and its ability to increase the temperature sensitivity make the PDMS a very attractive material of choice for our novel system.However, one of the possible and current ways of non-invasive monitoring methods of vital signs of the human body is the use of patch monitors ,40 or seThe team of authors offers a solution which is basically focused on the monitoring of long-term ill patients with a minimum of physical movement load. During experiments, all test subjects were asked to simulate their natural behavior in the most accurate way . These aspects are taken into account in the results described above of the probe efficiency, or, more precisely, of the whole measurement system. Authors are ready to carry out a detailed analysis of the influence of these artifacts in the follow-up research.In this article, we briefly described the overall design and realization of the prototype of a novel non-invasive multichannel hybrid fiber-optic sensor system for basic vital sign monitoring. Once clinically tested and validated, it has a great potential to establish itself on the market in the field of modern non-invasive patient monitoring. The main advantage of our solution is the design of a novel patient-friendly measurement probe, which constitutes the core of our system. The functionality of the system was verified by a series of experimental measurements of vital signs . The integration of these three vital parameters within one all-purpose probe represents a unique patented solution by the authors. Our experimental results, acquired by testing our novel prototype in research laboratory conditions, have unambiguously proven the functionality of the system. To gain clinical acceptance and find daily utilization in common clinical practice, we are now positioned to carry out extensive clinical research to validate the safety and efficacy of our system.None of the patients participating in the study complained of any discomfort associated with the presence of the sensor in a thoracic strap placed on her/his chest when asked about it after the examination. The Bland–Altman statistical analysis demonstrates the heart rate detection with a satisfactory accuracy in multiple subjects. For the entire data set, 96.54% of the values lie within the ±1.96 SD range for the HR determination. This fact could be acceptable for clinicians as the sensor is designed for monitoring rather than diagnosis. The results of respiratory measurement are characterized by the maximum relative error of 5.41%, and the maximum relative error of temperature measurement is 0.36%. The clinicians at the University Hospital  intend to use this novel sensor in the near future to perform clinical studies on a variety of health care issues.


The mortality rate of critically ill patients is high and the cost of the intensive (ICU) department is among the highest within the health-care industry. The cost will continue to increase because of the aging population in the western world. In the present review, we will discuss the impact of changes in ICU department organization on patient outcome and cost-effectiveness. The general perception that drug and treatment discoveries are the main drivers behind improved patient outcome within the health-care industry is in general not true. This is especially the case for the ICU department, in which the past decades’ organizational changes were the main drivers behind the reduction of ICU mortality. These interventions were at the same time able to reduce cost, something which is rare for drug and treatment discoveries. The organization of the intensive care department has been changed over the past decades, resulting in better patient outcome and reduction of cost. Major changes are the implementation of the “closed format” and electronic patient record. Furthermore, we will present possible future options to improve the organization of the ICU department to further reduce mortality and cost such as pooling of dedicated ICU into mixed ICU and embedding business strategies such as lean and total quality management. Challenges are ahead as the ICU is taking up the largest share of national health-care expenditure, and with the aging of the population, this will continue to increase. Besides future improvements of organizational structures within the ICU, the focus should also be on the implementation of and compliance with proven beneficial organizational structures. Intensive care units (ICUs) are among the most complex and expensive departments in a hospital. The innate complexity of the ICU makes organizational structuring of care an attractive target for performance improvement strategies. One improvement in the past is assigning “intensivists”  in managing ICU patients instead of specialists from the referral medical departments, which is also called “closed format” ICU departments. This closed format transformation has shown a beneficial impact on patient outcomes in a number of studies –3. HowevThe Medline database was used to identify Medical Subject Headings (MeSH) to select search terms. In addition to MeSH terms, we also used free-text words. Search terms referred to aspects of the ICU organization  as well as related topics . Relevance of each paper was assessed using the online abstracts. In addition, the reference lists of retrieved papers were screened for potentially important papers.The intensive care department is the most expensive hospital department. In the US alone, annual critical care medicine costs nearly doubled from 2000 to 2010 (from $56.6 to an estimated amount of $108 billion). Although the proportion of hospital cost allocated to critical care medicine (13.2%) decreased by 1.5% and the proportion of national health expenditures (4.14%) remained stable, the proportion of the gross domestic product used by critical care medicine increased from 0.66% in 2005 to 0.74% in 2010 . The maiIn the early days of the ICU, patients admitted to the ICU were treated by the referring physicians. Although referring physicians had extensive knowledge on the specific disease the patient was suffering from, there was a lack of knowledge concerning the intensive care treatment these patients needed. Another issue was the lack of continuity of care for these critically ill patients, as the referring physicians were not providing 7-day-per-week coverage of care. This issue was recognized in the 1990s and resulted in the development of the “Leapfrog initiative” . In shorThe positive effect of the closed format intensive care staffing on patient outcome, length of stay, and cost raised the question whether a 24-h availability of an intensivist would even further improve these results compared to having only an in-house intensivist during office hours. This hypothesis was supported by a study on the neonatal ICU showing mortality reduction among premature neonates admitted when they introduced a neonatologist or neonatal fellow in-house . AnotherIntensivist specialists are scarce recourses and should be utilized as high as possible. For this reason, Dara et al. looked at the optimal intensivist-to-bed ratio . Four tiWhat is true for the intensivist-to-bed ratio is probably also true for nurse-to-bed ratio. In many countries, intensive care nurses are specialized nurses with extra training. It is not known what the optimum ratio is. In most counties, the ratio of nurse to patient is between 1:1 and 1:2. For patients after hepatectomy or esophagectomy, there is evidence that less patients per nurse results in a decrease in pulmonary or infectious complications, while mortality was not significantly different . A recenGiven the fact that critically ill patients are often admitted to the ICU from general nursing departments, it seemed logical to install teams that reach out to these patients before detoriation begins . The CocThe introduction of patient digital management systems (PDMS) provided intensivists with a fast overview of patient’s critical data. Having an interface with the electronic medical record at the unit level was significantly associated with a lower risk of mortality in the ICU . The finIn manufacturing and business, one source of competitive advantage is consolidation of separate units which results in increase of scale and reduction of overhead. Within the service industry, consolidation or pooling also results in improvement of service capacity, hence reduction of wait time. The positive effect of pooling or consolidation might be a future improvement within the ICU. The formation of a mixed closed format ICU model: one central ICU in a hospital instead of several small ones , to which all patients independent of their underlying conditions are admitted. This is illustrated in Figs. The main purpose of a step down unit on an ICU is to bridge the differences between the ICU and a general ward  and therefore to reduce the readmission ratio. Readmission is known to be associated with adverse outcomes . CaregivInter-hospital transport of critically ill patients may have a positive effect on resource utilization by pooling admission capacity of the medical centers or creating focus clinics for certain patient categories. Furthermore, transportation enables the distribution of the most severe patients to large referral medical centers and the less severe patients to more rural centers. In this way, you optimize the utilization by level of care and it may improve the overall patient outcome . For insThe closed format model of ICU is a superior clinical practice as discussed above, but shortage of intensivists and financial reasons led to the development of telemedicine. In one study , they shTotal quality management (TQM) is a philosophy of management for continuously improving the quality of products and processes. According to TQM, quality is a process that can be managed and requires ongoing evaluation and change ). Before we can apply TQM and CQI in the ICU, we need specific quality indicators. A few of these indicators have been identified for the ICU: (1) percentage of patients with central venous catheter infections, (2) percentage of patients with ventilator-associated pneumonia, (3) percentage of patients with vancomycin-resistant enterococcus, (4) number of complications per patient, (5) rate of gastrointestinal bleeding, (6) average days of mechanical ventilation, (7) average ICU length of stay, and (8) patient satisfaction . Other iFrom recent studies in ICU patients, we know that improving patient safety has impact on the safety climate as well as on mortality and length of stay , 48. RisOn the Mend [The processes in an ICU can partly be seen as a manufacturing process. A future improvement could be identifying processes which work in the manufacturing industry which are also applicable for the ICU. One of the possible processes could be lean management. Lean management is a philosophy which is mainly derived from the Toyota Production System (TPS). The original seven “wastes” also known as “muda” were identified by Taiichi Ohno, the Toyota executive felt to be the main developer of the Toyota Production System . Later, the Mend . They hathe Mend  but failthe Mend . Evidencthe Mend , 57. WheThe evidence that changes in organizational structures in the intensive care department are able to have significant impact on patient outcome and cost is straightforward and sound. However, the implementation and compliance with these recommendations can be difficult. Pronovost et al. showed  that theThe organization of the intensive care department has been changed over the past decades resulting in better patient outcome and reduction of cost. Major changes are the implementation of the closed format and electronic patient record. Challenges are ahead as the ICU is taking up the largest share of national health-care expenditure, and with the aging of the population, this will continue to increase. We would like to advocate for standard inclusion of cost analysis into future study reports, as financial constraints within the health-care industry have become an important issue nowadays and cost-effectiveness may influence decision-making whether or not to implement an intervention. Besides future improvements of organizational structures within the ICU, the focus should also be on implementation of and compliance with proven beneficial organizational structures.


The aim of this study is on the investigation of motion noise removal techniques using two-accelerometer sensor system and various placements of the sensors on gentle movement and walking of the patients. A Wi-Fi based data acquisition system and a framework on Matlab are developed to collect and process data while the subjects are in motion. The tests include eight volunteers who have no record of heart disease. The walking and running data on the subjects are analyzed to find the minimal-noise bandwidth of the SCG signal. This bandwidth is used to design filters in the motion noise removal techniques and peak signal detection. There are two main techniques of combining signals from the two sensors to mitigate the motion artifact: analog processing and digital processing. The analog processing comprises analog circuits performing adding or subtracting functions and bandpass filter to remove artifact noises before entering the data acquisition system. The digital processing processes all the data using combinations of total acceleration and z-axis only acceleration. The two techniques are tested on three placements of accelerometer sensors including horizontal, vertical, and diagonal on gentle motion and walking. In general, the total acceleration and z-axis acceleration are the best techniques to deal with gentle motion on all sensor placements which improve average systolic signal-noise-ratio (SNR) around 2 times and average diastolic SNR around 3 times comparing to traditional methods using only one accelerometer. With walking motion, ADDER and z-axis acceleration are the best techniques on all placements of the sensors on the body which enhance about 7 times of average systolic SNR and about 11 times of average diastolic SNR comparing to only one accelerometer method. Among the sensor placements, the performance of horizontal placement of the sensors is outstanding comparing with other positions on all motions. Understanding the heart activities in every cardiac cycle is very useful in evaluating its performance. Monitoring the heart activities is extremely useful in screening and detecting of many cardiac related diseases. With the advance of technology, seismocardiography (SCG) observed by Bozhenko in 1962 [The authors in  suggesteMotion artifact removal of SCG signals has not been thoroughly studied. A study analyzed, identified and eliminated the segments of SCG signal containing some kind of noise which was created at a specific time during recoding . The autAll the above studies used only one accelerometer placing on the sternum. Recently, multi-site and multi-location accelerometer concepts on SCG have been investigated and reported in ,25. In aThe DAQ system consists of a rechargeable power supply, a 16-bit, 8-channel analog to digital converter, an ARM microcontroller, and a Wi-Fi module packed in a single PCB. The ADC is sampled at a rate of 1000 sample per second. SCG and ECG were simultaneously recorded on eight volunteers who have no record relating to heart disease with age 32.1 ± 4.5 years, weight 78.2 ± 12.7 kg and height 171.1 ± 7.5 cm. Each subject performed one minute for stationary, one minute for sitting on a chair and moving back and forth gently, one minute for walking on a treadmill with a speed around 5 km/h (around 80 m/s) and one minute for running on treadmill with a speed approximate 8 km/h (around 130 m/s). in The purpose in this study is to measure the SCG signal on active people so it needs to deal with the body movement noise and the use of two sensors (accelerometers) placed in different positions on the chest is investigated. It is assumed that one sensor is placed near to the heart to capture strong SCG signal with body movement and another one is placed far from the heart to capture body movement with minimized effect of the heart vibration. By observation, the noticed strongest SCG signal is below the chest which is indicated by To minimize the effect of respiration, the sensors were placed on the chest bones. The positions of sensors are 3 types: the same horizontal level on chest wall, the same vertical line on middle of chest wall and on diagonal line goes through the heart on chest wall as illustrated in A variety of techniques was applied to eliminate the motion noise on SCG using two accelerometers with different placements. For comparison purpose, the simple motion noise removal technique using only one accelerometer with an analog band-pass filter was also conducted. All techniques using two accelerometers can be classified in two main categories of only analog processing and only digital processing. All motion removal methods measured SCG signal along with ECG signal as reference for analysis purpose.First, the SCG bandwidth is analyzed as the noise frequency is the main drive in noise reduction methods. Two sensors were positioned on the chest of the testing subject, one is placed near to the heart to capture SCG signal and motion, and the other one is placed far from the heart to capture motion and a much smaller SCG signal compared to the other sensor. The signal of the sensors placing near to the heart of five subjects were selected and analyzed using fast fourier transform to identify the high-energy range of the artificial noise including respiratory, body movement  and voice. In this work, the noise from voice is ignored. These noises are picked up by the accelerometers in addition to the clear SCG signal. The respiratory rate is in the range of 8–44 per minute corresponding to 0.13–0.73 Hz . The sigMany studies used only z-axis of one accelerometer with a filter to measure the SCG signal, in this study, the same configuration on an active person was used to exam the effect of motion noise on the measured SCG signal. The accelerometer was attached on the sternum to obtaining the SCG signal. The results of this configuration were also used to compare the performance with the proposed techniques using two accelerometers. The analog processing includes an ADDER and a SUBTRACTOR set-up from an op-amp and an instrumentation amplifier as shown in A real ADDER and SUBTRACTOR with the same placement of sensors for each type  were also tested on a subject made gentle movement and walking. There are two important notices when placing the accelerometers on the chest. To eliminate the motion noise from both accelerometers by summing their z-axes, both sensors z-axis must be placed in opposite directions. For example, one sensor has z-axis faces outward from the chest, and another must be placed with the z-axis inward to the chest. With the SUBTRACTOR, since the common-mode rejection of the instrumentation amplifier is used to remove the motion noise, the two z-axes of the accelerometers need to be placed in the same direction. The ADDER uses the MCP6L02 op-amps to sum the signals and builds the second-order band-pass filter having a cut-off frequency in the range of 20–50 Hz. The total gain from input of the ADDER to the output of the band-pass filter is around 480. The output signal has an offset of 1.25 V and inverted because the ADDER is configured as negative feedback. The inversion can be easily flipped in the Matlab framework. The SUBTRACTOR uses the same op-amps for band-pass filter, but an instrumentation amplifier is used to build the SUBTRACTOR. The inputs of the SUBTRACTOR are coupled with a high-pass filter with a cut-off frequency of 20 Hz to bias the inputs and block the DC level from the sensors. The total gain is kept consistently with the ADDER which is around 480 for comparison. It also has the output offset at 1.25 V, but it is not in reversed form as the output of ADDER.TOTAL_ACC of the heart vibration from all data of the 3 axes of the two accelerometers.x1, y1, z1 are the data of three-axis of the first accelerometer and x2, y2, z2 are the data of three-axis of the second accelerometer. Then, the TOTAL_ACC is filtered with a digital zero-phase band-pass filter (20–50 Hz) for further noise removal. The filtered TOTAL_ACC is used for the detection step.The digital processing comprises two different combinations of data sets using two accelerometers in the Matlab framework. The signals from the two sensors placed in the same direction of all three axes go directly into the DAQ and their data are processed in two different strategies. (Z_ACC) is also filtered with a digital zero-phase band-pass filter (20–50 Hz) for further noise removal. The filtered Z_ACC is used for the detection step.abs is the absolute function and z1, z2 are the z-axis data of two accelerators. The absolute function is used to ensure the difference of two z-axis data always positive so that there is no concern on the position interchange of the two accelerometers. The calculated acceleration is then passed through a FIR low-pass filter. The filter was designed by Matlab with the following configurations: 330 orders, 6 dB cut-off frequency at 6.7 Hz, 60 dB of stopband attenuation, and 1 dB of passband ripple. The parameters for filter design were obtained based on facts and experiments using Matlab to provide good performance and maintain characteristics of the SCG. A person must have systolic and diastolic ratio less than 1.2. The maximum heart beat is 220 beat-per-minute (bpm) and the minimum heart rate is 30 bpm. For the lowest heart rate, the systolic interval must be below 1091 ms. For the highest heart rate, the systolic period has to be under 149 ms. These set the frequency constraints. To maintain the timing and phase, all filters in the algorithm have the same order and are applied zero-phase filtering (filtering in both forward and reverse directions). As a result, it requires the number of input data of at least triple the order of the filter. For real-time detection, algorithm processes on segments of 1 s of data  so that the order of all filters must be less than 333.The second strategy uses only the combination of z-axis of both accelerometers; then, the combined data The results are compiled under the number of systoles and diastoles detected compared to the manual count from the reference ECG during testing. Moving average and interpolation methods were used to identify the systoles and diastoles. In the first method, the slope, a moving average threshold, and systolic interval constraint are utilized. In the second method, instead of using the threshold, the peak pattern of the SCG signal energy is used. The sample points of interpolation are the maxima of the SCG energy signal. Spline interpolation is applied in this algorithm. The collected ECG signal was used only for manual annotation and comparison. This moving average method has an average error rate of 4% for systolic detection and 9% for diastolic detection on the eight testing subjects. The average processing time of the moving average method is 75.2 ms for one-minute data which is suitable for realtime wearable devices in healthcare applications.sys = Systolic variance/quiescent variance and SNRdia = Diastolic variance/quiescent variance. The average of systolic and diastolic SNRs are calculated for all cycles. The Vpp of both systoles and diastoles are also picked manually cycle by cycle then calculate the average. The distortion level is also looked at. Signal-to-noise ratios of the systolic and diastolic phase are also calculated for comparison. The results also present SNR and Vpp as indicators to compare the proposed method with existing methods. Both data of one-accelerometer and two-accelerometer method are filtered with the bandpass filter (20–50 Hz) using Labchart Reader software v8.1 to remove the mean. The Labchart reader was then used to calculate the variance of filtered data. The peaks of variance corresponding to systole and diastole were picked manually based on the ECG. The variance peak adjacent to the R peak of ECG is annotated as systolic variance. The variance peak next to the T wave of ECG is marked as diastolic variance. The variance in quiescent period (between a diastolic and consecutive systolic) was also picked manually. Then, the SNR for systole and diastole in each cycle are calculated by SNRUnder gentle motion, the two accelerometers placed horizontal, vertical and diagonal on the chest with SUBTRACTOR and the analog band-pass filter can effectively eliminate the artifact noise. All systolic and diastolic phases can be determined without the assistance from the reference ECG signal. Under walking motion, the two accelerometers placed horizontal, vertical and diagonal on the chest with SUBTRACTOR and the analog band-pass filter can deal with artifact noise better than using only one accelerometer. At least, no saturation is caused by walking motion even with the same high total gain when using one accelerometer. Although the SUBTRACTOR used high-performance common-mode rejection to suppress the walking noise and keep the output signal in range with the DAQ inputs, the two sensors do not react in the same way with walking motion which are shown by brown ovals in The z-axis of both sensors placed vertical on the chest looks quite similar comparing to the horizontal placement as shown in For gentle motion, the two accelerometers placed horizontal, vertical and diagonal on the chest with ADDER and the analog band-pass filter can remove most of the artifact noise. With or without the need of the reference ECG, all cardiac phases can be identified. The average measurements on all recognized systoles and diastoles of output signals on three types of sensor placement with ADDER and gentle movement are tabulated in For walking motion, the two accelerometers placed horizontal, vertical and diagonal on the chest with ADDER and the analog band-pass filter cannot efficaciously tackle walking motion. Some saturation caused by walking motion appears on many portions of the output signals. Saturation also results in the loss of information and false solutions in the detection step. The possible cause is that the ADDER cannot eliminate totally the walking noise in high-frequency range, so the difference of the two z-axis signals is significant. The high inequality combining with high amplification gain leads to saturation on the output signal. In addition, sensor differences and the opposite direction of placement, the dis-similar force propagation path corresponding to sensor positions can be another reason of different response. The two equations used in digital processing on the two accelerometers are repeated here for convenience:The following sub-sections comprises the results of using the total acceleration and z-axis acceleration to cope with gentle movement and walking motion in three places of the two sensors including horizontal, vertical, and diagonal. The gentle and walking data sets applied the above equations belong to analog processing with SUBTRACTOR because both sensors placing on the same directions for all axes have a better similarity on the reaction than placing on opposite directions when using ADDER. Hence, the results of both equations will also be compared to the results of analog processing with SUBTRACTOR.For gentle movements, the process successfully eliminate artifact noises. All systolic and diastolic phases are identifiable referring to ECG signal, but the output signal of the SUBTRACTOR is lagged by 15 ms compared to the outputs of total acceleration and z-axis acceleration. The reason is the delay of the instrumentation amplifier and the band-pass filter in analog processing method. The average Vpp of systoles and diastoles of the subtraction is always greater than the total acceleration and z-axis acceleration, but its SNRs are always smaller than the total acceleration and z-axis acceleration. It means that the analog processing may also increase the output noise level through the process while digital processing suppresses the noise better at the output. Between total acceleration and z-axis acceleration, the average Vpp of systoles and diastoles are quite close to each other when placing the two sensors on horizontal and diagonal, but the SNRs of total acceleration are smaller than z-axis acceleration for horizontal placement while its SNRs are larger than z-axis acceleration for diagonal placement. The reasons for these are that the z-axis acceleration deal better with noise than total acceleration for horizontal placement and vice versa for diagonal placement.For vertical placement, the average Vpp of systoles and diastoles of total acceleration are greater than z-axis acceleration, but the SNRs of both total acceleration and z-axis acceleration are not much different. It means that although total acceleration may gather information of all three axes to achieve better Vpp, it can also accumulate the noise at output from all three axes rather than the noise only on one axis as z-axis acceleration. The red and blue ovals show examples of determinable systole and diastole in For walking motion, the process cannot totally get rid of the artifact noise on the data sets, but they suppress the noise better on some portions comparing to the SUBTRACTOR. Examples can be seen in the fifth cardiac period which are indicated by the green ovals in A wireless DAQ combining with analog front-ends and algorithms on the Matlab framework are used to examine various motion removal techniques on the subjects while they were making soft movement or walking. There are two main procedures to remove the motion noise including analog processing and digital processing. They were tested on three placements of sensors including horizontal, vertical and diagonal with two kinds of motion noise comprising gentle movement and walking. Optimized bandwidth of the SCG signal was also analyzed on walking and running data of five subjects which is from 20 to 50 Hz. The noise removal techniques using two accelerometers provide better performance compared to traditional methods using only one sensor as summarized in With gentle motion, almost all noise removal techniques can recover most systolic and diastolic portions of the SCG signal. The frequency of gentle motion is out of range of the band-pass filter, so it can be removed completely. Although the techniques of using ADDER have good Vpps on all three placements, the SNRs of total acceleration and z-axis acceleration are much better than the others on all placements. The total acceleration and z-axis acceleration improve average systolic SNR around 2 times and average diastolic SNR around 3 times comparing to using only one accelerometer. Because the performance is not significant different among sensor placements when coping with gentle motion, placing the sensor horizontally is the best as the sensor setup is very simple. With walking motion, all techniques cannot totally remove artifact noise due to walking. Although the Vpp of walking motion is smaller than the Vpp of gentle motion, the frequency of some walking portions still in the bandwidth of the bandpass filter, so they are amplified and overlap with the interested SCG signal. Again, the methods of using ADDER have good Vpps on all three placements and highest systolic SNRs on horizontal position. The SNRs of ADDER and z-axis acceleration are still mostly better than the others in all sensor positions. The SNRs of ADDER and z-axis acceleration are generally better than the others in all sensor positions; they enhance about 7 times of average systolic SNR and about 11 times of average diastolic SNR comparing to using one accelerometer. The performance of horizontal placement is outstanding comparing with other positions when coping with walking motion.The total acceleration can enhance the SNRs with gentle motion by gathering all information from three axes, but with walking motion, the total acceleration may also accumulate the noise from three axes which causes lower SNRs comparing with ADDER and z-axis acceleration. The SNR results with walking motion may vary due to how synchronize between high-energy portions of walking motion with systoles/diastoles. If they are in-sync either with systoles or diastoles, those portions will be distorted and unidentified. If high-energy portions of walking stay in quiescent period of the output signals, both systoles and diastoles can be recognized. The reasons of less effectiveness of walking motion removal might be due to different reaction of two sensors to the motion. This can be the discrepancy or unaligned placement of the two sensors. The sensor reacts more similar with low-frequency noise such as gentle movement than high-frequency noise in walking, and the more the two sensor responses are different, the more the distortion appears on the output signal.In this study, the combination of three axes of the two accelerometers using total acceleration was investigated and showed the enhancement in the results. In addition, the three positions of two sensors were tested to confirm which one can achieve the best quality SCG which has not been conducted by previous studies. The horizontal placement is simple, convenient, and provides better SCG waveforms. The dissimilar response from the two sensors may come from the un-aligned placement which means both sensors are not placed on the same plane. To overcome this challenge, a calibration procedure should be developed to compensate the different reaction of the two sensors. Based on detected systolic and diastolic phases from this proposed techniques and taking the advantages of the characteristics of the SCG signal , the event-detection algorithm searches inside intervals to locate cardiac events. Moving average method or interpolation can be used to detect SCG events shown in


A crucial assumption in health valuation methods is that respondents pay equal attention to all information components presented in the response task. So far, there is no solid evidence that respondents are fulfilling this condition. The aim of our study is to explore the attendance to various information cues presented in the discrete choice (DC) response tasks.Eye tracking was used to study the eye movements and fixations on specific information areas. This was done for seven DC response tasks comprising health-state descriptions. A sample of 10 respondents participated in the study. Videos of their eye movements were recorded and are presented graphically. Frequencies were computed for length of fixation and number of fixations, so differences in attendance were demonstrated for particular attributes in the tasks.All respondents completed the survey. Respondents were fixating on the left-sided health-state descriptions slightly longer than on the right-sided. Fatigue was not observed, as the time spent did not decrease in the final response tasks. The time spent on the tasks depended on the difficulty of the task and the amount of information presented.Eye tracking proved to be a feasible method to study the process of paying attention and fixating on health-state descriptions in the DC response tasks. Eye tracking facilitates the investigation of whether respondents fully read the information in health descriptions or whether they ignore particular elements. Several preference-based measurement frameworks have been developed to quantify health conditions and express their quality , 2. In gThe core of a preference-based measurement framework consists of a response task comparing at least two objects. In the case of health these can be a pair of health descriptions (or combinations with duration of life or risk of immediate death). The respondents do not score the health attributes one by one but consider the whole set of attributes , which requires reading and mentally processing all of the attributes presented. Subsequently, the complete description should be compared with another description or other information elements  in another description. After given descriptions are compared, a choice has to be made in favor of the most preferable one.Conventionally, there were two preference-based methods commonly used for health state valuations: TTO (time trade-off) and SG (standard gamble). These methods—often called valuation techniques—proved to have substantial biases –8. MoreoThe choice processes can be described by the means of process tracing research . ProcessTherefore, the current exploratory study investigates the process of paying attention to various information elements of a DC task in a health setting, such as: health-state descriptions presented as alternatives on the left or right side of the screen, or specific attributes describing the health-state. For this, eye tracking—a common research tool in marketing, cognitive science, human computer interaction, and psychology—was used to study the process of paying attention.The eye-tracking study was performed in the Netherlands with 10 respondents who were either members of the general public, or PhD/Master students of the University Medical Center Groningen in contiguous scientific fields . All respondents live in the province of Groningen, the Netherlands. A sample as small as five is often considered sufficient for qualitative and explorative studies , 16. TheThe eye-tracking experiment started with an eye-calibration procedure . Calibration is necessary to establish that the eye-tracking device captures the eye fixation precisely and to minimize deviations between the real focal point and the “tracked” one. After calibration, the respondents were allowed to begin the response tasks. In case that after the first calibration the eye-tracker was unable to detect the eye fixation precisely, the recalibration was performed until precision was reached.http://www.euroqol.org), which assesses functioning in five health attributes (domains), namely Mobility, Self-care, Usual Activity, Pain/Discomfort, and Anxiety/Depression, with five levels each . The order of the health attributes (domains) was kept unchanged throughout the whole experiment. The respondents were expected to take into account the full description of the health states and to devote attention to all five attributes.Choice-based response tasks were presented as PowerPoint slides (font size 12) in the Dutch language. The layout was identical to the EQ-VT  system and consisted of time trade-off  and DC tasks . The DC The literature has shown that the fixation point of the eyes is linked to an individual’s point of attention . By implGazepoint software analysis tools: heat maps and fixation paths in video format; areas-of-interest statistics; and graphs. Heat maps and fixation paths represent the overall pattern of the respondents’ points or areas of attention: the areas of attention, duration of fixations, and direction of fixations  response tasks. To summarize, we found that the respondents pay attention to all elements of the health-state descriptions in the tasks. However, this explorative eye-tracking study revealed differences in attendance for different EQ-5D-5L attributes and a slight longer fixation time on the health-state description on the left side. Respondent fatigue was not demonstrated, however, time spent per task seem to be influenced by the complexity of the task.nd and 3rd) were visited most frequently. Their attraction may be explained by their central position on the screen and by the relative length of the description for these attributes. Another possible explanation is that higher severity levels of an attribute attract more attention compared to attributes of low severity. According to Orquin et al. [The attributes Self-care and Usual Activities . Previous studies were inconclusive about the number of tasks that should be included to avoid respondent fatigue. According to Craig et al. , neitherThis explorative study may be considered a first step towards the application of eye tracking to detect possible fixation strategies that respondents may use in their processes of paying attention to the information cues during the completion of DC response tasks for health-state evaluation. For the DC response task in the context of health states, this study has shown only limited differences in attendance. However, further investigation is warranted, requiring various designs for the more complex valuation techniques or for DC studies with multiplex scenarios . For more complex situations, changing the attribute order and including additional visual cues to enhance the understanding of the health-state description may reveal whether attendance depends on the location of an attribute description rather than (or as well as) on its content.Some limitations of this study should be mentioned. First, the sample is not representative and the sample size is small. Due to the exploratory nature of this study, we considered ten respondents sufficient to reveal important differences in the attendance process. Moreover, the eye-tracker equipment could not capture precisely the eye movements of people wearing glasses. The imprecision was due to the reflection of the lenses, irrespective of the presence or absence of daylight, the positioning of the respondent, the type of room for the experiment, or the screen type. This is considered a limitation because a large portion of the general public wear glasses and they would find it inconvenient or impossible to read the tasks without wearing glasses. Additionally, the eye tracker has a certain level of precision (0.5–1 degrees) which was found to be critical in the designation of small areas of interest as description statements for attributes. Therefore, further studies would require more sophisticated equipment to tackle these issues.A central assumption in this study is that information that is seen is also cognitively processed. When using fixations and saccades to quantify the amount of attention as in the present study, researchers base their analysis on this assumption. Although the assumption is generally validated, there are also empirical findings indicating that eye movements do not necessarily reflect cognitive processes in certain decision contexts . NormallThe current study was based on fixations (number and length). Eye-tracking capabilities may also include information about pupil dilations and the number of eye blinks. The investigation of pupil dilations can be used in the future research for the tasks with changing complexities because dilations can be a consistent index of cognitive load . FurtherIn conclusion, the current study investigated the process of attendance to various information cues presented in response tasks. Overall, respondents tend to pay attention to the full description and do not use shortcuts or disregard particular information elements.S1 FileFigure A. Disregarding particular attributes. Figure B. Left/right asymmetry of focusing. Figure C. Attention to specific attributes. Figure D. Respondent fatigue.(JNB)Click here for additional data file.


The focusing capabilities of a pinhole zone plate lens are presented and compared with those of a conventional Fresnel zone plate lens. The focusing properties are examined both experimentally and numerically. The results confirm that a pinhole zone plate lens can be an alternative to a Fresnel lens. A smooth filtering effect is created in pinhole zone plate lenses, giving rise to a reduction of the side lobes around the principal focus associated with the conventional Fresnel zone plate lens. The manufacturing technique of the pinhole zone plate lens allows the designing and constructing of lenses for different focal lengths quickly and economically and without the need to drill new plates. Beam forming and focusing can be achieved by devices based on refraction or diffraction phenomena. Focusing certain electromagnetic waves, such as soft X-rays and extreme ultraviolet radiation, by means of refracting optics devices has important limitations due to absorption. Diffractive devices are used to improve focusing, and the Fresnel zone plate (FZP) lens is one of the candidates. FZP consists of alternating opaque and transparent rings of certain radius and width in such a way as to cause constructive interference at the focus. However, spatial resolution is limited and depends on the width of the outer rings and it is difficult to acquire high quality patterns. To overcome these limitations, Kipp et al.  proposedThe importance of wave focusing is not only significant in the field of electromagnetic waves, but also extends to the acoustic field. Due to the potential applications of acoustic focusing in areas such as non-destructive evaluation or medical treatments, it has become a hot research topic.Inspired by the studies on extraordinary optical transmission through subwavelength aperture arrays, research has been extended to acoustic waves. Sound transmission through narrow slits and perforated plates has attracted much scientific interest throughout the last 10 years, both theoretically and experimentally ,4,5,6,7.Like in its optical counterpart, to achieve acoustic focusing through constructive interference of diffracted fields, planar diffraction FZPs have been developed. For instance, Moleron et al.  and Li eIn this work, a novel improved design of a FZP lens is reported. It is shown that replacing the transparent rings of a FZP by a distribution of holes can be used for ultrasound focusing, resulting in a pinhole zone plate (PZP) lens. A manufacturing technique of the PZP lens from an air-solid phononic plate is shown. The advantage of PZP lenses and their manufacturing technique is that they can be easily manufactured to match the focal point at a desired frequency. By comparing them against conventional FZPs, it will be shown that the PZP lens achieves a reduction of side lobes over the FZP lens.3, cl = 5670 m/s, ct = 3230 m/s ) and 0.002 m thickness, immersed in water .In order to analyze and compare Franhoufer diffraction of FZPs and PZPs lenses, underwater ultrasound experiments have been performed. Both lenses were made using brass plates with 0.350 m in width and 0. 450 m in length  and (2), the manufacture of the FZP was carried out using a numerical control milling machine. 3) around the plate, taking care that undesired air bubbles did not appear while the film was adhered. In this way, the air contained in the holes prevented ultrasonic wave propagation, creating opaque zones. To construct the lens, the film was carefully cut and removed from the transparent rings, leaving only the film on the opaque rings. The radius used for these rings are the same as those from the FZP lens. Thus, using a single drilled plate, lenses with different focal lengths can be constructed. To construct the PZP, in the first step, an air-solid phononic plate was fabricated to restrict the ultrasound wave propagation . A perfo2. The scan area was collinear with the center-line plane of the piston transducer and the sample lenses (XZ plane). The experimental set-up is based on the ultrasonic immersion transmission technique. The assembly was placed in a water tank. An automated positioning system built around a water tank was used to align and position the hydrophone through a 3D grid of measurement points located at any trajectory inside the tank. The coordinate system used and the experimental set-up are shown in To verify the focusing properties of the pinhole zone plate lens, the commercial finite element method software COMSOL Multiphysics was used to evaluate the lens. The brass used to construct the lens was modeled as a rigid solid.Measurement results of the normalized acoustic pressure amplitude 6. The measured distributions of the normalized acoustic pressure amplitude along x-axis at z = 0 of both FZP and PZP lenses are shown in The focusing performance of a PZP has been demonstrated experimentally and numerically. The experimental results are in agreement with the simulated ones. These results have been compared with a traditional FZP lens. In the particular case analyzed, it was observed that focal intensities are higher in the FZP case than in PZP one, due to the fact that total field at the focus is the sum of the fields coming from the individual holes. To increase the intensity at the focus in the PZP lens, it will be necessary to increase the number of holes. Due to the lens design with pinholes, a smooth filtering effect is created and a decrease of the side lobes around the principal focus associated with the conventional FZP lens is achieved. An optimum hole distribution must be implemented in further research to increase the resolution of the PZP lens by increasing the supression of side lobes. On the other hand, the manufacturing technique of the PZP lens allows designing and constructing lenses for different focal lengths without the need to drill new plates.