The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Aurelio Cappozzo - One of the best experts on this subject based on the ideXlab platform.
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human movement analysis using Stereophotogrammetry part 1 theoretical background
Gait & Posture, 2005Co-Authors: Aurelio Cappozzo, Alberto Leardini, Ugo Della Croce, Lorenzo ChiariAbstract:This paper sets the stage for a series of reviews dealing with the problems associated with the reconstruction and analysis of in vivo skeletal system kinematics using optoelectronic stereophotogrammetric data. Instantaneous bone position and orientation and joint kinematic variable estimations are addressed in the framework of rigid body mechanics. The conceptual background to these exercises is discussed. Focus is placed on the experimental and analytical problem of merging the information relative to movement and that relative to the morphology of the anatomical body parts of interest. The various global and local frames that may be used in this context are defined. Common anatomical and mathematical conventions that can be used to describe joint kinematics are illustrated in a comparative fashion. The authors believe that an effort to systematize the different theoretical and experimental approaches to the problems involved and related nomenclatures, as currently reported in the literature, is needed to facilitate data and knowledge sharing, and to provide renewed momentum for the advancement of human movement analysis.
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human movement analysis using Stereophotogrammetry part 3 soft tissue artifact assessment and compensation
Gait & Posture, 2005Co-Authors: Alberto Leardini, Lorenzo Chiari, Ugo Della Croce, Aurelio CappozzoAbstract:When using optoelectronic Stereophotogrammetry, skin deformation and displacement causes marker movement with respect to the underlying bone. This movement represents an artifact, which affects the estimation of the skeletal system kinematics, and is regarded as the most critical source of error in human movement analysis. A comprehensive review of the state-of-the-art for assessment, minimization and compensation of the soft tissue artifact (STA) is provided. It has been shown that STA is greater than the instrumental error associated with Stereophotogrammetry, has a frequency content similar to the actual bone movement, is task dependent and not reproducible among subjects and, of lower limb segments, is greatest at the thigh. It has been shown that in in vivo experiments only motion about the flexion/extension axis of the hip, knees and ankles can be determined reliably. Motion about other axes at those joints should be regarded with much more caution as this artifact produces spurious effects with magnitudes comparable to the amount of motion actually occurring in those joints. Techniques designed to minimize the contribution of and compensate for the effects of this artifact can be divided up into those which model the skin surface and those which include joint motion constraints. Despite the numerous solutions proposed, the objective of reliable estimation of 3D skeletal system kinematics using skin markers has not yet been satisfactorily achieved and greatly limits the contribution of human movement analysis to clinical practice and biomechanical research. For STA to be compensated for effectively, it is here suggested that either its subject-specific pattern is assessed by ad hoc exercises or it is characterized from a large series of measurements on different subject populations. Alternatively, inclusion of joint constraints into a more general STA minimization approach may provide an acceptable solution.
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human movement analysis using Stereophotogrammetry part 2 instrumental errors
Gait & Posture, 2004Co-Authors: Lorenzo Chiari, Alberto Leardini, Ugo Della Croce, Aurelio CappozzoAbstract:This paper reviews the main aspects involved with the management of instrumental errors associated with video-based optoelectronic Stereophotogrammetry. Insights on how such errors propagate to kinematic quantities are of great interest in the field of human movement analysis to improve the precision and reliability of measurements. The review focuses on the technical assessment and analytical compensation procedures to cope with instrumental errors. Relevant contributions dealing with intrinsic sources of systematic and random errors, such as the issues concerning camera calibration and filtering and smoothing of marker position data, are presented. Procedures for marker imaged processing, and missing marker recovery are also surveyed. Methods for checking the accuracy and precision of stereophotogrammetric systems are then reviewed. Finally, since the desired outcome of the movement measurements is a reliable estimate of body segment kinematics, state-of-the-art techniques proposed for minimization of error propagation arising from a cluster of external markers are described.
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pelvis and lower limb anatomical landmark calibration precision and its propagation to bone geometry and joint angles
Medical & Biological Engineering & Computing, 1999Co-Authors: Ugo Della Croce, Aurelio Cappozzo, Dc KerriganAbstract:Human movement analysis using Stereophotogrammetry is based on the reconstruction of the instantaneous laboratory position of selected bony anatomical landmarks (AL). For this purpose, knowledge of an AL's position in relevant bone-embedded frames is required. Because ALs are not points but relatively large and curved areas, their identification by palpation or other means is subject to both intra- and inter-examiner variability. In addition, the local position of ALs, as reconstructed using an ad hoc experimental procedure (AL calibration), is affected by photogrammetric errors. The intra- and inter-examiner precision with which local positions of pelvis and lower limb palpable bony ALs can be identified and reconstructed were experimentally assessed. Six examiners and two subjects participated in the study. Intra- and inter-examiner precision (RMS distance from the mean position) resulted in the range 6-21 mm and 13-25 mm, respectively. Propagation of the imprecision of ALs to the orientation of bone-embedded anatomical frames and to hip, knee and ankle joint angles was assessed. Results showed that this imprecision may cause distortion in joint angle against time functions to the extent that information relative to angular movements in the range of 10 degrees or lower may be concealed. Bone geometry parameters estimated using the same data showed that the relevant precision does not allow for reliable bone geometry description. These findings, together with those relative to skin movement artefacts reported elsewhere, assist the human movement analyst's consciousness of the possible limitations involved in 3D movement analysis using Stereophotogrammetry and call for improvements of the relevant experimental protocols.
Alberto Leardini - One of the best experts on this subject based on the ideXlab platform.
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quantification of soft tissue artefact in motion analysis by combining 3d fluoroscopy and Stereophotogrammetry a study on two subjects
Clinical Biomechanics, 2005Co-Authors: Rita Stagni, Silvia Fantozzi, A Cappello, Alberto LeardiniAbstract:BACKGROUND: Soft tissue artefact is the most invalidating source of error in human motion analysis using optoelectronic Stereophotogrammetry. It is caused by the erroneous assumption that markers attached to the skin surface are rigidly connected to the underlying bones. The quantification of this artefact in three dimensions and the knowledge of how it propagates to relevant joint angles is necessary for the interpretation of gait analysis data. METHODS: Two subjects, treated by total knee replacement, underwent data acquisition simultaneously with fluoroscopy and Stereophotogrammetry during stair climbing, step up/down, sit-to-stand/stand-to-sit, and extension against gravity. The reference 3D kinematics of the femur and tibia was reconstructed from fluoroscopy-based tracking of the relevant prosthesis components. Soft tissue artefact was quantified as the motion of a grid of retro-reflecting makers attached to the thigh and shank with respect to the underlying bones, tracked by optoelectronic Stereophotogrammetry. The propagation of soft tissue artefact to knee rotations was also calculated. FINDINGS: The standard deviation of skin marker trajectory in the corresponding prosthesis-embedded anatomical frame was found up to 31 mm for the thigh and up to 21 mm for the shank. The ab/adduction and internal/external rotation angles were the most affected by soft tissue artefact propagation, with root mean square errors up to 192% and 117% of the corresponding range, respectively. INTERPRETATIONS: In both the analysed subjects the proximal thigh showed the largest soft tissue artefact. This is subject- and task-specific. However, larger artefact does not necessarily produce larger propagated error on knee rotations. Propagated errors were extremely critical on ab/adduction and internal/external rotation. These large errors can nullify the usefulness of these variables in the clinical interpretation of gait analysis.
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human movement analysis using Stereophotogrammetry part 1 theoretical background
Gait & Posture, 2005Co-Authors: Aurelio Cappozzo, Alberto Leardini, Ugo Della Croce, Lorenzo ChiariAbstract:This paper sets the stage for a series of reviews dealing with the problems associated with the reconstruction and analysis of in vivo skeletal system kinematics using optoelectronic stereophotogrammetric data. Instantaneous bone position and orientation and joint kinematic variable estimations are addressed in the framework of rigid body mechanics. The conceptual background to these exercises is discussed. Focus is placed on the experimental and analytical problem of merging the information relative to movement and that relative to the morphology of the anatomical body parts of interest. The various global and local frames that may be used in this context are defined. Common anatomical and mathematical conventions that can be used to describe joint kinematics are illustrated in a comparative fashion. The authors believe that an effort to systematize the different theoretical and experimental approaches to the problems involved and related nomenclatures, as currently reported in the literature, is needed to facilitate data and knowledge sharing, and to provide renewed momentum for the advancement of human movement analysis.
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human movement analysis using Stereophotogrammetry part 3 soft tissue artifact assessment and compensation
Gait & Posture, 2005Co-Authors: Alberto Leardini, Lorenzo Chiari, Ugo Della Croce, Aurelio CappozzoAbstract:When using optoelectronic Stereophotogrammetry, skin deformation and displacement causes marker movement with respect to the underlying bone. This movement represents an artifact, which affects the estimation of the skeletal system kinematics, and is regarded as the most critical source of error in human movement analysis. A comprehensive review of the state-of-the-art for assessment, minimization and compensation of the soft tissue artifact (STA) is provided. It has been shown that STA is greater than the instrumental error associated with Stereophotogrammetry, has a frequency content similar to the actual bone movement, is task dependent and not reproducible among subjects and, of lower limb segments, is greatest at the thigh. It has been shown that in in vivo experiments only motion about the flexion/extension axis of the hip, knees and ankles can be determined reliably. Motion about other axes at those joints should be regarded with much more caution as this artifact produces spurious effects with magnitudes comparable to the amount of motion actually occurring in those joints. Techniques designed to minimize the contribution of and compensate for the effects of this artifact can be divided up into those which model the skin surface and those which include joint motion constraints. Despite the numerous solutions proposed, the objective of reliable estimation of 3D skeletal system kinematics using skin markers has not yet been satisfactorily achieved and greatly limits the contribution of human movement analysis to clinical practice and biomechanical research. For STA to be compensated for effectively, it is here suggested that either its subject-specific pattern is assessed by ad hoc exercises or it is characterized from a large series of measurements on different subject populations. Alternatively, inclusion of joint constraints into a more general STA minimization approach may provide an acceptable solution.
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human movement analysis using Stereophotogrammetry part 2 instrumental errors
Gait & Posture, 2004Co-Authors: Lorenzo Chiari, Alberto Leardini, Ugo Della Croce, Aurelio CappozzoAbstract:This paper reviews the main aspects involved with the management of instrumental errors associated with video-based optoelectronic Stereophotogrammetry. Insights on how such errors propagate to kinematic quantities are of great interest in the field of human movement analysis to improve the precision and reliability of measurements. The review focuses on the technical assessment and analytical compensation procedures to cope with instrumental errors. Relevant contributions dealing with intrinsic sources of systematic and random errors, such as the issues concerning camera calibration and filtering and smoothing of marker position data, are presented. Procedures for marker imaged processing, and missing marker recovery are also surveyed. Methods for checking the accuracy and precision of stereophotogrammetric systems are then reviewed. Finally, since the desired outcome of the movement measurements is a reliable estimate of body segment kinematics, state-of-the-art techniques proposed for minimization of error propagation arising from a cluster of external markers are described.
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application of Stereophotogrammetry to total body three dimensional analysis of human tremor
International Conference of the IEEE Engineering in Medicine and Biology Society, 1997Co-Authors: Angelo Cappello, Alberto Leardini, Maria Grazia Benedetti, Rocco Liguori, A BertaniAbstract:This work aims at verifying the possibility of investigating joint rotations, with amplitude and frequency ranges typical of pathological human tremor, using commercially available stereophotogrammetric systems together with signal processing techniques. A rotating disk is used as a mechanical tremor simulator to test the ability of the system to track known marker trajectories both in a large and a small calibrated volume. The performances of standard discrete Fourier transform (DFT) and autoregressive techniques are also evaluated and compared in the signal spectrum estimation. Results obtained from a pathological test subject and their dependence on the processing techniques adopted are also presented. The use of Stereophotogrammetry and of the proposed signal spectrum estimation technique allow to quantify both frequency and amplitude content of three-dimensional (3-D) rotations of many human joints simultaneously and therefore to isolate the contribution of each joint to the whole body tremor.
Thomas J J Maal - One of the best experts on this subject based on the ideXlab platform.
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three dimensional Stereophotogrammetry measurement of facial asymmetry in patients with congenital muscular torticollis a non invasive method
International Journal of Oral and Maxillofacial Surgery, 2021Co-Authors: H Vallen, W A Borstlap, M E L Nienhuijs, Tom G J Loonen, B Hoogendoorn, L A Van Vlimmeren, Thomas J J MaalAbstract:The aim of this study was to evaluate three-dimensional (3D) Stereophotogrammetry based methods for measuring craniofacial asymmetry in patients with congenital muscular torticollis (CMT). This study focused on the differences in craniofacial asymmetry in CMT patients compared with a healthy control group using 3D photographs. The difference in facial asymmetry between the CMT group and control group was measured using two methods to analyse facial asymmetry in distinct anatomical regions: (1) mirroring and surface-based registration to analyse the overall facial asymmetry; (2) the 'coherent point drift' based method. Thirty-one patients with CMT and 84 controls were included in the study. A statistically significant difference was found between the CMT patients and a healthy control group. The measured facial asymmetry for the CMT group was 1.71±0.66mm and for the controls 0.46±0.14mm (P<0.05). A significant difference was found in surface ratio for the cheek, nose and the forehead region (P<0.05). With its minimal invasive character, 3D Stereophotogrammetry is a useful tool in measuring the facial asymmetry associated with CMT and to quantify the treatment-induced facial changes. In the future 3D facial data could be used to create a ranking-scale to categorize the severity of facial asymmetry.
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combining deep learning with 3d Stereophotogrammetry for craniosynostosis diagnosis
Scientific Reports, 2020Co-Authors: Guido De Jong, Thomas J J Maal, Jene W Meulstee, Elmar Bijlsma, Myrte Wennen, Erik J Van Lindert, Rene Aquarius, Hans DelyeAbstract:Craniosynostosis is a condition in which cranial sutures fuse prematurely, causing problems in normal brain and skull growth in infants. To limit the extent of cosmetic and functional problems, swift diagnosis is needed. The goal of this study is to investigate if a deep learning algorithm is capable of correctly classifying the head shape of infants as either healthy controls, or as one of the following three craniosynostosis subtypes; scaphocephaly, trigonocephaly or anterior plagiocephaly. In order to acquire cranial shape data, 3D stereophotographs were made during routine pre-operative appointments of scaphocephaly (n = 76), trigonocephaly (n = 40) and anterior plagiocephaly (n = 27) patients. 3D Stereophotographs of healthy infants (n = 53) were made between the age of 3-6 months. The cranial shape data was sampled and a deep learning network was used to classify the cranial shape data as either: healthy control, scaphocephaly patient, trigonocephaly patient or anterior plagiocephaly patient. For the training and testing of the deep learning network, a stratified tenfold cross validation was used. During testing 195 out of 196 3D stereophotographs (99.5%) were correctly classified. This study shows that trained deep learning algorithms, based on 3D stereophotographs, can discriminate between craniosynostosis subtypes and healthy controls with high accuracy.
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effect of skin tone on the accuracy of hybrid and passive Stereophotogrammetry
Journal of Plastic Reconstructive and Aesthetic Surgery, 2019Co-Authors: Tycho S Wesselius, Arico C Verhulst, Dietmar J O Ulrich, Thomas J J MaalAbstract:Summary Background Three-dimensional (3D) surface images acquired from Stereophotogrammetry are increasingly being used to plan or evaluate treatment by plastic surgeons. Stereophotogrammetry exists in active, passive, and hybrid forms. Active and hybrid Stereophotogrammetry are believed to capture darker surfaces more accurately than passive Stereophotogrammetry. The purpose of this study was to investigate whether skin tone has a clinically relevant effect on the accuracy of hybrid and passive Stereophotogrammetry. Materials and methods Seven subjects with different skin tones were recruited. 3D-printed face and breast were spray-painted in six different colors, ranging from white to black. The skin tones and paint colors were objectified by measuring their melanin index. 3D photos of the subjects and 3D prints were acquired with hybrid and passive Stereophotogrammetry. These 3D photos were matched with specialized software, and their geometric differences were calculated. Results None of the 3D photos showed a clinically relevant mean inaccuracy. On the 3D prints, hybrid Stereophotogrammetry resulted in a smaller standard deviation of the inaccuracies than passive Stereophotogrammetry (0.20 ± 0.06 mm vs. 0.35 ± 0.07 mm, p Conclusion Skin tone does not influence the accuracy of hybrid and passive 3D Stereophotogrammetry in a clinically relevant way.
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influence of involuntary facial expressions on reproducibility of 3d Stereophotogrammetry in children with and without complete unilateral cleft lip and palate from 3 to 18 months of age
Clinical Oral Investigations, 2019Co-Authors: Sander Brons, Thomas J J Maal, Rinaldo D Vreeken, S J Berge, Amir M Darroudi, Rania M Nada, Ewald M Bronkhorst, Anne Marie KuijpersjagtmanAbstract:To assess the influence of involuntary facial expressions on 3D facial Stereophotogrammetry reproducibility in children with and without unilateral cleft lip, alveolus and palate (UCLP) aged 3–18 months. Three to eight 3D facial images per time point were acquired within 10 min of 31 children with UCLP and 50 controls at 3, 12 and 18 months of age. 3D mapping of two 3D facial images per subject per age was performed. Distance kits of the full face and nasolabial area were calculated. In the total subject pool, mean variation between two 3D facial images ranged from 0.38–0.88 mm. There were no significant differences within groups for the various ages. Variation between controls and UCLP subjects did not differ significantly. Variation was higher in the nasolabial area than in the full face. The influence of involuntary facial expressions on the estimation of facial growth should not be underestimated, especially in the nasolabial region of UCLP subjects aged 3 months. To improve 3D facial imaging reliability, image capturing should be performed by a trained photographer following a meticulous image capturing protocol, including thorough review after capture. Facial 3D Stereophotogrammetry is a useful tool for monitoring facial growth longitudinally in young children with facial deformities, as no radiation is involved and image capture is easy and fast. It can be performed reliably in children with and without UCLP aged 3–18 months by an experienced photographer utilising a meticulous image capturing protocol.
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a new method for three dimensional evaluation of the cranial shape and the automatic identification of craniosynostosis using 3d Stereophotogrammetry
International Journal of Oral and Maxillofacial Surgery, 2017Co-Authors: Jene W Meulstee, W A Borstlap, S J Berge, L M Verhamme, F Van Der Heijden, G A De Jong, Hans Delye, Thomas J J MaalAbstract:Craniosynostosis is a congenital defect which can result in abnormal cranial morphology. Three dimensional (3D) Stereophotogrammetry is potentially an ideal technique for the evaluation of cranial morphology and diagnosis of craniosynostosis because it is fast and harmless. This study presents a new method for objective characterization of the morphological abnormalities of scaphocephaly and trigonocephaly patients using 3D photographs of patients and healthy controls. Sixty 3D photographs of healthy controls in the age range of 3-6 months were superimposed and scaled. Principal component analysis (PCA) was applied to find the mean cranial shape and the cranial shape variation in this normal population. 3D photographs of 20 scaphocephaly and 20 trigonocephaly patients were analysed by this PCA model to test whether cranial deformities of scaphocephaly and trigonocephaly patients could be objectively identified. PCA was used to find the mean cranial shape and the cranial shape variation in the normal population. The PCA model was able to significantly distinguish scaphocephaly and trigonocephaly patients from the normal population. 3D Stereophotogrammetry in combination with the presented method can be used to objectively identify and classify the cranial shape of healthy newborns, scaphocephaly and trigonocephaly patients.
Ludwig M Heindl - One of the best experts on this subject based on the ideXlab platform.
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accuracy of areal measurement in the periocular region using Stereophotogrammetry
Journal of Oral and Maxillofacial Surgery, 2021Co-Authors: Jinhua Liu, Yongwei Guo, Alexander C. Rokohl, Marat Arakelyan, Ludwig M HeindlAbstract:Purpose The purpose of this study was to evaluate the accuracy of stereophotogrammetric area measurements in the periocular region and analyze the differences between the 2 genders and 2 races. Materials and Methods A prospective study was performed on healthy young volunteers. The sample was composed of 20 Caucasians and 20 Chinese volunteers. Five objects of different sizes (0.16 cm2, 0.36 cm2, 0.64 cm2, 1.44 cm2, and 2.56 cm2) were placed at 7 periocular locations. Caliper and the VECTRA M3 system were used for direct and 3D stereophotogrammetric analysis. Accuracy and differences in 2 different genders and 2 races were analyzed. The predictor variable was the mean absolute deviation between the 2 measurement methods. The nonparametric Wilcoxon signed-rank test or paired t-test was used to test the statistical differences between the 2 measurement methods. A P value Results The mean difference between the 2 measurements of all objects was less than 0.02 cm2, nonparametric Wilcoxon signed-rank test or paired t-test showed no statistically significant (P > .05, respectively) differences between the 2 measurement methods, except for object 1 and object 5 (endocanthion). Chinese and female volunteers tend to have lower accuracy than Caucasians and male volunteers. Conclusions Three-dimensional Stereophotogrammetry is highly accurate for area measurements in the periocular region.
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reliability of Stereophotogrammetry for area measurement in the periocular region
Aesthetic Plastic Surgery, 2021Co-Authors: Jinhua Liu, Yongwei Guo, Xiaoyi Hou, Alexander C. Rokohl, Wanlin Fan, Maxim Formuzal, Ming Lin, Ludwig M HeindlAbstract:Three-dimensional (3D) stereophotography area measurements are essential for describing morphology in the periocular region. However, its reliability has not yet been sufficiently validated. The objective of this study was to evaluate the reliability of 3D stereophotogrammetric area measurements in the periocular region. Forty healthy volunteers had five flat paper objects placed at each of the seven periocular positions including the endocanthion and the upper medial, upper middle, upper lateral, lower medial, lower middle, and the lower lateral eyelid. Two series of photographic images were captured twice by the same investigator. Each image of the first series was measured twice by the same rater, while images of both series were measured once by a second rater. Differences between these measurements were calculated, and the intrarater, interrater, and intramethod reliability was evaluated for intraclass correlation coefficients (ICCs), mean absolute differences (MADs), technical errors of measurements (TEMs), relative errors of measurements (REMs), and relative TEM (rTEM). Our results showed that 21.2% of all ICCs were considered as excellent, 45.5% were good, 27.3% were moderate, and 6.1% were poor. The interrater ICC for the endocanthion location was 0.4% on a low level. MAD values for all objects were less than 0.3 mm2, all TEM were less than 1 mm2, the REM and rTEM were less than 2% for all objects, showing high reliability. 3D Stereophotogrammetry is a highly reliable system for periocular area measurements and may be used in the clinical routine for planning oculoplastic surgeries and for evaluating changes in periocular morphology. Level of Evidence IV This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.
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Reliability of periocular anthropometry using three-dimensional digital Stereophotogrammetry
Graefe's Archive for Clinical and Experimental Ophthalmology, 2019Co-Authors: Yongwei Guo, Xiaoyi Hou, Renbing Jia, Yue Ruan, Friederike Schaub, Alexander C. Rokohl, Konrad R Koch, Jinhua Liu, Ludwig M HeindlAbstract:PurposeNon-invasive three-dimensional (3D) Stereophotogrammetry is becoming increasingly popular in many fields. However, few studies have focused on its periocular application. We aimed to provide evidence for the periocular application of a novel anthropometric procedure using 3D Stereophotogrammetry by evaluating its reliability.MethodsFifty-one Caucasians were recruited (102 eyes; mean age, 31.9 ± 13.6 years). Two sets of 3D images were acquired for each subject, and two measurement sessions were performed on each image by two raters. Fifty-two periocular landmarks were identified, and then 49 corresponding linear, curvilinear, and angular measurements were evaluated for intrarater, interrater, and intramethod reliability.ResultsOur findings showed highly reliable results for mean absolute difference (0.59 and 0.68 unit), relative error measurement (2.66% and 3.08%), technical error of measurement (0.59 and 0.66 unit), relative technical error of measurement (2.71% and 2.96%), and intraclass correlation coefficient (0.98) for intrarater 1 and intrarater 2 reliability; respectively 0.94 unit, 4.06%, 0.89 unit, and 3.94%, as well as 0.97 for interrater reliability; and respectively 0.98 unit, 4.66%, 0.96 unit, and 4.64%, as well as 0.96 for intramethod reliability.ConclusionsThis imaging system and the landmark identification protocol are highly reliable. The collected measurements and their errors can be applied for the comparison of reliability among various 3D imaging systems and populations. It could be utilized for planning surgeries and evaluating treatment outcomes for physicians in ophthalmology, plastic and esthetic surgery, and in the maxillofacial field where periocular morphology alterations are made.
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reliability of periocular anthropometry using three dimensional digital Stereophotogrammetry
Graefes Archive for Clinical and Experimental Ophthalmology, 2019Co-Authors: Yongwei Guo, Xiaoyi Hou, Renbing Jia, Yue Ruan, Friederike Schaub, Alexander C. Rokohl, Konrad R Koch, Jinhua Liu, Ludwig M HeindlAbstract:Non-invasive three-dimensional (3D) Stereophotogrammetry is becoming increasingly popular in many fields. However, few studies have focused on its periocular application. We aimed to provide evidence for the periocular application of a novel anthropometric procedure using 3D Stereophotogrammetry by evaluating its reliability. Fifty-one Caucasians were recruited (102 eyes; mean age, 31.9 ± 13.6 years). Two sets of 3D images were acquired for each subject, and two measurement sessions were performed on each image by two raters. Fifty-two periocular landmarks were identified, and then 49 corresponding linear, curvilinear, and angular measurements were evaluated for intrarater, interrater, and intramethod reliability. Our findings showed highly reliable results for mean absolute difference (0.59 and 0.68 unit), relative error measurement (2.66% and 3.08%), technical error of measurement (0.59 and 0.66 unit), relative technical error of measurement (2.71% and 2.96%), and intraclass correlation coefficient (0.98) for intrarater 1 and intrarater 2 reliability; respectively 0.94 unit, 4.06%, 0.89 unit, and 3.94%, as well as 0.97 for interrater reliability; and respectively 0.98 unit, 4.66%, 0.96 unit, and 4.64%, as well as 0.96 for intramethod reliability. This imaging system and the landmark identification protocol are highly reliable. The collected measurements and their errors can be applied for the comparison of reliability among various 3D imaging systems and populations. It could be utilized for planning surgeries and evaluating treatment outcomes for physicians in ophthalmology, plastic and esthetic surgery, and in the maxillofacial field where periocular morphology alterations are made.
Lorenzo Chiari - One of the best experts on this subject based on the ideXlab platform.
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human movement analysis using Stereophotogrammetry part 3 soft tissue artifact assessment and compensation
Gait & Posture, 2005Co-Authors: Alberto Leardini, Lorenzo Chiari, Ugo Della Croce, Aurelio CappozzoAbstract:When using optoelectronic Stereophotogrammetry, skin deformation and displacement causes marker movement with respect to the underlying bone. This movement represents an artifact, which affects the estimation of the skeletal system kinematics, and is regarded as the most critical source of error in human movement analysis. A comprehensive review of the state-of-the-art for assessment, minimization and compensation of the soft tissue artifact (STA) is provided. It has been shown that STA is greater than the instrumental error associated with Stereophotogrammetry, has a frequency content similar to the actual bone movement, is task dependent and not reproducible among subjects and, of lower limb segments, is greatest at the thigh. It has been shown that in in vivo experiments only motion about the flexion/extension axis of the hip, knees and ankles can be determined reliably. Motion about other axes at those joints should be regarded with much more caution as this artifact produces spurious effects with magnitudes comparable to the amount of motion actually occurring in those joints. Techniques designed to minimize the contribution of and compensate for the effects of this artifact can be divided up into those which model the skin surface and those which include joint motion constraints. Despite the numerous solutions proposed, the objective of reliable estimation of 3D skeletal system kinematics using skin markers has not yet been satisfactorily achieved and greatly limits the contribution of human movement analysis to clinical practice and biomechanical research. For STA to be compensated for effectively, it is here suggested that either its subject-specific pattern is assessed by ad hoc exercises or it is characterized from a large series of measurements on different subject populations. Alternatively, inclusion of joint constraints into a more general STA minimization approach may provide an acceptable solution.
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human movement analysis using Stereophotogrammetry part 1 theoretical background
Gait & Posture, 2005Co-Authors: Aurelio Cappozzo, Alberto Leardini, Ugo Della Croce, Lorenzo ChiariAbstract:This paper sets the stage for a series of reviews dealing with the problems associated with the reconstruction and analysis of in vivo skeletal system kinematics using optoelectronic stereophotogrammetric data. Instantaneous bone position and orientation and joint kinematic variable estimations are addressed in the framework of rigid body mechanics. The conceptual background to these exercises is discussed. Focus is placed on the experimental and analytical problem of merging the information relative to movement and that relative to the morphology of the anatomical body parts of interest. The various global and local frames that may be used in this context are defined. Common anatomical and mathematical conventions that can be used to describe joint kinematics are illustrated in a comparative fashion. The authors believe that an effort to systematize the different theoretical and experimental approaches to the problems involved and related nomenclatures, as currently reported in the literature, is needed to facilitate data and knowledge sharing, and to provide renewed momentum for the advancement of human movement analysis.
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human movement analysis using Stereophotogrammetry part 2 instrumental errors
Gait & Posture, 2004Co-Authors: Lorenzo Chiari, Alberto Leardini, Ugo Della Croce, Aurelio CappozzoAbstract:This paper reviews the main aspects involved with the management of instrumental errors associated with video-based optoelectronic Stereophotogrammetry. Insights on how such errors propagate to kinematic quantities are of great interest in the field of human movement analysis to improve the precision and reliability of measurements. The review focuses on the technical assessment and analytical compensation procedures to cope with instrumental errors. Relevant contributions dealing with intrinsic sources of systematic and random errors, such as the issues concerning camera calibration and filtering and smoothing of marker position data, are presented. Procedures for marker imaged processing, and missing marker recovery are also surveyed. Methods for checking the accuracy and precision of stereophotogrammetric systems are then reviewed. Finally, since the desired outcome of the movement measurements is a reliable estimate of body segment kinematics, state-of-the-art techniques proposed for minimization of error propagation arising from a cluster of external markers are described.
