Anatomical Coordinate System Research Articles

Soft tissue displacement over pelvic anatomical landmarks during 3-D hip movements.

The position, in a pelvis-embedded anatomical coordinate system, of skin points located over the following anatomical landmarks (AL) was determined while the hip assumed different spatial postures: right and left anterior superior and posterior superior iliac spines, and the sacrum. Postures were selected as occurring during walking and during a flexion-extension and circumduction movement, as used to determine the hip joint centre position (star-arc movement). Five volunteers, characterised by a wide range of body mass indices (22-37), were investigated. Subject-specific MRI pelvis digital bone models were obtained. For each posture, the pose of the pelvis-embedded anatomical coordinate system was determined by registering this bone model with points digitised over bony prominences of the pelvis, using a wand carrying a marker-cluster and stereophotogrammetry. The knowledge of how the position of the skin points varies as a function of the hip posture provided information regarding the soft tissue artefact (STA) that would affect skin markers located over those points during stereophotogrammetric movement analysis. The STA was described in terms of amplitude (relative to the position of the AL during an orthostatic posture), diameter (distance between the positions of the AL which were farthest away from each other), and pelvis orientation. The STA amplitude, exhibited, over all postures, a median [inter-quartile] value of 9[6] and 16[11]mm, for normal and overweight volunteers, respectively. STA diameters were larger for the star-arc than for the walking postures, and the direction was predominantly upwards. Consequent errors in pelvic orientation were in the range 1-9 and 4-11 degrees, for the two groups respectively.

The 'straight mouse': defining anatomical axes in 3D embryo models.

A primary objective of the eMouseAtlas Project is to enable 3D spatial mapping of whole embryo gene expression data to capture complex 3D patterns for indexing, visualization, cross-comparison and analysis. For this we have developed a spatio-temporal framework based on 3D models of embryos at different stages of development coupled with an anatomical ontology. Here we introduce a method of defining coordinate axes that correspond to the anatomical or biologically relevant anterior–posterior (A–P), dorsal–ventral (D–V) and left–right (L–R) directions. These enable more sophisticated query and analysis of the data with biologically relevant associations, and provide novel data visualizations that can reveal patterns that are otherwise difficult to detect in the standard 3D coordinate space. These anatomical coordinates are defined using the concept of a ‘straight mouse-embryo’ within which the anatomical coordinates are Cartesian. The straight embryo model has been mapped via a complex non-linear transform onto the standard embryo model. We explore the utility of this anatomical coordinate system in elucidating the spatial relationship of spatially mapped embryonic ‘Fibroblast growth factor’ gene expression patterns, and we discuss the importance of this technology in summarizing complex multimodal mouse embryo image data from gene expression and anatomy studies. Database URL: www.emouseatlas.org

Accuracy of femur reconstruction from sparse geometric data using a statistical shape model

Sparse geometric information from limited field-of-view medical images is often used to reconstruct the femur in biomechanical models of the hip and knee. However, the full femur geometry is needed to establish boundary conditions such as muscle attachment sites and joint axes which define the orientation of joint loads. Statistical shape models have been used to estimate the geometry of the full femur from varying amounts of sparse geometric information. However, the effect that different amounts of sparse data have on reconstruction accuracy has not been systematically assessed. In this study, we compared shape model and linear scaling reconstruction of the full femur surface from varying proportions of proximal and distal partial femur geometry in combination with morphometric and landmark data. We quantified reconstruction error in terms of surface-to-surface error as well as deviations in the reconstructed femur’s anatomical coordinate system which is important for biomechanical models. Using a partial proximal femur surface, mean shape model-based reconstruction surface error was 1.8 mm with 0.15° or less anatomic axis error, compared to 19.1 mm and 2.7–5.6° for linear scaling. Similar results were found when using a partial distal surface. However, varying amounts of proximal or distal partial surface data had a negligible effect on reconstruction accuracy. Our results show that given an appropriate set of sparse geometric data, a shape model can reconstruct full femur geometry with far greater accuracy than simple scaling.

Computer-assisted 3D planned corrective osteotomies in eight malunited radius fractures.

In corrective osteotomy of the radius, detailed preoperative planning is essential to optimising functional outcome. However, complex malunions are not completely addressed with conventional preoperative planning. Computer-assisted preoperative planning may optimise the results of corrective osteotomy of the radius. We analysed the pre- and postoperative radiological result of computer-assisted 3D planned corrective osteotomy in a series of patients with a malunited radius and assessed postoperative function. We included eight patients aged 13–64 who underwent a computer-assisted 3D planned corrective osteotomy of the radius for the treatment of a symptomatic radius malunion. We evaluated pre- and postoperative residual malpositioning on 3D reconstructions as expressed in six positioning parameters (three displacements along and three rotations about the axes of a 3D anatomical coordinate system) and assessed postoperative wrist range of motion. In this small case series, dorsopalmar tilt was significantly improved (p = 0.05). Ulnoradial shift, however, increased by the correction osteotomy (6 of 8 cases, 75 %). Postoperative 3D evaluation revealed improved positioning parameters for patients in axial rotational alignment (62.5 %), radial inclination (75 %), proximodistal shift (83 %) and volodorsal shift (88 %), although the cohort was not large enough to confirm this by statistical significance. All but one patient experienced improved range of motion (88 %). Computer-assisted 3D planning ameliorates alignment of radial malunions and improves functional results in patients with a symptomatic malunion of the radius. Further development is required to improve transfer of the planned position to the intra-operative bone.Level of evidence IV.

Abnormal tibiofemoral contact mechanics in subjects with medial and lateral compartment articular cartilage lesions

s / Osteoarthritis and Cartilage 23 (2015) A82eA416 A306 481 ABNORMAL TIBIOFEMORAL CONTACT MECHANICS IN SUBJECTS WITH MEDIAL AND LATERAL COMPARTMENT ARTICULAR CARTILAGE LESIONS S.Y. Segev, D. Kumar, L. Nardo, V. Pedoia, T.M. Link, S. Majumdar, R.B. Souza. Univ. of California San Francisco, San Francisco, CA, USA Purpose: To evaluate the changes in cartilage-on-cartilage contact areas and medial and lateral contact area centroid movement in the tibiofemoral joint during knee flexion and extension using MRI in subjects with and without tibiofemoral cartilage lesion. Methods: Subjects from an observational study on knee Osteoarthritis (OA), including both subjects with andwithout radiographic OA, (n1⁄4 94 Mean age 1⁄4 54.1±10.5 years; Mean BMI 1⁄4: 24.4±3.4 kg/m2; Men:Women 1⁄4 35:59) underwent 2D fast-spin echo (FSE) MR imaging at 0 and 30 of knee flexion under axial loading (25% bodyweight). For subjects with radiographic OA, the more severe knee was enrolled. For subjects without radiographic OA, the enrolled knee was randomly selected. A fluid sensitive-fat-saturated 3D fast spin-echo sequence with variable flip angle (CUBE) was acquired in order to grade cartilage lesions using a semi-quantitative score. Subjects were then stratified into those with and without cartilage lesions at the tibiofemoral joint. Tibiofemoral contact area was defined on FSE images as the area of contact between the tibial and femoral articular cartilage, excluding meniscus contact area and joint fluid. This region of contact was semiautomatically segmented separately in the medial and lateral knee compartment using Bezier-splines created with in-house software written in Matlab. Contact area centroid position was determined by evaluation of the contact area on a defined anatomic coordinate system embedded within the tibia. Differences in medial and lateral contact area at flexed and extended conditions, and medial and lateral contact area centroid translations were compared between subjects with and without cartilage lesions using analysis of co-variance (ANCOVA), adjusted for age, gender, knee alignment, and BMI. Results: Subjects with medial compartment cartilage lesions (n1⁄428) had greater contact area in the affected compartment during extension (Figure 1, 361 vs. 270 mm2; p1⁄40.025), but not flexion (Figure 1, 287 vs. 219mm2; p1⁄40.146) when compared to subjects without lesions (n1⁄466). No differences in contact area in the lateral compartment were observed between subjects with and without medial compartment lesions. In contrast, subjects with lesions in the lateral compartment (n1⁄418) were found to have greater contact area than subjects without lesions (n1⁄476) in both extension (Figure 2, 366 vs. 271 mm2; p1⁄40.009) and flexion (Figure 2, 326 vs. 224 mm2; p1⁄40.002) as well as in the contralateral compartment while in full extension (Figure 2, 374 vs. 279 mm2; p1⁄40.012). With regard to contact kinematics, subjects with medial compartment lesions had greater anterior-posterior translation of the medial contact centroid when moving from extension to flexion (Figure 3, Figure 4, p1⁄40.047). No differences in anterior-posterior centroid translations were observed in either the medial or lateral compartment of subjects with lateral compartment lesions. Conclusions: Contact mechanics in subjects with cartilage lesions are significantly different compared to those without lesions. The higher contact area in subjects with cartilage lesions is likely due to the changes in the ability of the cartilage to adapt to loading, expanding the contact surface as the cartilage adjacent to the lesion gives way to the load. This phenomenon is coupled with abnormal contact kinematics in persons with cartilage lesions. While the normal kinematics of knee flexion requires the femur to slide back on the tibial plateau, our data suggests that the movement in the affected compartment is greater in knees with medial compartment cartilage lesions. This finding could be related to knee instability, an extremely common symptom in patients with OA. Taken together, these differences may be responsible for more rapid cartilage degeneration in individuals with OA. Abstracts / Osteoarthritis and Cartilage 23 (2015) A82eA416 A307s / Osteoarthritis and Cartilage 23 (2015) A82eA416 A307 482 SERUM LEVELS OF RESISTIN AND INTERLEUKIN-17 ARE ASSOCIATED WITH INCREASED CARTILAGE DEFECTS AND BONE MARROW LESIONS IN PATIENTS WITH KNEE SYMPTOMATIC OSTEOARTHRITIS K. Wang y, J. Xu y, J. Cai y, S. Zheng y, X. Yang y, C. Ding zy. yDept. of Rheumatology and Immunology, First Affiliated Hosp. of Anhui Med. Univ., Hefei, China; zMenzies Inst. of Med. Res., Univ. of Tasmania,

Analysis of the talocrural and subtalar joint motions in patients with medial tibial stress syndrome

BackgroundThe rearfoot motion during sports activities in patients with the medial tibial stress syndrome (MTSS) is unknown. This study aimed to investigate the difference in kinematics of the rearfoot in MTSS patients (eight male soccer players) and control participants (eight male soccer players) during a forward step.MethodsSixteen male soccer players, including eight players with MTSS, participated. Forward step trials were recorded with cineradiographic images obtained at a sampling rate of 60 Hz. Geometric bone models of the tibia and talus/calcaneus were created from computed tomography scans of the distal part of one lower limb. Following a combination of approaches, anatomical coordinate systems were embedded in each bone model. The talocrural joint motion (relative motion of the talus with respect to the tibia) and subtalar joint motion (relative motion of the calcaneus with respect to the talus) were examined.ResultsA significantly larger range of internal/external rotation and inversion/eversion motion was observed in the subtalar joint of MTSS patients compared to healthy controls (P < 0.05) from heel contact to heel off. There were no significant differences between the MTSS patients and healthy participants in the ranges of all talocrural joint angles during the forward step.ConclusionOur results indicate that the range of subtalar joint motion is greater in patients with MTSS during the stance phase of the forward step. The kinematic results obtained of this study may have important clinical implications and add quantitative data to an in vivo database of MTSS patients.

Fibular malalignment in individuals with chronic ankle instability.

Case series. To determine whether abnormal fibular alignment is present in individuals with chronic ankle instability (CAI) using 3-D analysis of computed tomography (CT)-based bone models. A positional difference of the distal fibula in individuals with unilateral CAI, when compared to the contralateral side, has been suggested. However, previous studies report no consistent pattern of fibular malalignment in the anteroposterior direction and, to our knowledge, no study has investigated mediolateral malalignment. Seventeen males with unilateral CAI (mean ± SD age, 21.0 ± 2.4 years) and no history of injury in the contralateral side were enrolled. Geometric bone models of the tibia and fibula were created from non-weight-bearing CT images, and anatomical coordinate systems were embedded in the tibia model. Bilateral tibiae were superimposed using a best-fit algorithm that moved the tibia to the position of best congruity, and the amount of side-to-side difference in position of the fibulae was measured. The anteroposterior and mediolateral positional difference of the fibula of the ankle with CAI relative to the contralateral ankle, for the distal 10 cm of the fibula length, was determined using a color-coded map. The fibula of the ankle with CAI was significantly more lateral (0.57-0.68 mm) than that of the contralateral healthy ankle at all reference points from distal 10 cm to the lateral malleolus. There was no significant difference in anteroposterior position between the healthy ankles and those with CAI. This study detected malalignment of the distal fibula in ankles with CAI in a non-weight-bearing position. The fibula of the ankles with CAI had a significantly more lateral position than that of the healthy ankles, which may contribute to recurrent lateral ankle sprain or giving-way episodes.

Center of pressure trajectory differences between shod and barefoot running

This study examined differences in center of pressure (COP) trajectories between shod and barefoot running. Ten habitually shod runners ran continuous laps under both shod and barefoot conditions. The COP trajectory was calculated in the global coordinate system but then transformed to the anatomic coordinate system of the foot. The anterior–posterior and medio-lateral positions and excursions of the COP, as well as the most medial location and percent stand at which it occurred were examined. Additionally, external eversion moments and ground reaction forces were assessed. Compared to the shod condition, in the barefoot condition the COP was located more anteriorly early in stance and the COP was located significantly more medially at most time points across stance. There were no differences in external eversion moments during early stance or peak ground reaction forces between conditions. Future studies on mechanical or epidemiological differences between shod and barefoot running may find the COP trajectory an informative parameter to examine.

Validation of an Anatomical Coordinate System for Clinical Evaluation of the Knee Joint in Upright and Closed MRI

A computerized method to automatically and spatially align joint axes of in vivo knee scans was established and compared to a fixed reference system implanted in a cadaver model. These computational methods to generate geometric models from static MRI images with an automatic coordinate system fitting proved consistent and accurate to reproduce joint motion in multiple scan positions. Two MRI platforms, upright and closed, were used to scan a phantom cadaver knee to create a three-dimensional, geometric model. The knee was subsequently scanned in several positions of knee bending in a custom made fixture. Reference markers fixed to the bone were tracked by an external infrared camera system as well as by direct segmentation from scanned images. Anatomical coordinate systems were automatically fitted to the segmented bone model and the transformations of joint position were compared to the reference marker coordinate systems. The tracked translation and rotation measurements of the automatic coordinate system were found to be below root mean square errors of 0.8 mm and 0.7°. In conclusion, the precision of the translation and rotational tracking is found to be sensitive to the scanning modality, albeit in upright or closed MRI, but still within comparative measures to previously performed studies. The potential to use segmented bone models for patient joint analysis could vastly improve clinical evaluation of disorders of the knee with continual application in future three-dimensional computations.

Anatomy Calibration of Inertial Measurement Unit Using a Principle Component Analysis

Recently, as a result of advances in technology, micro-electro-mechanical system (MEMS)based inertial measurement units (IMUs) have frequently been used for human motion analyses. While the output signal from an IMU is based on the sensor coordinate system (CS), it is necessary to express the signal in the body segment CS for clinical meaning. The offset between the sensor CS and anatomical CS needs to be determined. In this study, a calibration method that determines the orientation offset between a body segment and an IMU attached to the body segment was proposed. The angular velocity was measured while the body segment was rotated and processed using a principle component analysis to form the basis of the orientation offset. The proposed method was applied to calibrate an IMU attached to the forearm and evaluated for five young healthy subjects. Its performance showed reasonable repeatability (mean < 1.4°, SD < 0.8°).

Automatic construction of an anatomical coordinate system for three-dimensional bone models of the lower extremities – Pelvis, femur, and tibia

Automated methods for constructing patient-specific anatomical coordinate systems (ACSs) for the pelvis, femur and tibia were developed based on the bony geometry of each, derived from computed tomography (CT). The methods used principal axes of inertia, principal component analysis (PCA), cross-sectional area, and spherical and ellipsoidal surface fitting to eliminate the influence of rater's bias on reference landmark selection. Automatic ACSs for the pelvis, femur, and tibia were successfully constructed on each 3D bone model using the developed algorithm. All constructions were performed within 30s; furthermore, between- and within- rater errors were zero for a given CT-based 3D bone model, owing to the automated nature of the algorithm. ACSs recommended by the International Society of Biomechanics (ISB) were compared with the automatically constructed ACS, to evaluate the potential differences caused by the selection of the coordinate system. The pelvis ACSs constructed using the ISB-recommended system were tilted significantly more anteriorly than those constructed automatically (range, 9.6–18.8°). There were no significant differences between the two methods for the femur. For the tibia, significant differences were found in the direction of the anteroposterior axis; the anteroposterior axes identified by ISB were more external than those in the automatic ACS (range, 17.5–25.0°).

Open Knee: A Pathway to Community Driven Modeling and Simulation in Joint Biomechanics.

Computational modeling and simulation (M&amp;S) in biomechanics is extending its reach from research environments towards translational applications. In particular to the knee joint, finite element (FE) analysis has significant utility to understand joint and tissue function, explore pathological conditions and injury mechanisms, and investigate surgical interventions and implant performance [1]. Unfortunately, while FE models of joints, in particular of the knee, are ubiquitous in literature [1], they are not necessarily available publicly for the community to reuse and further develop. Further, community driven modeling can provide the opportunity for crowd-sourced review, modification, and validation to address clinical and research problems in knee biomechanics. Therefore, the goals of this study are to provide an overview of our approach for open development of knee joint modeling as a potential framework to overcome potential challenges of implementing citizen science in joint biomechanics.Open Knee project was launched to provide an accessible model for FE analysis of the tibiofemoral joint [2]. The model incorporates femur and tibia (rigid bodies); femoral and tibial cartilage (nearly incompressible neo-Hookean); medial and lateral menisci (Fung orthotropic hyperelastic with horn attachments as linear springs), and cruciate and collateral ligaments (transversely isotropic hyperelastic) [2]. Frictionless contact between articulating surfaces, cruciate ligaments, and if desired, collateral ligaments and bones, are defined. FEBio is utilized for simulations [3]; the model was tested for FEBio v1.3. Simulation scenarios include a fixed tibia, where flexion of femur is prescribed and all other degrees of freedom are free or kept under load control. An anatomical coordinate system describes knee kinematics [4]. A dynamic implicit time integration is used to obtain solutions.The data, upon which Open Knee was based on, includes joint level anatomical and mechanical measurements [5]. A cadaver specimen, right knee from a 70 years old female donor, was tested. Anatomical reconstruction was based on magnetic resonance images. Joint kinematics-kinetics were measured during laxity testing and for combined loading scenarios in a robotics system. Gross measurements of anterior cruciate ligament deformations are also available.Open Knee website (https://simtk.org/home/openknee) provides the infrastructure for open development. It is also used to disseminate data, models, scripts (for configuration and postprocessing), results, and documents.Various simulations were conducted using Open Knee to illustrate customization (menisectomy) and to evaluate predictive capacity of joint response (passive flexion) and tissue mechanics (anterior cruciate ligament). Disagreements were noted in predictions of proximal-distal translation at high flexion angles during passive flexion, and for anterior displacements and ligament deformations during anterior drawer. Despite its limitations, Open Knee enabled various other studies, e.g., multiscale simulations [6].Open Knee has been provided as a first openly developed and disseminated FE representation of a joint, specifically that of the tibiofemoral joint. While the model can be utilized for different purposes to explore knee joint biomechanics, various limitations do exist. An extensive specimen-specific evaluation of joint level response has not been conducted, and previous studies illustrated the limitations of Open Knee's predictive capacity. In addition, many modeling components are missing, e.g., the patellofemoral joint and representation of in situ ligament strains. Driven by these limitations, more comprehensive experimentation is in progress, including accurate registration of high-resolution image data with robotics joint testing, and specimen-specific joint and tissue characterization. With the help of the community, future explorations may be possible through sensitivity analysis and by studies confirming the adequacy of predictive capacity and attempting to answer scientific and clinical questions.Citizen science in joint biomechanics can be challenging. While many computational aspects can be conducted in a remote manner, experimentation requires facilities that impose geographical constraints. Nonetheless, the community can be involved to establish specifications of experiments and during the analysis of data. Another bottleneck is associated with the computational cost of simulations that may hinder community developers/users to test model features, assess performance and conduct scientific studies. It may be necessary to establish a web-based framework to publicly access high performance computing to conduct simulations on the cloud. The use of free and open source simulation software has utmost importance to allow anyone to conduct analysis. Last but not least, contributions may need to be incentivized through a support system. Development of such a comprehensive platform will promote public development and dissemination of knee models representative of healthy and pathologic conditions.Open Knee is supported by R01GM104139, NIGMS, NIH. Previous work was partly supported by R01EB009643, NIBIB, NIH (development), R01AR049735, NIAMS, NIH (data), and R01GM083925, NIGMS, NIH (FEBio). Project hosting is provided by Simbios. Contributions by Scott Sibole and Randy Heydon are appreciated.

Correlation Between Femoral Tunnel Length and Tunnel Position in ACL Reconstruction

The position of the femoral tunnel affects the osseous geometry available for drilling during anterior cruciate ligament (ACL) reconstruction. The length of the tunnel changes with changes in the tunnel position and may have implications for femoral fixation. Forty-seven patients with a single-bundle ACL reconstruction underwent computed tomography (CT) evaluation to generate three-dimensional (3D) CT bone models. With use of a previously described anatomic coordinate system, the center of the femoral tunnel was quantified in the posterior-anterior and proximal-distal dimensions on 3D CT. Tunnel length was defined as the distance between the centers of the intra-articular and extra-articular tunnel apertures. The reconstructed knees were dichotomized by anatomy and technique into anatomic (n = 20) and nonanatomic (n = 27) groups as well as according to whether they had undergone medial portal drilling (n = 20) or transtibial drilling (n = 27) for analysis. In addition, a review of the literature on the relationship between tunnel length and tendon-to-bone healing was performed. Femoral tunnels drilled with nonanatomic footprints were longer (mean [and standard deviation], 43.6 ± 8.5 mm; range, 28.2 to 60.7 mm) than tunnels drilled with anatomic footprints (31.0 ± 6.3 mm; 21.2 to 42.5 mm) (p &lt; 0.001). Tunnels drilled transtibially (44.4 ± 7.6 mm; 32.5 to 60.7 mm) were significantly longer than tunnels drilled through the medial portal (29.8 ± 5.0 mm; 21.2 to 40.3 mm) (p &lt; 0.001). There was a strong correlation between tunnel length and posterior-anterior femoral tunnel position (r = 0.78, p &lt; 0.05), with more anterior tunnel positioning associated with greater tunnel length. There was no correlation between posterior-distal femoral tunnel position and tunnel length (r = -0.05; p = 0.74). There was no consensus in the literature regarding adequate tunnel length for biologic fixation. Femoral tunnels drilled with anatomic footprints had sufficient length for adequate femoral fixation. Femoral tunnels positioned anterior to the native insertion of the ACL were longer than those in anatomic position. The results of this study can help the surgeon to consider the relationship between tunnel position and subsequent tunnel length in ACL reconstruction.

Comparative evaluation of scapular and humeral coordinate systems based on biomedical images of the glenohumeral joint

Bio-imaging techniques represent a powerful tool for shoulder joint biomechanical analysis. However, the restricted field of view may prevent the acquisition of complete scapula and humerus bone models and hence limiting the applicability of standardized anatomical coordinate system (ACS) definitions. The aim of this study was to propose ACS definitions for both scapula and humerus which can be implemented when limited portions of the relevant bones are available. Magnetic resonance (MR) images of twenty right humeri and scapulae were acquired. The proposed ACSs were assessed in terms of (1) sensitivity to bone morphological variation, (2) intra – and inter – operator repeatability and (3) consistency with the anatomical cardinal directions. A comparison with alternative ACS definitions was also performed. Overall, our ACS scapular proposal and that presented in Kedgley and Dunning (2010) were found to be the least sensitive to the morphometric variability (mean angular absolute deviation lower than 8.3deg) and they were characterized by a high intra – and inter – operator repeatability (mean angular absolute deviation lower than 1.5deg). The humeral ACS proposal showed a morphometric variability similar to Amadi et al. (2009b) (mean angular absolute deviation lower than 8.3deg) but a higher reproducibility. The scapular and humeral ACS mean angular deviation from the reference anatomical cardinal directions were smaller than 15deg and 8.6deg, respectively. The proposed scapular and humeral ACS definitions are therefore suitable to be applied when a limited portion of the glenohumeral joint is available as it may occur in standard shoulder clinical exams.

Automatic determination of an anatomical coordinate system for a three-dimensional model of the human patella

Measuring the in vivo 3-D kinematics of the patella requires a repeatable anatomical coordinate system (ACS). The purpose of this study was to develop an algorithm to determine an ACS using the patella's unique morphology.An ACS was automatically constructed that aligned the proximal/distal (PD) axis with the posterior vertical ridge. Inter-subject ACS repeatability was determined by registering all patellae and their associated ACSs to a reference patella.The mean angle between the reference patella ACS and each subject's axes was less than 2.5° and the 95% CI was 1.0°–4.0°.Here, we presented an anatomical coordinate system that is independent of the observer's subjective judgement or orientation of the knee within the scanner.

Myofascial trigger points and innervation zone locations in upper trapezius muscles

BackgroundMyofascial trigger points (MTrPs) are hyperirritable spots located in taut bands of muscle fibres. Electrophysiological studies indicate that abnormal electrical activity is detectable near MTrPs. This phenomenon has been described as endplate noise and it has been purported to be associated MTrP pathophysiology. Thus, it is suggested that MTrPs will be overlap the innervation zone (IZ). The purpose of this work was to describe the location of MTrPs and the IZ in the right upper trapezius.MethodsWe screened 71 individuals and eventually enrolled 24 subjects with neck pain and active MTrPs and 24 neck pain-free subjects with latent MTrPs. Surface electromyography (sEMG) signals were detected using an electrode matrix during isometric contraction of the upper trapezius. A physiotherapist subsequently examined the subject’s trapezius to confirm the presence of MTrPs and establish their location. IZ locations were identified by visual analysis of sEMG signals. IZ and MTrPs locations were described using an anatomical coordinate system (ACS), with the skin area covered by the matrix divided into four quadrants.ResultsNo significant difference was observed between active and latent MTrPs locations (P = 0.6). Forty-five MTrPs were in the third quadrant of the ACS, and 3 were included in second quadrant. IZs were located approximately midway between the seventh cervical vertebrae and the acromial angle in a limited area in the second and third quadrants. The mean distance between MTrP and IZ was 10.4 ± 5.8 mm.ConclusionsAccording to the acquired results, we conclude that IZ and MTrPs are located in well-defined areas in upper trapezius muscle. Moreover, MTrPs in upper trapezius are proximally located to the IZ but not overlapped.

Non-directional radial intercalation dominates deep cell behavior during zebrafish epiboly

SummaryEpiboly is the first coordinated cell movement in most vertebrates and marks the onset of gastrulation. During zebrafish epiboly, enveloping layer (EVL) and deep cells spread over the vegetal yolk mass with a concomitant thinning of the deep cell layer. A prevailing model suggests that deep cell radial intercalations directed towards the EVL would drive deep cell epiboly. To test this model, we have globally recorded 3D cell trajectories for zebrafish blastomeres between sphere and 50% epiboly stages, and developed an image analysis framework to determine intercalation events, intercalation directionality, and migration speed for cells at specific positions within the embryo. This framework uses Voronoi diagrams to compute cell-to-cell contact areas, defines a feature-based spatio-temporal model for intercalation events and fits an anatomical coordinate system to the recorded datasets. We further investigate whether epiboly defects in MZspg mutant embryos devoid of Pou5f1/Oct4 may be caused by changes in intercalation behavior. In wild-type and mutant embryos, intercalations orthogonal to the EVL occur with no directional bias towards or away from the EVL, suggesting that there are no directional cues that would direct intercalations towards the EVL. Further, we find that intercalation direction is independent of the previous intercalation history of individual deep cells, arguing against cues that would program specific intrinsic directed migration behaviors. Our data support a dynamic model in which deep cells during epiboly migrate into space opening between the EVL and the yolk syncytial layer. Genetic programs determining cell motility may control deep cell dynamic behavior and epiboly progress.

SU‐E‐T‐689: Effects of Coordinate System Orientation On ICRU Bladder Point Dose

Purpose: To quantify the displacement and dosimetric errors on position of the ICRU bladder point due to coordinate system orientation in gynecological HDR procedures. Methods: Eight patients (23 treatment fractions) receiving HDR brachytherapy for gynecological malignancies were evaluated. Bladder points were placed for each of two coordinate systems (ICRU and applicator) for each patient fraction. The ICRU coordinate system refers to true anatomical orientations (e.g., ant/post) while the applicator coordinate system is transformed (translated and rotated) based on the location and orientation treatment applicator and is used to define prescription points and optimize planned dose distributions. In both cases, the ICRU bladder point definition was used to place the point (most posterior point of foley balloon on lateral image and center of foley balloon on AP image) with differences resulting from definition of coordinate system orientation. The displacement in three dimensions and point dose differences were calculated for each patient fraction. Results: Point displacement of the applicator coordinate system point (Bappl) relative to the ICRU point (BICRU) was 6.3 ± 0.7 mm (mean ± std err) with a range of 1.5 to 12.6 mm, a statistically significant Result. Dosimetrically, dose to Bappl was 7.3 ± 1.6% (mean ± std err) of the prescribed dose higher than BICRU with a range of −7.9 to 24.7%, a statistically and clinically significant Result. This results in an overestimation of bladder dose when using the applicator coordinate system and using ICRU point dose criteria for plan evaluation. Conclusion: Failure to use a true anatomical coordinate system can lead to statistically and clinically significant dosimetric errors in dose to the defined bladder point. Use of the applicator coordinate system to define the bladder point can potentially cause compromises in plan quality in attempting to meet normal tissue dose tolerances evaluated with incorrectly reported doses.

Anatomical coordinate systems for high-resolution scapula and humerus models

Anatomical coordinate systems for high-resolution scapula and humerus models

Registration of challenging pre-clinical brain images

The size and complexity of brain imaging studies in pre-clinical populations are increasing, and automated image analysis pipelines are urgently required. Pre-clinical populations can be subjected to controlled interventions (e.g., targeted lesions), which significantly change the appearance of the brain obtained by imaging. Existing systems for registration (the systematic alignment of scans into a consistent anatomical coordinate system), which assume image similarity to a reference scan, may fail when applied to these images. However, affine registration is a particularly vital pre-processing step for subsequent image analysis which is assumed to be an effective procedure in recent literature describing sophisticated techniques such as manifold learning. Therefore, in this paper, we present an affine registration solution that uses a graphical model of a population to decompose difficult pairwise registrations into a composition of steps using other members of the population. We developed this methodology in the context of a pre-clinical model of stroke in which large, variable hyper-intense lesions significantly impact registration performance. We tested this technique systematically in a simulated human population of brain tumour images before applying it to pre-clinical models of Parkinson's disease and stroke.