Position Of Anatomical Landmarks Research Articles

Evaluation of anatomical landmark position differences between respiration-gated MRI and four-dimensional CT for radiation therapy in patients with hepatocellular carcinoma

To measure the accuracy of position differences in anatomical landmarks in gated MRI and four-dimensional CT (4D-CT) fusion planning for radiation therapy in patients with hepatocellular carcinoma (HCC). From April to December 2009, gated MR and planning 4D-CT images were obtained from 53 inoperable HCC patients accrued to this study. Gated MRI and planning 4D-CT were conducted on the same day. Manual image fusions were performed by matching the vertebral bodies. Liver volumes and three specific anatomical landmarks (portal vein conjunction, superior mesenteric artery bifurcation, and other noticeable points) were contoured from each modality. The points chosen nearest the centre of the four landmark points were compared to measure the accuracy of fusion. The average distance differences (±standard deviation) of four validation points were 5.1 mm (±4.6 mm), 5.6 mm (±6.2 mm), 5.4 mm (±4.5 mm) and 5.1 mm (±4.8 mm). Patients who had ascites or pulmonary disease showed larger discrepancies. MRI-CT fusion discrepancy was significantly correlated with positive radiation response (p<0.05). Approximately 5-mm anatomical landmark positional differences in all directions were found between gated MRI and 4D-CT fusion planning for HCC patients; the gap was larger in patients with ascites or pulmonary disease. There were discrepancies of approximately 5 mm in gated MRI-CT fusion planning for HCC patients.

The Human Knee: Gross, Microscopic, Surgical, and Radiological Anatomy

The Human Knee: Gross, Microscopic, Surgical, and Radiological Anatomy

Application of Soft Tissue Artifact Compensation Using Displacement Dependency between Anatomical Landmarks and Skin Markers

Soft tissue artifact is known to be one of the main sources of errors in motion analysis by means of stereophotogrammetry. Among many approaches to reduce such errors, one is to estimate the position of anatomical landmarks during a motion with joint angle or displacement of skin markers, which is the so-called compensation method of anatomical landmarks. The position of anatomical landmarks was modeled from the data of the so-called dynamic calibration, in which anatomical landmark positions are calibrated in an ad hoc motion. This study aimed to apply the compensation methods with joint angle and skin marker displacement to three lower extremity motions (walking, sit-to-stand/stand-to-sit, and step up/down) in ten healthy males and compare their reliability. To compare the methods, two sets of kinematic variables were calculated using two different marker clusters, and the difference was obtained. Results showed that the compensation method with skin marker displacement had less differences by 30–60% compared to without compensation. In addition, it had significantly less difference in some kinematic variables (7 of 18) by 25–40% compared to the compensation method with joint angle.

Highlights in DD

“Highlights” calls attention to exciting advances in developmental biology that have recently been reported in Developmental Dynamics. Development is a broad field encompassing many important areas. To reflect this fact, the section spotlights significant discoveries that occur across the entire spectrum of developmental events and problems: from new experimental approaches, to novel interpretations of results, to noteworthy findings utilizing different developmental organisms. Leveling the playing field (New Frontiers in Cell Competition by Simon de Beco, Marcello Ziosi, and Laura A. Johnston, Dev Dyn 241:831–841) In a world that is competitive by nature, even cells elbow out the weak. In cell competition, cells get the stats on the their neighbors' fitness by sensing and responding to their growth rates. “Losing”&&num;148; cells undergo apoptosis, regulating overall organ homeostasis and growth, a process most intensely studied in growing Drosophila epithelia. This review details recent experiments that identify new players that make the fight possible, including the membrane protein Flower, the extracellular protein Sparc, the signaling molecule Wg, and the Hippo-Salvador-Warts pathway. Recent data support the hypothesis that cell competition also plays a physiological role in mammalian hematopoietic cells. However there is at least one key difference: “losers”&&num;148; undergo senescence rather than apoptosis. Future directions include a thorough comparison between Drosophila and mammalian cell competition, and how the process fits into other pathways such as stress resistance, stem cell expansion, and normal development. Progress will come from cooperation between mammalian and Drosophila investigators—not competition. It's normal (Normalized Shape and Location of Perturbed Craniofacial Structures in the Xenopus Tadpole Reveal an Innate Ability to Achieve Correct Morphology by Laura N. Vandenberg, Dany S. Adams, and Michael Levin, Dev Dyn 241:863–878) Embryos are incredibly forgiving. At later stages, there may be no signs of an injury sustained in early development. To gain insights into this phenomenon Vandenberg et. al, used geometric morphometric analytical techniques to determine how relative positions of Xenopus anatomical landmarks change over time following induced craniofacial perturbations. They note that while all tissues observed eventually end up back in their normal locations, the morphology of some tissues (cranial neural crest derived jaw and branchial arch) are more easily repaired than others (ectodermal placode derived—eye, nose). Further, reaching a target position is a dynamic process governed by a structure's position relative to stable reference points (distance from brain and angle from midline). The authors suggest a model in which a craniofacial structure senses its position based on signals sent between it and an “organizing center.” Uncovering the precise nature of this exchange has implications for repair of birth defects, organ regeneration, and insults sustained during adulthood.

Validity of the Microsoft Kinect for assessment of postural control

Clinically feasible methods of assessing postural control such as timed standing balance and functional reach tests provide important information, however, they cannot accurately quantify specific postural control mechanisms. The Microsoft Kinect™ system provides real-time anatomical landmark position data in three dimensions (3D), and given that it is inexpensive, portable and simple to setup it may bridge this gap. This study assessed the concurrent validity of the Microsoft Kinect™ against a benchmark reference, a multiple-camera 3D motion analysis system, in 20 healthy subjects during three postural control tests: (i) forward reach, (ii) lateral reach, and (iii) single-leg eyes-closed standing balance. For the reach tests, the outcome measures consisted of distance reached and trunk flexion angle in the sagittal (forward reach) and coronal (lateral reach) planes. For the standing balance test the range and deviation of movement in the anatomical landmark positions for the sternum, pelvis, knee and ankle and the lateral and anterior trunk flexion angle were assessed. The Microsoft Kinect™ and 3D motion analysis systems had comparable inter-trial reliability (ICC difference=0.06±0.05; range, 0.00–0.16) and excellent concurrent validity, with Pearson's r-values >0.90 for the majority of measurements (r=0.96±0.04; range, 0.84–0.99). However, ordinary least products analyses demonstrated proportional biases for some outcome measures associated with the pelvis and sternum. These findings suggest that the Microsoft Kinect™ can validly assess kinematic strategies of postural control. Given the potential benefits it could therefore become a useful tool for assessing postural control in the clinical setting.

Direct Kinematic Modeling of the Upper Limb During Trunk-Assisted Reaching

The study proposes a rigid-body biomechanical model of the trunk and whole upper limb including scapula and the test of this model with a kinematic method using a six-dimensional (6-D) electromagnetic motion capture (mocap) device. Large unconstrained natural trunk-assisted reaching movements were recorded in 7 healthy subjects. The 3-D positions of anatomical landmarks were measured and then compared to their estimation given by the biomechanical chain fed with joint angles (the direct kinematics). Thus, the prediction errors was attributed to the different joints and to the different simplifications introduced in the model. Large (approx. 4 cm) end-point prediction errors at the level of the hand were reduced (to approx. 2 cm) if translations of the scapula were taken into account. As a whole, the 6-D mocap seems to give accurate results, except for prono-supination. The direct kinematic model could be used as a virtual mannequin for other applications, such as computer animation or clinical and ergonomical evaluations.

Automated anatomical demarcation using an active shape model for videofluoroscopic analysis in swallowing

The current gold standard method in the clinical assessment of swallowing is the visual inspection of videofluoroscopic frames. Specific clinical measurements are estimated based on various anatomical and bolus positional information with respect to time (or frame number). However, due to the subjective nature of visual inspection clinicians face intra- and inter-observer repeatability issues and bias when making these estimations. The correct demarcations of reference lines highlighting the positions of important anatomical landmarks would serve as a visual aid and could also be used in conjunction with bolus detection methods to objectively determine these desirable measurements. In this paper, we introduce and test the reliability of applying a 16-point Active Shape Model as a deformable template to demarcate the boundaries of salient anatomical boundaries with minimal user input. A robust end and corner point detection algorithm is also used to provide image information for the suggested movement of the template during the fitting stage. Results show the model deformation constraints calculated from a training set of images are clinically coherent. The Euclidean distances between the fitted model points against their corresponding target points were measured. Test images were taken from two different data sets from frames acquired using two different videofluoroscopy units. Overall, fitting was found to be more reliable on the vertebrae and inferior points of the larynx compared to the superior laryngeal points and hyoid bone, with the model always fitting the C7 vertebra with discrepancies no higher than a distance of 23 pixels (3.2% of the image width, approximately 7.6 mm).

Kinematic self retargeting: A framework for human pose estimation

This paper presents a model-based, Cartesian control theoretic approach for estimating human pose from a set of key features points (key-points) detected using depth images obtained from a time-of-flight imaging device. The key-points represent positions of anatomical landmarks, detected and tracked over time based on a probabilistic inferencing algorithm that is robust to partial occlusions and capable of resolving ambiguities in detection. The detected key-points are subsequently kinematically self retargeted, or mapped to the subject’s own kinematic model, in order to predict the pose of an articulated human model at the current state, resolve ambiguities in key-point detection, and provide estimates of missing or intermittently occluded key-points. Based on a standard kinematic and mesh model of a human, constraints such as joint limit avoidance, and self-penetration avoidance are enforced within the retargeting framework. Effectiveness of the algorithm is demonstrated experimentally for upper and full-body pose reconstruction from a small set of detected key-points. On average, the proposed algorithm runs at approximately 10 frames per second for the upper-body and 5 frames per second for whole body reconstruction on a standard 2.13 GHz laptop PC.

Obesity and dentistry: a growing problem

Obesity has increased at an alarming rate in recent years. It is now a worldwide public health problem. The World Health Organisation (WHO) classifies obesity as a chronic disease. Affected individuals are at increased risk of hypertension, heart disease and other illnesses. There are also important social implications.Within dentistry and particularly in the provision of conscious sedation, obesity can be a potential complicating factor. For example, the position of anatomical landmarks may be less obvious if surrounded by fatty tissue. Very obese patients may be housebound or have difficulty accessing dental surgeries. Dental chairs may not be of an appropriate design to accommodate some obese patients. However, little information or advice on this topic is available in the literature.This article reviews obesity from a dental perspective. Challenges in providing dental care for obese patients are identified and practical recommendations made for their management.

MRI development and validation of two new predictive methods of glenohumeral joint centre location identification and comparison with established techniques

Identification of the centre of the glenohumeral joint (GHJ) is essential for three-dimensional (3D) upper limb motion analysis. A number of convenient, yet un-validated methods are routinely used to estimate the GHJ location in preference to the International Society of Biomechanics (ISB) recommended methods. The current study developed a new regression model, and simple 3D offset method for GHJ location estimation, employing easy to administer measures, and compared the estimates with the known GHJ location measured with magnetic resonance imaging (MRI). The accuracy and reliability of the new regression and simple 3D offset techniques were compared with six established predictive methods. Twenty subjects wore a 3D motion analysis marker set that was also visible in MRI. Immediately following imaging, they underwent 3D motion analysis acquisition. The GHJ and anatomical landmark positions of 15 participants were used to determine the new regression and simple 3D generic offset methods. These were compared for accuracy with six established methods using 10 subject's data. A cross validation on 5 participants not used for regression model development was also performed. Finally, 10 participants underwent a further two MRI's and subsequent 3D motion analysis analyses for inter-tester and intra-tester reliability quantification. When compared with any of the other established methods, our newly developed regression model found an average GHJ location closer to the actual MRI location, having an GHJ location error of 13±2mm, and had significantly lower inter-tester reliability error, 6±4mm (p<0.01).

Running biomechanics: shorter heels, better economy

Better running economy (i.e. a lower rate of energy consumption at a given speed) is correlated with superior distance running performance. There is substantial variation in running economy, even among elite runners. This variation might be due to variation in the storage and reutilization of elastic energy in tendons. Using a simple musculoskeletal model, it was predicted that the amount of energy stored in a tendon during a given movement depends more critically on moment arm than on mechanical properties of the tendon, with the amount of stored energy increasing as the moment arm gets smaller. Assuming a link between elastic energy reutilization and overall metabolic cost of running, a smaller moment arm should therefore be associated with superior running economy. This prediction was confirmed experimentally in a group of 15 highly trained runners. The moment arm of the Achilles tendon was determined from standardized photographs of the ankle, using the position of anatomical landmarks. Running economy was measured as the rate of metabolic energy consumption during level treadmill running at a speed of 16 km h(-1). A strong correlation was found between the moment arm of the Achilles tendon and running economy. Smaller muscle moment arms correlated with lower rates of metabolic energy consumption (r(2)=0.75, P<0.001).

Soft tissue artifact compensation using displacement dependency between anatomical landmarks and skin markers – a preliminary study

Soft tissue artifact is known to be one of the principal sources of errors using human motion analysis by means of stereophotogrammetry. As one of the ways to reduce such errors, Lucchetti, L., Cappozo, A., Cappello, A., Croce, U.D. [1998. Skin movement artefact assessment and compensation in the estimation of knee-joint kinematics. Journal of Biomechanics 31, 977–984] proposed the so-called dynamic calibration in which anatomical landmark positions are calibrated in an ad hoc motion after which they are compensated with joint angles in a motor task. However, the method was proven partially inefficient during the repetitive calculation of joint angles for anatomical landmark compensation. The present study herein attempted to offset the anatomical landmark position by using a skin marker displacement as an alternative to the compensation method with joint angles. The feasibility of the proposed method was tested by analyzing the knee motions of a patient wearing an external fixator on the shank. Its performance was later compared with the compensation method with joint angles. In the test, the proposed method was identified as effective in reducing soft tissue artifact errors by 40–80%. The errors of some of kinematic variables were significantly reduced by 25–60% compared to the compensation method with joint angles. Relevance to industry Motion analysis with stereophotogrammetry is utilized for various purposes, including clinical diagnosis, product design, and workload assessment. However, it has been known to accommodate significant errors due to the deformation of soft tissues such as those in the skin and muscles. Methods known to efficiently reduce errors due to the soft tissues are required to improve the utilization of motion analysis. The proposed method simplifies the procedure in reducing the error, and it can be implemented more easily during routine lower extremity motion analysis. But an application of this method during measurements of motions at workplaces would require a validation of the method based on scientific standards.

Postural Characteristics of Adolescents With Idiopathic Scoliosis

The objectives of this study were to compare the postural characteristics of idiopathic scoliosis (IS) patients with different types of spinal curvature and to compare a motion capture and a sequential digitization technique to estimate the postural characteristics of the IS patients. A total of 57 IS patients underwent a radiological, clinical, and postural geometric evaluations in an upright standing position as part of their regular follow-up. The posteroanterior radiograph of the trunk was used to measure the amplitude of spinal curvature. The postural evaluation was performed using a motion capture and sequential digitization technique providing the necessary 3-dimensional positions of anatomical landmarks. These landmarks were used to calculate postural parameters defining the position and orientation of the pelvis, shoulders, and shoulder blades. These measurements included lateral shift and angular measures of rotation and tilt. Significant differences in the frontal and transverse planes were found between the right thoracic (RTh), left thoracolumbar, and RTh-left lumbar (RThLL) patients. These characteristics were most prominent in the transverse plane for RTh patients, in the frontal plane for left thoracolumbar patients, and in the frontal and transverse planes for the RThLL lumbar patients. A strong positive intraclass correlation was also found between the parameters estimated with the motion capture system and with the sequential digitization system. Unique postural characteristics that are related to the type of the spinal curvature are evident in adolescents who have IS. Further work is necessary to assess how these measures may be used to monitor the progression of the spinal deformity. Quantifying the postural alignment of IS patients using surface anthropometric landmarks provides an opportunity to characterize the unique postural attributes that accompany each type of spinal curvature.

Estimation of the centre of mass for the study of postural control in Idiopathic Scoliosis patients: a comparison of two techniques

The objective of the present study is to quantify the position of the Centre of Mass (COM) during quiet standing using a force plate and compare this technique to the quantification of the COM with an anthropometric model. The postural control of 18 healthy adolescents and 22 IS patients was evaluated using an Optotrak 3D kinematic system, and two AMTI force plates during quiet standing. The position of anatomical landmarks tracked by the Optotrak system served to estimate the position of the COM of both groups using an anthropometric model (COM(anth)). The force plate served to estimate the position of the COM through double integration of the horizontal ground reaction forces (COM(gl)). The mean position and root mean square (RMS) amplitude of COM(gl, )in reference to the base of support (BOS) and the first sacral prominence (S1) were quantified in the Anterior-Posterior (A/P) and Medial-Lateral (M/L) directions. There was a significant difference between the control subjects and IS patients for the displacement of the COM(gl) in reference to the BOS in both the A/P and M/L directions. There was no difference between groups for the mean position of the COM(gl), however, 63% of the IS and 43% of the controls had a lateral position of the COM(gl )in reference to S1 of greater than 5 mm. There was a significant difference between groups in the A/P and M/L directions for the amplitude of error between the COM(gl) and COM(anth) techniques.

Aerodynamic force generation, performance and control of body orientation during gliding in sugar gliders (Petaurus breviceps)

Gliding has often been discussed in the literature as a possible precursor to powered flight in vertebrates, but few studies exist on the mechanics of gliding in living animals. In this study I analyzed the 3D kinematics of sugar gliders (Petaurus breviceps) during short glides in an enclosed space. Short segments of the glide were captured on video, and the positions of marked anatomical landmarks were used to compute linear distances and angles, as well as whole body velocities and accelerations. From the whole body accelerations I estimated the aerodynamic forces generated by the animals. I computed the correlations between movements of the limbs and body rotations to examine the control of orientation during flight. Finally, I compared these results to those of my earlier study on the similarly sized and distantly related southern flying squirrel (Glaucomys volans). The sugar gliders in this study accelerated downward slightly (1.0+/-0.5 m s(-2)), and also accelerated forward (2.1+/-0.6 m s(-2)) in all but one trial, indicating that the body weight was not fully supported by aerodynamic forces and that some of the lift produced forward acceleration rather than just balancing body weight. The gliders used high angles of attack (44.15+/-3.12 degrees ), far higher than the angles at which airplane wings would stall, yet generated higher lift coefficients (1.48+/-0.18) than would be expected for a stalled wing. Movements of the limbs were strongly correlated with body rotations, suggesting that sugar gliders make extensive use of limb movements to control their orientation during gliding flight. In addition, among individuals, different limb movements were associated with a given body rotation, suggesting that individual variation exists in the control of body rotations. Under similar conditions, flying squirrels generated higher lift coefficients and lower drag coefficients than sugar gliders, yet had only marginally shallower glides. Flying squirrels have a number of morphological specializations not shared by sugar gliders that may help to explain their greater lift generating performance.

Rotational and translational reproducibility of newly developed Leksell frame-based relocatable fixation system

The aim of this study was to evaluate three-dimensional movement of the cranium in a relocatable frame using positions of anatomical landmarks obtained from repeated quality-assurance (QA) computed tomography (CT) studies. We analyzed 17 series of QA-CT data representing five patients who underwent stereotactic radiotherapy for treatment of acoustic neurinoma. Helical-CT scans with 1-mm collimation were obtained at the time of treatment planning and during the course of treatment. The right and left short processes of the incus and the top of the crista galli were used as the three anatomical reference points. Fluctuations in distance among the reference points were all <1 mm. The translational displacements for these points were <2 mm, with standard deviations (SD) of <2 mm. A plane that included all three reference points was defined as the reference plane. To investigate the direction of cranial rotation for each QA-CT scan, unit normal vectors of the reference plane were obtained. Three-dimensional analyses indicated that cranial rotation was greatest along the X-axis, followed by the Y-axis, with the least rotation along the Z-axis. The result suggested that movement of the craniocaudal axis in the sagittal plane was a major factor behind displacement of the cranium.

Anatomical reliability of two fundamental radiological and clinical pelvic parameters: incidence and thickness

Reliability and reproducibility of two radiological pelvic parameters are tested: thickness (length of the segment defined by the middle of the upper endplate of the sacrum to the middle of the bi-coxo-femoral axis) and pelvic incidence (angle defined by the perpendicular line to the centre of the upper endplate of the sacrum and the thickness line). These two parameters provide a pelvis description and assess the relation between pelvis and spinal curves. The anatomical reliability of these radiological parameters was not achieved. The values of these two parameters from X-ray versus direct measurement on 12 anatomical specimens are compared. The direct measurement was performed by means of an electromagnetic Fastrak system (Polhemus society) providing 3D position of anatomical landmarks and allowing to measure the incidence and the thickness. These parameters were also measured from sagittal X-ray. Their values were compared. Incidence: the paired t-test and the variance ratio test were not statistically significant and a highly significant positive correlation existed between anatomical and radiological values (r=0.98; P<0.001). Thickness: the paired t-test was significant (P<0.01). There was a negative correlation between anatomical values of incidence and thickness (r= −0.54; P<0.05) but not for radiological values. A strong correlation exists which validates the radiological measurement of an angle, i.e. incidence, although there is a lack of reliability of the X-ray measurement of a distance, i.e. thickness, which is due to technical conditions of the X-ray examination. The results of this study suggest that in daily practice the X-ray measurement of the incidence only may be considered as an accurate indicator of pelvis morphology for the study of relations between pelvis anatomy and spinal curves (e.g., lordosis, scoliosis, spondylolisthesis).

Estimation of anatomical landmark positions from model of 3-dimensional foot by the FFD method

This paper proposes a method of estimation of the anatomical landmarks that are needed in product design from point clouds of body shape measured by a three-dimensional scanner. The algorithm is de...

Estimation of anatomical landmark positions from model of 3‐dimensional foot by the FFD method

AbstractThis paper proposes a method of estimation of the anatomical landmarks that are needed in product design from point clouds of body shape measured by a three‐dimensional scanner. The algorithm is described briefly. First, the standard model is defined as the average shape with anatomical landmarks calculated from multiple body data samples with given anatomical landmarks. Then, the matching transformation is applied to the standard model so that it fits the body shape data of the target model. The anatomical landmarks of the target body shape are estimated from the deformed standard model. Free‐form deformation (FFD) is used as the matching transformation, in which the deformation control lattice coordinates are determined from an estimation formula derived by multiple regression analysis of the multiple body data sample. This method is applied to a foot model for shoe design. The effectiveness of the proposed method is verified by an experimental evaluation. © 2005 Wiley Periodicals, Inc. Syst Comp Jpn, 36(6): 26–38, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.20270

Human movement analysis using stereophotogrammetry

Estimating the effects of different sources of error on joint kinematics is crucial for assessing the reliability of human movement analysis. The goal of the present paper is to review the different approaches dealing with joint kinematics sensitivity to rotation axes and the precision of anatomical landmark determination. Consistent with the previous papers in this series, the review is limited to studies performed with video-based stereophotogrammetric systems. Initially, studies dealing with estimates of precision in determining the location of both palpable and internal anatomical landmarks are reviewed. Next, the effects of anatomical landmark position uncertainty on anatomical frames are shown. Then, methods reported in the literature for estimating error propagation from anatomical axes location to joint kinematics are described. Interestingly, studies carried out using different approaches reported a common conclusion: when joint rotations occur mainly in a single plane, minor rotations out of this plane are strongly affected by errors introduced at the anatomical landmark identification level and are prone to misinterpretation. Finally, attempts at reducing joint kinematics errors due to anatomical landmark position uncertainty are reported. Given the relevance of this source of errors in the determination of joint kinematics, it is the authors' opinion that further efforts should be made in improving the reliability of the joint axes determination.