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Ligament properties in the literature are variable, yet scarce, but needed to calibrate computational models for spine clinical research applications. A comparison of ligament stiffness properties and their effect on the kinematic behavior of a thoracic functional spinal unit (FSU) is examined in this paper. Six unique ligament property sets were utilized within a volumetric T7-T8 finite element (FE) model developed using computer-aided design (CAD) spinal geometry. A 7.5 Nm moment was applied along three anatomical planes both with and without costovertebral (CV) joints present. Range of Motion (RoM) was assessed for each property set and compared to published experimental data. Intact and serial ligament removal procedures were implemented in accordance with experimental protocol. The variance in both kinematic behavior and comparability with experimental data among property sets emphasizes the role nonlinear characterization plays in determining proper kinematic behavior in spinal FE models. Additionally, a decrease in RoM variation among property sets was exhibited when the model setup incorporated the CV joint. With proper assessment of the source and size of each ligament, the material properties considered here could be expanded and justified for implementation into thoracic spine clinical studies.

Spinal surgical procedures often require release of intervertebral discs and ligaments to optimally achieve postural correction on a patient-specific basis. In this paper, a T7-T8 Finite Element (FE) model is utilized to examine internal load sharing during resection steps performed in a Ponte osteotomy. The FE model was rotated bidirectionally along three anatomical planes using an externally applied moment. In each step, the Ranges of Motion (RoM), Instantaneous Centers of Rotation (ICR), and forces from ligaments, discs, facet, and costovertebral joints were calculated. The product of each component’s force and the distance between the ICR and their position were used to calculate percent load sharing at the maximum moment magnitude. Removal of the facet joints accounts for overall significant increases in load sharing to the intervertebral disc, with maximum values reported in extension by approximately 18 percent and axial rotation by 16 percent. This study highlights key spine components whose kinematic influence may be considered to achieve desired surgical outcomes.

Cardiac auscultation (CA), the act of listening to the heart’s sound, is a critical skill that provides valuable information for identifying serious heart diseases. Proficiency in cardiac auscultation requires repeated stethoscope practice and experience in identifying abnormal or irregular cardiac rhythms. However, nowadays, most hospital admissions are short and intensely focused, with fewer opportunities for medical trainees to learn and practice bedside examination skills. It is common practice in many institutions to incorporate standardized patients (SPs) into CA training because these actors are able to represent the patient and convey the symptoms. However, SPs are typically healthy individuals, limiting the kinds of abnormalities that students can hear. In this work, we develop a novel real-time simulation-based method for virtual pathology stethoscope (VPS) detection. The VPS system uses augmented reality (AR) to teach medical students how to perform cardiac examinations by listening to abnormal heart sounds in SPs who are otherwise healthy. A digital stethoscope with two electrodes on the chest piece collects electrocardiogram (ECG) signal data sets from SPs at the four primary auscultation sites. Next, different deep-learning methods are evaluated for classifying the location of the stethoscope by taking advantage of subtle differences in the ECG signals. This study would significantly extend the simulation capabilities of SPs by allowing medical students and trainees to perform realistic CA and hear CA in a clinical environment.

Background: Mutations in the gene KCNH2 have been associated with both Short and Long QT syndrome. In this study, we identified a 1-day old infant that exhibited T-wave alternans coupled with Long QT Syndrome leading to aborted sudden infant death. Methods: Genetic analysis of the patient revealed a mutation in KCNH2 resulting in a proline to leucine substitution at position 632 (P632L). Functional electrophysiological studies were performed with the hERG mutation transiently transfected into either Human Embryonic Kidney (HEK) cells or human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). The functional effects of P632L were incorporated into biophysical computational models of hiPSC-CM as well as adult human cardiomyocytes to further assess its arrhythmogenic potential. Results: The male infant displayed multiple repolarization disorders including T-wave alternans and a QTc =510 ms that appeared 1 day after birth. Genetic screening revealed a heterozygous missense mutation (P632L) in KCNH2 in the infant. Patch clamp analysis of HEK cells transiently transfected with P632L mutation showed a complete loss of function of HERG current compared to WT HERG. Transient transfection of P632L into WT hiPSC myocytes resulted in prolongation of the hiPSC action potential compared to untransfected hiPSC myocytes. Co-transfection of WT and non-functional P632L channels into HEK cells resulted in a dramatic loss of current suggesting a dominant negative effect. Implementing the effects of a complete block of HERG current in the hiPSC-CM computer model prolonged the action potential by 45% and depolarized the resting membrane potentials. In adult human myocyte models, the effects of HERG blockade were more severe in Purkinje cells than that in ventricular myocytes (71% vs. 16% APD prolongation, respectively). Conclusions: The mutation P632L causes a complete loss of HERG current and results in QT prolongation. Numerical simulations suggest a more severe phenotype in Purkinje cells than in ventricular myocytes which could be proarrhythmic.

An error-controlled mesh refinement procedure for needle insertion simulations is presented. As an example, the procedure is applied for simulations of electrode implantation for deep brain stimulation. We take into account the brain shift phenomena occurring when a craniotomy is performed. We observe that the error in the computation of the displacement and stress fields is localised around the needle tip and the needle shaft during needle insertion simulation. By suitably and adaptively refining the mesh in this region, our approach enables to control, and thus to reduce, the error whilst maintaining a coarser mesh in other parts of the domain. Through academic and practical examples we demonstrate that our adaptive approach, as compared with a uniform coarse mesh, increases the accuracy of the displacement and stress fields around the needle shaft and, while for a given accuracy, saves computational time with respect to a uniform finer mesh. This facilitates real-time simulations. The proposed methodology has direct implications in increasing the accuracy, and controlling the computational expense of the simulation of percutaneous procedures such as biopsy, brachytherapy, regional anaesthesia, or cryotherapy. Moreover, the proposed approach can be helpful in the development of robotic surgeries because the simulation taking place in the control loop of a robot needs to be accurate, and to occur in real time.

This paper documents on-going work to facilitate ITK-based processing and 3D Slicer scene management in ParaView. We believe this will broaden the use of ParaView for high performance computing and visualization in the medical imaging research community. The effort is focused on developing ParaView plug-ins for managing VTK structures from 3D Slicer MRML scenes and encapsulating ITK filters for deployment in ParaView. In this paper, we present KWScene, an open source cross-platform library that is being developed to support implementation of these types of plugins. We describe the overall design of the library and provide implementation details and conclude by presenting a concrete example that demonstrates the use of the KWScene library in computational anatomy research at Johns Hopkins Center for Imaging Science.

Surgery simulation is a technology based on interactive biomechanics as well as haptic and visual rendering for training novice surgeons. Another important component of a surgery simulator is the representation of a patient’s anatomy in terms of simple shapes, typically triangles and tetrahedra, coinciding with relevant tissues, whose manipulation, cutting and resection is simulated. While this technology has so far emphasized generic simulators, increasingly researchers are emphasizing models that derive from the images of patients whose pathology collectively are predictive of a significant proportion of the future caseload of surgeons. In addition, our philosophy of producing patient-specific neurosurgery simulators is to organize the architecture in terms of two parameters: the choice of approach- pterional, trans-nasal, frontal and so on, and the nature of the pathology, which in turn determines the specific nature of the treatment and choice of tools. This paper describes on-going work on the refinement of an open-source software pipeline for producing patient-specific neurosurgery simulation, based on segmentation tools such as those available in Slicer and BrainVisa, surface and volume meshing, such as public VTK-based tools and Tetgen respectively, and the SOFA simulation platform. Practical requirements of the various components of the pipeline, such as resolution control and fidelity of surface and volume meshing, and interactive nonlinear mechanics in the biomechanics engine, are discussed.

As demonstrated by the example videos accompanying this submission of the multiresolution implementation of Spherical Demons, the registration appears reasonable. However, we are still unable to replicate the warps from the stable and well verified implementation of this algorithm url{http://sites.google.com/site/yeoyeo02/software/sphericaldemonsrelease}.We find the average warp discrepancies between the original implementation and ITK implementation to be about 5.3 mm on a sphere of radius 100.0 mm (note that we do not expect a 100% agreement because of implementation differences, but 5.3 mm is relatively large). The submission also includes cortical surface meshes of 39 subjects and the corresponding segmentation labels of the cortical surfaces. Ultimately, the best validation would be to compare the overlap of these segmentation labels after registration. We welcome fellow ITK developers to work on this.Please note that this ITK implementation of the algorithm is currently being reviewed and tested in the NAMIC Sandbox at: url{http://svn.na-mic.org/NAMICSandBox/trunk/QuadEdgeMeshSphericalDiffeomorphicDemonsRegistration/}.If you want access to the stable and well verified implementation of this algorithm, please use the MATLAB code available at: url{http://sites.google.com/site/yeoyeo02/software/sphericaldemonsrelease}.This document describes a contribution to the Insight Toolkit intended to support the process of performing deformable registration on two Meshes. The method implemented here is restricted to Meshes with a Spherical geometry and topology, and with scalar values associated to their nodes. The code described here is an implementation of the paper “Spherical Demons: Fast Diffeomorphic Landmark-Free Surface Registration” by Yeo, Sabuncu, Vercauteren, Ayache, Fischl and Golland [3, 4].This paper is accompanied with the source code, input data, parameters and output data that we used for validating the algorithm described in this paper. This adheres to the fundamental principle that scientific publications must facilitate reproducibility of the reported results.

This document describes a contribution to the Insight Toolkit intended to support the process of registering two Meshes. The methods included here are restricted to Meshes with a Spherical geometry and topology, and with scalar values associated to their nodes. This paper is accompanied with the source code, input data, parameters and output data that we used for validating the algorithm described in this paper. This adheres to the fundamental principle that scientific publications must facilitate reproducibility of the reported results.

This document describes a simple helper class intended for making easy to initialize the grid parameters of a BSplineDeformableTranform. This paper is accompanied with the source code, input data, parameters and output data that we used for validating the algorithm described in this paper. This adheres to the fundamental principle that scientific publications must facilitate reproducibility of the reported results.

Surgical simulations are normally developed in a cycle of continuous refinement. This leads to high costs in simulator design and as a result to a very limited number of simulators which are used in clinical training scenarios. We propose using Surgical Workflow Analysis for a goal-oriented specification of surgical simulators. Based on Surgical Workflows, the needed interaction scenarios and properties of a simulator can be derived easily. It is also possible to compare an existing simulator with the real workflow to distinguish whether it behaves realistically. We are currently using this method for the design of a new simulator for transnasal neurosurgery with good success.