Special Issue on Medical Simulation

We would like to welcome you to this Special Issue on Medical Simulation, the first of its kind not only for SIMULATION: Transactions of The Society for Modeling and Simulation International, but for any technical journal. Our respective backgrounds are an indication of the technical and clinical breadth of medical simulation, as we approach the subject as primarily medical image analysis and biomechanics experts respectively, each with a variety of clinical interests spanning virtual reality (VR)–based neuro-, orthopedic and ear-nose-and-throat surgery. Moreover, we believe that the breadth of the papers that comprise this issue reflects an even broader perspective. After all, medical simulation can be seen as encompassing mannequin-based training, as well as nonsurgical areas such as pharmacological and physiological modeling, the latter of which is increasingly multi-scale and integrative

Face and content validity of a novel, web-based otoscopy simulator for medical education.

BACKGROUND: Despite the fact that otoscopy is a widely used and taught diagnostic tool during medical training, errors in diagnosis are common. Physical otoscopy simulators have high fidelity, but they can be expensive and only a limited number of students can use them at a given time. OBJECTIVES: 1) To develop a purely web-based otoscopy simulator that can easily be distributed to students over the internet. 2) To assess face and content validity of the simulator by surveying experts in otoscopy. METHODS: An otoscopy simulator, OtoTrain™, was developed at Western University using web-based programming and Unity 3D. Eleven experts from academic institutions in North America were recruited to test the simulator and respond to an online questionnaire. A 7-point Likert scale was used to answer questions related to face validity (realism of the simulator), content validity (expert evaluation of subject matter and test items), and applicability to medical training. RESULTS: The mean responses for the face validity, content validity, and applicability to medical training portions of the questionnaire were all ≤3, falling between the Agree , Mostly Agree , and Strongly Agree categories. The responses suggest good face and content validity of the simulator. Open-ended questions revealed that the primary drawbacks of the simulator were the lack of a haptic arm for force feedback, a need for increased focus on pneumatic otoscopy, and few rare disorders shown on otoscopy. CONCLUSION: OtoTrain™ is a novel, web-based otoscopy simulator that can be easily distributed and used by students on a variety of platforms. Initial face and content validity was encouraging, and a skills transference study is planned following further modifications and improvements to the simulator

PWD-3DNet: A Deep Learning-Based Fully-Automated Segmentation of Multiple Structures on Temporal Bone CT Scans

The temporal bone is a part of the lateral skull surface that contains organs responsible for hearing and balance. Mastering surgery of the temporal bone is challenging because of this complex and microscopic three-dimensional anatomy. Segmentation of intra-temporal anatomy based on computed tomography (CT) images is necessary for applications such as surgical training and rehearsal, amongst others. However, temporal bone segmentation is challenging due to the similar intensities and complicated anatomical relationships among critical structures, undetectable small structures on standard clinical CT, and the amount of time required for manual segmentation. This paper describes a single multi-class deep learning-based pipeline as the first fully automated algorithm for segmenting multiple temporal bone structures from CT volumes, including the sigmoid sinus, facial nerve, inner ear, malleus, incus, stapes, internal carotid artery and internal auditory canal. The proposed fully convolutional network, PWD-3DNet, is a patch-wise densely connected (PWD) three-dimensional (3D) network. The accuracy and speed of the proposed algorithm was shown to surpass current manual and semi-automated segmentation techniques. The experimental results yielded significantly high Dice similarity scores and low Hausdorff distances for all temporal bone structures with an average of 86% and 0.755 millimeter (mm), respectively. We illustrated that overlapping in the inference sub-volumes improves the segmentation performance. Moreover, we proposed augmentation layers by using samples with various transformations and image artefacts to increase the robustness of PWD-3DNet against image acquisition protocols, such as smoothing caused by soft tissue scanner settings and larger voxel sizes used for radiation reduction. The proposed algorithm was tested on low-resolution CTs acquired by another center with different scanner parameters than the ones used to create the algorithm and shows potential for application beyond the particular training data used in the study

Finite-element and experimental analyses of the response of the cat eardrum to large static pressures

Currently available mathematical models of the eardrum are limited to low pressure levels owing to the assumption of linearity between stimulus (applied pressure) and response (eardrum displacement). In this work, the response of the cat eardrum to large static pressures is measured with a moire interferometer, and the data are modelled using the finite-element method. Experimental data indicate that eardrum response with a normal mobile malleus is nonlinear, asymmetric and hysteretic. Measurements with a fixed malleus permit investigation of eardrum behaviour without the confounding effects of the middle-ear ossicles.Artifactual banding in measured displacement patterns is investigated by means of numerical simulations. Artifacts in moire interferometry arise from ignoring height-dependent fringe-plane spacing, modulation, reflectivity and magnification when reconstructing surface shape. Systematic errors induced by these assumptions are small: their effects are not apparent in shape measurements, but do show up as bands in displacement images.The fixed-malleus data are modelled using the finite-element method to assess the importance of geometric nonlinearities at high pressure levels. Individualized finite-element models are created from shape data for each eardrum. Results indicate that geometric nonlinearity combined with nonuniform mechanical properties shows promise in describing eardrum response at high pressures

Finite-element modelling of middle-ear prostheses in cat

Discontinuity of the middle-ear ossicular chain results in conductive hearing loss. Two prostheses commonly used to surgically repair the ossicular chain are the MSA and the MFA. In the MSA, a strut is connected between the malleus and the head of the stapes, while in the MFA a strut is connected between the malleus and the footplate of the stapes. In this work, finite-element models of the MSA, MFA and normal cat middle ear are developed. The models are valid for low frequencies (below 300 Hz) and for physiological sound levels. The mechanical behaviour of the normal middle-ear model is compared with that of the MFA and MSA models. Several parameters are then varied in order to study their relative importance in the models. The effects of strut placement on the behaviour of the MSA and MFA models are also investigated

Finite-element modeling of the normal and surgically repaired cat middle ear

In this work, three-dimensional finite-element models of the normal and surgically repaired cat middle ear were developed. The normal middle-ear model was formed by adding explicit representations for the footplate and cochlear load to an existing model of the cat eardrum. The footplate was modeled as a thin plate with a thickened rim. The cochlear load was represented by springs attached along the footplate’s periphery. The model is valid for frequencies below 1 kHz and for physiological sound levels. Eardrum and manubrium displacements, and out-of-plane displacements of the footplate’s center, were found to compare well with experimental results. The normal model was modified to simulate the effects of two types of middle-ear surgery, both of which are used to repair a discontinuous ossicular chain. Bulging of the footplate was found to occur when a prosthesis made direct contact with the footplate. The location of the prosthesis along the manubrium did not affect the motion of the footplate as long as the joints were all rigid. When the joints were flexible, the largest displacements occurred when the prosthesis was positioned near the upper end of the manubrium