Patient-specific Computed Tomography Data Research Articles

Creation of a video library for education and virtual simulation of anatomical lung resection.

OBJECTIVESRecently, preoperative and intraoperative simulation using three-dimensional computed tomography (CT) has attracted much attention in thoracic surgery. However, because conventional three-dimensional CT only shows static images, dynamic simulation is required for a more precise operation. We previously reported on a resection process map for pulmonary resection, which we developed to generate virtual dynamic images from preoperative patient-specific CT scans. The goal of this study was to evaluate the feasibility of the clinical use of the resection process map for anatomical lung resection.METHODSThis study included 5 lobectomies for different lobes and 4 representative segmentectomies. Dissection of the pulmonary arteries, veins and bronchi were considered key parts of each procedure. To assess the description of images obtained from the resection process map, relevant clips from the actual surgical videos were collected, retrospectively replicated and superimposed on the resection process map to explain the procedures.RESULTSIn all surgical procedures, the resection process map successfully and semiautomatically generated a virtual dynamic image from the patient-specific CT data. Moreover, superimposition of the virtual images on the selected clips from the surgical videos showed no major differences.CONCLUSIONSThe resection process map could generate virtual images that corresponded to the actual surgical videos and has the potential for clinical use as preoperative and intraoperative simulation.

Resection Process Map: A novel dynamic simulation system for pulmonary resection

ObjectiveUse of 3-dimensional computed tomography for preoperative and intraoperative simulation has been introduced in the field of thoracic surgery. However, 3-dimensional computed tomography provides only static simulation, which is a significant limitation of surgical simulation. Dynamic simulation, reflecting the intraoperative deformation of the lung, has not been developed. The aim of this study was to develop a novel simulation system that generates dynamic images based on patient-specific computed tomography data. MethodsWe developed an original software, the Resection Process Map, for anatomic pulmonary resection. The Resection Process Map semi-automatically generates virtual dynamic images based on patient-specific computed tomography data. We retrospectively evaluated its accuracy in 18 representative cases by comparing the virtual dynamic images with the actual surgical images. ResultsIn this study, 9 patients who underwent lobectomy and 9 patients who underwent segmentectomy were included. For each case, a virtual dynamic image was successfully generated semi-automatically by the Resection Process Map. The Resection Process Map accurately delineated 98.6% of vessel branches and all the bronchi. The median time required to obtain the images was 121.3 seconds. ConclusionsWe successfully developed a novel dynamic simulation system, the Resection Process Map, for anatomic pulmonary resection.

Patient-Specific Prediction of Abdominal Aortic Aneurysm Expansion Using Bayesian Calibration.

Translating recent advances in abdominal aortic aneurysm(AAA) growth and remodeling (G&R) knowledge into a predictive, patient-specific clinical treatment tool requires a major paradigm shift in computational modeling. The objectives of this study are to develop a prediction framework that first calibrates the physical AAA G&R model using patient-specific serial computed tomography (CT) scan images, predicts the expansion of an AAA in the future, and quantifies the associated uncertainty in the prediction. We adopt a Bayesian calibration method to calibrate parameters in the G&R computational model and predict the magnitude of AAA expansion. The proposed Bayesian approach can take different sources of uncertainty; therefore, it is well suited to achieve our aims in predicting the AAA expansion process as well as in computing the propagated uncertainty. We demonstrate how to achieve the proposed aims by solving the formulated Bayesian calibration problems for cases with the synthetic G&R model output data and real medical patient-specific CT data. We compare and discuss the performance of predictions and computation time under different sampling cases of the model output data and patient data, both of which are simulated by the G&R computation. Furthermore, we apply our Bayesian calibration to real patient-specific serial CT data and validate our prediction. The accuracy and efficiency of the proposed method is promising, which appeals to computational and medical communities.

Estimating pedicle screw fastening strength via a virtual templating platform for spine surgery planning: a retrospective preliminary clinical demonstration

Traditional 2D images provide limited use for accurate planning of spine interventions, due to their inability to display the complex 3D spine anatomy and proximity of nerve bundles and vascular structures that must be avoided during the procedure. We have developed a platform for spine surgery planning that employs standard of care 3D preoperative images and enables oblique reformatting and 3D rendering of individual or multiple vertebrae, interactive templating and placement of virtual pedicle implants into the patient-specific computed tomography data. Here we propose a combined surrogate metric – the fastening strength – to provide estimates of the optimal implant selection and trajectory based on implant dimension and bone mineral density (BMD) of the displaced bone substrate. We conducted a retrospective clinical study based on pre- and post-operative data from four patients who underwent procedures involving pedicle screw implantation. We assessed the retrospective plans against the post-operative imaging data according to implant dimension, mean voxel intensity of implant trajectory, and fastening strength and showed consistency between the proposed plans and the post-operative procedure outcome. Our preliminary studies have demonstrated the feasibility of the platform in assisting the surgeon with the selection of appropriate size implant and trajectory that optimises fastening strength, given the intrinsic vertebral geometry and BMD.

Kallus Stabilizasyonu'nda Optimum Vida Konfigürasyonunun Belirlenmesi

Distraction osteogenesis is a common clinical procedure to correct mandibular retrognathia cases. In spite of consolidated clinical use, lots of questions still remain to be answered concerning distraction osteogenesis. One of them is to determine the best screw configuration providing boneremodelling in a healthy way due to the stabilization of callus. In this study, some suggestions will be presented about the points “what best screw locations are” and “what the optimum screw quantity is”. A three dimensional solid model was obtained by processing patient-specific computed tomography data in DICOM format. Teeth, cortical and trabecular bone segments were modelled separately with the segmentation process. Ramus and corpus segments were separated from each other by virtual surgery and corpus segment was positioned 11 mm forward. The distractors modelled were assembled into the mandible after modelling the callus. The volume meshes created for all the parts were transferred to a finite element software. Finite element analyses were run as bilaterally symmetric which means the same screw configurations were set for both sides of the mandible. The studies carried out in this paper have shown that screws located closer to the osteotomy line provide more stability, and triangular configuration has a better impact on stability than linear configuration. The reference stabilization case was identified as the scenario of using 22 screws in total, including 8 screws in ramus segment and 14 screws in corpus segment. This case was assumed as maximum stabilization case and other analyses were compared with this result. The results of the configuration including triangularly located 3 screws in ramus segment and closely located 2 screws near the osteotomy line in corpus segment have shown similarity with the reference stabilization case. The closest configuration to the reference case has been tried to determine by using as few screws as possible and has been recommended for clinical use

TOPAS: An innovative proton Monte Carlo platform for research and clinical applications

While Monte Carlo particle transport has proven useful in many areas (treatment head design, dose calculation, shielding design, and imaging studies) and has been particularly important for proton therapy (due to the conformal dose distributions and a finite beam range in the patient), the available general purpose Monte Carlo codes in proton therapy have been overly complex for most clinical medical physicists. The learning process has large costs not only in time but also in reliability. To address this issue, we developed an innovative proton Monte Carlo platform and tested the tool in a variety of proton therapy applications. Our approach was to take one of the already-established general purpose Monte Carlo codes and wrap and extend it to create a specialized user-friendly tool for proton therapy. The resulting tool, TOol for PArticle Simulation (TOPAS), should make Monte Carlo simulation more readily available for research and clinical physicists. TOPAS can model a passive scattering or scanning beam treatment head, model a patient geometry based on computed tomography (CT) images, score dose, fluence, etc., save and restart a phase space, provides advanced graphics, and is fully four-dimensional (4D) to handle variations in beam delivery and patient geometry during treatment. A custom-designed TOPAS parameter control system was placed at the heart of the code to meet requirements for ease of use, reliability, and repeatability without sacrificing flexibility. We built and tested the TOPAS code. We have shown that the TOPAS parameter system provides easy yet flexible control over all key simulation areas such as geometry setup, particle source setup, scoring setup, etc. Through design consistency, we have insured that user experience gained in configuring one component, scorer or filter applies equally well to configuring any other component, scorer or filter. We have incorporated key lessons from safety management, proactively removing possible sources of user error such as line-ordering mistakes. We have modeled proton therapy treatment examples including the UCSF eye treatment head, the MGH stereotactic alignment in radiosurgery treatment head and the MGH gantry treatment heads in passive scattering and scanning modes, and we have demonstrated dose calculation based on patient-specific CT data. Initial validation results show agreement with measured data and demonstrate the capabilities of TOPAS in simulating beam delivery in 3D and 4D. We have demonstrated TOPAS accuracy and usability in a variety of proton therapy setups. As we are preparing to make this tool freely available for researchers in medical physics, we anticipate widespread use of this tool in the growing proton therapy community.

Custom-designed orthopedic implants evaluated using finite element analysis of patient-specific computed tomography data: femoral-component case study

Custom-designed orthopedic implants evaluated using finite element analysis of patient-specific computed tomography data: femoral-component case study

Custom-designed orthopedic implants evaluated using finite element analysis of patient-specific computed tomography data: femoral-component case study

BackgroundConventional knee and hip implant systems have been in use for many years with good success. However, the custom design of implant components based on patient-specific anatomy has been attempted to overcome existing shortcomings of current designs. The longevity of cementless implant components is highly dependent on the initial fit between the bone surface and the implant. The bone-implant interface design has historically been limited by the surgical tools and cutting guides available; and the cost of fabricating custom-designed implant components has been prohibitive.MethodsThis paper describes an approach where the custom design is based on a Computed Tomography scan of the patient's joint. The proposed design will customize both the articulating surface and the bone-implant interface to address the most common problems found with conventional knee-implant components. Finite Element Analysis is used to evaluate and compare the proposed design of a custom femoral component with a conventional design.ResultsThe proposed design shows a more even stress distribution on the bone-implant interface surface, which will reduce the uneven bone remodeling that can lead to premature loosening.ConclusionThe proposed custom femoral component design has the following advantages compared with a conventional femoral component. (i) Since the articulating surface closely mimics the shape of the distal femur, there is no need for resurfacing of the patella or gait change. (ii) Owing to the resulting stress distribution, bone remodeling is even and the risk of premature loosening might be reduced. (iii) Because the bone-implant interface can accommodate anatomical abnormalities at the distal femur, the need for surgical interventions and fitting of filler components is reduced. (iv) Given that the bone-implant interface is customized, about 40% less bone must be removed. The primary disadvantages are the time and cost required for the design and the possible need for a surgical robot to perform the bone resection. Some of these disadvantages may be eliminated by the use of rapid prototyping technologies, especially the use of Electron Beam Melting technology for quick and economical fabrication of custom implant components.