Video analysis in basic skills training: a way to expand the value and use of BlackBox training?

BACKGROUND: Basic skills training in laparoscopic high-fidelity simulators (LHFS) improves laparoscopic skills. However, since LHFS are expensive, their availability is limited. The aim of this study was to assess whether automated video analysis of low-cost BlackBox laparoscopic training could provide an alternative to LHFS in basic skills training. METHODS: Medical students volunteered to participate during their surgical semester at the Karolinska University Hospital. After written informed consent, they performed two laparoscopic tasks (PEG-transfer and precision-cutting) on a BlackBox trainer. All tasks were videotaped and sent to MPLSC for automated video analysis, generating two parameters (Pl and Prtcl_tot) that assess the total motion activity. The students then carried out final tests on the MIST-VR simulator. This study was a European collaboration among two simulation centers, located in Sweden and Greece, within the framework of ACS-AEI. RESULTS: 31 students (19 females and 12 males), mean age of 26.2 ± 0.8 years, participated in the study. However, since two of the students completed only one of the three MIST-VR tasks, they were excluded. The three MIST-VR scores showed significant positive correlations to both the Pl variable in the automated video analysis of the PEG-transfer (RSquare 0.48, P < 0.0001; 0.34, P = 0.0009; 0.45, P < 0.0001, respectively) as well as to the Prtcl_tot variable in that same exercise (RSquare 0.42, P = 0.0002; 0.29, P = 0.0024; 0.45, P < 0.0001). However, the correlations were exclusively shown in the group with less PC gaming experience as well as in the female group. CONCLUSIONS: Automated video analysis provides accurate results in line with those of the validated MIST-VR. We believe that a more frequent use of automated video analysis could provide an extended value to cost-efficient laparoscopic BlackBox training. However, since there are gender-specific as well as PC gaming experience differences, this should be taken in account regarding the value of automated video analysis.

Virtual reality-based assessment of basic laparoscopic skills using the Leap Motion controller.

BACKGROUND: The majority of the current surgical simulators employ specialized sensory equipment for instrument tracking. The Leap Motion controller is a new device able to track linear objects with sub-millimeter accuracy. The aim of this study was to investigate the potential of a virtual reality (VR) simulator for assessment of basic laparoscopic skills, based on the low-cost Leap Motion controller. METHODS: A simple interface was constructed to simulate the insertion point of the instruments into the abdominal cavity. The controller provided information about the position and orientation of the instruments. Custom tools were constructed to simulate the laparoscopic setup. Three basic VR tasks were developed: camera navigation (CN), instrument navigation (IN), and bimanual operation (BO). The experiments were carried out in two simulation centers: MPLSC (Athens, Greece) and CRESENT (Riyadh, Kingdom of Saudi Arabia). Two groups of surgeons (28 experts and 21 novices) participated in the study by performing the VR tasks. Skills assessment metrics included time, pathlength, and two task-specific errors. The face validity of the training scenarios was also investigated via a questionnaire completed by the participants. RESULTS: Expert surgeons significantly outperformed novices in all assessment metrics for IN and BO (p < 0.05). For CN, a significant difference was found in one error metric (p < 0.05). The greatest difference between the performances of the two groups occurred for BO. Qualitative analysis of the instrument trajectory revealed that experts performed more delicate movements compared to novices. Subjects' ratings on the feedback questionnaire highlighted the training value of the system. CONCLUSIONS: This study provides evidence regarding the potential use of the Leap Motion controller for assessment of basic laparoscopic skills. The proposed system allowed the evaluation of dexterity of the hand movements. Future work will involve comparison studies with validated simulators and development of advanced training scenarios on current Leap Motion controller.

A simple sensor calibration technique for estimating the 3D pose of endoscopic instruments.

INTRODUCTION: The aim of this study was to describe a simple and easy-to-use calibration method that is able to estimate the pose (tip position and orientation) of a rigid endoscopic instrument with respect to an electromagnetic tracking device attached to the handle. METHODS: A two-step calibration protocol was developed. First, the orientation of the instrument shaft is derived by performing a 360° rotation of the instrument around its shaft using a firmly positioned surgical trocar. Second, the 3D position of the instrument tip is obtained by allowing the tip to come in contact with a planar surface. RESULTS: The results indicate submillimeter accuracy in the estimation of the tooltip position, and subdegree accuracy in the estimation of the shaft orientation, both with respect to a known reference frame. The assets of the proposed method are also highlighted by illustrating an indicative application in the field of augmented reality simulation. CONCLUSIONS: The proposed method is simple, inexpensive, does not require employment of special calibration frames, and has potential applications not only in training systems but also in the operating room.

A novel augmented reality simulator for skills assessment in minimal invasive surgery.

INTRODUCTION: Over the past decade, simulation-based training has come to the foreground as an efficient method for training and assessment of surgical skills in minimal invasive surgery. Box-trainers and virtual reality (VR) simulators have been introduced in the teaching curricula and have substituted to some extent the traditional model of training based on animals or cadavers. Augmented reality (AR) is a new technology that allows blending of VR elements and real objects within a real-world scene. In this paper, we present a novel AR simulator for assessment of basic laparoscopic skills. METHODS: The components of the proposed system include: a box-trainer, a camera and a set of laparoscopic tools equipped with custom-made sensors that allow interaction with VR training elements. Three AR tasks were developed, focusing on basic skills such as perception of depth of field, hand-eye coordination and bimanual operation. The construct validity of the system was evaluated via a comparison between two experience groups: novices with no experience in laparoscopic surgery and experienced surgeons. The observed metrics included task execution time, tool pathlength and two task-specific errors. The study also included a feedback questionnaire requiring participants to evaluate the face-validity of the system. RESULTS: Between-group comparison demonstrated highly significant differences (<0.01) in all performance metrics and tasks denoting the simulator's construct validity. Qualitative analysis on the instruments' trajectories highlighted differences between novices and experts regarding smoothness and economy of motion. Subjects' ratings on the feedback questionnaire highlighted the face-validity of the training system. CONCLUSIONS: The results highlight the potential of the proposed simulator to discriminate groups with different expertise providing a proof of concept for the potential use of AR as a core technology for laparoscopic simulation training.

BrachyGuide: a brachytherapy-dedicated DICOM RT viewer and interface to Monte Carlo simulation software.

This work presents BrachyGuide, a brachytherapy-dedicated software tool for the automatic preparation of input files for Monte Carlo simulation from treatment plans exported in DICOM RT format, and results of calculations performed for its benchmarking. Three plans were prepared using two computational models, the image series of a water sphere and a multicatheter breast brachytherapy patient, for each of two commercially available treatment planning systems: BrachyVision and Oncentra Brachy. One plan involved a single source dwell position of an 192Ir HDR source (VS2000 or mHDR-v2) at the center of the water sphere using the TG43 algorithm, and the other two corresponded to the TG43 and advanced dose calculation algorithm for the multicatheter breast brachytherapy patient. Monte Carlo input files were prepared using BrachyGuide and simulations were performed with MCNP v.6.1. For the TG43 patient plans, the Monte Carlo computational model was manually edited in the prepared input files to resemble TG43 dosimetry assumptions. Hence all DICOM RT dose exports were equivalent to corresponding simulation results and their comparison was used for benchmarking the use of BrachyGuide. Monte Carlo simulation results and corresponding DICOM RT dose exports agree within type A uncertainties in the majority of points in the computational models. Treatment planning system, algorithm, and source specific differences greater than type A uncertainties were also observed, but these were explained by treatment planning system-related issues and other sources of type B uncertainty. These differences have to be taken into account in commissioning procedures of brachytherapy dosimetry algorithms. BrachyGuide is accurate and effective for use in the preparation of commissioning tests for new brachytherapy dosimetry algorithms as a user-oriented commissioning tool and the expedition of retrospective patient cohort studies of dosimetry planning.

The Effect of Mixed-Task Basic Training in the Acquisition of Advanced Laparoscopic Skills.

The aim of this study was to assess whether mixed practice of basic tasks on a virtual reality (VR) simulator improves the performance of advanced tasks on the same device used for training as well as on a video trainer (VT). Thirty-six novices were allocated into 3 equal groups. Each group practiced on different combinations of basic tasks on a VR simulator: (A) peg transfer, (B) peg transfer and clipping, and (C) peg transfer, clipping, and cutting. Before and after training, each group performed a laparoscopic cholecystectomy (LC) scenario on the simulator and intracorporeal knot tying (KT) on a VT. Assessment metrics included time, instrument's path length, penalty score, and hand motion synchronization. Results showed that for the common training tasks, plateau values were statistically equivalent for most assessment metrics (P > .05). For LC, all groups showed significant performance improvement (P < .05). For KT, group C improved significantly in pathlength (P < .005), penalty score (P < .05), and hand motion synchronization (P < .05); the other groups failed to show an improvement (P > .05). In conclusion, training on different VR tasks seems to have no effect on the performance of more demanding tasks on the same device. However, the number of different tasks practiced on the VR simulator seems to favorably affect the performance of advanced tasks on the VT.

A head-to-head comparison between virtual reality and physical reality simulation training for basic skills acquisition.

BACKGROUND: This study aimed to investigate whether basic laparoscopic skills acquired with a virtual reality simulator (LapVR™) are transferable to a standard video trainer (VT) and vice versa. METHODS: Three basic tasks were considered: peg transfer, cutting, and knot-tying. The physical models were custom-built as identical copies of the virtual models. Forty-four novices were randomized into two equal groups to be trained on the LapVR™ or the VT. Each task was practiced separately 12 times. Transferability of skills from one modality to the other was assessed by performing the same task on the alternative modality before and after training (crossover assessment). Performance metrics included path length, time, and penalty score. RESULTS: Both groups demonstrated significant performance curves for all tasks and metrics (p < 0.05). Plateaus were statistically equivalent between the groups for each task in terms of path length and time, and across all tasks in terms of the penalty score (p < 0.05). When each group was tested on the alternative modality there was a significant improvement for all tasks and metrics (p < 0.05). Comparing the plateau performance of one group with the performance achieved on the same simulator by the other group we found (a) no statistical deference in the penalty score (p < 0.05), (b) a statistical difference in time and path length for cutting and knot-tying (p < 0.05), and (c) an equal time performance for peg transfer (p < 0.05) but not for path length (p < 0.05). CONCLUSIONS: Both modalities provided significant enhancement of the novices' performance. The skills learned on the LapVR™ are transferable to the VT and vice versa. However, training with one modality does not necessarily mean a performance equivalent to that achieved with the other modality.

A comparative assessment of inhomogeneity and finite patient dimension effects in 60Co and 192Ir high-dose-rate brachytherapy.

PURPOSE: To perform a comparative study of heterogeneities and finite patient dimension effects in 60Co and 192Ir high-dose-rate (HDR) brachytherapy. MATERIAL AND METHODS: Clinically equivalent plans were prepared for 19 cases (8 breast, 5 esophagus, 6 gynecologic) using the Ir2.A85-2 and the Co0.A86 HDR sources, with a TG-43 based treatment planning system (TPS). Phase space files were obtained for the two source designs using MCNP6, and validated through comparison to a single source dosimetry results in the literature. Dose to water, taking into account the patient specific anatomy and materials (Dw,m), was calculated for all plans using MCNP6, with input files prepared using the BrachyGuide software tool to analyze information from DICOM RT plan exports. RESULTS: A general TG-43 dose overestimation was observed, except for the lungs, with a greater magnitude for 192Ir. The distribution of percentage differences between TG-43 and Monte Carlo (MC) in dose volume histogram (DVH) indices for the planning target volume (PTV) presented small median values (about 2%) for both 60Co and 192Ir, with a greater dispersion for 192Ir. Regarding the organs at risk (OARs), median percentage differences for breast V50% were 3% (5%) for 60Co (192Ir). Differences in median skin D2cc were found comparable, with a larger dispersion for 192Ir, and the same applied to the lung D10cc and the aorta D2cc. TG-43 overestimates D2cc for the rectum and the sigmoid, with median differences from MC within 2% and a greater dispersion for 192Ir. For the bladder, the median of the difference is greater for 60Co (~2%) than for 192Ir (~0.75%), demonstrating however a greater dispersion again for 192Ir. CONCLUSIONS: The magnitude of differences observed between TG-43 based and MC dosimetry and their smaller dispersion relative to 192Ir, suggest that 60Co HDR sources are more amenable to the TG-43 assumptions in clinical treatment planning dosimetry.

On source models for (192)Ir HDR brachytherapy dosimetry using model based algorithms.

A source model is a prerequisite of all model based dose calculation algorithms. Besides direct simulation, the use of pre-calculated phase space files (phsp source models) and parameterized phsp source models has been proposed for Monte Carlo (MC) to promote efficiency and ease of implementation in obtaining photon energy, position and direction. In this work, a phsp file for a generic (192)Ir source design (Ballester et al 2015) is obtained from MC simulation. This is used to configure a parameterized phsp source model comprising appropriate probability density functions (PDFs) and a sampling procedure. According to phsp data analysis 15.6% of the generated photons are absorbed within the source, and 90.4% of the emergent photons are primary. The PDFs for sampling photon energy and direction relative to the source long axis, depend on the position of photon emergence. Photons emerge mainly from the cylindrical source surface with a constant probability over ±0.1 cm from the center of the 0.35 cm long source core, and only 1.7% and 0.2% emerge from the source tip and drive wire, respectively. Based on these findings, an analytical parameterized source model is prepared for the calculation of the PDFs from data of source geometry and materials, without the need for a phsp file. The PDFs from the analytical parameterized source model are in close agreement with those employed in the parameterized phsp source model. This agreement prompted the proposal of a purely analytical source model based on isotropic emission of photons generated homogeneously within the source core with energy sampled from the (192)Ir spectrum, and the assignment of a weight according to attenuation within the source. Comparison of single source dosimetry data obtained from detailed MC simulation and the proposed analytical source model show agreement better than 2% except for points lying close to the source longitudinal axis.

A user-oriented procedure for the commissioning and quality assurance testing of treatment planning system dosimetry in high-dose-rate brachytherapy.

PURPOSE: To develop a user-oriented procedure for testing treatment planning system (TPS) dosimetry in high-dose-rate brachytherapy, with particular focus to TPSs using model-based dose calculation algorithms (MBDCAs). METHODS AND MATERIALS: Identical plans were prepared for three computational models using two commercially available systems and the same (192)Ir source. Reference dose distributions were obtained for each plan using the MCNP v.6.1 Monte Carlo (MC) simulation code with input files prepared via automatic parsing of plan information using a custom software tool. The same tool was used for the comparison of reference dose distributions with corresponding MBDCA exports. RESULTS: The single source test case yielded differences due to the MBDCA spatial discretization settings. These affect points at relatively increased distance from the source, and they are abated in test cases with multiple source dwells. Differences beyond MC Type A uncertainty were also observed very close to the source(s), close to the test geometry boundaries, and within heterogeneities. Both MBDCAs studied were found equivalent to MC within 5 cm from the target volume for a clinical breast brachytherapy test case. These are in agreement with previous findings of MBDCA benchmarking in the literature. CONCLUSIONS: The data and the tools presented in this work, that are freely available via the web, can serve as a benchmark for advanced clinical users developing their own tests, a complete commissioning procedure for new adopters of currently available TPSs using MBDCAs, a quality assurance testing tool for future updates of already installed TPSs, or as an admission prerequisite in multicentric clinical trials.

An integrated approach to endoscopic instrument tracking for augmented reality applications in surgical simulation training.

BACKGROUND: Despite the popular use of virtual and physical reality simulators in laparoscopic training, the educational potential of augmented reality (AR) has not received much attention. A major challenge is the robust tracking and three-dimensional (3D) pose estimation of the endoscopic instrument, which are essential for achieving interaction with the virtual world and for realistic rendering when the virtual scene is occluded by the instrument. In this paper we propose a method that addresses these issues, based solely on visual information obtained from the endoscopic camera. METHODS: Two different tracking algorithms are combined for estimating the 3D pose of the surgical instrument with respect to the camera. The first tracker creates an adaptive model of a colour strip attached to the distal part of the tool (close to the tip). The second algorithm tracks the endoscopic shaft, using a combined Hough-Kalman approach. The 3D pose is estimated with perspective geometry, using appropriate measurements extracted by the two trackers. RESULTS: The method has been validated on several complex image sequences for its tracking efficiency, pose estimation accuracy and applicability in AR-based training. Using a standard endoscopic camera, the absolute average error of the tip position was 2.5 mm for working distances commonly found in laparoscopic training. The average error of the instrument's angle with respect to the camera plane was approximately 2°. The results are also supplemented by video segments of laparoscopic training tasks performed in a physical and an AR environment. CONCLUSIONS: The experiments yielded promising results regarding the potential of applying AR technologies for laparoscopic skills training, based on a computer vision framework. The issue of occlusion handling was adequately addressed. The estimated trajectory of the instruments may also be used for surgical gesture interpretation and assessment.