Maturity assessment of software-driven medical technologies: a quantitative score derived from a quality standard for the research phase.

Quantitatively assessing the level of readiness of medical technology improves its chance of successfully transfer from research to industry but remains a challenge. As many innovative medical devices are associated with or incorporate software, this article presents a methodology for evaluating the software maturity of a "Software-driven Medical Technology" (SdMT) during the research phase. A technological maturity model is developed by methodologically extracting relevant terms from the ISO/IEC 62304 standard, the main industry standard for medical device software, and results in a list of required software engineering artifacts. This list and the relative weight of the artifacts are used to establish a software maturity score for SdMT and the corresponding assessment questionnaire. The consistency of the model is demonstrated by analyzing the obtained score system relatively with the standard. The maturity score of a SdMT can be assessed during the research phase and depends on the number and importance of the artifacts already present at the time of evaluation.Clinical relevance- The proposed quantitative maturity score can help the medical technology innovation actors (clinicians, researchers and industrials) to better identify, improve and fasten the readiness of technology for clinical investigation and technology transfer.

Qualitative Comparison of Image Stitching Algorithms for Multi-Camera Systems in Laparoscopy.

Multi-camera systems were recently introduced into laparoscopy to increase the narrow field of view of the surgeon. The video streams are stitched together to create a panorama that is easier for the surgeon to comprehend. Multi-camera prototypes for laparoscopy use quite basic algorithms and have only been evaluated on simple laparoscopic scenarios. The more recent state-of-the-art algorithms, mainly designed for the smartphone industry, have not yet been evaluated in laparoscopic conditions. We developed a simulated environment to generate a dataset of multi-view images displaying a wide range of laparoscopic situations, which is adaptable to any multi-camera system. We evaluated classical and state-of-the-art image stitching techniques used in non-medical applications on this dataset, including one unsupervised deep learning approach. We show that classical techniques that use global homography fail to provide a clinically satisfactory rendering and that even the most recent techniques, despite providing high quality panorama images in non-medical situations, may suffer from poor alignment or severe distortions in simulated laparoscopic scenarios. We highlight the main advantages and flaws of each algorithm within a laparoscopic context, identify the main remaining challenges that are specific to laparoscopy, and propose methods to improve these approaches. We provide public access to the simulated environment and dataset.

External validation of a prostate biopsy simulator.

INTRODUCTION: Simulation-based training has proven to be a promising option allowing for initial and continuous training while limiting the impact of the learning curve on the patient. The Biopsym simulator was developed as a complete teaching environment for the prostate biopsy procedure. This paper presents the results of an external validation of this simulator, involving urology residents recruited during a regional teaching seminar. METHODS: Residents from 4 academic urology departments of the French Auvergne Rhône-Alpes region, who did not take part in the previous simulator validation studies, were enrolled. After a short presentation and standardized initiation session, residents carried out a simulated systematic 12-core biopsy procedure and were asked to fill in a questionnaire collecting their expectations and evaluation of the Biopsym simulator. The number of biopsies reaching each targeted sector, the total score provided by the simulator and the duration of the procedure were recorded. RESULTS: Twenty-three residents were recruited. The overall added value (/100) for learning was rated at a median of 100 (interquartile range 83-100), overall realism of the biopsy procedure at 80 (65-89). The median percentage of biopsies reaching the targeted sector was 66.7% (62-75). The median score provided by the simulator was 50% (37-60). For both, the difference between residents with or without prior biopsy experience was not statistically significant. The median duration of the simulated biopsy procedure was 4:58 (minutes: seconds) (3:49-6:00). Resident with prior experience required less time to complete the biopsy procedure 3:53 (3:39-4:56) vs. 5:10 (4:59-7:10), P=0.01. CONCLUSION: This external validation study confirms a high acceptance of the simulator by the target audience. To our knowledge, the Biopsym simulator is the only prostate biopsy simulator that demonstrated such validity as evaluated by clinicians, outside the center involved in its early development. LEVEL OF EVIDENCE: 3.

Validating the Transfer of Skills Acquired on a Prostate Biopsy Simulator: A Prospective, Randomized, Controlled Study.

OBJECTIVES: To evaluate the ability of students to reproduce the skills acquired on a prostate biopsy simulator in a real-life situation. DESIGN: A prospective randomized controlled study was conducted. Medical students with no experience of prostate biopsy were randomized between arm A « conventional training ¼ and arm B « simulator-enhanced training. ¼ The training was performed for both groups on the simulator. The students in arm B were provided with visual and numerical feedback. The transfer of skills was assessed by recording the position of the 12 biopsies performed by each student on an unembalmed human cadaver using a 3D ultrasound mapping device. SETTING: The study was conducted in an academic urology department and the cadaver experiments in the adjoining anatomy laboratory. RESULTS: Twenty-four students were included, and 22 completed the study. The median score obtained on the simulator at the end of the training was 57% (53-61) for arm A and 66% (59-71) for arm B. The median score obtained on the cadaver by students trained with the simulator was 75% (60-80), statistically superior to the score obtained by students trained conventionally of 45% (30-60), p < 0.0001. The median score obtained by all students when performing biopsies in a real-life situation was 63% (50-80) versus 60% (56-70) for their last training on the simulator. CONCLUSION: These results support the transfer of skills acquired on the simulator, and the superiority of a training curriculum integrating simulation, and performance feedback.

Simulation-based training for prostate biopsies: towards the validation of the Biopsym simulator.

Objectives: The Biopsym simulator, a virtual-reality simulator for prostate biopsies, was designed to offer enhanced teaching of the biopsy procedure. The objectives of the present article are to describe the new version of the simulator and report the results of a new validation study.Material and methods: A prospective validation study was conducted between January and March 2017. The new version of the simulator, with improved physical realism, ultrasound image deformation, and a new scoring system, was evaluated by novice and confirmed users.Results: Twenty-one users evaluated the simulator, including ten novices and 11 confirmed users. The overall realism of the biopsy procedure was rated at 7.7/10 (IQR 5.7-9). The differences between the rates given by confirmed users and novices were not statistically significant. The median overall score obtained for the performance of 12 systematic ultrasound-guided biopsies was 43% (IQR 33-55). The median score obtained by confirmed users was 54% (IQR 46-62), and the median score obtained by novices was 31% (IQR 20-35). The difference between the scores was statistically significant (p = 0.005).Conclusions: This study allowed us to gather evidence towards the validation, and particularly towards the construct validation of the new version of the Biopsym simulator.

Hybrid 2D-3D ultrasound registration for navigated prostate biopsy.

PURPOSE: We present a hybrid 2D-3D ultrasound (US) rigid registration method for navigated prostate biopsy that enables continuous localization of the biopsy trajectory during the exam. METHODS: Current clinical computer-assisted biopsy systems use either sensor-based or image-based approaches. We combine the advantages of both in order to obtain an accurate and real-time navigation based only on an approximate localization of the US probe. Starting with features extracted in both 2D and 3D images, our method introduces a variant of the iterative closest point (ICP) algorithm. Among other differences to ICP, a combination of both the euclidean distance of feature positions and the similarity distance of feature descriptors is used to find matches between 2D and 3D features. The evaluation of the method is twofold. First, an analysis of variance on input parameters is conducted to estimate the sensitivity of our method to their initialization. Second, for a selected set of their values, the target registration error (TRE) was calculated on 29,760 (resp. 4000) registrations in two different experiments. It was obtained using manually identified anatomical fiducials. RESULTS: For 160 US volumes, from 20 patients, recorded during routine biopsy procedures performed in two hospitals by six operators, the mean TRE was [Formula: see text] mm (resp. [Formula: see text] mm). CONCLUSION: This work allows envisioning further developments for prostate navigation and their clinical transfer.

3D-2D ultrasound feature-based registration for navigated prostate biopsy: a feasibility study.

The aim of this paper is to describe a 3D-2D ultrasound feature-based registration method for navigated prostate biopsy and its first results obtained on patient data. A system combining a low-cost tracking system and a 3D-2D registration algorithm was designed. The proposed 3D-2D registration method combines geometric and image-based distances. After extracting features from ultrasound images, 3D and 2D features within a defined distance are matched using an intensity-based function. The results are encouraging and show acceptable errors with simulated transforms applied on ultrasound volumes from real patients.

Hand-eye calibration of a robot--UltraSound probe system without any 3D localizers.

3D UltraSound (US) probes are used in clinical applications for their ease of use and ability to obtain intra-operative volumes. In surgical navigation applications a calibration step is needed to localize the probe in a general coordinate system. This paper presents a new hand-eye calibration method using directly the kinematic model of a robot and US volume registration data that does not require any 3D localizers. First results show a targeting error of 2.34 mm on an experimental setup using manual segmentation of five beads in ten US volumes.

Initial validation of a virtual-reality learning environment for prostate biopsies: realism matters!

BACKGROUND AND PURPOSE: A virtual-reality learning environment dedicated to prostate biopsies was designed to overcome the limitations of current classical teaching methods. The aim of this study was to validate reliability, face, content, and construct of the simulator. MATERIALS AND METHODS: The simulator is composed of (a) a laptop computer, (b) a haptic device with a stylus that mimics the ultrasound probe, (c) a clinical case database including three-dimensional (3D) ultrasound volumes and patient data, and (d) a learning environment with a set of progressive exercises including a randomized 12-core biopsy procedure. Both visual (3D biopsy mapping) and numerical (score) feedback are given to the user. The simulator evaluation was conducted in an academic urology department on 7 experts and 14 novices who each performed a virtual biopsy procedure and completed a face and content validity questionnaire. RESULTS: The overall realism of the biopsy procedure was rated at a median of 9/10 by nonexperts (7.1-9.8). Experts rated the usefulness of the simulator for the initial training of urologists at 8.2/10 (7.9-8.3), but reported the range of motion and force feedback as significantly less realistic than novices (P=0.01 and 0.03, respectively). Pearson r correlation coefficient between correctly placed biopsies on the right and left side of the prostate for each user was 0.79 (P<0.001). The 7 experts had a median score of 64% (59%-73%), and the 14 novices a median score of 52% (43%-67%), without reaching statistical significance (P=0.19). CONCLUSION: The newly designed virtual-reality learning environment proved its versatility and its reliability, face, and content were validated. Demonstrating the construct validity will necessitate improvements to the realism and scoring system used.

Using CamiTK for rapid prototyping of interactive computer assisted medical intervention applications.

Computer Assisted Medical Intervention (CAMI hereafter) is a complex multi-disciplinary field. CAMI research requires the collaboration of experts in several fields as diverse as medicine, computer science, mathematics, instrumentation, signal processing, mechanics, modeling, automatics, optics, etc. CamiTK is a modular framework that helps researchers and clinicians to collaborate together in order to prototype CAMI applications by regrouping the knowledge and expertise from each discipline. It is an open-source, cross-platform generic and modular tool written in C++ which can handle medical images, surgical navigation, biomedicals simulations and robot control. This paper presents the Computer Assisted Medical Intervention ToolKit (CamiTK) and how it is used in various applications in our research team.

Origins of balance disorders during a daily living movement in obese: can biomechanical factors explain everything?

Obese people suffer from postural deficits and are more subject to falls than their lean counterpart. To improve prevention and post-fall rehabilitation programs, it seems important to better understand the posturo-kinetic disorders in daily life situations by determining the contribution of some key factors, mainly morphological characteristics and physical activity level, in the apparition of these disorders. Twelve severe android obese and eight healthy non obese adults performed a reaching task mobilizing the whole body. To further determine the origin of the postural and motor behavior differences, non obese individuals also performed an experimental session with additional constraints which simulated some of the obese morphological characteristics. Impact of the sedentary lifestyle was also studied by dissociation of the obese in two subgroups: physically « active ¼ and physically « inactive ¼. Movement kinetics and kinematics were characterized with an optoelectronic system synchronized to a force platform. The mechanical equilibrium pattern was evaluated through the displacements of the Centre of Mass (CoM) and the centre of foot pressure within the Base of Support (BoS). Results showed that obesity decreased movement speed (≈-23%, p<0.01), strongly increased CoM displacement (≈+30%, p<0.05) and induced an important spatio-temporal desynchronization (≈+40%, p<0.05) of the focal and postural components of the movement during the transition between the descending and ascending movements. The role of some morphological characteristics and of physical activity on obese patients' postural control disorder is discussed and set back in the more general context of overall factors contributing to postural deficits with obesity.

Towards a generic framework for evaluation and comparison of soft tissue modeling.

Numerous models have been developed to describe the mechanical behavior of soft tissue in virtual reality medical environments. Very high credibility must be established before clinicians trust these simulations for diagnostic or treatment. Validating models to obtain the right compromise between accuracy and computational efficiency for the targeted medical application is a long, costly and time-consuming task. We have developed a freely available open-source framework for helping scientists in the difficult problem of evaluating and comparing biomechanical models in a more systematic and automatic manner.

Obesity impact on the attentional cost for controlling posture.

BACKGROUND: This study investigated the effects of obesity on attentional resources allocated to postural control in seating and unipedal standing. METHODS: Ten non obese adults (BMI = 22.4±1.3, age = 42.4±15.1) and 10 obese adult patients (BMI = 35.2±2.8, age = 46.2±19.6) maintained postural stability on a force platform in two postural tasks (seated and unipedal). The two postural tasks were performed (1) alone and (2) in a dual-task paradigm in combination with an auditory reaction time task (RT). Performing the RT task together with the postural one was supposed to require some attentional resources that allowed estimating the attentional cost of postural control. 4 trials were performed in each condition for a total of 16 trials. FINDINGS: (1) Whereas seated non obese and obese patients exhibited similar centre of foot pressure oscillations (CoP), in the unipedal stance only obese patients strongly increased their CoP sway in comparison to controls. (2) Whatever the postural task, the additional RT task did not affect postural stability. (3) Seated, RT did not differ between the two groups. (4) RT strongly increased between the two postural conditions in the obese patients only, suggesting that body schema and the use of internal models was altered with obesity. INTERPRETATION: Obese patients needed more attentional resources to control postural stability during unipedal stance than non obese participants. This was not the case in a more simple posture such as seating. To reduce the risk of fall as indicated by the critical values of CoP displacement, obese patients must dedicate a strong large part of their attentional resources to postural control, to the detriment of non-postural events. Obese patients were not able to easily perform multitasking as healthy adults do, reflecting weakened psycho-motor abilities.

A discrete soft tissue model for complex anatomical environment simulations.

Among the current challenges in human soft tissue modeling for medical purposes, the ability to model complex anatomical structures, their interactions and to accurately simulate them with physical realism are in the forefront of research. This paper describes a discrete soft tissue model which is geared toward solving these challenges. In this model, objects can be described as volumetric or surfacic sets of nodes depending on the level of precision required. Nodes have their own physical properties and a definition of their neighborhood. All these objects are submitted both to internal cohesive forces and to external attractive or interaction forces with other objects. Volume preservation is insured by a constraint. The model is applied to the simulation of the prostate and its surrounding organs.