Validation of an Ex Vivo Calf Brain Force Detection System for Neurosurgical Simulation Training

Background and Rationale: The subpial resection technique is a complex neurosurgical procedure that is essential for brain tumor and epilepsy surgery. However, opportunities for trainees to gain hands-on experience with this procedure without risk to patient safety are limited. The force applied on the brain during tool-tissue contact is a critical factor impacting patient safety. While virtual simulation platforms enable force monitoring, ex vivo animal brains cannot readily capture quantitative data. The investigators have therefore developed a prototype of a simulation platform that integrates a force sensor and a calf brain and can accurately detect real-time forces during simulated subpial resections. This study seeks to investigate the validity of this ex vivo calf brain force detection system.

Hypotheses:

1. The forces applied by instruments on an ex vivo calf brain during simulated subpial resection procedures will significantly differ between novice, intermediate, and expert participants.
2. The ex vivo calf brain force detection system will demonstrate face, content, construct, and convergent validity.
3. Levels of negative emotions, stress, and cognitive load will be greater in surgical trainees compared with experts.

Primary Objective: To measure and compare the forces applied by novice, intermediate, and expert participants during simulated ex vivo subpial resection procedures.

Secondary Objectives:

1. To evaluate the face, content, construct, and convergent validity of the ex vivo calf brain force measurement setup.
2. To determine how the simulation platform influences emotions, stress, and cognitive load of participants of different expertise levels.

Setting: McGill University Montreal Neurological Institute and Hospital.

Participants:

Neurosurgeons (experts): Staff neurosurgeons at McGill University, Université de Montréal, Université de Sherbrooke, or Université Laval specializing in oncology, epilepsy, pediatric, or vascular neurosurgery.

Neurosurgical fellows (trainees): Neurosurgical fellows at McGill University, Université de Montréal, Université de Sherbrooke, or Université Laval specializing in oncology, epilepsy, pediatric, or vascular neurosurgery.

Neurosurgical residents (trainees): Neurosurgical residents at McGill University, Université de Montréal, Université de Sherbrooke, or Université Laval.

Medical students (novices): Students enrolled in medical school at McGill University, Université de Montréal, Université de Sherbrooke, or Université Laval.

Design: A cross-sectional case series study.

Methodology: This study was approved by the McGill University Health Centre Research Ethics Board, Neurosciences-Psychiatry. A case series study will be conducted where medical students, neurosurgical residents, neurosurgical fellows, and staff neurosurgeons from four Quebec institutions will be recruited to perform subpial resection tasks on an ex vivo calf brain model. Calf brains will be placed in a 3D-printed skull model to mimic a realistic human operative environment. The 3D-printed skull model was prototyped from a publicly available CT scan obtained from Embodi3D, an open-access medical imaging repository, and reconstructed in 3D using the open-source software 3D Slicer version 5.10.0. A 6-degree-of-freedom force/torque sensor (Nano17 IP68, ATI Industrial Automation Inc., North Carolina, USA) and a USB data acquisition board (NI-6210, National Instruments Inc., Texas, USA) will be used to measure real-time forces applied to the brain. Participants will use microscissors, bipolar forceps, and a SONOPET ultrasonic aspirator (Stryker, Portage, Michigan, USA) to perform each simulated procedure. All three surgical instruments will be continuously tracked using infrared cameras, allowing kinematic data (velocity, acceleration, and jerk) of each instrument to be derived. The tasks will be performed using an OPMI pico surgical microscope (ZEISS, Jena, Germany) and video-recorded using a Blackfly S GigE embedded microscope camera (FLIR, Wilsonville, Oregon, USA), allowing a broader instrument view for evaluation of tracking data and postoperative performance. Before, during, and after the trial, all participants will self-report their emotions using Medical Emotions Scale (MES) and their stress using the Short Stress State Questionnaire (SSSQ) on 7-point Likert scales. All participants will also report their cognitive load after the trial using the Cognitive Load Index (CLI) on 5-point Likert scales and the NASA Task Load Index (NASA-TLX) on 7-point Likert scales. Expert participants will fill out questionnaires assessing the face and content validity of the ex vivo calf brain force detection setup on 7-point Likert scales. Blinded expert raters will watch the videos of each procedure and grade it using a modified Objective Structured Assessment of Technical Skills (OSATS) rating scale to determine the simulation platform's construct and convergent validity.

Study Procedure: Upon arrival, participants will read and sign an informed consent form. They will then fill out a pre-trial questionnaire assessing their demographic characteristics (e.g., sex, gender, age, institutional affiliation, etc.) as well as their baseline emotions and stress. Each participant will receive standardized written instructions on instrument use and function and presented with an image outlining the location of the three subpial resections on the ex vivo calf brain in front of them. Participants will adjust the operating microscope according to their preferences. The resections will be performed using microscissors to make an initial incision in the pia mater, bipolar forceps to lift the pia, and an ultrasonic aspirator to remove the assigned cortical area. After the first and second tasks, participants will fill out questionnaires assessing their emotions and stress once more. Finally, after the third task, novice and trainee participants will fill out a post-trial questionnaire assessing their emotions, stress, and cognitive load. Expert participants will fill out face and content validity questionnaires, followed by the post-trial questionnaire.

Significance: This study will provide validity evidence to support the educational utility of a novel ex vivo calf brain force detection system using both traditional and contemporary frameworks. For the first time in a realistic operative environment, it will be possible to monitor the force applied on the brain. The force and kinematic data collected from this case series study will be used to build an intelligent tutoring system capable of monitoring performance and mitigating errors during human surgical procedures.