ACPSEM position paper: the safety of magnetic resonance imaging linear accelerators.

Magnetic Resonance Imaging linear-accelerator (MRI-linac) equipment has recently been introduced to multiple centres in Australia and New Zealand. MRI equipment creates hazards for staff, patients and others in the MR environment; these hazards must be well understood, and risks managed by a system of environmental controls, written procedures and a trained workforce. While MRI-linac hazards are similar to the diagnostic paradigm, the equipment, workforce and environment are sufficiently different that additional safety guidance is warranted. In 2019 the Australasian College of Physical Scientists and Engineers in Medicine (ACPSEM) formed the Magnetic Resonance Imaging Linear-Accelerator Working Group (MRILWG) to support the safe clinical introduction and optimal use of MR-guided radiation therapy treatment units. This Position Paper is intended to provide safety guidance and education for Medical Physicists and others planning for and working with MRI-linac technology. This document summarises MRI-linac hazards and describes particular effects which arise from the combination of strong magnetic fields with an external radiation treatment beam. This document also provides guidance on safety governance and training, and recommends a system of hazard management tailored to the MRI-linac environment, ancillary equipment, and workforce.

The role of motion tracking in assessing technical skill acquisition using a neonatal 3D-printed thoracoscopic esophageal atresia/tracheo-esophageal fistula simulator.

INTRODUCTION: Acquiring the technical skills required for thoracoscopic repair of esophageal atresia with tracheo-esophageal fistula (EA/TEF) is challenging. A high-fidelity 3D-printed pediatric thoracoscopic EA/TEF simulator has been developed to address this issue. This study explored motion-tracking as an assessment tool to distinguish between surgeons of different expertise using the simulator. METHODS: Participants performed a single intracorporeal suture between the esophageal ends in EA with TEF. Total relative path lengths of the right and left surgical instruments were recorded during the task. Each video-recorded attempt was assessed by a blinded pediatric surgeon using a modified Objective Structured Assessment of Technical Skills (OSATS) score. Data recorded as median (range) and statistical significance as p<0.05. RESULTS: The task was performed by 17 participants. The median OSATS scores identified a significant difference between experts and novices. A difference between left- and right-hands was only found in the mid-skill level group. Right-hand path length was greatest in novices and lowest in experts. Left-hand path length was greatest in novices and the mid-skill level group compared to experts. CONCLUSION: Experts had the lowest total path length for either hand, suggesting they had the greatest efficiency of movement. The similar high path lengths in both hands for novices indicate their relatively low level of skill with either hand. The difference between right- and left-hand path lengths in the mid-skill level group likely reflects the improved right-handed technical skills in contrast to the still developing left hand. Further focus on the left hand during simulation training may improve left-handed economy of movement.

Construct validation of a 3D printed neonatal thoracoscopic simulator: Can it measure expertise?

BACKGROUND: acquiring technical expertise for neonatal thoracoscopy is challenging. To address this, we designed a fully synthetic thoracoscopic simulator for which we established its construct validity. METHODS: three thoracoscopic tasks were assessed: ring transfer, needle pass and incision of a blind upper esophageal pouch (EA cut). Participants watched instructional videos with accompanying written instructions for each task before having their attempt video recorded. All tasks were marked by three blinded pediatric surgeons using a modified Objective Structured Assessment of Technical Skills (OSATS). Scores were assessed using appropriate statistical analysis and inter-rater reliability was analyzed by interclass correlation coefficient (ICC). RESULTS: 23 participants completed the ring transfer and needle pass and 21 the EA cut: 5 experts (consultant surgeons), 5 intermediate (registrars on a training program) and 13 novices (medical students, house surgeons or non-training registrars). All three tasks distinguished between novice and intermediate/expert (ring transfer p = 0.00001, needle pass p = 0.0004 and EA cut p = 0.0014, respectively). Interrater reliability was good for ring transfer and needle pass but poor for EA cut. CONCLUSION: the tasks distinguished between novice and intermediate/expert but not between expert and intermediate. In needle pass and EA cut, there was a trend for the experts to score higher than intermediate participants. Ring transfer and needle pass tasks achieved construct validity, had good interrater reliability and were found to be useful in assessing a novice surgeon's progression towards the intermediate level. Distinguishing between intermediate and expert may require assessment of more complex tasks such as intracorporeal suturing and tying. LEVEL OF EVIDENCE: II.

End-User Input into the Design and Validation of a Synthetic Thoracoscopic Esophageal Atresia/Tracheo-Esophageal Fistula Simulator.

Introduction: Thoracoscopic repair of esophageal atresia and tracheo-esophageal fistula (EA/TEF) is challenging. We addressed this by designing a fully synthetic simulator of the procedure and described the design process and how its content validity was assessed. Methods: An iterative design and assessment of content validity was undertaken in three stages. Data were collected from participants who trialed the model and completed a survey of their experience (adapted from Barsness et al.). Results: The model was trialed by participants of varying experience. Each design refinement improved the model's fidelity and validity. For the last iteration of the simulator, the observed averages (out of a maximum of 5) were: value as a training tool 4.8, relevance 4.6, physical attributes 4.5, realism of material 4.25, realism experience 4.17, and ability to perform tasks 3.77. Conclusion: An iterative design process based on end-user feedback has led to a synthetic simulator that has achieved a high level of content validity. This model has advantages over other EA/TEF simulators in that it is relatively inexpensive and does not use animal tissue, thus removing ethical and procurement issues. It was rated highly for its value and relevance to training.

Critical design and validation considerations for the development of neonatal minimally invasive surgery simulators.

BACKGROUND/PURPOSE: Pediatric surgical trainees have limited exposure to advanced minimally invasive surgery (MIS) during their clinical training, particularly for cases such as esophageal atresia/tracheoesophageal fistula (EA/TEF). Simulation on validated neonatal models offers an alternative means of training that may augment traditional forms of training; but to be useful, they must fulfill certain criteria. METHODOLOGY: Review of the currently available MIS, thoracoscopic and laparoscopic, simulators for pediatric surgery, and identification of those factors that contribute to their fidelity and validity as a training tool that must be incorporated in the design of future simulation models. RESULTS: There are few neonatal laparoscopic and thoracoscopic models currently available, or in the research stage. To our knowledge, there is no commercially available, synthetic, high fidelity and low cost thoracoscopic model in existence. Use of animal tissue has disadvantages of ethical dilemmas, cost, and logistic and procurement issues. Newer synthetic models need to be validated for fidelity, to replicate those components of the operation that pose the greatest technical challenge, and incorporate means of measuring acquisition of technical expertise. CONCLUSION: This review describes the principles that need to be considered to develop low cost, validated high-fidelity MIS simulator that can be used for training, and that is capable of measuring the acquisition of the technical skills that can be applied to the repair of complex procedures such as esophageal atresia. Level of evidence III.

Growth rate of corpus callosum in very premature infants.

BACKGROUND AND PURPOSE: It is desirable to develop a bedside method for assessing cerebral development in the very premature infant to monitor the effectiveness of interventions aimed at improving cerebral development. Our aim was to describe the growth trajectory of the corpus callosum (CC) on cranial sonography in very premature infants. METHODS: We recruited 100 very-low-birth-weight infants admitted to a single regional level III neonatal intensive care unit from November 1998 to November 2000. Cranial sonography images of the CC were obtained for 64 (32 boys) infants (mean gestational age, 28 weeks; range, 23-33 weeks) in the first week of life and at term equivalency. The growth rate of the CC was compared in the 64 study infants to the expected growth rate of 0.20-0.27 mm/day from antenatal data and correlated with clinical outcome at 2 years of age by using Mental Development Index (MDI) and Psychomotor Development Index (PDI). RESULTS: The average growth rate of the CC was half of that expected from antenatal data. Mean growth rates were similar for all gestational ages (mean, 0.11 mm/day; range, 0.05-0.29; P = .4). The CC at term equivalency was longer for those in MDI class 2 (mean, 44.3 mm) compared with MDI class 3 (mean 40.2 mm; P = .003) as well as for PDI class 2 versus 3 (P = .017). CONCLUSION: Measurement of the length of the CC at cranial sonography is reproducible. Those with poorer neurodevelopmental outcomes have a shorter CC at term equivalency. The CC grows at a much lower rate postnatally than in utero among very premature infants.