Assessment of Magnetic Resonance Imaging Neurography and Tractography for Preoperative Mapping of Pelvic Nerves

Assessment of Magnetic Resonance Imaging Neurography and Tractography for Preoperative Mapping of Pelvic Nerves

This project aims at assessing two MRI acquisition methods, neurography and tractography, for the visualization of pelvic nerves. The goal is to optimize both methods and to test them on a pool of volunteers to assess if nerves can be delineated, so as to provide an individualized mapping of nerves to surgeons before an intervention and avoid postoperative complications.

Nerves of the autonomic nervous system are frequently damaged during pelvic surgery, and those injuries may lead to postoperative complications like incontinence or impotence. This study aims at developing an imaging protocol providing images where nerves can be visualized and segmented. A simple preoperative MRI exam might yield an individualized mapping of pelvic nerves that would be combined to augmented reality, thereby providing a valuable support to guide surgeons during an intervention by indicating location of the nerves that have to be preserved.

Up to now, investigations have been carried out with a 1.5 Tesla (1.5T) MRI system on an animal model (pig). MRI is non irradiant and non invasive imaging modality that proved to be a valuable method to visualize small structures like nerves. Investigations focused on MRI neurography, an anatomical imaging method highlighting nerves, and MRI tractography, a diffusion-tensor-based imaging method allowing reconstruction of nervous fibers. However, the swine model is not ideal due to major differences with human, more particularly the fact that the human pelvis contains a lot of fat unlike the swine pelvis, which is an interesting feature as there is a good contrast between fat and tissue in MRI. Therefore, it is important to perform new investigations in healthy volunteers to refine and assess the MRI acquisitions. Those investigations will be performed with a 3Tesla (3T) system from the same manufacturer, providing the same sequences but a higher field strength which should offer higher signal. There will be no injection of contrast agent. The protocol will use standard sequences from the manufacturer with parameters adjusted for the purposes of the study. The image quality will be scored on a 5-point Likert scale (0 = no possible delineation to 4=nerves are entirely visible).

Inclusion Criteria:

• Volunteers, male or female, from 18 years old
• Volunteers able to understand the study and to provide informed consent
• Volunteers affiliated to the French social security system

Exclusion Criteria:

• Volunteer with contraindications to MRI (implanted device like pace-maker or neurostimulator, ferromagnetic materials, claustrophobia or obesity)
• Volunteer that already underwent pelvic surgery
• Volunteer pregnant or breastfeeding
• Volunteer unable to provide informed consent
• Volunteer refusing to be informed of any anomaly during an exam
• Volunteer that already received more than 4500€ of allowance for biomedical testing
• Volunteer in exclusion period (determined by a previous study or in progress)
• Volunteer having forfeited their freedom of an administrative or legal obligation
• Volunteer under guardianship
• Volunteer carrying a multiresistant bacteria