Feasibility of MRI-US registration in oropharynx for transoral robotic surgery

Abstract

Trans-Oral Robotic Surgery (TORS) is an alternative surgery technique used to treat head-and-neck cancer. Compared with conventional surgery, robot assistance allows surgeons to operate within areas with restricted access, such as the oropharynx, reducing the operative morbidity, risk of reconstructive surgery and improving patient outcomes. TORS is a challenging procedure, and intra-operative Ultrasound (US) has the potential to improve anatomy visualization to lessen the cognitive load on surgeons. To date, only intra-oral US has been used in exploratory studies, but intra-oral US can interfere with robot tools. In this study, we assess the feasibility of using transcervical 3D US with TORS: we propose to place the US probe on the patient’s neck to evaluate oropharyngeal anatomy intra-operatively. We also perform the first feasibility study of image registration between transcervical 3D US and Magnetic Resonance Imaging (MRI) for the oropharynx. We collected 3D US and MRI data from five healthy volunteers and four patients with oropharyngeal cancer, and we use a semi-automatic MRI-US registration algorithm to estimate an affine transformation between the two image spaces. The average Target Registration Error (TRE) is 8.26 ± 7.41mm for healthy volunteers and 9.63 ± 5.91mm for patients, and our case studies show that image quality is the key factor for good registration. Our work shows that 3D transcervical US has the clinical potential to enable intraoperative oropharynx imaging and interventional MR guidance during TORS.