Tumor Volume and Margin Assessment With ex Vivo 3D-ultrasound After Transoral Robotic Surgery for Oropharyngeal Squamous Cell Carcinoma

The purpose of the study is to determine the accuracy of ex vivo 3D ultrasound (US) for detecting and delineating tumor tissue of the tonsils and base of tongue post-operatively. This is a quick technique that may provide valuable information for the surgeon that can potentially improve treatment outcomes.

Placing the surgical specimen in a water bath allows for an US swipe to be performed without compressing the specimen. This reduces the deformation of the specimen by removing the pressure from conventional US scanning. A video clip can be captured by swiping across the specimen in the water bath. By motorizing this motion, the video can be converted into a 3D volume due to the known number of video frames and a constant swiping speed.

We will correlate the ex vivo 3D US scans to histopathology for the following analyses:

• Four surgeons blinded to histopathology will rate each included case in terms of tumor visibility on ex vivo 3D US scans. If visible, the surgeons will mark the tumor and the healthy tissue.
• Tumor and margins will be correlated to histopathology pre- and post-formalin fixation on a subset of cases to explore the proportion of tissue shrinkage from formalin fixation.
• Two methods of estimating tumor volume will be compared: the ellipsoidal formula and full 3D segmentation.