A boundary-guided transformer for measuring distance from rectal tumor to anal verge on magnetic resonance images.

Accurate measurement of the distance from the tumor's lowest boundary to the anal verge (DTAV) provides an important reference value for treatment of rectal cancer, but the standard measurement method (colonoscopy) causes substantial pain. Therefore, we propose a method for automatically measuring the DTAV on sagittal magnetic resonance (MR) images. We designed a boundary-guided transformer that can accurately segment the rectum and tumor. From the segmentation results, we estimated the DTAV by automatically extracting the anterior rectal wall from the tumor's lowest point to the anal verge and then calculating its physical length. Experiments were conducted on a rectal tumor MR imaging (MRI) dataset to evaluate the efficacy of our method. The results showed that our method outperformed surgeons with 6 years of experience (p < 0.001). Furthermore, by referring to our segmentation results, attending and resident surgeons could improve their measurement precision and efficiency.