Ultrasound and Photoacoustic Imaging for Enhanced Differential Diagnosis of Rectal Cancer

-Emerging technique in which a short-pulsed laser beam penetrates diffusely into a tissue sample, causing the release of acoustic waves due to a transient temperature rise -The transient acoustic waves, or photoacoustic waves, are then measured around the sample by US transducers -The resolution of the devices can be altered by changing the wavelengths of laser light and spectrum analysis of the receiver. In this manner, human colorectal pathology will be examined under multiple types of photoacoustic ranges (broadly termed photoacoustic microscopy and photoacoustic imaging)

-An endorectal imaging device using coregistered photoacoustic and ultrasound imaging has been constructed. This probe is used to perform in vivo imaging among patients with rectal pathology intraoperatively.

After initial training, the study surgeon will grade the lesion as either PAM/US non-cCR or PAM/US cCR at the time of PAM/US imaging. The study radiologist, blinded from the surgeon's read, will also grade the lesion based on MRI. PAM/US-CNNs provide a real-time imaging tool to assist the reader team in diagnosis. The pathological outcomes of the patients will be assessed based on Tumor Regression Score by standard pathologic evaluation. The study will evaluate the effect of the assistance of PAM/US-CNNs for trained readers on their performance i.e. sensitivity and specificity of their diagnosis of rectal cancers from images obtained from the testing cohort of (Group 2) patients.