Technical Note: Feasibility of photoacoustic guided hysterectomies with the da Vinci robot

This technical note provides an overview of our work to explore the combination of photoacoustic imaging with the da Vinci surgical robot, which is often used to perform teleoperated hysterectomies (i.e., surgical removal of the uterus). Hysterectomies are the prevailing solution to treat medical conditions such as uterine cancer, endometriosis, and uterine prolapse. One complication of hysterectomies is accidental injury to the ureters located within millimeters of the uterine arteries that are severed and cauterized to hinder blood flow and enable full uterus removal. By introducing photoacoustic imaging, we aim to visualize the uterine arteries (and potentially the ureter) during this surgery. We developed a specialized light delivery system to surround a da Vinci curved scissor tool and an ultrasound probe was placed externally, representing a transvaginal approach to receive the resulting acoustic signals. Photoacoustic images were acquired while sweeping the tool across a custom 3D uterine vessel model covered in ex vivo bovine tissue that was placed between the 3D model and the light delivery system, as well as between the ultrasound probe and the 3D model (to introduce optical and acoustic scattering). Four tool orientations were explored with the scissors in either open or closed configurations. The optimal tool orientation was determined to be closed scissors with no bending of the tool's wrist, based on measurements of signal contrast and background signal-to-noise ratios in the corresponding photoacoustic images. We also introduce a new metric, d theta, to determine when the image will change during a sweep, based on the tool position and orientation (i.e., pose), relative to previous poses. Overall, results indicate that photoacoustic imaging is a promising approach to enable visualization of the uterine arteries and thereby guide hysterectomies (and other gynecological surgeries). In addition, results can be extended to other minimally invasive da Vinci surgeries and laparoscopic instruments with similar tip geometry.