Dual-wavelength photoacoustic imaging for guidance of hysterectomy procedures

Gynecologic surgery accounts for 75% of all intraoperative injuries to the ureters, which often occur due to the close proximity of the ureter to the uterine artery. We propose dual-wavelength photoacoustic imaging in order to distinguish the ureter from the uterine artery, identify the position of the surgical tool in proximity to these critical structures, and assist with guidance of hysterectomy procedures. Experiments were preformed in a pilot human cadaver study and a dual-wavelength approach was introduced to visualize the uterine artery and a ureter filled with urine and methylene blue. The ureter location was identified with low contrast at a wavelength of 750 nm and higher contrast at a wavelength of 690 nm, resulting in a 5.8 dB contrast difference in photoacoustic signals from the ureter at these two different wavelengths. The uterine artery was identified at laser wavelengths of both 690 nm and 750 nm, with similarly high contrasts of 17.4 dB and 16.0 dB, respectively. By using a dual-wavelength display, both the ureter and the uterine artery were identified and their position was estimated in the photoacoustic image. The proximity of a surgical tool tip to the ureter was additionally estimated based on the information provided in the dual-wavelength photoacoustic display and mapped to an auditory signal. This auditory information can be provided as either an alternative or an addition to photoacoustic images that inform surgeons of the risk of injury. Results highlight the promise of dual-wavelength photoacoustic imaging to achieve our ultimate goal of avoiding accidental ureteral injuries during hysterectomies and possibly other similar gynecologic surgeries and procedures.