Adding photoacoustic imaging to some robotic surgery procedures may reduce the number of injuries that inadvertently occur, according to a recent study in the Journal of Medical Imaging.

The research specifically looked at hysterectomies and potential damage to the ureter during the procedure. About 600,000 of hysterectomies are performed each year in the United States. The surgeries are increasingly being performed with robotic assistance, especially the da Vinci teleoperated surgical robot—it provides increased dexterity, reduced hospital stays, 3-D stereoscopic visualization, less blood loss and a shorter recovery period.

However, the surgery is risky: the surgeon must cut and cauterize the uterus’ arteries to remove it without hurting the ureter, which connects the kidneys to the bladder and is just millimeters away. Unfortunately, as many as 70 percent of ureter injuries are not detected during surgery, requiring additional operations to correct the damage and causing medical complications.

The researchers, who were affiliated with the Photoacoustic and Ultrasonic Systems Engineering (PULSE) Lab at Johns Hopkins University in Baltimore, theorized that image guidance would help locate the ureter and uterine arteries and reduce the incidence of ureter injury.

However, since ultrasound would be hard to operate during surgery and would not distinguish between the two types of vessels, they suggested photoacoustic imaging be used to visualize the ureter and the uterine arteries and help guide the teleoperated hysterectomy. The photoacoustic images could be displayed on the same master console that the surgeon is using for the teleoperation.

“To guide teleoperated hysterectomies, we envision that optical fibers surrounding a da Vinci surgical tool would illuminate the surgical site. The uterine arteries, which have higher optical absorption than surrounding tissue, would absorb this light, undergo thermal expansion and generate a sound wave to be detected with a transvaginal ultrasound probe,” they explained. Because metal also can absorb the light, the robotic tool could also be seen in the image.

They designed a prototype custom light delivery imaging system that surrounds a da Vinci robotic scissor tool. They used a mock operating room that contained a da Vinci robot, and used a 3-D printed model of the uterine artery, surrounded by bovine tissue to simulate the optical and acoustic scattering that would occur. They then repeatedly teleoperated the arm, sweeping the scissor in different “wrist” positions over the area.

They found that it was feasible to integrate the imaging with the robotic surgery to improve the targeting of the uterine arteries during a hysterectomy. They also learned that small angle differences can affect their ability to see the vessels because the scissor could block the light, but that the four wrist positions viewed have the potential to produce sufficient images for photoacoustic guidance.

“Results indicate that photoacoustic imaging is a promising approach to enable visualization of the uterine arteries to guide hysterectomies (and other gynecological surgeries). These results are additionally applicable to other da Vinci surgeries and other surgical instruments with similar tip geometry,” the authors conclude.

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