Assessment of da Vinci tool and wrist rotations that maximize fluence in photoacoustic-guided surgery: A simulation study

In minimally invasive photoacoustic-guided surgical procedures, one approach to achieve required target illumination is to attach light sources to a surgical tool, such as a scissor tool attached to a da Vinci robot for teleoperated surgeries. However, the tool tip can present an obstacle to light transmission when placed in particular orientations. We quantify the optical fluence resulting from different orientations of the da Vinci scissors tool, using Monte Carlo simulations to measure fluence at varying depths below the tissue surface. A metallic model of the da Vinci scissors tool was placed above simulated tissue in an orientation mimicking a surgical procedure. The da Vinci scissors tool was modeled with pivot points corresponding to two joints: (1) the wrist joint, which is near the base of the scissors tool tip and (2) the scissors joint, around which the scissors open and close, closer to the tip of the tool. Light sources representing optical fibers were placed around the base of the tool, facing the tissue. Simulations were performed with 154 total parameter combinations of different positions (i.e., seven wrist joint rotations using a dedicated wrist joint rotation model, seven scissor joint rotations using a dedicated scissor joint rotation model, with each joint in each model additionally rotated about an orthogonal axis, from 0^◦ to -180^◦ in 18^◦ increments). The resulting fluence was measured in a 10 mm radius region of interest (ROI) located 1 mm below the tissue surface under the tool. The maximum normalized fluence difference between two simulated tool orientations was 18-21%. These results establish a new simulation framework to enhance our understanding of the impact of specific tool orientations on the fluence delivered to tissue, which has the potential to impact the associated photoacoustic image quality.