Ultrasonic vitrectomy device-tissue interaction characterization

Abstract

Purpose : Electrical signatures of ultrasonic vitrectomy devices during tissue interaction have not been fully characterized and are not well understood as a theoretical model does not exist. Electrical measurements in BSS and pig vitreous show the ultrasonic energy-tissue interaction behavior and reveal high sensitivity of the ultrasonic probe to tissue type and sub-type. This is a first demonstration of ultrasonic vitrectomy tissue detection capability that may detect tissue type in real-time during surgery.

Methods : Measurements: Electrical data of Vitesse 25 gauge vitrectomy probe, driven by Stellaris Elite^TM (Bausch & Lomb, LLC) was measured using voltage and current probes on a mixed signal oscilloscope (Tektronix MSO 4054) with 1MS/s high resolution acquistion rate. The vitrectomy probe was operated in BSS and two forms of pig vitreous with 60 um stroke and 100 mmHg vacuum. Vitreous was harvested from a fresh pig eye and separated into two samples; viscous liquid (water and hyluronan) and thick gel-like (with collagen matrix).

Results : Vitesse shows an average power increase of 70% when operated in thick gel-like vitreous (Vit Base) compared to BSS with a 36% increase in voltage, a 16% increase in current, and a 20% increase in impedance. When operated in the viscous liquid (thin vitreous), Vitesse shows an average power increase of 47% when compared to BSS with a 23% increase in voltage, an 18% increase in current, and a 6% increase in impedance. A two sample unpaired t-test of the electrical parameters in tissue vs BSS with a significance level of 0.01 show extremely high statistical significance (p < 0.001).

Conclusions : There is a substantial difference in the electrical characteristics required to operate on posterior tissue types and BSS. With all four electrical parameters showing statistically significant results, this displays proof of concept that ultrasonic devices may be able to sense changes in tissue interaction during surgery in real-time.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

Figure 1: Vitesse 25 gauge vitrectomy probe operating in BSS, Thin Vitreous (viscous liquid), and Vitreous Base (thick gel-like).

 

Figure 2: Left: Thick, gel-like Pig Vitreous with visible collagen matrix (Vit Base in Figure 1). Right: Viscous liquid (water and hyaluronic acid) (Thin Vitreous in Figure 1).