Actionable Feedback on Signal-to-Background Ratios During Drop-in Radioguided Surgery.

Radioguided surgery (RGS) using prostate-specific membrane antigen (PSMA)-targeted tracers is frequently hampered by relatively low intraoperative signal intensities. This limits intraoperative target discrimination when feedback relies solely on probe counts per second. We evaluated whether real-time signal-to-background ratio (SBR) feedback, integrated into the robotic console via a graphical user interface (GUI), improves surgical perception, decisiveness, and scanning efficiency during drop-in PSMA-radioguided procedures.

Methods

We retrospectively analyzed 10 patients from the TRACE-II trial undergoing salvage RGS with 99mTc-PSMA imaging and surgery. Five procedures were performed with standard counts per second feedback (control group), and 5 were performed with additional live SBR feedback (experiment group). The GUI enabled intraoperative background sampling and displayed real-time SBRs via a traffic light-style color-coded gauge. Probe trajectories were reconstructed using video-based tracking with green polyetheretherketone marker rings, and scanning performance was quantified by total scan duration and target scan duration. Statistical comparisons were made using Mann-Whitney U and Spearman correlation analyses.

Results

Fourteen PSMA-avid lesions were resected, all of which were confirmed by pathology as cancerous. Cases with real-time SBR feedback showed more focused probe trajectories and reduced procedure times. The median total scan duration decreased from 455 to 237 s (P = 0.11), and the median target scan duration decreased from 299 to 212 s (P = 0.15). Although not statistically significant in this pilot study, scan durations strongly correlated with in vivo counts (Spearman ρ = -0.74, P = 0.01). After normalization for maximum in vivo counts, median target scan duration decreased from 21.1 to 5.3 seconds per counts per second (s/cps) (P = 0.08).

Conclusion

Streaming real-time SBR feedback into the robotic console improved surgical decisiveness and perception of PSMA-avid lesions and facilitated more efficient probe handling. By digitizing intraoperative contrast information, the drop-in γ-probe provided actionable feedback that reduced cognitive load and enhanced target discrimination. These findings support future multicenter studies to establish standardized SBR-based performance metrics in RGS.