Radiation Protection and Occupational Exposure on ⁶⁸Ga-PSMA-11–Based Cerenkov Luminescence Imaging Procedures in Robot-Assisted Prostatectomy

Abstract

<b>Introduction:</b> Cerenkov Luminescence Imaging (CLI) was successfully implemented in the intraoperative context as a form of cancer radio-guided surgery, showing promise in the detection of surgical margins during robot-assisted radical prostatectomy (RARP). The current study was designed to provide a quantitative description on the occupational radiation exposure to surgery and histopathology personnel from CLI-guided RARP after injection of [⁶⁸Ga]Ga-PSMA-11 using a single injection PET/CT / CLI protocol. <b>Methods:</b> Ten patients with preoperative [⁶⁸Ga]Ga-PSMA-11 administration and intraoperative CLI were included. Patient dose rate was measured, pre-PET/CT (<i>N</i> = 10) and post-PET/CT (<i>N</i> = 5) at one meter distance of four patient regions (A: head, B: right side, C: left side and D: feet). Electronic Personal Dosimeters (EPD) were used for intraoperative occupational exposure (<i>N</i> = 10). Measurements included the first surgical assistant and scrub nurse at the operating table and the CLI imager / surgeon at the robotic console, encompassing the whole duration of surgery and CLI image acquisition. An estimation of exposure to histopathology personnel was performed by measuring prostate specimens (<i>N</i> = 8) on a Germanium detector. <b>Results:</b> The pre-PET/CT measured dose rate values averaged (± SD) 5.3 ± 0.9 µSv/h. This corresponds to a patient-specific dose rate constant for positions B and C of 0.047 µSv/h*MBq. Post PET/CT dose rate values averaged (± SD) 1.04 ± 1.00 µSv/h. The patient-specific dose rate constant values were 0.011 µSv/h*MBq, 0.026 µSv/h*MBq, 0.024 µSv/h*MBq and 0.003 µSv/h*MBq, corresponding to regions A-D. EPD readings revealed an average (±SD) personal equivalent dose of 9.0 ± 7.1, 3.3 ± 3.9, 0.7 ± 0.7 µSv for first surgical assistant, scrub nurse and CLI imager / surgeon, respectively. The median (Interquartile range - IQR) Germanium detector measured activity of the prostate specimen was 2.96 kBq (2.23; 7.65 kBq). <b>Conclusion:</b> Single injection of [⁶⁸Ga]Ga-PSMA-11 PET/CT / CLI procedures are associated with a reasonable occupational exposure level, if kept under 110 procedures per year. Excised prostate specimen radionuclide content was below the exemption level for Gallium-68. Dose rate based calculations provide a robust estimation for EPD measurements.