β + surgical radio-guidance using a small Compton-angles collimation probe

Abstract

The fields of radio-guided surgery and interventional nuclear medicine benefit from a growing array of technologies that aid novel healthcare interventions. Among them, surgery probes able to efficiently detect β + emitters are essential to localize tumors previously detected in PET images. Different methods have been proposed for 18F radio-guidance within the body such as detection of 511 keV annihilation photons using electronically or mechanically collimated probes. The main limitations to the widespread use of these techniques are the lack of precise directional capabilities and inadequate sensitivity. We first used the Monte Carlo simulation platform GATE to determine the optimal signal to noise ratio that can be achieved with an ideal probe. Then, we focused on investigating a small Compton-angles collimation prototype probe followed by the construction of an initial proof of concept demonstrator. The performance of the small Compton-angles collimation probe was compared with a commercial probe based on mechanical collimation in terms of sensitivity and directionality. Monte Carlo simulations showed that in case of an ideal probe, with a tumor of 1 cm diameter positioned 5 mm under the skin and with a SUV of 2, the measured signal to background ratio would be of the order of 25%. The small Compton-angles collimated probe prototype showed significantly improved directionality compared to the commercial probe with mechanical collimation, despite having a sensitivity lower than the commercial probe. Monte Carlo simulations provide insights into the substantial impact of the background on the measured signal. Furthermore, the application of small Compton-angles collimation yields promising outcomes, particularly in terms of improving the directionality, with the objective of enhancing the detection of tumors. In addition, the studied prototype probe sensitivity can possibly be improved by upgrading the detector crystal material and geometry.