A solid-state intraoperative probe system

Intraoperative beta probes must be capable of detecting relatively small amounts of radionuclide in an environment where a significant photon background exists. The probe system in this investigation consisted of two stacked ion-implanted-silicon detectors. The rear detector served as a photon monitor, whose data and very good beta detection capabilities was used to correct for photon contamination present in the front detector´s readings. Miniaturized electronics for the operation of the detectors were housed in the handle of the probe wand. The amplified signals from these electronics were sent to a power and processing module where the pulses were pulse-height discriminated. This unit also housed the rechargeable lead-acid batteries used to power the system. The two channels of TTL pulse data created by the discriminators were input to a laptop computer where the they were processed and displayed. Beta and photon detection sensitivities were measured using Fluorine-18 (positron emitter) and Indium-111 (conversion electron emitter). The probe was found to have a positron detection sensitivity (Fluorine-18) of 7.21±0.11 cps/nCi and a 0.0004±0.0389 cps/nCi photon detection sensitivity. The measured electron detection sensitivity (Indium-111) was 1.42±0.04 cps/nCi, detected photon sensitivity was 0.0034±0.020 cps/nCi. The very good beta sensitivity and low photon sensitivity indicate that this system may be a useful aid for performing radionuclide-guided cancer surgeries using either positron or electron-emitting radiopharmaceuticals