A dual surface barrier detector unit for beta-sensitive endoscopic probes

The excellent targeting of positron-emitting radiopharmaceuticals such as ¹⁸F-Fluorodeoxyglucose (FDG) to cancer has inspired the development of a number of handheld beta probes to assist in surgeries. The use of these devices could potentially be expanded to utilization in minimally invasive techniques such as endoscopy. In this work, we describe the development and initial testing of a miniature beta-sensitive detector unit suitable for use in minimally invasive procedures. The detector consisted of two surface barrier detectors (active area=3 mm diameter and depletion layer depth=0.5 mm) mounted back-to-back in a PC board frame. This geometry allowed the rear detector to be shielded from the beta flux striking the front detector (most photons passed through the detector) so that its signal could be used to correct for photon contamination of the beta flux detected by the front detector. Initial testing of the system included measurement of the beta and photon detection sensitivities (1.87±0.02 cps/nCi (0.05±5.4×10^-4 cps/Bq) and 1.2×10^-4±9×10^-5 cps/nCi (3.24×10^-6±2.4×10^-6 cps/Bq), respectively) and mapping of the two-dimensional point spread function. The spatial resolution of the system is 3.05 mm FWHM. The potential effectiveness of the detector in clinical use was investigated by surveying a simulated esophagus containing radiotracer-avid areas of cancer. The results from this test demonstrated the ability of the detection system to distinguish focal areas of increased FDG uptake from surrounding normal tissue in a realistic annihilation photon flux environment. These encouraging results indicate that this detector unit is suitable for incorporation into a new beta-sensitive endoscopic probe system currently under development.