Beta‐ray imaging surgical scintillation detector with visible light photon counter readout

Abstract

Advances in medical imaging and microneurosurgery over the last 20 years have greatly increased the prospect of locating and removing the prominent mass of a brain tumor, yet delineating the tumor boundary on the millimeter scale during surgery remains ambiguous. This thesis presents the development of a scintillation detector that images distributions of beta‐ray radiation concentrated in tumor tissue via an appropriate radiopharmaceutical. A modular design allows detector heads of various sizes to couple to photodetectors via fiber optics. The detectors are hand‐held, maneuverable, and resolve beta‐ray distributions from under 1 mm in extent. Intended use is following the removal of the main neoplasm, and the injection of a tumor specific, beta‐ray labeled radiopharmaceutical such as used in PET. The short beta‐ray range means the detector is sensitive only to surface activity. The aim is to guide a surgeon when removing residual malignant tissue. Images formed with this device allow rapid assay of the tissue bed, and distinction between concentrations of high activity and high background rates. The detector design uses a novel solid‐state photomultiplier, the visible light photon counter (VLPC). The VLPC is an impurity band‐gap avalanche photodiode with high gain (∼25 000) and high quantum efficiency (∼70%) capable of detecting single photons.