Evaluation of a new small-pixel CdTe spectroscopic detector in dual-tracer SPECT brain imaging

Simultaneous dual-tracer brain imaging has the potential to shorten patient pathways in the diagnosis of neurodegenerative diseases, but the poor spectral resolution of conventional gamma cameras limits the utility of this technique. Solid state detectors offer improved capability to distinguish between two radioisotopes, but the technology has yet to be fully evaluated in the field of scintigraphic neuroimaging. We present imaging results for a new small-pixel CdTe detector in simultaneous dual-radioisotope scintigraphy of a brain phantom containing Tc-99m and I-123. Quantitative comparison is made with images of the same phantom obtained using a conventional gamma camera. We show that the CdTe detector offers improved scatter rejection and greatly reduced cross-talk between the energy windows. In addition, the new detector is able to resolve low-energy fluorescence x-rays from the source, which could be incorporated into SPECT reconstruction algorithms. Details of the planned development of the detector into a clinical demonstrator are discussed.