Quantitative SPECT for dosimetry of 131I molecular radiotherapy

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The aim of this project is to develop and evaluate the performance of a custom-designed y-ray imaging system that will facilitate quantitative dosimetry for Molecular Radiotherapy (MRT). In MRT, radiotracers are administered to deliver high radiation doses to targeted tissue with minimal damage to surrounding healthy tissue. The most common radionuclide used is the B-emitting isotope 131I, predominantly used in the treatment of thyroid cancer. The treatment plans are currently undesirably generic in that 131I is administered with an activity that is either fixed for a procedure or scaled according to patient weight. Dosimetry for MRT is extremely challenging due to limitations that arise from using diagnostic imaging systems for therapeutic imaging, and errors can arise in image quantification and spatial resolution. Therefore, it is difficult to qualify the impact of the treatment. The y-rays emitted from 131I can be imaged using a gamma camera, however, the performance of conventional imaging systems is not sufficient for dosimetry. Consequently, an optimised demonstrator system will be developed using Cadmium Zinc Telluride (CZT) detectors. Single Photon Emission Computed Tomography (SPECT) can be used to image the 364 keV 131I y-rays, therefore a SPECT detector system will be developed for therapeutic imaging based on CZT detectors and Application-Specific Integrated Circuit (ASIC) readout. This system is targeted at personalised cancer treatment plans and in turn will improve quality of life, reduce costs and enable required changes to current MRT treatment planning policies.