The DEPICT Project - Developing a gamma camera system for dosimetry of molecular radiotherapy
Lucy McAreavey is a third year PhD student in the Nuclear Physics group at the University of Liverpool. She graduated from the University of Liverpool in 2015 with a BSc in Physics with Medical Applications. She is currently collaborating with other nuclear physicists, medical physicists and radiation detector experts on the DEPICT project which aims to facilitate quantitative imaging for dosimetry of thyroid molecular radiotherapy with radioiodine (131I). Lucy has presented her work at conferences in Europe and the US and has had papers published on her research in the Journal of Instrumentation and Nuclear Future, the journal of the Nuclear Institute. She also engages in multiple outreach projects, and has been selected to be a Soapbox Science speaker at this years Bluedot festival.
Molecular radiotherapy (MRT) is a cancer treatment that involves the internal administration of radiopharmaceuticals to deliver a high radiation dose to targeted tumour tissue, whilst minimising the damage to surrounding healthy tissue. Current MRT treatment plans are undesirably generic as the administered activity is fixed for a certain procedure or scaled according to patient weight. However, it has been found that for the same initial administered activity, the uptake and retention of the MRT therapeutic agents, and hence the radiation dose, can vary by up to two orders of magnitude in different patients due to the wide range of biokinetics [1,2]. The absorbed radiation dose in the tissue of interest would ideally be calculated through accurate real-time quantitative imaging of the radiation distribution in the patient.
Single Photon Emission Computed Tomography (SPECT) can be used to image the radiation distribution, if gamma rays are emitted. In current SPECT systems however, quantitative activity information is lost due to dead time because diagnostic SPECT systems are not optimised for high-activity therapeutic measurements. The aim of the Dosimetry Imaging with CZT (DEPICT) project is to develop a custom-designed SPECT system to facilitate quantitative imaging, based on a collimated, pixelated CZT detector and a high-energy parallel hole collimator. The system will give an assessment of the radiation dose delivered to the patient, tailored specifically for MRT of the thyroid with radioiodine (131I).
The CZT detector has been characterised and optimised for 131I MRT  and gamma-ray images of a thyroid phantom have been acquired with a custom-designed high-energy parallel hole collimator and high-activity 131I. Preliminary 3D reconstruction data of calibration vials has been acquired to assess the feasibility of obtaining accurate quantitative information with the DEPICT system.
 D. Flux et al., A dose-effect correlation for radioiodine ablation in differentiated thyroid cancer. European Journal of Nuclear Medicine and Molecular Imaging (2010).
 Sgouros et al., Patient-Specific Dosimetry for 131I Thyroid Cancer Therapy Using 124I PET and 3-Dimentional-Internal Dosimetry (3D-ID) Software. Journal of Nuclear Medicine (2004).
 McAreavey et al., Characterisation of a CZT detector for dosimetry of molecular radiotherapy, Journal of Instrumentation 12 (2017).