Dissertation Defense: Chiao Huang, "Single-Photon Emission Computed Tomography (SPECT) Imaging of Alpha-Emitting Radiopharmaceutical Therapy"

Title

 Single-Photon Emission Computed Tomography (SPECT) Imaging of Alpha-Emitting Radiopharmaceutical Therapy

Abstract

Alpha-emitting radiopharmaceutical therapy (alpha-RPT) utilizes alpha-emitting radiotracers to target and kill tumor cells. Since radiotracers can deposit dose in both healthy and cancerous organs, assessing organ-specific dose is crucial to balance tumor control and the safety of normal organs. Several alpha-emitting isotopes have been introduced in RPT, and most of them also emit photons that allow image-based dose assessment using single-photon emission computed tomography (SPECT). Among these isotopes, Pb-212 has gained significant interest due to its promising clinical development. However, direct imaging of Pb-212 is challenging because of the high-energy photons emitted along its decay chain. This challenge motivates the current development of an elemental-identical imaging surrogate Pb-203, which provides a better photon spectrum while maintaining the same biodistribution as its therapeutic counterpart. Multiple works have investigated the performance of SPECT imaging of the Pb-212/Pb-203 therapy-imaging pair through phantom and clinical studies. In this dissertation, we systematically investigate the advantages of using Pb-203 imaging in Pb-212 therapy through simulations and task-based measures of image quality. This dissertation consists of three parts. The first part presents a Monte Carlo simulation of SPECT imaging of both Pb-212 and Pb-203, and demonstrates the advantages of using Pb-203 in Pb-212 therapy in terms of image characteristics and photon peak separation. The second part introduces tools for task-based measures of image quality for the simulated images, including the investigation of measurement noise and variability across patients. While typical scintillator-based detectors are used in the first part, the third part explores Cadmium Zinc Telluride (CZT) semiconductor detectors. We characterize a parallel-plate detector with an energy resolution of 2.39% at 140.5 keV, and discuss the benefits of using CZT detectors in imaging alpha-emitting radiopharmaceutical therapy. Overall, this work evaluates the feasibility and performance of SPECT imaging for alpha-emitting radiopharmaceutical therapy using imaging surrogates.

Please email Jini at jini@optics.arizona.edu or Chiao at chiaohuang@arizona.edu for a Zoom link.