Assessing Astatine-211 SPECT Image Quality in Relevant Organs

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2025-06-06

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2024

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Abstract

Theranostics is an evolving approach in nuclear medicine that aims to combine diagnostic and therapeutic value into a single agent of delivery. With increased interest in alpha-emitting radionuclides for their short effective range and high linear energy transfer, astatine-211 is a promising radionuclide for therapy applications. Previously at Duke University, the ability to image and quantitate images of astatine-211 was investigated and determined to be a challenge due to attenuation and collimation effects on desired photons for imaging, and undesirable high energy emission contributions. This research builds on that previous work to investigate the image quality extent of single photon planar and SPECT imaging for astatine-211 when considering relevant organs that could be at risk for radiation damage based on the distribution of the molecule carrying the At-211. The investigation is broken down into several experiments that provide the basis for understanding the potential of astatine-211 to perform as an imaging radionuclide, and the needed factors for image reconstruction including the appropriate linear attenuation coefficient and k-factor for dual-energy scatter correction. Two phantom designs were created. One was used to provide a baseline image quality comparison of four radionuclides (F-18 for PET, Tc-99m, Lu-177, and At-211 for single photon planar imaging). The other represented the salivary glands in the head and kidneys and tumors in the torso. Imaging the same realistically large phantom showed that only the fluorine-18 PET images 1 cm targets successfully, while technetium-99m and lutetium-177 are comparable in imaging 2 cm and 3 cm targets, and astatine-211 can only image 3 cm targets. This work successfully simulated the salivary glands and kidneys in an anthropomorphic phantom. The results indicated that the use of a k-factor of 1.1 is reasonable in the scatter correction of imaging astatine-211, which effectively reduced downscattered gamma rays in the images. Additionally, the results confirm that the medium energy general purpose collimator is better suited than the low energy high resolution collimator for imaging astatine-211 with improved SNR and comparable noise quality.

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Wong, Ye Wan Evan (2024). Assessing Astatine-211 SPECT Image Quality in Relevant Organs. Master's thesis, Duke University. Retrieved from https://hdl.handle.net/10161/31081.

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