Usefulness of partial volume effect-corrected F-18 FDG PET/CT for predicting I-131 accumulation in the metastatic lymph nodes of patients with thyroid carcinoma

Improved Quantification of 18F-FDG PET during 131I-Rituximab Therapy on Mouse Lymphoma Models after 131I Prompt Emission Correction

¹⁸F-FDG Positron Emission Tomography (PET) is used to monitor tumor response to ¹³¹I-therapy, but is confounded by prompt emissions (284, 364, 637, and 723 keV) from ¹³¹I, particularly in animal PET imaging. We propose a method for correcting this emission in ¹⁸F-FDG PET. The ¹³¹I prompt emission effect was assessed within various energy windows and various activities. We applied a single gamma correction method to a phantom and in vivo mouse model. The ¹³¹I prompt emission fraction was 12% when 300 µCi of ¹³¹I and 100 µCi of FDG were administered, and increased exponentially with escalating ¹³¹I activity for all energy windows. The difference in spill-over ratio was reduced to <5% after ¹³¹I prompt emission correction. In the mouse model, the standard uptake value (SUV) did not differ significantly between FDG PET only (gold standard) and FDG PET after ¹³¹I prompt emission-correction, whereas it was overestimated by 38% before correction. Contrast was improved by 18% after ¹³¹I prompt emission correction. We first found that count contamination on ¹⁸F-FDG follow-up scans due to ¹³¹I spilled-over count after ¹³¹I rituximab tumor targeted therapy. Our developed ¹³¹I prompt emission-correction method increased accuracy during measurement of standard uptake values on ¹⁸F-FDG PET.

Local Retention and Combination Effects of Biocompatible Doxorubicin-Loaded and Radioiodine-Labeled Microhydrogels in Cancer Therapy

I-131-labeled chitosan microhydrogels (I-131-CMH) that are retained at an injection site without leaking free I-131 into normal tissue can provide opportunities to improve cancer therapy. This study focuses on the development of doxorubicin-loaded I-131-CMH (Dox-I-131-CMH) for use in radiochemotherapy against cancer. The radiolabeling of I-131-CMH was found to be stable over a period of 2 weeks with no disassociation of free I-131, and Dox showed a sustained release from the CMH. When I-131-CMH were injected into the thigh muscle or tumor tissue, in vivo gamma imaging showed a retention at the injection site with no significant leakage of I-131 into other areas of normal tissue, and after an intrahepatic arterial injection, I-131-CMH were selectively retained in the liver. Dox-I-131-CMH had significant synergistic therapeutic effects of radiation and chemotherapy on mouse breast cancer models. In this regard, Dox-I-131-CMH may be a new alternative agent for cancer therapy.