Hardware, Software, and Scanning Issues Encountered during Small Animal Imaging of Photodynamic Therapy in the Athymic Nude RatNathan Cross; Rahul Sharma; Davood Varghai; Chandra Spring-Robinson; Nancy L. Oleinick; Raymond F. Muzic Jr.; David Dean

摘要

Introduction: Small animal imaging devices are now commonly used to study gene activation and model the effects of potential therapies. We are attempting to develop a protocol that non-invasively tracks the affect of Pc 4-mediated photodynamic therapy (PDT) in a human glioma model using structural image data from micro-CT (μCT) and/or micro-MR (μMR) scanning and functional data from ~(18)F-fluorodeoxy-glucose (~(18)F-FDG) micro-PET (μPET) imaging. Methods: Athymic nude rat U87-derived glioma was imaged by μPET and either μCT or μMR prior to Pc 4-PDT. Difficulty insuring animal anesthesia and anatomic position during the μPET, μCT, and μMR scans required adaptation of the scanning bed hardware. Following Pc 4-PDT the animals were again ~(18)F-FDG μPET scanned, euthanized one day later, and their brains were explanted and prepared for H&E histology. Histology provided the gold standard for tumor location and necrosis. The tumor and surrounding brain functional and structural image data were then isolated and co-registered. Results: Surprisingly, both the non-PDT and PDT groups showed an increase in tumor functional activity when we expected this signal to disappear in the group receiving PDT. Co-registration of the functional and structural image data was done manually. Discussion: As expected, μMR imaging provided better structural discrimination of the brain tumor than μCT. Contrary to expectations, in our preliminary analysis ~(18)F-FDG μPET imaging does not readily discriminate the U87 tumors that received Pc 4-PDT. We continue to investigate the utility of μPET and other methods of functional imaging to remotely detect the specificity and sensitivity of Pc 4-PDT in deeply placed tumors.