Abstract
Positron emission tomography (PET) may provide important information on the therapeutic response of radiopharmaceutical therapy (RPT) during therapy. The radiation emission from the RPT radionuclide may disturb the coincidence detection and impair the image resolution. In this study we tested the feasibility to perform intratherapeutic PET on three preclinical PET systems. Methods: Using 22Na point sources and phantoms filled with 18F, and a phantom filled with either 99mTc or 177Lu, the coincidence count rate and the spatial resolution when both a PET and a therapeutic radionuclide were present in the PET camera, were evaluated. 99mTc was used as a substitute for a generic therapeutic radioisotope, since it has a suitable half-life and is easy obtainable. Results: High activities of 99mTc deteriorated the coincidence count rate from the 18F-filled phantom with a 22Na point source on all three systems evaluated. One of the systems could to a high degree correct the count rate with its dead time correction. The spatial resolution was degraded at high activities of 99mTc for all systems. On one of the systems 177Lu increased the coincidence count rate and slightly affected the spatial resolution. The results for high activities of 177Lu were similar to those for 99mTc. Conclusion: Intratherapeutic imaging might be a feasible method to study RPT treatment response. However, some sensitive preclinical PET systems, unable to handle high count rates, suffer count losses and may also introduce image artifacts.
- Copyright © 2016 by the Society of Nuclear Medicine and Molecular Imaging, Inc.