TY - JOUR T1 - Counting Rate Characteristics and Image Distortion in Preclinical PET Imaging During Radiopharmaceutical Therapy JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1964 LP - 1970 DO - 10.2967/jnumed.116.175539 VL - 57 IS - 12 AU - Emma Mellhammar AU - Magnus Dahlbom AU - Johan Axelsson AU - Sven-Erik Strand Y1 - 2016/12/01 UR - http://jnm.snmjournals.org/content/57/12/1964.abstract N2 - PET may provide important information on the response during radiopharmaceutical therapy (RPT). Emission of radiation from the RPT radionuclide may disturb coincidence detection and impair image resolution. In this study, we tested the feasibility of performing intratherapeutic PET on 3 preclinical PET systems. Methods: Using 22Na point sources and phantoms filled with 18F, as well as a phantom filled with either 99mTc or 177Lu, we evaluated the coincidence counting rate and spatial resolution when both a PET and a therapeutic radionuclide were in the PET system. Because 99mTc has a suitable half-life and is easy obtainable, we used it as a substitute for a generic therapeutic radionuclide. Results: High activities of 99mTc deteriorated the coincidence counting rate from the 18F-filled phantom and the 22Na point source on all 3 systems. The counting rate could be corrected to a high degree on one of the systems by its dead-time correction. Spatial resolution was degraded at high 99mTc activities for all systems. On one of the systems, 177Lu increased the coincidence counting rate and slightly affected the spatial resolution. The results for high 177Lu activities were similar to those for 99mTc. Conclusion: Intratherapeutic imaging might be a feasible method of studying the response to RPT. However, some sensitive preclinical PET systems, unable to handle high counting rates, will have count losses and may also introduce image artifacts. ER -