TY - JOUR T1 - Variability in SUV biodistribution in delayed PET-MR studies JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 2090 LP - 2090 VL - 52 IS - supplement 1 AU - Martin Lord AU - Antonio Figueiral AU - Eric Fleury AU - Jean-Pierre Willi AU - Magalie Viallon AU - Jean-Noël Hyacinthe AU - Susanne Heinzer AU - Habib Zaidi AU - Osman Ratib Y1 - 2011/05/01 UR - http://jnm.snmjournals.org/content/52/supplement_1/2090.abstract N2 - 2090 Objectives To evaluate changes in biodistribution of tracer uptake in different organs measured at two different points in time to assess variability of SUV measurements in delayed imaging when PET-MR study is performed over an hour following a PET-CT scan. Methods In the process of evaluation of a new hybrid PET-MR scanner two consecutive PET scans were obtained after injection of FDG in 48 patients undergoing a PET-MR study following a PET-CT scan. The average delay between the first PET study (PET-CT) and the second PET study (PET-MR) was 94 ± 25 minutes ranging from 49 minutes to 138 minutes. Changes in biodistribution of tracer uptake were measured from 10 anatomical regions including brain, cerebellum, lungs, liver, heart, colon, muscle and bones as well as in tumor and metastatic lesions when present. Results The delay between the two scans being usually over an hour significant change in biodistribution of FDG tracer was observed in all cases. These changes were confirmed form SUV quantitative ROI measurement of different tissue uptake. While in general, pathological tracer uptake in malignant lesions seemed to increase between the first and the second scan, there was significant difference in delayed changes in uptake of different organs. Conclusions Very little is known about changes in FDG tissue uptake in normal organs over long periods of time after injection. Our study shows significant variability with different trends in different organs. This enforces the need for very strict control of time delays of image acquisition in comparing SUV between different studies since normal changes in biodistribution can significantly affect these measurements ER -