PT - JOURNAL ARTICLE AU - Boktor, Raef R. AU - Walker, Gregory AU - Stacey, Roderick AU - Gledhill, Samuel AU - Pitman, Alexander G. TI - Reference Range for Intrapatient Variability in Blood-Pool and Liver SUV for <sup>18</sup>F-FDG PET AID - 10.2967/jnumed.112.108530 DP - 2013 May 01 TA - Journal of Nuclear Medicine PG - 677--682 VI - 54 IP - 5 4099 - http://jnm.snmjournals.org/content/54/5/677.short 4100 - http://jnm.snmjournals.org/content/54/5/677.full SO - J Nucl Med2013 May 01; 54 AB - 18F-FDG PET qualitative tumor response assessment or tumor-to-background ratios compare targets against blood-pool or liver activity; standardized uptake value (SUV) semiquantitation has artifacts and is validated by a stable normal-tissue baseline. The aim of this study was to document the normal intrapatient range of scan-to-scan variation in blood-pool SUV and liver SUV and to identify factors that may adversely affect it (increase its spread). Methods: Between July 2009 and June 2010, 132 oncology patients had 2 PET/CT scans. Patient preparation, acquisition, and reconstruction protocols were held stable, uniform, and reproducible. Mean SUV (body weight) values were obtained from 2-dimensional regions of interest in the aortic arch blood pool and in the right lobe of the liver. Results: Of the 132 patients, 65 had lymphoma. Their mean age was 62.5 y. The group’s mean serum glucose level was 6.0 mmol/L at the first visit and 5.9 mmol/L at the second visit. The mean 18F-FDG dose was 4.1 MBq/kg at the first visit and 4.0 at the second. At the first visit, the group’s mean blood-pool SUV was 1.55 (SD, 0.38); at the second, 1.58 (SD, 0.37)—not statistically different. The group’s mean liver SUV was 2.17 (SD, 0.44) at the first visit and 2.29 (SD, 0.44) at the second (P = 0.005). Visit-to-visit intrapatient variation in blood-pool and liver SUVs had gaussian distributions. The variation in blood-pool SUV had a mean of 0.03 and SD of 0.42. The variation in liver SUV had a mean of 0.12 and SD of 0.50. Using 95th percentiles, the reference range in our patient population for intrapatient variation was −0.8 to 0.9 for blood pool SUV and −0.9 to 1.1 for liver SUV. Subanalysis by cancer type and chemotherapy suggested that the rise in liver SUV between the 2 visits was largely due to the commencement of chemotherapy, but no factors were identified as systematically affecting intrapatient variation, and no factors were identified as increasing its spread. Conclusion: In our patient cohort, the reference range for intrapatient variation in blood-pool and liver SUVs is −0.8 to 0.9 and −0.9 to 1.1, respectively.