Factors Affecting Standardized Uptake Value (SUV) of Positron Emission Tomography (PET) Imaging with 18F-FDG
Kanyalak Wiyaporn MSc*, Chiraporn Tocharoenchai MSc*, Pawana Pusuwan MD**, Tawatchai Ekjeen MSc*, Suraphong Leaungwutiwong MSc***, Suchera Thanyarak MSc***
Affiliation : * Department of Radiological Technology, Faculty of Medical Technology, Mahidol University, Bangkok, Thailand ** Department of Radiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand *** Department of Nuclear Medicine and PET/CT, Bumrungrad International Hospital, Bangkok, Thailand
Objective : The purpose of the study was to study factors affecting SUV of PET imaging with 18F-FDG.
Material and Method: PET/CT Biograph 64 was used to acquire the data. A NEMA PET phantom with 6
spheres varying in diameter from 10 to 37 mm was used to mimic the human body and tumors. Background
activity of 18F in the phantom was 0.14 μCi/ml and tumor-to-background ratios (TBR) of 2:1, 5:1 and 10:1
were studied. For each TBR, thirty sinograms were acquired with 3-min scan durations. Different scan durations
varying from 3 to 20 min using a TBR of 5:1were studied and three datasets of each scan time were collected.
Sinograms were reconstructed using the Ordered Subset Expectation Maximization (OSEM) algorithm with 5
mm Full-Width-at-Half-Maximum (FWHM) Gaussian filtering. Sinograms at TBR of 5:1 were reconstructed by
varying the number of iterative updates of OSEM (N) from 8 to 168 and SUVavg and SUVmax were measured. The
percentage of underestimation of SUVs was used to study the effect of tumor size and TBR. Intraclass correlation
coefficient (ICC) was used to test the reliability of SUVmax with different scan durations.
Results : The results showed that both the SUVavg and SUVmax rapidly increased when N was < 48 and slightly
increased afterwards. At TBRs ranging from 2:1 to 10:1, the percentages of underestimation of SUVmax ranged
from 8.17 to 22.46 and that of SUVavg were ranged from 41.44 to 52.33 for 37-mm sphere and from 40.38 to
54.52 and from 48.97 to 67.73 for 10-mm sphere respectively. Different scan durations gave reliable SUVsmax
with ICC of 0.996.
Conclusion : SUVs increased as N increased. The percentage of underestimation of the SUV depended on
tumor size and TBR. Scan duration did not affect SUVs.
Keywords : Standardized uptake value (SUV), Positron emission tomography (PET), Factors affecting, 18F-FDG
