Imaging quality of F-18-FDG PET/CT in the inpatient versus outpatient setting

Abstract

The purpose of this study is to investigate potential differences in the image quality of inpatient versus outpatient F-18-FDG PET/CT to provide evidence for appropriate policies and procedures to be promulgated on inpatient referrals. 100 consecutive inpatient and 100 outpatient F-18-FDG PET/CT scans were compared from the same time period and PET/CT scanner. Each study was evaluated for a subjective overall rating (optimal vs. suboptimal), and also by objective measurements (SUVmean) in four background structures (brain, blood pool, liver, and muscle). 96 outpatient scans were rated optimal and 4 suboptimal whereas corresponding numbers for inpatient scans were 77 and 23 (p < 0.001). Of the objective indices, cerebellar SUV was significantly different in inpatient versus outpatient (5.3 vs. 6.9; p < 0.001) as well as suboptimal versus optimal rated groups (4.8 vs. 6.3; p < 0.001). While mean blood glucose was higher for inpatients (108.01 vs. 101.49 mg/dl; p = 0.017), it was not significantly different between optimal and suboptimal exams. Linear regression analysis between blood glucose levels and cerebellar uptake revealed an inverse relationship (R = -0.38, p < 0.001). There was a significantly higher number of inpatient PET/CT scans rated as suboptimal in comparison to outpatient scans. Decreased cerebellar uptake was present in suboptimal rated studies and in inpatient studies. Altered biodistribution is thus a potential etiology of reduced scan quality among inpatients. These findings, if duplicated among other readers and centers, may form the basis of quality control recommendations for inpatient PET/CT ordering patterns.