title: Optimizing 18F-FDG Uptake Time Before Imaging Improves the Accuracy of PET/CT in Liver Lesions.
abstract: (18)F-FDG PET/CT has emerged as one of the fastest-growing imaging modalities. A shorter protocol results in a lower target-to-background ratio, which can increase the challenge of identifying mildly (18)F-FDG-avid lesions and differentiating inflammatory or physiologic activity from malignant activity. The purpose of this study was to determine the delay between radiotracer injection and imaging that optimizes target-to-background ratio while maintaining counts high enough to ensure scan sensitivity.
  
  
  METHODS
  The study included 140 patients (66 male and 74 female; age range, 42-95 y) with suspected hepatic lesions as seen on an (18)F-FDG PET scan. SUV was determined as region-of-interest activity/(dose/total body weight).
  
  
  RESULTS
  The mean injected dose was 610 ± 66.6 MBq (16.5 ±1.8 mCi), with a mean glucose level of 107 ± 26.6 mg/dL (standardized to 90 mg/dL). The uptake time before imaging ranged from 61 to 158 min, with a mean of 108.8 ± 24.8 min. The P values for the correlation of SUV to time were 0.004, 0.003, and 0.0001 for malignant lesions, benign lesions, and background hepatic tissue, respectively.
  
  
  CONCLUSIONS
  An approximately 90-min time window from (18)F-FDG injection to PET imaging would significantly improve target-to-background ratio and, thus, quantitation and visual interpretation. This benefit outweighs the minimal loss in patient throughput.
authors.affiliation: Beaumont Health System, Royal Oak, Michigan zaidfaham@gmail.com.
authors.forename: Zaid
authors.initials: Z
authors.lastname: Al-Faham
authors.affiliation: Beaumont Health System, Royal Oak, Michigan.
authors.forename: Prashant
authors.initials: P
authors.lastname: Jolepalem
authors.affiliation: Beaumont Health System, Royal Oak, Michigan.
authors.forename: John
authors.initials: J
authors.lastname: Rydberg
authors.affiliation: Beaumont Health System, Royal Oak, Michigan.
authors.forename: Ching-Yee O
authors.initials: CY
authors.lastname: Wong
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001692:Biological Transport; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000008:administration & dosage / Q000378:metabolism*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007267:Injections; D008099:Liver / Q000000981:diagnostic imaging / Q000378:metabolism; D008107:Liver Diseases / Q000000981:diagnostic imaging* / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D000072078:Positron Emission Tomography Computed Tomography / Q000379:methods*; D011849:Radioactive Tracers; D059629:Signal-To-Noise Ratio; D013997:Time Factors
chemical_list: D011849:Radioactive Tracers; D019788:Fluorodeoxyglucose F18
keywords: 18F-FDG PET scan; liver lesions; target-to-background ratio