title: Ambient temperature and cardiac accumulation of 18F-FDG.
abstract: Warming patients by changing the ambient environment (rather than core temperature) has been reported to reduce brown adipose tissue activity, thereby reducing artifacts in (18)F-FDG PET. Nonetheless, a reduction in cardiac uptake of (18)F-FDG has been incidentally noted during ambient warming. This study examined the impact of seasonal variations in ambient temperatures on cardiac uptake of (18)F-FDG.
  
  
  METHODS
  Consecutive (18)F-FDG PET patients were recruited into summer and winter cohorts. The protocol was highly standardized; however, data were excluded when scanning took place other than 60 min after injection. Mean and maximum counts per pixel in the cardiac region and cardiac standardized uptake value were determined and correlated with the daily minimum, maximum, and mean temperature (day of scan), mean temperature on the scan day and preceding 2 d (3-d window), and mean temperature 1, 2, 3, and 4 wk before scanning.
  
  
  RESULTS
  No statistically significant differences were noted between cohorts (summer and winter) for age, sex, weight, height, or dose. As expected, the summer cohort was associated with statistically higher minimum, maximum, and mean temperatures, longer days, and greater sunlight hours (all P < 0.001). The mean and maximum heart counts were statistically higher in winter than summer (P = 0.031 and P = 0.024, respectively). The cardiac standardized uptake value was statistically higher for winter than summer (P = 0.026). The key factors in cardiac accumulation of (18)F-FDG were the minimum temperature on the day of the scan and the 3-d mean temperature.
  
  
  CONCLUSIONS
  Cardiac accumulation of (18)F-FDG is influenced by the ambient temperature, in particular the minimum temperature on the day of the scan and the 3-d average temperature before the scan. Further investigation is warranted to examine the impact of this observation on clinical protocols and cardiac (18)F-FDG PET study results.
authors.affiliation: Faculty of Science, Charles Sturt University, Wagga Wagga, New South Wales, Australia.
authors.forename: Samantha
authors.initials: S
authors.lastname: O'Loughlin
authors.affiliation: Faculty of Science, Charles Sturt University, Wagga Wagga, New South Wales, Australia Australian School of Advanced Medicine, Macquarie University, Sydney, New South Wales, Australia gcurrie@csu.edu.au.
authors.forename: Geoffrey M
authors.initials: GM
authors.lastname: Currie
authors.affiliation: Macquarie Medical Imaging, Macquarie University Hospital, Sydney, New South Wales, Australia; and.
authors.forename: Marko
authors.initials: M
authors.lastname: Trifonovic
authors.affiliation: Faculty of Science, Charles Sturt University, Wagga Wagga, New South Wales, Australia Australian School of Advanced Medicine, Macquarie University, Sydney, New South Wales, Australia Cardiac Health Institute, Sydney, New South Wales, Australia.
authors.forename: Hosen
authors.initials: H
authors.lastname: Kiat
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000378:metabolism*; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D012621:Seasons; D013696:Temperature
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: 18F-FDG PET; ambient temperature; cardiac