We analyzed 3640 consecutive 18F-FDG PET–CT whole-body scans performed on 1972 patients for a variety of diagnostic reasons at Beth Israel Deaconess Medical Center from August 2003 through May 2006. Data on age and sex were obtained for all patients. Data on height, weight, fasting plasma glucose level, medication use, diagnosis, and smoking history were obtained for all patients who had substantial amounts of brown adipose tissue according to PET–CT scans and for a control group consisting of two patients without detectable brown adipose tissue who underwent scanning on the same day as each patient with brown adipose tissue (see Table 1 in the Supplementary Appendix , available with the full text of this article at NEJM.org). Outdoor temperatures in Boston for the dates of scans were obtained from the U.S. Weather Service.
Routine histologic and immunohistochemical assays for UCP1 with the use of polyclonal anti-mouse UCP1 antibody (Santa Cruz Biotechnology) were performed on paraffin sections. PET–CT images were acquired with the use of a Discovery LS multidetector helical PET–CT scanner (GE Medical Systems).20 (link) In areas where uptake of 18F-FDG was identified by PET and the presence of fat was identified by CT, the maximal and mean standardized uptake values (SUVs), defined as the activity per milliliter within the region of interest divided by the injected dose in megabecquerels per gram of body weight, were determined. Calculations were performed with the use of OpenPACS and PET–CT Viewer shareware.21 (link) Images from Massachusetts General Hospital were acquired in a similar manner.22 (link)
Routine histologic and immunohistochemical assays for UCP1 with the use of polyclonal anti-mouse UCP1 antibody (Santa Cruz Biotechnology) were performed on paraffin sections. PET–CT images were acquired with the use of a Discovery LS multidetector helical PET–CT scanner (GE Medical Systems).20 (link) In areas where uptake of 18F-FDG was identified by PET and the presence of fat was identified by CT, the maximal and mean standardized uptake values (SUVs), defined as the activity per milliliter within the region of interest divided by the injected dose in megabecquerels per gram of body weight, were determined. Calculations were performed with the use of OpenPACS and PET–CT Viewer shareware.21 (link) Images from Massachusetts General Hospital were acquired in a similar manner.22 (link)
