RT Journal Article
SR Electronic
T1 Revised mapping of brown fat on 18-Fluorodeoxyglucose Positron Emission Tomography / Computed Tomography
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 1157
OP 1157
VO 62
IS supplement 1
A1 Hussein Rabie Farghaly
A1 Nada Ashour
A1 Abdullah Alqarni
A1 Hatem Nasr
YR 2021
UL http://jnm.snmjournals.org/content/62/supplement_1/1157.abstract
AB 1157Aim: To identify the various anatomical regions of 18-Fluorodeoxyglucose (18-FDG) avid brown adipose tissue (BAT) and to create a body map that can demonstrate the common and possible uncommon patterns of activated 18-FDG avid BAT. Material and Methods: We retrospectively reviewed all Positron Emission Tomography/Computed Tomography (PET/CT) studies from 2011 to 2019 for the presence of FDG BAT uptake. Data collected included patients’ demographics, clinical indication, regions of FDG avid BAT, and date of the scan. Image interpretation was performed to localize the sites and extent of BAT FDG uptake on PET/CT scans. Sites of FDG avid BAT were classified into either superficial (typical) or deep. To assess the extent of activated FDG avid BAT, a quantitative brown fat score (BFS) was developed for the overall brown fat (BFS-O), Typical brown fat (BFS-T), and atypical brown fat (BFS-A) by summation of the number of involved body regions in each scan. The presence and extent of brown fat were tested in relation to the time of the year the scan was performed. To the study, the year was divided into 2 unequal seasons according to the average weather in Riyadh, Saudi Arabia, a hot season of 7 months (April to October) and a cold season of 5 months (November to March). We used an unpaired student T-test to compare the mean values of continuous variables. ROC analysis was used to define the cutoff values for BFS that best identifies the patient subgroups associated with each season of the year. Chi square test was used to compare differences in frequency between categorical variables. Pearson correlation was used to assess the correlation between scores. Results: The study population included 291 patients (mean age of 27.59±13.02years;161(55.3%)females). The most frequent sites for active BAT were supraclavicular, cervical, axillary, and paravertebral and were detected in 95.5%,79.7%,72.5%, and 50.95% of patients, respectively. These sites are relatively more superficial in a location with all patients showing at least one of these sites involved and were considered typical sites. The other deeper sites of BAT were less frequently activated (50.5%) and were considered atypical sites, in a descending frequency these sites are abdominal paraaortic, mediastinal, perihepatic, suprarenal, subscapular, paracolic, retrocrural, perinephric, para-psoas, pericardial, subpectoral and gluteal (Table 1). The mean BFS-O and BFS-A were significantly higher in the cold season compared to the hot season of the year (4.24±2.05vs3.59±1.69;p=0.004) and (1.21±1.46vs0.67±1.05;p<0.001). A cutoff value for BFS-O of >4 based on ROC analysis (p=0.0081) was best to identify patients’ subgroups associated with the cold or hot season of the year with sensitivity, specificity, PPV, NPV and accuracy of 42.3%, 74.3%, 73.3%, 43.5% and 54.3% respectively (p=0.004). Studies performed during the cold season showed more patients with BFS-O of >4 and more patients with atypical brown fat sites compared to studies done during the hot season of the year (73.3%vs26.7%; p=0.004) and (71.4%vs28.6%; p=0.002). A positive correlation was found between BFS-T and BFS-A (r= -0.344; p<0.001). The BFS-O, BFS-T and BFS-A were inversely correlated to patients’ age (r=-0.214; p<0.001),(r=-0.232;p<0.001)and(r=-0.135;p=0.021) respectively. Patients with BFS-O of >4 or with atypical brown fat sites had a younger mean age (24.29±8.67vs29.46±14.63;p<0.001)and (25.95±11.31vs29.26±14.41;p<0.03).Conclusion: Both typical and atypical sites for BAT were identified. When active BAT is seen it is almost always seen in one or more typical sites while the deeper atypical sites are only noted in a fraction of these patients who have more extensive BAT activation and are rarely seen if the more superficial typical sites are not involved. More extensive and more atypical sites of BAT involvement were associated with the cold season of the year as well as with younger age.