Variations in arm positions in FDG PET/CT

Objectives The SNM published guidelines for arm positions in whole-body (WB) FDG PET/CT. Arms at the side may produce beam-hardening artifacts over the torso. Therefore, the arms should be elevated over the head (arms up or AU) in all cancer cases except in head and neck (H/N) cancer patients where the arms should be positioned at the side (arms down or AD). We evaluated the variation in arm position in our PET center.

Methods 1489 WB PET/CT scans were reviewed and noted for arm positions. The studies were divided into H/N and non-H/N. A note was made when there was a deviation in the arm positioning from the SNM recommendation. Body mass index (BMI), age and gender were also recorded for correlation.

Results Of the 1489 studies reviewed, 1205 (81%) were non-H/N cases, and 284 (19%) were H/N cases. Of the 1205 non-H/N cases, 642 (53%) had AD (no deviation), but 563 (47%) had AU (deviation). Of the 284 H/N cases, 277 (97.5%) had AD (no deviation) and only 7 (2.5%) had AU (deviation). Deviation in arm position showed statistically significant correlations with BMI (p=.001), age (p=.02), and gender (p<.001).

Conclusions Deviation from the SNM’s recommendations for arm positions in FDG PET/CT was 54% for non-H/N cases, but only 2.5% for H/N cases. When present, deviation was more commonly noted in obese patients (BMI>25 due to body habitus), males, or patients over 60 (likely due to shoulder arthritis).