Using PET/CT Bone Scan Dynamic Data to Evaluate Tibia Remodeling When a Taylor Spatial Frame Is Used: Short and Longer Term Differences

Eighteen consecutive patients, treated with a Taylor Spatial Frame for complex tibia conditions, gave their informed consent to undergo Na(18)F(-) PET/CT bone scans. We present a Patlak-like analysis utilizing an approximated blood time-activity curve eliminating the need for blood aliquots. Additionally, standardized uptake values (SUV) derived from dynamic acquisitions were compared to this Patlak-like approach. Spherical volumes of interest (VOIs) were drawn to include broken bone, other (normal) bone, and muscle. The SUV m (t) (m = max, mean) and a series of slopes were computed as (SUV m (t i ) - SUV m (t j ))/(t i - t j ), for pairs of time values t i and t j . A Patlak-like analysis was performed for the same time values by computing ((VOI p (t i )/VOI e (t i ))-(VOI p (t j )/VOI e (t j )))/(t i - t j ), where p = broken bone, other bone, and muscle and e = expected activity in a VOI. Paired comparisons between Patlak-like and SUV m slopes showed good agreement by both linear regression and correlation coefficient analysis (r = 84%, r s = 78%-SUVmax, r = 92%, and r s = 91%-SUVmean), suggesting static scans could substitute for dynamic studies. Patlak-like slope differences of 0.1 min(-1) or greater between examinations and SUVmax differences of ~5 usually indicated good remodeling progress, while negative Patlak-like slope differences of -0.06 min(-1) usually indicated poor remodeling progress in this cohort.