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%-SUV(max), r = 92%, and r (s) = 91%-SUV(mean)), suggesting static scans could substitute for dynamic studies. Patlak-like slope differences of 0.1 min(−1) or greater between examinations and SUV(max) 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.