Using PET/CT bone scan dynamic data to evaluate tibia remodeling when a taylor spatial frame is used: Short and longer term differences

Abstract

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 = m a x, 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 SU V 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.