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

## TL;DR

This study uses PET/CT scans to assess tibia bone remodeling in patients treated with a Taylor Spatial Frame, comparing dynamic data with static methods.

## Contribution

A Patlak-like analysis is introduced to approximate blood activity without blood samples, enabling dynamic evaluation of bone remodeling.

## Key findings

- Patlak-like and SUVm slopes showed strong agreement, suggesting static scans can replace dynamic studies.
- Positive Patlak-like slope differences of 0.1 min−1 or greater and SUVmax differences of ~5 indicate good remodeling progress.
- Negative Patlak-like slope differences of −0.06 min−1 suggest poor remodeling progress in the studied cohort.

## Abstract

Eighteen consecutive patients, treated with a Taylor Spatial Frame for complex tibia conditions, gave their informed consent to undergo Na18F− 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 SUVm(t) (m = max, mean) and a series of slopes were computed as (SUVm(t
i) − SUVm(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 ((VOIp(t
i)/VOIe(t
i))−(VOIp(t
j)/VOIe(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 SUVm 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.