Can gray values derived from CT and cone beam CT estimate new bone formation? An in vivo study

Objectives: The main aim of this study was to investigate whether Hounsfield unit derived from computed tomography (HU/CT) and gray value derived from cone beam computed tomography (GV/CBCT) can predict the amount of new bone formation (NBF) in the defects after bone reconstruction surgeries. Materials and methods: Thirty calvaria defects created in 5 rabbits and grafted with both radiolucent (RL, n = 15) and radiopaque (RO, n = 15) bone substitute materials were evaluated, 8 weeks postoperatively. The defects were scanned by multislice computed tomography (Somatom®, Siemens Healthineers, Erlangen, Germany) and CBCT (NewTom VG®, Qualitative Radiology, Verona, Italy). MSCT and CBCT scans were matched to select the exact region of interest (ROI, diameter = 5 mm and height = 1 mm). HU/CT and GV/CBCT of each ROI were obtained. Mean amount of NBF in whole of the defects was measured using serial histomorphometric assessment. We investigated the correlation between HU/CT and GV/CBCT, HU/CT and NBF, and GV/CBCT and NBF generally, and separately among the RL or RO grafted defects, by linear generalized estimating equation modeling. Receiver operation characteristic analysis was performed to check the accuracy of HU/CT and GV/CBCT in diagnosing more than 10% NBF in the samples.
Results: There were linear correlations between HU/CT and GV/CBCT, HU/CT and NBF, and GV/CBCT and NBF.
Conclusion: According to the results, both HU/CT and GV/CBCT can be considered as fairly good predictors for assessment of the amount of NBF following bone reconstruction surgeries.