Effect of different thresholds on the accuracy of linear and volumetric analysis of native- and grafted-bone.

The study aimed to evaluate the accuracy of Micro-CT in linear and volumetric measurements in native (NB) and grafted bone (GB) areas. A total of 111 biopsies of maxillary sinuses grafted with deproteinized bovine bone (DBB) in humans were evaluated. The linear measurements were performed to measure the length of the NB and GB. Furthermore, the amount of mineralized tissues at the NB and GB was performed. In the histomorphometry analysis the percentage of mineralized tissues at the NB and GB was obtained in two histological sections while the mineralized tissues were measure in the micro-CT varying the thresholds of the grayscale varying from 90-250 to 90-150 with 10 levels of variation between each one was applied. Then these data were correlated in order to check the higher r level between the histomorphometry and micro-CT thresholds intervals. The linear length of the NB was 2.44±0.91mm and 2.48±1.50mm, respectively, for micro-CT and histomorphometry (r =0.57), while the linear length of the GB was 3.63±1.66mm and 3.13±1.45mm, respectively, for micro-CT and histomorphometry (r =0.74) Histomorphometry showed 45.91±11.69% of bone in NB, and 49.57±5.59% of bone and biomaterial in the GB. The total volume of mineralized tissues that were closest to the histometric analysis were 43.75±15.39% in the NB (Threshold:90-240; r = 0.50) and 51.68±8.42% in the GB (Threshold:90-180; r =-0.028). The micro-CT analysis showed good accuracy in the linear analysis in both portions of the biopsies but for volumetric analysis just in NB.