Measurements of mandibular canal region obtained by cone-beam computed tomography: a cadaveric study

Objective. The objective of this study was to assess the accuracy and reproducibility of cone-beam CT measurements of specific distances around the mandibular canal by comparing them to direct digital caliper measurements. Methods. Six formalin-fixed hemimandible specimens were examined using the ILUMA cone-beam CT system. Images were obtained at 120 kVp, 3.8 mA, and a voxel size of 0.2 mm, with an exposure time of 40 seconds. Specimens were cut into sections at 7 locations using a Lindemann burr, and a digital caliper was used to measure the following distances on both the anterior and posterior sides of each section: Mandibular Width (W); Mandibular Length (L); Upper Distance (UD); Lower Distance (LD); Buccal Distance (BD); and Lingual Distance (LID). The same distances were measured on the corresponding cross-sectional cone-beam CT images using the built-in measurement software. All caliper and cone-beam CT measurements were made by 2 independent trained observers and were repeated after an interval of 1 week. The Bland/Altman method was used to calculate intra- and inter-rater reliability. Intra-class correlation coefficients (ICCs) from 2-way random effects model were calculated. Agreements between cone-beam CT and direct digital caliper were calculated by ICC for 6 distances and 2 observers. Results. Intraobserver and interobserver measurements for all distances showed high agreement. ICCs for intraobserver agreement ranged from 0.86 to 0.97 for cone-beam CT measurements and from 0.98 to 0.99 for digital caliper measurements. ICCs between observers ranged from 0.84 to 0.97 for the cone-beam CT measurements and from 0.78 to 0.97 for the digital caliper measurements. ICCs for cone-beam CT and direct digital caliper ranged from 0.61 to 0.93 for the first observer and from 0.40 to 0.95 for the second observer. Conclusion. Accuracy of cone-beam CT measurements of various distances surrounding the mandibular canal was comparable to that of digital caliper measurements. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009; 107: e34-e42)