Effect of slice inclination and object position within the field of view on the measurement accuracy of potential implant sites on cone-beam computed tomography

Accuracy of implant height and width measurement with triaxial rotation method based on cone-beam CT

Objective

To investigate the accuracy of implant height and width measurement in the mandibular and maxillary first molar region based on cone-beam CT (CBCT) data, and to establish an accurate method for bone measurement in the implant region.

Materials and methods

CBCT images of 122 patients with implant in mandibular or maxillary first molar region were retrospectively collected. Two methods were used to measure sagittal height (SH), coronal height (CH), sagittal width (SW), and coronal width (CW) of implants. Method 1 (general method): the images were analyzed using the built-in software NNT 9.0 software. SHl, CHl, SWl, and CWl were measured on the reconstructed sagittal and coronal based on the radiologist's own experience. Method 2 (triaxial rotation method): the raw data were demonstrated in Expert mode of NNT 9.0 software, in which the coronal axis and sagittal axis were rotated paralleling to the long axis of the implant for reconstruction, and then SH2, CH2, SW2, and CW2 were measured on the reconstructed sagittal and coronal images. The results of two methods were compared with the actual implant size (H0, W0). Paired T-test was performed for statistical analysis. Dahlberg formula was used to check the measurement error.

Results

For method 1, there was no significant differences between SHl and H0 (P > 0.05), but significant differences between CHl and H0, SWl and W0, and CWl and W0 (P < 0.05). For method 2, there were no significant differences between all measurements and actual size (P > 0.05). The random error range measured using Dahlberg formula was 0.157-1.171 mm for general method and 0.017-0.05 mm for triaxial rotation method.

Conclusion

The triaxial rotation method is accurate for implant height and width measurements on CBCT images and could be used in pre-operatively bone height and width measurement of potential implant sites.

Effect of Mandible Phantom Inclination in the Axial Plane on Image Quality in the Presence of Implant Using Cone-Beam Computer Tomography

Purpose To assess the effect of 30° phantom inclination on image quality in the presence of an implant using cone-beam computed tomography (CBCT). Materials and methods Three series of eight scans were taken and categorized by a range of 87-90 kVp and 7.1 mA, and 8 mA. For the first CBCT series, the phantom was placed on a flat plane. For the second series, the phantom was inclined at 30° in the axial plane. For the third series, inclined scans were re-oriented and included for statistics. In total, 24 scans were used for statistics. i.e., eight scans at three different planes (flat plane, inclined plane, and re-oriented inclined plane). All the images were analyzed for artifact and contrast-to-noise ratio (CNR) on ImageJ software. Results The inclination of the dry human mandible phantom by 30° reduces the artifact (p <0.05). However, the CNR was not affected by the phantom inclination. Conclusion The appropriate inclination of the head can significantly reduce the metal artifact in the presence of implants and thus improve the CBCT image quality for post-operative follow-up.

A diagnostic accuracy study on an innovative auto-edge detection technique for identifying simulated implant fractures on radiographic images

Implant fracture is a rare but devastating complication of treatment in partially or fully edentulous patients which requires prompt diagnosis. Nevertheless, studies on defining the most accurate technique for the detection of implant fractures are lacking. In the present study, the Canny edge detection algorithm was applied on multiple radiographic modalities including parallel periapical (PPA), oblique periapical (OPA), and cone beam CT (CBCT) with and without metal artifact reduction (MAR) to examine its accuracy for diagnosis of simulated implant fractures. Radiographs were taken from 24 intact implants and 24 implants with artificially created fractures. Images were evaluated in their original and Canny formats. The accuracy of each radiograph was assessed by comparison with a reference standard of direct observation of the implant. The greatest area under the receiver operating characteristic curve belonged to Canny CBCT with MAR (0.958), followed by original CBCT with MAR (0.917), original CBCT without MAR = Canny CBCT without MAR = Canny OPA (0.875), Canny PPA (0.833), original PPA = original OPA (0.792), respectively. The Canny edge detection algorithm is suggested as an innovative method for accurate diagnosis of clinically suspected implant fractures on CBCT and periapical radiographies.