| Abstract|| |
Objectives: The aim of this study was to assess the visibility of mandibular canal (MC) on cone beam CT (CBCT) images using a medical review monitor under two different calibration modes. The effect of age, gender, and location of the dental implant site was also assessed. Materials and Methods: CBCT images of 428 dental implant sites were selected for the study. Images were displayed twice on a medical review monitor using two different calibration modes: standard and DICOM, and two observers evaluated the visibility of the MC using four-point scoring scale (1–4, poor to excellent). Cohen Kappa was used to assess intra and inter-rater reliability. Chi-square test was used to compare proportions of MC visibility by gender and location and one-way ANOVA was used to compare mean age and MC visibility. Results: Each observer classified the visibility of MC with a total agreement of 100% between DICOM mode and standard mode (Kappa = 1, P < 0.001 for each observer). In each mode, a strong agreement (inter-rater reliability) was detected between the observers (Cohen's kappa = 0.88 for both modes, P < 0.001) with a percent agreement of 95.3% for each mode. Gender and location were not statistically associated with MC visibility (P > 0.05). Age, however, was a significant predictor of MC visibility (P < 0.05). Conclusions: DICOM calibration had no added value over standard calibration for assessing the visibility of MC at dental implant sites on a medical review monitor. Only the age had significant effect on the visibility.
Keywords: Calibration, cone beam CT, dental implant, mandibular canal, medical monitors, visibility
|How to cite this article:|
Alkhader M, Hudieb M, Kheirallah K. Effect of calibration of a medical review monitor on the visibility of mandibular canal at dental implant sites: A cone beam CT study. Indian J Dent Res 2020;31:883-7
|How to cite this URL:|
Alkhader M, Hudieb M, Kheirallah K. Effect of calibration of a medical review monitor on the visibility of mandibular canal at dental implant sites: A cone beam CT study. Indian J Dent Res [serial online] 2020 [cited 2021 Apr 15];31:883-7. Available from: https://www.ijdr.in/text.asp?2020/31/6/883/311654
| Introduction|| |
Dental implants are considered one of the best options to treat patients with edentulous areas and to restore missing teeth., Implant success rate and 10-year survival rate was more than 90%,, even with the presence of multiple risk factors like smoking, bruxism and load, high success rate was reported too.
In order for dental implant treatment to be successful, proper dental implant planning must be conducted preoperatively, in which bone quantity and quality must be evaluated in addition to pathologies and anatomical structures at dental implant site. Needless to say that mandibular canal (MC) is one of the most important anatomical structures that must be evaluated if implants have to be inserted in the posterior mandible.
The location of MC inside bone can be determined depending on the visibility of its superior and inferior border., Several factors can affect the visibility of the MC like its location, shape, voxel size, exposure parameters, and angulation of image cross-section,,,, and different studies have been conducted to investigate the effect of other factors using different imaging modalities.,,,, Among these modalities, cone beam CT (CBCT) is considered imaging of choice due to its low radiation dose and high image resolution.
CBCT images can be displayed on commercial or medical monitors. Medical monitors are characterized by different specifications like high luminance, luminance stabilization over long period of time, and pre-calibrated to the Digital Imaging and Communications in Medicine Greyscale Display Function (DICOM GSDF); therefore, medical monitors are preferred over commercial monitors in medical practice.
Calibration to DICOM optimizes brightness and gray level, thus, resulting in better matching for human visual system and better diagnostic performance. Dicom calibration can be done using specific softwares to ensure that GSDF curve was met according to Barten's model. According to this, the percentage of contrast change required for a detection threshold at low background luminance is higher than that at high background luminance.
The superior performances of calibrated monitors has been shown in previous studies,, using 2D and 3D CBCT images for different dental tasks like caries detection, visualizing pathology, and normal anatomy. However, to the best of our knowledge, there is no single study which evaluated the effect of monitor calibration on the visibility of MC at dental implant sites, therefore, this study was conducted.
| Materials and Methods|| |
In our retrospective study, images for all patients who underwent CBCT examination for dental implant treatment at our dental radiology clinic were retrieved and evaluated. Only cases with missing lower second premolars and molars were included in the study. The number of cases included was 428. Cases with artifacts or pathology affecting the visibility of MC at the implant sites were excluded. The study protocol was approved by our institutional review board (Protocol. 320/2015).
A KODAK 9500 Cone Beam 3D System (Carestream, Rochester, NY) CBCT apparatus with flat panel detector was used. The imaging area of CBCT is a cylinder with a height of 15–20.6 cm and a diameter of 9–18 cm providing isotropic cubic voxels with sides of 0.2–0.3 mm. Only cases examined with 0.2 mm were included in the study. The exposure parameters were as follows: 90 kV as a tube voltage, 10 mA as a tube current, and an exposure time of 10.8 s.
Examinations were performed by 360° rotation in the occlusal position with the patient standing and closing their teeth.
Under subdued lighting, one calibrated oral radiologist (MA) with 11 years of experience with CBCT and dental implants was responsible for generating cross-sectional images at proposed mandibular implant sites after creating pseudo-panoramic images, and then closing the case for a second evaluation after 1 month. Under same conditions, Images were evaluated for a third and fourth time by one calibrated oral implantologist (MH) with 10 years of experience.
The curved slicing module was used for creating pseudo-panoramic images, and the arch was manually created on the horizontal section. The horizontal section was automatically displayed by the software and the thickness of the focal trough was adjusted in order to fit the mandible of each patient.
To generate cross-sectional images, a vertical blue line on the displayed panoramic image was moved to the proposed implant site while keeping it perpendicular to the occlusal plane. For each implant site, three cross-sectional images were generated by setting the interslice distance to 2 mm; therefore, the diameter of the proposed implant was 4 mm. The visibility of MC was considered poor and given a score of 1 if it was not detected in any of cross sectional images, a score of 2 (good) if it was visible or possible to be delineated from the surrounding bone marrow spaces on one section, a score of 3 (very good) if it was visible on two sections, and a score of 4 (excellent) if it was visible on three sections [Figure 1],[Figure 2],[Figure 3],[Figure 4].
|Figure 1: Example on poor visibility of MC on which the MC was not detected on all CBCT slices|
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|Figure 2: Example on good visibility of MC on which the MC was detected on one CBCT slice|
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|Figure 3: Example on very good visibility of MC on which the MC was detected on two CBCT slices|
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|Figure 4: Example on excellent visibility of MC on which the MC was detected on all CBCT slices|
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Under two different calibration modes: standard and DICOM, all images were evaluated on Dell Medical Review 22 Monitor (MR2217) with installed CS 3D imaging viewer (CS 3D imaging viewer, 3.2.9 Carestream, Rochester, NY). Window settings were fixed for all cases before evaluation.
Data was presented using numbers/percentages and means (SD) as appropriate. Cohen Kappa and percent agreement for each observer in the two modes were calculated to assess reliability of standard mode compared to DICOM mode. Chi-square test was used to compare proportions of visibility by gender and location. One way ANOVA were used to compare mean age and visibility. Post-hoc Tuckey's test was used to compare the mean age for each visibility score. Alpha level was set at 0.05 for all tests.
| Results|| |
A total of 428 patients were included in the current analysis; about two-thirds of which were females (60.5%). Mean age (SD) was 51.02 (13.6) years. In each mode, a strong agreement (inter-rater reliability) was detected between the radiologist (observer 1) and implantologist (observer 2) (Cohen's kappa = 0.88 for both DICOM and standard modes, P < 0.001) with a percent agreement of 95.3% for each mode.
Using the standard mode, each observer was able to accurately classify visibility with a total agreement of 100% compared to the DICOM mode (Kappa = 1, P < 0.001 for each observer) [Table 1].
|Table 1: Visibility for each observer under standard mode and DICOM mode|
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The effect of gender, location, and age on visibility is presented in [Table 2]. Gender and location were not statistically associated with visibility (P > 0.05 for gender and location). Age, however, was a significant predictor of visibility (P < 0.05). Post-hoc Tuckey's test showed that the age of patients who had very good visibility (53.1 years) was significantly higher than that of those who had excellent visibility (49.9 years) (P = 0.019). No other significant results were found in the mean age.
| Discussion|| |
In this study, the two observers similarly identified the MC when images are visualized under both of the calibration modes, this indicate that DICOM calibration had no added value over standard calibration for assessing the visibility of MC.
This similarity in performance is due to number of factors, one of them is the dim light in reading environment. Liukkonen et al. showed that under dim light reading environment, there is no significant differences in reading chest radiograph using different monitors (medical or non-medical, calibrated to DICOM or without calibration).
We evaluated images on Dell medical review monitor (MR 2217). The brightness of the monitor in both of calibration modes is almost similar to each other, its 180 cd/m2 in DICOM and 175 cd/m2 in standard calibration. This might be an appropriate explanation for not detecting a significant difference between both of calibration methods as shown in Tofangchiha et al. study. In their study, medical and conventional monitors with similar luminance were used, and this resulted in similar accuracy in diagnosis of vertical root fracture.
In our current study, MC was considered visible if we were able to separate it from surrounding bone marrow spaces, and it was unnecessary to be fully corticated, thus, the same visibility of MC under both of calibration modes might be due to compensatory behavior by observers.
In contrast to previous studies which showed usefulness of DICOM calibration in caries detection,,, this was not applicable to our case, since visibility of MC is different diagnostic task and cross-sectional images were not used in those previous studies. Moreover, using same monitor for comparison as in our case is better than using different monitors with different specifications.
Our results revealed that the MC visibility was not related to the subject's gender or the location of the dental implant site, meanwhile, Age was a significant predictor of visibility. The age of patients who had very good visibility (53.1 years) was significantly higher than that of those who had excellent visibility (49.9 years). This might be explained by the fact that the bone density is decreasing with age and resulted in difficulty in detecting the MC on cross sectional CBCT images. On the other hand, Miles et al. found that the gender and location had significant effects on MC visibility. This might be due to using thicker CBCT slices or using different criteria for scoring MC visibility.
In conclusion, DICOM calibration had no effect on the visibility of MC at dental implant sites, therefore, using standard calibration is considered sufficient for such diagnostic task.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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Dr. Mustafa Alkhader
Department of Oral Medicine and Oral Surgery, Faculty of Dentistry, Jordan University of Science and Technology, P.O. Box 3030, Irbid 22110
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2]