J. Martin Palomo

Reliability and accuracy of cone-beam computed tomography dental measurements

INTRODUCTION Dental measurements are an integral part of the orthodontic records necessary for proper diagnosis and treatment planning. In this study, we investigated the reliability and accuracy of dental measurements made on cone-beam computed tomography (CBCT) reconstructions. METHODS Thirty human skulls were scanned with dental CBCT, and 3-dimensional reconstructions of the dentitions were generated. Ten measurements (overbite, overjet, maxillary and mandibular intermolar and intercanine widths, arch length available, and arch length required) were made directly on the dentitions of the skulls with a high-precision digital caliper and on the digital reconstructions with commercially available software. Reliability and accuracy were assessed by using intraclass correlation and paired Student t tests. A P value of < or = 0.05 was used to assign statistical significance. RESULTS Both the CBCT and the caliper measurements were highly reliable (r >0.90). The CBCT measurements tended to slightly underestimate the anatomic truth. This was statistically significant only for compounded measurements. CONCLUSIONS Dental measurements from CBCT volumes can be used for quantitative analysis. With the CBCT images, we found a small systematic error, which became statistically significant only when combining several measurements. An adjustment for this error allows for improved accuracy.

Image distortion and spatial resolution of a commercially available cone-beam computed tomography machine

INTRODUCTION Our objective was to evaluate images produced by a commercially available cone-beam computed tomography (CBCT) machine (i-CAT model 9140-0035-000C, Imaging Sciences International, Hatfield, Pa) for measurement and spatial resolution (ie, the ability to separate 2 objects in close proximity in the image) for all settings and in all dimensions. METHODS A custom phantom containing 0.3 mm diameter chromium metal markers approximately 5 mm apart in 3 planes of space was developed for analyzing distortion and measurement accuracy. This phantom was scanned in the CBCT machine by using all 12 commercially available settings. The distance between the markers was measured 3 times on the 3-dimensional images by using a Digital Imaging and Communications in Medicine (DICOM) viewer and was also measured 3 times directly on the phantom with a fine-tipped digital caliper. A line-pair phantom was used to evaluate spatial resolution. Thirty evaluators analyzed images and assigned a resolution from 0.2 to 1.6 mm according to the separation of the line pairs. RESULTS There were no statistically significant differences among the 3-dimensional images for any setting, in any dimension, or in images divided by thirds in terms of measurement accuracy. Comparison of the CBCT measurements to the direct digital caliper measurements showed a statistically significant difference (P <0.01). However, the absolute difference was <0.1 mm and is probably not clinically significant for most applications. The worst spatial resolution found was 0.86 mm. Spatial resolution was lower at faster scan times and larger voxel sizes. CONCLUSIONS This CBCT machine has clinically accurate measurements and acceptable resolution.

Influence of CBCT exposure conditions on radiation dose

BACKGROUND Cone-beam computed tomography (CBCT) has been changing the way dental practitioners use imaging. The radiation dose to the patient and how to effectively reduce the dose is still not completely clear to most users of this technology. OBJECTIVE The objective of this study was to quantitate the change in radiation dose when using different CBCT settings. METHODS A CBCT machine was modified to allow different setting combinations. The variables consisted of 4 different mA choices (2, 5, 10, and 15), 2 kVp choices (100 and 120), and 3 fields of view (6 inches, 9 inches, and 12 inches). A radiation phantom with 10 thermoluminescent dosimeters (TLD) was used to measure radiation dose. One specific setting (15 mA, 120 kVp, and 12-inch FOV) was scanned 3 times to determine consistency. RESULTS The CBCT showed less than 5% variance in radiation dose values. An overall reduction in dose of about 0.62 times was achieved by reducing the kVp from 120 to 100. When reducing the field size the dose decreased 5% to 10%, while for organs that escaped the direct beam the reduction was far greater. CONCLUSIONS A reduction in radiation dose can be achieved by using the lowest exposure settings and narrow collimation.

Applications of cone beam computed tomography in the practice of oral and maxillofacial surgery.

l m i o a d h d t s roviding imaging in 3 dimensions, computed tomogaphy (CT) has had a profound effect on surgical and edical practice since its introduction in 1973. Practiioners at that time certainly marveled at the new techology, but likely were at a loss as to how to apply it or hat exactly the images meant. It was only after years of esearch, as well as the development of a whole new spect of radiology, that we have been able to apply this echnology for the benefit of our patients. In oral and maxillofacial surgery, we are accustomed o using CT in patients with trauma and pathological onditions in the hospital setting; however, in dental ractice, practitioners depend almost entirely on 2-diensional plain films. The applications and advantages f CT in dentistry remain largely unrealized. Cone beam CT (CBCT) was first developed for use n angiography. In 1998, Mozzo et al reported the rst CBCT unit developed specifically for dental use, he NewTom 9000 (Quantitative Radiology, Verona, taly). Other similar devices introduced at around that ime included the Ortho-CT, which was renamed the DX (J. Morita Mfg Corp, Kyoto, Japan) multi-image icro-CT in 2000. In 2003, Hashimoto et al reorted that the 3DX CBCT produced better image uality with a much lower radiation dose than the ewest multidetector row helical CT unit (1.19 mSv s 458 mSv per examination).

Image quality produced by different cone-beam computed tomography settings.

INTRODUCTION The aim of this study was to evaluate image quality at different cone-beam computed tomography settings and 3 fields of view. METHODS A Hitachi CB MercuRay (Hitachi Medical Systems, Tokyo, Japan) was modified to allow different setting combinations. The variables consisted of 4 milliampere settings (2, 5, 10, and 15 mA), 2 kilovolt (peak) settings (100 and 120 kV[p]), presence or absence of a copper filter, and 3 fields of view (6, 9, and 12 in). Thirty-two scans were taken on a cadaver head and 16 scans on a dry skull. The groups were divided by field of view, and the images were ranked by at least 30 judges. Diagnostic quality was addressed in a questionnaire. Descriptive statistics and rankings were calculated with Excel 2003 (Microsoft, Redmond, Wash) and the Friedman and Wilcoxon signed rank tests with SPSS software (version 14.0.1; SPSS, Chicago, Ill). RESULTS The presence or absence of a filter showed significant differences (P <.006) in 2 pairs of the 9-in field of view. Variation in kilovolt (peak) settings showed significant differences (P <.006) in the 6-in 5-mA images with a filter. Altering the milliampere settings showed significant differences (P <.008) in the 6- and 12-in groups. The 9-in group showed significant differences between 2 mA and 10 and 15 mA. Overall, the 6-, 9-, and 12-in images had diagnostic quality 56%, 99%, and 99% of the time, respectively. CONCLUSIONS Presence or absence of a filter and the kilovolt (peak) setting did not affect overall image quality. Images taken at lower milliampere settings showed good diagnostic quality.

Cone Beam CT for Diagnosis and Treatment Planning in Trauma Cases

Three-dimensional imaging offers many advantages in making diagnoses and planning treatment. This article focuses on cone beam CT (CBCT) for making diagnoses and planning treatment in trauma-related cases. CBCT equipment is smaller and less expensive than traditional medical CT equipment and is tailored to address challenges specific to the dentoalveolar environment. Like medical CT, CBCT offers a three-dimensional view that conventional two-dimensional dental radiography fails to provide. CBCT combines the strengths of medical CT with those of conventional dental radiography to accommodate unique diagnostic and treatment-planning applications that have particular utility in dentoalveolar trauma cases. CBCT is useful, for example, in identifying tooth fractures relative to surrounding alveolar bone, in determining alveolar fracture location and morphology, in analyzing ridge-defect height and width, and in imaging temporomandibular joints. Treatment-planning applications include those involving extraction of fractured teeth, placement of implants, exposure of impacted teeth, and analyses of airways.

Use of Cone Beam Computed Tomography to Volumetrically Assess Alveolar Cleft Defects—Preliminary Results

PURPOSE The purpose of this study was to determine the utility of cone beam computed tomographic (CBCT) imaging in assessing the volume of alveolar cleft defects in patients undergoing secondary cleft repair. MATERIALS AND METHODS Fourteen patients with unilateral clefts were analyzed in a retrospective study. Preoperative CBCT imaging of patients preparing to undergo secondary repair of alveolar clefts was reviewed. Using anatomic landmarks, 3 measurements were collected from CBCT images for each patient: facial width (FW), facial height (FH), and facial-palatal length (FL). These values were used to calculate the estimated volume (EV) of the cleft and thus the amount of bone graft material that would be needed to fill the defect. RESULTS The overall mean values of FW, FH, and FL were 9.7 ± 3.1, 14.07 ± 2.7, and 5.6 ± 0.8 mm, respectively. Mean EV was 489.0 ± 151.6 mm(3). The single (0.879) and average (0.956) measurements of the intraclass correlation coefficient for FH were very good to excellent. Similar data were observed for FH (single, 0.827; average, 0.935). For FL, a decreasing trend in the mean and variability over the 3 measurement times was reflected in low single (0.305) and moderate average (0.569) intraclass correlation coefficients. CONCLUSIONS CBCT imaging can be used to reliably measure FW, FH, and FL and to calculate the EV of the cleft. These data can be used by oral and maxillofacial surgeons to quantitatively assess the volume of an alveolar cleft and aid in preoperative determination of the amount of bone that will be needed to adequately graft the cleft space. This will also aid in appropriate selection of an autogenous graft donor site before surgery.

History of imaging in orthodontics from Broadbent to cone-beam computed tomography

The history of imaging and orthodontics is a story of technology informing biology. Advances in imaging changed our thinking as our understanding of craniofacial growth and the impact of orthodontic treatment deepened. This article traces the history of imaging in orthodontics from the invention of the cephalometer by B. Holly Broadbent in 1930 to the introduction of low-cost, low-radiation-dose cone-beam computed tomography imaging in 2015.

Hypoglossal nerve stimulation rescue surgery after multiple multilevel procedures for obstructive sleep apnea.

Hypoglossal nerve stimulation (HNS) is a new procedure offered for the treatment of moderate-to-severe obstructive sleep apnea (OSA) that has been shown to decrease the severity and symptoms of OSA in select patients. We report on a case of a patient with persistent symptoms and findings of OSA despite a history of multiple multilevel procedures, including an uvulopalatopharyngoplasty (UPPP) with revision, a genioglossus advancement, and a maxillomandibular advancement. The patient then underwent HNS with significant improvement of his symptoms and severity. The success of this patients HNS surgery demonstrates that we need to examine where HNS fits into the approach to surgery for OSA. There could be benefit to considering cranial nerve stimulation earlier than conventional approaches for select patients.

Cervical vertebral bone mineral density changes in adolescents during orthodontic treatment.

INTRODUCTION The cervical vertebral maturation (CVM) stages have been used to estimate facial growth status. In this study, we examined whether cone-beam computed tomography images can be used to detect changes of CVM-related parameters and bone mineral density distribution in adolescents during orthodontic treatment. METHODS Eighty-two cone-beam computed tomography images were obtained from 41 patients before (14.47 ± 1.42 years) and after (16.15 ± 1.38 years) orthodontic treatment. Two cervical vertebral bodies (C2 and C3) were digitally isolated from each image, and their volumes, means, and standard deviations of gray-level histograms were measured. The CVM stages and mandibular lengths were also estimated after converting the cone-beam computed tomography images. RESULTS Significant changes for the examined variables were detected during the observation period (P ≤0.018) except for C3 vertebral body volume (P = 0.210). The changes of CVM stage had significant positive correlations with those of vertebral body volume (P ≤0.021). The change of the standard deviation of bone mineral density (variability) showed significant correlations with those of vertebral body volume and mandibular length for C2 (P ≤0.029). CONCLUSIONS The means and variability of the gray levels account for bone mineral density and active remodeling, respectively. Our results indicate that bone mineral density distribution and the volume of the cervical vertebral body changed because of active bone remodeling during maturation.