John B. Ludlow

Comparative dosimetry of dental CBCT devices and 64-slice CT for oral and maxillofacial radiology

OBJECTIVES This study compares 2 measures of effective dose, E(1990) and E(2007), for 8 dentoalveolar and maxillofacial cone-beam computerized tomography (CBCT) units and a 64-slice multidetector CT (MDCT) unit. STUDY DESIGN Average tissue-absorbed dose, equivalent dose, and effective dose were calculated using thermoluminescent dosimeter chips in a radiation analog dosimetry phantom. Effective doses were derived using 1990 and the superseding 2007 International Commission on Radiological Protection (ICRP) recommendations. RESULTS Large-field of view (FOV) CBCT E(2007) ranged from 68 to 1,073 microSv. Medium-FOV CBCT E(2007) ranged from 69 to 560 microSv, whereas a similar-FOV MDCT produced 860 microSv. The E(2007) calculations were 23% to 224% greater than E(1990). CONCLUSIONS The 2007 recommendations of the ICRP, which include salivary glands, extrathoracic region, and oral mucosa in the calculation of effective dose, result in an upward reassessment of fatal cancer risk from oral and maxillofacial radiographic examinations. Dental CBCT can be recommended as a dose-sparing technique in comparison with alternative medical CT scans for common oral and maxillofacial radiographic imaging tasks.

In Vivo Comparison of Conventional and Cone Beam CT Synthesized Cephalograms

OBJECTIVE To compare measurements from synthesized cone-beam computed tomography (CBCT) lateral cephalograms using orthogonal and perspective projections with those from conventional cephalometric radiographs. MATERIALS AND METHODS Thirty-one patients were imaged using CBCT and conventional cephalometry. CBCT volume data were imported in Dolphin 3D. Orthogonal and perspective lateral cephalometric radiographs were created from three-dimensional (3D) virtual models. Twelve linear and five angular measurements were made on synthesized and conventional cephalograms in a randomized fashion. Conventional image measurements were corrected for known magnification. Linear and angular measurements were compared between image modalities using repeated measures analysis of variance. Statistical significance was defined as an alpha level of .01. RESULTS With the exception of the Frankfort-mandibular plane angle (P < .0001), angular measurements were not statistically different for any modality (P > .01). Linear measurements, whether based on soft or hard tissue landmarks, were not statistically different (P > .01). CONCLUSIONS Measurements from in vivo CBCT synthesized cephalograms are similar to those based on conventional radiographic images. Thus, additional conventional imaging may generally be avoided when CBCT scans are acquired for orthodontic diagnosis.

Precision of cephalometric landmark identification: Cone-beam computed tomography vs conventional cephalometric views

INTRODUCTION In this study, we compared the precision of landmark identification using displays of multi-planar cone-beam computed tomographic (CBCT) volumes and conventional lateral cephalograms (Ceph). METHODS Twenty presurgical orthodontic patients were radiographed with conventional Ceph and CBCT techniques. Five observers plotted 24 landmarks using computer displays of multi-planer reconstruction (MPR) CBCT and Ceph views during separate sessions. Absolute differences between each observers plot and the mean of all observers were averaged as 1 measure of variability (ODM). The absolute difference of each observer from any other observer was averaged as a second measure of variability (DEO). ANOVA and paired t tests were used to analyze variability differences. RESULTS Radiographic modality and landmark were significant at P <0.0001 for DEO and ODM calculations. DEO calculations of observer variability were consistently greater than ODM. The overall correlation of 1920 paired ODM and DEO measurements was excellent at 0.972. All bilateral landmarks had increased precision when identified in the MPR views. Mediolateral variability was statistically greater than anteroposterior or caudal-cranial variability for 5 landmarks in the MPR views. CONCLUSIONS The MPR displays of CBCT volume images provide generally more precise identification of traditional cephalometric landmarks. More precise location of condylion, gonion, and orbitale overcomes the problem of superimposition of these bilateral landmarks seen in Ceph. Greater variability of certain landmarks in the mediolateral direction is probably related to inadequate definition of the landmarks in the third dimension.

Effective radiation dose of ProMax 3D cone-beam computerized tomography scanner with different dental protocols

OBJECTIVES The aim of this study was to compare effective doses resulting from different scan protocols for cone-beam computerized tomography (CBCT) using International Commission on Radiological Protection (ICRP) 1990 and 2007 calculations of dose. STUDY DESIGN Average tissue-absorbed dose, equivalent dose, and effective dose for a ProMax 3D CBCT with different dental protocols were calculated using thermoluminescent dosimeter chips in a human equivalent phantom. Effective doses were derived using ICRP 1990 and the superseding 2007 recommendations. RESULTS Effective doses (ICRP 2007) for default patient sizes from small to large ranged from 102 to 298 μSv. The coefficient of determination (R(2)) between tube current and effective dose (ICRP 2007) was 0.90. When scanning with lower resolution settings, the effective doses were reduced significantly (P < .05). CONCLUSIONS ProMax 3D can provide a wide range of radiation dose levels. Reduction in radiation dose can be achieved when using lower settings of exposure parameters.

Quantification of condylar resorption in temporomandibular joint osteoarthritis

OBJECTIVE This study was performed to determine the condylar morphologic variation of osteoarthritic (OA) and asymptomatic temporomandibular joints (TMJs) and to determine its correlation with pain intensity and duration. STUDY DESIGN Three-dimensional surface models of mandibular condyles were constructed from cone-beam computerized tomography images of 29 female patients with TMJ OA (Research Diagnostic Criteria for Temporomandibular Disorders group III) and 36 female asymptomatic subjects. Shape correspondence was used to localize and quantify the condylar morphology. Statistical analysis was performed with multivariate analysis of covariance analysis, using Hotelling T(2) metric based on covariance matrices, and Pearson correlation. RESULTS The OA condylar morphology was statistically significantly different from the asymptomatic condyles (P < .05). Three-dimensional morphologic variation of the OA condyles was significantly correlated with pain intensity and duration. CONCLUSION Three-dimensional quantification of condylar morphology revealed profound differences between OA and asymptomatic condyles, and the extent of the resorptive changes paralleled pain severity and duration.

A comparison of kodak ektaspeed plus film and the siemens sidexis digital imaging system for caries detection using receiver operating characteristic analysis

OBJECTIVE To evaluate the accuracy of proximal caries detection comparing enhanced and unenhanced Siemens Sidexis CCD-based digital images with Ektaspeed Plus films utilizing receiver operating characteristic analysis. STUDY DESIGN Sixty extracted teeth (24 posterior and 36 anterior) were imaged under identical standardized geometric and exposure conditions. Six observers, using a 5-point confidence scale, rated 120 proximal surfaces for the presence or absence of carious lesions by means of three image modalities: (1) observer enhanced and (2) unenhanced Sidexis displays, and (3) Ektaspeed Plus films. The ground truth was determined by microscopic analysis of ground sections. Receiver operating characteristic curves were generated with calculated areas (AZ) analyzed with analysis of variance for effect of reader, reading, and modality. RESULTS Analysis of variance demonstrated significant differences among readers, readings and modalities (mean square values of 0.012, 0.005, 0.004, F ratios of 13.604, 5.329, 5.100; p = values of 0.001, 0.043, and 0.030, respectively). Post-hoc paired comparisons of modalities using Tukeys statistic demonstrated that only film and enhanced Sidexis images were different from each other (p = 0.024). AZ scores were 0.7650, 0.7499, and 0.8008 respectively, for unenhanced Sidexis, enhanced Sidexis, and Ektaspeed Plus film. CONCLUSION Unenhanced digital Sidexis images were equivalent to film for the detection of proximal caries in this in vitro study. Observer enhanced Sidexis images exhibited a statistically significant lower diagnostic accuracy than the unenhanced digital and film images.

Correlating cone beam CT results with temporomandibular joint pain of osteoarthritic origin

OBJECTIVES The purpose of this study was to determine whether bony changes in temporomandibular joint (TMJ) osteoarthritis (OA) is correlated with pain and other clinical signs and symptoms. METHODS Clinical data and cone beam CT (CBCT) images of 30 patients with TMJ OA were analysed. The criteria of Koyama et al (Koyama J, Nishiyama H, Hayashi T. Follow-up study of condylar bony changes using helical computed tomography in patients with temporomandibular disorder. Dentomaxillofac Radiol 2007; 36: 472-477.) and Ahmad et al [Ahmad M, Hollender L, Anderson Q, Kartha K, Ohrbach R, Truelove EL, et al. Research diagnostic criteria for temporomandibular disorders (RDC/TMD): development of image analysis criteria and examiner reliability for image analysis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009; 107: 844-860.] were used to classify the condyles observed on the CBCT. Clinical measures included self-reported pain, mandibular range of motion, TMJ sound, pain on palpation of the TMJ and masticatory muscles, and pain on jaw function. Generalized linear modelling was used to correlate the clinical and radiographic findings and Spearmans rho was used to correlate the two classification systems. RESULTS There was poor correlation between the maximum condyle change and pain rating (Koyama: r² = 0.1443, p = 0.3995; Ahmad: r² = 0.0273, p = 0.9490), maximum mouth opening (Koyama: r² = 0.2910, p = 0.0629; Ahmad: r² = 0.2626, p = 0.0951), protrusion (Koyama: r² = 0.0875, p = 0.7001; Ahmad: r² = 0.1658, p = 0.3612), right lateral motion (Koyama: r² = 0.0394, p = 0.9093; Ahmad: r² = 0.0866, p = 0.6877) and left lateral motion (Koyama: r² = 0.0943, p = 0.6494; Ahmad: r² = 0.1704, p = 0.3236). Strong correlation was observed between Koyama et als and Ahmad et als classifications for average (r = 0.9216, p < 0.001) and maximum (r = 0.7694; p < 0.0001) bony change. CONCLUSIONS There was poor correlation between condylar changes (as observed on CBCT images), pain and other clinical signs and symptoms in TMJ OA.

Incidental findings from cone beam computed tomography of the maxillofacial region: a descriptive retrospective study

OBJECTIVE To evaluate the type and prevalence of incidental findings from cone beam computed tomography (CBCT) of the maxillofacial region. Findings are divided into those that require (i) intervention/referral, (ii) monitoring, and (iii) no further evaluation. METHODS Three hundred consecutive CBCT scans conducted in the University of North Carolina School of Dentistry Oral and Maxillofacial Radiology Clinic from January 1 to August 31, 2008 were retrospectively reviewed. Findings were categorized into airway, soft tissue calcifications, bone, temporomandibular joint (TMJ), endodontic, dental developmental, and pathological findings. RESULTS A total of 272 scans revealed 881 incidental findings (3.2 findings/scan). The most prevalent was airway findings (35%) followed by soft tissue calcifications (20%), bone (17.5%), TMJ (15.4%), endodontic (11.3%), dental developmental (0.7%), and pathological (0.1%). 16.1% required intervention/referral, 15.6% required monitoring, and the remainder (68.3%) required neither. CONCLUSION This study underscores the need to thoroughly examine all CBCT volumes for clinically significant findings within and beyond the region of interest.

Tuned Aperture Computed Tomography and Detection of Recurrent Caries

This study compared the diagnostic efficacy of four imaging modalities for the detection of artificially induced recurrent caries: intraoral film, direct digital bitewing images, tuned apertuce computed tomography (TACTTM) slices and iteratively restored TACTTM images using an in vitro model. Twenty-four posterior teeth were prepared for MOD inlay restorations. These were then restored with different restorative materials (amalgam, Herculite and Durafill). Lesions were simulated in half the number of surfaces studied. These lesions were created either at the intersection of the facial or lingual walls and the gingival floor or on the gingival floor midway between the facial and lingual walls in the proximal boxes of the MOD restorations. Analysis of observations from 8 observers using ROC curve reveal the superior diagnostic efficacy with TACTTM iteratively restored images (Az for TACTTM iteratively restored images = 0.9171, TACTTM slices = 0.7052, Film = 0.6608, direct digital images = 0.5979). ANOVA revealed significance with respect to the imaging modality used (p < 0.0001). The results suggest that TACTTM images hold promise as a more effective imaging modality than film or direct digital systems for detection of recurrent caries.

TACT Imaging of primary caries

OBJECTIVE Tuned-aperture computed tomography, a new method for creating 3-D radiographic information based on optical aperture theory, was evaluated for diagnostic efficacy in primary caries detection. STUDY DESIGN Sixty-four extracted teeth with 89 carious lesions were imaged with D-speed film, direct digital, and TACT modalities. A commercially available, 8-bit, charge-coupled device was used in the later two modalities. Six trained observers were asked to identify the presence or absence and depth of interproximal and occlusal lesions for all three modalities. The teeth were sectioned and examined microscopically to determine ground truth. Logistic regression analysis was performed for all three imaging systems for the detection task. Analysis of variance was used for depth determination. Detection of lesion, depth of lesion accuracy, and time for diagnosis were also examined. RESULTS For caries detection TACT and film were not different (p = 0.2216) with the Wald statistic. Film and TACT were significantly more accurate than the digital system (p = 0.0001). Scheffes post hoc test revealed that TACT and film were more accurate than the direct digital system for determining lesion depth (p = 0.05) but not statistically different when compared with each other. The detection data were substantiated further by receiver operating characteristic analysis that demonstrated similar statistical relationships. Time required per diagnosis was not shown to be statistically different among the three imaging modalities. CONCLUSIONS We conclude for caries detection and depth determination that TACT could not be distinguished from film despite the significant relative loss of information capacity in the charge-coupled device receptor. The relatively poorer performance yielded by the digital control images suggests that increased information capacity associated with more modern charge-coupled device detectors may improve diagnostic performance for both direct digital and TACT displays over that demonstrated in this investigation.