Low-cost dual-energy CBCT by spectral filtration of a dual focal spot X-ray source.

Dual-energy cone beam computed tomography (DE-CBCT) has been shown to provide more information and improve performance compared to a conventional single energy spectrum CBCT. Here we report a low-cost DE-CBCT by spectral filtration of a carbon nanotube x-ray source array. The x-ray photons from two focal spots were filtered respectively by a low and a high energy filter. Projection images were collected by alternatively activating the two beams while the source array and detector rotated around the object, and were processed by a one-step materials decomposition and reconstruction method. The performance of the DE-CBCT scanner was evaluated by imaging a water-equivalent plastic phantom with inserts containing known densities of calcium or iodine and an anthropomorphic head phantom with dental implants. A mean energy separation of 15.5 keV was achieved at acceptable dose rates and imaging time. Accurate materials quantification was obtained by materials decomposition. Metal artifacts were reduced in the virtual monoenergetic images synthesized at high energies. The results demonstrated the feasibility of high quality DE-CBCT imaging by spectral filtration without using either an energy sensitive detector or rapid high voltage switching.

Three-Dimensional Assessment of Cervical Vertebrae Anomalies in Patients With Cleft Lip and Palate.

OBJECTIVE: To evaluate the occurrence of cervical vertebrae anomalies (CVA) in patients with unilateral (UCLP) and bilateral cleft lip and palate (BCLP) using cone beam computed tomography (CBCT) examinations. DESIGN: Retrospective assessment of CBCT images. Descriptive statistics were calculated. Fisher exact test or χ2 test was performed to evaluate the differences among each CVA between sex and type of cleft. SETTING: School of Dentistry. PARTICIPANTS: One hundred fifty-one patients with cleft lip and palate (103 UCLP/48 BCLP). INTERVENTIONS: No relevant intervention. MAIN OUTCOME MEASURES: Cone beam computed tomography images were assessed for the presence or absence of 12 most commonly observed CVA: spina bifida, dehiscence, cleft of the posterior arch, cleft of the anterior arch, fusion between cervical vertebrae, block fusion, occipitalization, narrowing of the intervertebral space, posterior ponticle, os odontoideum, ossiculum terminale, and subdental cartilaginous remnants. RESULTS: The presence of subdental cartilaginous remnants was the most frequently observed alteration-found in 81.45% of the sample-and it was the only CVA with statistically significant frequencies in the individuals with BCLP. Considering only the other CVA, 22.51% presented 1 and 5.29% presented 2 or more CVA. CONCLUSIONS: Patients with cleft lip and palate may present an overall high incidence of CVAs. However, when comparing the distribution of the CVAs among sex and types of cleft, the only significant difference noted was a higher incidence of subdental cartilaginous remnants among patients with BCLP.

Cone-beam CT diagnostic applications: caries, periodontal bone assessment, and endodontic applications.

Cone-beam CT (CBCT) is useful for many maxillofacial applications, such as implant site imaging and diagnosis and treatment planning for orthodontics and craniofacial surgery. Dentoalveolar applications, such as carious lesion detection and characterization, assessment of the three-dimensional nature of periodontal bone topography, and various endodontic applications are less known and not as thoroughly studied. This article explores and assesses in vivo and in vitro efforts to apply CBCT imaging to these more common dentoalveolar tasks. CBCT imaging, like its medical counterpart, can be seen as a highly useful and, in some instances, indispensable part of the dental imaging armamentarium.

In vitro assessment of cone beam local computed tomography for proximal caries detection.

OBJECTIVES: To compare the accuracy of local computed tomography (LCT) and conventional radiography for proximal caries detection and depth assessment. STUDY DESIGN: An in vitro model was used consisting of 20 extracted posterior teeth with 18 caries lesions. Local computed tomography slices were reconstructed in axial and parasagittal planes from 100 basis projections. Conventional radiographs were also acquired. Eight observers determined the presence and depth of caries lesions. Receiver operating characteristic analysis and weighted kappa statistics were used. RESULTS: Local computed tomography had a mean A(z) score of 0.82 (SD = 0.07) and conventional radiography of 0.79 (SD = 0.08; analysis of variance: P > .05). Interobserver agreement was moderate. The mean kappa for depth assessment was 0.68 (SD = 0.06) for LCT and 0.47 (SD = 0.08) for conventional radiography (analysis of variance: P < .05). Local computed tomography resulted in substantial and conventional radiography in moderate interobserver agreement. CONCLUSIONS: There is no difference between LCT and conventional radiography for proximal caries detection. Local computed tomography was more accurate for assessing caries lesion depth.

In vitro assessment of local computed tomography for the detection of longitudinal tooth fractures.

OBJECTIVE: To test the accuracy of local computed tomography (LCT) in detecting longitudinal fractures in comparison with conventional periapical radiographs. STUDY DESIGN: Longitudinal fractures were induced in 30 of 60 teeth. The teeth were placed in a dry dentate mandible with soft tissue simulation. A laboratory LCT unit was used to acquire 180 basis projections with 1 degree separation along a 180 degree arc. Conventional radiographs served as the control modality. Correlated axial, coronal, and sagittal views were presented to 10 observers. The observers determined the presence of a root fracture by using a 5-point receiver operating characteristic confidence scale. RESULTS: The mean A(z) for LCT was 0.91 (SD = 0.07). The mean A(z) for conventional radiography was 0.70 (SD = 0.07). The difference between the modalities was statistically significant (analysis of variance: P < .0002), whereas the differences between the observers was not (analysis of variance: P = .319). CONCLUSION: Local CT significantly improves the detection of longitudinal fractures in vitro compared with conventional periapical radiography.

Tuned aperture computed tomography (TACT) for cross-sectional implant site assessment in the posterior mandible.

PURPOSE: This study was designed to optimize a new radiographic modality known as tuned aperture computed tomography (TACT) for cross-sectional imaging of implant sites in human dry mandibles. MATERIALS AND METHODS: Five imaging modalities were compared for image quality and measurement accuracy: (1) conventional hypocycloidal tomograms, (2) TACT images reconstructed using the average method produced using a linear x-ray source movement, (3) TACT images reconstructed using the average method produced using a multidirectional x-ray source movement, (4) minimally reconstructed TACT images without a fiducial marker at the site of interest, and (5) minimally reconstructed TACT images with a fiducial marker at the site of interest. RESULTS: The extended Mantel-Haenszel mean score statistic was used to investigate the influence of modality on subjective image quality. A statistically significant difference for certain types of TACT images and multidirectional tomography (P < 0.0001) was observed. Linear TACT and multmin TACT were rated as significantly better than other image modalities (P < 0.0009), whereas multidirectional tomography was rated as being significantly worse than other radiographic modalities (P < 0.0001). For the quantitative assessment, data were normalized and analyzed statistically through a paired-comparisons t test. For each modality, the accuracy for maximum height and height was significantly different from ground truth (P < 0.05). CONCLUSION: The qualitative data suggest that visibility of structures important to the choice of implant location and dimension were seen better with certain TACT methods. Quantitative differences from ground truth (actual measurements of the bone-absolute truth) were clinically negligible. TACT appears to offer the potential of superior image quality over the status quo.