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.     

Tuned aperture computed tomography to evaluate osseous healing

Quantification of osseous healing is a challenging task, requiring expensive advanced imaging modalities. To improve diagnostic osseous imaging, we undertook this prospective study to explore the potential of Tuned Aperture Computed Tomography. Eighty defects in 20 rabbit mandibles, randomly carrying an osteoblast suspension or a polymer matrix or a combination thereof or no treatment, were imaged at 3, 6, 9, and 12 weeks post-surgery. TACT slices, iteratively restored TACT, and conventional digital radiographs were evaluated. Mean-gray-value distribution within regions of interest was correlated with histomorphometric data. Lesions treated with osteoblast/polymer-matrix delivery systems demonstrated the highest mean gray-value, while the diagnostic efficacy of TACT-IR was significantly better than that of other imaging modalities (p < 0.001). Thus, TACT is an accurate imaging modality for non-destructive quantification of osseous dynamics.     

Diagnostic accuracy of Tuned Aperture Computed Tomography (TACT)

The diagnostic accuracy of Tuned Aperture Computed Tomography (TACT) was evaluated for a variety of diagnostic tasks. Drawbacks of 2D radiography, lack of accessibility and high cost associated with advanced imaging modalities prompted these studies. Mechanically induced vertical/oblique radicular fractures (VRF) on unrestored and endodontically treated teeth were imaged using 2D radiography, unprocessed and TACT-IR images. The effect of iterative restoration on diagnostic accuracy was studied in association with detection tasks such as VRF and mandibular fractures, as also with quantification efforts associated with osseous healing studied in vivo. Iterative restoration deblurring of TACT produced consistently higher diagnostic quality than the other two image types. The effect of observer training and previous experience with viewing TACT indicated that observers with prior experience performed better. It was also noted that fractures extending beyond the middle third of the roots were more accurately detected. The effect of the number of basis images on diagnostic accuracy of TACT radiographs for mandibular fractures showed that reconstructions using 16 basis images that had been iteratively restored performed significantly better. In the in vivo study, quantitative evaluation of healing of osseous defects subjected to different types of grafts using TACT indicates that the most optimal healing occurred with osteoblast-polymer matrix combination. TACT-IR correlated most with histomorphometric data. Increases in gray values corresponding to bone formation were notable during the early period following surgery. These studies indicate that there is enough justification for TACT to find applications in many clinical situations where an ordinary dental x-ray source and a digital sensor/film are currently being used.     

Detection of artificially induced vertical radicular fractures using Tuned Aperture Computed Tomography

This study compared the accuracy of three imaging modalities for the detection of artificially induced vertical root fractures (VRF) on teeth in cadaver mandibles. Fifty-four single-rooted, endodontically treated mandibular teeth being prepared to carry posts were evaluated using direct digital radiography (DDI) with a Schick sensor, unprocessed Tuned Aperture Computed Tomography (TACT-U) images and iteratively restored TACT (TACT-IR) images. Twenty-eight of these teeth had been subjected to fracture induction using an apically driven force. Nine basis images were used for each TACT image generation. Eight observers used a five-point confidence rating scale to record the confidence with which they considered a fracture to be present or not. Sensitivity and specificity values were computed and receiver operating characteristic (ROC) curves were generated. The areas under the curves (Az) used as an indication of the diagnostic accuracy of the imaging system were as follows: DDI: 0.37; TACT-U: 0.77 and TACT-IR: 0.81. DDI was significantly inferior to the TACT modalities. Differences in detection efficacy based on observers and observation sessions were noted on ANOVA and post-hoc Tukey's tests. This study indicates that TACT is the imaging modality of choice for VRF in endodontically treated teeth.     

Diagnostic value of tuned-aperture computed tomography versus conventional dentoalveolar imaging in assessment of impacted teeth

OBJECTIVE: This clinical study compares the diagnostic value of interactive 3-dimensional tuned-aperture computed tomography (TACT) with conventional dentoalveolar radiographic examinations of impacted maxillary incisors. STUDY DESIGN: TACT was compared variously with conventional intraoral, occlusal, rotational panoramic, and lateral cephalographic examinations. Sixteen dentists independently evaluated the clarity of anatomic structures of impacted anterior maxillary teeth and surrounding tissues. Estimation of confidence in clinical assessment of the patient was made together with a determination of the diagnostic potential of the studied modalities for altering treatment plans. RESULTS: TACT was found to significantly improve depiction of the buccal/palatal position of the impacted tooth and its relationship with adjacent teeth (P < .0001) irrespective of the availability of lateral cephalograms. Subjective assessments for clinical decision making approximated a 10% increase in confidence ratings with TACT. The added diagnostic value with TACT varied from case to case. CONCLUSIONS: The interactive 3-dimensional TACT display was perceived to be more informative for assessing impacted teeth and their relation to surrounding tissues than conventional methods in some cases but not in others. TACT altered treatment-option selection in some instances.     

An in vivo comparison of diagnostic information obtained from tuned-aperture computed tomography and conventional dental radiographic imaging modalities.

OBJECTIVE: The purpose of this study was to compare diagnostic information obtained by means of 3-dimensional tuned-aperture computed tomography (TACT) and by means of conventional radiography of patients requiring surgery. STUDY DESIGN: TACT produced digital images that yielded a series of tomographic slices viewed interactively. Controls were conventional periapical and/or panoramic radiographs. Each of 4 independent dentists performed 2 tasks, one requiring an estimation of confidence in their clinical assessments of the patient and the other requiring an estimation of the resulting diagnostic potential for altering associated treatment options. Data were analyzed through use of the nonparametric Mann-Whitney U Wilcoxon rank sum W test. RESULTS: A statistically significant difference for both tasks was observed (2-sided; P<.001). CONCLUSIONS: TACT displays were more diagnostically informative and had more impact on potential treatment options than did conventional radiographs.     

Assessment of three-dimensional X-ray images: reconstruction from conventional tomograms, compact computerized tomography images, and multislice helical computerized tomography images

Three-dimensional X-ray images (3D images) were used for imaging diagnosis in the oral and maxillofacial region. These images could be fundamentally reconstructed from various tomograms, though clinical 3D images were mainly reconstructed from computerized tomography (CT) images. In this investigation, 3D images were reconstructed from conventional tomograms with a panoramic unit, compact CT images, and multislice helical CT images, and the usefulness of each system was subjectively assessed for dental implant treatment. Three hemilateral dried human mandibles were used and were examined by linear tomography with a panoramic unit, compact CT, and multislice helical CT, and 3D images were reconstructed by using the rendering software for each system. The 3D images were visually evaluated on a 5-point scale covering the alveolar ridge, buccal and lingual bone surface, mental foramen, and tooth sockets. As a result, 3D images reconstructed from conventional tomograms with the panoramic unit were assessed as fair to unsure, compact CT 3D images were assessed as unsure to good, and multislice helical CT 3D images were assessed as good to excellent. It was concluded that compact CT 3D images and multislice helical CT 3D images were useful in dental implant treatment.     

The role of objective plane angulation on the mandibular image using cross-sectional tomography

Cross-sectional jaw images in the buccolingual direction obtained by conventional or computerized tomography are used in the image diagnosis of dental implant treatment. This study was performed to clarify the subjective image quality of the mandibular depiction by shifting the angles of the tomographic objective plane. A panoramic machine with a linear tomographic function was used to obtain cross-sectional tomographic images on bilateral first molar regions of 10 dried human mandibles. The angles of tomographic objective planes were shifted horizontally within a range of +/- 20 degrees at intervals of 5 degrees from the tomographic objective plane, which was automatically determined. The image qualities of 4 anatomical structures-alveolar crest, buccal and lingual cortical bone, and mandibular canal-were subjectively scored on a 5-point scale method. As a result, the permitted tomographic objective angles were from -1.7 degrees to 2.5 degrees, a range of 4.2 degrees for all 4 anatomical structures. When this result was compared with a previous geometric result, the permitted range of the angles was quite narrow. The tomographic objective angles should be manually set in accordance with an optimal tomographic plane for individual patients by using the positioning technique in linear tomography.     

Selection criteria for dental implant site imaging: a position paper of the American Academy of Oral and Maxillofacial radiology

The American Academy of Oral and Maxillofacial Radiology (AAOMR) has reviewed the implant imaging literature and issues this position paper for preoperative assessment of the dental implant site. The history of dental implant radiology and basic imaging principles are reviewed. An overview is presented of anatomically salient features in the maxilla and mandible germane to implant imaging, specifically to cross-sectional or transverse imaging for endosseous implants. All current modalities, including intraoral, panoramic, cephalometric, tomographic, and computed tomography, are discussed in light of the imaging data needed to select optimum implant solutions. After reviewing the current literature, the AAOMR recommends that some form of cross-sectional imaging be used for implant cases and that conventional cross-sectional tomography be the method of choice for gaining this information for most patients receiving implants.     

Evaluation of tuned-aperture computed tomography in the detection of simulated periodontal defects

OBJECTIVE: The objective of this study was to compare the diagnostic efficacy of tuned-aperture computed tomography (TACT) and conventional film for the detection of simulated periodontal defects. STUDY DESIGN: Periodontal defects were created in 15 premolar-molar interproximal sites selected from 8 cadaver jaw segments. Ten observers viewed 45 image pairs (baseline and follow up) in 4 TACT modalities and film to assess the presence of defect. The TACT modalities were 1st and 2nd generation prototype systems (TACT-1 and TACT-2) with circular (C) and random (R) distribution patterns of source projection (TACT-1C, TACT-1R, TACT-2C, TACT-2R). Observer performance and related factors were analyzed by using receiver operating characteristic and analysis of variance. RESULTS: Mean A(z) values were 0.64 for film, 0.74 for TACT-1C, 0.82 for TACT-1R, 0.64 for TACT-2C, and 0.69 for TACT-2R. TACT-1R was significantly better than film (P < .001), TACT-2C (P < .001) and TACT-2R (P = .007). CONCLUSION: TACT-1R provided the best diagnostic performance in the detection of simulated periodontal defects among the 5 modalities compared in this study.     

Diagnosis of external root resorption using TACT (tuned-aperture computed tomography)

Abstract – This study compared the ability of the TACT system of imaging and conventional D‐speed film to detect simulated resorptive defects in cadaver teeth and jaws. Mandibular human jaw blocks were prepared and then split through the teeth in a mesial to distal direction so that the mandibular halves could be opened and reassembled when necessary. One half of each of 42 teeth was extracted, and areas on the tooth and corresponding bone identified to be studied. The jaws were opened and reassembled after no defects or after defects of different sizes (0.25, 0.5, 1.0, 2.0 mm) were placed in the tooth and the corresponding bone at predetermined evaluation areas. The teeth were imaged after each stage with conventional D‐speed film using a standard paralleling technique, and with a modified orthopantomograph OP100 machine using a Schick #2 size CCD sensor as the image receptor. The source images were registered and TACT slices were generated using TACT Workbench Software. Three observers were asked to identify the presence of resorptive defects in the conventional film group and the TACT image group using specific criteria. TACT imaging was statistically superior to conventional radiographs in detecting defects that were present (Wilcoxon matched pairs signed ranks test P=0.003). This was true for all sizes of defects examined. There was no difference between the two modalities when a defect was not present.     

Diagnosis of external root resorption using TACT (tuned-aperture computed tomography)

This study compared the ability of the TACT system of imaging and conventional D-speed film to detect simulated resorptive defects in cadaver teeth and jaws. Mandibular human jaw blocks were prepared and then split through the teeth in a mesial to distal direction so that the mandibular halves could be opened and reassembled when necessary. One half of each of 42 teeth was extracted, and areas on the tooth and corresponding bone identified to be studied. The jaws were opened and reassembled after no defects or after defects of different sizes (0.25, 0.5, 1.0, 2.0 mm) were placed in the tooth and the corresponding bone at predetermined evaluation areas. The teeth were imaged after each stage with conventional D-speed film using a standard paralleling technique, and with a modified orthopantomograph OP100 machine using a Schick #2 size CCD sensor as the image receptor. The source images were registered and TACT slices were generated using TACT Workbench Software. Three observers were asked to identify the presence of resorptive defects in the conventional film group and the TACT image group using specific criteria. TACT imaging was statistically superior to conventional radiographs in detecting defects that were present (Wilcoxon matched pairs signed ranks test P = 0.003). This was true for all sizes of defects examined. There was no difference between the two modalities when a defect was not present.     

Cross-sectional imaging of the jaws for dental implant treatment: accuracy of linear tomography using a panoramic machine in comparison with reformatted computed tomography

PURPOSE: Although various panoramic X-ray machines with linear tomographic functions are now frequently applied to diagnosis related to dental implant treatment, the angles of the tomographic objective planes are automatically determined and cannot be adjusted for individual patients. To resolve this problem, a direct laser positioning (DLP) system was developed. In this investigation, the measurement accuracy of images obtained by the DLP system in comparison with those from reformatted computed tomography (CT) was assessed. MATERIALS AND METHODS: A rectangular parallel piped phantom was scanned with the system and the height and width were measured on linear tomograms. Ten sites in 3 dried mandibles and 21 mandibular molar sites in 15 patients were examined both with the DLP system and the reformatted CT to compare the measured values on both images. RESULTS: The phantom experiment showed that the difference between the actual and measured heights and widths of the phantom were within 1 mm. DISCUSSION: The difference between the values obtained by the DLP system and CT was slightly larger in the patients than those in the dried mandibles. CONCLUSION: The DLP measurement accuracy was deemed sufficient for clinical use.     

Detection of caries with conventional digital imaging and tuned aperture computed tomography using CRT monitor and laptop displays.

OBJECTIVE: The purpose of this study was to compare the diagnostic performance of conventional digital images and tuned aperture computed tomography (TACT) slices in caries detection through use of cathode-ray tube monitor and laptop displays. STUDY DESIGN: Forty-two extracted posterior teeth were mounted and imaged with a direct digital radiography system. Conventional digital bitewing projections and TACT slices were acquired. Images were viewed on a high-resolution cathode-ray tube monitor and on an active-matrix laptop display. Eight observers assessed caries status of occlusal and proximal surfaces of the teeth using all combinations of image and display modality. Observers' assessments were compared with the results of histologic examination of tooth sections. Possible differences in receiver operating characteristic curve areas among displays, image modalities, observers, and surfaces were analyzed by means of analysis of variance. RESULTS: There was no statistically significant difference between the diagnostic performances provided by the cathode-ray tube monitor and laptop displays in caries detection (P = .588). In addition, the performances of digital images and TACT slices were not significantly different (P = .843). CONCLUSIONS: Modern active-matrix laptop displays provide diagnostic quality for caries detection comparable to that obtainable with cathode-ray tube monitors.     

Accuracy of cone beam computed tomography and panoramic and periapical radiography for detection of apical periodontitis

The aim of this study was to evaluate the accuracy of imaging methods for detection of apical periodontitis (AP). Imaging records from a consecutive sample of 888 imaging exams of patients with endodontic infection (1508 teeth), including cone beam computed tomography (CBCT) and panoramic and periapical radiographs, were selected. Sensitivity, specificity, predictive values, and accuracy of periapical and panoramic radiographs were calculated. Receiver operating characteristic (ROC) analysis was performed to assess the diagnostic accuracy of the panoramic and periapical images. Prevalence of AP was significantly higher with CBCT. Overall sensitivity was 0.55 and 0.28 for periapical and panoramic radiographs, respectively. ROC curves and area under curve (AUC) with periapical radiography showed a high accuracy for the cutoff value of 5 for both periapical (AUC, 0.90) and panoramic (AUC, 0.84) radiographs. AP was correctly identified with conventional methods when showed advanced status. CBCT was proved to be accurate to identify AP.     

The use of 3 different imaging methods for the localization of the mandibular canal in dental implant planning

PURPOSE: The purpose of this study was to investigate the efficiency of panoramic radiography, conventional (cross-sectional) tomography, and computerized tomography for location of the mandibular canal before implant placement in the posterior region of the mandible. MATERIALS AND METHODS: Edentulous mandibles from 6 dry adult human skulls were used in this study. Four measurements (D1, D2, D3, D4) were made of 12 areas, one on each side of each mandible. Panoramic radiographs, conventional tomograms, and computerized tomograms were obtained. On each image, measurements were made for localization of the mandibular canal by one researcher. All measurements were repeated 3 times within a period of 3 weeks. Upon completion of imaging, the mandibles were surgically sectioned to provide direct measurements. The measurements obtained from the images were compared with direct measurements. Pearson correlation coefficients were calculated to detect statistical correlations between repeated measurements. The Dunnett t test was performed for statistical comparison of measurements from images and direct measurements. RESULTS: Pearson correlation coefficients showed strong linear correlation for all measurements (P < .01). No statistically significant difference was observed between direct measurement and D1, D2, or D4 (P < .05), but a statistically significant difference for D3 (buccolingual width 5 mm under mandibular crest; Dunnett t test; P > .05) between measurements was obtained from the images and direct measurements. CONCLUSION: The measurements obtained from computerized tomographic images were more consistent with direct measurements than the measurements obtained from panoramic radiographic images or conventional tomographic images.     

A comparison of jaw dimensional and quality assessments of bone characteristics with cone-beam CT, spiral tomography, and multi-slice spiral CT

PURPOSE: For proper preoperative planning of oral implants, the need has increased for tomographic imaging for precise determination of anatomic dimensions. However, concern for radiation exposure, which is substantial with computerized tomography (CT), has also grown. In the present study, the validity of jawbone width assessment and delineation by means of cone-beam CT (CBCT) and spiral tomography on dry mandibles was compared. Secondly, the subjective image quality of CBCT images with those obtained by multi-slice spiral CT (MSCT) of a fixed ex vivo cadaver with its soft tissues was compared. MATERIALS AND METHODS: The study included 25 dry human mandibles for the dimensional study and 1 formalized maxilla for image quality assessment. Measurements of the mandibles by means of a digital sliding caliper acted as the gold standard. Radiographic examination of the premolar and canine regions was performed with both CBCT and spiral tomography. Observational measurements were carried out by postgraduates in oral imaging. Subjective image quality was assessed on the fixed maxilla, including soft tissues, by comparing CBCT and MSCT. Inter- and intraobserver variability were determined. RESULTS: Direct mandibular measurements were on average 0.23 mm (SD 0.49) and 0.34 mm (SD 0.90) larger than the CBCT and spiral tomography measurements, respectively. Subjective image quality of the CBCT was significantly better than for the MSCT with regard to visualization and delineation of the lamina dura and periodontal ligament space. Subjective image quality of the MSCT was significantly better for the MSCT than the CBCT for the gingiva and cortical bone. CONCLUSIONS: These results indicate that on dry mandibles, jawbone width measurements by means of CBCT and spiral tomography are reliable, even if on average they slightly underestimate the bone width. For the subjective image quality, the CBCT offered better visualization of details of the small bony structures. Spiral tomography offered better visualization of the cortical bone and the gingiva.     

Geometric accuracy of digital volume tomography and conventional computed tomography

Digital volume tomography is a recently established imaging method that is based on the principle of cone beam computed tomography (CBCT). One of its main applications is imaging in dental and maxillofacial surgery. The objective of this study was to compare the geometric accuracy of digital volume tomographic imaging with that of conventional CT and to assess the suitability for image-guided operating.A calibration cube with a defined pattern of tubes inside was scanned using CT and digital volume tomography. Spatial accuracy was analysed with a software evaluation tool. The positions of the intersections of the tubes were detected in imaging data and registered to the real positions in the calibration body. The deviation was calculated and compared for CT and digital volume tomography.Resolution of spatial images was similar for both methods. However, the spatial accuracy in digital volume tomography was slightly lower than that of CT but still in the submillimetric range. The accuracy was better in the middle, but lower in the margins of the volume. This is a disadvantage in technical image quality, but does not affect the diagnostic image quality. The geometric accuracy is sufficient for digital volume tomography-based image-guided surgery.     

Generation of TACT image slices using different reconstruction algorithms: effects on natural caries detection.

OBJECTIVE: The purpose of this study was to determine whether the method of reconstruction of tuned-aperture computed tomography (TACT) slices has an influence on observer performance in caries detection. STUDY DESIGN: Eight images of each of 40 extracted posterior teeth were acquired by using a solid state intraoral detector. Stacks of tuned-aperture computed tomography slices were generated by using the minimum and average reconstruction methods. Slices of the 2 experimental conditions were presented to 8 observers in a balanced order. Images were viewed on a high-resolution 21-in color monitor. Observers scored the presence/absence of caries by using a 5-point confidence scale. Observers' assessments were compared with histologic examinations of tooth sections. Receiver operating characteristic curves measured observers' diagnostic performance. Analysis of variance was used to test for possible significant differences between observers and between experimental conditions. Sensitivity, specificity, accuracy, and interobserver reliability were also calculated. RESULTS: No statistically significant differences between the 2 methods of reconstruction were found for the detection of either occlusal (P =.07) or proximal (P =.52) caries. Interobserver reliability was similar for both experimental conditions. CONCLUSIONS: The minimum and average methods of TACT reconstruction provide comparable performances for caries detection tasks.     

Diagnostic accuracy of panoramic radiography,stereo-scanography and cone beam CT for assessment of mandibular third molars before surgery

Abstract

Objective. To compare the diagnostic accuracy of panoramic imaging, stereo-scanography and cone beam computed tomography (CBCT) for assessment of mandibular third molars. Material and methods. One hundred and twelve patients (147 third molars) underwent radiographic examination by panoramic imaging, stereo-scanography and CBCT. Tooth angulation, root morphology, number of roots and relation to the mandibular canal were assessed. The same variables were assessed intra- and post-operatively and served as reference for the radiographic assessments. The diagnostic accuracy for each variable was compared between the three modalities and accuracy was further expressed as sensitivity and specificity and tested between the modalities for identifying the relation to the mandibular canal. Results. There were no significant differences between the modalities regarding tooth angulation, root morphology and number of roots. However, CBCT was more accurate than stereo-scanography for determining root bending in the bucco-lingual plane (p = 0.02). Moreover, sensitivity for direct contact to the mandibular canal (panoramic imaging: 0.29, stereo-scanography: 0.57, CBCT: 0.67) was higher for CBCT than for panoramic images (p = 0.05) and specificity for no direct contact to the mandibular canal (panoramic imaging: 0.78, stereo-scanography: 0.53, CBCT: 0.68) was higher for panoramic images and CBCT than for scanograms (p < 0.001). Conclusion. Panoramic imaging, stereo-scanography and CBCT seem equally valuable for examination of tooth angulation, number and morphology of roots of mandibular third molars. However, CBCT was more accurate for assessment of root bending in the bucco-lingual plane and more accurate than panoramic images to identify direct contact to the mandibular canal.