Tuned Aperture Computed Tomography Images Research Articles

Correlation of tuned aperture computed tomography with conventional computed tomography for evaluation of osseous healing in calvarial defects

To compare the diagnostic efficacy of iteratively restored tuned aperture computed tomography (TACT) with conventional computed tomography (CT) for evaluation of osseous healing in induced calvarial defects. Fifty-six calvarial defects in 14 rabbits received 1 of 4 possible treatments: copolymer membranes with and without bone marrow stromal cells (BMSCs), BMSCs alone, or no treatment (control). Healing was measured after 2, 4, and 8 wks as remaining defect areas measured on TACT and CT images. Histomorphometric analyses were done on the specimens. Bone formation was minimal to none in control defects and those treated with BMSCs or polymer matrices alone. Healthy bone formation was noted in defects treated with polymers impregnated with BMSCs. Unresolved defect area measurements using TACT and CT of osseous healing showed a high positive correlation. Potential for TACT to accurately detect osseous healing in surgical defects was demonstrated. High resolution of TACT combined with generation of information in 3D yields comparable performance to CT.

Diagnostic ability of extraoral tuned aperture computed tomography (TACT) for impacted third molars

The purpose of this study was to evaluate the capabilities of a newly developed extraoral TACT system for diagnosing impacted third molars. Three dry human mandibles with impacted third molars were used. Nine base images were obtained by the extraoral and intraoral TACT methods. Four board-certified oral and maxillofacial radiologists evaluated TACT slice images as to whether the TACT images could clearly show the periodontal space of the impacted third molar, and the location of the tooth relative to the second molar, or to the mandibular canal. The criteria were excellent, good, fair, poor, and unreadable. Only the visibility of the periodontal space in extraoral TACT was significantly inferior to that of intraoral TACT. Almost all of the series of TACT images, however, were graded as excellent or good. The results indicate that extraoral TACT is a useful modality for the clinical assessment of impacted third molars.

Array geometry for assessment of mandibular implant position using tuned aperture computed tomography (TACT).

To evaluate observer faciolingual depth and vertical depth reading errors when using various X-ray beam array geometries to make basis images for tomosynthetic reconstruction using tuned aperture computed tomography (TACT). Tissue-equivalent models were constructed to replicate the position of dental implants in relation to simulated mandibular canals. X-ray beam geometries used to acquire the basis images for TACT(TM) integration included horizontal linear, vertical linear, and symmetric and asymmetric conical arrays. Twenty-one dentists trained in the use of TACT acted independently as observers. Tasks included: (1) determination of the relative position of the implant in relation to the simulated canal; and (2) measurement of the vertical depth and faciolingual (lateral) depth dimensions between these two structures. As the study did not involve repeated measures (only one measure was obtained from each observer on each of the two dependent variables), data for faciolingual depth and vertical depth reading errors were analysed using a one-way analysis of variance (ANOVA) with Tukey's honestly significant different (HSD) procedure. Errors in determining the relative position of the implant to the simulated canal were most frequent when the linear horizontal projection geometry was employed for producing basis images (57% error for model #2 where the implant was lingually placed). The mean measurement errors for TACT images constructed using the various different projection arrays depended both on the structural relationship of anatomic features and the employed beam array geometry. Conical beam arrays are preferred over linear beam arrays for constructing basis images used with TACT for the purpose of correlating the position of a mandibular dental implant in relation to the mandibular canal. They more consistently allowed the observers to establish a measurement of the faciolingual relationship of the implant to the canal. For vertical depth measurement of the relationship of a mandibular dental implant to the mandibular canal, TACT does not appear to have any advantage over individual simple transmission radiographic images.

Effect of iterative restoration on the detection of artificially induced vertical radicular fractures by Tuned Aperture Computed Tomography.

The purpose of this study was to evaluate the effect of the number of iterative restorations (IR) on the diagnostic accuracy of Tuned Aperture Computed Tomography images (TACT) for detection of induced vertical/oblique root fractures in mandibular teeth. Fractures were induced in 28 single-rooted, endodontically treated cadaver mandibular teeth while another 26 such teeth served as controls. TACT slices reconstructed by using 9 arbitrary projections (angular disparity of 9 degrees -20 degrees) were iteratively restored 1, 2, and 3 times. Eight observers scored their diagnoses by using a confidence rating scale. Ground truth was available from direct examination with transillumination, following extraction. Mean areas under the representative ROC curves for the 3 operations were 0.96 (3 IRs), 0.87 (2 IRs), and 0.86 (1 IRs). Analysis of variance demonstrated significant differences between 3 and 1 to 2 IRs (P <.01), as well as between observers (P <.01). Diagnostic accuracy of TACT for vertical/oblique root fracture detection improved after 3 IRs.

Fractal analyses of osseous healing using tuned aperture computed tomography images.

The aim of this study was to evaluate osseous healing in mandibular defects using fractal analyses on conventional radiographs and tuned aperture computed tomography (TACT; OrthoTACT, Instrumentarium Imaging, Helsinki, Finland) images. Eighty test sites on the inferior margins of rabbit mandibles were subject to lesion induction and treated with one of the following: no treatment (controls); osteoblasts only; polymer matrix only; or osteoblast-polymer matrix (OPM) combination. Images were acquired using conventional radiography and TACT, including unprocessed TACT (TACT-U) and iteratively restored TACT (TACT-IR). Healing was followed up over time and images acquired at 3, 6, 9, and 12 weeks post-surgery. Fractal dimension (FD) was computed within regions of interest in the defects using the TACT workbench. Results were analyzed for effects produced by imaging modality, treatment modality, time after surgery and lesion location. Histomorphometric data were available to assess ground truth. Significant differences (p < 0.0001) were noted based on imaging modality with TACT-IR recording the highest mean fractal dimension (MFD), followed by TACT-U and conventional images, in that order. Sites treated with OPM recorded the highest MFDs among all treatment modalities (p < 0.0001). The highest MFD based on time was recorded at 3 weeks and differed significantly with 12 weeks (p < 0.035). Correlation of FD with results of histomorphometric data was high (r = 0.79; p < 0.001). The FD computed on TACT-IR showed the highest correlation with histomorphometric data, thus establishing the fact TACT is a more efficient and accurate imaging modality for quantification of osseous changes within healing bony defects.

Tuned-aperture computed tomography for detection of occlusal caries.

To evaluate the use of tuned-aperture computed tomography (TACT) for the detection of primary occlusal caries. The material comprised 76 extracted posterior teeth, 51 with caries. Radiographs were recorded both with the Sens-A-Ray (Regam Medical Systems Int. AB, Sundsvall, Sweden) digital radiographic system and with Kodak EktaSpeed Plus film (Eastman-Kodak Co., Rochester NY, USA) employing an Orthopantomograph OP 100 (Instrumentarium Imaging, Tuusula, Finland) and a Prostyle Intra (Planmeca, Helsinki, Finland) dental unit respectively. The Sens-A-Ray radiographs were used to construct TACT slices and TACT iterative slices. The teeth were subsequently sectioned in 300 microm thick slices. Microradiographs were exposed and analysed with respect to the true presence of lesions. Seven observers subjectively evaluated the radiographs and ROC analyses performed. Conventional radiographs were compared with TACT images by means of the area under the ROC curves, Az. Paired t-test was used to compare Az values. Interobserver agreement was evaluated using the Kendall coefficient and the Friedman Anova. TACT radiographs were significantly better than conventional radiographs for diagnosing all types of occlusal caries combined (P(TACT) (slices)=0.02. P(TACT) (iterative slices)=0.01). However, neither TACT system was significantly better than film for enamel and dentinal caries separately. Observer agreement was moderate. However, observers demonstrated significant systematic differences in their readings (P<0.001). TACT may be a feasible method for diagnosing primary occlusal caries.

Comparative evaluation of Tuned Aperture Computed Tomography for the detection of mandibular fractures.

To compare the diagnostic efficacy of Tuned Aperture Computed Tomography (TACT) with conventional imaging modalities for detection of fractures of the mandible. Fractures were induced using blunt trauma in human defleshed mandibles. Conventional extra-oral and indirect digital images, unprocessed TACT images reconstructed from eight and 16 basis images (BI) and iteratively restored TACT images from eight and 16 BI were used for fracture evaluation. Twelve observers recorded their diagnoses using a five-point confidence rating scale. The data were analysed using ROC curve analysis. Significant differences were found (P < 0.0001) in the areas under the curve (Az): film, 0.6954; digital images 0.6169; TACT unprocessed images using 8 BI, 0.7420; TACT unprocessed images using 8 BI, 0.7667; TACT unprocessed images using 16 BI, 0.7730; TACT iteratively restored images using 16 BI, 0.8143. No observer-based differences were found. Fractures in the condylar and coronoid regions were more difficult to detect than those in the ramus and body of the mandible. Iteratively restored TACT images generated using 16 BI had a superior diagnostic performance to all the other imaging modalities. Studies are in order to evaluate its in vivo potential.