Tuned Aperture Computed Tomography Research Articles

STATIONARY INTRAORAL DIGITAL TOMOSYNTHESIS USING CARBON NANOTUBES FIELD EMISSION X-RAY TECHNOLOGY: CLINICAL PROTOTYPE

<h3>Background</h3> Tuned aperture computed tomography (TACT) and intraoral tomosynthesis were studied in the past and demonstrated improved detection of various dental diseases. However, interest in TACT waned because the technology was not viable for clinical use. Recently, interest resurged with the advent of the carbon nanotube field emission x-ray source array technology. Researchers from the University of North Carolina (UNC) Department of Physics and Astronomy and the UNC School of Dentistry designed, patented, and conducted several benchtop studies to demonstrate its utility.¹ <h3>Objective</h3> The aim of this study was to develop a viable stationary intraoral tomosynthesis imaging device for clinical use. <h3>Materials and Methods</h3> XinVivo, an imaging device startup company, developed a prototype system designed for intraoral imaging applications.² <h3>Results</h3> The prototype met all the requirements for clinical use and met the U.S. Food and Drug Administration (FDA) requirements for intraoral imaging devices. <h3>Discussion</h3> The clinical prototype met all manufacturer specifications. Preliminary studies indicated that stationary intraoral tomosynthesis (s-IOT) provides increased image quality and feature conspicuity at a dose comparable with that in a single 2-dimensional (2-D) intraoral radiography.³

Three dimensional (3D) imaging techniques in orthodontics-An update.

3D imaging is a technique which develops or creates the impression of depth within an image by deploying 2D data into 3-dimensional format. To aid in quality regulating processes for industrial purposes, 3D imaging has become an extremely valuable factor. Owing to their various drawbacks, a wide range of investigative methods formulated for demonstration of facial structures and the dentition were dilapidated. Currently in medicine, the most prevalent method is perhaps 3D imaging technique renders thorough and problem specific information regarding hard and the soft tissues, such as Computerized Tomography (CT), Cone Beam Computerized Tomography (CBCT), Micro Computerized Tomography (MCT), 3D laser scanning, structured light technique, stereophotogrammetry or 3D surface imaging systems (3dMD), 3D facial morphometry (3DFM), Tuned Aperture Computed Tomography (TACT), and Magnetic Resonance Imaging (MRI). 3D imaging techniques in orthodontics plays an important role by facilitating more elaborated diagnostic information on the precise cases like patients having craniofacial anomalies. Hence, the aim of this study was to review advances in 3D imaging with in the field of orthodontics.

High-Resolution in situ Imaging of Cochlear Implant Electrode Arrays in Cat Temporal Bones Using Tuned Aperture Computed Tomography (TACT®)

To determine the suitability of Tuned Aperture Computed Tomography (TACT) to generate high-resolution images of intracochlear electrode arrays, in situ, with sufficient anatomic and electrode detail to relate the location of individual electrode contacts to important anatomic landmarks in cat cadaveric temporal bones. The ultimate objective is to develop an imaging technology whereby variations in electrode location, relative to the target neural tissues, can be accurately determined and related to variations in performance with the cochlear implant. Cat temporal bones were implanted with an experimental scala tympani electrode array and an external fiducial landmark. A series of conventional 2D digital radiographs were collected from a variety of x-ray source projection angles and served as for generation of 3D volume renderings using the TACT software toolbox. The 3D renderings were then reoriented and resliced interactively to view the cochlear and electrode features of interest. Significant electrode and anatomical details could be visualized including the course of the electrode wires (<40 microm diameter), the location of all electrode contacts and the outline of the scala tympani. TACT generates high-resolution 3D images from 2D conventional radiographs. With TACT, the 3D renderings can be interactively reoriented and resectioned to permit visualization of any cochlear or electrode feature. In the present study, this aspect of TACT affords the opportunity to view of the location of each electrode contact relative to the adjacent cochlear features, such as the scalar walls. Because TACT uses conventional radiographic images to generate the volume renderings, the quality and resolution of the resulting 2D images do not suffer from artifacts characteristic of CT. These findings suggest that TACT may be a powerful tool for understanding the contribution of electrode placement to perceptual performance with the cochlear implant.

Optimization of TACT Imaging Protocols for in situ Visualization of Cochlear Electrode Arrays in Cat Temporal Bones

To explore the effect of the number of two-dimensional (2D) images and x-ray projection angles on the resolution of reconstructed three-dimensional (3D) volumes of intracochlear electrode arrays in cadaveric cat temporal bones using Tuned Aperture Computed Tomography (TACT). Multiple 2D radiographs (basis images (BI)) of implanted cadaveric cat temporal bones were acquired using a range of projection angles, and imported into the TACT workbench. 3D volumes were reconstructed using varying numbers of BIs. Contrast resolution in the image was determined by comparing the contrast ratio (using maximum and minimum grayscale values) in specified anatomic areas of interest. Systematically increasing the number of BIs used in the reconstruction process resulted in a systematic increase in contrast resolution. Likewise, increasing the range of effective projection angles, as also the number of such angles used in the TACT computation also increased the contrast resolution of the resulting images. Precise determination of the location of cochlear implant electrodes in situ is critical to understanding the factors influencing efficacy of electrical stimulation of the deaf ear. Renderings generated with the TACT algorithm produce 3D images permitting visualization of implant electrode features and anatomic details with resolution sufficient to accurately localize electrode contacts within scala tympani. The quality of resulting images, evaluated as a function of image contrast, improved with a larger number of BIs in the reconstruction. Wider projection angles also improved image detail in addition to generating thinner slices. Any loss in contrast was compensated for by the number of BIs. TACT can thus be optimized to provide useful data to help characterize the location of intracochlear electrode arrays.

Tuned‐Aperture Computed Tomography for Detection of Induced Mid‐Buccal/Lingual Alveolar Bone Defects

The detection of bone loss in mid-buccal and lingual crests is impossible using conventional radiographs because of the superimposition of overlying anatomy and lack of three-dimensional information. The purpose of this study was to compare the diagnostic efficacy of tuned-aperture computed tomography (TACT) and conventional two-dimensional direct digital radiography (DDR) in an in vitro environment. A total of 45 mandibular molars had 0.8-mm lesions on mid-buccal/lingual crestal areas. Half of the sites received defects, whereas the other half served as controls. Nine DDR images were used to generate TACT slices that were further subjected to iterative restoration (TACT-IR). Eight observers used a confidence rating scale to record diagnoses. Receiver operating characteristic (ROC) analysis was done, and areas under the curves were computed (A(z)) as indicators of diagnostic accuracy. Analysis of variance (ANOVA) was used to test for effects of observer, imaging modality, and location on the detection of lesions. TACT-IR performed significantly better than DDR. There was a significant difference in the accuracy of diagnosis based on observers (P <0.001). TACT-IR appears to be the imaging modality of choice for the detection of small osseous changes on crestal bone in mid-buccal/lingual sites.

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.

Accuracy of extraoral tuned aperture computed tomography (TACT) for proximal caries detection

The objectives of this study were to compare the difference in the accuracy of proximal caries detection by extraoral tuned aperture computed tomography (TACT), intraoral TACT, and film radiographs. Eighty proximal surfaces of 40 extracted human maxillary teeth were used. A digital sensor was the image receptor for TACT. Film radiographs were acquired using Insight film. Nine basis images were acquired to reconstruct TACT slices. Seven observers scored the presence or absence of proximal caries using the 3 imaging modalities. The true presence of caries and its depth were determined using the sectional images obtained by micro CT. Among the image modalities and observers, possible differences in the area under the receiver operating characteristic curve were assessed by analysis of variance (ANOVA). ANOVA indicated no statistically significant differences between observers (P = .845), modalities (P = .657), and observer-modality combinations (P = .593). Within the limited range of this study, extraoral TACT was not statistically different from intraoral TACT or film radiographs for proximal caries detection. This suggests that extraoral TACT may have some clinical utility for caries diagnosis and that further study may be warranted.

SU-FF-I-35: Scatter Correction For Digital Tomosynthesis

Purpose: To investigate post acquisition scatter correction for digital tomosynthesis breast imaging. Method and Materials: Images of a composite phantom that was fabricated for evaluating digital breast tomosynthesis and used in a previous contrast-detail (CD) study [Suryanarayanan et al., Acad Radiol 7: 1085–1097, 2000] were used to test the scatter correction method. These images were acquired using a prototype full-field digital mammography (FFDM) system (GE Medical Systems, Milwaukee, WI) without an anti-scatter grid. The phantom comprised of a centrally placed CD insert (MedOptics, Tucson, AZ), blocks of cluttered paraffin and polymethyl methacrylate (PMMA), and beeswax surrounding it to provide a total phantom thickness of 54 mm. A set of 7 projection images of the phantom were acquired over an angular range of ± 18° at 60 intervals at 26 kVp, MoMo, and 32 mAs/view. The projection data sets were corrected for scatter using the scatter correction technique described by Trotter et al. [Proc. SPIE, vol. 4682: 469–478, 2002] and processed with an adaptive noise filter. The projection images were then reconstructed using back-projection and iterative restoration methods using Tuned Aperture Computed Tomography (TACT) [Webber et al., J. Digit. Imaging, 13: 90–97, 2000] software (developed by R.L. Webber, Wake Forest University, NC). The contrast-to-noise (CNR) ratio, signal-to-noise ratio (SNR), and % contrast were computed for one of the targets (2.32 mm diameter and 0.24 mm depth). Results: The uncorrected projection data set reconstructed with back-projection resulted in CNR = 3.0, SNR = 30.4, and % contrast = 11.1, while the scatter corrected and processed projection images yielded CNR = 10.2, SNR =60.7, and %contrast = 20.2. Conclusion: The results of this study indicate improved SNR, CNR, and % contrast after scatter correction in tomosynthesis. We are currently implementing and evaluating other scatter correction and reconstruction methods for digital tomosynthesis.

Three-dimensional tomo-synthesis/reconstruction methods and stereographic viewing display applied for dento-alveolar imaging

Reconstructed 2D slices, which were generated by the Tuned-Aperture Computed Tomography (TACT) algorithm, was applied for three-dimensional dento-alveolar imaging. Furthermore, glasses-free stereoscopic liquid-crystal display was applied to displaying dento-alveolar images. The comparative diagnostic values of tomo-synthesis, pseudo-hologram and 3D-CT images were evaluated. Due to the progress of 3D-viewing technology of the flat TFT display, the glasses-free stereoscopic display is available. Therefore, we examined to use a 3D-viewing display without eye-glasses to improve the recognition of 3D anatomical structure. 2D slices and pseudo-holograms were found to significantly improved depiction of the buccal/palatal position of the impacted tooth. In cases of horizontal impaction, pseudo-holograms as well as 3D-CT were preferred to 2D slices. 3D data set was easily modified by the provided software for the specific 3D-viewing system. The depth perception toward dento-alveolar structures somewhat improved by the stereoscopic view nevertheless observers were less attuned to the 3D-viewing display.

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.

Different digital imaging techniques in dental practice

Different imaging techniques are used to pick up the signal of interest in digital sensors, including charge-coupled devices (CCD), complementary metal-oxide semiconductors (CMOS), photostimulable phosphors plates (PSP) and tuned-aperture computed tomography (TACT) Digital radiography sensors are divided into: storage phosphor plates (SPP) called photostimulable phosphor plates (PSP), silicon devices such as charge-coupled devices (CCD) or complementary metal oxide semiconductors (CMOS). Relatively new type of imaging that may hold advantage over current radiographic modalities is tuned-aperture computed tomography (TACT).

Early detection and quantitative assessment of apical root resorption using crown-root ratio and tuned-aperture computed tomography (TACT)

EARLY DETECTION AND QUANTITATIVE ASSESSMENT OF APICAL ROOT RESORPTION USING CROWNROOT RATIO AND TUNED-APERTURE COMPUTED TOMOGRAPHY (TACT). Andre Mol, Julie H. Mol, Onanong Chai-u-dom, and Donald A. Tyndall, University of North Carolina, Chapel Hill, NC, and Chulalongkorn University, Bangkok, Thailand Background. Apical root resorption (ARR) is a complication of orthodontic treatment without clear causative factors. The relationship between causative factors and ARR may be obscured by inaccuracies in current methods of detection and quantification. Twodimensional imaging, lack of image standardization, as well as orthodontic tooth movement and remodeling of the surrounding tissues all pose considerable challenges. Objective. The purpose of this study was to develop and test a tuned-aperture computed tomography (TACT) application and to assess the validity of the crown-root ratio (CRR) method for the detection and quantification of small oblique apical root resorption lesions. Methods and materials. A registered (R) and a nonregistered (NR) version of TACT were tested. In TACT-R, the detector moved with the tooth through mechanical standardization. TACT-NR allowed the tooth to move independently of the detector. Ten basis images with a maximum angular disparity of 20° were used. Oblique slicing of TACT-NR follow-up stacks was required for registration with baseline stacks. A slice shifting algorithm was applied to prevent drifting of cross-talk shadows. Twenty extracted maxillary incisors placed in a widened alveolus of a maxillary jaw segment served as test and control sites. Baseline images were acquired without lesions. Follow-up images were acquired with and without lesions. Lesions were created by cutting an oblique buccolingual segment of the root just below the apex. Teeth were moved between baseline and follow-up (rotation and torque), and a bone-putty mixture was used to simulate remodeling of the surrounding bone. CRR, TACT-R, and TACT-NR were tested by 6 radiologists using ROC-analysis. CRR and TACT-R were also tested for their quantitative ability. Results. Low Az-values were obtained for CRR (0.68; SD .09), TACT-R (0.64; SD .09), and TACT-NR (0.60; SD .09). Differences between modalities were not statistically significant (ANOVA: P .05). Lesion quantification was poor for both CRR (R .03) and TACT-R (R .13). Conclusions. Crown-root ratio and TACT are not valid for the detection and quantification of small oblique apical root resorption lesions. Imaging techniques with greater angular disparity between basis images reduce cross-talk effects and are likely to improve performance.

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.

Excellence in publishing: the Wuehrmann prize

The American Academy of Oral and Maxillofacial Radiology (AAOMR) established “The Wuehrmann Prize” for the best radiology journal article of the year in 1995. The Award is named after Dr. Arthur H. Wuehrmann, a Distinguished Life Member of the Academy. Since then, eight published articles have been selected. The purpose of the award is to recognize excellence in publishing, which happens to be the motto of our publisher, Mosby Inc. The winning papers have been: White SC, Sapp JP, Seto BG, Mankovich NJ. Absence of radiometric differentiation between periapical cysts and granulomas. OOOOE 1994;78:650-4. Callender KI, Brooks SL. Usefullness of tomography in the evaluation of patients with temporomandibular joint disorders: a retrospective study. OOOOE 1996;81(6):710-9. Brooks SL, Brand JW, Gibbs SJ, Hollander L, Lurie AG, Omnell KA, Westessen PL, White SC. Imaging of the temporomandular joint: a position paper of the American Academy of Oral and Maxillofacial Radiology. OOOOE 1997;83(5):609-18. Christgau M, Hiller KA, Schmalz G, Kolbeck C, Wenzel A. Accuracy of quantitative digital subtraction radiography for determining changes in calcium mass in mandibular bone: an in vitro study. Journal of Periodontology Research. 1998;33(3):138-49. Bohay RN, Stephens RG, Kogan SL. A study of the impact of screening or selective radiography in the treatment and postdelivery outcome in edentulous patients. OOOOE 1998;86(3):353-9. White SC, Pullinger AG. Impact of TMJ radiographs on clinician decision making. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 1995;79:375-81. Liang H, Tyndall DA, Ludlow JB, Liang LA, Nunn NE. Accuracy of mandibular cross-sectional imaging with tuned-aperture computed tomography (TACT), iteratively reconstructed TACT, and multidirectional, linear, and transverse panoramic radiography. OOOOE 2001;91(5):594-602. Rushton VE, Lorner K, Worthington HU. Routine panoramic radiography of new adult patients in general dental practice: relevance of diagnostic yield to treatment and identification of radiographic selection criteria. OOOOE 2002;93(4):488-95. The Wuehrmann Prize is given to a paper published in OOOOE between July of the previous year and June of the year the prize is to be given. Papers eligible for the prize are those that present basic/clinical/epidemiological/survey research of relevance to OMFR that adheres to the principles of the scientific method. Position papers, case reports, and review articles are not considered for the Prize. Papers are judged based upon: (a) relevance to OMFR, (b) originality of research objectives and/or ideas presented, (c) innovativeness of study design (novelness of approaches/concepts), (d) appropriateness of epidemiological/statistical methods, and (e) clearness of presentation. The Awards Committee selects a Wuehrmann Prize Subcommittee, consisting of the Journal Section Editor as chair and 4 members of the Editorial Board, with a rotating membership. The Editor identifies approximately 7-10 notable articles meeting the criteria and provides the subcommittee with a list of these candidates within 2 weeks after publication of the June issue of OOOOE. Prior to this, subcommittee members may submit to the Editor titles of papers for consideration. The number of articles selected by the Editor for submission to the subcommittee is up to the discretion of the Editor. Each subcommittee member reads the candidate papers and ranks the top 5, sending the results to the Editor within one month. The Editor tallies the votes and notifies the Executive Secretary so the appropriate plaque can be made in time for the annual meeting. If there is not a clear winner after the first ballot, the subcommittee reaches consensus via e-mail and/or telephone discussion. Scanning the titles of the Prize winners reveals an interesting diversity of topics. New applications of technology, radiographic selection criteria, dental and jaw pathology, and an AAOMR position paper are included. Recognition of excellence in publishing should be a stimulating factor in the continuous improvement of the quality of articles in the Journal, and it is hoped that this Prize will result in that goal.

A look back at quad O &amp; E (aka“Triple O”)

A look back at quad O &amp; E (aka“Triple O”)

Influence of the number of basis images and projection array on caries detection using tuned aperture computed tomography (TACT)

OBJECTIVES to determine if the number of basis images and spatial distribution of the projection array used for TACT slice generation influence observer performance in caries detection. METHODS In the first experiment, 2, 4, 8 and 12 basis projections of each of 40 teeth were acquired using a CMOS digital radiography sensor. Projections were distributed radially in space using a 20 degree angular disparity. TACT slices were generated from the four subgroups of images, presented to eight observers, and viewed on a high-resolution monitor. Observers scored the presence/absence of caries using a 5-point confidence scale. Gold standard was histological examination of tooth sections. ROC curves measured observer diagnostic performance. ANOVA tested for significant differences between observers and experimental conditions. In the second experiment, the number of basis projections judged to be satisfactory for TACT slice generation was used. Horizontal and vertical linear arrays of projections were compared to the circular projection array. RESULTS There was a statistically significant difference between the numbers of basis projections in the detection of both occlusal (P=0.006) and proximal caries (P=0.005). No significant difference was found between projection arrays in the detection of either occlusal (P=0.065) or proximal (P=0.515) caries. CONCLUSIONS The number of TACT basis projections significantly influences caries detection. Eight or more images should be used. Either linear-vertical, linear-horizontal or circular arrays of basis projections may be used for TACT slice generation in caries detection tasks.

Evaluation of tuned aperture computed tomography (TACT) in the localization of simulated periodontal defects.

To compare the diagnostic efficacy of tuned aperture computed tomography (TACT) with the application of the 'buccal object rule' (BOR) in the localization of simulated periodontal defects. Thirty interproximal sites were selected in fifteen cadaver segments of maxillae and mandible. Artificial periodontal defects were created using round burs and 40% formic acid in the buccal, lingual or mid-buccolingual areas. Eight basis projections were obtained and TACT slices were reconstructed for each region of interest. Two of the basis images were used in application of BOR for localization of the defect. Eight observers scored the location of defects using TACT slices and the paired radiographs separately. Data were analysed using the kappa statistic and ANOVA. A mean weighted kappa of 0.14 for localization was obtained with both BOR and TACT. Using ANOVA, there was no significant difference between modality and observer. There was however, a significant difference (P=0.019) between different defect sizes. Both modalities performed better with larger defect sizes. TACT performed slightly better than BOR when the smaller lesions were included; however, with larger lesions, this trend was reversed. The results confirm the relationship between correlation distance (the resultant slice width) and object size in the application of TACT for localization. BOR remains a simple yet effective tool for localization. The clinical significance is not clear considering the low kappa scores obtained with both the modalities.

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 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.

Accuracy of mandibular cross-sectional imaging with tuned- aperture computed tomography (TACT), iteratively reconstructed TACT, and multidirectional, linear, and transverse panoramic tomography

Objective. This study was designed to compare 5 modalities with respect to accuracy in mandibular cross-sectional imaging. The modalities tested were tuned-aperture computed tomography (TACT), iteratively reconstructed TACT, multidirectional tomography, linear tomography, and transverse panoramic tomography. Study Design. Twenty sites were selected from 3 dry human mandibles, and cross-sectional views were imaged through use of each of the 5 modalities. A quantitative analysis included measurements of 2 linear distances; a qualitative study included image evaluation by 6 observers. A nested mixed analysis of variance model was used to control for mandibles and locations within mandibles for the quantitative analysis; the Cochran-Mantel-Haenszel test was used for the qualitative analysis. Results. There was a significant difference in measurement error for maximum height but not for width. There was also a significant difference in qualitative image evaluation results. Conclusions. Of the 5 modalities tested, the narrow-layer multidirectional tomographic technique produced the greatest diagnostic accuracy and quality in cross-sectional imaging. The transverse panoramic tomographic technique produced the least diagnostic accuracy and quality. Linear tomography, TACT, and iteratively reconstructed TACT were intermediate in accuracy and quality. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2001;91:594-602)