Biomedical subjects

D A Tyndall

Publications and source records attributed to D A Tyndall.

At least 19 recordsLinked to original sources

PubMed2004

Minimum number of basis projections for caries detection with local CT.

OBJECTIVES: To investigate the relationship between the number of basis projections for local computed tomography (CT) and the detection of proximal caries and to find a minimum number of projections needed to maintain diagnostic accuracy. METHODS: We presented observers (n = 12) with stacks of both axial and vertical CT slices of 23 extracted teeth placed in a dry human mandible. The slices were prepared with 14, 20, 33 and 100 basis projections. The observers scored the proximal surfaces for the presence of caries on a 1-5 confidence scale. The performance of the varying number of projections was compared with conventional digital radiographs. RESULTS: The performance of all four CT modalities was significantly better than conventional radiographs (P = 0.005 to P = 0.021) and showed a consistent increase with the number of projections. Diagnostic performance depended significantly on lesion depth (P = 0.00), but not on observer. CONCLUSIONS: We conclude that the number of CT projections used can be reduced at least to 20 with the diagnostic performance still markedly better than that of conventional film, provided that the observer can make use of both axial and vertical stacks of CT slices.

Dental Caries↗

PubMed2003

Effect of data compression on proximal caries detection: observer performance with DenOptix photostimulable phosphor images.

OBJECTIVES: To study the effect of lossy image compression on caries detection. Null hypothesis states no difference in caries detection efficacy among observers using original digital images versus images compressed at various rates of compression. METHODS: Digital images of 41 extracted posterior teeth were obtained with a storage phosphor DenOptix (Gendex DenOptix Imaging system) system. Images were exported in Tagged Image File Format (TIFF) and compressed with Joint Photographic Experts Group File Interchange Format (JFIF), as provided by the software of the imaging system. The compressions options JFIF100%, JFIF75% and JFIF50% resulted in reducing the image size to 1:2, 1:11 and 1:16, respectively. Eight observers evaluated the presence or absence of caries on a 5-point confidence scale. The actual caries status of each proximal surface was determined by ground section histology. Responses were evaluated by receiver operating characteristic (ROC) analysis. Areas under the curves (Az) were assessed using analysis of variance (ANOVA). RESULTS: The mean Az scores were 0.85 for original/uncompressed images, and 0.89 for JFIF100%, 0.88 for JFIF75% and 0.88 for JFIF50% images. These differences were not statistically significant (P = 0.26). Differences between observers were also not statistically significant (P = 0.12). CONCLUSIONS: JFIF compression at the level of 1:16 can be used without significant deterioration in diagnostic accuracy for proximal caries detection.

Analysis of Variance↗

PubMed2003

Detection of caries with local CT.

OBJECTIVES: An in vitro observer study of the detection of interproximal caries by local CT. METHODS: Detection of caries by means of conventional two-dimensional (2D) digital radiography and by two CT modalities was compared. Ground truth was obtained from histological examination of the sectioned teeth. Twenty-three extracted teeth (46 surfaces) were placed in groups of six in two dry mandibles. The observers (n=10) scored the proximal surfaces for the presence of caries on a 1-5 confidence scale. Data analysis used analysis of variance (a General Linear Model). Observer and method were entered into the model as within-subject variables and lesion depth was entered as a between-subjects variable. RESULTS: The analysis showed observer, method and lesion depth effects as well as several interaction effects to be significant. Observers performed significantly better with the vertically reformatted CT slices than with conventional radiographs (P=0.025). Furthermore, there were significant differences between observers, and several interactions were found to be significant. This means that although the reformatted slices performed best overall, this performance differed significantly depending on observer and on lesion depth. CONCLUSIONS: Vertically reformatted CT slices obtained with local CT performed significantly better than conventional 2D digital radiographs in visually detecting caries. Axial slices did not perform better than conventional radiographs. When vertically reformatted slices are used, local CT is a promising tool for the detection of interproximal caries.

Analysis of Variance↗

PubMed2002

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.

Analysis of Variance↗

PubMed2001

Fractal dimension analysis of weight-bearing bones of rats during skeletal unloading.

Fractal analysis was used to quantify changes in trabecular bone induced through the use of a rat tail-suspension model to simulate microgravity-induced osteopenia. Fractal dimensions were estimated from digitized radiographs obtained from tail-suspended and ambulatory rats. Fifty 4-month-old male Sprague-Dawley rats were divided into groups of 24 ambulatory (control) and 26 suspended (test) animals. Rats of both groups were killed after periods of 1, 4, and 8 weeks. Femurs and tibiae were removed and radiographed with standard intraoral films and digitized using a flatbed scanner. Square regions of interest were cropped at proximal, middle, and distal areas of each bone. Fractal dimensions were estimated from slopes of regression lines fitted to circularly averaged plots of log power vs. log spatial frequency. The results showed that the computed fractal dimensions were significantly greater for images of trabecular bones from tail-suspended groups than for ambulatory groups (p < 0.01) at 1 week. Periods between 1 and 4 weeks likewise yielded significantly different estimates (p < 0.05), consistent with an increase in bone loss. In the tibiae, the proximal regions of the suspended group produced significantly greater fractal dimensions than other regions (p < 0.05), which suggests they were more susceptible to unloading. The data are consistent with other studies demonstrating osteopenia in microgravity environments and the regional response to skeletal unloading. Thus, fractal analysis could be a useful technique to evaluate the structural changes of bone.

Animals↗

PubMed2001

Detection of simulated periodontal bone gain by digital subtraction radiography with tuned-aperture computed tomography. The effect of angular disparity.

OBJECTIVES: To investigate the influence of angular disparity on observer detection of simulated bone gain in digital subtraction radiography using tuned-aperture computed tomography (TACT). MATERIALS AND METHODS: Simulated periodontal defects were created in interproximal and buccal or lingual (tooth-obscured) areas of the premolar and molar regions of a dry human skull. Radiographs were obtained before and after known weights of amorphous bone were added to the defects to simulate bone gain. The skull was positioned in a multidirectional tomographic unit to achieve reproducibility. A series of nine basis images were acquired with a CMOS intra-oral receptor and repeated using angular disparities of 10 degrees, 20 degrees, and 30 degrees. Stacks of TACT slices generated from the basis images were paired for image-registration, histogram-equalization and subtraction using TACT Workbench. Eight calibrated observers randomly assessed the presence or absence of bone gain using a 5-point confidence scale. ROC curves were generated and A(z) values were analysed using ANOVA. RESULTS: There were significant differences in the performance of the observers (P=0.034), defect location (P=0.005), amount of bone gain (P<0.001), angular disparity (P=0.003) and angular disparity x defect location interaction (P=0.019). Mean A(z) values in detecting bone gain were 0.90, 0.85, 0.79 for angular disparities of 10 degrees, 20 degrees, and 30 degrees respectively. CONCLUSIONS: Smaller angular disparity provided better detection of bone gain with TACT-subtraction using nine basis-projections. This effect of angular disparity was especially evident with tooth-obscured defects.

Alveolar Bone Loss↗

PubMed2001

Evaluation of a new digital panoramic system: a comparison with film.

OBJECTIVES: To evaluate the diagnostic efficacy of the Orthophos DS digital panoramic system (Sirona, Bensheim, Germany) for the detection of dento-alveolar disease in comparison with film. METHODS: Five patients selected for admission to the School of Dentistry had a panoramic radiograph obtained with the Orthophos Plus (Sirona, Bensheim, Germany) system, a digital panoramic image obtained with the Orthophos DS (Sirona, Bensheim, Germany) system and a full mouth series. The ground truth was determined from the full mouth series by a panel of board certified oral and maxillofacial radiologists using the Delphi method. Four observers scored both the film and digital panoramic images for the presence of caries and marginal periodontitis. Results were statistically analysed using ROC analysis and ANOVA. RESULTS: There was no significant difference (P=0.704) between the two modalities for the detection of caries but there was a significant difference (P=0.015) for the detection of periodontal disease where conventional panoramic film performed better than the digital image. CONCLUSIONS: Though the conventional film was better than the digital image for the detection of periodontal disease, further studies are needed to determine the clinical significance of this result in relation to the potential advantages of digital technology.

Analysis of Variance↗

PubMed2001

Analysis of fractal dimensions of rat bones from film and digital images.

OBJECTIVES: (1) To compare the effect of two different intra-oral image receptors on estimates of fractal dimension; and (2) to determine the variations in fractal dimensions between the femur, tibia and humerus of the rat and between their proximal, middle and distal regions. METHODS: The left femur, tibia and humerus from 24 4-6-month-old Sprague-Dawley rats were radiographed using intra-oral film and a charge-coupled device (CCD). Films were digitized at a pixel density comparable to the CCD using a flat-bed scanner. Square regions of interest were selected from proximal, middle, and distal regions of each bone. Fractal dimensions were estimated from the slope of regression lines fitted to plots of log power against log spatial frequency. RESULTS: The fractal dimensions estimates from digitized films were significantly greater than those produced from the CCD (P=0.0008). Estimated fractal dimensions of three types of bone were not significantly different (P=0.0544); however, the three regions of bones were significantly different (P=0.0239). The fractal dimensions estimated from radiographs of the proximal and distal regions of the bones were lower than comparable estimates obtained from the middle region. CONCLUSIONS: Different types of image receptors significantly affect estimates of fractal dimension. There was no difference in the fractal dimensions of the different bones but the three regions differed significantly.

Analysis of Variance↗

PubMed2001

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

OBJECTIVES: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Algorithms↗

PubMed2001

The effect of the number of iterative restorations on tuned aperture computed tomography for approximal caries detection.

OBJECTIVES: To determine whether the number of iterative restorations performed on TACT images affects observers' ability to detect dental caries. METHODS: Eight TACT basis images of 40 extracted human posterior teeth were acquired using a CCD sensor. TACT slices of each tooth were generated and subsequently submitted to 1, 2 or 3 iterative restorations. Stacks of images from the three experimental conditions were presented to six observers in a balanced order, on a high-resolution 21' color monitor. Observers scored the presence or absence of approximal caries using a 5-point confidence scale. Observers' assessments were compared with the results of histological examination. Receiver operating characteristic (ROC) curves were generated and possible significant differences between observers and between modalities tested by ANOVA. The level of significance was set at alpha=0.05. Interobserver reliability was calculated as intraclass correlation. RESULTS: Mean areas under the ROC curves (A(z)) for the three experimental conditions were 0.791 (one iterative restoration), 0.81 (two iterative restorations), and 0.778 (three iterative restorations). ANOVA did not demonstrate any significant difference between modalities (P=0.25) but did so between observers (P=0.031). Interobserver reliability was similar for all experimental conditions tested. CONCLUSIONS: Varying the number of iterative restorations from one to three does not affect observers' ability to detect approximal caries with TACT slices.

Analysis of Variance↗

PubMed2001

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.

Analysis of Variance↗

PubMed2001

Effect of angular disparity of basis images and projection geometry on caries detection using tuned-aperture computed tomography.

OBJECTIVE: The purpose of this study was to determine whether projection geometry and angular disparity of basis images used for tuned-aperture computed tomography (TACT) slice generation influence observer performance in caries detection. STUDY DESIGN: Four sets of 8 projections of each of 40 teeth were acquired by using a digital sensor. Each set was radially distributed and subtended angular disparities of 10 degrees, 20 degrees, 30 degrees, and 40 degrees, representing strict projection geometries. A fifth set of images was acquired by using unconstrained geometry. TACT slices were generated from all experimental conditions and presented to 8 observers who viewed the images on a high-resolution monitor. Observers scored the presence/absence of caries with a 5-point confidence scale. Ground truth was achieved by histologic examination of tooth sections. Receiver operating characteristic curves measured observers' diagnostic performance. Analysis of variance was used to test for significant differences among observers and between experimental conditions. RESULTS: No statistically significant difference between angular disparities was found for the detection of either occlusal (P =.105) or proximal (P =.052) caries. No statistically significant difference between unconstrained and stringent projection geometries was found for the detection of either occlusal (P =.879) or proximal (P =.130) caries. CONCLUSIONS: Angular disparities ranging from 10 degrees to 40 degrees provide comparable performance in caries detection with TACT. Both unconstrained and stringent projection geometries may be used when reconstructing TACT slices for caries detection tasks.

Analysis of Variance↗

PubMed2001

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.

Algorithms↗

PubMed2000

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.

Anatomy, Cross-Sectional↗

PubMed1999

Dental anomalies associated with amelogenesis imperfecta: a radiographic assessment.

Amelogenesis imperfecta, a group of hereditary conditions primarily affecting the enamel, has been associated with dental anomalies, including taurodontism, congenitally missing teeth, delayed eruption, crown resorption, and abnormal enamel density. The purpose of this study was to assess the prevalence of these anomalies in an amelogenesis imperfecta population. The study group consisted of members of 9 unrelated families--22 family members with amelogenesis imperfecta and 13 unaffected family members. Panoramic radiographs were evaluated for taurodontism, congenitally missing teeth, delayed tooth eruption, pathologic dental resorption, pulp calcification, and radiographic enamel density. The prevalence of taurodontism was similar in people with amelogenesis imperfecta and normal people; all of the remaining parameters were more commonly observed in people with amelogenesis imperfecta. The radiographic enamel density was quantitatively reduced in teeth affected by amelogenesis imperfecta in comparison with teeth with normal enamel. These findings suggest that some of the features associated with amelogenesis imperfecta result from abnormal enamel formation (eg, decreased enamel density, crown resorption) whereas others may occur as a result of expression of the genetic mutation in cells other than ameloblasts (eg, abnormal eruption, pulp calcification).

Adolescent↗

PubMed1999

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.

Analysis of Variance↗

PubMed1999

Two- and three-dimensional imaging modalities for the detection of caries. A comparison between film, digital radiography and tuned aperture computed tomography (TACT).

OBJECTIVES: To compare the diagnostic performance provided by two- (film and digital radiography) and three-dimensional imaging modalities (TACT slices and TACT pseudoholograms) in the detection of primary caries. METHODS: Forty-two extracted human posterior teeth were mounted and imaged with conventional film and direct digital radiography. Free-hand positioning of a dental X-ray source was used for all exposures. From the digital images, iteratively restored TACT slices and TACT pseudoholograms were generated. Film images were viewed on a viewbox. Digital format images were viewed on a high-resolution monitor. Eight observers used a five-point scale to score the presence or absence of occlusal and proximal caries using the four image modalities. Observers' assessments were compared with the histological examination of tooth sections. Possible differences in ROC curve areas among image modalities, observers, and surfaces were assessed by ANOVA. Intra- and interobserver reliability as indicated by intraclass correlation was also calculated. RESULTS: There were no statistically significant differences between the diagnostic performances of film, digital radiography, TACT slices and TACT pseudoholograms in the detection of caries (P = 0.310). Intraclass correlation indicated the highest concordance both within and between observers when film was used for the evaluation. CONCLUSIONS: Under the experimental conditions of this study, three-dimensional TACT images did not improve caries detection over film or digital radiography. Further research should investigate the effects of imaging variables on TACT's diagnostic efficacy.

Analysis of Variance↗

PubMed1999

Cross-sectional presurgical implant imaging using tuned aperture computed tomography (TACT).

OBJECTIVES: To investigate tuned aperture computed tomography (TACT) as an alternative to conventional tomography for cross-sectional imaging of potential implant sites. METHODS: Twenty potential implant sites in three dry human mandibles were selected. Sixteen TACT basis projections were recorded on film using a linear array of source positions. Films were scanned and 20 TACT and iterative TACT slices were reconstructed using TACT Workbench software. Maximum height and width were measured on one representative slice of each site. Results were compared with the ground truth using ANOVA and Wilcoxon signed rank tests. RESULTS: The means of relative difference in maximum height were 1.55 and 1.56% for TACT and iterative TACT respectively (P = 0.8643). The means of relative difference in width were 5.96 and 6.36% for TACT and iterative TACT respectively (P = 0.4845). More than 75% measurements were within +/- 1 mm of ground truth for both modalities. CONCLUSIONS: TACT may provide an alternative to conventional tomography for dental implant imaging. Further investigations should be performed to explore factors affecting image quality.

Anatomy, Cross-Sectional↗