Digital Radiographic Image Processing and Analysis.

This article describes digital radiographic imaging and analysis from the basics of image capture to examples of some of the most advanced digital technologies currently available. The principles underlying the imaging technologies are described to provide a better understanding of their strengths and limitations.

Guide to Digital Radiographic Imaging.

This is a resource for clinicians who are considering purchasing a digital imaging system or those already using one who want to optimize its use. It covers selected topics in digital imaging fundamentals, detector technology, image processing and quality assurance. Through a critical appraisal of the strengths and limitations of digital imaging components, the goal of this guide is to contribute to the appropriate use of these systems to maximize the health benefit for patients.

Penetration of radiopaque dental restorative materials using a novel ultrasound imaging system.

PURPOSE: To determine whether a novel ultrasound imaging system could detect 25 microm thick cracks beneath gold, silver amalgam, and porcelain restorations on tooth phantoms. METHODS: Tooth phantoms were constructed using acoustically-matched composite to simulate dentin, with 25 microm thick water-filled cracks located approximately 1 mm inside the simulated dentin. Porcelain and gold restorations were bonded using resinous cement, and an amalgam restoration was attached using mechanical retention. A portion of the gold restoration was left unattached to simulate cement washout. A novel monostatic pulse-echo ultrasound system with a 19 MHz single-element PLZT transducer, custom transmit/receive electronics and signal processing with a Ga-In alloy couplant was used to measure the relative return echo amplitude from restoration surfaces, simulated dentin/restoration interfaces, and cracks. Extracted teeth were also used to demonstrate that the system was capable of detecting cracks in real teeth. RESULTS: Cracks were detected beneath porcelain and amalgam, and within a human molar. Cracks were not detected in simulated dentin beneath gold; however, simulated cement washout directly beneath gold was identified. The ability to detect defects in the phantom was dependent on the acoustic reflection coefficient between interfaces, the attenuation of each material, acoustic clutter within the phantom, and geometry. Gold restorations transmitted minimal acoustic energy due to their large acoustic impedance; however, the ability to distinguish the gold/cement interface from the gold/washout interface indicated that ultrasound can detect density changes immediately below restorations, such as caries, fractures, or debonding. The ability to penetrate resin-composite was also demonstrated.

Clinical and panoramic predictors of femur bone mineral density.

Dentists are a potentially valuable resource for initial patient screening for signs of osteoporosis, as individuals with osteoporosis have altered architecture of the inferior border of the mandible as seen on panoramic radiographs. Our aim was to evaluate the efficacy of combining clinical and dental panoramic radiographic risk factors for identifying individuals with low femoral bone mass. Bone mineral density was measured at the femoral neck and classified as normal, osteopenic or osteoporotic using WHO criteria in 227 Japanese postmenopausal women (33-84 years). Panoramic radiographs were made of all subjects. Mandibular cortical shape and width was determined and trabecular features were measured in each ramus. Mean subject age, height, and weight were significantly different in the three bone-density groups (P<0.0001). A classification and regression trees (CART) analysis using just clinical risk factors identified 136 (87%) of the 157 individuals with femoral osteopenia or osteoporosis. Mean mandible cortical width (P<0.0001), cortical index (P<0.0001) and trabecular features (P=0.02) were also significantly different in the three bone density groups. A CART analysis considering only radiographic features found 130 (83%) of the 157 individuals with femoral osteopenia or osteoporosis, although none of the subjects with osteoporosis was correctly identified. A CART analysis using both clinical and radiographic features found that the most useful risk factors were thickness of inferior border of the mandible and age. This algorithm identified 130 (83%) of the 157 individuals with femoral osteopenia or osteoporosis. The results of this study suggest that 1) clinical information is as useful as panoramic radiographic information for identifying subjects having low bone mass, and 2) dentists have sufficient clinical and radiographic information to play a useful role in screening for individuals with osteoporosis.

Fourier and wavelet analyses of dental radiographs detect trabecular changes in osteoporosis.

OBJECTIVES: Osteoporosis results in loss of bone mass and microarchitectural deterioration. Dental radiographs potentially offer a means of screening for osteoporosis as they are commonly made on adults. Spatial frequency analyses are well suited to detect subtle changes in image patterns. We hypothesize that individuals with osteoporosis exhibit an altered radiographic trabecular pattern that can be detected by spatial frequency and strut analysis. STUDY DESIGN: Maxillary and mandibular periapical radiographs of 26 women with osteoporosis and 23 controls were examined using one-dimensional discrete Fourier and wavelet analyses in both jaws to measure the spatial frequency distributions of trabecular structures. A strut analysis was also performed. RESULTS: Individuals with osteoporosis revealed an altered trabecular pattern compared to controls. Using Fourier and strut variables allows classification of subjects with 92% sensitivity, 96% specificity, and a 22% cross-validation error rate. Wavelet analysis was also useful but did not perform better than Fourier analysis for subject classification. CONCLUSIONS: Spatial frequency analysis of digitized dental radiographs, especially Fourier analysis, and strut analysis provide value for identifying individuals with osteoporosis.