P.F. van der Stelt

Efficacy of digital intra-oral radiography in clinical dentistry

OBJECTIVES This article emphasizes the comparison of intra-oral digital imaging to film-based imaging. Additional possibilities of digital imaging that may contribute to system efficacy are discussed as well. STUDY SELECTION The main subjects for research in digital imaging are image quality, image acquisition, diagnostic quality, image manipulation, automated analysis, and application software. DATA SOURCES Representative articles on these subjects from the international literature are used for this review. Indirect digital imaging still requires film processing, sophisticated film digitizers, and time to digitize film. Although it is not an efficient method for the dental practice, digitization can be very useful for quantitative analysis of radiographs. Direct digital imaging is more efficient than indirect digital imaging. The main advantages are (semi) real time imaging, low X-ray dose requirements, and no need for chemical processing. In spite of a more limited resolution of the images, direct imaging may perform as accurately as film-based imaging. Direct image plate systems can well be used, for instance, for full-mouth series. The main application of direct sensor systems appears to be endodontology and implantology. In summary, direct digital imaging may be as efficient as film-based imaging in clinical dentistry. The computer provides for many additional options in digital imaging, such as the digital storage, compression, and exchange of radiographic information. Image manipulation (e.g. image enhancement, subtraction radiography and image reconstruction) and automated analysis may benefit radiodiagnosis. CONCLUSION It can be concluded that digital imaging certainly has great potential, especially with respect to improvement of diagnostic quality and automated image analysis.

The radiographic trabecular pattern of hips in patients with hip fractures and in elderly control subjects.

Due to the increasing number of osteoporotic fractures of hip, spine, and wrist there is a growing need for methods to track down the subjects with inferior bone structure and to monitor the effects of therapeutic measures. This study aims at a noninvasive diagnostic tool, deriving architectural properties of trabecular bone from in vivo measurements on plane radiographic films. Pelvic radiographs of the nonfractured hips of 81 patients with hip fractures and of the right hips of 74 controls were studied. The regions of interest, 2 x 2 cm2, located in the femoral neck, were sampled and digitized with a video camera connected to an image analysis system. Several geometrical and directional measurements were made. The measurements were evaluated by statistical comparison with fracture risk, gender, and Singh index. By discriminant analysis, type of fracture, as well as gender and Singh index could be predicted correctly for 58% of the subjects, whereas guessing would be correct in only 8%. It was found that the geometrical parameters discriminate between hips of controls and patients. With respect to the directional measurements associations were found with gender and Singh index. Although the new parameters assess fracture risk less accurately than bone density measurements, some parameters suggest by their behavior that they are relevant with respect to femoral bone architecture and its mechanical behavior. Although interpretation of the measurements in histological concepts requires methods that have been reported in literature only recently, it is concluded that digital analysis of the radiographic trabecular pattern is an interesting option to increase the diagnostic yield of plane film radiographs and to study the structure of bone in vivo.

The radiographic trabecular bone pattern during menopause.

The purpose of this study is to increase the diagnostic value of radiographs by observing the radiographic trabecular pattern during occasions of changing three-dimensional bone structure. We explored how the shape of the radiographic trabecular pattern of the distal radius relates to bone mineral density, time, and menopausal status. We found that the trabecular pattern correlates with bone mineral density and time, especially in the early years of the climacterium.

Detecting Reduced Bone Mineral Density From Dental Radiographs Using Statistical Shape Models

We describe a novel method of estimating reduced bone mineral density (BMD) from dental panoramic tomograms (DPTs), which show the entire mandible. Careful expert width measurement of the inferior mandibular cortex has been shown to be predictive of BMD in hip and spine osteopenia and osteoporosis. We have implemented a method of automatic measurement of the width by active shape model search, using as training data 132 DPTs of female subjects whose BMD has been established by dual-energy X-ray absorptiometry. We demonstrate that widths measured after fully automatic search are significantly correlated with BMD, and exhibit less variability than manual measurements made by different experts. The correlation is highest towards the lateral region of the mandible, in a position different from that previously employed for manual width measurement. An receiver-operator characteristic (ROC) analysis for identifying osteopenia (T < - 1: BMD more than one standard deviation below that of young healthy females) gives an area under curve (AUC) value of 0.64. Using a minimal interaction to initiate active shape model (ASM) search, the measurement can be made at the optimum region of the mandible, resulting in an AUC value of 0.71. Using an independent test set, AUC for detection of osteoporosis (T < -2.5) is 0.81.

Modern radiographic methods in the diagnosis of periodontal disease.

For many years, radiographs have been a valuable aid in the diagnosis of periodontal disease and the evaluation of treatment effects. Computer-based image acquisition and processing techniques will now further increase the importance of radiography in periodontal diagnosis.Temporal changes of lesions can be made easily visible by means of subtraction radiography based on digital images. This process requires a pair of images with identical gray-level distributions and projection geometry. The gray-level distribution and perspective projection of images can be corrected by means of digital image processing. A pair of identical images can thus be obtained without mechanical alignment of patient, film, and x-ray source. Algorithms have been developed for automatical determination of the borders of lesions and can subsequently produce quantitative information ranging from simple distance measurements to advanced multidimensional quantitation of image parameters. Accurate volume measurements can be carried out...For many years, radiographs have been a valuable aid in the diagnosis of periodontal disease and the evaluation of treatment effects. Computer-based image acquisition and processing techniques will now further increase the importance of radiography in periodontal diagnosis. Temporal changes of lesions can be made easily visible by means of subtraction radiography based on digital images. This process requires a pair of images with identical gray-level distributions and projection geometry. The gray-level distribution and perspective projection of images can be corrected by means of digital image processing. A pair of identical images can thus be obtained without mechanical alignment of patient, film, and x-ray source. Algorithms have been developed for automatical determination of the borders of lesions and can subsequently produce quantitative information ranging from simple distance measurements to advanced multidimensional quantitation of image parameters. Accurate volume measurements can be carried out by the utilization of calibration wedges in the image. Image reconstruction procedures, such as tomosynthesis, provide information about the third dimension, which is normally lost in conventional radiographic projections. The buccal and lingual sites of the alveolar crest can be inspected separately. The progress of computer-aided procedures as discussed in this paper appears to have great potential for the improvement of the radiographic diagnosis of periodontal lesions. Especially, the benefits of reproducibility and quantitative evaluation of treatment effects will greatly improve the role of radiography in periodontics.

Orientation of the trabecular pattern of the distal radius around the menopause

The trabecular pattern depicted on radiographs of the distal radius of women around the menopause is analysed by a new method to measure orientation. It is shown that the trabecular pattern on radiographs of the distal radius is aligned preferentially along the axial direction and to a lesser extent along the transverse direction. Two minima of orientation are found at 60 degrees off the axial direction. A significant correlation is found between the average value of the orientation in the radius and the average lumbar bone mineral density. It is known that the bone mineral content decreases around the menopause. Previous reports on the present images describe several features that were found to be related to bone mineral content and to time. The orientation of the trabecular pattern, however, is found to be independent of time, at least during the two years of the investigation. Therefore, it is concluded that the orientation of the radiographic trabecular pattern tends to remain stable even if some features of the pattern evolve. Previous studies on radiographs of the radius of children and elderly women and men provide evidence for the tendency of orientation to remain stable not only in women around the menopause, but also in men and women during the entire adult life.

Influence of cone beam CT scanning parameters on grey value measurements at an implant site

OBJECTIVES The aim of this study was to determine the grey value variation at the implant site with different scan settings, including field of view (FOV), spatial resolution, number of projections, exposure time and dose selections in two cone beam CT (CBCT) systems and to compare the results with those obtained from a multislice CT system. METHODS A partially edentulous human mandibular cadaver was scanned by three CT modalities: multislice CT (MSCT) (Philips, Best, the Netherlands), and two CBCT systems: (Accuitomo 170(®), Morita, Japan) and (NewTom 5G(®), QR, Verona, Italy). Using different scan settings 36 and 24 scans were obtained from the Accuitomo and the NewTom, respectively. The scans were converted to digital imaging and communications in medicine 3 format. The analysis of the data was performed using 3Diagnosys(®) software (v. 3.1, 3diemme, Cantù, Italy) and Geomagic studio(®) 2012 (Morrisville, NC). On the MSCT scan, one probe designating the site for pre-operative implant placement was inserted. The inserted probe on MSCT was transformed to the same region on each CBCT scan using a volume-based three-dimensional registration algorithm. The mean voxel grey value of the region around the probe was derived separately for each CBCT. The influence of scanning parameters on the measured mean voxel grey values was assessed. RESULTS Grey values in both CBCT systems significantly deviated from Hounsfield unit values measured with MSCT (p = 0.0001). In both CBCT systems, scan FOV and spatial resolution selections had a statistically significant influence on grey value measurements (p = 0.0001). The number of projections selection had a statistically significant influence in the Accuitomo system (p = 0.0001) while exposure time and dose selections had no statistically significant influence on grey value measurements in the NewTom (p = 0.43 and p = 0.37, respectively). CONCLUSIONS Grey-level values from CBCT images are influenced by device and scanning settings.

Longitudinal analysis of radiographic trabecular pattern by image processing.

To describe structural and textural changes in bone structure, the radiographic trabecular pattern of children, aged 4-14 years, was examined using a digital image processing system. This investigation is based on data from the Nijmegen Growth Study, a mixed-longitudinal growth study comprised of three birth cohorts, which were observed for five years. Of 3075 left hand-forearm radiographs of 426 children, a standard area of 10 x 10 mm of the radius was digitized and the trabecular pattern was described by ten image features. It is demonstrated that all image features show significant changes during the observation period (multivariate analysis of variance of p < 0.01). The age of the children correlates significantly with the image features (Spearmans Rho = 0.4; p < 0.05). Because of cohort effects, the three cohorts were studied separately. Highest correlations between age and trabecular pattern were shown in the cohort of the youngest children. The changes of the image features during the observation period seems to indicate that the fine trabecular pattern of young children changes into a coarser adult pattern. It is concluded that digital quantification of the radiographic trabecular pattern is appropriate to describe changes in trabecular bone.

Osteoporosis detection using intraoral densitometry

OBJECTIVES To determine the diagnostic accuracy of mandibular and maxillary bone density in detecting osteoporosis using receiver operating characteristic (ROC) analysis. METHODS 671 women between 45 years and 70 years of age underwent dual energy X-ray absorptiometry (DXA) of the hip and lumbar spine. This was the gold standard for diagnosing osteoporosis. Intraoral radiography of the upper and lower right premolar region was performed, using an aluminium wedge as a densitometric reference. Jaw bone density was determined using dedicated software. Observer differences and ROC curves were analysed. RESULTS For detecting osteoporosis using jaw bone density, the area under the ROC curve (A(z)) was 0.705. For separate analysis of mandibular and maxillary films, sensitivity varied from 33.9% to 38.7% and specificity from 83.5% to 85.3% when using a threshold of 4.3 mm Al equivalent. CONCLUSIONS Density of the premolar region reaches a fair diagnostic accuracy, which might improve when including additional factors in the analysis and refining the densitometric tool.

Bone density measurements in intra-oral radiographs

Jaw bone density measurements are applicable in many clinical situations to assess bone tissue. To be able to implement research findings in clinical reality, tools must be simple and low cost. Intra-oral radiographs including a reference material perform well as a densitometric tool. However, the inclusion of a reference material, usually in the form of a metal wedge, is an additional burden for the dentist. The aim of this study was to evaluate whether a reference step wedge is required for accurate densitometric results. Dual energy X-ray absorptiometry measurements and densitometric measurements on intra-oral radiographs using a custom-made software were performed on bone samples from the premolar region of the mandible. Observer agreement of bone density expressed as grey value was high. The correlation between mandibular bone mineral density and the densitometric values on intra-oral radiographs was substantially higher when the aluminium step wedge was included. The Wilcoxon test revealed no significant difference between the density measurements using nine or three steps of the Al reference wedge. Density determination of grey value and mm Aleq thickness value both have good intra- and inter-observer agreement. However, jaw bone densitometry is far more accurate when including a reference wedge.