Biomedical subjects

W G Geraets

Publications and source records attributed to W G Geraets.

At least 19 recordsLinked to original sources

PubMed1999

Effect of noise on the compressibility and diagnostic accuracy for caries detection of digital bitewing radiographs.

OBJECTIVES: To determine the effect of noise on the compressibility and the diagnostic accuracy for caries detection of digital bitewing radiographs. METHODS: Bitewing radiographs of patients were obtained with a storage phosphor (Digora, Soredex, Helsinki, Finland) and compressed at different JPEG compression levels (2, 27, 53 and 128). A just noticeable difference study was performed to select a compression level to study the added noise effect. Gaussian noise was added at low, medium, and high levels to both the original and compressed images. Seven observers examined the selected approximal surfaces to identify the caries depth. ROC analysis was performed together with ANOVA at P = 0.05. RESULTS: The compressibility of the images decreased as the noise level increased. ROC analysis revealed no significant difference between the original and compressed images within the same noise level (P > 0.06). With added noise compressed/decompressed images had a higher Az than the corresponding original images. CONCLUSIONS: JPEG compression at level 27 can be used without a significant deterioration in diagnostic accuracy. Compression at this level seemed to reduce the effect of noise to some extent.

Analysis of Variance↗

PubMed1998

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.

Age Factors↗

PubMed1998

Comparison of two methods for measuring orientation.

At the Department of Dental Radiology of ACTA, the line fraction deviation (LFD) method was developed to measure orientation on radiographic trabecular patterns. This article explains the measurement of the LFD index of orientation in a downscaled model. When investigations began to produce noteworthy results, the need for deeper understanding of the method and the resulting diagrams increased. Because it had previously been applied on rather complex patterns originating from bone it seemed worthwhile to study simpler images as well, which might yield a more intuitive understanding of the diagrams. Moreover, it seemed useful to compare the new LFD method with the well-accepted mean intercept length (MIL) method. Fifty images originating from cancellous bone structures and 25 drawings were analyzed. The results show that the MIL method tends to produce ellipses (not only on images originating from bone), and also that the LFD method is more sensitive to anisotropy.

Anisotropy↗

PubMed1998

Radiographic assessment of changes in marginal bone around endosseous implants supporting mandibular overdentures.

OBJECTIVES: To evaluate the reliability of a new method for quantification of radiographic changes in the marginal bone around implants. METHODS: Three groups of seven patients treated with an overdenture supported by two endosseous implants (Brnemark, n = 7 patients; IMZ, n = 7 patients; ITI Bonefit, n = 7 patients) were selected. Six weeks after loading the implants, radiographs were obtained using the long cone technique and an aiming device, scanned and digitized. Two observers measured the height and area of the peri-implant bone defects twice. The difference between measurements was statistically analysed using paired t-tests. RESULTS: There were small differences in interobserver error for the Brnemark implant system (P < 0.05), but no significant differences for the IMZ and ITI Bonefit. There were no significant difference in intraobserver error with any of the three implant systems (P > 0.05). CONCLUSIONS: The newly developed technique by measuring the area of the defect overcomes some drawbacks of existing techniques for quantification of peri-implant bone loss in the mandible.

Alveolar Bone Loss↗

PubMed1998

A radiographic method for measuring radiation dose based on beam quality.

OBJECTIVES: To develop a radiographic method for measuring radiation dose based on beam quality for inexpensive postal surveys of general dental practitioners. METHODS: Different beam qualities were simulated to expose a commercially available film (X-Omat MA 18 x 22.4 cm, Ready Pack, Kodak Pathe, Paris, France). Density and contrast curves were fitted by means of 4th-degree polynomial functions. The curves were used to estimate beam quality (as the first HVL) and radiation dose in air for 22 different dental X-ray machines by means of linear interpolation. These estimations were compared with the measurements obtained with the NERO system and an ionization chamber (paired t-test). RESULTS: No significant differences were found between the radiographic and the conventional methods in determining beam quality and radiation dose. CONCLUSIONS: The radiographic method can be used to determine beam quality and radiation dose of dental X-ray machines from a single exposure. The radiographic method is simple and inexpensive and causes a minimum of disruption to the dental practice.

Absorptiometry, Photon↗

PubMed1998

Agreement between radiographic and photographic trabecular patterns.

PURPOSE: It has been hypothesized that photographs can facilitate the interpretation of the radiographic characteristics of trabecular bone. The reliability of these photographic and radiographic approaches has been determined, as have various agreements between the two approaches and their correlations with biomechanical characteristics. MATERIAL AND METHODS: Fourteen vertebral bodies were obtained at autopsy from 6 women and 8 men aged 22-76 years. Photographs (n = 28) and radiographs (n = 28) were taken of midsagittal slices from the third lumbar vertebra. The radiographs and photographs were digitized and the geometric properties of the trabecular architecture were then determined with a digital image analysis technique. Information on the compressive strength and ash density of the vertebral body was also available. RESULTS: The geometric properties of both radiographs and photographs could be measured with a high degree of reliability (Cronbach's alpha > 0.85). Agreement between the radiographic and photographic approaches was mediocre as only the radiographic measurements showed significant correlations (p < 0.05) with the biomechanical characteristics. We suggest that optical phenomena may result in the insignificant correlations between the photographs and the biomechanical characteristics. CONCLUSION: For digital image processing, radiography offers a superior description of the architecture of trabecular bone to that offered by photography.

Adult↗

PubMed1997

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.

Analysis of Variance↗

PubMed1997

Impact of scale standardization on images of digital radiography systems.

OBJECTIVES: To test the effect of altering image size on diagnostic quality. METHODS: Endodontic files, size 10 and 15 were prepared to full root length and 1.5 mm short, in upper and lower molars and premolars. Digital images of the Sidexis (S) and Visualix/Vixa (V) system were reduced in size to Digora (D) scale, and the D images were enlarged to S scale. ROC analysis was performed and data analysed with MANOVA statistics. RESULTS: Assessment of root canal length with file size 10 was less accurate for the S images reduced in size, compared with the original S images (P < 0.011). All other differences were not significant (P > 0.081). CONCLUSIONS: Relevant diagnostic information may be lost when images are reduced in size. Therefore, for optimal presentation, the smaller images should be enlarged rather than the larger ones reduced.

Analysis of Variance↗

PubMed1997

Reliability of an image analysis system for quantifying the radiographic trabecular pattern.

A reliability evaluation technique was used to examine the reliability of an image analysis system of the trabecular pattern and to determine the contribution of three possible sources of error variance. Two series of radiographs were taken of 14 lumbar vertebral slices (28 radiographs). Every radiograph was placed on a viewing box for digitization four times by a single operator (112 positions of radiographs) and from every position of a radiograph an area of 15 mm x 15 mm was digitized twice (224 samples for analysis). Ten geometrical characteristics of the trabecular pattern were studied and its orientation was analyzed in 12 directions. Reliability was determined by calculating Cronbach's alpha. This design enabled dividing the measurement error (1-alpha) into fractions associated with the X-ray procedure, the operator and the system. Using this reliability evaluation technique, it was found that the orientation variables are more reliable than the geometric variables. It was found that effort to increase the reliability should be directed toward improving the technical procedure of this image analysis system. Also, repeated measurements will increase the reliability. The number of repeated measurements based on a desired reliability can be calculated. This procedure of evaluation gives the opportunity to select a source of error variance which have to be reduced to increase reliability most effectively.

Adult↗

PubMed1996

Relations between radiographic trabecular pattern and biomechanical characteristics of human vertebrae.

PURPOSE: Relations between the radiographic trabecular pattern and the biomechanical characteristics of bone were studied. MATERIAL AND METHODS: The material comprised L2 and L3 vertebral bodies of 14 individuals (aged 22-76 years; 6 women and 8 men). Compressive strength and ash density of the complete L2 vertebral body were determined. Of the L3 vertebral body, ash density and compressive strength in both horizontal and vertical directions were measured on cylinders of merely trabecular bone. Radiographs were taken of a midsagittal slice of L3 vertebrae. They were digitized to measure trabecular bone geometry and orientation. The procedure was repeated several times to obtain reliable measures. RESULTS: The radiographic trabecular pattern was significantly related to compressive strength, ash density and age. One of the radiographic geometric features in particular seems to offer information concerning the structural integrity of the trabecular architecture. CONCLUSION: Analysis of the radiographic trabecular pattern appears to be a promising technique for prediction of trabecular bone strength.

Aging↗

PubMed1995

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 (Spearman's 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.

Adolescent↗

PubMed1994

An analysis of the orientation of the radiographic trabecular pattern in the distal radius of children.

A digital image processing system was used to study changes in orientation of the radiographic trabecular pattern of bone in children aged 4-14 years. The radiographs originated from a mixed-longitudinal growth study (The Nijmegen Growth Study), which comprised of three birth cohorts and which was carried out between 1971 and 1975. Of 3075 left hand-forearm radiographs of 426 children, the orientation of the trabecular pattern of the radius was analysed in twelve directions on a standard area of 10 x 10 millimetres. It was demonstrated that the trabecular pattern of the radius shows two predominant directions of orientation: along and perpendicular to the long axis of the radius. Spearman's Rank Correlations were calculated between direction of orientation and age of the children for the total population as well as for the cohorts separately, because the existence of cohorts-effects. The cohort of the youngest children showed more and higher significant correlations than the other cohorts, indicating that the trabecular pattern of young children is more subjected to changes. The results indicate that the prevalence of trabeculae orientated perpendicular to the long axis of the radius decreases. We speculate that this development reflects the effects of changes in mechanical loading in that direction during growth and development resulting in functional adaptation of the trabecular bone.

Adaptation, Biological↗

PubMed1994

Longitudinal changes in the orientation of trabecular bone in relation to the location in the distal radius.

The aim of this study was to examine changes in orientation of trabecular bone during growth and development in relation to the location of trabeculae between the epiphysial growth plate and the marrow cavity. Five annual hand-wrist radiographs of 57 children between 4-9 years of age, originating from the Nijmegen Growth Study, were analysed by a digital image processing system. Analysis was carried out on four adjacent areas of 7 mm x 7 mm located in the distal head of the radius between the epiphyseal growthplate and the marrow cavity. The orientation of the trabecular pattern was measured in twelve directions. The orientation of trabeculae at a standardized distance from the epiphysial growth plate did not change significantly during growth and development. The orientation in directions perpendicular to the long axis of the radius was higher in newly formed trabecular bone, which is located just below the epiphysial growthplate, than in older trabecular bone at a larger distance from the epiphysial growth plate. Observation of one single area during five years of growth and development showed a comparable development.

Aging↗

PubMed1992

Cariogenic changes in dental enamel of boys and girls in relation to salivary properties. II. Radiological examination.

In earlier clinical studies of a group of children subjected to an intense fluoride treatment programme several salivary properties were related to cariogenic changes in the enamel surface, as assessed by mirror and probe. In this study the relationship between salivary parameters and cariogenic changes was investigated on bitewings taken from the same teeth. Inverse correlations were found between the acid producing capacity of the micro-organisms in the saliva (as determined in the Snyder test) and most cariogenic changes detected in bitewings particularly in boys. These radiologically detected changes in enamel were the reverse of those obtained clinically. These discrepancies were explained by differences in sensitivity between clinical and radiological techniques used to diagnose cariogenic changes. In contrast it was confirmed radiologically that for girls the P concentration in saliva and for boys the amount of resting saliva are important for preventing extension of caries into deeper layers of enamel.

Adolescent↗

PubMed1992

Relationship between cariogenic events and salivary tests in boys and girls: oral examination.

For boys and girls several salivary tests have been correlated with the following early cariogenic processes developing simultaneously in dental enamel: initiation, regression, stabilization and progression. These events were observed clinically during three consecutive intervals. Only correlations, significant during at least two random intervals were discussed. The Snyder test determined at 24 hours was significantly positively correlated with most events confined to the enamel surfaces and only the Snyder test determined at 48 hours in stimulated saliva appeared to be significantly positively related with deeper processes such as progression. In addition, the mineral composition of Ca2+, P and Mg2+ in saliva was significantly related to cariogenic events in the enamel surfaces of girls, and its viscosity for boys. Finally, and most interesting from a clinical point of view, was the fact that caries progression was negatively related with P concentrations in both unstimulated and stimulated saliva for girls. For boys a negative correlation was found between caries progression and flow of stimulated saliva.

Adolescent↗

PubMed1992

Differences between primary and permanent teeth in posteruptive age dependency of radiological changes in enamel during the development of approximal caries.

A longitudinal radiological study of children (N = 549) who participated in a comprehensive preventive maintenance program showed that caries related events in the approximal surfaces of permanent teeth differed from those in deciduous teeth. Changes in the approximal surfaces of the younger permanent teeth were more pronounced than of the older primary teeth and differed significantly from 1 year to 2.5 years. These findings can be explained by posteruptive maturation of tooth enamel.

Adolescent↗

PubMed1991

Computer-aided interpretation and quantification of angular periodontal bone defects on dental radiographs.

Capabilities of human observers to detect and describe small bone defects objectively are limited. Digital image processing can provide a useful contribution to the diagnostic process. This paper describes the evaluation of a computer-aided procedure for the interpretation and quantification of angular periodontal bone defects on dental radiographs. The computer-aided procedure was able to rank series of artificial periodontal bone lesions as accurate as experienced clinicians. Comparison of data from clinical inspection of lesions during surgery and quantitative results of the digitized procedure shows that the latter produced reliable information on the lesions size. Reproducibility is satisfactory. It was concluded that computer-aided detection and description of periodontal bone defects decreases the interobserver variability in general and the time-dependent variability in repeated assessments of a single observer.

Alveolar Bone Loss↗

PubMed1991

[Approximal caries in children].

A longitudinal radiological study in children (N = 549) who participated in a comprehensive maintenance program (they were treated in the clinic of the Department of Pedodontics of the Academic Centre for Dentistry Amsterdam) suggests that changes in the approximal surfaces of deciduous molars may differ from the changes in the approximal surfaces of permanent (pre)molars. Regression and initiation possibly occur more frequently in the deciduous teeth than in permanent teeth.

Adolescent↗