Spatial resolution and angular alignment tolerance in radiometric analysis of alveolar bone change

Low dose x-ray sources and high quantum efficiency sensors: the next challenge in dental digital imaging?

Objective(s). The major challenge encountered to decrease the milliamperes (mA) level in X-ray imaging systems is the quantum noise phenomena. This investigation evaluated dose exposure and image resolution of a low dose X-ray imaging (LDXI) prototype comprising a low mA X-ray source and a novel microlens-based sensor relative to current imaging technologies. Study Design. A LDXI in static (group 1) and dynamic (group 2) modes was compared to medical fluoroscopy (group 3), digital intraoral radiography (group 4), and CBCT scan (group 5) using a dental phantom. Results. The Mann-Whitney test showed no statistical significance (α = 0.01) in dose exposure between groups 1 and 3 and 1 and 4 and timing exposure (seconds) between groups 1 and 5 and 2 and 3. Image resolution test showed group 1 > group 4 > group 2 > group 3 > group 5. Conclusions. The LDXI proved the concept for obtaining a high definition image resolution for static and dynamic radiography at lower or similar dose exposure and smaller pixel size, respectively, when compared to current imaging technologies. Lower mA at the X-ray source and high QE at the detector level principles with microlens could be applied to current imaging technologies to considerably reduce dose exposure without compromising image resolution in the near future.

Digital Image Analysis of Cadaver Mandibular Trabecular Bone Patterns

BACKGROUND

The purpose of this study was to investigate the source of radiographic trabecular patterns by removing trabecular bone in four sequential steps from six cadaver mandible sections, radiographing the sections after each removal, and using four digital-image analysis methods to quantify any resulting changes to the radiographs.

METHODS

Mandible sections were cut sagittally into halves. Trabecular bone was removed from each section in four stages. Following each stage, standardized radiographs were taken, using direct digital equipment. Trabecular bone in the resulting digital images was measured with four methods. Mean gray level values (method 1) and cumulative percent histograms (method 2) were calculated from the raw data. Morphological image processing was used to skeletonize the trabecular structure, which was quantified by counting the number of trabecular ends and segments in the skeletonized images (method 3) and performing fractal analyses of the skeletonized images (method 4). Repeated measures analysis of variance (ANOVA) was used to test for changes in measurements attributable to bone removal.

RESULTS

Repeated measures ANOVA indicated that the use of gray levels, cumulative percent histograms, and morphologic operators resulted in highly significant changes in measurements following bone removal (P < 0.01). Ends and segments demonstrated similar performance, with changes highly significant over time (P < 0.01). Fractal analysis also resulted in highly significant changes over time (P < 0.01).

CONCLUSIONS

The analyses performed in this study demonstrated consistent image differences following the four steps of bone removal. These differences appeared whether light, cancellous bone or heavier endosteal bone was removed. These findings indicate that trabecular and endosteal bone combine to form the structure that most dentists identify as trabeculae on intraoral radiographs.

Evaluation of pluronic polyols as carriers for grafting materials: study in rat calvaria defects

BACKGROUND

Pluronic polyols are a family of non-ionic surfactants currently used as drug carriers for antibiotic, anti-inflammatory, and anti-neoplastic agents. Therapeutic administration of non-ionic surface-active agents is known to facilitate early collagen synthesis and microcirculation, thus promoting wound healing. The purpose of this study was to determine the in vivo effects of pluronic polyols combined with either an allograft or an alloplast on the healing of critical-sized calvarial defects.

METHODS

One hundred fifty (150) adult (95 to 105 days old) male Sprague-Dawley rats weighing between 375 and 425 g were randomly and evenly assigned to each of 15 separate treatment groups and anesthetized, and 8 mm calvarial critical-sized defects were created. Pluronic F-68 (F-68) or pluronic F-127 (F-127) was administered either topically or systemically and in conjuction with demineralized bone powder (DBP), tricalcium phosphate (TCP), or non-grafted controls. Pluronic polyols are easily mixed with either DBP or TCP to improve handling ease. Calvaria were harvested at 12 weeks postsurgery and evaluated histomorphometrically, by contact radiography with subsequent densitometric analysis, through energy spectrometry utilizing a scanning electron microscope, and by fluorescent microscopy.

RESULTS

There was a significant difference in the percentage of bone fill among the control, TCP, and DBP only groups, P <0.05. The only significant difference within any of these groups was between the TCP control and TCP plus systemic F-127, P<0.05.

CONCLUSIONS

Although there were isolated differences, the overall trend was that the pluronic polyol and the mode of administration did not result in a significant change in bone wound healing as measured by the percentage of bone fill. Pluronic polyols may be considered as carriers for osseous graft materials.

Estimation of skeletal bone mineral density by means of the trabecular pattern of the alveolar bone, its interdental thickness, and the bone mass of the mandible

OBJECTIVE

We sought to evaluate the use of the alveolar trabecular pattern, the mandibular alveolar bone mass (MABM) measured by photodensitometry, and the interdental alveolar thickness for prediction of the skeletal bone mineral density (BMD).

STUDY DESIGN

MABM and the coarseness of trabeculation were assessed by using periapical radiographs in 80 dentate women. The interdental alveolar thickness was measured on casts, and BMD of the forearm with dual X-ray absorptiometry.

RESULTS

Significant correlations were found between skeletal BMD and MABM (r = 0.46, P <.001) as well as the coarseness of the trabeculation (r = 0.62, P <.001). The interdental alveolar thickness improved the correlation between skeletal BMD and MABM (R2 = 0.44, P <.001). Age, but not interdental thickness, improved the correlation between the coarseness of trabeculation and skeletal BMD (R2 = 0.52, P <.001).

CONCLUSION

Evaluation of the coarseness of trabeculation of the alveolar bone as seen on intraoral radiographs is a helpful clinical indicator of skeletal BMD and better than densitometric measurements of the alveolar bone. Dense trabeculation is a strong indicator of high BMD, whereas sparse trabeculation may be used to predict low BMD.

Clinical validation of a new subtraction radiography technique for periodontal bone loss detection

BACKGROUND

Diagnostic subtraction radiography (DSR) is a new digital radiographic image subtraction method designed to enhance detection of crestal or periapical bone density changes and to help evaluate caries progression in teeth. In this clinical study, the performance of the DSR method was evaluated for its ability to detect periodontal bone loss and was compared with that of conventional evaluation of radiographs and the standardized cephalostat-guided image acquisition and subtraction technique (LRA) which served as the "gold standard."

METHODS

In each of 25 subjects with alveolar crestal bone loss created by periodontal surgery, one set of DSR radiographs and one set of LRA radiographs were obtained before and after the surgery. Subtraction images were then generated by both the proprietary DSR and the LRA techniques. Four viewers evaluated the paired film sets and both subtraction image sets using a 5 point confidence scale to determine the presence or absence of crestal bone loss. Receiver operating characteristics (ROC) statistical procedures were applied to analyze the diagnostic accuracy and statistical differences between the three imaging modalities.

RESULTS

The DSR subtraction viewing generated an ROC area of 0.882. For 2 of the viewers this represented a statistically significant gain (P <0.05) over the conventional viewing of the radiographs which had an average ROC area of 0.730. In comparison, the LRA method achieved an area of 0.954. The differences between the LRA and the DSR subtraction methods were not statistically significant, but the statistical power for claiming equality was low ranging from 0.2 to 0.6.

CONCLUSIONS

The use of the DSR technique in clinical radiographic image acquisition and subsequent subtraction analysis clearly enhanced the accuracy of alveolar crestal bone loss detection when compared to conventional film viewing. Because this methodology is less resource demanding than LRA and the film exposure techniques and computer-based image analysis skills may be acquired with only a few hours of training, the DSR has potential in clinical practice.

A lesion detectability simulation method for digital x-ray imaging

A simulation method is described in this work that aids in quantifying the upper limits of lesion detectability as a function of lesion size, lesion contrast, pixel size, and x-ray exposure for digital x-ray imaging systems. The method entails random lesion placement with subsequent simulated imaging on idealized x-ray detectors with no additive noise and 100% quantum detective efficiency. Lesions of different size and thickness were simulated. Mean (expectation) lesion signal-to-noise ratios (LSNRs) were calculated and receiver operating characteristic (ROC) curves were constructed based on LSNR ensembles. Mean (expectation) values of the areas under the ROC curves were calculated for lesions of varying size on pixel arrays of varying size at different exposures. Analyses were performed across several parameters, including lesion size, pixel size, and exposure levels representative of various areas of radiography. As expected, lesion detectability increased with lesion size, contrast, pixel size, and exposure. The model suggests that lesion detectability is strongly dependent on the relative alignment (phase) of the lesion with the pixel matrix for lesions on the order of the pixel size.

Three-dimensional alveolar bone morphology analysis using computed tomography

The purpose of the present study was to determine whether the use of 3-dimensional computed tomography (3DCT) is an effective method of imaging bone defect morphology caused by periodontal disease. A total of 186 sites from 9 patients were examined. Periodontal parameters were recorded after initial therapy. For the evaluation of bone resorption and root morphology, computed tomography (CT) scanning was performed and then CT images were reconstructed for 3-dimensional evaluation. Immediately prior to the surgery, bone sounding measurements were done under local anesthesia. The denuded bone measurement during periodontal surgery represented the true bone level. To compare the bone level obtained from 3DCT images with the true bone level, the examiner, without being informed of the patient's condition, traced the cemento-enamel junction (CEJ) and apical extent of the bone levels on the images of 3DCT, and measured the vertical distance between the CEJ and bone. The mean difference between 3DCT and the true bone level was 0.41+/-2.53 mm (mean+/-SD). The correlation between them showed a highly significant linear regression (R=0.75). However, the mean difference between the bone sounding level and the true bone level was 0.22+/-1.49 mm (R=0.91). Thus, bone sounding was slightly more accurate than 3DCT, but there was no significant difference between these two assessments (P >0.05). The results of present study indicate that 3DCT has the potential to allow precise assessment of bone defect caused by periodontal disease.