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Bone Radiography
1. Computerized Radiographic Analysis of Osteoporosis:  A Preliminary Evaluation

Measurement of bone mass is important in determining the risk for fracture and in following the course of patients on therapy for osteoporosis.  One of the current noninvasive methods of bone mass measurement is bone mineral densitometry (BMD).  BMD is a good predictor of fracture risk; however, there is considerable overlap in the BMD results between individuals who have fractured and those who have not.  Bone structure is also important in determining fracture risk.  We developed a new method to evaluate bone structure using conventional radiographs of the spine.  The method assesses bone structure non-invasively using a computerized texture analysis scheme with which to examine the trabecular pattern.  Standard lumbar spine radiographs of forty-three individuals were analyzed and compared to their BMD measurements obtained by dual photon absorptiometry.  Our method, evaluated at one point in time, was more effective than the BMD measurements at distinguishing cases with fractures elsewhere in the spine from those with no fracture.  Although further study is necessary, these preliminary results suggest that such a measure for bone structure combined with bone densitometry (bone mass) may lead to a more sensitive and specific predictor of osteoporosis and risk of fracture.  (366, 549, 642, 643)


2. Multifractal Radiographic Analysis of Osteoporosis

An important complication of osteoporosis is fracture.  Alteration in bone structure, as well as decreased bone mass, contributes to the tendency to fracture in osteoporosis.  Current methods that measure bone mass alone show substantial overlap of the measurements of osteoporotic patients who fracture with those that do not.  Our aim was to develop noninvasive methods of evaluating bone structure on radiographs to better predict fracture risk in osteoporosis.  Regions of interest (ROIs) were selected from digitized lateral lumbar spine radiographs of 43 patients being seen in an osteoporosis clinic.  The fractal dimension of these ROIs was estimated using a surface area method.  The ability of fractal dimension to distinguish between cases that had fracture elsewhere in the spine from those that did not, was evaluated using ROC analysis.  These results were compared with ROC analysis for these same patients using BMD measurements.  Significantly larger Az values were obtained using fractal dimension (0.97) than from using BMD (0.58), indicating a better test performance using fractal dimension.  Therefore, computerized radiographic methods to evaluate bone structure, such as fractal analysis, may be helpful in better determining fracture risk in osteoporosis.  (404)


 3. Normalized BMD as a Predictor of Bone Strength

In the noninvasive evaluation of bone quality, BMD has been shown to be the single most important predictor of bone strength and osteoporosis-related fracture.  Among the methods of measuring BMD, dual x-ray absorptiometry (DXA) has widespread acceptance due to its low radiation, low cost, and high precision.  However, DXA measures area BMD instead of true volumetric density; thus, a larger bone tends to have a high BMD than a smaller bone.  Therefore, the comparison of BMDs of bones of different sizes can be misleading.  In this study, we tried to compensate for the size effect by normalizing the area BMD with bone size as measured from a standard pelvic radiograph.  The overall method for calculation of normalized BMD included conventional area-based BMD from DXA and the extraction of geometric measures from pelvic radiographs.  The database for analysis included 34 femoral neck specimens.  Regression analysis was performed between the normalized volumetric BMD, measured from femoral neck region, and the mechanical properties obtained from trabecular bone cubes machined from the same region.  After normalization of the area BMD, the coefficient of determination increased from 0.30 to 0.43 for the Young modulus and from 0.27 to 0.37 for bone compressive strength.  A noninvasive method of normalizing BMD can improve the prediction of bone mechanical properties and has potential in monitoring changes in growing skeletons and in the clinical evaluation of bone quality.  (714)


4. Computerized Radiographic Texture Measures for Characterizing Bone Strength


We investigated computerized methods to ultimately characterize bone trabecular pattern from clinical skeletal radiographs.  A “phantom” was made for potential use in the development and evaluation of computerized methods for characterizing radiographic trabecular patterns and ultimately bone strength.  Femoral neck specimens were excised during total hip arthroplasties from subjects exhibiting a range of diseases.  To mimic the femoral neck in vivo, a “simulated clinical” setup was implemented in which specimens were exposed under conditions that yielded radiographs similar in appearance to standard pelvis radiographs.  Fourier-based and fractal-based texture measures were in the computer analysis; including RMS variation, first moment of the power spectrum, angular-dependent forms of these measures, and fractal dimension.  The texture measures obtained from the “simulated clinical” specimen films correlated modestly with those from direct exposure “verification” films of the specimens (R=0.59-0.69; P<0.0001).  We conclude that the femoral neck specimen “phantoms” may be useful in the development and evaluation of computerized methods for analyzing bone trabecular patterns from skeletal radiographs.  (666, 798)


5. Effect of Imaging Conditions on Computerized Analysis of Radiographic Bone Patterns


We developed computerized methods for characterizing the bone texture pattern from digitized skeletal radiographs.  For this method to be useful clinically, it must be able to distinguish between weak and strong bone under the range of exposure conditions potentially encountered in the clinical setting.  In this study, we examined the effect of exposure conditions on Fourier-based texture features.  Thirty-four femoral specimens from total hip arthroplasties were radiographed multiple times mechanical strength testing from which load to failure values were obtained.  The performance of the texture features was investigated in the task of distinguishing between strong and weak bone as characterized by the load to failure values.  The texture features showed no dependence upon focal spot size of the x-ray tube or magnification.  The texture features did show a dependence on relative exposure, peak kilo voltage, and amount of scattering material.  (699)


6. Radiographic Texture Analysis of the Calcaneus (heel) in the Prediction of Vertebral Fractures


Bone structure, in addition to bone mass, contributes to the strength of bone. In this study we investigated the ability of radiographic texture analysis of calcaneus bone densitometry images to characterize bone structure in order to predict the presence of vertebral fractures.  Our database consists of ninety-four subjects: fourteen with vertebral fractures and eighty without vertebral fractures. The calcaneus of each subject was scanned on a PIXI peripheral bone densitometer.  A 64x64 region of interest (ROI) was selected with the same center where the BMD ROI was placed by the PIXI software. Fourier-based texture features were used, including RMS variation and first moment of the power spectrum. ROC analysis was used to evaluate the performance of the features in the task of distinguishing between subjects with and without vertebral fractures. Linear discriminant analysis (LDA) was used to combine texture features with BMD measurements.  For the single ROI method, the RMS variation and first moment of the power spectrum yielded Az of 0.51 and 0.58, respectively. In comparison, BMD alone achieved an Az value of 0.56. Using the multiple-ROI method, the average of the first moment feature over the entire calcaneus yielded an Az value 0.61. The LDA achieved an Az of 0.73 with the combination of average RMS variation, average first moment, and BMD.  The texture analysis of calcaneus bone densitometer images may be useful in assessing bone structure and in predicting the presence of vertebral fractures. (955)


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This site was last updated 11/24/04