Regional trabecular bone quality estimation for purposes of femoral bone strength prediction is important for improving the clinical assessment of osteoporotic fracture risk. In this study, we explore the ability of 3D Minkowski Functionals derived from multi-detector computed tomography (MDCT) images of proximal femur specimens in predicting their corresponding biomechanical strength. MDCT scans were acquired for 50 proximal femur specimens harvested from human cadavers. An automated volume of interest (VOI)-fitting algorithm was used to define a consistent volume in the femoral head of each specimen. In these VOIs, the trabecular bone micro-architecture was characterized by statistical moments of its BMD distribution and by topological features derived from Minkowski Functionals. A linear multiregression analysis and a support vector regression (SVR) algorithm with a linear kernel were used to predict the failure load (FL) from the feature sets; the predicted FL was compared to the true FL determined through biomechanical testing. The prediction performance was measured by the root mean square error (RMSE) for each feature set. The best prediction result was obtained from the Minkowski Functional surface used in combination with SVR, which had the lowest prediction error (RMSE = 0.939 ± 0.345) and which was significantly lower than mean BMD (RMSE = 1.075 ± 0.279, p<0.005). Our results indicate that the biomechanical strength prediction can be significantly improved in proximal femur specimens with Minkowski Functionals extracted from on MDCT images used in conjunction with support vector regression.
We investigate the use of different trabecular bone descriptors and advanced machine learning techniques to complement standard bone mineral density (BMD) measures derived from dual-energy x-ray absorptiometry (DXA) for improving clinical assessment of osteoporotic fracture risk. For this purpose, volumes of interest were extracted from the head, neck, and trochanter of 146 ex vivo proximal femur specimens on multidetector computer tomography. The trabecular bone captured was characterized with (1) statistical moments of the BMD distribution, (2) geometrical features derived from the scaling index method (SIM), and (3) morphometric parameters, such as bone fraction, trabecular thickness, etc. Feature sets comprising DXA BMD and such supplemental features were used to predict the failure load (FL) of the specimens, previously determined through biomechanical testing, with multiregression and support vector regression. Prediction performance was measured by the root mean square error (RMSE); correlation with measured FL was evaluated using the coefficient of determination R 2 . The best prediction performance was achieved by a combination of DXA BMD and SIM-derived geometric features derived from the femoral head (RMSE: 0.869±0.121 , R 2 : 0.68±0.079 ), which was significantly better than DXA BMD alone (RMSE: 0.948±0.119 , R 2 : 0.61±0.101 ) (p<10 −4 ). For multivariate feature sets, SVR outperformed multiregression (p<0.05 ). These results suggest that supplementing standard DXA BMD measurements with sophisticated femoral trabecular bone characterization and supervised learning techniques can significantly improve biomechanical strength prediction in proximal femur specimens.
Estimating local trabecular bone quality for purposes of femoral bone strength prediction is important for improving
the clinical assessment of osteoporotic hip fracture risk. In this study, we explore the ability of geometric features
derived from the Scaling Index Method (SIM) in predicting the biomechanical strength of proximal femur specimens
as visualized on multi-detector computed tomography (MDCT) images. MDCT scans were acquired for 50 proximal
femur specimens harvested from human cadavers. An automated volume of interest (VOI)-fitting algorithm was
used to define a consistent volume in the femoral head of each specimen. In these VOIs, the non-linear micro-structure of the trabecular bone was characterized by statistical moments of its BMD distribution and by local scaling properties derived from SIM. Linear multi-regression analysis and support vector regression with a linear kernel (SVRlin) were used to predict the failure load (FL) from the feature sets; the predicted FL was compared to the FL values determined through biomechanical testing. The prediction performance was measured by the root mean square error (RMSE) for each image feature on independent test set. The best prediction result was obtained from the SIM feature set with SVRlin, which had the lowest prediction error (RMSE = 0.842 ± 0.209) and which
was significantly lower than the conventionally used mean BMD (RMSE = 1.103 ± 0.262, , p<0.005). Our results indicate that the biomechanical strength prediction can be significantly improved in proximal femur specimens on MDCT images by using high-dimensional geometric features derived from SIM with support vector regression.
To improve the clinical assessment of osteoporotic hip fracture risk, recent computer-aided diagnosis systems
explore new approaches to estimate the local trabecular bone quality beyond bone density alone to predict femoral
bone strength. In this context, statistical bone mineral density (BMD) features extracted from multi-detector
computed tomography (MDCT) images of proximal femur specimens and different function approximations
methods were compared in their ability to predict the biomechanical strength. MDCT scans were acquired in
146 proximal femur specimens harvested from human cadavers. The femurs' failure load (FL) was determined
through biomechanical testing. An automated volume of interest (VOI)-fitting algorithm was used to define a
consistent volume in the femoral head of each specimen. In these VOIs, the trabecular bone was represented
by statistical moments of the BMD distribution and by pairwise spatial occurrence of BMD values using the
gray-level co-occurrence (GLCM) approach. A linear multi-regression analysis (MultiReg) and a support vector
regression algorithm with a linear kernel (SVRlin) were used to predict the FL from the image feature sets.
The prediction performance was measured by the root mean square error (RMSE) for each image feature on
independent test sets; in addition the coefficient of determination R2 was calculated. The best prediction
result was obtained with a GLCM feature set using SVRlin, which had the lowest prediction error (RSME =
1.040±0.143, R2 = 0.544) and which was significantly lower that the standard approach of using BMD.mean and
MultiReg (RSME = 1.093±0.133, R2 = 0.490, p<0.0001). The combined sets including BMD.mean and GLCM
features had a similar or slightly lower performance than using only GLCM features. The results indicate that the
performance of high-dimensional BMD features extracted from MDCT images in predicting the biomechanical
strength of proximal femur specimens can be significantly improved by using support vector regression.
KEYWORDS: Bone, Image registration, Magnetic resonance imaging, Image resolution, 3D image processing, Image analysis, Image segmentation, Medical imaging, Image processing, In vivo imaging
This study investigated the feasibility of automatic image registration of MR high-spatial resolution proximal femur
trabecular bone images as well as the effects of gray-level interpolation and volume of interest (VOI) misalignment on
MR-derived trabecular bone structure parameters. For six subjects, a baseline scan and a follow-up scan of the proximal
femur were acquired on the same day. An automatic image registration technique, based on mutual information, utilized
a baseline and a follow-up scan to compute transform parameters that aligned the two images. These parameters were
subsequently used to transform the follow-up image with three different gray-level interpolators. Nearest neighbor
interpolation and b-spline approximation did not significantly alter bone parameters, while linear interpolation
significantly modified bone parameters (p<0.01). Improvement in image alignment due to the automatic registration was
determined by visually inspecting difference images and 3D renderings. This work demonstrates the first application of
automatic registration, without prior segmentation, of high-spatial resolution trabecular bone MR images of the proximal
femur. Additionally, effects due to imprecise analysis volume alignment are investigated. Inherent heterogeneity in
trabecular bone structure and imprecise positioning of the VOI along the slice (A/P) direction resulted in significant
changes in bone parameters (p<0.01). Results suggest that automatic mutual information registration using nearest-neighbor
gray-level interpolation to transform the final image ensures VOI alignment between baseline and follow-up
images and does not compromise the integrity of MR-derived trabecular bone parameters.
The objective of this study was to develop a segmentation technique to quantify breast tissue and total breast volume from MRI data. The goal of our research is to quantify breast density using MRI to help better assess breast cancer risk for certain high-risk populations for whom mammography is of limited usefulness due to their high breast density. A semi-automatic segmentation technique was implemented based on a fuzzy inference system to segment 3D breast tissue from fat, and quantify the total volume of the breast in order to obtain an index of MR breast density on 10 healthy volunteers. The algorithm was based on two non-contrast 3D MR sequences. A fuzzy c-means algorithm was used to provide a first estimate of the segmentation of breast tissue from fat on specific slices. Based on the means and standard deviations of the segmented groups (breast tissue and fat) Sugeno-type fuzzy inference systems were built and then used as the main segmentation tools to segment surrounding slices. Results of volumetric measurements and breast density index obtained with the semi-automated method were compared with quantitative results obtained using classical global thresholding segmentation technique.
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