Correlation of Trabecular Bone Structure with Age, Bone Mineral Density, and Osteoporotic Status: In Vivo Studies in the Distal Radius Using High Resolution Magnetic Resonance Imaging

Abstract

High resolution magnetic resonance (MR) images of the distal radius were obtained at 1.5 Tesla in premenopausal normal, postmenopausal normal, and postmenopausal osteoporotic women. The image resolution was 156 microm in plane and 700 microm in the slice direction; the total imaging time was approximately 16 minutes. An intensity-based thresholding technique was used to segment the images into trabecular bone and marrow, respectively. Extensions of standard stereological techniques were used to derive measures of trabecular bone structure from these segmented images. The parameters calculated included apparent measures of trabecular bone volume fraction, trabecular thickness, trabecular spacing, and trabecular number. Fractal-based texture parameters, such as the box-counting dimension, were also derived. Trabecular bone mineral density (BMD) and cortical bone mineral content (BMC) were measured in the distal radius using peripheral quantitative computed tomography (pQCT). In a subset of patients, spinal trabecular BMD was measured using quantitative computed tomography (QCT). Correlations between the indices of trabecular bone structure measured from these high-resolution MR images, age, BMD, and osteoporotic fracture status were examined. Cortical BMC and trabecular BMD at the distal radius, spinal BMD, trabecular bone volume fraction, trabecular thickness, trabecular number, and fractal dimension all decreased with age. Trabecular spacing showed the greatest percentage change and increased with age. In addition, significant differences were evident in spinal BMD, radial trabecular BMD, trabecular bone volume fraction, trabecular spacing, and trabecular number between the postmenopausal nonfracture and the postmenopausal osteoporotic subjects. Trabecular spacing and trabecular number showed moderate correlation with radial trabecular BMD but correlated poorly with radial cortical BMC. High resolution MR imaging, a potentially useful tool for quantifying trabecular structure in vivo, may have applications for understanding and evaluating skeletal changes related to age and osteoporosis.

Processing and Analysis of In Vivo High-Resolution MR Images of Trabecular Bone for Longitudinal Studies: Reproducibility of Structural Measures and Micro-Finite Element Analysis Derived Mechanical Properties

“…I M was taken as the intensity at the peak position plus half the peak width. Using the mean intensity of the trabecular region, I O , the threshold is set to give a fraction of bone pixels, f = N bone /N total , satisfying the equation fI B + (1-f)I M = I O [5]. The resulting binarized image for one slice is shown in Fig.…”

“…Magnetic resonance imaging (MRI) provides unique capabilities for the study of the structural aspects of both trabecular and cortical bone, allowing in vivo, noninvasive, three-dimensional (3D) structure assessment without the use of ionizing radiation. Previous studies have demonstrated the usefulness of both high-resolution imaging (HR-MRI) [1][2][3][4][5][6] and MR relaxometry [7][8][9][10][11] for deriving structural parameters for the assessment of trabecular bone. For the current study we are concerned with HR-MRI, in which the trabecular structure is determined indirectly from a scan in which the bone marrow shows as a high intensity and the signal voids are assumed to be volumes of bone.…”

Magnetic resonance imaging of normal and osteoarthritic trabecular bone structure in the human knee

“…The threshold depends significantly on the imaging modality and may vary depending on the operator. Based on a dual reference limit and assuming a biphasic model, as previously validated (20), a global threshold was calculated and the images were binarized into a bone phase and a marrow phase. The segmented binary image was used to compute (per slice and ROI) trabecular bone parameters, such as the apparent trabecular bone volume fraction (BV/TV), apparent trabecular number (Tb.N), apparent trabecular separation (Tb.Sp), and apparent trabecular thickness (Tb.Th) analogous to standard bone histomorphometry (25).…”

“…The assessment of human trabecular bone structure using MRI techniques showed that it was possible to quantify the trabecular architecture and derive such measures as trabecular width, trabecular bone volume fraction, and mean intercept length, as well as quantitative measures of texture, such as the fractal characteristics of the trabecular bone network (19)(20)(21). Majumdar et al (20) derived structural parameters in premenopausal healthy women and in postmenopausal women with osteoporosis and correlated the data with peripheral quantitative CT bone mineral density (BMD) and spinal fracture status.…”

“…Majumdar et al (20) derived structural parameters in premenopausal healthy women and in postmenopausal women with osteoporosis and correlated the data with peripheral quantitative CT bone mineral density (BMD) and spinal fracture status. Although MR techniques may result in partial volume effects because the spatial resolution is comparable with trabecular dimensions, Kothari et al (22) have shown that these effects may be minimized when the lower resolution of the slice is selected along the direction of primary trabecular orientation.…”