Survey of MRI Usefulness for the Clinical Assessment of Bone Microstructure (original) (raw)
Calcified tissue international, 2014
The utility of HR-CT to study longitudinal changes in bone microarchitecture is limited by subject radiation exposure. Although MR is not subject to this limitation, it is limited both by patient movement that occurs during prolonged scanning at distal sites, and by the signal-to-noise ratio that is achievable for high-resolution images in a reasonable scan time at proximal sites. Recently, a novel MR-based technique, fine structure analysis (FSA) (Chase et al. Localised one-dimensional magnetic resonance spatial frequency spectroscopy. PCT/US2012/068284 2012, James and Chase Magnetic field gradient structure characteristic assessment using one-dimensional (1D) spatial frequency distribution analysis. 7932720 B2, 2011) has been developed which provides both high-resolution and fast scan times, but which generates at a designated set of spatial positions (voxels) a one-dimensional signal of spatial frequencies. Appendix 1 provides a brief introduction to FSA. This article describes a...
Role of Magnetic Resonance for Assessing Structure and Function of Trabecular Bone
2002
The strength of trabecular bone and its resistance to fracture has traditionally been associated with apparent density. This paradigm assumes that neither the ultrastructural nor microstructural make-up of the bone is altered during aging and osteoporosis. There has been growing evidence against this view from both laboratory and clinical studies. Recent advances in noninvasive imaging technology, notably micro-magnetic resonance imaging (µ-MRI), offers an opportunity to test the hypothesis that architecture is an independent contributor to bone strength. Critical hurdles to overcome have their origin in the limited signal-to-noise ratio, which precludes imaging at a voxel size much smaller than trabecular thickness. The resulting partial volume blurring calls for more elaborate processing and analysis techniques. This article reviews new approaches conceived in the authors' laboratory toward acquisition, processing and structural analysis of trabecular bone images in the limited spatial resolution regime of in vivo µ-MRI. The method, termed 'virtual bone biopsy' (VBB), provides detailed insight into the three-dimensional trabecular network topology and scale at the distal radius or distal tibia serving as surrogate sites. The resulting VBB structural parameters are shown to be associated with the bone's biomechanical properties and fracture resistance and the technology has advanced to a stage permitting serial studies in laboratory animals and humans as a means to evaluate the effects of treatment. The method is currently confined to peripheral skeletal sites and its extension to typical fracture sites such as the proximal femur hinges on further advances in detection sensitivity.
MRI Techniques for the Examination of Trabecular Bone Structure
Current Medical Imaging Reviews, 2005
It is well known that bone mineral density measurement is a widely available means of identifying individuals with osteoporosis. However, bone strength depends not only on the amount of material but also on properties related to bone quality. Significant progress has been made in the development of magnetic resonance imaging (MRI) techniques for assessing bone status during the past years. This review discusses the technical principles, clinical applications, recent advances, limitations, and future trends of MRI techniques available for the diagnosis of osteoporosis. Using MRI, bone status can be evaluated either by T2* measurements, which are sensitive to field inhomogeneities caused by susceptibility differences at the marrowbone interfaces, or by high-resolution imaging. In T2* relaxometry, the decrease in marrow T2* measurements and its decay characteristics provide useful information about the structure and quality of the trabecular bone. T2* measurements have been performed at several locations of the axial and peripheral skeleton such as spine, proximal femur and calcaneus. It has also been shown that osteoporotic and normal subjects may be distinguished using T2* decay characteristics. In addition to T2* relaxometry, high-resolution MR imaging may be used to quantify trabecular bone architecture. Gradient echo and spin echo sequences have been used to obtain images in vitro and in vivo mainly at peripheral sites of the skeleton. Several image-processing methods have been applied to measure bone structure. Technological advances in MRI scanners offer exciting new possibilities in bone analysis and may contribute to our understanding of osteoporosis.
Quantitative MRI for the assessment of bone structure and function
NMR in Biomedicine, 2006
Osteoporosis is the most common degenerative disease in the elderly. It is characterized by low bone mass and structural deterioration of bone tissue, leading to morbidity and increased fracture risk in the hip, spine and wrist-all sites of predominantly trabecular bone. Bone densitometry, currently the standard methodology for diagnosis and treatment monitoring, has significant limitations in that it cannot provide information on the structural manifestations of the disease. Recent advances in imaging, in particular MRI, can now provide detailed insight into the architectural consequences of disease progression and regression in response to treatment. The focus of this review is on the emerging methodology of quantitative MRI for the assessment of structure and function of trabecular bone. During the past 10 years, various approaches have been explored for obtaining image-based quantitative information on trabecular architecture. Indirect methods that do not require resolution on the scale of individual trabeculae and therefore can be practiced at any skeletal location, make use of the induced magnetic fields in the intertrabecular space. These fields, which have their origin in the greater diamagnetism of bone relative to surrounding marrow, can be measured in various ways, most typically in the form of R 0 2 , the recoverable component of the total transverse relaxation rate. Alternatively, the trabecular network can be quantified by high-resolution MRI (m-MRI), which requires resolution adequate to at least partially resolve individual trabeculae. Micro-MRI-based structure analysis is therefore technically demanding in terms of image acquisition and algorithms needed to extract the structural information under conditions of limited signal-to-noise ratio and resolution. Other requirements that must be met include motion correction and image registration, both critical for achieving the reproducibility needed in repeat studies. Key clinical applications targeted involve fracture risk prediction and evaluation of the effect of therapeutic intervention.
Calcified Tissue International, 2005
The purpose of this study is to use high-resolution magnetic resonance (MR) imaging at 3 Tesla (3T) to quantify trabecular bone structure in vitro using femoral head specimens, and to correlate the calculated structure measures with those that were determined using microcomputed tomography (μCT), the standard of reference. Fifteen cylindrical cores were obtained from fresh femoral heads after total hip arthroplasty. MR images were obtained at 3T using a transmit-receive wrist coil. Highresolution coronal images were acquired using a modified three-dimensional (3D) fast-gradient echo sequence. From these data sets two-dimensional (2D) structural parameters analogous to bone histomorphometry were derived by using both mean intercept length (MIL) methods based on the plate model and the more recent model-assumption free 3D distance-transformation (DT) methods. The parameters measured by the 2D plate model-based MIL method and the DT method included apparent (App). BV/TV (bone volume/total volume), App. Tb.Th (trabecular thickness), App. Tb.Sp (trabecular separation), and App. Tb.N (trabecular number). Identical regions of interest were analyzed in the MR images and the μCT data sets, and similar structure measures were derived. The means and standard deviations of the parameters over all slices were calculated and MR-derived measures were correlated with those derived from the μCT data sets using linear regression analyses. Structure measures were overestimated with MRI, for example, the mean App. BV/TV was 0.45 for MRI and 0.20 for μCT, and the slope of the graph was 1.45. App. Tb.Th was overestimated by a factor of 1.9, whereas App. Tb.Sp was underestimated; Tb.N showed the smallest effect. Correlations between the individual parameters were excellent (App. BV/TV, r 2 = 0.82; App. Tb.Sp, r 2 = 0.84; App. Tb.N, r 2 = 0.81), except for App. Tb.Th (r 2 = 0.67). The results of this study show that trabecular bone structure measures may be obtained using 3T MR imaging. These measures, although higher than the standard of reference, show a highly significant correlation with true structure measures obtained by μCT.
Imaging techniques for evaluating bone microarchitecture
Joint Bone Spine, 2006
At present, fracture risk prediction in the individual patient relies chiefly on bone mineral density (BMD) measurements. However, many lines of evidence indicate that the decreased bone strength characteristic of osteoporosis is dependent not only on BMD, but also on other factors, most notably bone microarchitecture. Here, we review available tools for characterizing trabecular microarchitecture (in terms of morphology, topology, and texture) and for obtaining 2D and 3D images (using radiography, computed tomography, and magnetic resonance imaging). Bone microarchitecture imaging is a noninvasive method that may improve fracture risk prediction in the individual patient, shed light on the pathophysiology of osteoporosis, and help to monitor the effects of treatments. Among the various methods available to date, magnetic resonance imaging has the advantage of involving no radiation exposure, although its limited availability restricts its usefulness for studying vast populations. Regardless of the methods selected to assess bone microarchitecture, there is a need for validated standardized parameters capable of improving fracture risk prediction in longitudinal studies.
Trabecular Bone Assessment Using Magnetic-Resonance Imaging: A Pilot Study
International Journal of Environmental Research and Public Health
The aim of this study was to assess trabecular bone morphology via magnetic-resonance imaging (MRI) using microcomputed tomography (µCT) as the control group. Porcine bone samples were scanned with T1-weighted turbo spin echo sequence imaging, using TR 25 ms, TE 3.5 ms, FOV 100 × 100 × 90, voxel size 0.22 × 0.22 × 0.50 mm, and scan time of 11:18. µCT was used as the control group with 80 kV, 125 mA, and a voxel size of 16 µm. The trabecular bone was segmented on the basis of a reference threshold value and morphological parameters. Bone volume (BV), Bone-volume fraction (BvTv), Bone specific surface (BsBv), trabecular thickness (TbTh), and trabecular separation (TbSp) were evaluated. Paired t-test and Pearson correlation test were performed at p = 0.05. MRI overestimated BV, BvTv, TbTh, and TbSp values. BsBv was the only parameter that was underestimated by MRI. High statistical correlation (r = 0.826; p < 0.05) was found for BV measurements. Within the limitations of this study,...
Osteoporosis International, 2008
Summary In vivo high-resolution peripheral quantitative micro-CT (HR-pQCT) is a new modality for imaging peripheral sites like the distal tibia and the distal radius, providing structural bone parameters. Comparing HR-pQCT with MRI, we found that both modalities are capable of offering meaningful information on trabecular structure. Background Magnetic resonance imaging (MRI) has emerged as the leading in vivo method for measuring trabecular bone micro-architecture and providing structural information. Recently, an in vivo HR-pQCT modality was introduced for imaging peripheral sites like the distal tibia and the distal radius, providing structural bone parameters. The goal of this work was to compare and evaluate the performances and in vivo capabilities of HR-pQCT in comparison with MRI at 3 Tesla. Methods To this end images of 8 human specimens (5 tibiae and 3 radii) and 11 participants (6 tibia and 5 radii) were acquired with both modalities. Additionally, the radius specimens were scanned with micro-CT (μCT), which was used as a standard of reference. Structural parameters calculated from MRI were compared with results from HR-pQCT images and additionally μCT for the radii specimens. Results High correlations (r > 0.7) were found for trabecular number and trabecular spacing between the two modalities in vivo and ex vivo. 2D and 3D analysis revealed high correlations (r > 0.8) in structural bone parameters for all measurements. Using micro-CT as standard of reference both results from QCT and MRI correlated well. Conclusion Both imaging modalities were found to perform equally well regarding trabecular bone measurements.