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1.
J Magn Reson Imaging ; 33(5): 1229-34, 2011 May.
Article in English | MEDLINE | ID: mdl-21509883

ABSTRACT

PURPOSE: To present a novel technique for measuring tissue enhancement in breast fibroglandular tissue regions on contrast-enhanced breast magnetic resonance imaging (MRI) aimed at quantifying the enhancement of breast parenchyma, also known as "background enhancement." MATERIALS AND METHODS: Our quantitative method for measuring breast MRI background enhancement was evaluated in a population of 16 healthy volunteers. We also demonstrate the use of our new technique in the case study of one subject classified as high risk for developing breast cancer who underwent 3 months of tamoxifen therapy. RESULTS: We obtained quantitative measures of background enhancement in all cases. The high-risk patient exhibited a 37% mean reduction in background enhancement with treatment. CONCLUSION: Our quantitative method is a robust and promising tool that may allow investigators to quantify and document the potential adverse effect of background enhancement on diagnostic accuracy in larger populations.


Subject(s)
Breast/pathology , Carcinoma, Intraductal, Noninfiltrating/pathology , Magnetic Resonance Imaging/methods , Adult , Breast Neoplasms/diagnosis , Breast Neoplasms/pathology , Female , Humans , Image Processing, Computer-Assisted , Middle Aged , Receptors, Estrogen/metabolism , Reproducibility of Results , Tamoxifen/pharmacology
2.
Osteoarthritis Cartilage ; 14(1): 63-70, 2006 Jan.
Article in English | MEDLINE | ID: mdl-16188466

ABSTRACT

OBJECTIVE: To use receiver operator characteristics (ROC) analysis for assessing the diagnostic performance of three cartilage-specific MR sequences at 1.5 and 3 T in detecting cartilage lesions created in porcine knees. DESIGN: Eighty-four cartilage lesions were created in 27 porcine knee specimens at the patella, the medial and lateral femoral and the medial and lateral tibial cartilage. MR imaging was performed using a fat saturated spoiled gradient echo (SPGR) sequence (in plane spatial resolution/slice thickness: 0.20 x 0.39 mm2/1.5 mm) and two fat saturated proton density weighted (PDw) sequences (low spatial resolution: 0.31 x 0.47 mm2/3 mm and high spatial resolution: 0.20 x 0.26 mm2/2 mm). The images were independently analyzed by three radiologists concerning the absence or presence of lesions using a five-level confidence scale. Significances of the differences for the individual sequences were calculated based on comparisons of areas under ROC curves (A(Z)). RESULTS: The highest A(Z)-values for all three radiologists were consistently obtained for the SPGR (A(Z) = 0.84) and the high-resolution (hr) PDw (A(Z) = 0.79) sequences at 3T. The corresponding A(Z)-values at 1.5 T were 0.77 and 0.69; the differences between 1.5 and 3 T were statistically significant (P < 0.05). A(Z)-values for the low-resolution PDw sequence were lower: 0.59 at 3 T and 0.55 at 1.5 T and the differences between 1.5 and 3T were not significant. CONCLUSION: With optimized hr MR sequences diagnostic performance in detecting cartilage lesions was improved at 3 T. For a standard, lower spatial resolution PDw sequence no significant differences, however, were found.


Subject(s)
Cartilage Diseases/pathology , Cartilage, Articular/pathology , Magnetic Resonance Imaging/methods , ROC Curve , Animals , Disease Models, Animal , Femur , Hindlimb , Joints/pathology , Patella , Reproducibility of Results , Swine , Tibia
3.
Osteoporos Int ; 16(11): 1307-14, 2005 Nov.
Article in English | MEDLINE | ID: mdl-15999292

ABSTRACT

Previously, high resolution MRI to assess bone structure of deep-seated regions of the skeleton such as the proximal femur was substantially limited by signal-to-noise ratio (SNR). With the advent of new optimized pulse sequences in MRI at 1.5 T and 3 T, it may now be possible to depict and quantify the trabecular microarchitecture in the proximal femur. The purpose of this study was to investigate the feasibility of assessing trabecular microstructure of the human proximal femur in vivo with MR imaging at 1.5 T and 3 T. MR images of six young, healthy male and female subjects were acquired using standard clinical 1.5-T and high-field 3-T whole-body MR scanners. Using a T2/T1-weighted 3D FIESTA sequence (and a 3D FIESTA-C sequence at 3 T to avoid susceptibility artifacts) a resolution of 0.234 x 0.234 x 1.5 mm(3) was achieved in vivo. Structural parameters analogous to standard bone histomorphometry were determined in femoral head and trochanter regions of interest. Bone mineral density (BMD) measurements were also obtained using dual-energy X-ray absorptiometry (DXA) for the femoral trochanter in the same subjects. The bone structure of the proximal femur is substantially better depicted at 3 T than at 1.5 T. Correlation between the structural parameters obtained at both field strengths was up to R =0.86 for both the femoral head and the trochanteric region. However, the resolution of the images limits the application of 3D structural analysis, making the assessment more akin to 2D textural measures, which may be correlated to histomorphometric but are not identical measures. This feasibility study establishes the potential of MRI as a means of imaging proximal femur structure, and improvements in technique and resolution enhancements are warranted.


Subject(s)
Femur/anatomy & histology , Image Interpretation, Computer-Assisted , Magnetic Resonance Imaging/methods , Adult , Bone Density , Feasibility Studies , Female , Humans , Male , Osteoporosis/diagnosis , Reproducibility of Results , Sensitivity and Specificity
4.
Calcif Tissue Int ; 76(5): 355-64, 2005 May.
Article in English | MEDLINE | ID: mdl-15868282

ABSTRACT

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 (microCT), 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. High-resolution 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 microCT 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 microCT 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 microT, 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, r2 = 0.82; App. Tb.Sp, r2 = 0.84; App. Tb.N, r2 = 0.81), except for App.Tb.Th (r2 = 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 microCT.


Subject(s)
Femur Head/pathology , Magnetic Resonance Imaging/methods , Tomography, X-Ray Computed/methods , Aged , Calibration , Humans , Image Processing, Computer-Assisted , Magnetic Resonance Imaging/standards , Male , Miniaturization , Reference Standards , Tomography, X-Ray Computed/standards
5.
Invest Radiol ; 38(5): 269-80, 2003 May.
Article in English | MEDLINE | ID: mdl-12750616

ABSTRACT

RATIONALE AND OBJECTIVES: A novel, nonlinear morphologic measure [DeltaP(alpha)] based on local 3D scaling properties was applied to high-resolution magnetic resonance images (HR-MRI) of human trabecular bone to predict biomechanical strength in vitro. METHODS: We extracted DeltaP(alpha) and traditional morphologic parameters (apparent trabecular volume fraction, apparent trabecular separation) from HR-MR images of 32 femoral and 13 spinal bone specimens. Furthermore, bone mineral density (BMD) and maximum compressive strength (MCS) were determined. The morphologic measures were compared with BMD in predicting the biomechanical strength. RESULTS: In the vertebral (femoral) specimens, R2 for MCS versus DeltaP(alpha) was 0.87 (0.61) (P < 0.001). Correlation between BMD and MCS was 0.53 (P = 0.05) (0.79 [P < 0.001]) for the vertebral (femoral) specimens. For the femoral specimens, prediction of MCS could be improved further by combining BMD and morphologic parameters by multiple regression (R2 = 0.88). CONCLUSIONS: Morphologic measures extracted from HR-MRI considering local 3D-scaling properties can be used to predict biomechanical properties of bone in vitro. They are superior to 2-dimensional standard linear morphometric measures and, depending on the anatomic location, more reliably predict bone strength as measured by MCS than does BMD.


Subject(s)
Femur/physiopathology , Magnetic Resonance Imaging/methods , Spine/physiopathology , Adult , Aged , Biomechanical Phenomena , Bone Density , Cadaver , Humans , Image Processing, Computer-Assisted , Imaging, Three-Dimensional , In Vitro Techniques , Middle Aged , Regression Analysis , Reproducibility of Results , Stress, Mechanical
6.
Calcif Tissue Int ; 72(2): 156-65, 2003 Feb.
Article in English | MEDLINE | ID: mdl-12370799

ABSTRACT

The purpose of this study was to use high resolution magnetic resonance imaging (HR-MRI) combined with structure analysis to investigate the trabecular structure of the human proximal femur and to compare this technique with bone mineral density (BMD) using dual energy X-ray absorptiometry (DXA) in the prediction of bone strength in vitro. Thirty-one fresh human proximal femur specimens were examined with HR-MRI using a T1-weighted 3D spinecho-sequence in a coronal plane (voxel size: 0.195 x 0.195 x 0.9 mm and 0.195 x 0.195 x 0.3 mm). In these images structure parameters analogous to standard bone histomorphometry were obtained in a femoral head, neck, and trochanteric region of interest (ROI). In addition, BMD measurements were obtained using DXA and finally, all specimens were tested biomechanically in a materials testing machine, and maximum compressive strength (MCS) was determined. Correlations between BMD and MCS were significant (p <0.01) with R-values up to 0.74. Correlating structure parameters and MCS R-values up to 0.69 (P <0.01) were obtained. Using multivariate regression analysis, combining structure parameters and BMD, improved correlations versus MCS substantially (up to R = 0.93; P <0.01). In conclusion, this study showed that in an experimental setting, structure parameters determined in high resolution MR images of the proximal femur correlated significantly with bone strength. The highest correlations, however, were obtained combining BMD and structure measures.


Subject(s)
Femur/anatomy & histology , Magnetic Resonance Imaging/methods , Aged , Bone Density , Bone and Bones/anatomy & histology , Bone and Bones/diagnostic imaging , Compressive Strength , Female , Femur/diagnostic imaging , Femur/physiology , Humans , Male , Radiography , White People
7.
Osteoporos Int ; 13(4): 278-87, 2002.
Article in English | MEDLINE | ID: mdl-12030542

ABSTRACT

The authors have developed a system for the characterization of trabecular bone structure from high-resolution MR images. It features largely automated coil inhomogeneity correction, trabecular bone region segmentation, serial image registration, bone/marrow binarization, and structural calculation steps. The system addresses problems of efficiency and inter- and intraoperator variability inherent in previous analyses. The system is evaluated on repetitive scans of 8 volunteers for both two-dimensional (2D) apparent structure calculations and three-dimensional (3D) mechanical calculations using micro-finite element analysis. Coil correction methods based on a priori knowledge of the coil sensitivity and on low-pass filtering of the high-resolution mages are compared and found to perform similarly. Image alignment is found to cause small but significant changes in some structural parameters. Overall the automated system provides on the order of a 3-fold decrease in trained operator time over previous manual methods. Reproducibility is found to be dependent on image quality for most parameters. For 7 subjects with good image quality, reproducibility of 2-4% is found for 2D structural parameters, while 3D mechanical parameters vary by 4-9%, with percent standardized coefficients of variation in the ranges of 15-34% and 20-38% respectively.


Subject(s)
Bone Density , Bone and Bones/physiopathology , Magnetic Resonance Imaging/methods , Osteoporosis/diagnosis , Adult , Biomechanical Phenomena , Female , Finite Element Analysis , Humans , Longitudinal Studies , Male , Middle Aged , Reproducibility of Results
8.
Osteoporos Int ; 13(1): 6-17, 2002 Jan.
Article in English | MEDLINE | ID: mdl-11878456

ABSTRACT

Measurement of microstructural parameters of trabecular bone noninvasively in vivo is possible with high-resolution magnetic resonance (MR) imaging. These measurements may prove useful in the determination of bone strength and fracture risk, but must be related to other measures of bone properties. In this study in vivo MR imaging was used to derive trabecular bone structure measures and combined with micro-finite element analysis (microFE) to determine the effects of trabecular bone microarchitecture on bone mechanical properties in the distal radius. The subjects were studied in two groups: (I) postmenopausal women with normal bone mineral density (BMD) (n = 22, mean age 58 +/- 7 years) and (II) postmenopausal women with spine or femur BMD -1 SD to -2.5 SD below young normal (n = 37, mean age 62 +/- 11 years). MR images of the distal radius were obtained at 1.5 T, and measures such as apparent trabecular bone volume fraction (App BV/TV), spacing, number and thickness (App TbSp, TbN, TbTh) were derived in regions of interest extending from the joint line to the radial shaft. The high-resolution images were also used in a micro-finite element model to derive the directional Young's moduli (E1, E2 and E3), shear moduli (G12, G23 and G13) and anisotropy ratios such as E1/E3. BMD at the distal radius, lumbar spine and hip were assessed using dual-energy X-ray absorptiometry (DXA). Bone formation was assessed by serum osteocalcin and bone resorption by serum type I collagen C-terminal telopeptide breakdown products (serum CTX) and urinary CTX biochemical markers. The trabecular architecture displayed considerable anisotropy. Measures of BMD such as the ultradistal radial BMD were lower in the osteopenic group (p<0.01). Biochemical markers between the two groups were comparable in value and showed no significant difference between the two groups. App BV/TV, TbTh and TbN were higher, and App TbSp lower, in the normal group than the osteopenic group. All three directional measures of elastic and shear moduli were lower in the osteopenic group compared with the normal group. Anisotropy of trabecular bone microarchitecture, as measured by the ratios of the mean intercept length (MIL) values (MIL1/MIL3, etc.), and the anisotropy in elastic modulus (E1/E3, etc.), were greater in the osteopenic group compared with the normal group. The correlations between the measures of architecture and moduli are higher than those between elastic moduli and BMD. Stepwise multiple regression analysis showed that while App BV/TV is highly correlated with the mechanical properties, additional structural measures do contribute to the improved prediction of the mechanical measures. This study demonstrates the feasibility and potential of using MR imaging with microFE modeling in vivo in the study of osteoporosis.


Subject(s)
Bone Density , Osteoporosis, Postmenopausal/pathology , Radius/pathology , Aged , Anisotropy , Biomarkers/analysis , Biomechanical Phenomena , Bone Remodeling , Feasibility Studies , Female , Finite Element Analysis , Hip Joint/physiopathology , Humans , Image Processing, Computer-Assisted , Lumbar Vertebrae/physiopathology , Magnetic Resonance Imaging , Middle Aged , Osteoporosis, Postmenopausal/physiopathology , Radius/physiopathology
9.
Osteoporos Int ; 13(2): 119-29, 2002.
Article in English | MEDLINE | ID: mdl-11905522

ABSTRACT

The purpose of this study was to use high-resolution magnetic resonance (HR-MR) imaging to analyze the trabecular bone structure of the calcaneus in patients before and after renal transplantation and to compare this technique with bone mineral density (BMD) in predicting therapy-induced bone loss and osteoporotic fracture status. HR-MR imaging (voxel size: 0.195 x 0.195 x 1 mm) was performed at 1.5 T with an axial and sagittal orientation in 48 patients after transplantation, 12 patients before renal transplantation and 20 healthy controls. Structure measures analogous to standard histomorphometry and fractal dimension were determined in these images. BMD measurements of the lumbar spine and the proximal femur were obtained in the healthy female controls and the patients. Vertebral and peripheral fracture status were determined in all patients. The structural measures app.BV/TV, Tb.Sp, Tb.Th and Tb.N showed significant differences between controls and patients (p<0.05) while fractal dimension showed no significant differences. Neither the structural measures nor BMD showed significant differences between patients before and after transplantation. Correlations between time after transplantation versus structural measures and BMD were not significant. Differences between fracture and nonfracture patients were significant for the structural measures app.BV/TV, Tb.Sp and Tb.N (axial images) as well as for app.Tb.Th (sagittal images) and spine BMD (p<0.05) but not for hip BMD. Using odds ratios the strongest discriminators between patients with and without fractures were app. BV/TV, app.Tb.Sp (axial images) and app.Tb.Th (sagittal images), even after adjustment for age and BMD. Using receiver operating characteristic analysis the highest diagnostic performance was found for a combination of BMD and structural measures. In conclusion, our results indicate that structural measures obtained from HR-MR images may be used to characterize fracture incidence in kidney transplant patients; the best results, however, are obtained using a combination of BMD and structural measures.


Subject(s)
Calcaneus/pathology , Fractures, Bone/diagnosis , Kidney Transplantation/adverse effects , Magnetic Resonance Imaging , Osteoporosis/diagnosis , Adult , Aged , Bone Density , Calcaneus/physiopathology , Female , Femur/physiopathology , Fractures, Bone/etiology , Fractures, Bone/physiopathology , Humans , Image Processing, Computer-Assisted , Immunosuppressive Agents/adverse effects , Lumbar Vertebrae/physiopathology , Male , Middle Aged , Odds Ratio , Osteoporosis/etiology , Osteoporosis/physiopathology , Postoperative Period , ROC Curve
10.
Osteoporos Int ; 13(2): 130-6, 2002.
Article in English | MEDLINE | ID: mdl-11905523

ABSTRACT

Complementing measurements of bone mass with measurements of the architectural status of trabecular bone is expected to improve predictions of fracture risk in osteoporotic patients and improve the assessment of response to drug therapy. With high-resolution MRI the trabecular network can be imaged with 156 x 156 x 500 microm3 voxels, sufficient to depict individual trabeculae, albeit with inaccurate thickness. In this work, distance transformation techniques were applied to the three-dimensional image of the distal radius of postmenopausal patients. Structural indices such as trabecular number (app.Tb.N), thickness (app.Tb.Th) and separation (app.Tb.Sp) were determined without model assumptions. A new metric index, the apparent intra-individual distribution of separations (app.Tb.Sp.SD), is introduced. The reproducibility of the MR procedure and structure assessment was determined on volunteers, and the coefficient of variation was found to be 2.7-4.6% for the mean values of structural indices and 7.7% for app.Tb.Sp.SD. The distance transformation methods were then applied to two groups of patients: one of postmenopausal women without vertebral fracture and one of postmenopausal women with at least one vertebral fracture. It was found that app.Tb.Sp.SD discriminates fracture subjects from non-fracture patients as well as dual-energy X-ray absorptiometry (DXA) measurements of the radius and the spine, but not as well as DXA of the hip. Using receiver operating characteristic analysis, the area under the curve (AUC) values were 0.67 for app.Tb.Sp.SD, 0.72 for DXA radius, 0.67 for DXA spine and 0.81 for DXA of the hip. A combination of MR indices reached an AUC of 0.75. Age-adjusted odds ratio ranged from 1.85 to 2.03 for app.Tb.N, app.Tb.Sp and app.Tb.Sp.SD (p<0.003). We conclude that in vivo high-resolution MRI not only has the potential of imaging trabecular bone, but in combination with novel metrics may offer new insight into the structural changes occurring in postmenopausal women.


Subject(s)
Magnetic Resonance Imaging/methods , Osteoporosis, Postmenopausal/pathology , Spinal Fractures/pathology , Absorptiometry, Photon , Adult , Bone Density , Feasibility Studies , Female , Humans , Image Processing, Computer-Assisted , Logistic Models , Middle Aged , Odds Ratio , Osteoporosis, Postmenopausal/complications , Osteoporosis, Postmenopausal/physiopathology , ROC Curve , Radius/pathology , Radius/physiopathology , Reproducibility of Results , Spinal Fractures/etiology , Spinal Fractures/physiopathology
11.
Clin Biomech (Bristol, Avon) ; 17(2): 81-8, 2002 Feb.
Article in English | MEDLINE | ID: mdl-11832257

ABSTRACT

OBJECTIVE: To investigate whether recently developed in vivo high-resolution magnetic resonance-imaging and micro-finite element techniques can monitor changes in bone mechanical properties during long-term clinical trials aiming at evaluating the efficacy of new drugs for the treatment of osteoporosis. DESIGN: Comparison of baseline and follow-up mechanical parameters calculated using micro-finite element analysis of the calcaneus for subjects participating in a study investigating the effect of idoxifene. BACKGROUND: Contemporary measurements for the evaluation of bone mechanical properties, based on dual-energy X-ray absorptiometry measurements, are not very accurate and require large trial populations. METHODS: A total of 56 postmenopausal subjects received either a placebo, 5 mg or 10 mg per day of idoxifene. Magnetic resonance-images of the calcaneus were made at baseline and after one year. Mechanical parameters of a trabecular volume of interest in the calcaneus were calculated using micro-finite element analysis. RESULTS: Although there were no significant differences between the mean changes in the treated groups and the placebo group, there were significant changes from baseline within groups after one year of treatment. Significant changes, however, were found only for mechanical parameters and only in the treated groups. CONCLUSIONS: The present study is the first demonstration that longitudinal changes in bone mechanical properties due to trabecular micro-architectural changes may be quantified in long-term clinical studies. Since significant changes in mechanical parameters were obtained for the treated groups whereas no significant change in bone mass was found we conclude that the application of these techniques may increase the clinical significance of these trials. RELEVANCE: A precise diagnosis of in vivo bone mechanical properties that accounts for (changes in) trabecular bone architecture is of particular importance for longitudinal clinical trials aiming at evaluating the efficacy of new drugs since it can lead to clinically relevant results from shorter follow-up intervals and may enable a reduction of the number of patients involved in the trial.


Subject(s)
Bone Density/drug effects , Calcaneus/physiology , Estrogen Antagonists/pharmacology , Finite Element Analysis , Magnetic Resonance Imaging , Tamoxifen/analogs & derivatives , Tamoxifen/pharmacology , Female , Humans , Image Processing, Computer-Assisted , Middle Aged , Postmenopause/physiology , Randomized Controlled Trials as Topic
12.
Magn Reson Imaging ; 20(10): 733-41, 2002 Dec.
Article in English | MEDLINE | ID: mdl-12591569

ABSTRACT

An accurate measurement of the transverse relaxation time T(2), and the histogram of T(2) in the brain parenchyma can be accomplished in vivo using a multi-echo magnetic resonance imaging sequence. An estimate of the error in the T(2) measurement is derived using copper sulfate doped water phantoms. Correction factors are calculated and applied to the signal intensity of each voxel prior to the in vivo T(2) evaluation. These corrected T(2) are in good agreement with the theoretical values calculated from copper sulfate concentrations. This technique is then applied to calculate T(2) histograms of the brain. The population studied was composed of normal volunteers and multiple sclerosis patients. The corrected T(2) histogram method discriminates the normal control population from the MS population, and also discriminates between relapsing-remitting patients and primary progressive or secondary progressive patients. Moreover using this approach we are able to detect in MS patients a global shift of the T(2) of the white mater toward higher values. The results of this study showed that the method is easy to implement and may be used to characterize MS pathology.


Subject(s)
Brain/pathology , Magnetic Resonance Imaging , Multiple Sclerosis/diagnosis , Female , Humans , Male , Multiple Sclerosis/pathology , Multiple Sclerosis, Chronic Progressive/diagnosis , Multiple Sclerosis, Chronic Progressive/pathology , Multiple Sclerosis, Relapsing-Remitting/diagnosis , Multiple Sclerosis, Relapsing-Remitting/pathology , Phantoms, Imaging
13.
Spine (Phila Pa 1976) ; 26(19): E437-44, 2001 Oct 01.
Article in English | MEDLINE | ID: mdl-11698903

ABSTRACT

STUDY DESIGN: Twelve lumbar intervertebral disc specimens were imaged with magnetic resonance imaging to estimate relaxation constants, T1 and T2, and tissue water diffusion, before and after applying compression. OBJECTIVES: The objectives of the study were to measure T1, T2, and water diffusion for differences with loading state, region of the disc (anulus fibrosus or nucleus pulposus), and grade of degeneration. SUMMARY OF BACKGROUND DATA: Magnetic resonance imaging can be used qualitatively to estimate water content and degeneration of the intervertebral disc. Beyond structural information of images, the relaxation times T1 and T2 may contain information on the changes occurring with degeneration. A modified spin-echo sequence can be used to estimate tissue water diffusion in cartilage and disc specimens with the ability to measure anisotropy. METHODS: Specimens were imaged in a 1.5-Tesla clinical scanner. T1, T2, and water diffusion were estimated from midsagittal images. Magnetic resonance imaging parameters were calculated before and after axial loading. The measured T1, T2, and D (diffusion coefficient) were compared before and after compression, and for the diffusion data, also by direction to consider anisotropy. RESULTS: For the T1 data, a significant difference was found by region, nucleus > anulus, and loading state, loaded > unloaded. For the T2 values, there was a significant difference by region, nucleus > anulus, and Thompson grade. For diffusion, significant differences were found by region, nucleus > anulus, Thompson grade, direction of diffusion, and state of compression, loaded > unloaded. CONCLUSIONS: This study demonstrated that magnetic resonance imaging can be used to measure significant changes in T1, T2, or diffusion in intervertebral disc specimens by region, loading condition, or Thompson grade.


Subject(s)
Body Water/metabolism , Intervertebral Disc/metabolism , Lumbar Vertebrae , Magnetic Resonance Imaging/methods , Weight-Bearing/physiology , Adolescent , Adult , Aged , Diffusion , Female , Humans , In Vitro Techniques , Intervertebral Disc/physiopathology , Intervertebral Disc Displacement/metabolism , Intervertebral Disc Displacement/physiopathology , Male , Middle Aged
14.
J Bone Miner Res ; 16(8): 1511-9, 2001 Aug.
Article in English | MEDLINE | ID: mdl-11499874

ABSTRACT

The purpose of this study was to use quantitative magnetic resonance imaging (MRI; high-resolution [HR] and relaxometry) to assess trabecular bone structure in lumbar vertebrae specimens and to compare these techniques with bone mineral density (BMD) in predicting stress values obtained from mechanical tests. Fourteen vertebral midsagittal sections from lumbar vertebrae L3 were obtained from cadavers (aged 22-76 years). HR images with a slice thickness of 300 microm and an in-plane spatial resolution of 117 microm2 x 117 microm2 were obtained. Transverse relaxation time T2' distribution was measured by using an asymmetric spin-echo (ASE) sequence. Traditional morphometric measures of bone structure such as apparent trabecular bone fraction (app. BV/TV), apparent trabecular bone number (app. Tb.N), apparent trabecular bone separation (app. Tb.Sp), and apparent trabecular bone thickness (app. Tb.Th) as well as the directional mean intercept length (MIL) were calculated. Additionally, BMD measurements of these sections were obtained by dual-energy X-ray absorptiometry (DXA) and biomechanical properties such as directional stress values (to fracture) were determined on adjacent specimens. With the exception of T2', all morphological parameters correlated very well with age, BMD, and stress values (R between 0.79 and 0.92). However, in the direction perpendicular to the magnetic field, T2' values enhanced the adjusted R2 correlation value with horizontal (M/L) stress values in addition to BMD from 0.70 to 0.91 (p < 0.05).


Subject(s)
Lumbar Vertebrae/pathology , Adult , Aged , Bone Density , Female , Humans , Lumbar Vertebrae/physiopathology , Magnetic Resonance Imaging/methods , Male , Middle Aged
15.
Invest Radiol ; 36(4): 210-7, 2001 Apr.
Article in English | MEDLINE | ID: mdl-11283418

ABSTRACT

RATIONALE AND OBJECTIVES: The purpose of this study was to compare trabecular bone structure parameters assessed with high-resolution magnetic resonance imaging (HR-MRI) with those determined in specimen sections. METHODS: High-resolution MR images were obtained for 30 calcaneus specimens with a three-dimensional, T1-weighted spin-echo sequence (spatial in-plane resolution 0.195 mm, slice thicknesses of 0.3 and 0.9 mm). Thirty-eight sections were obtained from the specimens, and contact radiography was performed. In the corresponding sections, structural parameters analogous to bone histomorphometry were determined. RESULTS: Significant correlations between MRI-derived structural parameters and those derived from macro pathological sections were found: r values of up to 0.75 were obtained (P < 0.01). The highest correlations were found for apparent bone volume/total volume and trabecular thickness. Image thresholding techniques showed a significant impact on these correlations (P < 0.01). The thinner MR sections were less susceptible to the different thresholding algorithms. CONCLUSIONS: Trabecular bone structure depicted by HR-MR images is significantly correlated with that shown in macro sections (P < 0.01); however, a number of limitations have to be considered, including the substantial impact of thresholding techniques and slice thickness.


Subject(s)
Calcaneus/anatomy & histology , Magnetic Resonance Imaging , Aged , Aged, 80 and over , Humans , Middle Aged , Reference Values
18.
Med Phys ; 27(11): 2594-9, 2000 Nov.
Article in English | MEDLINE | ID: mdl-11128312

ABSTRACT

Our purpose in this study was (i) to measure trabecular bone structure using fractal analysis of distal radius radiographs in subjects with and without osteoporotic hip fractures, and (ii) to compare these measures with bone mineral density (BMD) as well as with measures of trabecular bone structure derived from high resolution magnetic resonance (MR) images. Distal radius radiographs were obtained using semi-industrial films (55 kVp, 400 mAs) in 30 postmenopausal patients, who had suffered osteoporotic hip fractures (74.8+/-8.2 years) in the last 24 months and 27 postmenopausal age-matched (74.6+/-6.6 yr) normal volunteers. Radiographs were digitized at 50 microm. A Fourier power spectrum-based fractal dimension (FD) characterizing the trabecular pattern was measured in a region of interest proximal to the joint line. The fractal dimension was calculated over two spatial frequency (f) ranges: FD1 was calculated over 0.5

Subject(s)
Bone and Bones/diagnostic imaging , Fractals , Aged , Bone Density , Case-Control Studies , Female , Femur/diagnostic imaging , Hip/diagnostic imaging , Humans , Magnetic Resonance Imaging , Middle Aged , Models, Statistical , Osteoporosis/diagnostic imaging , Postmenopause , ROC Curve , Radiography
19.
Radiology ; 217(3): 855-62, 2000 Dec.
Article in English | MEDLINE | ID: mdl-11110954

ABSTRACT

PURPOSE: To use high-spatial-resolution magnetic resonance (MR) imaging to analyze the trabecular bone structure of the calcaneus in patients before and after heart transplantation and to compare this technique with bone mineral density (BMD) measurement in predicting therapy-induced bone loss and vertebral fracture status. MATERIALS AND METHODS: High-spatial-resolution 1.5-T MR imaging of the calcaneus was performed in 40 men 11-120 months after heart transplantation, in 11 men before heart transplantation, and in 10 age-matched male volunteers. Sagittal and transverse T1-weighted spin-echo images with a voxel size of 0.195 x 0.195 x 1.000 mm were obtained, and structure measurements analogous to bone histomorphometric values were calculated. In addition, the BMD of the lumbar spine was determined in the transplant recipients pre- and postoperatively by using quantitative computed tomography, and vertebral fracture status was assessed. RESULTS: Significant differences in structure and BMD measurements were found between patients before and after heart transplantation (P <. 05). In 17 (42%) of 40 transplant recipients, vertebral fractures were found. Although structure measurements were significantly different between patients with and those without fractures (P <.05), BMDs were not. Correlations between time after transplantation and some structure measurements were moderately significant (P <. 05), but such correlations with BMD measurements were not. CONCLUSION: MR imaging-derived structure measurements in the calcaneus are useful for monitoring bone changes after heart transplantation and assessing vertebral fracture status.


Subject(s)
Bone Density/physiology , Bone and Bones/physiology , Heart Transplantation/physiology , Magnetic Resonance Imaging/methods , Adult , Calcaneus/physiology , Case-Control Studies , Humans , Male , Middle Aged , Spinal Fractures/diagnosis , Spinal Fractures/physiopathology
20.
Bone ; 27(2): 319-26, 2000 Aug.
Article in English | MEDLINE | ID: mdl-10913929

ABSTRACT

This cross-sectional study is based on images from the lower leg as assessed by peripheral quantitative computer tomography (pQCT). Measurements were performed in 39 female and 38 male control subjects and 15 female professional volleyball players, all between 18 and 30 years of age. The images were obtained at shank levels of 4%, 14%, 33%, and 66% from the distal end. Bone and muscle cross-sectional areas, and the bones' density-weighted area moment of resistance and of inertia were assessed. From these, muscle-bone strength indices (MBSIs) were developed for compression (CI = 100. bone area/muscle area) and bending (BI = 100. bone area moment of resistance/muscle area/tibia length). Significant correlations between muscle cross-sectional area and bone were found at all section levels investigated. The strongest correlation for compression was observed in the sections at 14% (correlation coefficient r = 0.74), where 4.10 +/- 0.46 cm(2) bone, on average, was related to 100 cm(2) muscle. The compression index (CI) at the 14% level was independent of the tibia length. Interestingly, the 15 athletes had significantly greater CIs than the control subjects. This is most probably due to the greater tension development in the athletes. The highest correlation for bending was for anteroposterior bending at 33% of tibia length (r = 0.81), where the area moment of resistance, R, was on, average, 4.21 +/- 0.54 cm(3)/100 cm(2) muscle/m tibia length. Analysis of the bones' area moment of inertia showed that buckling is a possible cause of bending at the 33% and 66% levels, but not at the 14% level. No gender differences in MBSI were found. Likewise, age was without significant effect. The data show that bone architecture depends critically on muscle cross section and tension development. Moreover, bone geometry (e.g., the tibia length) influences the geometrical distribution of bone mineral, as it was found that long bones adapted to the same compressive strength are wider than short ones. We conclude that MBSIs offer a powerful diagnostic tool for bone disorders and may contribute to improving the treatment of bone metabolic and other diseases.


Subject(s)
Leg/physiology , Muscle, Skeletal/physiology , Tibia/physiology , Absorptiometry, Photon , Adult , Anthropometry , Compressive Strength , Female , Humans , Male , Muscle, Skeletal/anatomy & histology , Osteoporosis/pathology , Osteoporosis/physiopathology , Sex Factors , Sports , Tibia/anatomy & histology , Tibia/diagnostic imaging
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