Quadriceps muscle quality and quantity following tibial plateau fracture repair.

PURPOSE: To investigate the qualitative and quantitative changes seen in quadriceps muscles [QM] following tibial plateau fracture and surgery. METHODS: A consecutive series of patients with an isolated tibial plateau fracture presenting to a single academic center were enrolled and prospectively followed. Bilateral knee MRIs were performed preoperatively and 3 and 12 months postoperatively to assess quantity and quality of the quadriceps muscles. All patients underwent tibial plateau operative repair and were made non-weight-bearing for 10 weeks postoperatively then advanced to weight-bearing as tolerated. Functional status assessed via the short musculoskeletal functional assessment (SMFA); knee range of motion [ROM]; vastus medialis oblique [VMO] and vastus lateralis [VL] muscle quantity (axial width, cross sectional area [CSA] and volume) on injured and contralateral limb; VMO, sartorius, semi-membranous and biceps femoris [BF] muscle quality (fat and water content, and proton density fat fraction). All muscle quantitative and qualitative measurements were compared across all time points. RESULTS: Ten patients were included in the final analysis, 6 males and 4 females, with average age of 43.62 ± 16.3 years. While the VMO and VL axial width and CSA were significantly decreased at 3 months preoperatively, this was not statistically significant. There was no significant difference between any QM quantitative measurements at any time points. There was no difference in fat content, water content or PDFF at any time point for the VMO, sartorius, semi-membranous and BF muscles. Regression analysis also showed no association between 12-month SMFA scores and knee ROM with VMO/VL CSA at 1 year. CONCLUSIONS: QM quantity and quality do not significantly change at 3 months and 1 year postoperatively following tibial plateau fracture surgery. LEVEL OF EVIDENCE: Prognostic Level II.

Fatty Acid Composition of Proximal Femur Bone Marrow Adipose Tissue in Subjects With Systemic Lupus Erythematous Using 3 T Magnetic Resonance Spectroscopy.

BACKGROUND: Systemic lupus erythematosus (SLE) is a chronic, inflammatory disease with common musculoskeletal manifestations, notably reductions in bone quality. Bone marrow adipose tissue composition and quantity has been previously linked to bone quality and may play a role in SLE pathophysiology but has not been thoroughly studied. PURPOSE: To use magnetic resonance spectroscopy (MRS) to investigate bone marrow adipose tissue quantity and composition in proximal femur subregions of untreated SLE patients compared to controls and treated patients. STUDY TYPE: Prospective. SUBJECTS: A total of 64 female subjects: 28 SLE, 15 glucocorticoid (GC)-treated SLE and 21 matched controls. FIELD STRENGTH/SEQUENCE: Stimulated echo acquisition mode (STEAM) sequence at 3 T. ASSESSMENT: MRS was performed at multiple echo times in the femoral neck and trochanter regions and fatty acids (FA) composition was computed. STATISTICAL TESTS: Intergroup comparisons were carried out using ANOVA. A P value < 0.05 was considered statistically significant. RESULTS: SLE patients had significantly higher saturated FA compared to controls in both the femoral neck (+0.12) and trochanter (+0.11), significantly lower monounsaturated FA in the trochanter compared to controls (-0.05), and significantly lower polyunsaturated FA in the femoral neck compared to both controls (-0.07) and SLE patients on GC therapy (-0.05). DATA CONCLUSION: SLE patients have altered proximal femur marrow fat metabolism, which may reflect a manifestation of, or play a role in, the altered inflammatory response of these patients. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 2.

3T chemical shift-encoded MRI: Detection of altered proximal femur marrow adipose tissue composition in glucocorticoid users and validation with magnetic resonance spectroscopy.

BACKGROUND: Osteoporosis (OP) results in weak bone and can ultimately lead to fracture. Drugs such as glucocorticoids can also induce OP (glucocorticoid-induced osteoporosis [GIO]). Bone marrow adipose tissue composition and quantity may play a role in OP pathophysiology, but has not been thoroughly studied in GIO compared to primary OP. PURPOSE/HYPOTHESIS: Chemical shift-encoded (CSE) MRI allows detection of subregional differences in bone marrow adipose tissue composition and quantity in the proximal femur of GIO compared to OP subjects and has high agreement with the reference standard of magnetic resonance spectroscopy (MRS). STUDY TYPE: Prospective. SUBJECTS: In all, 18 OP and 13 GIO subjects. FIELDS STRENGTH: 3T. SEQUENCE: Multiple gradient-echo, stimulated echo acquisition mode (STEAM). ASSESSMENT: Subjects underwent CSE-MRI in the proximal femurs, and for each parametric map regions of interest (ROIs) were assessed in the femoral head (fHEAD), femoral neck (fNECK), Ward's triangle (fTRIANGLE), and the greater trochanter (GTROCH). In addition, we compared CSE-MRI against the reference standard of MRS performed in the femoral neck and Ward's triangle. STATISTICAL TESTS: Differences between OP/GIO were investigated using the Mann-Whitney nonparametric test. Bland-Altman methodology was used to assess measurement agreement between CSE-MRI and MRS. RESULTS: GIO compared with OP subjects demonstrated: decreased monounsaturated fat fraction (MUFA) (-2.1%, P < 0.05) in fHEAD; decreased MUFA (-3.8%, P < 0.05), increased saturated fat fraction (SFA) (5.5%, P < 0.05), and decreased T2* (-3.8 msec, P < 0.05) in fNECK; decreased proton density fat fraction (PDFF) (-15.1%, P < 0.05), MUFA (-9.8%, P < 0.05), polyunsaturated fat fraction (PUFA) (-1.8%, P < 0.01), increased SFA (11.6%, P < 0.05), and decreased T2* (-5.4 msec, P < 0.05) in fTRIANGLE; and decreased T2* (-1.5 msec, P < 0.05) in GTROCH. There was high measurement agreement between MRI and MRS using the Bland-Altman test. DATA CONCLUSION: 3T CSE-MRI may allow reliable assessment of subregional bone marrow adipose tissue (bMAT) quantity and composition in the proximal femur in a clinically reasonable scan time. Glucocorticoids may alter the lipid profile of bMAT and potentially result in reduced bone quality. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:490-496.

MRI assessment of bone structure and microarchitecture.

Osteoporosis is a disease of weak bone and increased fracture risk caused by low bone mass and microarchitectural deterioration of bone tissue. The standard-of-care test used to diagnose osteoporosis, dual-energy x-ray absorptiometry (DXA) estimation of areal bone mineral density (BMD), has limitations as a tool to identify patients at risk for fracture and as a tool to monitor therapy response. Magnetic resonance imaging (MRI) assessment of bone structure and microarchitecture has been proposed as another method to assess bone quality and fracture risk in vivo. MRI is advantageous because it is noninvasive, does not require ionizing radiation, and can evaluate both cortical and trabecular bone. In this review article, we summarize and discuss research progress on MRI of bone structure and microarchitecture over the last decade, focusing on in vivo translational studies. Single-center, in vivo studies have provided some evidence for the added value of MRI as a biomarker of fracture risk or treatment response. Larger, prospective, multicenter studies are needed in the future to validate the results of these initial translational studies. LEVEL OF EVIDENCE: 5 Technical Efficacy: Stage 5 J. MAGN. RESON. IMAGING 2017;46:323-337.

Radiomic analysis of the proximal femur in osteoporosis women using 3T MRI.

Introduction: Osteoporosis (OP) results in weak bone and can ultimately lead to fracture. MRI assessment of bone structure and microarchitecture has been proposed as method to assess bone quality and fracture risk in vivo. Radiomics provides a framework to analyze the textural information of MR images. The purpose of this study was to analyze the radiomic features and its abilityto differentiate between subjects with and without prior fragility fracture. Methods: MRI acquisition was performed on n = 45 female OP subjects: 15 with fracture history (Fx) and 30 without fracture history (nFx) using a high-resolution 3D Fast Low Angle Shot (FLASH) sequence at 3T. Second and first order radiomic features were calculated in the trabecular region of the proximal femur on T1-weighted MRI signal of a matched dataset. Significance of the feature's predictive ability was measured using Wilcoxon test and Area Under the ROC (AUROC) curve analysis. The features were correlated DXA and FRAX score. Result: A set of three independent radiomic features (Dependence Non-Uniformity (DNU), Low Gray Level Emphasis (LGLE) and Kurtosis) showed significant ability to predict fragility fracture (AUROC DNU = 0.751, p < 0.05; AUROC LGLE = 0.729, p < 0.05; AUROC Kurtosis = 0.718, p < 0.05) with low to moderate correlation with FRAX and DXA. Conclusion: Radiomic features can measure bone health in MRI of proximal femur and has the potential to predict fracture.

Osteoporosis Imaging.

Osteoporosis is the most common disease affecting bones worldwide. Dual x-ray absorptiometry (DXA) is the current reference standard for assessing bone health and, combined with other clinical parameters, provides a good estimation of fracture risk. DXA-based Trabecular Bone Score (TBS) can provide complementary indirect information about bone microarchitecture, which also deteriorates osteoporosis. QCT can provide a 3-D volumetric assessment of bone mineral density (BMD), and FEA of computed tomography (CT) images of bone can provide estimates of bone strength, which have the potential to add value, beyond BMD, for fracture risk assessment. Magnetic resonance imaging (MRI) of bone microarchitecture is an additional promising alternative to the assessment of BMD, and there is evidence that microarchitectural parameters could 1 day have benefits for diagnosing osteoporosis beyond BMD and/or FRAX. Assessment of bone via MRI also provides insight into other bone tissue properties (cortical porosity, marrow fat) that are altered in osteoporosis and that DXA cannot assess. Overall, bone health cannot be characterized solely by one parameter. Current imaging techniques/modalities in combination with advanced image processing hold the potential to provide a comprehensive understanding of the pathologic changes that occur in bone tissue in the setting of osteoporosis and pave the way for new imaging methods to diagnose, monitor, and predict osteoporosis.

Analysis of muscle, hip, and subcutaneous fat in osteoporosis patients with varying degrees of fracture risk using 3T Chemical Shift Encoded MRI.

Osteoporosis (OP) is a major disease that affects 200 million people worldwide. Fatty acid metabolism plays an important role in bone health and plays an important role in bone quality and remodeling. Increased bone marrow fat quantity has been shown to be associated with a decrease in bone mineral density (BMD), which is used to predict fracture risk. Chemical-Shift Encoded magnetic resonance imaging (CSE-MRI) allows noninvasive and quantitative assessment of adipose tissues (AT). The aim of our study was to assess hip or proximal femoral bone marrow adipose tissue (BMAT), thigh muscle (MUS), and subcutaneous adipose tissue (SAT) in 128 OP subjects matched for age, BMD, weight and height with different degrees of fracture risk assessed through the FRAX score (low, moderate and high). Our results showed an increase in BMAT and in MUS in high compared to low fracture risk patients. We also assessed the relationship between fracture risk as assessed by FRAX and AT quantities. Overall, the results of this study suggest that assessment of adipose tissue via 3T CSE-MRI provides insight into the pathophysiology fracture risk by showing differences in the bone marrow and muscle fat content in subjects with similarly osteoporotic BMD as assessed by DXA, but with varying degrees of fracture risk as assessed by FRAX.

Chemical shift-encoded MRI for assessment of bone marrow adipose tissue fat composition: Pilot study in premenopausal versus postmenopausal women.

OBJECT: To quantify and compare subregional proximal femur bone marrow fat composition in premenopausal and postmenopausal women using chemical shift-encoded-MRI (CSE-MRI). MATERIALS AND METHODS: A multi gradient-echo sequence at 3 T was used to scan both hips of premenopausal (n = 9) and postmenopausal (n = 18) women. Subregional fat composition (saturation, poly-unsaturation, mono-unsaturation) was quantitatively assessed in the femoral head, femoral neck, Ward's triangle, greater trochanter, and proximal shaft in bone marrow adipose tissue and separately within red and yellow marrow adipose tissue. RESULTS: Significant differences in fat composition in postmenopausal compared to premenopausal women, which varied depending on the subregion analyzed, were found. Within both whole and yellow marrow adipose tissue, postmenopausal women demonstrated higher saturation (+14.7% to +43.3%), lower mono- (-11.4% to -33%) and polyunsaturation (-52 to -83%) (p < 0.05). Within red marrow adipose tissue, postmenopausal women demonstrated lower fat quantity (-16% to -24%) and decreased polyunsaturation (-80 to -120%) in the femoral neck, greater trochanter, and Ward's triangle (p < 0.05). CONCLUSION: CSE-MRI can be used to detect subregional differences in proximal femur marrow adipose tissue composition between pre- and post-menopausal women in clinically feasible scan times.

Localized 2D COSY sequences: Method and experimental evaluation for a whole metabolite quantification approach.

Two-dimensional spectroscopy offers the possibility to unambiguously distinguish metabolites by spreading out the multiplet structure of J-coupled spin systems into a second dimension. Quantification methods that perform parametric fitting of the 2D MRS signal have recently been proposed for resolved PRESS (JPRESS) but not explicitly for Localized Correlation Spectroscopy (LCOSY). Here, through a whole metabolite quantification approach, correlation spectroscopy quantification performances are studied. The ability to quantify metabolite relaxation constant times is studied for three localized 2D MRS sequences (LCOSY, LCTCOSY and the JPRESS) in vitro on preclinical MR systems. The issues encountered during implementation and quantification strategies are discussed with the help of the Fisher matrix formalism. The described parameterized models enable the computation of the lower bound for error variance--generally known as the Cramér Rao bounds (CRBs), a standard of precision--on the parameters estimated from these 2D MRS signal fittings. LCOSY has a theoretical net signal loss of two per unit of acquisition time compared to JPRESS. A rapid analysis could point that the relative CRBs of LCOSY compared to JPRESS (expressed as a percentage of the concentration values) should be doubled but we show that this is not necessarily true. Finally, the LCOSY quantification procedure has been applied on data acquired in vivo on a mouse brain.