Explore the vast range of titles available.

Background Paraspinal muscle fat infiltration is associated with spinal degeneration and low back pain, however, quantifying muscle fat using clinical magnetic resonance imaging (MRI) techniques continues to be a challenge. Advanced MRI techniques, including chemical‐shift encoding (CSE) based water–fat MRI, enable accurate measurement of muscle fat, but such techniques are not widely available in routine clinical practice. Methods To facilitate assessment of paraspinal muscle fat using clinical imaging, we compared four thresholding approaches for estimating muscle fat fraction (FF) using T1‐ and T2‐weighted images, with measurements from water–fat MRI as the ground truth: Gaussian thresholding, Otsu's method, K‐mean clustering, and quadratic discriminant analysis. Pearson's correlation coefficients (r), mean absolute errors, and mean bias errors were calculated for FF estimates from T1‐ and T2‐weighted MRI with water–fat MRI for the lumbar multifidus (MF), erector spinae (ES), quadratus lumborum (QL), and psoas (PS), and for all muscles combined. Results We found that for all muscles combined, FF measurements from T1‐ and T2‐weighted images were strongly positively correlated with measurements from the water–fat images for all thresholding techniques (r = 0.70–0.86, p < 0.0001) and that variations in inter‐muscle correlation strength were much greater than variations in inter‐method correlation strength. Conclusion We conclude that muscle FF can be quantified using thresholded T1‐ and T2‐weighted MRI images with relatively low bias and absolute error in relation to water–fat MRI, particularly in the MF and ES, and the choice of thresholding technique should depend on the muscle and clinical MRI sequence of interest. To facilitate assessment of paraspinal muscle fat using clinical imaging, we compared four approaches for estimating muscle fat fraction (FF) with T1‐ and T2‐weighted images using measurements from CSE MRI as the ground truth for validation: Gaussian thresholding, Otsu's method, k‐mean clustering, and quadratic discriminant analysis. Pearson's correlation coefficient (r), mean absolute error (MAE), and mean bias error (MBE) was calculated for FF estimates between T1‐ and T2‐weighted MRI and CSE MRI for the lumbar multifidus (MF), erector spinae (ES), quadratus lumborum (QL), and psoas (PS), and for all muscles together. We found that for all muscles combined, FF measurements from T1‐ and T2‐weighted images were strongly correlated with measurements from the water–fat images for all thresholding techniques and we therefore conclude that muscle FF can be reliably quantified using thresholded T1‐ and T2‐weighted MRI images with relatively low bias and absolute error in relation to water–fat MR, particularly in the MF and ES.

Background: Current evaluation of muscle fatty infiltration has been limited by subjective classifications. Quantitative fat evaluation through magnetic resonance imaging (MRI) may allow for an improved longitudinal evaluation of the effect of surgical repair on the progression of fatty infiltration. Hypotheses: We hypothesized that (1) patients with isolated full-thickness supraspinatus tendon tears would have less progression in fatty infiltration compared with patients with full-thickness tears of multiple tendons and (2) patients with eventual failed repair would have higher baseline levels of fatty infiltration. Study Design: Cohort study; Level of evidence, 2. Methods: Thirty-five patients with full-thickness rotator cuff tears were followed longitudinally. All patients received a shoulder MRI, including the iterative decomposition of echoes of asymmetric length (IDEAL) sequence for fat measurement, prior to surgical treatment and at 6 months after surgical repair. Fat fractions were recorded for all 4 rotator cuff muscles from measurements on 4 sagittal slices centered at the scapular-Y. Demographics and tear characteristics were recorded. Baseline and follow-up fat fractions were compared for patients with isolated supraspinatus tears versus multitendon tears and for patients with intact repairs versus failed repairs. Statistical significance was set at P < .05. Results: The mean fat fractions were significantly higher at follow-up than at baseline for the supraspinatus (9.8% ± 7.0% vs 8.3% ± 5.7%; P = .025) and infraspinatus (7.4% ± 6.1% vs 5.7% ± 4.4%; P = .027) muscles. Patients with multitendon tears showed no significant change for any rotator cuff muscle after repair. Patients with isolated supraspinatus tears showed a significant progression in the supraspinatus fat fraction from baseline to follow-up (from 6.8% ± 4.9% to 8.6% ± 6.8%; P = .0083). Baseline supraspinatus fat fractions were significantly higher in patients with eventual failed repairs compared with those with intact repairs (11.7% ± 6.8% vs 7.1% ± 4.8%; P = .037). Conclusion: Contrary to our initial hypothesis, patients with isolated supraspinatus tears showed a significant progression of fatty infiltration. Patients with eventual repair failure had higher baseline fat fractions in the supraspinatus.

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.

Background Current clinical protocols for MR-guided focused ultrasound (MRgFUS) treatment of osseous lesions, including painful bone metastases and osteoid osteomas, rely on measurement of the temperature change in adjacent muscle to estimate the temperature of the bone. The goal of this study was to determine if T2-based thermometry could be used to monitor the temperature change in bone marrow during focused ultrasound ablation of bone lesions. Methods We investigated the dependence of T2 on temperature in ex vivo bovine yellow bone marrow at 3T and studied the influence of acquisition parameters on the T2 measurements. We examined if T2 changes in red bone marrow caused by the ablation of ex vivo trabecular bone were reversible and measured the patterns of heating and tissue damage. The technique was validated during the ablation of intact ex vivo bone samples and an in vivo animal model. Results Results of the calibration experiment showed a linear relationship (7 ms/°C) between T2 change and temperature and could be used to quantify the temperature during heating of up to 60 °C. During trabecular bone ablation, we observed a linear relationship (5.7 ms per °C) between T2 and temperature during the heating stage of the experiment. After cool down, there was residual T2 elevation (~35 ms) in the ablated area suggesting irreversible tissue changes. In ex vivo and in vivo cortical bone ablation experiments, we observed an increase in T2 values in the marrow adjacent to the intersection of the cortical bone and the beam path. The in vivo experiment showed excellent correspondence between the area of T2 elevation in marrow during the ablation and the resulting non-enhancing area in the post-contrast images. Conclusions In this study, we have demonstrated that T2-based thermometry can be used in vivo to measure the heating in the marrow during bone ablation. The ability to monitor the temperature within the bone marrow allowed more complete visualization of the heat distribution into the bone, which is important for local lesion control.

Introduction Many studies have attempted to link multifidus (MF) fat infiltration with muscle quality and chronic low back pain (cLBP), but there is no consensus on these relationships. Methods In this cross‐sectional cohort study, 39 cLBP patients and 18 asymptomatic controls were included. The MF muscle was manually segmented at each lumbar disc level and fat fraction (FF) measurements were taken from the corresponding advanced imaging water‐fat images. We assessed the distribution patterns of MF fat from L1L2 to L5S1 and compared these patterns between groups. The sample was stratified by age, sex, body mass index (BMI), subject‐reported pain intensity (VAS), and subject‐reported low back pain disability (oswestry disability index, ODI). Results Older patients had significantly different MF FF distribution patterns compared to older controls (p < 0.0001). Male patients had 34.8% higher mean lumbar spine MF FF compared to male controls (p = 0.0006), significantly different MF FF distribution patterns (p = 0.028), 53.7% higher mean MF FF measurements at L2L3 (p = 0.037), and 50.6% higher mean MF FF measurements at L3L4 (p = 0.041). Low BMI patients had 29.7% higher mean lumbar spine MF FF compared to low BMI controls (p = 0.0077). High BMI patients only had 4% higher mean lumbar spine MF FF compared to high BMI controls (p = 0.7933). However, high BMI patients had significantly different MF FF distribution patterns compared to high BMI controls (p = 0.0324). Low VAS patients did not significantly differ from the control cohort for any of our outcomes of interest; however, high VAS patients had 24.3% higher mean lumbar spine MF FF values (p = 0.0011), significantly different MF FF distribution patterns (p < 0.0001), 34.7% higher mean MF FF at L2L3 (p = 0.040), and 34.6% higher mean MF FF at L3L4 (p = 0.040) compared to the control cohort. Similar trends were observed for ODI. Conclusions This study suggests that when the presence of paraspinal muscle fat infiltration is not characteristic of an individual's age, sex, and BMI, it may be associated with lower back pain. Many studies have attempted to link multifidus fat infiltration with muscle quality and chronic low back pain, but there is no consensus on these relationships. This study suggests that when the presence of fat is not characteristic of an individual's age, sex, and BMI, it may be a back pain risk factor.

Abstract ObjectiveTo qualitatively evaluate the utility of zero echo-time (ZTE) MRI sequences in identifying osseous findings and to compare ZTE with optimized spoiled gradient echo (SPGR) sequences in detecting knee osseous abnormalities.Materials and methodsZTE and standard knee MRI sequences were acquired at 3T in 100 consecutive patients. Three radiologists rated confidence in evaluating osseous abnormalities and image quality on a 5-grade Likert scale in ZTE compared to standard sequences. In a subset of knees (n = 57) SPGR sequences were also obtained, and diagnostic confidence in identifying osseous structures was assessed, comparing ZTE and SPGR sequences. Statistical significance of using ZTE over SPGR was characterized with a paired t-test.ResultsImage quality of the ZTE sequences was rated high by all reviewers with 278 out of 299 (100 studies, 3 radiologists) scores ≥ 4 on the Likert scale. Diagnostic confidence in using ZTE sequences was rated “very high confidence” in 97%, 85%, 71%, and 73% of the cases for osteophytosis, subchondral cysts, fractures, and soft tissue calcifications/ossifications, respectively. In 74% of cases with osseous findings, reviewer scores indicated confidence levels (score ≥ 3) that ZTE sequences improved diagnostic certainty over standard sequences. The diagnostic confidence in using ZTE over SPGR sequences for osseous structures as well as abnormalities was favorable and statistically significant (p < 0.01).ConclusionIncorporating ZTE sequences in the standard knee MRI protocol was technically feasible and improved diagnostic confidence for osseous findings in relation to standard MR sequences. In comparison to SPGR sequences, ZTE improved assessment of osseous abnormalities.

PurposeThe composition of the subchondral bone marrow and cartilage endplate (CEP) could affect intervertebral disc health by influencing vertebral perfusion and nutrient diffusion. However, the relative contributions of these factors to disc degeneration in patients with chronic low back pain (cLBP) have not been quantified. The goal of this study was to use compositional biomarkers derived from quantitative MRI to establish how CEP composition (surrogate for permeability) and vertebral bone marrow fat fraction (BMFF, surrogate for perfusion) relate to disc degeneration.MethodsMRI data from 60 patients with cLBP were included in this prospective observational study (28 female, 32 male; age = 40.0 ± 11.9 years, 19–65 [mean ± SD, min–max]). Ultra-short echo-time MRI was used to calculate CEP T2* relaxation times (reflecting biochemical composition), water-fat MRI was used to calculate vertebral BMFF, and T1ρ MRI was used to calculate T1ρ relaxation times in the nucleus pulposus (NP T1ρ, reflecting proteoglycan content and degenerative grade). Univariate linear regression was used to assess the independent effects of CEP T2* and vertebral BMFF on NP T1ρ. Mixed effects multivariable linear regression accounting for age, sex, and BMI was used to assess the combined relationship between variables.ResultsCEP T2* and vertebral BMFF were independently associated with NP T1ρ (p = 0.003 and 0.0001, respectively). After adjusting for age, sex, and BMI, NP T1ρ remained significantly associated with CEP T2* (p = 0.0001) but not vertebral BMFF (p = 0.43).ConclusionPoor CEP composition plays a significant role in disc degeneration severity and can affect disc health both with and without deficits in vertebral perfusion.

Osteoarthritis is a condition in which low-grade inflammation results in joint pain, and it is the most common joint disease. Interactions between all of the major joint tissues, including the articular cartilage, synovium, bone marrow, subchondral bone, trabecular bone, and muscle, have been implicated in osteoarthritis. Magnetic resonance images have been used to quantify the cartilage morphology, volume and thickness, and focal defects, and may reflect changes in the biochemical composition of articular cartilage.

PurposeFat infiltration (FI) of the paraspinal muscles (PSMs) measured using MRI is an aspect of muscle quality and is considered to be worse in chronic low back pain (cLBP) patients. However, there is not a clear association between paraspinal muscle FI and cLBP, leaving the clinical importance of paraspinal muscle composition unestablished. The spatial distribution of FI in the PSMs may inform mechanistic understanding of non-specific cLBP as it relates to degenerative intervertebral disc (IVD) pathology. We hypothesized that paraspinal muscle fat-mapping would reveal distinct FI distribution patterns in relation to cLBP symptoms and proximity to symptomatic IVD degeneration.MethodsFrom advanced-sequence water-fat MRI of 40 axial cLBP patients and 21 controls, we examined the spatial distribution of paraspinal muscle FI in relation to the center of rotation at the L4L5 disc. Using statistical parametric mapping, we compared FI patterns for multifidus (MF), erector spinae (ES), and psoas between patients and controls, and to the presence and severity of adjacent degenerative IVD pathology.ResultsThe spatial distribution of PSMs FI differs between PSMs and according to symptoms and the adjacent degenerative IVD pathology. Furthermore, the region of MF closest to the disc center of rotation appears most susceptible to FI in the presence of symptomatic IVD degeneration.ConclusionOur study identified spatial distribution patterns of FI in the PSMs as a potential diagnostic biomarker that may also provide granular mechanistic insights into spine biomechanics related to cLBP, as well as advancing the use of prior summary measures limited to overall muscle FI.

SummaryPeople living with HIV (PLWH) have increased risk of osteoporosis and fractures. We assessed the proximal femur of PLWH and age-matched seronegative controls using quantitative computed tomography and magnetic resonance imaging. Results suggest that the trabecular compartment is compromised at fracture-prone regions in the proximal femur of PLWH.IntroductionPeople living with HIV (PLWH) have increased risk of osteoporosis and fractures. However, studies assessing the main determinants of bone strength in the proximal femur exclude this vulnerable population. We assessed the proximal femur of 40 PLWH and 26 age-matched seronegative controls using quantitative computed tomography and magnetic resonance imaging.MethodsWe examined cortical volumetric bone mineral density (Ct.vBMD), trabecular vBMD (Tb.vBMD), cortical thickness (Ct.Th), bone marrow adiposity (BMA), and trabecular number, separation, and bone volume fraction. Parametric comparisons between the two groups were made for the femoral head, femoral neck, trochanter, and total hip using linear regression adjusting for several covariates, including metrics of body composition. In addition, we investigated the associations of BMA with Tb.vBMD and trabecular microarchitecture with Spearman’s rank partial correlations.ResultsPLWH had lower Tb.vBMD and deteriorated trabecular microarchitecture in the femoral neck, trochanter and total hip, and elevated BMA in the femoral head, femoral neck, and total hip. Ct.vBMD and Ct.Th were not significantly different between the two groups. BMA was significantly associated with lower Tb.vBMD and deteriorated trabecular microarchitecture in both groups albeit at different femoral regions.ConclusionsOur findings suggest that the trabecular, and not the cortical, compartment is compromised in the proximal femur of PLWH. The observed impairments in fracture-prone regions in PLWH indicate lower femoral strength and suggest higher fracture risk. The inverse associations of BMA with trabecular bone density and microarchitecture quality agree with findings at other anatomic sites and in other populations, suggesting that excess BMA possibly due to a switch from the osteoblast to the adipocyte lineage may be implicated in the pathogenesis of bone fragility at the femur in PLWH.