Vertebral Fat Fraction Research Articles

Assessing fat fraction and R2* value of lumbar spine based on MRI as a marker of bone mineral density.

The study aimed to investigate the correlation between fat fraction (FF), R2* value of vertebrae based on IDEAL-IQ sequence and bone mineral density (BMD) based on QCT, and their diagnostic value for low BMD and osteoporosis. Subgroups were divided according to different gender, age, BMI and bone mass to compare the differences in parametric variables. One-way ANOVA, independent samples t-test, correlation coefficient analysis, linear regression analysis and ROC curve analysis were performed. Significant differences were found in FF among different bone mass groups, and between different gender and age groups. While R2* only had significant difference between different gender groups and males with different age. BMD was significantly negatively correlated with FF, especially in women, and FF significantly negatively affected BMD after controlling for gender, age and BMI. There was mildly positive correlation between BMD and R2* in men, and R2* significantly positively influenced BMD controlling for the confounders. In addition, FF was positively correlated with age, whereas R2* was negatively correlated with age in men. FF had high diagnostic efficacy for low bone mass and osteoporosis, while R2* alone was weakly diagnostic. Vertebral FF can be served as a potential important imaging biomarker for assessing low BMD and osteoporosis, and R2* of males can be utilized as an complementary parameter for evaluating osteoporosis. The IDEAL-IQ sequence has the potential to be used as an accessory examination in the diagnosis of osteoporosis, assessment of treatment efficacy and prediction of fracture risk.

Quantitative analysis of vertebral fat fraction and R2* in osteoporosis using IDEAL-IQ sequence

ObjectiveTo investigate the correlation between FF, R2* value of IDEAL-IQ sequence and bone mineral density, and to explore their application value in the osteoporosis.MethodsWe recruited 105 women and 69 men aged over 30 years who voluntarily underwent DXA and MRI examination of lumbar spine at the same day. Participants were divided into normal, osteopenia and osteoporosis group based on T-score and BMD value of DXA examination. One-way ANOVA was adopted to compare the quantitative parameters among the three groups. Independent samples t-test was utilized to compare FF and R2* value between men and women.Pearson correlation analysis was used to research the correlation between FF, R2* value and BMD.ResultsAge, height, weight, BMD and FF value were significantly different among three groups (p < 0.05). No significant difference was found in FF value between male and female group, while R2* value were significantly different. Vertebral FF was moderately negatively correlated with aBMD, especially in women (r = -0.638, p < 0.001). R2* was mildly to moderately positively correlated with aBMD in men (r = 0.350, p = 0.003), but not in women. Moreover, FF was positively correlated with age, R2* was negatively correlated with age in men, and BMD was negatively correlated with age.ConclusionsThe vertebral FF value of IDEAL-IQ sequence has the potential to be a new biological marker for the assessment of osteoporosis. Vertebral FF is moderately negatively correlated with aBMD, especially in women, allowing accuratly quantify the bone marrow fat. R2* value is mildly to moderately correlated with BMD in men and can be served as a complementary tool in the assessment of osteoporosis.

Evidence- and data-driven classification of low back pain via artificial intelligence: Protocol of the PREDICT-LBP study.

In patients presenting with low back pain (LBP), once specific causes are excluded (fracture, infection, inflammatory arthritis, cancer, cauda equina and radiculopathy) many clinicians pose a diagnosis of non-specific LBP. Accordingly, current management of non-specific LBP is generic. There is a need for a classification of non-specific LBP that is both data- and evidence-based assessing multi-dimensional pain-related factors in a large sample size. The "PRedictive Evidence Driven Intelligent Classification Tool for Low Back Pain" (PREDICT-LBP) project is a prospective cross-sectional study which will compare 300 women and men with non-specific LBP (aged 18-55 years) with 100 matched referents without a history of LBP. Participants will be recruited from the general public and local medical facilities. Data will be collected on spinal tissue (intervertebral disc composition and morphology, vertebral fat fraction and paraspinal muscle size and composition via magnetic resonance imaging [MRI]), central nervous system adaptation (pain thresholds, temporal summation of pain, brain resting state functional connectivity, structural connectivity and regional volumes via MRI), psychosocial factors (e.g. depression, anxiety) and other musculoskeletal pain symptoms. Dimensionality reduction, cluster validation and fuzzy c-means clustering methods, classification models, and relevant sensitivity analyses, will classify non-specific LBP patients into sub-groups. This project represents a first personalised diagnostic approach to non-specific LBP, with potential for widespread uptake in clinical practice. This project will provide evidence to support clinical trials assessing specific treatments approaches for potential subgroups of patients with non-specific LBP. The classification tool may lead to better patient outcomes and reduction in economic costs.

Associations between vertebral bone marrow fat and sagittal spine alignment as assessed by chemical shift-encoding-based water–fat MRI

BackgroundThe relationship between sagittal spine alignment and vertebral bone marrow fat is unknown. We aimed to assess the relationship between vertebral bone marrow fat and sagittal spine alignment using chemical shift-encoding-based water–fat magnetic resonance imaging (MRI).MethodsA total of 181 asymptomatic volunteers were recruited for whole spine X-ray and lumbar MRI. Spine typing was performed according to the Roussouly classification and measurement of vertebral fat fraction based on the chemical shift-encoding-based water–fat MRI. One-way analysis of variance (ANOVA) was used to analyze the differences in vertebral fat fraction between spine types. The post hoc least significant difference (LSD) test was utilized for subgroup comparison after ANOVA.ResultsOverall, the vertebral fat fraction increased from L1 to L5 and was the same for each spine type. The vertebral fat fraction was the highest in type 1 and lowest in type 4 at all levels. ANOVA revealed statistically significant differences in fat fraction among different spine types at L4 and L5 (P < .05). The post hoc LSD test showed that the fat fraction of L4 was significantly different (P < .05) between type 1 and type 4 as well as between type 2 and type 4. The fat fraction of L5 was significantly different between type 1 and type 3, between type 1 and type 4, and between type 2 and type 4 (P < .05).ConclusionOur study found that vertebral bone marrow fat is associated with sagittal spine alignment, which may serve as a new additional explanation for the association of sagittal alignment with spinal degeneration.

Correlation of R2* with fat fraction and bone mineral density and its role in quantitative assessment of osteoporosis.

To investigate the correlation of R2* with vertebral fat fraction (FF) and bone mineral density (BMD), and to explore its role in the quantitative assessment of osteoporosis (OP). A total of 83 patients with low back pain (59.77 ± 7.46 years, 30 males) were enrolled, which underwent lumbar MRI in IDEAL-IQ sequences and quantitative computed tomography (QCT) scanning within 48h. The FF, R2*, and BMD of all 415 lumbar vertebrae were respectively measured. According to BMD, all vertebrae were divided into BMD normal, osteopenia, and OP groups, and the difference of FF and R2* among groups was analyzed by one-way ANOVA. The correlation between R2*, FF, and BMD was analyzed by Pearson's test. Taking BMD as the gold standard, the efficacies for FF and R2* in diagnosis of OP and osteopenia were assessed by receiver operating characteristic curve, and their area under the curve (AUC) was compared with DeLong's test. The FF and R2* were statistically different among groups (F values of 102.521 and 11.323, both p < 0.05), and R2* were significantly correlated with FF and BMD, respectively (r values of -0.219 and 0.290, both p < 0.05). In diagnosis of OP and osteopenia, the AUCs were 0.776 and 0.778 for FF and 0.638 and 0.560 for R2*, and the AUCs of R2* were lower than those of FF, with Z values of 4.030 and 4.087, both p < 0.001. R2* is significantly correlated with FF and BMD and can be used as a complement to FF and BMD for quantitative assessment of OP. • R2* based on IDEAL-IQ sequences has a definite but weak linear relationship with FF and BMD. • FF is significantly correlated with BMD and can effectively evaluate BMAT. • R2* can be used as a complement to FF and BMD for fine quantification of bone mineral loss and bone marrow fat conversion.

Accuracy and applicability of dual-energy computed tomography in quantifying vertebral bone marrow adipose tissue compared with magnetic resonance imaging

ObjectivesTo evaluate the accuracy of dual-energy computed tomography (DECT) in quantifying bone marrow adipose tissue (BMAT) and its applicability in the study of osteoporosis (OP).MethodsA total of 83 patients with low back pain (59.77 ± 7.46 years, 30 males) were enrolled. All patients underwent lumbar DECT and magnetic resonance imaging (MRI) scanning within 48 h, and the vertebral fat fraction (FF) was quantitatively measured, recorded as DECT-FF and MRI-FF. A standard quantitative computed tomography (QCT) phantom was positioned under the waist during DECT procedure to realize the quantization of bone mineral density (BMD). The intraclass correlation coefficient (ICC) and Bland–Altman method was used to evaluate the agreement between DECT-FF and MRI-FF. The Pearson test was used to study the correlation between DECT-FF, MRI-FF, and BMD. With BMD as a gold standard, the diagnostic efficacy of DECT-FF and MRI-FF in different OP degrees was compared by receiver operating characteristic (ROC) curve and DeLong test.ResultsThe values of DECT-FF and MRI-FF agreed well (ICC = 0.918). DECT-FF and MRI-FF correlated with BMD, with r values of −0.660 and −0.669, respectively (p < 0.05). In the diagnosis of OP and osteopenia, the areas under curve (AUC) of DECT-FF was, respectively, 0.791 and 0.710, and that of MRI-FF was 0.807 and 0.708, and there was no significant difference between AUCs of two FF values (with Z values of 0.503 and 0.066, all p > 0.05).ConclusionDECT can accurately quantify the BMAT of vertebrae and has the same applicability as MRI in the study of OP.

Quantitative Study of Vertebral Body and Paravertebral Muscle Degeneration Based on Dual-Energy Computed Tomography: Correlation With Bone Mineral Density.

This study aimed to quantify the degeneration of the vertebral body and paravertebral muscles using dual-energy computed tomography (DECT) and study its relationship with osteoporosis. A total of 130 patients with chronic low back pain were included in this study, and DECT scanning of the lumbar region was undertaken prospectively. By placing a standard quantitative computed tomography corrected phantom under the waist during the DECT procedure, bone mineral density (BMD) and the following quantitative parameters were obtained: calcium density (CaD), vertebral fat fraction (VFF), psoas major area, psoas major fat fraction, erector spinalis area, and erector spinalis fat fraction (ESFF). Independent sample t test and 1-way analysis of variance were used between different age-BMD groups. Pearson test was applied to determine correlations for all measurements, and a mathematical model of BMD was established through regression analysis. Calcium density, VFF, psoas major area, psoas major fat fraction, erector spinalis area, and ESFF were significantly different among the age-BMD groups (P < 0.05), and BMD was significantly correlated with these parameters (P < 0.05). Calcium density, VFF, and ESFF were included in the BMD regression equation: BMD = 69.062 + 11.637 × CaD - 1.018 × VFF - 0.726 × ESFF (R2 = 0.860, F = 125.979, P < 0.001). Degeneration of the vertebral body and paravertebral muscles can be quantitatively analyzed using DECT, and CaD, VFF, and ESFF were independent influencing factors of BMD.

Predicting Lumbar Vertebral Osteopenia Using LvOPI Scores and Logistic Regression Models in an Exploratory Study of Premenopausal Taiwanese Women

PurposeTo propose hybrid predicting models integrating clinical and magnetic resonance imaging (MRI) features to diagnose lumbar vertebral osteopenia (LvOPI) in premenopausal women.MethodsThis prospective study enrolled 101 Taiwanese women, including 53 before and 48 women after menopause. Clinical information, including age, body height, body weight and body mass index (BMI), were recorded. Bone mineral density (BMD) was measured by the dual-energy X-ray absorptiometry. Lumbar vertebral fat fraction (LvFF) was measured by MRI. LvOPI scores (LvOPISs) comprising different clinical features and LvFF were constructed to diagnose LvOPI. Statistical analyses included normality tests, linear regression analyses, logistic regression analyses, group comparisons, and diagnostic performance. A P value less than 0.05 was considered as statistically significant.ResultsThe post-menopausal women had higher age, body weight, BMI, LvFF and lower BMD than the pre-menopausal women (all P < 0.05). The lumbar vertebral osteoporosis group had significantly higher age, longer MMI, and higher LvFF than the LvOPI group (all P < 0.05) and normal group (all P < 0.005). LvOPISs (AUC, 0.843 to 0.864) outperformed body weight (0.747; P = 0.0566), BMI (0.737; P < 0.05), age (0.649; P < 0.05), and body height (0.5; P < 0.05) in diagnosing LvOPI in the premenopausal women. Hybrid predicting models using logistic regression analysis (0.894 to 0.9) further outperformed all single predictors in diagnosing LvOPI in the premenopausal women (P < 0.05).ConclusionThe diagnostic accuracy of the LvOPI can be improved by using our proposed hybrid predicting models in Taiwanese premenopausal women.

Exercise may impact on lumbar vertebrae marrow adipose tissue: Randomised controlled trial.

Animal and human cross-sectional data suggest that bone marrow adipose tissue (MAT) may respond to mechanical loads and exercise. We conducted the first randomised controlled trial of exercise on MAT modulations in humans. Forty patients with chronic non-specific low back pain (NSCLBP) were enrolled in a six-month single-blinded randomised controlled trial (ACTRN12615001270505). Twenty patients loaded their spines via progressive upright aerobic and resistance exercises targeting major muscle groups (Exercise). Twenty patients performed non-weightbearing motor control training and manual therapy (Control). Testing occurred at baseline, 3-months (3mo) and 6-months (6mo). Lumbar vertebral fat fraction (VFF) was measured using magnetic resonance imaging axial mDixon sequences. When compared to baseline (percent change), lumbar vertebral fat fraction (VFF; measured using magnetic resonance imaging axial mDixon sequences) was lower in Exercise at 3mo at L2 (-3.7[6.8]%, p=0.033) and L4 (-2.6[4.1]%, p=0.015), but not in Control. There were no between-group effects. The effects of Exercise on VFF were sex-specific, with VFF lower in men at L2, L3, L4 at 3mo and at L1, L2, L3 and L4 at 6mo (p all≤0.05), but not in women. Leg and trunk lean mass were increased at 3mo in Exercise. Changes in VFF correlated significantly with changes in total fat (ρ=0.40) and lean (ρ=-0.41) masses, but not with lumbar BMD (ρ=-0.10) or visceral adipose tissue volume (ρ=0.23). This trial provided first prospective evidence in humans that a moderate exercise intervention may modulate lumbar VFF as a surrogate measure of MAT at 3mo, yet not 6mo. The effect of exercise on MAT may be more prominent in males than females.

Mapping the medullar adiposity of lumbar spine in MRI: A feasibility study

PurposeThe bone medullar adiposity is a marker of bone quality to the point that there is a need to investigate the factors which influence or not the density and distribution of this fat in the spine, especially at the lumbar level. The purpose was to test the feasibility of a Dixon three-point technique and investigate the vertebral marrow fat distribution. Material and methodsA sagittal sequence Iterative Decomposition of Water and Fat with Echo Asymmetry and Least-squares Estimation (IDEAL) IQ was performed on the lumbar spine of 46 subjects who were not suffering from any bone disease (21 women and 25 men, aged 18–77 years). Medulla adiposity was determined directly from the measurement of the fat fraction in each vertebral body (T12 to S1) obtained on the fat cartography automatically generated by the IDEAL sequence. ResultsAverage vertebral fat fraction was 36.48% (SD 12.82), with a tendency to increase with age and to higher values among men. We observed a craniocaudal gradient of the fat fraction (β = 1.37; p < 0,001; SD 0.11) increasing with age in the lumbar spine from T12 to L5. Through multivariate analysis, this gradient was adjusted for sex, weight and height of the subjects. ConclusionThis feasibility study shows the existence of a physiological craniocaudal gradient of vertebral medullar adiposity from T12 to L5. This gradient increases with age but it is independent of sex or BMI. The IDEAL sequence allows quick and reproducible measurement of the spine vertebral medullar adiposity.

Bone Marrow Reconversion With Reambulation: A Prospective Clinical Trial.

In a prospective clinical trial, 20 healthy men participated in a 60-day, 6-degree head-down tilt bed rest study. Serial 3-T magnetic resonance (MR) imaging measures of the lumbar spine were performed at baseline, after 57 days of bed rest, and at 30, 360, and 720 days of reambulation (100 MR imaging scans). Proton density with and without fat saturation, 2-point Dixon, and single-voxel MR spectroscopy techniques were used to assess bone marrow composition (300 measures). Erythropoiesis was measured using hematocrit, reticulocyte, and ferritin. Also, participants randomly received either a nutritional intervention composed of polyphenols, omega-3, vitamin E, and selenium or a normal diet. Thirty days of reambulation after 60 days of bed rest caused a marked decrease of the mean lumbar vertebral fat fraction (VFF) (-9.2 ± 1.6 percentage points, -8.0 ± 1.3 percentage points, and -12.7 ± 1.2 percentage points compared with baseline using proton density, Dixon, MR spectroscopy, respectively; all 3, P < 0.05). Reambulation also decreased the fat saturation index (-5.3 ± 1.1 percentage points compared with baseline; P < 0.05). These coincided with lower hematocrit and ferritin and with increased reticulocytes at reambulation day 13 compared with baseline (all 3, P < 0.05). After 57 days of bed rest, the VFF was unchanged from baseline (all 3 MR techniques, P > 0.05); reambulation for 2 years returned the lumbar VFF to baseline values. This longitudinal trial established that 30 days of reambulation after 60 days of bed rest constituted a powerful stimulus for bone marrow reconversion. In this model, the enhanced erythropoiesis coupled with preferential consumption of fatty acids from regulated marrow adipose tissue to supply energy for erythropoiesis and bone anabolism may explain the lumbar vertebrae reconversion. These results will help interpreting bone marrow signal in ambulatory patients after long periods of bed rest.

Marrow adipose tissue gradient is preserved through high protein diet and bed rest. A randomized crossover study

ContextMarrow adipose tissue (MAT) has a peripheral to central distribution in adults, higher in peripheral bones. Similarly, the spine has a caudal to cephalad MAT distribution, higher in lumbar vertebras. Diet and the level of physical activities are known modulators of MAT with significant impact on bone; however, whether these can modulate the MAT gradient is unknown. ObjectiveTo measure the effect of high protein diet and bed rest interventions on the lumbar MAT gradient. Design, participants, interventionIn a prospective randomized crossover trial, 10 healthy men participated in 2 consecutive campaigns of 21days head-down-tilt-bed-rest (HDTBR). They received either whey protein and potassium bicarbonate-supplemented or control diet separated by a 4-month washout period. Main outcome measure(s)Ten serial MRI measures of lumbar vertebral fat fraction (VFF) were performed at baseline, 10days and 20days of HDTBR and 3 and 28days after HDTBR of each bed rest campaign. ResultsThe mean L5-L1 VFF difference of 4.2±1.2 percentage point higher at L5 (p=0.008) constituted a caudal to cephalad lumbar MAT gradient. High protein diet did not alter the lumbar VFF differences during both HDTBR campaigns (all time points p>0.05). Similarly, 2 campaigns of 21days of HDTBR did not change the lumbar VFF differences (all time points p>0.05). ConclusionsThis pilot study established that the lumbar vertebral MAT gradient was not altered by a high protein nor by 2×21days bed rest interventions. These findings demonstrated that this lack of mechanical stimulus was not an important modulator of the lumbar MAT gradient. The highly preserved MAT gradient needs to be measured in more situations of health and disease and may potentially serve to detect pathological situations.

Intervertebral disc status is associated with vertebral marrow adipose tissue and muscular endurance.

Low back pain is a major public health issue. Identifying factors associated with better intervertebral disc (IVD) characteristics gives insight into IVD metabolism and highlights intervention targets for improvement of IVD health. This cross-sectional study investigates whether IVD T2-relaxation time on magnetic resonance imaging (MRI) is associated with vertebral fat fraction (VFF; to quantify marrow adipose tissue), trunk muscle cross-sectional area (CSA), muscle function and physical activity (PA). Seventy-nine healthy subjects (35 males, 44 females) without history of spinal disease were included. Lumbar IVDs T2-relaxation time, lumbar VFF and CSA of multifidus, erector spinae, quadratus lumborum, and psoas muscles were quantified via MRI. Isometric trunk flexion and extension endurance times as well as habitual PA levels and exposure to occupational spine risk factors were documented. Pearson-partial correlations adjusted for anthropometric differences by controlling for vertebral body height. Higher IVD T2-time correlated with: (a) lower VFF (r = -0.27, p < 0.05), (b) greater trunk extensor muscle endurance (r = 0.37, p < 0.01), and (c) greater trunk flexor muscle endurance (r = 0.30, p < 0.01) but not with muscle CSA. Lower VFF also correlated with greater extensor muscle endurance (r = -0.26, p < 0.05) and habitual PA (MET-mins per week) (r = -0.24, p < 0.05). This is the first study to show that better IVD hydration is associated with lower VFF and that greater physical activity is associated with favourable levels of vertebral marrow adipose tissue in young healthy individuals. Reduced vertebral marrow adipose tissue may specifically improve IVD hydration via improved nutrient supply. These slides can be retrieved under Electronic Supplementary Material.

Abstract B29: Increased vertebral marrow adiposity in long-term survivors of pediatric allogeneic hematopoietic stem cell transplant is associated with deficits in trabecular microarchitecture

Abstract Background: As treatment-related mortality following allogeneic hematopoietic stem-cell transplantation (alloHSCT) declines, a major unmet need is the identification and prevention of late effects. Long-term survivors of hematologic malignancies requiring alloHSCT show impaired bone density and structure with excess whole body adiposity (Mostoufi-Moab, JBMR, 2012). Marrow adipocytes share common mesenchymal stem cells (MSC) with bone-forming osteoblasts, with an inverse relation between MSC differentiation into osteoblasts or adipocytes. The impact of alloHSCT and total body irradiation (TBI) on marrow adipose tissue (MAT) and trabecular bone microarchitecture (TBA) has not been addressed. Methods: Magnetic resonance spectroscopic imaging (MRSI) and high-resolution structural imaging were used to quantify vertebral MAT and distal tibia TBA on a 1.5 Tesla magnet. Twenty-five alloHSCT recipients with underlying diagnosis of acute leukemia, ages 12-24 years, were enrolled, a median of 11 years (range 5-19) after alloHSCT and TBI, and compared with age-, sex- and race-matched healthy controls. Results: AlloHSCT survivors had lower height Z-scores (-1.39 ± 0.98 vs. -0.04 ± 0.98; p &amp;lt; 0.001), compared with controls, while BMI Z-scores did not differ. Overall, greater MAT was associated with lower bone volume fraction (BVF), R = -0.57, p &amp;lt; 0.001. AlloHSCT was associated with higher mean (± SD) vertebral fat fraction (59.0 ± 11.3 vs. 29.3 ± 9.9; p &amp;lt; 0.001) and trabecular deficits including lower bone volume fraction (β -0.01; 95% CI -0.12, -0.00; p=0.02) and evidence of abnormal microarchitecture [greater erosion (p=0.01) with a more rod like structure (p=0.02)], vs. controls. TBA deficits were more pronounced in female alloHSCT recipients. Growth hormone deficiency was not associated with MAT or bone deficits. Conclusion: Survivors of childhood alloHSCT after TBI demonstrate marked increases in vertebral MAT combined with abnormal trabecular bone microarchitecture. Future studies are needed to determine the metabolic effects and fracture implications of excess MAT, and to identify therapies for improved bone accrual following childhood alloHSCT. Citation Format: Sogol Mostoufi-Moab, Wenli Sun, Jeremy Magland, Elizabeth Isaacoff, Nancy J. Bunin, Jill P. Ginsberg, Felix Wehrli, Justine Shults, Mary B. Leonard. Increased vertebral marrow adiposity in long-term survivors of pediatric allogeneic hematopoietic stem cell transplant is associated with deficits in trabecular microarchitecture. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr B29.

Fat Fraction Estimation of the Vertebrae in Females Using the T2*-IDEAL Technique in Detection of Reduced Bone Mineralization Level

The aim of this study was to use the T2*-iterative decomposition of water and fat with echo asymmetry and least squares estimation quantification (IDEAL) technique to estimate vertebral fat fraction (FF) and compare it with bone mineralization levels in females. Forty-five (mean age, 49.5 years) consecutive women who underwent magnetic resonance imaging and spinal dual-energy x-ray absorptiometry bone mineral density (BMD) examination constituted the study population. Depending on t scores derived from dual-energy x-ray absorptiometry, the vertebrae were classified into 3 groups (1, healthy; 2, osteopenia; and 3, osteoporosis). The Spearman ρ test was used to investigate the presence of correlation between FF and BMD. Analysis of covariance was performed to compare the differences among the groups. The FF cutoff value for the prediction of osteoporosis/osteopenia was evaluated with the receiver operating characteristic curve analysis. We found a moderate negative correlation between BMD (grams per square centimeter) and FF (r = - 0.42), and it was statistically significant (P < 0.001). The FF mean of age-corrected group 1 (45.17%; SD, 1.3) was lower than that of groups 2 (51.77%; SD, 0.69) and 3 (50.82%; SD, 1.5), and the difference was statistically significant (P < 0.001, P = 0.021). The area under the receiver operating characteristic curve for FF was 0.80 (95% confidence interval, 0.72-0.86). The optimal cutoff point was obtained as 39%, and for this cutoff point, the sensitivity and the specificity were 93% and 60.3%, respectively. The T2*-IDEAL technique can be used as an alternative technique in estimation of FF, and it is possible to detect reduced bone mineralization of the vertebrae by estimation of FF value with this technique.

Rapid determination of vertebral fat fraction over a large range of vertebral bodies

Vertebral body fat fraction (FF) has been found to vary between lumbar vertebrae using magnetic resonance spectroscopy (MRS). We aim to more quickly assess a larger number of adjacent vertebrae using a single T2-weighted iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) sequence. Five men had dual-energy X-ray absorptometry (DEXA) and 1.5-T MR scans performed. MRS was performed at L3, and a sagittal IDEAL sequence was also performed, resulting in separate fat-only and water-only readings from T10 to S2. For the IDEAL measurements, two independent observers followed a set reading protocol, with five observations each per vertebra. Intra- and interobserver variability were assessed as deviations from the mean within and between observers, respectively. For FF measurements there was limited intra-observer variation, with observers being on average within 3.4% of the pooled mean value. Similarly, there was good interobserver agreement, with an average variation of 2.1%. All men showed a reduction in FF of 1.6-7% between L5 and S1. Otherwise, there was a trend of increasing FF moving inferiorly from T10 to S2. This averaged 2.7% per vertebra (range 1.1-3.8%) and may not have been dependent on MRS-measured FF at the L3 level. There was poor correlation between MRS-measured FF at L2-4 and bone mineral density measured using DEXA (R(2) = 0.06). IDEAL measurements are generally reproducible between observers following a set protocol. There appears to be a gradient in FF moving from T10 to S2, with S1 showing a consistent decrease. This variation may better describe overall marrow function than a single-vertebra reading.

Resistive exercises, with or without whole body vibration, prevent vertebral marrow fat accumulation during 60 days of head-down tilt bed rest in men

Fat accumulates in the bone marrow of lumbar vertebrae with bed rest. Exercise with or without whole body vibration may counter this effect. Our objectives were to measure 1) the vertebral fat fraction (VFF) of men subjected to bed rest who performed resistive exercises with (RVE, n = 7) or without whole body vibration(RE, n = 8) or no exercise (CTR, n = 9) using three MRI techniques; and 2) changes in peripheral blood counts. Twenty-four healthy men (age: 20-45 yr) underwent -6° head-down tilt (HDT) bed rest for 60 days. MRI was performed using three techniques (fat saturation, proton spectroscopy, and in and out of phase) to measure the fat fraction of L(3), L(4), and/or L(5) at baseline, mid-HDT, and end-HDT. Erythrocytes and leukocytes were counted at HDT days 19, 33, 47, 54, and 60. The mean absolute VFF was increased in the CTR group at mid-HDT and end-HDT (+3.9 ± 1.3 and +3.6 ± 1.2%, respectively, both P < 0.05). The RE group had a smaller VFF change than the CTR group at mid-HDT (-0.9 ± 1.2 vs. +3.9 ± 1.3%, P < 0.05). The RVE group had a smaller VFF change than the CTR group at end-HDT (-2.6 ± 1.9 vs. +3.5 ± 1.2%, P < 0.05). Erythrocyte counts were increased in all groups at HDT day 19 and HDT day 33 and in the RE group at HDT day 54 (all P < 0.05). Bed rest for 60 days at -6° HDT increased lumbar VFF in men beyond natural involution. RVE and RE regimens effectively prevented VFF accumulation. Higher erythrocyte counts were not altered by RVE or RE. Whole body vibration, along with RE administered to people with prolonged immobility, may prevent fat accumulation in their bone marrow.

Bone marrow fat accumulation after 60 days of bed rest persisted 1 year after activities were resumed along with hemopoietic stimulation: the Women International Space Simulation for Exploration study

Immobility in bed and decreased mobility cause adaptations to most human body systems. The effect of immobility on fat accumulation in hemopoietic bone marrow has never been measured prospectively. The reversibility of marrow fat accumulation and the effects on hemopoiesis are not known. In the present study, 24 healthy women (age: 25-40 yr) underwent -6 degrees head-down bed rest for 60 days. We used MRI to noninvasively measure the lumbar vertebral fat fraction at various time points. We also measured hemoglobin, erythropoietin, reticulocytes, leukocytes, platelet count, peripheral fat mass, leptin, cortisol, and C-reactive protein during bed rest and for 1 yr after bed rest ended. Compared with baseline, the mean (+/-SE) fat fraction was increased after 60 days of bed rest (+2.5+/-1.1%, P<0.05); the increase persisted 1 yr after the resumption of regular activities (+2.3+/-0.8%, P<0.05). Mean hemoglobin levels were significantly decreased 6 days after bed rest ended (-1.36+/-0.20 g/dl, P<0.05) but had recovered at 1 yr, with significantly lower mean circulating erythropoietin levels (-3.8+/-1.2 mU/ml, P<0.05). Mean numbers of neutrophils and lymphocytes remained significantly elevated at 1 yr (+617+/-218 neutrophils/microl and +498+/-112 lymphocytes/microl, both P<0.05). These results constitute direct evidence that bed rest irreversibly accelerated fat accumulation in hemopoietic bone marrow. The 2.5% increase in fat fraction after 60 days of bed rest was 25-fold larger than expected from historical ambulatory controls. Sixty days of bed rest accelerated by 4 yr the normal bone marrow involution. Bed rest and marrow adiposity were associated with hemopoietic stimulation. One year after subjects returned to normal activities, hemoglobin levels were maintained, with 43% lower circulating erythropoietin levels, and leukocytes remained significantly elevated across lineages. Lack of mobility alters hemopoiesis, possibly through marrow fat accumulation, with potentially wide-ranging clinical consequences.

Quantitative imaging of Gaucher disease.

Twenty-three patients with type 1 Gaucher disease were evaluated with a battery of quantitative imaging techniques. Plain radiographs were used to measure cortical thickness and Erlenmeyer flask deformity. Xenon-133 uptake was measured in scans of the lower extremities. Dual-energy quantitative computed tomography was used for calculation of trabecular bone and bone marrow fat content in the spine and long bones. Magnetic resonance (MR) imaging was performed to evaluate disease extent and three-dimensional splenic volume. MR images were also used to provide quantitative measurements of each vertebral fat fraction. Each imaging modality was correlated with the others as well as with the clinical history of skeletal complications and the hematocrit and acid phosphatase activity. There was a strong relationship between splenic volume and disease severity as measured clinically and with laboratory testing. The spinal fat fraction also correlated with these measures of disease severity and with the femoral fat fraction and xenon uptake. No measurement allowed discrimination of patients with from those without skeletal complications.