Quantification of vertebral bone marrow fat content using 3 Tesla MR spectroscopy: reproducibility, vertebral variation, and applications in osteoporosis

Purpose:

To determine the reproducibility of proton MR spectroscopy (¹H‐MRS) for assessing vertebral bone marrow adiposity at 3 Tesla (T); to evaluate variation of marrow adiposity at different vertebral levels; and to demonstrate the feasibility of using ¹H‐MRS at 3T for evaluating marrow adiposity in subjects with low bone density.

Materials and Methods:

Single voxel MRS was acquired at vertebral body L1 to L4 at 3T in 51 postmenopausal females including healthy controls (n = 13) and patients with osteoporosis/osteopenia (n = 38). Marrow fat contents were compared between vertebral levels and between groups using analysis of variance (ANOVA). Six subjects were scanned twice to evaluate technique reproducibility.

Results:

The average coefficient of variation of vertebral marrow fat content quantification was 1.7%. Marrow fat content significantly increased from L1 to L4. The average fat content was significantly elevated in patients with osteoporosis/osteopenia compared with controls, adjusted for age and body mass index (P < 0.05).

Conclusion:

In vivo MRS at high field strength provides reliable measurement of marrow adiposity with excellent reproducibility and can be a valuable tool for providing complementary information on bone quality and potentially also fracture risk. J. Magn. Reson. Imaging 2011;33:974–979. © 2011 Wiley‐Liss, Inc.     

Osteoporosis is associated with increased marrow fat content and decreased marrow fat unsaturation: a proton MR spectroscopy study

PURPOSE: To use proton magnetic resonance spectroscopy ((1)H-MRS) to evaluate vertebral marrow fat, and to determine whether bone density correlates with fat content and fat unsaturation levels in postmenopausal women. MATERIALS AND METHODS: Fifty-three women (mean age = 70 years) underwent dual energy x-ray absorptiometry and (1)H-MRS, and 12 young female controls (mean age = 28 years) underwent (1)H-MRS of the lumber spine. Water and lipid peak amplitudes were measured to calculate fat content and fat unsaturation index. Spearman's correlation tests and a t-test comparison of means were applied. RESULTS: (1)H-MRS was successful in 15 normal, 15 osteopenic, and 20 osteoporotic subjects, and in all controls. Marrow fat content was significantly elevated in osteoporotic (65.5% +/- 10%) and osteopenic (63.5% +/- 9.3%) subjects compared to normal subjects (56.3% +/- 11.2%) and young controls (29% +/- 9.6%). The fat unsaturation index was significantly decreased in osteoporotic (0.091 +/- 0.013) and osteopenic (0.097 +/- 0.014) subjects compared to normal subjects (0.114 +/- 0.016) and young controls (0.127 +/- 0.031). A good inverse correlation was observed between the fat content and the unsaturation index (r(s) = -0.53, P < 0.0001). CONCLUSION: Osteoporosis is associated with increased marrow fat. As marrow fat increases, saturated lipids appear to increase preferentially to unsaturated lipids.     

Age, gender, and skeletal variation in bone marrow composition: a preliminary study at 3.0 Tesla

PURPOSE: To evaluate the efficacy of MR Spectroscopy (MRS) at 3.0 Tesla for the assessment of normal bone marrow composition and assess the variation in terms of age, gender, and skeletal site. MATERIALS AND METHODS: A total of 16 normal subjects (aged between eight and 57 years) were investigated on a 3.0 Tesla GE Signa system. To investigate axial and peripheral skeleton differences, non-water-suppressed spectra were acquired from single voxels in the calcaneus and lumbar spine. In addition, spectra were acquired at multiple vertebral bodies to assess variation within the lumbar spine. Data was also correlated with bone mineral density (BMD) measured in six subjects using dual-energy X-ray absorptiometry (DXA). RESULTS: Fat content was an order of magnitude greater in the heel compared to the spine. An age-related increase was demonstrated in the spine with values greater in men compared to female subjects. Significant trends in vertebral bodies within the same subjects were also shown, with fat content increasing L5 > L1. Population coefficient of variation (CV) was greater for fat fraction (FF) compared to BMD. CONCLUSION: Significant normal variations of marrow composition have been demonstrated, which provide important data for the future interpretation of patient investigations.     

Bone marrow diffusion in osteoporosis: evaluation with quantitative MR diffusion imaging

PURPOSE: To determine the diffusion of vertebral body marrow with quantitative MR diffusion imaging and to examine whether differences exist between subjects with postmenopausal osteoporosis and premenopausal control subjects. MATERIALS AND METHODS: A total of 44 consecutive women (mean age, 70 years) with documented bone mineral density (BMD) measured by dual energy x-ray absorptiometry (T-score) and 20 normal subjects (mean age, 28 years) were examined with echo-planar diffusion imaging at 1.5 T using b values of 0, 20, 40, 60, 80, 100, 200, 300, 400, and 500 seconds/mm2. Extravascular diffusion (D) and apparent diffusion coefficient (ADC) were calculated and results from both groups compared. RESULTS: Both D and ADC values tended to decrease with decreasing BMD. Mean D values were significantly lower in postmenopausal women with reduced BMD (0.42 +/- 0.12 x 10(-3) mm2/second) than normal premenopausal women (0.50 +/- 0.09 x 10(-3) mm2/second). Mean ADC values were significantly lower both in subjects with reduced BMD (0.41 +/- 0.10 x 10(-3) mm2/second) and normal BMD (0.43 +/- 0.08 x 10(-3) mm2/second) compared to normal controls (0.49 +/- 0.07 x 10(-3) mm2/second). CONCLUSION: Accumulation of fatty bone marrow associated with osteoporosis is reflected by a decrease in D and ADC. Diffusion imaging may prove useful in the study of osteoporosis.     

~1H MRS对椎体骨髓研究初步应用

目的 探讨椎体骨髓脂肪含量(fat fraction,FF)在不同年龄组、性别的变化规律及与骨密度(bone mineral densities,BMD)的相关性.方法 对85名年龄21～70岁健康志愿者及20名已行腰椎双能量X线吸收测定(dual X-ray absorptionmetry,DXA)诊断为骨质疏松的老年男女进行前瞻性MR波谱分析,测定L_3椎体脂肪分数值(fat fraction,FF).健康志愿者按每10岁为一个年龄段,将其分为5组,每组16～18人.结果 21～30岁组、31～40岁组、41～50岁组、51～60岁组、>60岁组和骨质疏松组的FF分别为30.7%±4.4%、35.5%±6.8%、41.9%士6.6%、46.8%±5.5%、51.7%±5.2%和59.2%±7.4%;除>60岁组和骨质疏松组外,各组L_3椎体脂肪含量男性均比女性高(P<0.05),其中,41～50岁组中的男女差别最大,达11.1%.骨质疏松组FF与BMD呈负相关关系(γ=-0.6,P<0.01).结论 正常椎体骨髓脂肪含量随年龄而逐渐增加,~1H MRS可作为评价骨质量的新手段.     

椎体骨髓状况的磁共振波谱评估

目的 探讨椎体氢质子磁共振波谱对椎体骨髓状况的评估价值. 方法 对152例(30～80岁,平均58岁±14岁)女性志愿者进行腰椎MR检查.首先常规扫描矢状位T_2WI、T_1WI和横轴位T_2WI.MR常规扫描结束后采用单体素PRESS序列对L_2～L_4椎体进行波谱采集,相应谱线采用SAGE 7.0软件分析并计算相关椎体MRS定量指标.结果 随年龄增大椎体脂肪含量(FF%)逐步增加;椎体水峰线宽(LW)随年龄增加呈逐渐变窄趋势;椎体脂峰线宽未见明显变化趋势.结论氢质子磁共振波谱可以在常规腰椎磁共振基础上无创性地评估椎体骨髓变化状况.     

Reproducibility of MR perfusion and 1H spectroscopy of bone marrow

Purpose

To determine the reproducibility of proton (¹H) magnetic resonance (MR) spectroscopy and dynamic contrast‐enhanced MR imaging in a clinical setting for the assessment of marrow fat fraction and marrow perfusion in longitudinal studies.

Materials and Methods

In all, 36 subjects (17 females, 19 males, mean age 72.9 ± 2.9 years) who underwent MR spectroscopy and/or dynamic contrast‐enhanced perfusion imaging of the proximal femur were asked to return after 1 week for a repeat MR examination.

Results

Reproducibility of ¹H MR spectroscopy in all bone areas tested was high, ranging from 0.78–0.85, with the highest reproducibility being in the femoral head and lowest in the femoral neck. Reproducibility of paired perfusion measurements ranged from 0.59 (enhancement slope femoral head) to 0.98 (enhancement maximum acetabulum). Overall reproducibility of ¹H MR spectroscopy and dynamic contrast‐enhanced imaging tended to be best in areas with the highest inherent fat fraction or perfusion.

Conclusion

Reproducibility of ¹H MR spectroscopy or perfusion imaging is sufficiently high to warrant these techniques being applied to the longitudinal study of bone diseases. J. Magn. Reson. Imaging 2009;29:1438–1442. © 2009 Wiley‐Liss, Inc.     

MRS骨髓脂肪含量预测骨质疏松性髋部骨折的价值

目的 探讨股骨颈骨髓脂肪含量(BMF)对评估骨质疏松(OP)髋部脆性骨折风险的预测价值.方法 15例女性髋部骨折组(年龄68.3岁±9.4岁)及74例女性非骨折正常对照组(年龄61.6岁±10.3岁)行髋部双能X线吸收测量法扫描获取股骨颈骨密度(FN-BMD)及磁共振波谱(MRS)扫描测定BMF.采用受试者工作特征曲线(ROC)分析FN-BMD及BMF对预测髋部骨折风险的差异.结果 BMF与FN-BMD(r=-0.579)、年龄(r=0.460)、体重(r=-0.270)、体质量指数(BMI)(r=-0.239)存在轻-中度相关性(P均＜0.05),将年龄、体重、BMI作为协变量加以校正,BMF与FN-BMD之间的相关性依然存在(r=-0.374,P＜0.001).校正年龄、体重、BMI后,髋部骨折组FN-BMD较非骨折组低(P=0.020),BMF较非骨折组高(P=0.007).即使将FN-BMD加以校正,BMF在2组间差异仍存在统计学意义.FN-BMD及BMF判定髋部骨折的ROC曲线下面积分别为0.810、0.801,两者对骨折风险评估无统计学差异(P=0.894 5). BMF联合FN-BMD判定髋部骨折的R)C曲线下面积为0.826,与单独FN-BMD预测髋部骨折风险的能力无统计学意义(P=0.650 2).结论 股骨颈BMF是独立于FN-BMD决定髋部骨强度的预测因子,但BMF联合FN-BMD并不能提高对髋部脆性骨折的预测能力.     

Bone marrow edema syndrome

Bone marrow edema syndrome (BMES) refers to transient clinical conditions with unknown pathogenic mechanism, such as transient osteoporosis of the hip (TOH), regional migratory osteoporosis (RMO), and reflex sympathetic dystrophy (RSD). BMES is primarily characterized by bone marrow edema (BME) pattern. The disease mainly affects the hip, the knee, and the ankle of middle-aged males. Many hypotheses have been proposed to explain the pathogenesis of the disease. Unfortunately, the etiology of BMES remains obscure. The hallmark that separates BMES from other conditions presented with BME pattern is its self-limited nature. Laboratory tests usually do not contribute to the diagnosis. Histological examination of the lesion is unnecessary. Plain radiographs may reveal regional osseous demineralization. Magnetic resonance imaging is mainly used for the early diagnosis and monitoring the progression of the disease. Early differentiation from other aggressive conditions with long-term sequelae is essential in order to avoid unnecessary treatment. Clinical entities, such as TOH, RMO, and RSD are spontaneously resolving, and surgical treatment is not needed. On the other hand, early differential diagnosis and surgical treatment in case of osteonecrosis is of crucial importance.     

Localized MR 1H spectroscopy reveals alterations of susceptibility in bone marrow with hemosiderosis

A noninvasive investigation of the structure of hemopoietic bone marrow is based on the determination of the magnetic field distribution within small volume elements in vertebral bodies by localized ¹H MR spectroscopy. In patients with he-matological diseases the status of the bone marrow was found to considerably influence the homogeneity of the magnetic field in trabecular bone in vivo. The line widths of the ¹H signals were evaluated in follow-up studies during initial chemotherapy of eight patients with leukemia. lntraindividual comparison revealed significant broadening of the field distribution after a few weeks of cytotoxic treatment in five of the patients. Additionally, 19 patients after bone marrow transplantation showed significantly broader field distributions in the lipid signals than 13 matched healthy volunteers. These alterations of the microscopic field homogeneity were not caused by trabecular density effects. Iliac crest biopsies revealed high amounts of hemosiderin in the cases with broadened line widths. Ten of the 19 patients after bone marrow transplantation showed high amounts of hemosiderin and broad lines in the spectra. The content of hemosiderin of the other patients was not significantly increased.     

Gender and age groups interactions in the quantification of bone marrow fat content in lumbar spine using 3T MR spectroscopy: A multivariate analysis of covariance (Mancova)

Introduction

There is an age-related conversion of red to yellow bone marrow in the axial skeleton, with a gender-related difference less well established. Our purpose was to clarify the variability of bone marrow fat fraction (FF) in the lumbar spine due to the interaction of gender and age groups.

Methods

44 healthy volunteers (20 males, 30–65 years old and 24 females, 30–69 years old) underwent 3T magnetic resonance spectroscopy (MRS) and conventional MRI examination of the lumbar spine; single-voxel spectrum was acquired for each vertebral body (VB). After controlling body mass index (BMI), a two-way between-groups multivariate analysis of covariance (MANCOVA) assessed the gender and age group differences in FF quantification for each lumbar VB.

Results

There was a significant interaction between gender and age group, p = .017, with a large effect size (partial η² = .330). However the interaction explained only 33% of the observed variance. Main effects were not statistically significant. BMI was non-significantly related to FF quantification.

Conclusions

Young males showed a high FF content, which declined in the 4th decade, then increased the next 3 decades to reach a FF content just below the initial FF means. Females’ FF were low in the 3rd decade, depicted an accelerated increase in the 4th decade, then a gradual increase the next 3 decades to reach a FF content similar to males’ values. Our findings suggest that quantification of bone marrow FF using MRS might be used as a surrogate biomarker of bone marrow activity in clinical settings.     

Hematopoietic bone marrow in the adult knee: spin-echo and opposed-phase gradient-echo MR imaging

Hematopoietic bone marrow in the distal femur of the adult may be mistaken for a pathologic marrow process in magnetic resonance imaging of the knee. We investigated the incidence of hematopoietic marrow in the distal femur in a series of 51 adult patients and compared spin-echo (TR/TE in ms: 500/35, 2000/80) and opposed-phase gradient-echo (0.35 T, TR/TE in ms: 1000/30, = 75°) magnetic resonance images. Zones with intermediate to low signal intensity on T1-weighted spinecho and opposed-phase gradient-echo sequences representing hematopoietic marrow within high signal intensity fatty marrow were observed in 18 of the 51 patients. Five patterns of marrow signal reduction were identified; type 0: uniform high signal, i.e., no signal change; type I, focal signal loss; type II, multifocal signal loss without confluence; type III, confluent signal loss; and type IV, complete homogeneous reduction in marrow signal. Opposed-phase gradient-echo sequences demonstrated markedly greater red-yellow marrow contrast than conventional spin-echo sequences. Follow-up studies in three patients using a gradient-echo sequence with TE varying from 10 to 21 ms at 1-ms increments showed a cyclic increase and decrease in red and yellow marrow signal intensity depending on the TE. The contribution of intravoxel chemical shift effects on red-yellow marrow contrast in opposed-phase gradient-echo images was verified by almost complete cancellation of the TE-dependent marrow signal oscillation with use of a chemically selective pulse presaturating the water protons.Hematopoietic marrow in the adult distal femur in the absence of hematologic abnormalities is found primarily in women of menstruating age. It may be residual and may represent a biologic variation in the normal adult pattern of red-yellow marrow distribution. Reconverted red marrow appears to be related to increased erythrocyte demand. Residual and reconverted red marrow should not be mistaken for bone marrow malignancy. Opposed-phase gradient-echo imaging is easily implemented and appears ideally suited to monitor the distribution of hematopoietic marrow as a function of age and erythrocyte demand in vivo.