MR多回波Dixon脂肪定量技术在脊柱病变的应用和展望

【摘要】脊柱病变常引起椎体脂肪含量的变化,MR多回波Dixon定量（modified Dixon quantification,mDixon-Quant）技术是一项可靠的评估骨髓病变的磁共振成像技术,可协助对脊柱病变的诊断,本文综述了近几年来mDixon-Quant技术在脊柱病变中的临床应用和研究进展。     

基于Dixon技术的MRI评估体模、正常志愿者及跟腱痛病人的肌肉脂肪含量:与肉眼评估小腿肌肉质量对比

目的与MRS及肉眼评估肌肉脂肪含量方法比较,基于Dixon技术的双点MR成像方法对体模、正常志愿者及跟腱痛病人的肌肉脂肪含量的定量研究。方法应用     

心包脂肪影像学的研究进展

心包脂肪是冠状动脉和心脏周围的脂肪组织。其中,心外膜脂肪组织和血管周围脂肪组织与心血管系统密切相关,参与了心血管疾病(CVD)的重要病理生理过程。目前可通过心脏超声、CT、MRI、正电子发射体层成像(PET)及影像组学等影像方法无创检测心包脂肪的变化。就心包脂肪参与CVD的生物学机制、心包脂肪影像学评估技术的进展及在冠状动脉疾病、心房颤动和心力衰竭中的临床应用价值予以综述。     

脂肪抑制技术在骨骼肌肉疾病MRI诊断中的应用

脂肪抑制技术在骨骼肌肉疾病ＭＲＩ诊断中的应用王霞郎志谨韩玉成焦天民王绍武王峰ＭＲＩ是目前唯一能够对骨髓变化作出诊断的检查方法，尤其是脂肪抑制成像技术的应用，提高了骨骼肌肉系统疾病的诊断水平。笔者在３８例骨骼肌肉系统疾病的ＭＲＩ检查中应用了脂肪抑制技术...     

MR灌注成像在骨髓血流灌注中的研究进展

多数骨髓疾病伴有血流灌注的变化,MR灌注成像能够提供骨髓微循环信息,可在早期监测骨髓血流灌注的变化,有助于疾病的诊断及疗效评估。目前多种MR成像技术已用于骨髓血流灌注的评估,包括动态增强MRI (DCE-MRI)、动脉自旋标记成像(ASL)、体素内不相干运动扩散加权成像(IVIM-DWI)以及血氧水平依赖(BOLD)MRI等。综述上述MR灌注成像技术应用在骨质疏松、骨关节炎、骨肿瘤和肿瘤样病变、血液病等评估其骨髓血流灌注作用及研究进展。     

IDEAL-IQ定量评价2型糖尿病患者器官脂肪沉积的研究进展

随着生活水平的提高及生活方式的改变,糖尿病成为一个全球性的公众健康问题。糖尿病代谢紊乱可导致内脏脂肪沉积,因此组织中的脂肪含量是评估疾病状态的一个重要生物标志物。通过3.0 T MRI非对称回波最小二乘估算法迭代水和脂肪分离技术(IDEAL-IQ)对2型糖尿病患者肝脏、胰腺、肾脏及椎体内的脂肪进行定量分析,对病情评估、治疗方案的选择具有一定的指导意义。就MRI IDEAL-IQ序列在糖尿病患者腹部脏器及椎体骨髓脂肪定量中的研究进展及临床价值做一综述。     

胰腺脂肪定量的CT和MRI研究进展

近年来,越来越多的研究证实胰腺脂肪浸润与肥胖、高血压、糖尿病、高血脂以及胰腺癌、胰腺癌淋巴结转移、术后胰瘘等疾病有关。胰腺脂肪定量对这些相关疾病的预防、早期诊断、治疗、疗效评价以及预后评估等都具有重要的临床价值。CT和MRI是准确、安全、快速地诊断和定量成人及儿童胰腺脂肪浸润的影像方法。就胰腺脂肪浸润的影像诊断及胰腺脂肪定量的CT和MRI研究进展予以综述。     

应用空间谱激励快速脂肪选择性GRE成像评估肥胖青少年的脂肪肝:与光谱结果的定量数据对比研究

目的测试空间谱激励快速脂肪选择性GRE成像这一技术在评估肥胖青少年肝内脂肪(IHL)含量的可行性。方法单次屏气内行脂肪选择性MR成像(1.5T),记录有代表     

磁共振波谱成像评估初发2型糖尿病患者骨髓脂肪含量

目的探讨磁共振波谱成像(MRS)定量评估初发2型糖尿病(T2DM)骨髓脂肪含量变化及其与胰岛素抵抗的相关性。方法初发T2DM患者及年龄匹配的正常对照组(n=32/组)行双能X线骨密度测定及股骨颈MRS扫描,分别获得骨密度(BMD)及骨髓脂肪分数(FF)。检查2组研究对象空腹血糖(FPG)、糖化血红蛋白(Hb A1c)、胰岛素(FINS)及血脂指标(TC、TG、HDL-C、LDL-C),利用稳态模式评估法评价胰岛素抵抗(HOMA-IR)。结果初发T2DM组BMD值与对照组无统计学差异。初发T2DM组FF值显著高于正常对照组(P0.001),校正糖代谢、脂代谢及BMD值,2组间FF值仍存在统计学差异(F值=16.763,P=0.012)。FF与HOMA-IR呈中度正相关性(r=0.683,P0.001),校正BMI,FF与HOMA-IR仍然存在正相关性(r=0.592,P=0.018)。结论初发T2DM患者骨髓脂肪增高,骨髓脂肪增多可能是胰岛素抵抗的影响因素之一。     

改良双回波成像对肝脏脂肪测量的探讨

目的探讨改良双回波成像技术对肝脏脂肪含量的定量分析及影响因素。方法应用30°小翻转角射频脉冲,通过短回波时间(TE:2.1ms)成像,校正同相位图像信号强度,改良双回波成像技术。双回波技术、改良双回波技术及氢质子波谱成像技术(~1H-MRS)分别测量肝脏左右叶脂肪含量,计算脂肪酸含量分数%F、%F_(corrected)与%F_(MRS);以%FMRS为标准,评价三种方法测量脂肪酸含量分数、比较其相关性及一致性。结果三种方法测量脂肪酸含量分数差异无统计学意义(P均0.05)。%F、%F_(corrected)与%F_(MRS)均呈正相关,相关系数r分别为0.876、0.911,(P均0.0001);Kappa值分别为0.865(95%可信区间0.676～0.903)、0.901(95%可信区间0.816～0.937),一致性均较好;%F_(corrected)与%F_(MRS)的一致性较%F与%F_(MRS)的高。结论改良双回波成像技术能够纠正T_1偏倚,减少T_2*衰减及脂肪峰多重性/J耦合的影响;能更准确半定量评价肝脏脂肪酸含量。     

Evaluation of vertebral bone marrow fat content by chemical-shift MRI in osteoporosis

Objective  

To quantitatively evaluate vertebral bone marrow fat content and investigate its association with osteoporosis with chemical-shift magnetic resonance imaging (CS-MRI).     

Diagnosis and triage of a patient with an extra-osseous fat fluid level

Extra-osseous fat fluid level is rarely seen in osteomyelitis, with only three magnetic resonance imaging (MRI) cases previously reported in the literature. The rarity of this finding is probably secondary to the extensive necrosis of bone marrow that needs to occur at a rapid phase for the fat to accumulate. However, an extra-osseous fat fluid level is a specific diagnostic sign of osteomyelitis in cases with otherwise equivocal imaging findings and should be reported as such, especially when associated with medullary bone destruction and in the absence of trauma.     

Bone mineral and other bone components in vertebrae evaluated by QCT and MRI

To evaluate the usefulness of assessing bone components using magnetic resonance imaging (MRI), the contributions of bone components, including mineral, fat and collagen, to bone mineral density (BMD) and T1 relaxation time (T1) were studied using phantoms. Excised human vertebrae were also evaluated by quantitative computed tomography (QCT) and MRI. T1 was shortened with increasing quantities of fat and collagen. In water, T1 was significantly affected by bone density, while in oil, T1 became slightly longer as bone density increased. The presence of fat and collagen caused under- and overestimations of BMD, respectively. There was good correlation between T1 and BMD in osteoporotic vertebrae and the vertebrae with long T1 showed an increased content of hematopoietic marrow and/or abnormally increased bone mineral. It was concluded that the experimental data showed that MRI can contribute to the assessment of bone quality.     

A technique for assessment of bone marrow composition using magnetic resonance phase interference at low field

In disorders which involve the bone marrow, the fat/water ratio of the marrow is often an indicator of the progress of disease. A noninvasive method of monitoring this ratio in bone marrow could be clinically useful. We have investigated a method of bone marrow assessment, using magnetic resonance imaging at low field (0.064 Tesla). The method has been tested using calibrated phantoms; we also present results from normal human subjects.     

Normal spinal bone marrow in adults: dynamic gadolinium-enhanced MR imaging

PURPOSE: To determine the patterns of dynamic enhancement of normal spinal bone marrow in adults at gadolinium-enhanced magnetic resonance (MR) imaging and the changes that occur with aging. MATERIALS AND METHODS: Dynamic contrast material-enhanced MR imaging of the thoracolumbar spine was performed in 71 patients. The maximum percentage of enhancement (Emax), enhancement slope, and enhancement washout were determined from bone marrow enhancement time curves (ETCs). The bone marrow signal intensity on T1-weighted spin-echo MR images was qualitatively classified into three grade categories. Quantitative ETC values were correlated with patient age and bone marrow fat content grade. Statistical analysis included mean t test comparison, analysis of variance, and regression analysis of the correlations between age and quantitative MR parameters. RESULTS: Emax, slope, and washout varied widely among the patients. Emax values were obtained within 1 minute after contrast material injection and ranged from 0% to 430%. Emax values were significantly higher in patients younger than 40 years than in those aged 40 years or older (P <.001). These values decreased with increasing age in a logarithmic relationship (r = 0.71). Emax values decreased as fat content increased, but some overlap among the fat content grades was noted. Analysis of variance revealed that Emax was significantly related to age (younger than 40 years vs 40 years or older) (P <.001) and fat content grade (P <.001) but not significantly related to sex. CONCLUSION: Dynamic contrast-enhanced MR imaging patterns of normal spinal bone marrow are dependent mainly on patient age and fat content.     

Systemic bone marrow disorders: characterization with proton chemical shift imaging

In a prospective clinical study, 26 patients (22 with malignant lymphoma and 4 with myelofibrosis) and 9 healthy volunteers were examined by conventional magnetic resonance and proton chemical shift imaging (CSI; modified Dixon method). On the basis of the CSI data, a quantitative evaluation of the relative fat and water signal fractions in regions of interest of the femur, pelvis, and spine was performed. In 16 of 17 patients with biopsy-proven bone marrow disorders, CSI revealed a significant reduction in the fat fraction of the bone marrow relative to that of normal volunteers. The visual assessment could detect only 14 of the 17 pathological cases.     

Bone infarction and fat island appearing as local defects in radionuclide bone marrow imaging

Parallel studies of radionuclide bone marrow imaging and bone scanning are helpful in the early diagnosis of skeletal metastasis. In bone marrow imaging, most lesions are observed as a local defect. We had two cases of nonmetastatic lesions which appeared as local defects in bone marrow imaging. The first case was a male Hodgkin's disease patient, aged 48, who had been treated with frequent chemotherapy, including the administration of a large quantities of steroids. He complained of slight pain in the left shoulder. Without increased uptake in bone scanning, abnormal accumulation of 67Ga-citrate and a local defect in bone marrow imaging appeared, corresponding to localization of the pain. Suspecting bone marrow metastasis, we performed magnetic resonance imaging (MRI). An area of slightly decreased intensity in T1-weighted spin-echo images and lower intensity than fat tissue in T2-weighted images were observed, although it was slightly enhanced by Gd-DTPA. This lesion was diagnosed by biopsy as a bone infarction. The second case was that of a 69-year-old male lung cancer patient. Though no abnormality was revealed by bone scanning or 67Ga-citrate scintigraphy, an apparent defect at the 10th thoracic vertebra was observed in bone marrow imaging. It was not accompanied by pain. MRI was also performed in this case. This was depicted as a clearly defined high intensity area. This was diagnosed as a fat island, and no change has been seen in the seven months of follow up. In conclusion, it is necessary to consider the possibility of nonmetastatic lesions, when local defects appear in bone marrow imaging performed on cancer patients.     

Quantitative chemical shift imaging of vertebral bone marrow in patients with Gaucher disease.

To evaluate extent of bone marrow involvement and disease severity in Gaucher patients, results of modified Dixon quantitative chemical shift imaging (QCSI) of the lumbar spine were correlated with quantitative analysis of marrow triglycerides and glucocerebrosides and with quantitative determination of splenic volume at magnetic resonance (MR) imaging. High-field-strength MR spectra of surgical marrow specimens were dominated by a single fat and a water peak, validating use of QCSI. QCSI showed average vertebral marrow fat fractions of 10% +/- 8 in Gaucher patients (normal adult averages, 29% +/- 6). Relaxation times for lipid and water approximated normal averages; bulk T1 values were significantly longer, reflecting decreased marrow fat. Glucocerebroside concentrations were higher in Gaucher marrow and inversely correlated with triglyceride concentrations. Extent of marrow infiltration determined by fat fraction measurements correlated with disease severity measured by splenic enlargement. These results show that as Gaucher cells infiltrate bone marrow and displace normal marrow adipocytes, bulk T1 increases due to the higher T1 of water compared with that of fat. QCSI provides a sensitive, noninvasive technique for evaluating bone marrow involvement in Gaucher disease.     

Chemical shift imaging of bone marrow: preliminary experience

A phase-contrast method of chemical shift imaging was used to evaluate bone marrow in normal volunteers and in patients with metabolic, inflammatory, traumatic, and neoplastic disorders. Five normal volunteers were examined in order to obtain preliminary data on normal patterns of signal intensity in hematopoietic and fatty marrow using both conventional magnetic resonance imaging and proton chemical shift imaging. Normally, hematopoietic marrow yields low signal intensity on phase-contrast images; pathologic conditions affecting hematopoietic marrow typically result in increased signal intensity due to either accumulated lipid or water. Because of its high fat content, yellow marrow normally yields high signal intensity on phase-contrast images, whereas abnormal conditions usually result in decreased phase-contrast signal intensity due to increased tissue water. Proton chemical shift imaging is likely to be a valuable supplement to standard magnetic resonance imaging techniques in the study of bone marrow in vivo.     

Vertebral bone mineral density, marrow perfusion, and fat content in healthy men and men with osteoporosis: dynamic contrast-enhanced MR imaging and MR spectroscopy

PURPOSE: To prospectively use hydrogen 1 (1H) magnetic resonance (MR) spectroscopy and dynamic contrast material-enhanced MR imaging to measure vertebral body marrow fat content and bone marrow perfusion in older men with varying bone mineral densities as documented with dual x-ray absorptiometry (DXA). MATERIALS AND METHODS: This study had institutional review board approval, and all participants provided informed consent. DXA, 1H MR spectroscopy, and dynamic contrast-enhanced MR imaging of the lumbar spine were performed in 90 men (mean age, 73 years; range, 67-101 years). Vertebral marrow fat content and perfusion (maximum enhancement and enhancement slope) were compared for subject groups with differing bone densities (normal, osteopenic, and osteoporotic). The t test was used for comparisons between groups, and the Pearson test was used to determine correlation between marrow fat content and perfusion indexes. RESULTS: Eight subjects were excluded, yielding a final cohort of 82 subjects (mean age, 73 years; range, 67-101 years) that included 42 subjects with normal bone density (mean T score, 0.8 +/- 1.1 [standard deviation]), 23 subjects with osteopenia (mean T score, -1.6 +/- 0.4), and 17 subjects with osteoporosis (mean T score, -3.2 +/- 0.5). Vertebral marrow fat content was significantly increased in subjects with osteoporosis (mean fat content, 58.23% +/- 7.8) (P = .002) or osteopenia (mean fat content, 55.68% +/- 10.2) (P = .034) compared with that in subjects with normal bone density (50.45% +/- 8.7). Vertebral marrow perfusion indexes were significantly decreased in osteoporotic subjects (mean enhancement slope, 0.78%/sec +/- 0.3) compared with those in osteopenic subjects (mean enhancement slope, 1.15%/sec +/- 0.6) (P = .007) and those in subjects with normal bone density (mean enhancement slope, 1.48%/sec +/- 0.7) (P < .001). CONCLUSION: Subjects with osteoporosis have decreased vertebral marrow perfusion and increased marrow fat compared with these parameters in subjects with osteopenia. Similarly, subjects with osteopenia have decreased vertebral marrow perfusion and increased marrow fat compared with these parameters in subjects with normal bone density.