中老年人群肝脏脂肪含量与骨密度的相关性研究

目的探讨中老年人群肝脏脂肪含量与腰椎骨密度的相关性。方法2016年3月至6月纳入184名北京社区中老年居民,其中男68名、女116名,对其进行腹部MRI mDIXON-Quant序列扫描和腰椎定量CT(QCT)扫描,测量肝脏脂肪含量和腰1~腰3椎体骨密度。根据肝脏脂肪含量的四分位数分为四组,采用单因素方差分析比较不同肝脏脂肪含量组间骨密度及身高、体重、体质量指数(BMI)、腰围、臀围等变量的差异,并对肝脏脂肪含量和骨密度做Spearman相关性分析和偏相关分析。结果随着肝脏脂肪含量的升高,BMI、腰围呈上升趋势,而腰椎骨密度逐渐降低。肝脏脂肪含量与腰椎骨密度呈低度负相关(r=-0.203,P=0.003),校正年龄、体重之后,仍呈负相关(r=-0.291,P<0.001),男性中r=-0.283(P=0.021),女性r=-0.210(P=0.025)。结论中老年人群肝脏脂肪含量与腰椎骨密度呈低度负相关。     

Non-invasive quantification of hepatic fat fraction by fast 1.0, 1.5 and 3.0 T MR imaging

INTRODUCTION: Even mild hepatic steatosis in a split liver donor may cause general liver failure and death in the donor. So far, CT density measurements or percutaneous biopsy is used to determine the presence of hepatic steatosis. Magnetic resonance imaging (MRI) may be an elegant method of non-invasive and non-radiation quantification of hepatic fat content. METHODS: Fast gradient echo (GRE) technique was used to discriminate between fat and water spins. Echo time (TE) was adjusted for field strength dependent in-phase and out-of-phase states at 1.0, 1.5 and 3.0 T. Continuous MR signal transition from 100% water to 100% fat was investigated using a wedge water-oil phantom, which was positioned in such a way, that no spatial resolution occurred, thereby combining water and fat in one slice. RESULTS: Using the phantom, a significant difference for a 5% difference in fat content was demonstrated in the range from 20 to 80% fat content (p<0.05) for all tested field strengths. In 25 patients MRI data were correlated with the percentage of fat determined by histologic evaluation of a CT-guided liver biopsy. Using the linear correlation calculated from the MRI phantom data at 1.0 T, we determined the liver fat from each patient's MRI measurements. Comparison of these data with the histologic quantified fat fraction of liver tissue showed a strong correlation (r(2)=0.93 for TE 6 ms and r(2)=0.91 for TE 10 ms). CONCLUSION: The described method can be used to determine the presence of hepatic steatosis of >10% with p<0.05.     

Magnetic resonance imaging and spectroscopy for monitoring liver steatosis

PURPOSE: To compare noninvasive MRI and magnetic resonance spectroscopy (MRS) methods with liver biopsy to quantify liver fat content. MATERIALS AND METHODS: Quantification of liver fat was compared by liver biopsy, proton MRS, and MRI using in-phase/out-of-phase (IP/OP) and plus/minus fat saturation (+/-FS) techniques. The reproducibility of each MR measure was also determined. An additional group of overweight patients with steatosis underwent hepatic MRI and MRS before and after a six-month weight-loss program. RESULTS: A close correlation was demonstrated between histological assessment of steatosis and measurement of intrahepatocellular lipid (IHCL) by MRS (r(s) = 0.928, P < 0.0001) and MRI (IP/OP r(s) = 0.942, P < 0.0001; FS r(s) = 0.935, P < 0.0001). Following weight reduction, four of five patients with >5% weight loss had a decrease in IHCL of >or=50%. CONCLUSION: These findings suggest that standard MRI protocols provide a rapid, safe, and quantitative assessment of hepatic steatosis. This is important because MRS is not available on all clinical MRI systems. This will enable noninvasive monitoring of the effects of interventions such as weight loss or pharmacotherapy in patients with fatty liver diseases.     

Fatty liver. Chemical shift phase-difference and suppression magnetic resonance imaging techniques in animals, phantoms, and humans.

In vitro animal and human models were used to evaluate the potential of chemical shift magnetic resonance imaging (MRI) for assessing fatty liver. Phantoms of varying fat content were created from mayonnaise-agar preparations. Fatty liver was induced in eight rats by feeding them ethanol for three to six weeks (36% of total calories), whereas eight control rats were fed a normal diet. T1-weighted in-phase and opposed-phase MR images were obtained of the phantoms animals, and 28 human subjects. Additional images obtained in animals included long TR images with in-phase and opposed-phase technique, and hybrid chemical shift water and fat suppression. The rats were killed and histologic status was graded blindly by a hepatopathologist as normal, mild, moderate, or severe fatty change, for correlation with MR grading. Quantitative analysis of MR images included fat signal fraction for animals, and relative signal decrease between in-phase and opposed-phase images for phantom and human data. Phantom in-phase signal increased linearly with respect to fat content, whereas opposed-phase signal decreased linearly. MRI and histologic grading of rat livers were highly correlated, especially when based on water suppression images (r = 0.91, P = .0001). Opposed-phase images were also highly correlated, while fat suppression images were less effective. There was no overlap between MR-derived fat fractions for control (2.6%-5.7%) versus ethanol-fed rats (7.7%-17.9%, P = .0002). Human liver considered to be fatty by visual inspection (n = 8) had higher relative signal decrease than nonfatty liver (n = 22) (P less than .001). Phantom, animal, and human data demonstrate that comparison of T1-weighted in-phase and opposed-phase images is both practical and sensitive in the detection and grading of fatty liver.     

Interleaved water and fat imaging and applications to lipid quantitation using the gradient reversal technique

PURPOSE: To implement and evaluate the gradient reversal-based chemical shift imaging technique to obtain qualitative and quantitative spatially-registered fat and water images with high imaging efficiency at very high field. MATERIALS AND METHODS: A multiecho gradient reversal-based sequence allowing interleaved water-fat imaging during a single acquisition and quantitation of fat/water content is presented. The sequence was optimized and implemented at 11.7T. The quantitation was verified with water-fat phantoms and applied to lipid measurement in an in vivo mouse model. RESULTS: Results from phantoms, in vivo lipid measurement in mouse liver and hind limb muscle, and ex vivo rat knee imaging experiments demonstrated the robustness and high selectivity of this technique for interleaved and quantitative water and fat imaging at very high field. CONCLUSION: The proposed MRI technique permits interleaved water and fat imaging, with which spectrally well-separated water and fat images at the identical slice locations could be obtained in a single acquisition without increasing scan time. The technique could be used for in vivo quantitative mapping of lipid content and applied to investigations using small animal experiment models.     

Liver-vessel cancellation artifact on in-phase and out-of-phase MRI imaging: a sign of ultra-high liver fat content

Purpose:

To describe a new MRI sign, the liver‐vessel cancellation artifact, on In‐Phase and Out‐of‐Phase gradient‐echo sequences related to ultra‐high liver fat content (>90%) by qualitative histology.

Materials and Methods:

Institutional review board approval was obtained for this retrospective HIPAA‐compliant study with waived informed consent. Patients with liver steatosis were searched in MRI (n = 195) and pathology (n = 116) databases between January 1, 2008, and June 20, 2010. Two readers blindly reviewed all MR images for the presence of the liver‐vessel cancellation sign. Cross‐reference of patients with biopsy‐proven steatosis and MRI within one month was performed (n = 54; 25 males, 29 females; mean age 41.0 ± 18.9), with a population of 6 patients with ultra‐high liver fat content (1 male, 5 females; mean age 15.5 ± 11.2). Performance diagnostic tests, including sensitivity and specificity, were performed.

Results:

Liver‐vessel cancellation sign was present in all patients with ultra‐high liver fat content but in none of the remaining patients. Calculated sensitivity and specificity for the detection of ultra‐high liver fat content with this sign were 100% (95% confidence interval [CI]: 69.1–100%) and 100% (95% CI: 98.4–100%), respectively.

Conclusion:

The presence of liver‐vessel cancellation artifact around intra‐hepatic vessels is a feature of ultra‐high liver fat content. J. Magn. Reson. Imaging 2012;35:1112‐1118. © 2011 Wiley Periodicals, Inc.     

脂肪肝单能CT定量诊断的实验研究

目的　研究兔脂肪肝模型中肝脏脂肪含量与肝脏CT值之间的相互关系 ,为CT定量诊断脂肪肝提供理论依据。材料与方法　对造成不同程度脂肪肝的实验组 16只家兔和正常对照组 4只健康家兔分别行单能CT检查 ,测定肝脏的CT值。心脏穿刺取血 ,测定血清丙氨酸转氨酶 (ALT)、天门冬氨酸转氨酶 (AST)、碱性磷酸酶 (ALP)的水平。对肝脏进行组织学检查 ,用图像分析系统测量并计算肝脏脂滴占肝脏单位体积的百分比 (VP值 )。结果　实验组的VP值与CT值之间在统计学上有显著性意义的线性负向相关关系 (r =- 0 .90 ,t=7.5 4 ,P <0 .0 0 1) ;重度脂肪肝组血清ALT、AST、ALP水平较正常组、轻度脂肪肝组、中度脂肪肝组高 (P <0 .0 1)。结论　单能CT的肝脏CT值可以定量诊断脂肪肝的肝脏脂肪含量 ,判断脂肪肝的程度 ,效果优于血清ALT、AST、ALP等指标     

R2 relaxometry with MRI for the quantification of tissue iron overload in beta-thalassemic patients

PURPOSE: To evaluate the usefulness of a time-efficient MRI method for the quantitative determination of tissue iron in the liver and heart of beta-thalassemic patients using spin-spin relaxation rate, R2, measurements. MATERIALS AND METHODS: Images were obtained at 1.5 T from aqueous Gd-DTPA solutions (0.106-8 mM) and from the liver and heart of 46 beta-thalassemic patients and 10 controls. The imaging sequence used was a respiratory-triggered 16-echo Carr-Purcell-Meiboom-Gill (CPMG) spin-echo (SE) pulse sequence (TR = 2000 msec, TE(min) = 5 msec, echo spacing (ES) = 5 msec, matrix = 192 x 256, slice thickness = 10 mm). Liver iron concentration (LIC) measurements were obtained for 22 patients through biopsy specimens excised from the relevant liver segment. Biopsy specimens were also evaluated regarding iron grade and fibrosis. Serum ferritin (SF) measurements were obtained in all patients. RESULTS: A statistically significant difference was found between patients and healthy controls in mean liver (P < 0.004) and myocardium (P < 0.004) R2 values. The R2 values correlated well with Gd DTPA concentration (r = 0.996, P < 0.0001) and LIC (r = 0.874, P < 0.0001). A less significant relationship (r = 0.791, P < 0.0001) was found between LIC measurements and SF levels. R2 measurements appear to be significantly affected (P = 0.04) by different degrees of hepatic fibrosis. The patients' liver R2 values did not correlate with myocardial R2 values (r = 0.038, P < 0.21). CONCLUSION: Tissue iron deposition in beta-thalassemic patients may be adequately quantified using R2 measurements obtained with a 16-echo MRI sequence with short ES (5 msec), even in patients with a relatively increased iron burden.     

Comparison of fat quantification methods: a phantom study at 3.0T

PURPOSE: To compare different imaging methods with single-voxel MR spectroscopy (MRS) for the quantification of fat content in phantoms at 3.0T. MATERIALS AND METHODS: Imaging and spectroscopy was performed on a GE Signa system. Eleven novel homogeneous fat-water phantoms were constructed with variation in fat content from 0% to 100%. These were imaged using three techniques and compared with single-voxel non-water-suppressed MRS. Pixel-by-pixel maps of fat fraction were produced and mean values compared to MRS-determined measurements. Preliminary in vivo examinations were subsequently performed in the breast and spine to compare the best imaging technique with MRS. RESULTS: All imaging methods significantly correlated with MRS (P < 0.001): IDEAL (r(2) = 0.985), IOP (r(2) = 0.888), WS (r(2) = 0.939), and FS (r(2) = 0.938). In addition, IDEAL provided artifact-free maps of fat fraction with superior uniformity. In vivo results using IDEAL produced values that were between 9% to 16% of the corresponding MRS values. CONCLUSION: This work demonstrates that imaging may be utilized as a high-resolution alternative to MRS for the quantification of fat content. In the future we intend to replace MRS with IDEAL in our clinical studies involving fat measurement.     

Fat quantification using three-point dixon technique: in vitro validation

RATIONALE AND OBJECTIVES: To test the repeatability, reproducibility and accuracy of the three-point Dixon (3PD) sequence for estimating true fat volume ratios using a fat/water phantom. MATERIALS AND METHODS: A phantom, constructed from test tubes of varying fat content, was imaged using the 3PD sequence on a 1.5T MRI scanner by two operators four times each. Fat volume ratios were calculated from these images and compared with true fat volumes. RESULTS: Measures of fat volume ratios calculated from the 3PD MR images correlated strongly with values for true fat volumes (r = 0.96). CONCLUSION: The 3PD technique was found to be highly reproducible and accurate, and may be useful for in vivo quantification of fat in lean tissues, such as the liver, pancreas or skeletal muscle.     

Assessment of the variations in fat content in normal liver using a fast MR imaging method in comparison with results obtained by spectroscopic imaging

A recently published Dixon-based MRI method for quantifying liver fat content using dual-echo breath-hold gradient echo imaging was validated by phantom experiments and compared with results of biopsy in two patients (Radiology 2005;237:1048-1055). We applied this method in ten healthy volunteers and compared the outcomes with the results of MR spectroscopy (MRS), the gold standard in quantifying liver fat content. Novel was the use of spectroscopic imaging yielding the variations in fat content across the liver rather than a single value obtained by single voxel MRS. Compared with the results of MRS, liver fat content according to MRI was too high in nine subjects (range 3.3–10.7% vs. 0.9–7.7%) and correct in one (21.1 vs. 21.3%). Furthermore, in one of the ten subjects the MRI fat content according to the Dixon-based MRI method was incorrect due to a (100-x) versus x percent lipid content mix-up. The second problem was fixed by a minor adjustment of the MRI algorithm. Despite systematic overestimation of liver fat contents by MRI, Spearman’s correlation between the adjusted MRI liver fat contents with MRS was high (r = 0.927, P < 0.001). Even after correction of the algorithm, the problem remaining with the Dixon-based MRI method for the assessment of liver fat content,is that, at the lower end range, liver fat content is systematically overestimated by 4%.     

多回波Dixon技术在非酒精性脂肪肝中脂肪定量及铁沉积的应用进展

非酒精性脂肪性肝病(NAFLD)病人的肝脏脂肪含量和铁过载与其病情的进展密切相关。基于MRI的水脂分离技术即Dixon技术不仅可以测量肝脏脂肪分数,还可得出R2*弛豫图来反映铁沉积情况,其具有无创性、可重复性等优点,在NAFLD的早期诊断、病情评估及疗效评价中具有重要的临床价值。就多回波Dixon技术在肝脏脂肪定量及铁沉积中的研究进展予以综述。     

T2*校正水脂分离MRI评价慢性肾脏病非透析患者骨髓脂肪含量变化

目的 探讨T2*校正水脂分离序列定量慢性肾脏病(CKD)非透析患者腰椎骨髓脂肪分数(MFF)及其与骨代谢指标的相关性.方法 78例CKD患者按肾小球滤过率(eGFR)分为5组,所有患者行T2*校正3D VIBE水脂分离扫描,计算MFF并评价2次重复扫描的精确性及不同观察者测量MFF的一致性.检测血钙、磷、碱性磷酸酶、骨钙素、甲状旁腺素及25(OH)D3.结果 MRI重复扫描MFF变异系数为2.37％,观察者间测定MFF组内相关系数(ICC)为0.901,2位观察者内ICC分别为0.959、0.948.MFF在各期CKD中均存在统计学差异,与血钙、磷、甲状旁腺素、碱性磷酸酶及骨钙素比较,MFF值变化出现较早.MFF与血磷(r=3.011,P=0.003)、甲状旁腺素水平(r=3.852,P＜0.001)呈正相关性,与血钙(r=-2.767,P=0.017)、25(OH)D3(r=-6.032,P＜0.001)、eGFR(r=-5.104,P＜0.001)呈负相关性.多元线性回归分析,25(OH)D3 (Sβ=-0.343)及eGFR(Sβ=-0.284,P均＜0.001)是MFF的独立影响因素.结论 CKD非透析患者存在骨髓脂肪浸润,T2*校正水脂分离MRI是定量CKD骨髓脂肪含量的有效手段.     

Hepatic lipid accumulation in healthy subjects: a comparative study using spectral fat-selective MRI and volume-localized 1H-MR spectroscopy.

Fat-selective MRI was applied to assess the amount and spatial distribution of hepatic lipids (HL) in healthy subjects. The results were compared with those obtained by localized 1H-MR spectroscopy (MRS). Ninety subjects (23-63 years old) underwent single-slice fat-selective MRI with spatial-spectral excitation and volume-localized spectroscopy at 1.5 T. HLs were analyzed in ventral and dorsal regions of interest (ROIs) of the liver in fat-selective images. Spectra were evaluated using the integral signal of methylene and methyl signals. The fat-selective images showed smooth and homogeneous distribution of HL over the entire cross section of the liver. There was, however, a marked interindividual variability in the amount of HL. MRS revealed a lipid signal fraction between 0.5% and 39.3%. The fat content in the ROIs in images correlated well with the spectroscopic results (r >or= 0.95). Both techniques provide sufficient sensitivity for a reliable and quantitative assessment of liver steatosis in subjects without liver disease. 1H-MRS has a higher sensitivity compared to MRI, especially for small amounts of HL, which may be of interest for metabolic interventions. Fat-selective images provide more spatial information about fat distribution, which makes this technique suitable for clinical imaging of patients with liver disease.     

Selective missing pulse steady state free precession (MP-SSFP): inner volume and chemical shift selective imaging in a steady state sequence

PURPOSE: To examine new sequences that restrict acquisition of spins to those excited by both of the RF pulses in missing pulse steady state free precession (MP-SSFP) MRI. MATERIALS AND METHODS: New MP-SSFP sequences were created by replacing one of the slice selective pulses (SSPs) with an orthogonal SSP for inner volume imaging, and with a chemical shift selective (CHESS) pulse for chemical shift imaging. The inner volume sequence was applied to a reduced field of view at the center of a resolution phantom; resulting images were evaluated for differences in the aliased signal. The CHESS sequence was applied to volunteers, as well as to and fat, water, and acetic acid phantoms. Results were evaluated with SNR measurements. RESULTS: The inner volume sequence eliminated the aliased signal, while nonselected fat and water levels were suppressed to that of noise by the CHESS sequence. CONCLUSION: Results suggest a novel steady state technique for rapid inner volume or chemical shift imaging.     

Imaging of liver function with dedicated animal dynamic pinhole scintigraphy in rats

BACKGROUND: Non-invasive evaluation of liver function in small animal models remains a challenge. Hepatobiliary scintigraphy (HBS) enables the assessment of total and regional liver function for both uptake and excretion in larger species. AIM: To validate quantitative liver function assessment with dedicated pinhole HBS in rats. To illustrate an application of this technique, liver function was assessed in two surgical models of liver regeneration. METHODS: HBS was performed in 12 rats with 99mTc-mebrofenin on a dedicated animal pinhole gamma camera. The hepatic uptake rate was calculated twice by different observers to establish a normal range and the reproducibility of processing. The degree of hepatocellular injury and synthesis function were assessed by serum liver tests. Liver function was compared with liver weight. Subsequently, three groups of three rats were scanned on three separate days to assess the reproducibility of HBS. Finally, to illustrate an application of this technique, liver function was assessed in two surgical models of liver regeneration. RESULTS: HBS in rats was feasible without mortality. The mean liver uptake rate was 77.29+/-1.29% . min(-1). Calculation of the liver uptake (% . min(-1)) was highly reproducible (r=0.95, P<0.001). There was a good correlation between liver weight and function measured by HBS at baseline and after partial resection (r=0.94, P<0.001). CONCLUSION: HBS offers a unique combination of functional liver uptake and excretion assessment with the ability to determine the liver function reserve before and after an intervention in rats.     

Low-carbohydrate diet induced reduction of hepatic lipid content observed with a rapid non-invasive MRI technique

Low carbohydrate diets are currently fashionable for inducing weight loss, but the metabolic effects at organ level are not well understood, especially the effect on liver fat storage. Such studies require serial hepatic fat measurements, for which liver biopsy is impractical. In 10 healthy volunteers we demonstrate the use of rapid (total 2 min acquisition time, 10 min magnet room time), non-invasive, quantitative MRI to serially measure hepatic fat changes induced by following a low carbohydrate diet for 10 days. A significant (p<0.01) reduction in hepatic fat after 3 days of dieting was observed in 5 subjects. All subjects demonstrated significant (p<0.01) reductions in hepatic fat by day 10. A strong correlation (kappa = 0.81) existed between the initial fat content and the percentage fat content reduction in the first 3 days of the diet. All subjects lost weight (average 1.7 kg at day 3 and 3.0 kg at day 10), but this was not correlated with hepatic fat loss after 3 days or 10 days of dieting. The results presented illustrate the potential value of MR hepatic fat quantification in longitudinal studies of hepatic fat content.     

乙型肝炎病毒所致慢性肝病病人肝脏铁沉积和脂肪变性的MRI定量研究

目的 根据多回波Dixon技术定量测得的R₂*值和质子密度脂肪分数（PDFF）评价乙型肝炎病毒（HBV）所致慢性肝病病人的肝脏铁含量和脂肪含量,探讨定量测量与病情进展的关系。方法 回顾性分析97例HBV所致慢性肝病病人,所有病人均行钆塞酸二钠（Gd-EOB-DTPA）增强MRI检查。根据病情进展状态将病人分为3组,慢性乙型肝炎（CHB）组21例,乙肝肝硬化（LC）组44例,LC合并肝细胞癌（HCC）组32例。另外纳入正常对照（NC）组20例。全部研究对象均进行了MRI多回波Dixon序列扫描,测量其肝实质R₂*值和PDFF;测量HCC病人病灶处的R₂*值和PDFF,获取所有LC病人的肝功能Child-Pugh评分。采用Kruskal-Wallis检验比较组间R₂*值和PDFF差异;采用配对t检验比较HCC组病灶与邻近正常肝组织的R₂*和PDFF。采用Spearman相关分析所有受试者R₂*值与PDFF,及LC病人Child-Pugh评分与其R₂*值、PDFF之间的相关性。结果 ①LC组、HCC组R₂*均高于NC组（均P<0.05）,HCC组R₂*高于CHB组（P<0.05）;HCC组PDFF高于NC组（P<0.05）。其余2组间R₂*和PDFF的差异均无统计学意义（均P>0.05）。②HCC病人病灶处的R₂*低于邻近正常肝组织（P<0.05）,而两者PDFF差异无统计学意义（P>0.05）。③所有受试者R₂*与PDFF呈正相关（r=0.558,P<0.05）,LC病人肝脏R₂*与Child-Pugh评分呈正相关（r=0.336,P<0.05）,PDFF与Child-Pugh评分无相关性（r=0.102,P>0.05）。结论 HBV所致慢性肝病病人可出现肝脏铁沉积和脂肪变性;随着病情的进展,肝脏铁含量和脂肪含量呈升高趋势;癌变病灶表现为肝脏富铁背景下的乏铁灶。     

Liver fat: effect of hepatic iron deposition on evaluation with opposed-phase MR imaging

PURPOSE: To retrospectively determine the effect of liver iron deposition on the evaluation of liver fat by using opposed-phase magnetic resonance (MR) imaging. MATERIALS AND METHODS: Committee on Human Research approval was obtained, and compliance with HIPAA regulations was observed. Patient consent was waived by the committee. Thirty-eight patients with cirrhosis (30 men, eight women; mean age, 58 years; range, 34-76 years) who underwent abdominal MR imaging and had contemporaneous liver biopsy were retrospectively identified. Two radiologists independently quantified liver fat according to the relative loss of signal intensity and compared this loss on opposed-phase and in-phase T1-weighted gradient-echo images. Liver fat percentage and presence of iron deposition were independently recorded by a pathologist. Generalized linear models, which included a mixed-random effects model, were used to determine the effect of iron deposition on the Spearman correlation coefficient for relative signal intensity loss versus histopathologically determined fat percentage. RESULTS: Liver iron deposition was found in 25 of 38 patients. Liver fat percentage (mean, 3%; range, 0%-25%) was identified histopathologically in 14 of 38 patients and in nine of 25 patients with iron deposition. For both readers, relative signal intensity loss at opposed-phase imaging was closely and significantly correlated (P < .05) with histopathologically determined liver fat percentage in patients without iron deposition (r = 0.7 for reader 1, r = 0.6 for reader 2), but no such correlation was found in patients with iron deposition (r = 0.1 for reader 1, r = -0.31 for reader 2; P > .05). CONCLUSION: Signal intensity loss on in-phase images caused by the presence of liver iron is a potential pitfall in the determination of liver fat percentage at opposed-phase MR imaging in chronic liver disease.     

3.0T ~1H-MRS联合梯度回波化学位移技术定量分析评估脂肪肝治疗效果

目的:探讨在3.0T MRI上联合运用氢质子波谱成像(1H-MRS)和梯度回波化学位移技术评估脂肪肝治疗效果的可行性。方法:搜集临床确诊的脂肪肝病例26例,于干预治疗前、干预治疗后3个月、6个月各行1次磁共振化学位移抑脂成像(梯度回波T1WI同/去相位双回波)和氢质子波谱成像(1 H-MRS),测得同/去相位序列的信号强度值(SIIP和SIOP),计算双回波脂变指数(FI)。测得1 H-MRS的水峰峰值(Pwater)和脂肪峰峰值(Plipid)、水峰峰下面积(Awater)、脂肪峰峰下面积(Alipid),计算肝细胞相对脂肪含量1(RLC1)及相对脂肪含量2(RLC2)。同期测量患者的血脂、谷氨酰转肽酶、腹围及身高体重指数(BMI),将其拟合成临床脂肪肝指数(FLI)。以FLI为参照标准,对不同时间点MRI所测得肝脏脂肪含量进行统计学分析。结果:FI、RLC1、RLC2与FLI进行秩相关性分析,呈正相关性(r>0,P<0.05)。干预治疗前后对照采用重复测量的方差分析,显示FI、RLC1、RLC2、FLI组间差异具有统计学意义(P=0.000),对时间(time)变化趋势的对比Polynomial检验显示time*type有统计学意义(P=0.000),提示FI、RLC1、RLC2在治疗前、治疗后3个月、治疗后6个月的变化是有差异的。可靠性分析显示,治疗前后组的FI和治疗前组的RLC1、RLC2的可重复性好,组内相关系数ICC≥0.75。结论:1H-MRS和梯度回波化学位移MRI可在一定程度上对脂肪肝进行定量测定,可作为脂肪肝动态监测、疗效评估和随访观察的有效手段。