Volume correction for edema in single-volume proton MR spectroscopy of contrast-enhancing multiple sclerosis lesions.

The effect of edema on metabolic changes in contrast-enhancing multiple sclerosis lesions was studied by combining quantification of proton MR spectra with segmentation of the volume-of-interest, which was based on biexponential T(2) relaxation. All lesions showed a second component (s(long)) with a longer T(2) (185-450 ms), which was increased compared to healthy controls. Regression analysis indicated that s(long) replaces the short-T(2) component and total creatine. Since the water content was close to 100%, s(long) was used to correct for an increase in extracellular space. This compensated for the apparent loss of creatine and rendered cholines markedly increased, as observed in animals with experimental allergic encephalomyelitis. Total N-acetyl aspartate (NAA) concentration was inversely correlated with s(long) and between 34-70% of its average reduction was assigned to edema. Thus, NAA loss exceeded cellular loss. Assessment of varying degrees of edema may be especially beneficial for quantitative longitudinal studies.     

Proton MR spectroscopy of gadolinium-enhanced multiple sclerosis plaques.

Magnetic resonance (MR) imaging and proton MR spectroscopy were performed in 14 patients with clinically definite multiple sclerosis (MS). Prominent resonances in the 0.5-2.0-ppm region were seen in the spectra of six of nine gadopentetate dimeglumine-enhanced plaques in seven patients. These resonances were presumed to originate in lipids and other myelin breakdown products. Similar resonances were detected in only seven of 21 unenhancing plaques. The more frequent presence of such signals in the gadolinium-enhanced regions indicates that myelin breakdown is often associated with the inflammation that occurs in early stages of MS plaque evolution. It remains uncertain, however, whether active inflammation as indicated by gadolinium enhancement is a necessary precursor of myelin breakdown as detected at MR spectroscopy. Quantitative spectral analysis did not indicate statistically significant differences in N-acetyl aspartate and choline levels relative to creatine plus phosphocreatine between healthy volunteers and MS patients.     

Normal-appearing white matter in optic neuritis and multiple sclerosis: a comparative proton spectroscopy study

We investigated neurochemical abnormalities in the normal-appearing white matter (NAWM) on MRI of patients with optic neuritis (ON) and compared them to those of patients with multiple sclerosis (MS). Patients with ON (42) were classified into three groups according to abnormalities on brain MRI. Patients with MS (55) were devided in two groups: relapsing remitting MS (RRMS) and secondary progressive MS (SPMS). All patients underwent MRI of the brain and localised proton magnetic resonance spectroscopy (MRS) of NAWM. The results were compared to those of 15 controls. Patients with MS had significant abnormalities compared with controls and with patients with ON. Patients with RRMS and those with ON had comparable MRS parameters, while patients with SPMS had significant spectroscopic abnormalities in comparison with controls, but also with patients with RRMS. These changes consisted of a decrease in N -acetylaspartate, a neuronal marker, which may reflect axonal dysfunction and/or loss. MRS abnormalities were detected in 14 patients with ON (27 %). The main abnormalities consisted of a decrease in N -acetylaspartate, an increase in choline-containing compounds at long echo times, and the presence of free lipid peaks at short echo times. MRS of the NAWM on MRI may prove useful for detecting neurochemical brain abnormalities in ON not visible on MRI. Received: 19 January 1999 Accepted: 23 March 1999     

Serial diffusion-weighted MR imaging and proton MR spectroscopy of acute large demyelinating brain lesions: case report

We present the serial MR studies of two patients with symptomatic acute large demyelinating lesions that initially showed a drop in apparent diffusion coefficient values. Baseline proton MR spectroscopy showed a slight decrease in N-acetylaspartate and a normal choline level. An excess of lactate was observed at the first examinations and completely disappeared by the final examinations. The time-course evolution of the lesions shown by MR imaging and proton MR spectroscopic examinations suggests that the initial drop in apparent coefficient diffusion may have been related to dense inflammatory cell infiltration and scant tissue destruction or to reversible reduced vascular supply due to the severity of the inflammatory process.     

Longitudinal inter‐ and intra‐individual human brain metabolic quantification over 3 years with proton MR spectroscopy at 3 T

The longitudinal repeatability of proton MR spectroscopy (¹H‐MRS) in the healthy human brain at high fields over long periods is not established. Therefore, we assessed the inter‐ and intra‐subject repeatability of ¹H‐MRS in an approach suited for diffuse pathologies in 10 individuals, at 3T, annually for 3 years. Spectra from 480 voxels over 360 cm³ (～30%) of the brain, were individually phased, frequency‐aligned, and summed into one average spectrum. This dramatically increases metabolites' signal‐to‐noise‐ratios while maintaining narrow linewidths that improve quantification precision. The resulting concentrations of the N‐acetylaspartate, creatine, choline, and myo‐inositol are: 8.9 ± 0.8, 5.9 ± 0.6, 1.4 ± 0.1, and 4.5 ± 0.5 mM (mean ± standard‐deviation). the inter‐subject coefficients of variation are 8.7%, 10.2%, 10.7%, and 11.8%; and the longitudinal (intra‐subject) coefficients of variation are lower still: 6.6%, 6.8%, 6.8%, and 10%, much better than the 35%, 44%, 55%, and 62% intra‐voxel coefficients of variation. The biological and nonbiological components of the summed spectra coefficients of variation had similar contributions to the overall variance. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Benign versus secondary-progressive multiple sclerosis: the potential role of proton MR spectroscopy in defining the nature of disability.

PURPOSEWe determined the clinical utility of proton MR spectroscopy in defining the extent of disability in benign versus secondary-progressive multiple sclerosis (MS).METHODSThirty patients with clinically definite MS, including 16 patients with benign MS and 14 with secondary-progressive MS, and a group of 13 healthy volunteers were studied with combined stimulated-echo acquisition mode proton MR spectroscopy and MR imaging (all patients received contrast material).RESULTSAcute enhancing lesions of benign and secondary-progressive MS were characterized by a reduction in N-acetylaspartate (NAA)/choline and NAA/creatine and an increase in inositol compounds/creatine as compared with normal white matter. Such variations were also detected in chronic unenhancing lesions in patients with secondary-progressive MS, although they were not found in chronic unenhancing lesions in patients with benign MS. Chronic lesions of the two forms of the disease have significative differences in NAA and inositol signals.CONCLUSIONProton MR spectroscopy is able to show metabolic changes occurring in the white matter of patients with MS. Such changes differ according to the phase (acute versus chronic) and the clinical form (benign versus secondary-progressive) of the disease.     

多发性硬化白质脱髓鞘斑块的磁敏感加权成像及动态磁敏感增强灌注成像研究

目的 探讨多发性硬化(MS)脱髓鞘斑块的磁敏感加权成像(SWI)特征表现、MS斑块形态及微循环的演变过程.方法 对31例临床确诊的MS患者进行MR检查,扫描序列包括T2WI、液体衰减反转恢复(FLAIR)序列T2WI、T1WI及SWI.其巾21例进行了MRI随访,间隔时间为2.0～20.0个月,并且15例随访患者在第2次MR检查时行动态磁敏感增强灌注成像DSC-PI).观察MS斑块在"滤过"后相位图(FPI)的特征,测量斑块相位值和灌注参数.包括脑血流量(CBF)和脑血容量(CBV),并动态分析其演变规律.不同序列检测出的斑块个数采用配对t检验进行对照分析;采用Pearson相关分析法评价斑块相位值与灌注参数的相关性.结果 在FPI上,全部患者298个MS斑块呈3种表现:(1)低信号灶,无小血管穿行(109个,37%);(2)低信号灶,有小血管穿行(169个,57%);(3)病灶区仪有"异常血管区"而无明显信号降低(20个,7%).21例随诊病例中,前后2次检查经FLAIR T2WI检出的斑块总数及均数分别为452(22±8)、439(21±7)个,T1WI检出的斑块数分别为205(10±3)、206(10±-3)个,SWI检出的斑块数分别为211(10±3)、219(10±3)个,FLAIR T2WI检出的病灶均数减少(t=2.28,P=0.03),FPI检出的病灶均数增加(t=-2.61,P=0.02),而T1WI检出的病灶均数无明显变化(t=-1.00,P=0.33).21例随访患者中,6例发现有9个脱髓鞘斑块从仪表现为异常血管区演变到出现明确的低信号灶,其相位值变化(-0.031±0.012)与CBF值的变化[(-13.92±7.99)ml·100 g-1·min-1]以及CBV值的变化[(-2.54±1.33)ml·100 g-1]具有负相关(r值分别为-0.73、-0.84,P值均<0.05).结论 SWI相位图上低信号伴有小静脉穿行是MS脱髓鞘斑块的特征性表现;联合运用SWI和DSC-PI有助于进一步理解MS斑块的病理生理演变机制,并监测病情演变.

Abstract：

Objective To identify the imaging characteristics of demyelinating plaques in multiple sclerosis (MS) by using susceptibility weighted imaging(SWI),and further explore their morphologic and inicro-hemodynamic evolvements.Methods Thirty-one cases with clinically proven MS received SWI and dynamical susceptibility contrasted MR perfusion imaging(DSC-PI).And 21 cases received MR again in the fbllow-up period,with a time interval of 2.0-20.0 months[mean(7.5±4.8)months].Features of MS plaques in filtered phase images(FPI)were assessed,and the number of MS plaques detected in T1 WI,T2 FLAIR and FPI images were counted respectively.The measurements of phase values and perfusion parameters(including CBF and CBV)were acquired and their variation over time was also evaluated.The number of plaques detected by different MR sequences was compared by using paired t test,and the correlation between phase values and perfusion parameters was evaluated by using Pearson correlative analysis.Results Three types of MS plaques were observed in FPI images,including(1) round or oval hypointense foci without small veins(109 of 298,37%),(2)hypointense foci with small veins(169 of 298, 57% ), (3) abnormal vessels alone without hypointense foci (20 of 298, 7% ). In the 21 cases received MR follow-up, the total and mean plaque numbers identified on T2 FLAIR images were 452 and (22±8) in the first MR examination, and 439 and (21±7)in the second MR examination; and on T1-weithed images, they were 211 and( 10±3 ) in the first MR examination, and 219 and( 10±3 ) in the second MR examination; as well as those on FPI images were 205 and ( 10±3), and 206 and(10±3),respectively. Compared between the first and second MR scan, the mean of number on T2 FLAIR images decreased (t= 2. 28, P= 0. 03 ), and that on FPI images increased( t = -2. 61, P = 0. 02 ), and then that onT1-weight images keep invariable ( t = - 1. 00, P = 0. 33 ). Moreover, a development from regions with "abnormal vessels" alone to hypointense foci were observed in 9 plaques from 6 folh,w-up cases. The changes of phase values of these 9 plaques were significant correlated with CBF' and CBV (r = -0. 73 ,P <0. 05 ;r = -0. 84, P < 0. 05 ). Conclusions Hypointense focus with or without small veins on FPI image is the characteristic manifestation of MS plaques. Combination of SWI and DSC-PI is helpful in further understanding the patho-physiological mechanism of MS plaques and monitoring the evolvement of them.     

Prostate cancer: a comparative study of 11C-choline PET and MR imaging combined with proton MR spectroscopy

Purpose Prostate cancer is difficult to visualise in its early stages using current imaging technology. The present study aimed to clarify the utility of ¹¹C-choline PET for localising and evaluating cancer lesions in patients with prostate cancer by conducting a prospective comparison with magnetic resonance (MR) imaging combined with proton MR spectroscopy.Methods PET and MR imaging combined with proton MR spectroscopy were performed in 20 patients with prostate cancer. Correlations among the metabolite ratio of choline + creatine to citrate (Cho+Cr/Ci) on MR spectroscopy, serum PSA and maximum standardised uptake value (SUV_max) of ¹¹C-choline were assessed. The location of the primary lesion was assessed by the site of SUV_max and the laterality of the highest Cho+Cr/Ci ratio and confirmed by examination of surgical pathology specimens (n=16).Results PET exhibited a diagnostic sensitivity of 100% (20/20) for primary lesions, while the sensitivities of MR imaging and MR spectroscopy were 60% (12/20) and 65% (13/20), respectively. Weak linear correlations were observed between SUV_max and serum PSA (r=0.52, p<0.05), and between SUV_max and Cho+Cr/Ci ratio (r=0.49, p<0.05). Regarding the localisation of main primary lesions, PET results agreed with pathological findings in 13 patients (81%) (=0.59), while MR spectroscopy results were in accordance with pathological findings in eight patients (50%) (=0.11).Conclusion This preliminary study suggests that ¹¹C-choline PET may provide more accurate information regarding the localisation of main primary prostate cancer lesions than MR imaging/MR spectroscopy. A further clinical study of ¹¹C-choline PET in a large number of patients suspected of prostate cancer will be necessary to determine the clinical utility of ¹¹C-choline PET in patients who clinically require biopsy.     

MR波谱在预测前列腺癌转移中的作用

目的 探讨MR波谱(MRS)在预测前列腺癌转移中的价值.方法 65例超声引导下穿刺活检证实的前列腺癌患者,根据临床分期分为未发生转移组(B期和C期)31例和发生骨和(或)淋巴结转移组(D期)34例,通过MRS测定2组患者癌病灶区(胆碱+肌酸)/枸橼酸盐[(Cho +Cre)/Cit]的比值,并比较其差异.同时利用描绘受试者工作特征(ROC)曲线来初步评价MRS在预测前列腺癌发生转移中的效能.结果 未发生转移组和发生转移组患者的前列腺癌区(Cho+Cre)/Cit比值分别为1.3±0.5和2.2±0.6,差异有统计学意义(t=6.38,P＜0.05).利用癌病灶区(Cho+Cre)/Cit的平均比值对肿瘤是否发生转移进行诊断试验,ROC曲线下面积(Az)值为0.87,最佳临界点为1.53,此时诊断的敏感性为94.12%(32/34),特异性为67.74%(21/31),准确性为81.54%(53/65).结论 MRS作为一种无创的MRS检查方法 ,有可能对肿瘤是否发生转移作出预测.     

In Vivo proton MR spectroscopy of human gliomas: definition of metabolic coordinates for multi-dimensional classification

Several multi-dimensional statistical evaluation methods were applied to single-voxel proton MR spectra of glial brain tumors and of healthy volunteers. Metabolic coordinates with histological relevance for future diagnosis were found by which spectra from controls, low-grade tumors, and highgrade tumors were completely separated. Significant differences between low-grade and high-grade glioma patients and controls were found for several metabolic ratios by variance analysis. Cluster analysis both with and without principal component analysis was applied. The outcome of these two approaches depended mainly on the lipid-to-creatine ratio. Two other approaches, discriminant factor analysis and the orthonormal discriminant vector method were then used to find discriminatory metabolic coordinates. It turned out that a linear combination of all evaluable metabolic ratios made it possible to separate the three groups completely. On the basis of these results, a classification method that uses the entire proton MRS spectrum is proposed.     

2D CSI proton MR spectroscopy of human spinal vertebra: feasibility studies

This report focuses on proton magnetic resonance spectroscopy (1H MRS) of spine vertebra acquired with two-dimensional chemical shift imaging (2D CSI), utilizing the stimulated echo acquisition mode (STEAM) sequence. Both validity and reproducibility studies were performed. To validate the 2D CSI method, its spectra were compared with those obtained with the single-voxel (SV) method. Five normal volunteers were scanned. The reproducibility of 2D CSI was examined by performing spectroscopy on two different occasions, on three normal volunteers. Data show that the STEAM 2D CSI technique results in MRI spectra comparable to those obtained with the STEAM SV method. 2D CSI offers significant time savings and convenient multi-voxel spectral analysis at a substantially higher signal-to-noise ratio. The 2D CSI method was then applied to a patient with a small vertebral hemangioma. The results demonstrated that the voxels containing the hemangioma exhibit different spectra than the neighboring voxels of the same vertebra. Additionally, a case of vertebral osteoporosis was investigated. Results showed a significant increase in the lipid-to-water ratio (LWR). It is suggested that 2D CSI may be powerful in identifying physiological as well as pathological changes of the bone marrow. Furthermore, covering a more extensive area of the vertebral body will maximize the chances of depicting a small focus of pathologic tissue. A more detailed bone marrow pattern was noticed in on one subject whose spectra show more lipid peaks.     

P-31 MR spectroscopy of skeletal and cardiac muscle metabolism in patients with systemic sclerosis: A multiple case study

Three-dimensionally localized proton-decoupled phosphorus-31 magnetic resonance (MR) spectroscopy of skeletal and cardiac muscle was performed in six patients with systemic sclerosis. Cardiac (n = 9) and skeletal (n = 6) spectra were also obtained in healthy volunteers. Metabolite ratios and intracellular pH were determined from the spectra of skeletal and cardiac muscle. The phosphocreatine-to-adenosine triphosphate ratio was normal for both skeletal and cardiac muscle in patients with systemic sclerosis. The pH values of skeletal muscle were similar in patients and control subjects (7.13 ± 0.02 vs 7.12 ± 0.01, respectively). In skeletal muscle, the inorganic phosphate-to-phosphocreatine ratio in patients was increased relative to that of control subjects (0.106 ± 0.014 vs 0.086 ± 0.006, respectively; P =.02). P-31 MR spectroscopy showed no abnormalities in the myocardium of patients with systemic sclerosis. Assessment of the inorganic phosphate-to-phosphocreatine ratio in peripheral skeletal muscle may be helpful for assessing disease activity.     

Segmentation of multiple sclerosis lesions in MR images: a review

Introduction  

Multiple sclerosis (MS) is an inflammatory demyelinating disease that the parts of the nervous system through the lesions generated in the white matter of the brain. It brings about disabilities in different organs of the body such as eyes and muscles. Early detection of MS and estimation of its progression are critical for optimal treatment of the disease.     

MR imaging in acute multiple sclerosis: ringlike appearance in plaques suggesting the presence of paramagnetic free radicals.

MR studies in three patients with multiple sclerosis have shown clearly defined rings within plaques of demyelination, having signal characteristics consistent with the presence of paramagnetic material. It is suggested that these appearances represent the presence of free radicals in the macrophage layer forming the margin of an acute plaque.     

FLAIR imaging for multiple sclerosis: a comparative MR study at 1.5 and 3.0 Tesla

The purpose of this study was (1) to identify the optimal TE for FLAIR-imaging at 3.0 T assessing three different echo times qualitatively and quantitatively and (2) to evaluate the diagnostic efficacy of high-field 3.0-T FLAIR imaging in comparison to conventional 1.5-T MRI in patients with multiple sclerosis (MS). Twenty-two patients with clinically definite MS underwent axial FLAIR imaging at 1.5 and 3.0 T. In 15 of these patients further FLAIR images with a TE of 100, 120 and 140 ms were acquired at 3.0 T. Imaging protocols were modified for 3.0 T using the increased SNR to acquire more and thinner slices while maintaining a comparable scan time. FLAIR images of either different TEs or different field strengths were ranked for each patient qualitatively by two observers. Signal intensity measurements were obtained in the gray and white matter, CSF and representative white matter lesions (WML). At 3.0 T, a TE of 100 and 120 ms proved superior in all qualitative categories when compared to 140 ms. In the quantitative assessment CNR of WML was highest for 120 ms (CNR: 19.8), intermediate for 100 ms (17.2) and lowest for 140 ms (15.3) (P<0.003). For lesion conspicuity and overall image quality, 3.0 T was judged superior to 1.5 T, whereas no difference was found for gray-white differentiation and image noise. With regard to artifacts, 3.0 T was inferior to 1.5 T. The CNR for WML was slightly lower at 3.0 T, but the difference was not significant (22.6 vs. 28.0, P=ns). However, significantly more WML were detected at 3.0 T than at 1.5 T (483 vs. 341, P<0.0001). The optimal echo time for FLAIR imaging at 3.0 T is 120 ms due to the significantly higher CNR of WML. By trading the higher SNR at 3.0 T for better spatial resolution, nearly the same CNR level could be maintained, increasing lesion detectability at 3.0 T compared to 1.5 T. Thus, high-field MRI may further strengthen the role of MRI as the most sensitive paraclinical test for the early diagnosis of MS.     

The fetus at term: in utero volume-selected proton MR spectroscopy with a breath-hold technique--a feasibility study

In three healthy gravidas at 38 and 39 weeks gestation, fetal MR spectroscopy was performed with a breath-hold technique by using the following pulse sequences: single voxel point-resolved spectroscopy, or PRESS, for liver and heart studies and stimulated-echo acquisition mode, or STEAM, for brain studies. Signal peaks of lipid from heart and liver were detected, as were the signal peaks of choline, creatine, and N-acetylaspartate from fetal brain. Findings demonstrated the feasibility of performing proton MR spectroscopy to assess mobile fetal structures.     

肝硬化患者肝移植前后脑代谢改变的MR波谱研究

目的 采用1H-MRS定量分析肝硬化患者肝移植前后脑代谢的变化.方法 选取37例肝硬化患者(患者组)和22名健康志愿者(对照组)进行神经心理学测试及点分辨自旋回波波谱序列(PRESS)MRS,并于肝移植术后1、3个月对18例患者进行随访,测量数字连线试验(NCT-A)、数字符号试验(DST)、符号数字试验(SDT)等神经心理学各指标及后扣带回、左侧基底节MRS各代谢物的含量.采用独立样本t检验比较对照组和患者组术前的神经心理学、MRS各参数;利用方差分析统计肝移植前后神经心理学测试、MRS的变化;用Pearson相关性检验分析各时间点扣带回和左侧基底节MRS各指标与神经心理学测试之间的相关性.结果 (1)移植术前患者组与对照组比较,后扣带回N-乙酰天冬氨酸(NAA)/肌酸(Cr)、胆碱(Cho)/Cr、肌醇(mI)/Cr、谷氨酸复合物(Glx)/Cr分别为1.96±0.21和1.73±0.12、0.65±0.12和0.83±0.09、0.41±0.14和0.72±0.11、2.37±0.38和1.92±0.32,两组差异有统计学意义(t值分别为-5.42、5.96、8.62、-4.72,P值均＜0.01);基底节Cho/Cr、mI/Cr、Glx/Cr分别为0.63±0.16和0.77±0.10、0.38±0.17和0.53±0.21、1. 70±0.36和1.29±0.30,两组差异有统计学意义(t值分别为3.64、3.07、-4.58,P值均＜0.01);(2)患者组的NCT-A测试时间[(5 8.17±19.12)s]明显长于对照组[(37.68±8.02)s],差异有统计学意义(t=4.14,P＜0.01);而DST[(36.67±9.91)分]及SDT[(31.67±9.49)分]成绩明显低于对照组[(55.36±9.27)、(50.73±8.34)分],差异有统计学意义(t值分别为4.60、4.65,P值均＜0.01).移植术后1个月患者组NCT-A、DST、SDT分别为(53.06±12.71)s、(41.89±8.17)、(37.44±7.68)分,术后3个月分别为(35.72 ±5.20)s、(54.39±5.69)分、(49.39±5.65)分,与术前比较差异有统计学意义(F值分别为33.554、85.772、83.061,P值均＜0.01).(3)术后1个月患者组后扣带回NAA/Cr、Cho/Cr、mI/Cr、Glx/Cr分别为1.79±0.19、0.90士0.14、0.39±0.15、1.86士0.32,术后3个月分别为1.66±0.18、0.92±0.08、0.71±0.10、1.75±0.25,与术前比较差异有统计学意义(F值分别为12.658、38.178、75.186、19.420,P值均＜0.01).术后1个月患者组基底节Cho/Cr、mI/Cr、Glx/Cr分别为0.81±0.08、0.47 ±0.25、1.30 ±0.20,术后3个月分别为0.80 ±0.09、0.61±0.27、1.23±0.25,与术前比较差异有统计学意义(F值分别为9.447、8.027、17.952,P值均＜0.01).(4)术前扣带回的mI/Cr与NCT-A及DST、SDT之间具有相关性(r值分别为0.743、0.597、0.615,P值均＜0.01).结论 肝硬化患者脑代谢异常是可逆性的,后扣带回mI/Cr可作为监测肝移植后脑代谢恢复状况的指标.