脑白质疏松症的MR弥散成像及扩散张量成像的研究
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摘要
应用MR弥散加权成像及扩散张量成像技术,测量脑白质疏松病灶的ADC值、DCavg值及FA值,观察以上指标与脑白质疏松症严重程度的相关性,并探讨脑白质微结构变化及其与CT值的相关性,分析脑白质疏松与认知功能之间的关系。本文回顾性分析了24例脑白质疏松及8例健康志愿者的常规CT、MRI、DWI及DTI的影像学表现,结果表明:1、LA组病变区ADC、FA、DCavg值与正常对照组、LA组正常脑白质比较,差异有显著性。2、随着LA分级越来越高,ADC、DCavg值呈逐渐升高趋势,FA值呈逐渐降低趋势。3、LA病变在侧脑室前角、侧脑室后角、半卵圆中心感兴趣区域ADC、FA、DCavg值在不同性别间的比较,P>0.05,差异无显著性。4、根据FA、DCavg值与MMSE之间的相关系数,间接推断LA与认知功能的关系。故DTI为临床提供早期诊断和全面评估,及早阻止认知功能的衰退,提高生活质量,减轻社会负担。
Leukoaraiosis (LA) was first proposed in 1987 by Hachinski. Most reasons are vascular factors.LA shows low-density by CT scan or high signal areas by MRI scan in perventricular or subcortical areas (centrum semiovale). It is a combination of causes white matter abnormalities. LA happens more common in people over age 60, often accompanied with dementia and cerebrovascular disease, also found in asymptomatic elderly people. With the progress of the disease, It can cause chronic progressive disorder of cognitive function, seriously affecting the quality of life and increased social burden.
Diagnosis of leukoaraiosis has been dependent on the CT and MRI, demyelinating disease with or without changes, as well as the extent of demyelination can make preliminary judgments. Functional MRI makes MR imaging diagnosis from morphology to the direction of the function development. In addition to evaluation of anatomical structures, but also non-invasive evaluation of brain function in the situation. Diffusion weighted imaging (DWI) reflects the microscopic movement of water molecules, Brownian motion of water molecules are very sensitive. It can detect the water apparent diffusion coefficient (ADC) values in the living tissue; we study the disease status from cellular and molecular level. Diffusion tensor imaging (DTI) as a new technology that uses spin echo-echo planar imaging (SE-EPI) sequence, which is currently clinical practice in the fastest scanning techniques. Reflect the living tissue water diffusion of information, observe the trend of brain white matter tract organization, bypass, push, and interrupt and sabotage abnormal proliferation of tissue are anisotropic. Ordinary diffusion-weighted sequence can not reflect the diffusion anisotropy, while the DTI sequence applied in a number of diffusion gradient directions, and collected separately, and then draw a variety of data, obtained by calculating multiple images. Fractional anisotropy (FA )is used to quantitative analysis of key indicators.
This study retrospectively analyzed 24 patients with leukoaraiosis patients and 8 healthy volunteers by CT, MRI, DWI and DTI scan, combined with its performance、related its parameters, and relevant literature, to observe the relevant parameters and the brain white matter serious degree of osteoporosis, to explore the micro-structural changes in white matter, cognitive function compare with different sex, clinical provide early diagnosis and hamper comprehensive assessment of cognitive function decline , improve quality of life and reduce the social burden.
Method:
We studied 24 patients with leukoaraiosis and 8 healthy people with a mean age of 63.3 years, and the control group of 8 patients, 2 males, 6 females, mean age was 54 years old; LA 24 patients, male 13 cases, 11 female, mean age was 65.5 years. All patients were examine by Siemens Avanto 1.5T superconducting MR scanner system . MRI included axial TlWI, T2WI, FLAIR, sagittal T2WI weighted images. T1WI axial used spin echo sequence, TR: 550ms, TE: 8.4ms. T2WI axial use fast spin echo sequence , TR: 4500ms, TE: 85ms. Axial FLAIR: TR: 9000ms,TE: 99ms, TI: 2458.6ms. Sagittal T2WI: TR: 3500ms, TE: 99ms. Axial diffusion-weighted imaging (DWI) using single-shot echo-planar sequence (EPI), in the X, Y, Z three directions imposed sensitive gradient, b = 0s/mm2 and b = 1000s/mm2, TR: 2900ms, TE: 89ms , scan time: 57s. Axial T1WI, T2WI, FLAIR, sagittal T2WI and DWI sequences thickness are 6.0mm, spacing 1.8mm, FOV 230mm×230mm. DTI using echo-planar pulse sequence (Echo Planar Imaging, EPI), diffusion gradient directions for the 20, b 0 and 1000s/mm2, scan level, parallel to the conventional MRI, slice thickness 5.0mm, spacing 1.5mm, TR 2700ms, TE 88ms, FOV 230mm×230mm. Excitation frequency of 4, scan time was 3.56min. DTI-facilitate multi-directional reconstruction, all patients scan anatomical image (t1-mpr-ns-tra-p2-iso) sequence, slice thickness 1.0mm, spacing 0.5mm, TR1900ms, TE3.37ms, FOV 256mm×256mm.
All subjects caught using GE light speed 16-slice spiral CT examination: canthal line to listen to the baseline. Scan parameters: 120kV, 230mAs, slice thickness 5mm, matrix 512×512, window width 80, window 35.
Scan after the completion of the original image sent to the Siemens workstation using Neuro 3D software for analysis and processing, the DTI as the superposition of the original image and anatomy, and tracing through the white matter imaging (Diffusion Tensor Tractography, DTT) for reconstruction of nerve fiber bundles. Select the lateral ventricle anterior horn, lateral horn, semi-oval center, genu of corpus callosum, corpus callosum selected regions of interest (Regionof Interest, ROI). Negative control group, region of interest measurement ADC, DCavg, FA values and CT values, LA group routine MRI scan on the light of the abnormal signal
Measure the ROI of leukoaraiosis ADC, DCavg, FA values and CT value.
Results:
Seen by the control group corpus callosum, centrum semiovale, posterior horn of lateral ventricle adjacent to lateral ventricle anterior horn next to the FA value was followed a downward trend. LA group of ADC, FA, DCavg values were normal control group and LA group of normal white matter by univariate analysis of variance were statistically significant. LA group the parameters of different grades can be seen, with the LA classification more and more, ADC, DCavg values were gradually increasing trend, FA values showed a decreasing trend. LA lesions in the lateral ventricle on the anterior horn, lateral horn, semi-oval center region of interest ADC, FA, DCavg values in different genders line independent samples T test, P> 0.05,No statistically significant. According to FA, DCavg value of the correlation coefficient between MMSE and indirectly infer the relationship between LA and cognitive function.
Conclusion:
DTI analysis of leukoaraiosis by the FA, DCavg value of conventional MRI, can detect abnormal changes in the microstructure of white matter, leukoaraiosis in the early diagnosis, early clinical intervention, blocked the decline of cognitive function.
Leukoaraiosis (LA) was first proposed in 1987 by Hachinski. Most reasons are vascular factors.LA shows low-density by CT scan or high signal areas by MRI scan in perventricular or subcortical areas (centrum semiovale). It is a combination of causes white matter abnormalities. LA happens more common in people over age 60, often accompanied with dementia and cerebrovascular disease, also found in asymptomatic elderly people. With the progress of the disease, It can cause chronic progressive disorder of cognitive function, seriously affecting the quality of life and increased social burden.
Diagnosis of leukoaraiosis has been dependent on the CT and MRI, demyelinating disease with or without changes, as well as the extent of demyelination can make preliminary judgments. Functional MRI makes MR imaging diagnosis from morphology to the direction of the function development. In addition to evaluation of anatomical structures, but also non-invasive evaluation of brain function in the situation. Diffusion weighted imaging (DWI) reflects the microscopic movement of water molecules, Brownian motion of water molecules are very sensitive. It can detect the water apparent diffusion coefficient (ADC) values in the living tissue; we study the disease status from cellular and molecular level. Diffusion tensor imaging (DTI) as a new technology that uses spin echo-echo planar imaging (SE-EPI) sequence, which is currently clinical practice in the fastest scanning techniques. Reflect the living tissue water diffusion of information, observe the trend of brain white matter tract organization, bypass, push, and interrupt and sabotage abnormal proliferation of tissue are anisotropic. Ordinary diffusion-weighted sequence can not reflect the diffusion anisotropy, while the DTI sequence applied in a number of diffusion gradient directions, and collected separately, and then draw a variety of data, obtained by calculating multiple images. Fractional anisotropy (FA )is used to quantitative analysis of key indicators.
This study retrospectively analyzed 24 patients with leukoaraiosis patients and 8 healthy volunteers by CT, MRI, DWI and DTI scan, combined with its performance、related its parameters, and relevant literature, to observe the relevant parameters and the brain white matter serious degree of osteoporosis, to explore the micro-structural changes in white matter, cognitive function compare with different sex, clinical provide early diagnosis and hamper comprehensive assessment of cognitive function decline , improve quality of life and reduce the social burden.
Method:
We studied 24 patients with leukoaraiosis and 8 healthy people with a mean age of 63.3 years, and the control group of 8 patients, 2 males, 6 females, mean age was 54 years old; LA 24 patients, male 13 cases, 11 female, mean age was 65.5 years. All patients were examine by Siemens Avanto 1.5T superconducting MR scanner system . MRI included axial TlWI, T2WI, FLAIR, sagittal T2WI weighted images. T1WI axial used spin echo sequence, TR: 550ms, TE: 8.4ms. T2WI axial use fast spin echo sequence , TR: 4500ms, TE: 85ms. Axial FLAIR: TR: 9000ms,TE: 99ms, TI: 2458.6ms. Sagittal T2WI: TR: 3500ms, TE: 99ms. Axial diffusion-weighted imaging (DWI) using single-shot echo-planar sequence (EPI), in the X, Y, Z three directions imposed sensitive gradient, b = 0s/mm2 and b = 1000s/mm2, TR: 2900ms, TE: 89ms , scan time: 57s. Axial T1WI, T2WI, FLAIR, sagittal T2WI and DWI sequences thickness are 6.0mm, spacing 1.8mm, FOV 230mm×230mm. DTI using echo-planar pulse sequence (Echo Planar Imaging, EPI), diffusion gradient directions for the 20, b 0 and 1000s/mm2, scan level, parallel to the conventional MRI, slice thickness 5.0mm, spacing 1.5mm, TR 2700ms, TE 88ms, FOV 230mm×230mm. Excitation frequency of 4, scan time was 3.56min. DTI-facilitate multi-directional reconstruction, all patients scan anatomical image (t1-mpr-ns-tra-p2-iso) sequence, slice thickness 1.0mm, spacing 0.5mm, TR1900ms, TE3.37ms, FOV 256mm×256mm.
All subjects caught using GE light speed 16-slice spiral CT examination: canthal line to listen to the baseline. Scan parameters: 120kV, 230mAs, slice thickness 5mm, matrix 512×512, window width 80, window 35.
Scan after the completion of the original image sent to the Siemens workstation using Neuro 3D software for analysis and processing, the DTI as the superposition of the original image and anatomy, and tracing through the white matter imaging (Diffusion Tensor Tractography, DTT) for reconstruction of nerve fiber bundles. Select the lateral ventricle anterior horn, lateral horn, semi-oval center, genu of corpus callosum, corpus callosum selected regions of interest (Regionof Interest, ROI). Negative control group, region of interest measurement ADC, DCavg, FA values and CT values, LA group routine MRI scan on the light of the abnormal signal
Measure the ROI of leukoaraiosis ADC, DCavg, FA values and CT value.
Results:
Seen by the control group corpus callosum, centrum semiovale, posterior horn of lateral ventricle adjacent to lateral ventricle anterior horn next to the FA value was followed a downward trend. LA group of ADC, FA, DCavg values were normal control group and LA group of normal white matter by univariate analysis of variance were statistically significant. LA group the parameters of different grades can be seen, with the LA classification more and more, ADC, DCavg values were gradually increasing trend, FA values showed a decreasing trend. LA lesions in the lateral ventricle on the anterior horn, lateral horn, semi-oval center region of interest ADC, FA, DCavg values in different genders line independent samples T test, P> 0.05,No statistically significant. According to FA, DCavg value of the correlation coefficient between MMSE and indirectly infer the relationship between LA and cognitive function.
Conclusion:
DTI analysis of leukoaraiosis by the FA, DCavg value of conventional MRI, can detect abnormal changes in the microstructure of white matter, leukoaraiosis in the early diagnosis, early clinical intervention, blocked the decline of cognitive function.
引文
[1] Hachinaki VC, Potter P, Merskey H. Leukoaraiosis[J]. Arch Neurol, 1987,44(1):21-23.
[2] Knopman D, Boland LL, Mosley T, et al. Cardiovascular risk factors and cognitive decline in middle aged adults[J]. Neurology, 2001,56(1):42-48.
[3] Breteler MM, vanSwieten JC, Bots ML, et al, Cerebral white matter lesions, vascular risk factors, and cognitive function in a population-based study[J]. Neurology, 1994,44:1246-1252.
[4] Markus HS, Lythgoe DJ, Ostegaard L, et al, Reduced cerebral blood flow in white matter in ischaemic leukoaraiosis demonstrated using quantitative exogenous contrast based perfusion MRI[J]. J Neurol Neurosurg Psychiatry, 2000,69:48-53.
[5]李亚健,李文贤,孙兮文等.老年人脑白质疏松与认知功能的关系[J].上海医学影像杂志, 2002,11(2):99-101.
[6] Libby P, Hansson GK. Involvement of immune system in human atherogenesis: current knowledge and unanswered questions[J]. Lab Invest, 1991,64 (1):5-15.
[7] Strub R. Vascular dementia[J]. South Med J, 2003,96(4):363-366.
[8] Sierra C, Coca A. White matter lesions and cognitive impairment as silent cerebral disease in hypertension[J]. The Scientific World Journal, 2006,21(6):494-501.2000,(59):23-30.
[24] Tullberg M, Fletcher E, DeCarli C, et al. White matter lesions impair frontal lobe function regardless of their location[J]. Neurology, 2004,63(2):246- 253.
[25] Carew TG, Lamar M, Cloud BS, et al. Impairment in category fluency in ischemic vascular dementia[J]. Neuropsychology, 1997, 11(3):400-412.
[26] Nasreddine ZS, Phillips NA, Bedirian V, et al. The Montreal cognitive assessment, MoCA: A brief screening tool for mild cognitive impairment[J]. J Am Geriatr Soc, 2005,53(4):695-699.
[27] Kaplan E, Fein D, Morris R, et al. The WAIS-Rr as a Neuropsychological Instrument. San Antonio: Pschological Corporation, 1991.
[28] Hajnal JV, DoranM, Hall AS, et al. MR imaging of anisotropically restricted diffusion of water in the nervous system: technical, anatomic, and pathologic considerations[J]. J Comput Assist Tomogr, 1991, 15(1):1-18.
[29]张雪林,磁共振成像诊断学[M].北京:人民军医出版社, 2001,42.
[30] Gillard JH, Papadakis NG, Markin K, et al. MR diffusion tensor imaging of white matter tract disruption in stroke at 3T[J]. British Journal of Radiology, 2001,74(883):642-647.
[31] Jellison BJ, Field AS, Medow J, et al. Diffusion tensor imaging of cerebral white matter: a pictorial review of physics, fiber tract anatomy, and tumor imaging patterns[J]. Amerian Journal of Neuroradiology2004:25(3):356-369.
[32] Aharon-peretz J, Cummings JL, Hill MA. Vascular dementia and dementia of the Alzheimer type[J]. Arch Neurol, 1988,45(7):719-721.
[33] Sullivan MO, Morris R, Huckstep B, et al. Diffusion tensor MRI correlates with executive dysfunction in patients with ischaemic leukoaraiosis[J]. J Neurol Neurosurg Psychiatry, 2004,75(3):441-447.
[34]张雪宁,张云亭.脑白质疏松的扩散张量成像(DTI)研究[J].临床放射学杂志, 2006,25(7):593-597.
[35]何光武,董德柱,沈天真,等.正常成人大脑胼胝体弥散张量纤维束成像研究[J]医学影像学杂志, 2005,15(2):892921.
[36] Pierpaoli C, Jezzard P, Basser PJ, et al. Diffusion tensor MR imaging of the human brain[J]. Radiology, 1996,201(3):637-648.
[37] Nusbaum AO, Tang CY, Buchsbaum MS, et al. Regional and global changes in cerebral diffusion with normal aging[J]. Am J Neuroradiol, 2001,22(1):136-142.
[38] Chen ZG, Li TQ, Hindmarsh T. Diffusion tensor trace mapping normal adult brain using single-shot EPI technique: A methodologic study of the aging brain[J]. Acta Radiol, 2001,42(5):447-458.
[39] Englter ST, Provenzale JM, Petrella JR, et al. The effect of aging on the apparent diffusion coefficient of normal-appearing white matter[J]. AJR Am J Roentgenology, 2000,175(2):425-430.
[40] Sacco S, Carolei A. Homocysteine and leukoaraiosis: time for aclinical trial[J]. Neurol Sci, 2007,28(5): 235-237.
[41] Thein SS, Hamidon BB, The HS, et al. Leukoaraiosis as a predictor for mortality and morbidity after an acute ischaemic stroke[J]. Singapore Med J, 2007,48: 396-399.
[42]吴传深,周东丰,Peter Como.中国版简易精神状态量表在中国农村地区的适用性[J].中国心理卫生杂志, 2002,16(4): 242-245.
[43]陈立成,苏丽惠,樊春艳.“简易智能状态检查”量表在保定市正常老年人群中的应用[J].中国老年学杂志, 2004,11(24): 1018-1019.
[44] Roebuck JR, Cecil KM, Schnall MD, et al. Human breast lesions: characterization with proton MR spectroscopy[J]. Radiology, 1998,209(1): 269-275.
[45] Norris DG. High field human imaging[J]. J Magn Reson Imaging, 2003,18(5):519-529.
[46] Hunsche S, Michael ME, Stoeter P, et al. Diffusion-tensor MR imaging at 1.5 and 3.0T: initial observations [J]. Radiology, 2001,221:550-556.
[47] Poonawalla AH, zhou XJ. Analytical error propagation in diffusion anisotropy calculations[J]. J Magn Reson Imaging, 2004,19(4):489-498.
[48] Jones DK. The effect of gradient samping schemes on measures derived from diffusion tensor MRI: a Monte Carlo study[J]. Magn Reson Med, 2004,51(4):807-815.
[49]饶晶晶,漆剑频,王承德.扩散张量成像扩散梯度方向与DTI图像质量的相关性研究[J].放射学实践, 2008,23(3):320-323.
[50]倪建明,沈天真,陈星荣. 3.0T MR弥散梯度编码方向对脑组织FA值测量的影响[J].医学影像学杂志, 2007,17(7):660-663.
[51]肖江喜,郭雪梅,王霄英,等.头部弥散张量磁共振成像扫描方案的优选[J].中国医学影像技术, 2003,19:1433-1435.
[52]祝玉芬,冯连元,郭平珍,等.脑白质稀疏症的影像诊断[J].中华放射学杂志, 1995,29:757-761.
[53] Mantyla R, Aronen HJ, Salonen O, et al. The prevalence and distribution of white-matter changes on different MRI pulse sequences in a post- stroke cohort[J]. Neuroradiology. 1999;41(9):657-665.
[54] Steingart A, Hachinski VC, Lau C, et al. Cognitive and neurologic findings in demented patient with diffusion white matter lucencies on computed tomography scan[J].Arch Neurol, 1987,44(1):36-39.
[55] 0'Sullivan M, Summers PE, Jones DK, et al. Normal-appearing white matter in ischemic leukoaraiosis: a diffusion tensor MRI study[J]. Neurology, 2001,57(12):2307-2310.
[2] Knopman D, Boland LL, Mosley T, et al. Cardiovascular risk factors and cognitive decline in middle aged adults[J]. Neurology, 2001,56(1):42-48.
[3] Breteler MM, vanSwieten JC, Bots ML, et al, Cerebral white matter lesions, vascular risk factors, and cognitive function in a population-based study[J]. Neurology, 1994,44:1246-1252.
[4] Markus HS, Lythgoe DJ, Ostegaard L, et al, Reduced cerebral blood flow in white matter in ischaemic leukoaraiosis demonstrated using quantitative exogenous contrast based perfusion MRI[J]. J Neurol Neurosurg Psychiatry, 2000,69:48-53.
[5]李亚健,李文贤,孙兮文等.老年人脑白质疏松与认知功能的关系[J].上海医学影像杂志, 2002,11(2):99-101.
[6] Libby P, Hansson GK. Involvement of immune system in human atherogenesis: current knowledge and unanswered questions[J]. Lab Invest, 1991,64 (1):5-15.
[7] Strub R. Vascular dementia[J]. South Med J, 2003,96(4):363-366.
[8] Sierra C, Coca A. White matter lesions and cognitive impairment as silent cerebral disease in hypertension[J]. The Scientific World Journal, 2006,21(6):494-501.2000,(59):23-30.
[24] Tullberg M, Fletcher E, DeCarli C, et al. White matter lesions impair frontal lobe function regardless of their location[J]. Neurology, 2004,63(2):246- 253.
[25] Carew TG, Lamar M, Cloud BS, et al. Impairment in category fluency in ischemic vascular dementia[J]. Neuropsychology, 1997, 11(3):400-412.
[26] Nasreddine ZS, Phillips NA, Bedirian V, et al. The Montreal cognitive assessment, MoCA: A brief screening tool for mild cognitive impairment[J]. J Am Geriatr Soc, 2005,53(4):695-699.
[27] Kaplan E, Fein D, Morris R, et al. The WAIS-Rr as a Neuropsychological Instrument. San Antonio: Pschological Corporation, 1991.
[28] Hajnal JV, DoranM, Hall AS, et al. MR imaging of anisotropically restricted diffusion of water in the nervous system: technical, anatomic, and pathologic considerations[J]. J Comput Assist Tomogr, 1991, 15(1):1-18.
[29]张雪林,磁共振成像诊断学[M].北京:人民军医出版社, 2001,42.
[30] Gillard JH, Papadakis NG, Markin K, et al. MR diffusion tensor imaging of white matter tract disruption in stroke at 3T[J]. British Journal of Radiology, 2001,74(883):642-647.
[31] Jellison BJ, Field AS, Medow J, et al. Diffusion tensor imaging of cerebral white matter: a pictorial review of physics, fiber tract anatomy, and tumor imaging patterns[J]. Amerian Journal of Neuroradiology2004:25(3):356-369.
[32] Aharon-peretz J, Cummings JL, Hill MA. Vascular dementia and dementia of the Alzheimer type[J]. Arch Neurol, 1988,45(7):719-721.
[33] Sullivan MO, Morris R, Huckstep B, et al. Diffusion tensor MRI correlates with executive dysfunction in patients with ischaemic leukoaraiosis[J]. J Neurol Neurosurg Psychiatry, 2004,75(3):441-447.
[34]张雪宁,张云亭.脑白质疏松的扩散张量成像(DTI)研究[J].临床放射学杂志, 2006,25(7):593-597.
[35]何光武,董德柱,沈天真,等.正常成人大脑胼胝体弥散张量纤维束成像研究[J]医学影像学杂志, 2005,15(2):892921.
[36] Pierpaoli C, Jezzard P, Basser PJ, et al. Diffusion tensor MR imaging of the human brain[J]. Radiology, 1996,201(3):637-648.
[37] Nusbaum AO, Tang CY, Buchsbaum MS, et al. Regional and global changes in cerebral diffusion with normal aging[J]. Am J Neuroradiol, 2001,22(1):136-142.
[38] Chen ZG, Li TQ, Hindmarsh T. Diffusion tensor trace mapping normal adult brain using single-shot EPI technique: A methodologic study of the aging brain[J]. Acta Radiol, 2001,42(5):447-458.
[39] Englter ST, Provenzale JM, Petrella JR, et al. The effect of aging on the apparent diffusion coefficient of normal-appearing white matter[J]. AJR Am J Roentgenology, 2000,175(2):425-430.
[40] Sacco S, Carolei A. Homocysteine and leukoaraiosis: time for aclinical trial[J]. Neurol Sci, 2007,28(5): 235-237.
[41] Thein SS, Hamidon BB, The HS, et al. Leukoaraiosis as a predictor for mortality and morbidity after an acute ischaemic stroke[J]. Singapore Med J, 2007,48: 396-399.
[42]吴传深,周东丰,Peter Como.中国版简易精神状态量表在中国农村地区的适用性[J].中国心理卫生杂志, 2002,16(4): 242-245.
[43]陈立成,苏丽惠,樊春艳.“简易智能状态检查”量表在保定市正常老年人群中的应用[J].中国老年学杂志, 2004,11(24): 1018-1019.
[44] Roebuck JR, Cecil KM, Schnall MD, et al. Human breast lesions: characterization with proton MR spectroscopy[J]. Radiology, 1998,209(1): 269-275.
[45] Norris DG. High field human imaging[J]. J Magn Reson Imaging, 2003,18(5):519-529.
[46] Hunsche S, Michael ME, Stoeter P, et al. Diffusion-tensor MR imaging at 1.5 and 3.0T: initial observations [J]. Radiology, 2001,221:550-556.
[47] Poonawalla AH, zhou XJ. Analytical error propagation in diffusion anisotropy calculations[J]. J Magn Reson Imaging, 2004,19(4):489-498.
[48] Jones DK. The effect of gradient samping schemes on measures derived from diffusion tensor MRI: a Monte Carlo study[J]. Magn Reson Med, 2004,51(4):807-815.
[49]饶晶晶,漆剑频,王承德.扩散张量成像扩散梯度方向与DTI图像质量的相关性研究[J].放射学实践, 2008,23(3):320-323.
[50]倪建明,沈天真,陈星荣. 3.0T MR弥散梯度编码方向对脑组织FA值测量的影响[J].医学影像学杂志, 2007,17(7):660-663.
[51]肖江喜,郭雪梅,王霄英,等.头部弥散张量磁共振成像扫描方案的优选[J].中国医学影像技术, 2003,19:1433-1435.
[52]祝玉芬,冯连元,郭平珍,等.脑白质稀疏症的影像诊断[J].中华放射学杂志, 1995,29:757-761.
[53] Mantyla R, Aronen HJ, Salonen O, et al. The prevalence and distribution of white-matter changes on different MRI pulse sequences in a post- stroke cohort[J]. Neuroradiology. 1999;41(9):657-665.
[54] Steingart A, Hachinski VC, Lau C, et al. Cognitive and neurologic findings in demented patient with diffusion white matter lucencies on computed tomography scan[J].Arch Neurol, 1987,44(1):36-39.
[55] 0'Sullivan M, Summers PE, Jones DK, et al. Normal-appearing white matter in ischemic leukoaraiosis: a diffusion tensor MRI study[J]. Neurology, 2001,57(12):2307-2310.