Magnetisation transfer imaging of the normal adenohypophysis: the effect of sex and age

Magnetisation transfer (MT) techniques provide tissue contrast depending mainly on the concentration of macromolecules. Because many macromolecules are involved in the secretory activity of the pituitary gland, MT techniques might be useful in the study of pituitary gland disorders. Our purpose was to establish a quantitative database of the MT ratio (MTR) of the normal adenohypophysis and to see whether there are age- and sex-related differences. Using a three-dimensional gradient-echo sequence for MT we studied the adenohypophysis in 56 males and 61 females aged 7 months-77 years; postsaturation images were obtained using an on-resonance binomial prepulse. The images were normal in all but three patients, two with meningiomas, one with a schwannoma). Adenohypophyseal MTR increased in both sexes up to 19 years of age (r = 0.47 males, 0.39 females, P < 0.05 ). In men after 20 years and in women from 20–49 years MTR decreased (r = –0.68, P < 0.001, r = –0.46, P < 0.05, respectively). In women aged 50–59 years the MTR again increased slightly. The MTR in males was slightly higher at all ages except before 9 and after 50 years of age. These differences were not statistically significant except in the 40–49 year group (P < 0.05). Received: 11 August 2000 Accepted: 8 September 2000     

Magnetisation transfer ratios of contrast-enhancing and nonenhancing lesions in multiple sclerosis

Magnetisation transfer (MT) is a recently introduced technique for assessing the water content of tissues in vivo and its relationship to macromolecules or membranes. It has been suggested that MT could provide indirect evidence of the characteristics of multiple sclerosis (MS) lesions (oedema, demyelination, or gliosis). Our aims were to characterise brain MS lesions and to compare the magnetisation transfer ratio (MTR) values of lesions with different patterns of contrast enhancement. In patients with MS we measured the MTR of 65 gadolinium-enhancing and 292 nonenhancing lesions. Using the equation published by Dousset et al. we studied 29 patients with clinically definite MS and 10 healthy controls. Lesions had significantly lower MT than the normal-appearing white matter of the patients or the normal white matter of healthy controls. There was no difference in the MTR of enhancing and nonenhancing lesions. Enhancement was homogeneous in 45 and ring-like in 20 lesions; MTR values were lower in the latter. These findings are presumably related to the differences in pathological features of enhancing (different amounts of proteins and inflammatory cells, oedema and demyelination) and nonenhancing (gliosis, demyelination and axonal loss) lesions.     

Use of magnetisation transfer contrast to improve cerebral 3D MR angiography

To improve 3D-time of flight (3D-TOF) magnetic resonance angiography, we used magnetisation transfer (MT) to increase the contrast between flowing blood and stationary tissues. With a 1.5 KHz off-resonance radio-frequency MT applied for 16 ms at a maximum power within specific absorption rate (SAR) limits, a 37% decrease in the signal of white matter was obtained, whereas the signal from flowing blood decreased by only 8%. An improvement in maximum intensity projection (MIP) image quality was obtained all MT-3DTOF studies on seven volunteers using progressively more powerful MT pulses. Routine clinical use of MT-3DTOF appears promising and can be achieved at any strength field.     

Cerebrospinal fluid flow and production in patients with normal pressure hydrocephalus studied by MRI

An interleaved velocity-sensitised fast low-angle shot pulse sequence was used to study cerebrospinal fluid (CSF) flow in the cerebral aqueduct, and supratentorial CSF production in 9 patients with normal pressure hydrocephalus (NPH) and 9 healthy volunteers. The peak aqueduct CSF flow, both caudal and rostral, was significantly increased in patients with NPH. No significant difference in the supratentorial CSF production rate was found between patients (mean 0.60+/–0.59 ml/min) and healthy volunteers (mean 0.68+/–0.31 ml/min). Our method may be useful for investigation and monitoring of patients with NPH before and after ventriculoperitoneal shunt operations.     

Magnetization transfer measurements in normal-appearing cerebral white matter in patients with chronic obstructive hydrocephalus.

PURPOSE: The purpose of this work was to assess the presence of subtle changes in normal-appearing white matter on T2-weighted MR images in patients with chronic obstructive hydrocephalus using magnetization transfer (MT) measurements. METHOD: In 12 patients with chronic obstructive hydrocephalus, MT ratios (MTRs) of normal-appearing rostral (PR) and caudal (PC) periventricular white matter, of the genu (CG) and the splenium (CS) of the corpus callosum, and of the thalamus (TH) were measured and compared with those of 16 healthy control subjects. RESULTS: We found a significantly lower MTR in chronic obstructive hydrocephalus than in the normal group for PR, PC, CG, and CS but not for TH. CONCLUSION: Our study shows that MT measurements give additional information that cannot be gained by conventional SE MRI, suggesting that chronic obstructive hydrocephalus is associated with diffuse white matter damage that also affects normal-appearing cerebral white matter.     

Magnetisation transfer measurements of the subcortical grey and white matter in Parkinson's disease with and without dementia and in progressive supranuclear palsy

We measured the magnetisation transfer ratio (MTR) in the subcortical grey and white matter of 11 patients with idiopathic Parkinson's disease (PD) without dementia, six with PD with dementia (PDD), six with progressive supranuclear palsy (PSP), and 12 elderly control subjects to assess regional differences in structural brain damage. There were no significant differences in MTR in any region between PD and controls. However, patients with PDD had significantly lower MTR in the subcortical white matter, including the frontal white matter and the genu of the corpus callosum than the controls, whereas PSP had significantly lower MTR in the subcortical grey matter, including the putamen, globus pallidus and thalamus, in addition to the subcortical white matter. This suggests that regional patterns of structural brain damage can be detected using the magnetisation transfer technique. Measurement of MTR in the subcortical grey and white matter may be useful in differential diagnosis. Received: 10 May 2000 Accepted: 14 July 2000     

Magnetic resonance spectroscopy features of normal-appearing white matter in patients with acute brucellosis

We aimed to evaluate whether the subtle metabolic cerebral changes are present in normal-appearing white matter on conventional MRI, in patients with acute brucellosis, by using MR spectroscopy (MRS). Sixteen patients with acute brucellosis and 13 healthy control subjects were investigated with conventional MRI and single-voxel MRS. Voxels were placed in normal-appearing parietal white matter (NAPWM). N-Acetyl aspartate (NAA)/creatine (Cr) and choline (Cho)/Cr ratios were calculated. There was no significant difference between the study subjects and the control group in NAA/Cr ratios obtained from NAPWM. However, the Cho/Cr ratios were significantly higher in patients with acute brucellosis compared to controls (p=0.01). MRS revealed metabolic changes in normal-appearing white matter of patients with brucellosis. Brucellosis may cause subtle cerebral alterations, which may only be discernible with MRS. Increased Cho/Cr ratio possibly represents an initial phase of inflammation and/or demyelination process of brucellosis.     

对比增强磁化传递MRI在肺癌脑内小转移灶成像中的价值

目的　探讨对比增强磁化传递 (magnetisationtransfer,MT)MRI在肺癌脑内小转移灶的应用。方法　对 6 0例病人 (含 172个转移灶 )进行对比增强磁化传递前后的对照研究。对比增强磁化传递前采用SE序列T1WI。然后 ,注射钆喷替酸葡甲胺 (Gd DTPA) (0 1mmol/kg)增强后 ,进行SE序列T1WI和SE序列T1WIMT技术成像。通过比较对比度 /噪声比值 (C/Ns值 ) ,对采用MT技术与否的影像结果进行评估 ;再对采用MT技术与否所显示的转移灶数量进行对照。结果　所有采用T1WI对比增强MT技术的图像C/Ns值比常规T1WI对比增强图像的C/Ns值高。采用MT技术图像的C/Ns值为 2 6 98± 7 0 6 ( x±s) ,常规T1WI对比增强图像的C/Ns值为 15 5 1± 8 5 4 ,t =8 0 2 ,P <0 0 1。T1WI对比增强MT技术比常规T1WI对比增强能显示更多的转移灶数目 (6 0个 ) ,χ2 =7 79,P <0 0 1。结论　在显示肺癌脑内小转移灶方面 ,T1WIMT对比增强比常规T1WI对比增强更为敏感 ,对评估中枢神经系统转移性疾病具有重要的临床价值。     

Magnetization transfer imaging and magnetic resonance spectroscopy of normal-appearing white matter in late-life major depression

PURPOSE: To examine the relationships between the damaged macromolecular pool seen on magnetization transfer (MT) imaging and cerebral metabolic changes recorded by magnetic resonance spectroscopy (MRS), in frontal white and gray matter regions of late-life MDD patients. MATERIALS AND METHODS: MT imaging and MRS were performed on eight patients with late-life MDD and eight age-matched healthy controls. MT ratios were calculated using the on-resonance and off-resonance images. Correlations were computed between MT ratios and the ratios of several metabolites, including choline (Cho), myo-inositol (mI), N-acetylaspartate (NAA), and N-acetylaspartylglutamate (NAAG), to creatine (Cr). RESULTS: Statistically significant correlations were found in white matter between the MT ratios and mI/Cr (r = -0.90, N = 7, P = 0.016), and between the MT ratios and (NAA + NAAG)/Cr (r = -0.89, N = 8, P = 0.007). No significant correlations were found in gray matter or between the MT ratios and NAA/Cr or Cho/Cr in white matter. CONCLUSION: Changes in the white matter macromolecular protein pool, observed as reduced MT ratios, may be related to changes in the mI and the total NAA pools. These findings may have implications for the pathophysiology of late-life major depression.     

Magnetisation transfer ratio measurement in the cervical spinal cord: a preliminary study in multiple sclerosis

MRI readily detects the lesions of multiple sclerosis (MS) in the brain and spinal cord. Conventional MRI sequences do not, however, permit distinction between the various pathological characteristics (oedema, demyelination, axonal loss and gliosis) of lesions in MS. Magnetisation transfer (MT) imaging may be more specific in distinguishing the pathologies responsible for disability in MS, namely demyelination and axonal loss, and therefore may have a potential role in monitoring treatment. We have applied MT imaging to the cervical spinal cord to see if it is feasible to measure MT ratios (MTR) in this region where pathological changes may result in considerable disability. We studied 12 patients with MS and 12 age- and sex-matched normal controls using a sagittal T2-weighted fast spin-echo sequence with and without an MT pulse. The median value for cervical cord mean MTR measurement in normal controls was 19.30 % units (interquartile range 19.05–19.55), whereas values were significantly lower in MS patients (median = 17.95 % units, interquartile range 17.25–19.00, P = 0.0004). There was a low intrarater variability for repeated mean MTR measurements. We conclude that it is possible to measure MTR in the cervical spinal cord, that a significant reduction occurs in patients with MS, and that there may be a role for this measure in future MS treatment trials. Received: 11 May 1996 Accepted: 24 July 1996     

Contrast-enhanced magnetisation transfer MRI in metastatic lesions of the brain

Our purpose was to compare prospectively the sensitivity of contrast-enhanced magnetisation transfer (MT) MRI and gradient-echo (GE) T1-weighted images in metastatic disease of the brain. We studied 52 patients with brain metastases, using conventional T1-weighted GE and MT spin-echo (SE) images after the same standard dose of gadolinium. Axial 5-mm reconstructions of GE data were compared with 5-mm MT images in the same plane. Metastases were counted independently by two neuroradiologists. In 12 patients (23 %) MT imaging showed more metastases than GE images (P = 0.03). We detected 68 more metastases with the former technique. Received: 27 July 1997 Accepted: 22 April 1998     

Magnetization transfer ratio values and proton MR spectroscopy of normal-appearing cerebral white matter in patients with liver cirrhosis.

BACKGROUND AND PURPOSE: Hepatic encephalopathy in cirrhotic patients may be the clinical manifestation of disturbed cerebral cell volume homeostasis. The aim of this study was to investigate the presence of significant changes in magnetization transfer ratio (MTR) values, which could reflect an increase in free water within the brain of patients with liver cirrhosis, and to correlate these findings with minimal hepatic encephalopathy and proton MR spectroscopy ((1)H-MRS) abnormalities. METHODS: Twenty-four patients with liver cirrhosis and eight healthy control volunteers were included in the study. MR imaging studies included conventional T1- and T2-weighted imaging, (1)H-MRS, and magnetization transfer imaging. MTR and (1)H-MRS values were obtained from normal-appearing white matter and were correlated with each other and with the presence of minimal hepatic encephalopathy. RESULTS: (1)H-MRS showed a decrease in choline and myo-inositol and an increase in glutamine + glutamate with respect to creatine + phosphocreatine. MTR values were significantly decreased in cirrhotic patients when compared with healthy control volunteers, although this decrease was not significantly higher in the patients with minimal hepatic encephalopathy. The decreases in MTR values correlated with increases in glutamine + glutamate. CONCLUSION: The MTR decrease in patients with liver cirrhosis may be caused by low-grade astrocytic swelling produced as a response to the osmotic stress occurring in these patients. However, in this cross-sectional study, we did not find a correlation between MTR decrease and the presence of minimal hepatic encephalopathy, probably because of limitations in MTR quantification techniques.     

Atrophy of the corpus callosum correlates with white matter lesions in patients with cerebral ischaemia

Many studies of white matter high signal (WMHS) on T2-weighted MRI have disclosed that it is related to cerebral ischaemia and to brain atrophy. Atrophy of the corpus callosum (CC) has also been studied in relation to ischaemia. Our objective was to test the hypothesis that CC atrophy could be due to ischaemia. We therefore assessed CC, WMHS and brain atrophy in patients with risk factors without strokes (the risk factor group) and in those with infarcts (the infarct group), to investigate the relationships between these factors. We studied 30 patients in the infarct group, 14 in the risk factor group, and 29 normal subjects. Using axial T1-weighted MRI, cortical atrophy and ventricular enlargement (brain atrophy) were visually rated. Using axial T2-weighted MRI, WMHS was assessed in three categories: periventricular symmetrical, periventricular asymmetrical and subcortical. Using the mid-sagittal T1-weighted image, the CC was measured in its anterior, posterior, midanterior and midposterior portions. In the normal group, no correlations were noted between parameters. In the infarct group, there were significant correlations between CC and brain atrophy, and between CC atrophy and WMHS. After removing the effects of age, gender and brain atrophy, significant correlations were noted between some CC measures and subcortical WMHS. In the risk factor group, there were significant correlations between CC and brain atrophy and between CC atrophy and WMHS. After allowance for age, gender and brain atrophy, significant correlations between some CC measures and periventricular WMHS remained. The hypothesis that CC atrophy could be due to cerebral ischaemia was supported by other analyses. Namely, for correlations between the extent of infarcts and partial CC atrophy in patients with anterior middle cerebral artery (MCA) and with posterior MCA infarcts, there were significant correlations between the extent of infarct and midanterior CC atrophy in the former, and posterior CC atrophy in the latter. Our findings could indicate that CC atrophy is associated with cerebral ischaemia. Received: 5 December 1998/Accepted: 6 November 1999     

Magnetization transfer ratio histogram analysis of normal-appearing gray matter and normal-appearing white matter in multiple sclerosis.

PURPOSE: The purpose of this work was to determine the extent of disease and disease severity in the conventional MR normal-appearing gray matter (NAGM) and white matter (NAWM) in patients with relapsing-remitting (RR) and secondary progressive (SP) multiple sclerosis (MS) utilizing quantitative magnetization transfer ratio (MTR) histogram analysis. METHOD: Twenty-seven patients with MS (16 RR, 11 SP) and 16 healthy control subjects were studied. MTR was calculated in the totally segmented GM and WM without T2 lesions in each group. RESULTS: Each of the RR and SP MS patient groups had significantly smaller MTR histogram mean values in NAGM and NAWM than the healthy subjects (p 相似文献   

鼻咽癌放射治疗后颞叶常规MRI表现正常脑白质的扩散张量成像初步研究

目的 利用DTI对鼻咽癌患者放疗后颞叶常规MRI表现正常脑白质进行监测.方法 回顾性分析经病理活检证实的75例鼻咽癌患者的临床和影像资料,所有患者均行全脑常规MR和DTI检查,且常规MRI未见异常.以放疗前的18例患者作为对照组,放疗后的57例患者为放疗组,并根据放疗后不同时间分为5组:组1(放疗后≤3个月,16例)、组2(放疗后＞3～6个月,12例)、组3(放疗后＞6 ～9个月,10例)、组4(放疗后＞9 ～12个月,8例)、组5(放疗后＞12个月,11例).测量各组患者的部分各向异性分数(FA)、平均扩散系数(MD)、表观扩散系数(ADC)、平行本征值(入‖)及垂直本征值(λ⊥),采用单因素方差分析对各组数据进行分析.结果 对照组及放疗后各组的平均λ⊥值分别为(6.075±0.341)×10-4、(6.700±0.379)×10-4、(6.976±0.527)×10-4、(6.621 ±0.388)×10-4、(6.751±0.460)×10-4、(6.222±0.256)×10-4 mm2/s,λ‖值分别为( 12.524 ±0.713)×10-4、( 11.764±0.574)×10-4、(11.842±0.471)×10-4、( 11.569±0.552)×10-4、(12.050 ±0.614)× 10-4、( 12.100±0.529)×10-4 mm2/s,FA值分别为0.452±0.030、0.379±0.028、0.382±0.028、0.389±0.032、0.388±0.022、0.423±0.232,各组间差异均有统计学意义(F值分别为10.485、4.625、16.539,P值均＜0.05).进一步多重比较,放疗后12个月内(组1～4)的平均λ⊥值均较放疗前明显升高,差异有统计学意义(P＜0.05).而放疗12个月后(组5)的平均λ⊥值基本恢复,与放疗前差异无统计学意义(P＞0.05).放疗后9个月内(组1～3)的平均λ‖值较放疗前明显降低,差异有统计学意义(P＜0.05);9个月以后(组4、5)的平均λ‖值与对照组比较差异无统计学意义(P＞0.05).所有放疗后组(组1～5)的平均FA值均比放疗前明显下降,差异有统计学意义(P＜0.05).放疗后各组平均ADC及MD值对比放疗前差异均无统计学意义(P＞0.05).结论 DTI可以在常规MRI发现异常之前检测到脑组织特别是白质微观结构的改变,可以为临床早期诊断和早期干预放射性损伤提供更多影像学证据.     

The effect of magnetisation transfer contrast on cerebrospinal fluid on motion artefacts on fluid-attenuated inversion-recovery images

We assessed possible advantages of the use of fluid-attenuated inversion-recovery (FLAIR) sequences with magnetisation-transfer contrast (MTC) over conventional FLAIR images. We carried out cranial MRI at 1 tesla on 50 patients with both sequences. In nine patients with multiple sclerosis (MS) we performed a quantitative comparison of the two sequences, looking at the contrast-to-noise ratio between lesions and normal white matter and counting the number of lesions shown using each method. A qualitative comparison on all patients consisted of the analysis of the appearance of the normal parenchyma, of any lesions, and of artefacts, with particular reference to cerebrospinal fluid (CSF) motion artefacts. The quantitative analysis showed no meaningful difference between the two sequences. The cerebral parenchyma and lesions appeared substantially the same with both techniques. With FLAIR MTC there was a clear, and consistent reduction in CSF motion artefacts. FLAIR MTC sequences can usefully be used in place of the conventional sequence at 1 tesla.     

Frequency analyses of CSF flow on cine MRI in normal pressure hydrocephalus

Our objective was to clarify intracranial cerebrospinal fluid (CSF) flow dynamics in normal-pressure hydrocephalus (NPH). Frequency analyses of CSF flow measured with phase-contrast cine MRI were performed. The CSF flow spectra in the aqueduct were determined in patients (n=51) with NPH, brain atrophy or asymptomatic ventricular dilation (VD), and in healthy volunteers (control group; n=25). The changes in CSF flow spectra were also analyzed after intravenous injection of acetazolamide. Moreover, a phase transfer function (PTF) calculated from the spectra of the driving vascular pulsation and CSF flow in the aqueduct were assessed. These values were compared with the pressure volume response (PVR). The amplitude in the NPH group was significantly larger than that in the VD or control group because of a decrease in compliance. The phase in the NPH group was significantly different from that in either the VD or the control group, but no difference was found between the VD and control groups. The amplitude increased in all groups after acetazolamide injection. The PTF in the NPH group was significantly larger than in the control group, and a positive correlation was noted between PTF and PVR. Frequency analyses of CSF flow measured by cine MRI make it possible to noninvasively obtain a more detailed picture of the pathophysiology of NPH. Electronic Publication     

Narrow CSF space at high convexity and high midline areas in idiopathic normal pressure hydrocephalus detected by axial and coronal MRI

Introduction The aim of this study was to determine the performance of axial and coronal magnetic resonance imaging (MRI) in detecting the narrowing of the cerebrospinal fluid (CSF) space at the high convexity and high midline areas, which is speculated to be one of the clinical characteristics of idiopathic normal pressure hydrocephalus (iNPH). Methods We retrospectively examined axial and coronal T1-weighted images of 14 iNPH patients and 12 age-matched controls. The narrowness of the CSF space at the high convexity/midline was blindly evaluated by five raters using a continuous confidence rating scale for receiver operating characteristic (ROC) analysis. Results Axial and coronal imaging accurately determined the presence of the narrow cisterns/sulci at the high convexity/midline and was capable of predicting probable/definite iNPH with a high degree of accuracy. there were also no significant differences in the detection of this finding between the axial and coronal images. Conclusion Both axial and coronal T1-weighted MRI can detect the narrow CSF space at the high convexity/midline accurately and may therefore facilitate clinicians in choosing a management strategy for iNPH patients.     

Clinical impact of the callosal angle in the diagnosis of idiopathic normal pressure hydrocephalus

The utility of measuring the corpus callosal angle (CA) for the diagnosis of idiopathic normal pressure hydrocephalus (INPH) was investigated. Three-dimensional magnetic resonance imaging (MRI) was performed in 34 INPH patients, 34 Alzheimer’s disease (AD) patients, and 34 normal control (NC) subjects. Measurement of the CA on the coronal MR images of the posterior commissure perpendicular to the anteroposterior commissure plane was performed for all subjects. The CA of the INPH group (mean ± SD, 66 ± 14°) was significantly smaller than those of the AD (104 ± 15°) and NC (112 ± 11°) groups. When using the threshold of the mean − 2SD value of the NC group (= 90°), an accuracy of 93%, sensitivity of 97%, and specificity of 88% were observed for discrimination of INPH from AD patients. Measuring the CA helps in differentiating INPH patients from AD and normally aged subjects.     

抑郁症患者脑白质纤维的各向异性变化

目的：探讨MRI DWI上抑郁症患者脑白质纤维的各向异性特征。方法：对9例抑郁症患者以及与患者组年龄、性别相匹配的10例志愿者（对照组）行MR扩散张量成像（DTI）。记录额叶、颞叶、枕叶和胼胝体白质的各向异性分值（FA值）。结果：抑郁症患者左右额叶上中下部、左右颞叶、胼胝体压部的脑白质FA值均低于对照组,差异有显著性意义（P〈0.05）。结论：抑郁症患者的额叶和颞叶的白质纤维束FA值比正常人低,而且左右侧不对称。