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Magnetization Transfer Ratio (magnetization + transfer_ratio)
Selected AbstractsA Magnetization Transfer MRI Study of Deep Gray Matter Involvement in Multiple SclerosisJOURNAL OF NEUROIMAGING, Issue 4 2006Jitendra Sharma MD ABSTRACT Background/Purpose: Gray matter involvement in multiple sclerosis (MS) is of growing interest with respect to disease pathogenesis. Magnetization transfer imaging (MTI), an advanced MRI technique, is sensitive to disease in normal appearing white matter (NAWM) in patients with MS. Design/Methods: We tested if MTI detected subcortical (deep) gray matter abnormalities in patients with MS (n= 60) vs. age-matched normal controls (NL, n= 20). Magnetization transfer ratio (MTR) maps were produced from axial proton density, conventional spin-echo, 5 mm gapless slices covering the whole brain. Region-of-interest,derived MTR histograms for the caudate, putamen, globus pallidus, thalamus, and NAWM were obtained. Whole brain MTR was also measured. Results: Mean whole brain MTR and the peak position of the NAWM MTR histogram were lower in patients with MS than NL (P < .001) and mean whole brain MTR was lower in secondary progressive (SP, n= 10) than relapsing-remitting (RR, n= 50, P < .001) patients. However, none of the subcortical gray matter nuclei showed MTR differences in MS vs. NL, RR vs. SP, or SP vs. NL. Conclusions: The MTI technique used in this cohort was relatively insensitive to disease in the deep gray matter nuclei despite showing sensitivity for whole brain disease in MS. It remains to be determined if other MRI techniques are more sensitive than MTI for detecting pathology in these areas. [source] Magnetization transfer ratio as a predictor of malignancy in breast lesions: Preliminary resultsMAGNETIC RESONANCE IN MEDICINE, Issue 5 2008Ruth Helena Morais Bonini Abstract MRI is an important tool for investigating breast cancer. Although recognized as the method of choice for screening high-risk patients, and for other indications the role of MRI for lesion characterization remains controversial. Recently some authors have advocated the use of morphologic and postcontrast features for this purpose. Quantitative breast MRI techniques have not been applied extensively in breast diseases. Magnetization transfer (MT) is a quantitative MR technique commonly used to investigate neurological diseases. In breast diseases the use of MT has been limited to improving visualization of areas of enhancement in postcontrast images. The purpose of this study was to evaluate the feasibility and utility of MT in discriminating benign from malignant breast lesions. Fifty-two lesions, BIRADS 4 and 5, from 49 patients, were prospectively evaluated using the MT ratio (MTR). Patients were divided into two groups: benign and malignant lesions. The MTR of fat, pectoralis major muscle, fibroglandular tissue, and breast lesions were calculated. A statistically significant difference was found between MTR from benign and malignant lesions (P < 0.001). Preliminary results suggest that MT can be used to evaluate breast lesions. Further studies are necessary to better define the utility and applicability of this technique. Magn Reson Med 59:1030,1034, 2008. © 2008 Wiley-Liss, Inc. [source] Cerebral oedema in minimal hepatic encephalopathy due to extrahepatic portal venous obstructionLIVER INTERNATIONAL, Issue 8 2010Amit Goel Abstract Background: Minimal hepatic encephalopathy (MHE) has recently been reported in patients with extrahepatic portal venous obstruction (EHPVO). Aims: To evaluate brain changes by magnetic resonance studies in EHPVO patients. Methods: Blood ammonia level, critical flicker frequency (CFF), brain metabolites on 1H-magnetic resonance (MR) spectroscopy and brain water content on diffusion tensor imaging and magnetization transfer ratio (MTR) were studied in 31 EHPVO patients with and without MHE, as determined by neuropsychological tests. CFF and magnetic resonance imaging studies were also performed in 23 controls. Results: Fourteen patients (14/31, 45%) had MHE. Blood ammonia level was elevated in all, being significantly higher in the MHE than no MHE group. CFF was abnormal in 13% (4/31) with EHPVO and in 21% (3/14) with MHE. On 1H-MR spectroscopy, increased Glx/Cr, decreased mIns/Cr, and no change in Cho/Cr were noted in patients with MHE compared with controls. Significantly increased mean diffusivity (MD) and decreased (MTR) were observed in the MHE group, suggesting presence of interstitial cerebral oedema (ICE). MD correlated positively with blood ammonia level (r=0.65, P=0.003) and Glx (r=0.60, P=0.003). Discussion: MHE was detected in 45% of patients with EHPVO while CFF was abnormal in only 13%. ICE was present in 7/10 brain regions examined, particularly in those with MHE. Hyperammonaemia elevated cerebral Glx levels correlated well with ICE. Conclusions: MHE was common in EHPVO; CFF could identify it only in a minority. ICE was present in EHPVO, particularly in those with MHE. It correlated with blood ammonia and Glx/Cr levels. Hyperammonaemia seems to contribute to ICE in EHPVO. [source] Quantitative MRI-pathology correlations of brain white matter lesions developing in a non-human primate model of multiple sclerosisNMR IN BIOMEDICINE, Issue 2 2007Erwin L. A. Blezer Abstract Experimental autoimmune encephalomyelitis (EAE) induced with recombinant human myelin/oligodendrocyte glycoprotein in the common marmoset is a useful preclinical model of multiple sclerosis in which white matter lesions can be well visualized with MRI. In this study we characterized lesion progression with quantitative in vivo MRI (4.7,T; T1 relaxation time,±,Gd-DTPA; T2 relaxation time; magnetization transfer ratio, MTR, imaging) and correlated end stage MRI presentation with quantitative ex vivo MRI (formaldehyde fixed brains; T1 and T2 relaxation times; MTR) and histology. The histopathological characterization included axonal density measurements and the numeric quantification of infiltrated macrophages expressing markers for early active [luxol fast blue (LFB) or migration inhibition factor-related protein-14 positive] or late active/inactive [periodic acid Schiff (PAS) positive] demyelinating lesion. MRI experiments were done every two weeks until the monkeys were sacrificed with severe EAE-related motor deficits. Compared with the normal appearing white matter, lesions showed an initial increase in T1 relaxation times, leakage of Gd-DTPA and decrease in MTR values. The progressive enlargement of lesions was associated with stabilized T1 values, while T2 initially increased and stabilized thereafter and MTR remained decreased. Gd-DTPA leakage was highly variable throughout the experiment. MRI characteristics of the cortex and (normal appearing) white matter did not change during the experiment. We observed that in vivo MTR values correlated positively with the number of early active (LFB+) and negatively with late active (PAS+) macrophages. Ex vivo MTR and relaxation times correlated positively with the number of PAS-positive macrophages. None of the investigated MRI parameters correlated with axonal density. Copyright © 2006 John Wiley & Sons, Ltd. [source] Magnetization transfer ratio evolution with demyelination and remyelination in multiple sclerosis lesionsANNALS OF NEUROLOGY, Issue 2 2008Jacqueline T. Chen PhD Objective To assess demyelination and remyelination in vivo in acute gadolinium (Gd)-enhancing lesions of multiple sclerosis (MS). Methods We measured significant changes in magnetization transfer ratio (MTR) consistent with demyelination and remyelination of individual lesion voxels, as well as the mean normalized MTR over all lesion voxels during and after contrast enhancement, in MS patients participating in a 3-year Canadian trial assessing immunoablation and autologous stem cell transplantation for treatment of MS. Results The average mean normalized lesion MTR over all lesions exhibited partial recovery over 2 to 4 months after Gd enhancement. Voxel-based analysis demonstrated that approximately 70% of the initially enhancing lesion volume (GdLV) was left with stably low MTR over 39 months of evaluation. The percentage of the GdLV undergoing significant increases in MTR consistent with remyelination increased for approximately 7 months after enhancement and then stabilized at 21 %GdLV. Significant decreases in MTR consistent with demyelination were ongoing for approximately 33 months after enhancement, stabilizing at 9 %GdLV. The estimated error of these measurements, based on scan/rescan analysis, was less than 0.4 %GdLV. Interpretation We found significant changes in MTR consistent with demyelination and remyelination that followed different temporal evolutions and were ongoing in different lesion regions for at least 3 years after lesion formation. Ann Neurol 2008 [source] Diffusion-weighted imaging and magnetization transfer imaging of tardive and edentulous orodyskinesiaMOVEMENT DISORDERS, Issue 9 2008Abdesslem Khiat PhD Abstract Oral dyskinesias occur in elderly individuals in relation to drug use (tardive dyskinesia, TD) or edentulousness (edentulous orodyskinesia, EOD) but their characterization remains incomplete. Our aim was to investigate whether magnetic resonance techniques such as diffusion-weighted imaging (DWI) and magnetization transfer imaging (MTI) of the brain could be used to differentiate dyskinetic patients from control subjects. Eight drug-treated patients with TD, 12 EOD patients, 8 drug-treated patients without TD, and 10 control subjects were recruited and examined by DWI and MTI. Measurements in the caudate nucleus, putamen, and globus pallidus yielded globally different apparent diffusion coefficient (ADC) values between drug treated patients with TD and control subjects but the magnetization transfer ratios showed no significant variations. The discrimination between dyskinetic patients and control subjects offered by ADC values was however slightly poorer than the discrimination offered by the previously published choline/creatine ratios measured by MR spectroscopy in the basal ganglia. The results are consistent with the pathophysiological hypothesis of damage to cholinergic interneurons. © 2008 Movement Disorder Society [source] | ||||||||||