Altered diffusion tensor in multiple sclerosis normal-appearing brain tissue: cortical diffusion changes seem related to clinical deterioration

PURPOSE: To investigate normal-appearing white (NAWM) and cortical gray (NAGM) matter separately in multiple sclerosis (MS) in vivo using diffusion tensor imaging (DTI). MATERIALS AND METHODS: In 64 MS patients (12 primary progressive [PP], 38 relapsing remitting [RR], 14 secondary progressive [SP]) and 20 healthy controls, whole-brain apparent diffusion coefficient (ADC) and fractional anisotropy (FA) maps were acquired. A stimulated echo acquisition mode (STEAM) DTI sequence was used with minimal geometrical distortion in comparison to echo-planar imaging (EPI). NAWM and NAGM were identified using conventional magnetic resonance (MR) images, allowing a cautious assessment of FA in cortex. RESULTS: Histogram analyses showed significant global FA decreases and ADC increases in MS NAWM compared to control WM. MS cortical NAGM had no significant global ADC increase, but FA was decreased significantly. In regional analyses, nearly all NAWM regions-of-interest (ROIs) had significantly increased ADC compared to controls, but FA was not changed. In nearly all cortical NAGM ROIs, ADC was significantly increased and FA significantly reduced. In multiple linear regression analyses in RR/SPMS patients, NAGM-ADC histogram peak height was associated more strongly with clinical disability than T2 lesion load. CONCLUSION: Tissue damage occurs in both NAWM and cortical NAGM. The cortical damage appears to have more clinical impact than T2 lesions.     

Improved detection of enhancing and nonenhancing lesions of multiple sclerosis with magnetization transfer.

PURPOSETo determine whether magnetization transfer imaging can improve visibility of contrast enhancement of multiple sclerosis plaques.METHODSFifty-nine enhancing and 63 nonenhancing lesions in 10 patients with multiple sclerosis were evaluated to calculate contrast-to-noise ratios on conventional T1-weighted and T1-weighted magnetization transfer images. The signal intensity of the lesion and the background (white matter) were measured on precontrast T1-weighted and T1-weighted magnetization transfer images (800/20/1 [repetition time/echo time/excitations]) and on postcontrast T1-weighted and T1-weighted magnetization transfer images. Mean contrast-to-noise ratios was calculated for all lesions.RESULTSThe contrast-to-noise ratio was significantly higher for enhancing and nonenhancing lesions on T1-weighted magnetization transfer images than on conventional T1-weighted images. For enhancing lesions, the contrast-to-noise ratio was significantly higher on postcontrast T1-weighted magnetization transfer images, 32 +/- 2 compared with 21 +/- 2 on conventional T1-weighted images. Fifty of the 59 enhancing lesions were seen on both the T1-weighted and the T1-weighted magnetization transfer images. Nine enhancing lesions were seen only on the postcontrast T1-weighted magnetization transfer images. In addition, of 63 nonenhancing lesions seen on proton-density, T2-weighted, and T1-weighted magnetization transfer images, 16 were not seen on the conventional T1-weighted images. Seven of the 63 nonenhancing lesions and 7 of the 59 enhancing lesions had high signal intensity on the precontrast T1-weighted magnetization transfer images suggestive of lipid signal, a finding not seen on the conventional precontrast T1-weighted images.CONCLUSIONMagnetization transfer improves the visibility of enhancing multiple sclerosis lesions, because they have a higher contrast-to-noise ratio than conventional postcontrast T1-weighted images. High signal intensity on both nonenhancing and enhancing lesions noted only on precontrast T1-weighted magnetization transfer suggests a lipid signal was unmasked. If magnetization transfer is used in multiple sclerosis patients, a precontrast magnetization transfer image is necessary.     

Quantitative diffusion measurements in focal multiple sclerosis lesions: correlations with appearance on TI-weighted MR images

OBJECTIVE: Relative hypointensity on T1-weighted MR imaging has been suggested as a putative disability marker. The purpose of our study was to determine if there are quantifiable diffusion differences among focal multiple sclerosis lesions that appear differently on conventional T1-weighted MR images. We hypothesized that markedly hypointense lesions on unenhanced T1-weighted images would have significantly increased diffusion compared with other lesions, and enhancing portions of lesions would have different diffusion compared with nonenhancing lesions. SUBJECTS AND METHODS: Average apparent diffusion coefficient (ADC) was calculated for 107 lesions identified on T2-weighted images in 16 patients with multiple sclerosis and was compared with the ADC of normal white matter in 16 age- and sex-matched control subjects. Seventy-five nonenhancing lesions (29 isointense, 46 hypointense) and 32 enhancing lesions (6 isointense, 26 hypointense) were categorized on the basis of unenhanced T1-weighted MR imaging. RESULTS: Hypointense and isointense nonenhancing lesions both showed significantly higher ADC than normal white matter (p < 0.0001). Hypointense nonenhancing lesions showed higher ADC values than isointense nonenhancing lesions (p < 0.0001). Diffusion in enhancing portions of enhancing lesions was decreased when compared with nonenhancing portions. CONCLUSION: Quantitative diffusion data from MR imaging differ among multiple sclerosis lesions that appear different from each other on T1-weighted images. These quantitative diffusion differences imply microstructural differences, which may prove useful in documenting irreversible disease.     

Gd-DTPA-enhanced MR of suspected spinal multiple sclerosis

A prospective study was undertaken to evaluate the potential of Gd-DTPA-enhanced MR to differentiate active from inactive demyelinating lesions of the cervical spinal cord. Five patients with elongated high-signal-intensity lesions in the cervical cord on long TR/TE spin-echo MR images and a clinical suspicion of demyelinating disease had MR before and after IV Gd-DTPA. Delayed contrast enhancement (after 45-60 min) of the lesions was seen on short TR/TE images in two patients with clinically active disease, but no enhancement could be detected in three patients with stable disease. The patients with active disease underwent repeated MR examinations until the enhancement disappeared. The decrease in Gd-DTPA enhancement paralleled a decrease in clinical signs and symptoms of cervical myelopathy. MR is useful in evaluating patients suspected of having demyelinating disease. The MR finding of asymptomatic lesions in the brain lends support to the diagnosis of multiple sclerosis. Other possible causes of myelopathy, such as spinal cord compression and intramedullary tumor, can be excluded with the use of MR.     

多发性硬化患者弥散张量成像及其与认知功能的关系

目的: 探讨多发性硬化(MS)患者脑内病灶及脑组织的MR弥散张量成像(DTI)特点及其与认知功能的关系.材料和方法:对7例MS患者进行韦氏智力量表测查及头颅DTI检查.结果:病灶、病灶周围看似正常的组织(PWM)、看似正常的白质(NAWM)及看似正常的灰质(NAGM)较对照组相应部位脑组织的表观扩散系数(ADC)值增高,各向异性(FA)值减低.有智能损害的MS患者的NAWM、NAGM的ADC值高于智能正常的患者;而其NAGM的FA值低于智能正常的患者.结论:PWM、NAWM及NAGM组织内存在结构与功能改变,并影响认知功能.DTI有助于发现认知改变的微小结构和功能的异常.     

Single-dose gadolinium with magnetization transfer versus triple-dose gadolinium in the MR detection of multiple sclerosis lesions.

PURPOSETo compare the efficacy of single-dose gadolinium with magnetization transfer contrast (MTC) with that of triple-dose gadolinium in detecting enhancing multiple sclerosis lesions.METHODSTwenty-one patients with multiple sclerosis were examined with MR imaging first with 0.1 mmol/kg gadolinium (single dose) and then, after 24 to 72 hours, with 0.3 mmol/kg gadolinium (triple dose). T2-weighted fast spin-echo and T1-weighted spin-echo MR images with and without MTC were obtained before contrast administration followed by either T1-weighted spin-echo images with MTC (single dose) or conventional T1-weighted spin-echo images (triple dose), starting 5, 17, and 29 minutes after contrast administration. All images were evaluated in a blinded fashion and scored in random order by two readers. Outcome parameters included number of enhancing lesions, number of active MR examinations (those containing at least one enhancing lesion), contrast ratio (signal intensity of enhancing lesion divided by signal intensity of normal-appearing white matter), and size of enhancing lesions.RESULTSEighty-one percent more enhancing lesions and 49% more active MR examinations were detected when a triple dose of gadolinium was used as compared with a single dose. The level of agreement between readers as to the number of enhancing lesions was significantly higher for triple-dose than for single-dose gadolinium. With triple-dose gadolinium, contrast ratios and areas of enhancement increased by 10% and 33%, respectively. Delayed imaging increased the size of the lesion by 11% on single-dose MTC images and by 18% on triple-dose images.CONCLUSIONTriple-dose gadolinium is more effective (higher sensitivity and interobserver agreement) than single-dose gadolinium in combination with MTC in detecting enhancing multiple sclerosis lesions.     

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   

Dynamic susceptibility contrast perfusion MR imaging of multiple sclerosis lesions: characterizing hemodynamic impairment and inflammatory activity

BACKGROUND AND PURPOSE: Perfusion measurement in multiple sclerosis (MS) may cast light on the disease pathogenesis and lesion development since vascular pathology is frequently demonstrated in the disease. This study was performed to investigate the perfusion characteristics in MS lesions using dynamic susceptibility contrast MR imaging (DSC-MRI) to better understand the hemodynamic changes in MS. METHODS: Seventeen patients with relapsing-remitting MS were studied with DSC-MRI. Perfusion measurements included cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT), were obtained in enhancing, non-enhancing lesions covered by DSC-MRI and contralateral normal appearing white matter (NAWM) in patients as well as normal white matter in seventeen control subjects. RESULTS: DSC-MRI data demonstrated reduced perfusion with significantly prolonged MTT (P < 0.001) in lesions and NAWM in patients compared with normal white matter in controls. Compared to contralateral NAWM, enhancing lesions demonstrate increased CBF (P = 0.007) and CBV (P < 0.0001), indicating inflammation-mediated vasodilatation. A K means cluster analysis was performed and identifies approximately 63.8% of non-enhancing lesions (Class 1) with significantly decreased perfusion (P < or = 0.0001) when compared with contralateral NAWM. In contrast, the remainder 36.2% non-enhancing lesions (Class 2) show increased CBV (P = 0.02) in a similar fashion to enhancing lesions and can be observed on quantitative color-coded maps even without blood-brain barrier breakdown. CONCLUSION: DSC-MRI measurements demonstrate potential for investigating hemodynamic abnormalities that are associated with inflammatory activity, lesion reactivity and vascular compromise in MS lesions. Non-enhancing lesions showed both low and high perfusion suggesting microvascular abnormalities with hemodynamic impairment and inflammatory reactivity that cannot be seen on conventional MRI.     

临床孤立综合征和复发缓解型多发性硬化患者表现正常脑白质及脑灰质的MR扩散张量直方图比较

目的 评价扩散张量成像(DTI)对临床孤立综合征(CIS)的研究价值,了解CIS的病理变化机制及与复发缓解型多发性硬化(RRMS)的关系.方法 选择19例CIS患者(CIS组)、19例RRMS患者(RRMS组)和19例性别、年龄与之匹配的健康志愿者(正常对照组)为研究对象.用1.5 T超导型MR机采集数据,经图像后处理得到表现正常脑白质(NAWM),表现正常脑灰质(NAGM)的平均扩散率(MD)、各向异性分数(FA)直方图,其中提取出下列指标:平均值、直方图峰高和峰位置,进行单因素方差分析和秩和检验,并对3组NAWM、NAGM的MD、FA值与扩展残疾状态量表(EDSS)评分进行Spearman相关分析.结果 RRMS组患者表现正常脑白质MD为(0.83±0.04)×10-3mm2/s,较正常对照组(0.78±0.02)×10-3mm2/s、CIS组(0.79±0.02)×10-3mm2/s均显著增高(F=15.304,P＜0.01),但CIS组与正常对照组间差异无统计学意义(P＞0.05);MD图峰高CIS组明显低于正常对照组(P＜0.01);RRMS组平均FA值(0.36±0.03)较正常对照组(0.41±0.01)及CIS组(0.40±0.02)均降低(F=17.965,P＜0.01),但CIS组与正常对照组间差异无统计学意义(P＞0.05),平均FA图峰位置CIS组较正常对照组明显左移.NAGM MD在正常对照组、CIS组、RRMS组分别为(1.03±0.05)、(1.08±0.06)、(1.18±0.12)×10-3mm2/s,依次增高,且差异均有统计学意义(F=15.261,P＜0.01).CIS患者的各项DTI指标与EDSS评分均无显著性相关.RRMS患者NAGM的MD与EDSS评分呈正相关(r=0.568,P＜0.05).结论 DTI直方图可以敏感的显示及量化CIS及多发性硬化(MS)NAWM、NAGM的异常,作为MS最早期表现的CIS患者NAWM、NAGM均已发生了病理改变,但较MS病变轻.     

Gd-DTPA-enhanced short repetition time and short inversion time inversion recovery magnetic resonance imaging. Experimental and clinical assessment

To suppress both water and fat signal while retaining the high signal of Gd-DTPA enhancement, magnetic resonance imaging (MRI) of phantoms and 28 patients with mass lesions was done using short repetition time (TR) and short inversion time inversion recovery (STIR) sequences. Optimal STIR pulse sequences of 500 to 1000/80-100/20-30 (TR/TI/TE) were determined by an experimental study. In most instances, a signal bandwidth of +/- 8 kHz was used to increase the signal-to-noise ratio. The authors measured image contrast between lesions and adjacent fatty tissue and compared postcontrast STIR and T1-weighted spin-echo (T1-W SE) images. When the signal intensity of a lesion is 80% of adjacent fatty tissue on postcontrast T1-W SE, short TR STIR images provide better tumor delineation.     

Gd-DTPA in clinical MR of the brain: 1. Intraaxial lesions

Over 35 intraaxial lesions in 15 patients suspected of having intracranial tumors were studied with MR before and after injection of Gadolinium-DTPA (Gd-DTPA). Diseases included primary and metastatic brain tumors, plaques of multiple sclerosis, occult arteriovenous malformations, lymphoma, toxoplasmosis, and pituitary adenoma. The precontrast T2-weighted sequence (SE 2000/30, 60) was found to be most sensitive in detecting intraaxial lesions, showing 17 lesions that were not seen on the post-Gd-DTPA T1-weighted sequence (SE 500/30). In one case of multiple sclerosis, several lesions seen on the pre-Gd-DTPA study on T2-weighted images faded after injection of Gd-DTPA (due to T2 shortening). In two patients with large metastatic foci, other small metastatic lesions were seen better after Gd-DTPA on both T1- and T2-weighted sequences. Four other patients with only one focal-enhancing lesion and one patient with multifocal lesions on T1-weighted images actually had a much larger single glioma depicted on pre-Gd-DTPA T2-weighted images. In a patient with AIDS, a ring-enhancing lesion thought to be an abscess proved to be lymphoma. The cryptic arteriovenous malformations enhanced but showed more characteristic findings, such as hemorrhage, on pre-Gd-DTPA studies. Our experience suggests that Gd-DTPA may not improve sensitivity of MR in the detection of intraaxial lesions. However, functional aspects of brain disease, such as the presence of perfusion of a lesion and active breach of the blood-brain barrier, are depicted well with Gd-DTPA and are vital for proper diagnosis in many instances.     

Multiple sclerosis: serial study of gadolinium-enhanced MR imaging

Thirteen patients with definite multiple sclerosis (MS), studied 16-24 months previously with magnetic resonance (MR) imaging with and without enhancement by intravenously administered gadolinium diethylenetriaminepentaacetic acid (DTPA) dimeglumine, were reexamined with a similar protocol. Assessment of enhancement and clinical activity in both studies revealed that enhancement was observed in 13 of 14 cases in which clinical activity had changed within 4 weeks of the study and thus appeared more sensitive than clinical examination in determining active disease. The 3-minute postinjection, short repetition time image (TR) was the most efficient for depicting enhancement. Enhancing lesions (active plaques) arose from previously hyper- or isointense regions on long TR images. Previously active lesions reverted to areas of iso- or hyperintensity on long TR images. Serial comparison of long TR images in this population reveals a decrease in high-intensity lesions on long TR images in some cases and an increase in others. The findings of high-intensity regions on long TR images and previously enhancing lesions both becoming isointense suggests that transient inflammatory changes with concomitant edema without demyelination and/or with significant remyelination may occur in some MS lesions. MS lesions are dynamic; both active and inactive lesions may show dramatic change on longitudinal MR imaging studies.     

The value of magnetization transfer in delineation and differentiation of intracranial lesions

Purpose: Determination of the value of magnetization transfer (MT) imaging in the detection of lesions by evaluating the contrast difference between MT and non-MT spin-echo (SE) images of different types of enhancing intra-axial lesions, and the assessment of the applicability of MT effect (MTE) on lesion characterization.Methods: Twenty-seven patients (ages 11 to 72) having 36 lesion consisted of 12 multiple sclerosis plaques, nine metastatic lesions, 12 glial tumours and three abscesses were studied on 1.0 T imager with Gd-DTPA enhanced non-MT and MT sequences by application of 1500 Hz off-resonance pulse. Signal-to-noise ratios (SNR) and contrast-to-noise ratios (CNR) obtained with both techniques were compared to assess contrast improvement. MT effect (MTE) was used to evaluate the degree of saturation produced and its variances were analysed for lesion characterization.Results: The difference between MT and non-MT images for CNR was significant for all lesion types (P<0.05). Compared to the non-MTs, there was 60% improvement in CNR on MT images. MTE was not diagnostically significant in lesion characterization due to marked overlapping of MTE values for different lesion types.Conclusions: With the parameters used, MT almost doubles the CNR of enhancing intra-axial lesions, obviating the use of high dose regimens.     

Multiple sclerosis: comparison of trace apparent diffusion coefficients with MR enhancement pattern of lesions

BACKGROUND AND PURPOSE: Diffusion-weighted MR imaging and the trace apparent diffusion coefficient (ADC) provide important structural information about tissues. The purpose of this study was to investigate the relationship between trace ADC values and the enhancement pattern of multiple sclerosis (MS) lesions. METHODS: Ninety-six lesions, identified in 24 patients with MS, were characterized by their enhancement pattern on contrast-enhanced T1-weighted MR images. There were 57 nonenhancing lesions (NELs), 28 homogeneously enhancing lesions (HELs), and 11 ring-enhancing lesions (RELs). The trace ADC means for each type of lesion and for normal-appearing white matter (NAWM) were calculated and compared using Student's t-test. RESULTS: The mean trace ADC values for HELs (mean, 7.7 x 1(-10) m2s(-1); SD, 1.4 x 10(-10) m2s(-1)) were less than those for RELs (mean, 1.2 x 10(-9) m2s(-1); SD, 3.5 x 10(-10)m2s(-1)) and NELs (mean, 1.3 x 10(-9) m2(s-1); SD, 2.6 x 10(-10) m2(s-1)). There was a significant difference between the mean trace ADC values of HELs and RELs as well as between those for HELs and NELs. There was also a significant difference in the mean trace ADC values between all lesion types and NAWM (mean, 6.9 x 10(-10) m2s(-1); SD, 5.0 x 10(-11) m2s(-1)). CONCLUSION: We found a predictable relationship between mean trace ADC and the pattern of enhancement in MS lesions, corresponding to reported histopathologic differences in myelination between lesion types and magnetization transfer ratios.     

Abnormal corpus callosum: a sensitive and specific indicator of multiple sclerosis

The authors investigated whether identification of corpus callosal (CC) involvement might increase the specificity of magnetic resonance (MR) imaging in differentiating multiple sclerosis (MS) from other periventricular white matter diseases (PWDs). They prospectively evaluated 42 patients with MS and 127 control patients with other PWDs. Ninety-three percent of the MS patients demonstrated confluent and/or focal lesions involving the callosal-septal interface (CSI). These lesions characteristically involved the inferior aspect of the callosum and radiated from the ventricular surface into the overlying callosum. CSI lesions were optimally demonstrated on sagittal long repetition time (TR)/short echo time (TE) images and frequently (45% of cases) went undetected on axial images. Only 2.4% of the control patients had lesions of the CC. The authors conclude that midsagittal long TR/short TE images are highly sensitive and specific for MS and that callosal involvement in MS is more common than previously reported.     

MR proton spectroscopy in multiple sclerosis.

PURPOSE: To elucidate the natural history of visualized MR abnormalities in patients with multiple sclerosis using proton spectroscopy. METHODS: MR imaging and proton spectroscopy (1H spectroscopy) were performed on 16 patients with clinically definite multiple sclerosis. All patients received gadopentetate dimeglumine (Gd-DTPA). RESULTS: Decreased levels of N-acetylaspartate (NAA) were demonstrated in 17 out of 21 lesions. No correlation was found between decreased NAA and Gd-DTPA enhancement. In five out of seven enhancing lesions, abnormal 1H spectra with extra peaks (termed marker peaks) at 2.1-2.6 ppm (ranging in absolute concentration from 10-50 mM protons) were observed. In nine out of 14 unenhancing lesions, no elevated marker peaks were observed. In the five other unenhancing lesions, the levels of these marker peaks were generally lower than the enhancing group. No correlation was found between the NAA levels and the levels of the marker peaks. We suggest two distinct biochemical processes: 1) decreased NAA reflecting neuronal cell loss, and 2) elevated marker peaks reflecting ongoing demyelination. CONCLUSIONS: Based upon these observations we infer that 1) the majority of enhancing lesions are demyelinating with extra peaks at 2.1-2.6 ppm representing a marker of this process, 2) enhancing lesions without this marker most likely represent edematous regions without significant demyelination, and 3) demyelination may be long in duration compared with transient blood-brain barrier disruption manifested by Gd-DTPA enhancement. Our results suggest that 1H spectroscopy has the ability to further categorize MR-demonstrated enhancing and unenhancing lesions in patients with multiple sclerosis and that it may be more sensitive than contrast enhancement in revealing the true time course of demyelination.     

Can nonenhancing white matter lesions in cancer patients be disregarded?

PURPOSE: To assess the risks and implications of assuming that white matter lesions in cancer patients that do not enhance with gadopentetate dimeglumine (Gd-DTPA) can be considered to be benign. METHODS: Gd-DTPA was administered prospectively to 131 consecutive patients with biopsy-proved extracranial malignancies referred for cranial MR imaging to exclude cerebral metastases over a 21/2-year period. From this initial group, 50 patients were identified who had focal nonenhancing lesions of the white matter on T2-weighted images, but no other findings to suggest metastatic disease. This cohort of 50 patients was then followed for at least 1 year to determine the risk and clinical implications of assuming these nonenhancing white matter lesions were benign. RESULTS: Thirty patients (60%) were alive and clinically free of cranial metastatic disease at least 1 year following their initial MR study (median follow-up time, 17 months). Twenty of the 50 patients (40%) died within 1 year of their study (median survival, 4.1 months). Review of clinic notes and hospital charts revealed no evidence for deterioration of neurologic status in any of these patients before death, and the cause of death in each case was ascribed to extracranial complications of their systemic malignancies. Eight of these 20 patients who expired had at least one follow-up cranial CT or MR scan before death showing no new cerebral metastases or change in the nonenhancing white matter lesions previously identified. In a single patient, however, follow-up MR scan revealed conversion of one of her several white matter lesions from nonenhancing to enhancing without appreciable change in its size on T2-weighted images. Unfortunately, this patient died 4 months later from surgical complications without interval change in her neurologic status nor pathologic proof of the nature of this lesion. CONCLUSIONS: White matter lesions in cancer patients that do not enhance with Gd-DTPA at the time of the initial MR study have a low probability of representing metastatic disease. Clinical management or final outcome will not likely be altered by assuming such lesions are benign.     

Evaluation of Gd-enhancement in brain MR of multiple sclerosis: image subtraction with and without magnetization transfer

The aim of our study was to test the possibility of using image subtraction in detecting enhancing lesions in brain MR scans with and without magnetization transfer (MT) in multiple sclerosis (MS). Ten MS patients underwent 1.5-T MR imaging of the brain with spin-echo T1-weighted sequences with and without MT, repeated after 0.1 mmol/kg of an usual two-compartment paramagnetic contrast agent (Gadoteridol, Gd-HP-DO3A). Precontrast images were subtracted from postcontrast. Enhancing lesions were counted on the postcontrast images only (post-Gd), comparing pre- and postcontrast images by direct visual control (pre/post-Gd), and on the subtracted images (SI) only. Without MT, 36 enhancing lesions were counted on post-Gd, 36 on pre/post-Gd, and 59 on SI; using MT, 69, 52, and 50, respectively. Significant differences were found for pre/post-Gd without MT vs SI without MT ( p=0.028) and vs pre/post-Gd with MT ( p=0.012) as well as for pre/post-Gd with MT vs post-Gd with MT ( p=0.028). With pre/post-Gd, MT allowed the detection of 1.6 enhancing lesions per patient more than without MT. Whereas the SI without MT allow the detection of an increased number of enhancing lesions, SI with MT do not. An off-site final assessment allowed calculation of sensitivity and positive predictive value as follows: without MT were 63 and 94% (post-Gd), 67 and 100% (pre/post-Gd), 96 and 88% (SI); and with MT were 93 and 73% (post-Gd), 96 and 100% (pre/post-Gd), 91 and 98% (SI), respectively. Thus, SI seem to increase the sensitivity without MT; moreover, they could be used to correct the pseudoenhancement that impair post-Gd images with MT.     

Long-term changes of magnetization transfer-derived measures from patients with relapsing-remitting and secondary progressive multiple sclerosis.

BACKGROUND AND PURPOSE: For cases of multiple sclerosis (MS), magnetization transfer (MT) imaging may provide more pathologically specific and accurate estimates of the disease process than does conventional imaging. In this study, we evaluated changes of the MT ratio (MTR) of newly enhancing lesions, the MTR of normal-appearing white matter (NAWM), the average lesion MTR, and the MT histogram-derived metrics during a 3-year follow-up period for patients with relapsing-remitting or secondary progressive MS. METHODS: Dual-echo, conventional spin-echo, and MT images were obtained from seven patients with relapsing-remitting MS, seven patients with secondary progressive MS, and five age- and sex-matched control subjects at the time of study entry and 1, 13, and 37 months later. RESULTS: Newly enhancing lesions in the patients with secondary progressive MS presented a more severe and significant MTR reduction during the follow-up period as compared with those in the relapsing-remitting group. In cases of secondary progressive MS, we also observed a significant reduction of the MTR values of the NAWM and a trend toward reduction of average lesion MTR values. The patients with MS had mean percentage changes of MT histogram-derived measures that were approximately two to 10 times higher than those of the control subjects. CONCLUSION: This preliminary 3-year follow-up study shows that newly enhancing lesions and NAWM in patients with secondary progressive MS have significantly lower MTR values than do those in patients with relapsing-remitting MS. It also shows that the tissue damage that remains after enhancement ceases is more severe in secondary progressive disease.     

Characteristics and pitfalls of contrast-enhanced, T1-weighted magnetization transfer images of the brain

RATIONALE AND OBJECTIVES: This study was undertaken to clarify the difference in signal pattern on contrast material-enhanced T1-weighted magnetic resonance (MR) magnetization transfer (MT) images between enhancing and nonenhancing lesions in various intracranial diseases and to determine the necessity of nonenhanced MT images for evaluating lesional contrast enhancement. MATERIALS AND METHODS: MR images of 116 patients who underwent nonenhanced T1-weighted imaging, nonenhanced MT imaging, and contrast-enhanced MT imaging were reviewed. The increase in signal intensity of lesions relative to normal brain was compared between nonenhanced T1-weighted images and contrast-enhanced MT images. Signal intensity of lesions was compared with that of the striate nucleus and white matter on contrast-enhanced MT images. True enhancement was determined by comparison with nonenhanced MT images. RESULTS: In all, 143 lesions, including 86 enhancing and 57 nonenhancing lesions, were identified among 63 patients. Almost all (99%) of the enhancing lesions were hyperintense to striate nucleus on contrast-enhanced MT images, and most (>87%) showed moderate to marked signal intensity increase from nonenhanced T1-weighted images to contrast-enhanced MT images. Most (>95%) of the nonenhancing lesions showed mild or no increase in relative signal intensity, and most (75%) were iso- or hypointense to striate nucleus on contrast-enhanced MT images. A few nonenhancing lesions (4%-6%), however, showed increase in signal intensity that was indistinguishable from true enhancement without comparison to non-enhanced MT images. CONCLUSION: Nonenhanced MT images should be obtained to assess pathologic enhancement accurately.