Faculty Bibliography

Image intensity standardization is a recently developed postprocessing method that is capable of correcting the signal intensity variations in MR images. We evaluated signal intensity of healthy and diseased tissues in 10 multiple sclerosis (MS) patients based on standardized dual fast spin-echo MR images using a numerical postprocessing technique. The main idea of this technique is to deform the volume image histogram of each study to match a standard histogram and to utilize the resulting transformation to map the image intensities into standard scale. Upon standardization, the coefficients of variation of signal intensities for each segmented tissue (gray matter, white matter, lesion plaques, and diffuse abnormal white matter) in all patients were significantly smaller (2.3-9.2 times) than in the original images, and the same tissues from different patients looked alike, with similar intensity characteristics. Numerical tissue characterizability of different tissues in MS achieved by standardization offers a fixed tissue-specific meaning for the numerical values and can significantly facilitate image segmentation and analysis

OBJECTIVE: To determine the relationship between gadolinium-enhancing lesions and changes in whole brain parenchymal volume in patients with relapsing-remitting MS, and to test the hypothesis that gadolinium enhancement is a predictor of whole brain atrophy. METHODS: Twenty-four patients with clinically definite MS were imaged over 2 years. A computer-assisted segmentation technique based on high-resolution MRI was used to quantify gadolinium-enhancing T1 lesion volume and brain parenchyma and CSF volumes. Percent brain parenchymal volume (PBV) relative to the total intracranial volume was calculated, and changes in PBV were used to represent the degree of whole brain atrophy over 2 years. RESULTS: PBV at baseline was dependent on duration of MS, and a significant decrease in PBV was observed over the course of the study. Changes in enhanced T1 lesion load failed to correlate with changes in PBV, and multiple regression analyses determined that enhanced T1 lesion load at baseline was not a significant predictor of subsequent change in PBV. CONCLUSIONS: MR visible inflammation as demonstrated by enhanced T1 lesions is not a significant factor in the pathogenesis of whole brain atrophy in relapsing-remitting MS, suggesting that a more global pathologic process is responsible for the loss of brain parenchymal volume

PURPOSE: To determine annual rates of volumetric changes in the whole-brain parenchyma of patients with relapsing-remitting and secondary progressive multiple sclerosis (MS) and test the hypothesis that these changes correlate with clinical disability. MATERIALS AND METHODS: A computer-assisted segmentation technique with thin-section magnetic resonance (MR) imaging was used in 36 patients with MS (27 relapsing-remitting, nine secondary progressive) and in 20 control subjects to quantify brain and cerebrospinal fluid volumes. To determine the degree of brain atrophy, the percentage brain parenchyma volume (PBV) relative to that of intracranial contents was calculated. RESULTS: At the beginning of the study, the PBV was smaller in the MS group than in the control group (P = .007); brain parenchyma volumes were similar. The median rate of brain volume loss was 17.3 mL per year in patients with relapsing-remitting MS and 23.6 mL per year in those with secondary progressive MS. There was a negative correlation between brain atrophy and Expanded Disability Status Scale (EDSS) score in patients with secondary progressive MS (r = -0.69, P = .004) and no correlation in patients with relapsing-remitting MS. T2 lesion volume did not correlate with brain atrophy in either group. CONCLUSION: The correlation between brain atrophy and EDSS score was better in patients with secondary progressive MS than in those with relapsing-remitting MS

OBJECTIVE: To evaluate the efficacy of glatiramer acetate (GA, Copaxone; Teva Pharmaceutical Industries, Ltd., Petah Tiqva, Israel) by MRI-based measures in patients with relapsing-remitting (RR) MS. METHODS: Twenty-seven patients with clinically definite RR-MS were treated with either 20 mg of GA by daily subcutaneous self-injection (n = 14) or placebo (n = 13) for approximately 24 months. Axial dual-echo fast-spin-echo T2-weighted images and T1-weighted images before and after gadolinium (Gd) were acquired at 1.5 tesla and transferred into an image processing computer system. The main outcome measures were the number of Gd-enhanced T1 and T2 lesions and their volume as well as brain parenchyma volume. RESULTS: The values of age, disease duration, Expanded Disability Status Scale (EDSS) score, the number of T1- and T2-weighted lesions, and their volume were similar between GA- and placebo-receiving groups at the entry of this study. There was a decrease in the number of T1-enhanced lesions (p = 0.03) and a significant percent annual decrease of their volume in GA recipients compared with those of placebo recipients. There were no significant differences between changes in the two groups in the number of T2 lesions and their volume. The loss of brain tissue was significantly smaller in the GA group compared with that of the placebo group. CONCLUSIONS: These results show that GA treatment may decrease both lesion inflammation and the rate of brain atrophy in RR-MS

OBJECTIVE: To quantitate the extent of neuronal cell loss in MS via the whole brain's N-acetylaspartate (NAA) concentration (WBNAA). METHODS: Because NAA is assumed to be present only in neuronal cell bodies and their axons, we measured WBNAA as a marker for viable neurons in 12 patients (9 women and 3 men, 26 to 53 years of age) suffering from relapsing-remitting (RR) MS for at least 5 years and compared them with 13 age- and sex-matched normal controls. Total brain NAA was determined with proton MR spectroscopy, and WBNAA was obtained by dividing it by the total brain volume, calculated from high resolution MRI. RESULTS: The WBNAA of the RR MS patients was lower than their matched controls (p<0.005). This difference was greater among older than younger subjects. The linear prediction equations of WBNAA with age indicate a faster, x10, decline in the patients, approximately 0.8% per year of age (p = 0.022). CONCLUSION: The age-dependent decrease of whole brain N-acetylaspartate (WBNAA) in the patients suggests that progressive neuronal cell loss is a cardinal feature of this disease. WBNAA offers a quick, highly reproducible measure of disease progression and may be an important marker of treatment efficacy in MS as well as other neurodegenerative diseases

BACKGROUND AND PURPOSE: The T1-weighted fast spin-echo (T1-FSE) MR imaging sequence is not used routinely, since the speed advantage is not as dramatic as it is in T2-weighted imaging. We evaluated the T1-FSE sequence to determine whether this technique can replace the conventional T1-weighted spin-echo (T1-SE) sequence for routine contrast-enhanced imaging. METHODS: Sixty-nine patients with intracranial enhancing lesions underwent both T1-SE and T1-FSE sequences in a random order after administration of contrast agent. Acquisition time was 55 seconds for the T1-FSE sequence and 2 minutes 38 seconds for the SE sequence. The conspicuity of enhancing lesions, peritumoral edema, and gray-to-white matter contrast as well as motion and flow artifacts were analyzed. Signal-to-noise ratios of enhancing lesions, gray matter, and white matter as well as contrast-to-noise ratios (CNRs) of enhancing lesions, with gray matter with white matter as the standard, were calculated. RESULTS: The conspicuity of enhancing lesions was better on T1-FSE sequences than on T1-SE sequences, although the difference in the CNRs of enhancing lesions did not reach significance. Images obtained with the T1-FSE sequence showed less flow and motion artifacts than did those obtained with the T1-SE sequence. The conspicuity of peritumoral edema and gray-to-white matter contrast was lower on the T1-FSE images than on the T1-SE images. CONCLUSION: The T1-FSE sequence reduces imaging time and has the potential to replace the conventional T1-SE sequence for the evaluation of enhancing lesions in the brain when time is a consideration

The purpose of this study was to evaluate the utility of diffusion-weighted magnetic resonance imaging (MRI) with echo-planar imaging (EPI) technique in depicting the tumor cellularity and grading of gliomas. Twenty consecutive patients (13 men and 7 women, ranging in age from 13 to 69 years) with histologically proven gliomas were examined using a 1.5 T superconducting imager. Tumor cellularity, analyzed with National Institutes of Health Image 1.60 software on a Macintosh computer, was compared with the minimum apparent diffusion coefficient (ADC) and the signal intensity on the T2-weighted images. The relationship of the minimum ADC to the tumor grade was also evaluated. Tumor cellularity correlated well with the minimum ADC value of the gliomas (P = 0.007), but not with the signal intensity on the T2-weighted images. The minimum ADC of the high-grade gliomas was significantly higher than that of the low-grade gliomas. Diffusion-weighted MRI with EPI is a useful technique for assessing the tumor cellularity and grading of gliomas. This information is not obtained with conventional MRI and is useful for the diagnosis and characterization of gliomas

OBJECTIVE: Our purpose was to evaluate the relationships between the ratio of maximum relative cerebral blood volume (rCBV) (rCBV ratio = rCBV[tumor]/rCBV[contralateral white matter]) and histologic and angiographic vascularities of gliomas using the gradient-echo echoplanar MR imaging technique. We also evaluated the usefulness of rCBV maps for grading gliomas. SUBJECTS AND METHODS: We examined 30 patients with histologically verified gliomas. Gliomas were classified as glioblastoma, anaplastic glioma with enhancement, anaplastic glioma without enhancement, and low-grade glioma. The maximum rCBV ratio of each glioma was compared with both histologic and angiographic vascularities, and the relationship between the maximum rCBV ratios and each type of glioma was established. RESULTS: The maximum rCBV ratios of the gliomas significantly correlated with both histologic and angiographic vascularities (p < .001). Mean values and SDs of maximum rCBV ratios of each type of tumor were 7.32+/-4.39 for glioblastomas, 5.84+/-1.82 for anaplastic gliomas with enhancement, 1.53+/-0.75 for anaplastic gliomas without enhancement, and 1.26+/-0.55 for low-grade gliomas. The maximum rCBV ratios of the glioblastomas were significantly higher than those of the anaplastic gliomas without enhancement (p = .002) and the low-grade gliomas (p < .001). The maximum rCBV ratios of the anaplastic gliomas with enhancement were higher than those of the anaplastic gliomas without enhancement and the low-grade gliomas, but the differences were not statistically significant (p = .08 and p = .03, respectively). CONCLUSION: The results of perfusion-sensitive MR imaging with gradient-echo echoplanar technique correlated with both histologic and angiographic vascularities

We used constructive interference in steady state (CISS) 3D Fourier transform (3DFT) MRI data sets to obtain three-dimensional (3D) virtual MRI endoscopic views of the intracranial cerebrospinal fluid (CSF) spaces, processing them with a commercially available perspective endoscopic algorithm. We investigated the potential of the intracranial virtual MRI endoscopy applied to visualisation of the pathology in 13 patients with surgically confirmed trigeminal neuralgia (3), hemifacial spasm (3), acoustic neuroma (3), suprasellar germinoma (1), Langerhans cell histiocytosis (1), lateral ventricle nodules (1) and pituitary dwarfism (1). All images were acquired using a 1.5-T imager employing a circular polarised head coil. The CISS-3DFT data sets were transferred to a workstation for processing with the perspective endoscopic algorithm. Postprocessing for virtual MRI endoscopy was possible for all data sets. The lesions in 12 patients, and their complex anatomical relationships with the surrounding structures, were well seen on the 3D images. A small acoustic neuroma in the internal auditory meatus was not seen using virtual endoscopy. Although virtual MRI endoscopy has limitations, it provides 3D images which cannot be acquired using any other procedure