Perfusion MR Imaging in Gliomas: Comparison with Histologic Tumor Grade

OBJECTIVE: To determine the usefulness of perfusion MR imaging in assessing the histologic grade of cerebral gliomas. MATERIALS AND METHODS: In order to determine relative cerebral blood volume (rCBV), 22 patients with pathologically proven gliomas (9 glioblastomas, 9 anaplastic gliomas and 4 low-grade gliomas) underwent dynamic contrast-enhanced T2*-weighted and conventional T1- and T2-weighted imaging. rCBV maps were obtained by fitting a gamma-variate function to the contrast material concentration versus time curve. rCBV ratios between tumor and normal white matter (maximum rCBV of tumor / rCBV of contralateral white matter) were calcu-lated and compared between glioblastomas, anaplastic gliomas and low-grade gliomas. RESULTS: Mean rCBV ratios were 4.90'+/-1.01 for glioblastomas, 3.97'+/-0.56 for anaplastic gliomas and 1.75'+/-1.51 for low-grade gliomas, and were thus sig-nificantly different; p < .05 between glioblastomas and anaplastic gliomas, p <.05 between anaplastic gliomas and low-grade gliomas, p < .01 between glioblas-tomas and low-grade gliomas. The rCBV ratio cutoff value which permitted dis-crimination between high-grade (glioblastomas and anaplastic gliomas) and low-grade gliomas was 2.60, and the sensitivity and specificity of this value were 100% and 75%, respectively. CONCLUSION: Perfusion MR imaging is a useful and reliable technique for esti-mating the histologic grade of gliomas.

Functional MR Imaging of Cerebral Auditory Cortex with Linguistic

PURPOSE: To obtain preliminary data for understanding the central auditory neural pathway by means of functional MR imaging (fMRI) of the cerebral auditory cortex during linguistic and non-linguistic auditory stimulation. MATERIALS AND METHODS: In three right-handed volunteers we conducted fMRI of auditory cortex stimulation at 1.5 T using a conventional gradient-echo technique (TR/TE/flip angle: 80/60/40 degree). Using a pulsed tone of 1000 Hz and speech as non-linguistic and linguistic auditory stimuli, respectively, images-including those of the superior temporal gyrus of both hemispheres-were obtained in sagittal plases. Both stimuli were separately delivered biaurally or monoaurally through a plastic earphone. Images were activated by processing with homemade software. In order to analyze patterns of auditory cortex activation according to type of stimulus and which side of the ear was stimulated, the number and extent of activated pixels were compared between both temporal lobes. RESULTS: Biaural stimulation led to bilateral activation of the superior temporal gyrus, while monoaural stimulation led to more activation in the contralateral temporal lobe than in the ipsilateral. A trend toward slight activation of the left (dominant) temporal lobe in ipsilateral stimulation, particularly with a linguistic stimulus, was observed. During both biaural and monoaural stimulation, a linguistic stimulus produced more widespread activation than did a non-linguistic one. CONCLUSION: The superior temporal gyri of both temporal lobes are associated with acoustic-phonetic analysis, and the left (dominant) superior temporal gyrus is likely to play a dominant role in this processing. For better understanding of physiological and pathological central auditory pathways, further investigation is needed.

Human Brain Mapping of Language-Related Function on 1.5T Magnetic Resonance System: Focused on Motor Language Function

PURPOSE: To investigate the feasibility of functional MR imaging of motor language function and its usefulnessin the determination of hemispheric language dominance. MATERIALS AND METHODS: In order to activate the motorcenter of language, six subjects(5 right-handed, 1 left-handed; 3 males, 3 females) generated words. They wererequested to do this silently, without physical articulation, in response to English letters presented visually.Gradient-echo images (TR/TE/flip angle, 80/60/40o; 64x128 matrix; 10mm thickness) were obtained in three axialplanes including the inferior frontal gyrus. Functional maps were created by the postprocessing of gradient-echoimages, including subtraction and statistics. Areas of activation were topographically analyzed and numbers ofactivated pixels in each region were compared between right and left sides. The reproducibility of functional mapswas tested by repetition of functional imaging in the same subjects. RESULTS: Statistically significant activationsignals were demonstrated in five of six subjects, in whom the distribution of those signals was predominantly inboth frontal lobes. Hemispheric lateralization of activation, when activated pixels were compared between bothinferior frontal gyri, was in all cases on the left. In four subjects, functional maps were reproduced in asimilar fashion. CONCLUSION: Our results suggest that functional MR imaging can depict the activation of motorlanguage function in the brain and can be used as a useful non-invasive method for determining the hemisphericdominance of language.

Functional Magnetic Resonance Imaging of the Brain: Principle and Practical Application

Functional magnetic resonance imaging is a promising imaging technique developed recently to obtain functional maps of the brain, and can be successfully performed on widely available diagnostic MR imaging systems. Thus, the technical principle and application of this new imaging are no more minor part of knowledge in radiology. We describe herein the overview of functional magnetic resonance imaging about the physiologic mechanism, imaging technique, image-processing method and practical application.

Blood Volume of Intraaxial Brain Tumor: Evaluation with Dynamic Contrast-Enhanced T2*-Weighted MR Imaging

PURPOSE: To evaluate the utility of dynamic contrast-enhanced T2*-weighted MR imaging in assessing the cerebral blood volume (CBV) in intra-axial brain tumors. MATERIALS AND METHODS: Ten malignant gliomas (five glioblastomas, three anaplastic astrocytomas, two anaplastic oligodendrogliomas), five metastatic tumors and three hemangioblastomas were included in this study. In conjunction with T1- and T2-weighted imagings, all patients underwent dynamic contrast-enhanced T2*-weighted imaging, using the conventional gradient-echo technique (TR/TE/flip angle: 40/26/10degree; 64x128 matrix; 5-6 mm thickness) during the bolus injection of 15 mmol/kg Gd-DTPA. From these dynamic images, CBV was calculated on a pixel-by-pixel basis and a CBV map was obtained. The CBVs of the tumor and contralateral normal white matter were measured by placing the ROI on the CBV map. The CBV ratios of tumor/normal white matter were compared among the three tumor groups. RESULTS: CBV maps were successfully created in all cases. CBV ratios varied from 1.7 to 13.0 (mean 6.1) in malignant gliomas, from 3.9 to 11.4 (mean 7.3) in metastatic tumors and from 17.8 to 26.4 (mean 22.2) in hemangioblastomas (malignant gliomas vs hemangioblastomas, p.05). CONCLUSION: Hypervascular hemangioblastomas have the highest CBV, and this allows for easy differentiation from malignant gliomas and metastatic tumors. Both show a similar, moderately increased range of CBV suggesting thatthere is no significant difference in vascularity between the two tumor groups. Dynamic contrast-enhanced T2* imaging is a clinically useful technique which provides information about tumor vascularity not provided by standard MRI techniques.