P7

PATFERNS OF NORMAL MENINGEAL ENHANCEMENT ON 1.5 T MR IMAGING

~ , O. P. Eldevlk, M.D., L K. Cohen, M.D., University of Michigan Medical Center, Ann Arbor, MI

Pu _rpose: To evaluate the normal patteros of intraeranial meningeal and ependymal enhancement contrast-enhanced head MR scans.

Methoct¢.. The intraeranial meninges and ventrieular ependyma were evaluated prospectivaly on 177 eonsocutive pre-conWast and post-contrast coronal Tl-weighted 1.5-T MR scans. Enhancement was graded on a 6 point scale (range: no enhanceraont to diffuse, irregular enhancement) and correlated with clinical history in each ease.

Results: 115 scans showed a "normal" paUem of meningeal enhancement (either no enhencemen or only focal enhancement of a region on < 3 contiguous sections or < 2 ara on a single section). Of these patients. 80 had otherwise normal scans, 15 demonstrated minimal inwscranial abnormalities (areas of isehemic change, etc.) and 20 showed significant abnormalities (predominantly intra-aslal tumors).

62 sc .uns demonstra .t .ed. abnormal muaiageal enhenuament. Of thase, 55 demonstratad sigulfieent assocmted abnormaliues (tumors, shunts, post-operative) and 7 did not show any other iatrecrani abnormalities.

C t ~ l .usln.~: An abnorm.al, pattern of meningeal enhancement correlates highly ( p < .001) with slgnificent abnormalines on head MR scans. Therefore, significant intracranial

meningeal/epeodymal enhancement should prompt a search for an etiulogy/explenatiort (either on the . .c3tyrent man or in the patient's past medical history) as such enhancement should not be eoosldered a normal fmdthg.

P8

REPRESENTATION OF WHITE MA'ITER TRACTS ON MRI (FRONTAL, SAGITTAL AND HORIZONTAL PROJECTIONS), Mark Glazer, M.D., Ruth G. Ramsey, M.D., Keiichiro Kasai, M.D., Haruo Isoda. M.D., Ph.D., Noriko Murayama, M.D., Ph.D., George, s Salamon, M.D., The University of Chicago, Cldcago, IL Purpose: A 3D method of analysis of white matter has been proposed to follow dieir main tracts in normal or pathological subjects. Methods: Correlations have been made between an in vivo MR study and postmortem analysis of the brain with myelin stain. The in vivo MR examinations were made on a 1.5 T MR unit with I mm sections using spoiled gradient echo volume and spin echo imaging. A special program (vox tool) allowed us to follow any tract on three orthogonal planes. Results: The following pathways have been analyzed: Pyramidal and sensitive fibers to areas 1,2,3, visual pathways, cal]osal fibars, superior and inferior longitudinal bundles, and thalamocortlcal tracts. Conelnsions: Determination of some main white matter tracts may be of extreme importance in MRI analysis of disconnection syndromes such as conduction aphasia, in the surgery of epilepsy, in vascular diseases such as for differentiation between necrotic areas and damyellnallng areas. It is also useful for interpretation and understanding of PET end functional MRI (fMR1) studies with ' neuropsychologic tests.

P9

PHYSI OLOGICAL A C T I V A T I O N M E A S U R E D B Y Tc-99m H M P A O B R A ~ SPECT C O M P A R E D W I T H Q U A N T I T A T I V E Xe-133 tCBF. Geor~ Deutseh. Ph.D.. J.M. Mountz, M.D., Ph.D., H.G. Liu, M.S. University of Alabama at Birmingham Medical Center, Birmingham, AL

~ : The nonlinearity of Tc-99m I-IMPAO dis~ibufion at higher regional cerebral blood flow (rCBF) may affect its application to rCBF activation studies. We compared cortical rCBF changes observed on Te-99m I-IMPAO SPECT scuns with quantitative rCBF obtained using Xe-133 eleurance in 20 cerebrovascular disease patients who had vaseulur reserve testing using both Diamox (acetuzolamide) and CO2 vasodllatory stress tests. Methods: 740 MBq Te-99m H M P A O was injected 15 minutes after lg Diamox injection. SPECT scanning was then performed on an A D A C Gennsys camera. Quantitative rCBF studies were performed on a Novo 32e cerebrograph using 1 minute inhalation of Xe- 133 (10mCi/liter air) during 5% CO 2 stress testing. All subjects also had SPECT and Xe rCBF studies during a "resting" state. SPECT data was analyzed using an automated cortical ROI generator and compared to Xe rCBF values calculated over the same regions. Results: Diamox SPECT revealed asymmetries and focai defects during stress consistent with CO s Xe rCBF studies, but Xe rCBF was more sensitive to baseline asymmetries and minimal flow changes due to its absolute quantification. Conelualons: I-IMPAO SPECT allows accurate assessment of the brain topography involved in vasodilatory stress testing. Quantffieation provides additional information, however, and should be pursued with Xe SPECT methods.

PlO MRI OF TEMPORAL LOBE EPILEPSy: COMPARISON OF S E Q ~ C E S .

Authors: LeoJ. Wolanqkv. M.D.. T. Kate, B.S., J. A. Mal~ian, M.D., B. K. Praman~ MD, D. Marks, M.D., J. Pak, M.D., H-J.Lee, M.D. UMDNJ, Newark, New Jei~ey

Ptwtmse: Because of growing In,crest in seizure surgery for intractable temporal Inl~ epilepsy, arcurato IVJ~I dingnesis of hippocampal scleresis Is esserdlal. Various studt5 have showed differences in r~ults, which have depeaded, in part, on techniques employed. The purpose of this study was to cmnpare the effectiveness of four differeat MRI sequences.

The folinwing four MRI sequences were compared: Thin-section 3D Fomier Tramfform Spoiled Grant , t-Echo (SPGR) Tl-weighted images; High-resolution fast s0n-echa T2- weighted images; Ceaventional sp'm-echo Balanced imas~; and Narrow-bandwidth (4 kHz) ¢onvmtio~l spin-echo T2-weigMed Inmgrs. Each sequence was read separately by a reader banded to the ~a~msiz. R~ult~: The most effective sequemo~ were T2-FSE (sensltivit y : 100%; spt¢lfldty : 80%) and SPGR (mmedtivity : 86.7%; and spedlkity : $4.6%). Narrow handwldth 1"2 tended to be lem effective (Semitivtty : 78.6%; specificity : 71.4%). Bahmced hnages had poor Semlelvlty bee.ainu of poor distlm~n Of klppocampus from vemrlde.

Tl-weightod SPGR and T 2 - w ~ FSE tend to be the most effective seque~es for tha dlal~eets Of Idppeompal atrophy and appear to be ¢omplemeatary.

P l l EVALUATION OF OCULAR M~LANOMA: MRI OR ULTRASOUND? Kundan L. Gupt,% I~, D, Daisy Gupta, Bradey S. Shore, M.D Tulane University Medical Center, New Orleans, Louisiana Purpose: Delineating the optimal MR imaging sequences and usefulness of ul t rasound in evaluating ocular melanoma.

~Materials and Methods: lntraocular melanoma is the most common int raocular malignancy in adults accounting for 80% of pr imary ocular malignancies. Magnetic resonance imaging was compared to ul trasound in the efficacy of evaluating, detecting characterizing 183 ocular melanoma cases. The f indings, size of tumor , presence of re t ina l de tachment and hemorrhage are analyzed. Results: Heavily T-1 weighted sequences were considered more sensitive than ei ther T-2 or proton densi ty images in reveal ing informat ion regarding deeper lesions and providing superior contrast resolut ion and tissues characteristics. Ultrasound, however, is invaluable in that i t is cost effective, easily provided on an ou tpa t ien t basis and provides h igher resolution in detecting smaller lesions. Conc~lusiQn: MRI and US are both excellent imaging modali t ies in the medical care and foliow-up of the pre and post surgical ocular melanoma. Knowledge of each modali t ies effiG'tiy,and limitations facilitates optimal cost effective pat ient care.

P12 T c - 9 9 m HMPAO BRAIN SPECT IN CHILDHOOD NARCOLEPSY: EVALUATION OF ITEM, Non-REM, AND T H E AWAKE STATE. Elmer C. San Pedro. M.D,, LM. Mountz, M.D., Ph.D., M. Wise, M.D., H.G. Lin, M.S. University of Alabarna at Birmingham, Birmingham, AL.

Put'nose: The inability of accurately identifying the exact moment of tracer injection in relation to the sleep-wake state contributes to conflicting reports in the medical literature regarding rCBF changes in narcolepsy. We ased videe/EEG/polygraphic monituring to dccurocnt sleep states prior to tracer injeedon. Methods: Brain SPECT imaging was performed after three separate injections of Te-99m HMPAO (over a 3-5 day period) to evaluate brain activity during wakefulness, REM and Non-REM sleep in two children with narcolepsy. Results: Semi-quantitative analysis showed significant increases in global rCBF during NOn-REM (20%) and during REM (9%) sleep as compared to the awake state in the first subject. There was also significant hemispheric perf~sicu asymmetry during Non-REM, R>L (8.5%) and during REM L>R (5%) as compared to wakefulness. The second subject developed minor bemispheric perfusion asymmetries during REM and NOn-REM when compared to wakefulness. Conclusions: Although there were only two subjects in this study, our results demonstrate that semiquamitative brain SPECT coupled with video/EEG/polygraphic monituring is able to detect rCBF changes in each stage of the sleep-wake cycle and may be helpful in future studies of rCBF changes in narcolepsy and other sleep disorders.