Resolution-dependent estimates of lesion volumes in MRI studies of the brain in multiple sclerosis

Clinical

and praclinical

diagnosis and dassitkation

of MS.

PATHOLOGICAL GLEANED BY SPECTROSCOPIC

O.R. Hommes

MECHANISMS IN CNS DEMYELINATION: AS SERIAL PROTON MAGNETIC RESONANCE IMAGING OF MULTIPLE SCLEROSIS

Wolinskv JS Narayana PA, Doyle TJ, Lindsey JW, University of Texas Houston, H&th Science Center, POE3 20708, Houston, TX 77225 USA Single voxel magnetic resonance spectroscopy studies of MS have generally analyzed metabolite change in regions of now activity defined by serial MRI or Gd enhancement. While providing valuable data, these correlations are biased to predefined MRI events. In order to determine the time course of regional changes in specific metabolites visualized by 2D MRS Imaging (MRSI) in MS and correlate these with MRI, serial MSRI in a predetermined anatomical region of interest. This should allow better appreciation of the metabolic events that underlie lesion formation. 25 patients with clinically definite MS and modest clinical deficits (EDSS O-4.0) underwent serial MRVMRSI at 4 - 10 week rmervals for up to 6 sessions each. They have completed 106 sessions to date, Dual echo, interleaved, 3mm thick, spin density and T2 weighted imaging was followed by 2D, multivoxel MRSI at T,=30 msec, from a 1 Scm X 8cm X 8cm tissue slab consistently located for each subject in the white matter above the lateral ventricles. 32X32 phase encoding steps yielded a nominal voxel size of 0.8 cc Following MRSI. Tl weighted images were obtained before and after Gd. Quantitative analysis showed rather stable choline (Ch), creatine (Cr), N-acetyl aspartate (NAA). inositol (In) and cytosolic protein/lipid (Li) metabolic maps in normal and most MS subjects over multiple sessions. Informative MS oases showed regional increases in Ch that could precede MRI-defined lesions, regional Increases in Li that often correlated with Gd-enhancements, but were also found with stable lesions and in the absence of MRI-defined lesions, and reversible regionally depressed NAA Serial MRSI provides a sensitive method of differentiating otherwise homogeneous MRI-defined lesions and reveals regronal metabolic derangements not visualized by MRI.

RESOLUTION-DEPENDENT

ESTIMATES

OF

LESION

VOLUMES

IN

MRI

CHARACTERIZING THE NATURAL HISTORY AND RESPONSE TO TREATMENT OF INDIVIDUALS WlTH MS VIA AUTOMATED MAGNETIC RESONANCE IMAGING QUANTITATION, AND QUANmATIVE MAGNE3-IZATION TRANSFER

STUDIES OFTHE BRAIN IN MULTIPLE SCLEROSIS.

&E&LB& *MA Horsfield. S Mammi. A Campr, C Pereira, B Colombo, G Comi. Depts of Neurology and Neuroradiology. IRCCS Osp S Raffaele, Universita dl hlilano (I). ‘Dept of Medical Phystcs. University of Leicester (UK).

In

this

multiple resonance

study,

sclerosis imaging

we (MS) (-1)

ROBERT

GROSSMAN, RADIOLOGY/NEURORADIOLOGY; WBm, NEUROLOGY, UNIVERSITY PENNSYLVANIA MEDICAL CENTER, PHILADELPHIA,

Our increasing ability to utilize MR to characterize MS lesions over trme in a quantitative and sensitive fashion impacts diagnosis, observations of natural history and of responses to putative treatments of MS.

investigated the relationship between lesion volumes measured from magnetic scans and image slice thickness.

The lesion volume was computed using a semi-automated thresholding technique from axial scans of the brain of varying slice thickness. Ten patients with definite MS entered the study and in all cases the computed lesion volume increased with decreasing slice thickness (p=O.Ol). Lesion volumes measured for scans with slice thickness of 3 mm were on average 8.8% (range=l-33%) greater than those measured for scans with slice thickness of 5 mm (p=O.O06). Linear extrapolation from our data allowed the lesion volume at very small slice thickness to be estimated; this was found to be on average 20% greater than that obtained using a slice thickness of 5 mm. Furthermom. there are considerable differences in the percentage change in lesion volume from patient-to-patient, and it would appear that there is a larger variation and

with

higher These

volume discrepancies

slice lesion data

might

thickness loads. suggest that

go between

some MRI

for

patients

inaccurancies

way and

towards clinical

with

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OF USA

We have taken two separate approaches to improve MR capability. First, in order to quantify lesion volume, we developed a volumetric technique using “fuzzy connectors” and 3DVIEWNX software. On long TR images it has an inter- and intra-reader variability of about 1% and takes about 10 minutes of operator time. We also can use a similar technique to quantify enhanced lesions. The goal of this work is to understand what relationship, if any, exists between lesion volume and clinical parameters including clinical classification. Results to date make it clear that planning a clinical trial should include stratification of patients by MR lesion volume prior to entry. The other approach, designed to increase specificity with respect to lesion structum, uses the technique of magnetization transfer. With this methodology, using animal model data for guidance. we can classify lesions as being primarily demyelinating or primarily edematous.

lesions

m measuring lesion accounting for the findings in MS patients,

Additionally, we have produced magnetization transfer histograms that enable us to quantify the extent of abnormality throughout the entire brain. We believe that this method can measure the total extent of abnormality in the normal appearing white matter (MR occult disease) as well as categorizing changes in the more obviously abnormal white matter.

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