The role of quantitative neuroimaging indices in the differentiation of ischemia from demyelination: an analytical study with case presentation.
OBJECTIVE
Differentiation of acute and subacute ischemic stroke lesions from acute demyelinating lesions of multiple sclerosis (MS) may not be possible on conventional magnetic resonance imaging (MRI). Both lesion types enhance on T1 with gadolinium (Gd) contrast and both are hyperintense on diffusion-weighted imaging (DWI). This study is an analysis of two quantitative MR indices: (1) calculated apparent diffusion coefficients (ADCs) and (2) T2 relaxation times (T2R) as means toward differentiating acute ischemic lesions from acute demyelinating lesions. Chronic ischemic and demyelinating lesions were evaluated for comparison as well.


METHODS
The MRI of nine patients with both acute and chronic ischemic lesions and six patients with both acute and chronic demyelinating lesions were analyzed for ADC and T2Rs. The indices were measured by manually placing regions of interest (ROIs) at the anatomic center of the acute lesion. Acute ischemic lesions were chosen by their hyperintensity on DWI and hypointensity on ADC mapping. Acute demyelinating lesions were selected by peripheral contrast enhancement after the administration of Gd. Computation of the ADC involved the diffusion coefficient on a region by region basis as follows: D = -(b(0)/b(1000))ln(S(b1000)/S(b0)), where S(b1000) is the signal intensity on DWI and S(b0) is the signal intensity on T2 with diffusion sensitivities of b(0) and b(1000), respectively. Computation of the T2R was made as follows: T2R = (TE(T2)--TE(PD))/(ln SI(PD)--ln SI(T2)), where TE is the echo time of the different pulse sequences, SI is signal intensity on the different echo sequences, and PD represents proton density sequence.


RESULTS
Twenty-nine acute ischemia, 27 acute demyelination, 28 chronic ischemia, and 43 chronic demyelination image sets were analyzed. The differences between ADC(acute infarct) (0.760) versus ADC(acute plaque) (1.106) were significant (p < 0.02). The differences between T2R(acute infarct) (235.5) versus T2R(acute plaque) (170.5) were also significant (p < 0.02).


CONCLUSIONS
ADC in combination with T2R is a useful tool to differentiate acute ischemic from acute demyelinating lesions. The use of these neuroimaging indices along with magnetic resonance spectroscopy metabolite ratios is then demonstrated in elucidating the pathophysiological mechanism for a case of delayed posttraumatic bilateral internuclear ophthalmoplegia.
Hoque
Romy
R
Department of Neurology, Louisiana State University Health Sciences Center, Shreveport, Louisiana 71103, USA.
Ledbetter
Christina
C
Gonzalez-Toledo
Eduardo
E
Misra
Vivek
V
Menon
Uma
U
Kenner
Meghan
M
Rabinstein
Alejandro A
AA
Kelley
Roger E
RE
Zivadinov
Robert
R
Minagar
Alireza
A
D000328:Adult; D001921:Brain / Q000473:pathology*; D001931:Brain Mapping; D003711:Demyelinating Diseases / Q000150:complications; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007511:Ischemia / Q000209:etiology / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000145:classification / Q000379:methods*; D008297:Male; D013997:Time Factors