MR exponential image in ischemic stroke: A preliminary evaluation

Abstract

Background and purposeMagnetic resonance (MR) diffusion images, including both the diffusion-weighted image (DWI) and the apparent diffusion coefficient (ADC), allow detection of cerebral ischemic lesions within minutes of onset, and the contrast within the image is based on microscopic motion of the water. A third type of diffusion image can be created, “the exponential image”. Our goals were to evaluate the ability of exponential image in reflecting the changes in both DWI and ADC and whether it can replace these two sets of images in cerebral infarction patients. Patients and methodsA total of 51 patients were enrolled in the study, 47 were included in the analysis, and four were excluded from the study. Conventional and DW MRI were performed in 47 patients. For each patient DWI, ADC maps, and exponential images were reviewed and the change in signal intensity of the lesion compared with the contralateral normal side was measured (rSI) as well as the changes in (rADC). ResultsThere was a significant change in the rSIDW and rSIExp in late subacute and chronic stages (p<.001), however, rADC showed a significant decrease (p<.001) in hyperacute and acute stages, followed by a significant increase (p<.001) in the late subacute and chronic stages. rSIExp was highly correlated with the change in the rADC values in different stages of infarction (r=.72, p<.001). However, the changes in the rSIDW correlated less closely with the change in the rADC values (r=.35, (p<.05)). ConclusionExponential image offers a simple, more accurate replacement for both sets (DWI and ADC), by combining the advantages of both sets.