Applications of diffusion/perfusion magnetic resonance imaging in experimental and clinical aspects of stroke

Abstract

The acute evaluation of stroke patients has undergone dramatic advances in the recent past. The increasing availability of novel magnetic resonance imaging (MRI) techniques, such as diffusion and perfusion MRI, provides a plethora of information to clinicians evaluating patients suspected of having an acute stroke. This review focuses on recent advances with experimental and clinical applications of perfusion and diffusion imaging and their utility in identifying potentially salvageable ischemic tissue in rat stroke model and stroke patients.

Figure 1

A, Cerebral blood flow (CBF) and apparent diffusion coefficient (ADC) maps at 30 and 180 minutes of permanent focal ischemic rat (ADC: 0 to 2 × 10⁻³ mm²/s; CBF: 0 to 3 mL/g/min.) B, Pixel-by-pixel CBF-ADC scatterplots of the left hemisphere (LH) and right hemisphere (RH) at 30 and 180 minutes after stroke. C, Lesion-volume evolution in permanent (n = 6) and temporary (60 minutes) (n = 6) occlusion rats, and their correlations with triphenyltetrazolium chloride (TTC) infarct volumes. D, Functional CBF-based magnetic resonance imaging maps of a normal (overlaid on anatomic images) and a stroke (overlaid on CBF images) rat. Bilateral forepaw somatosensory stimulation used 0.3 ms, 3 Hz, 6 mA under 1.1 % isoflurane [20] (cross-correlation coefficient of 0.3 [P < 0.05] to 0.8).

Figure 2

Representative diffusion magnetic resonance image (MRI) (panel A), perfusion MRI mean transit time (MTT) map (panel B), and magnetic resonance angiography (MRA) (panel C) from a stroke patient initially imaged 2.5 hours after stroke onset. These images demonstrate occlusion of the middle cerebral artery on MRA with a large area of hypoperfusion on MTT maps and only a small lesion of the diffusion MRI scan. The patient received intravenous tissue plasminogen activator. Reperfusion on the MRA and perfusion MRI with minimal expansion of the diffusion lesion, supporting successful thrombolysis and likely tissue salvage on images obtained 24 hours later (panels D, E, and F). (DWI—diffusion-weighted imaging.) (Courtesy of M. Selim, MD).