Intravoxel incoherent motion perfusion imaging in acute stroke: initial clinical experience

Intravoxel incoherent motion (IVIM) imaging is an MRI perfusion technique that uses a diffusion-weighted sequence with multiple b values and a bi-compartmental signal model to measure the so-called pseudo-diffusion of blood caused by its passage through the microvascular network. The goal of the current study was to assess the feasibility of IVIM perfusion fraction imaging in patients with acute stroke. Images were collected in 17 patients with acute stroke. Exclusion criteria were onset of symptoms to imaging > 5 days, hemorrhagic transformation, infratentorial lesions, small lesions < 0.5 cm in minimal diameter and hemodynamic instability. IVIM imaging was performed at 3 T, using a standard spin-echo Stejskal-Tanner pulsed gradients diffusion-weighted sequence, using 16 b values from 0 to 900 s/mm(2). Image quality was assessed by two radiologists, and quantitative analysis was performed in regions of interest placed in the stroke area, defined by thresholding the apparent diffusion coefficient maps, as well as in the contralateral region. IVIM perfusion fraction maps showed an area of decreased perfusion fraction f in the region of decreased apparent diffusion coefficient. Quantitative analysis showed a statistically significant decrease in both IVIM perfusion fraction f (0.026 +/- 0.019 vs. 0.056 +/- 0.025, p = 2.2 center dot 10(-6)) and diffusion coefficient D compared with the contralateral side (3.9 A +/- 0.79 A center dot 10(-4) vs. 7.5 A +/- 0.86 A center dot 10(-4) mm(2)/s, p = 1.3 A center dot 10(-20)). IVIM perfusion fraction imaging is feasible in acute stroke. IVIM perfusion fraction is significantly reduced in the visible infarct. Further studies should evaluate the potential for IVIM to predict clinical outcome and treatment response.