Use of mean apparent propagator (MAP) MRI in patients with acute ischemic stroke: A comparative study with DTI and NODDI

Purpose: To evaluate the Mean Apparent Propagator (MAP) MRI for processing multi-shell diffusion imaging in patients with acute ischemic stroke (AIS) and correlate to diffusion tensor imaging (DTI) and neurite orientation and dispersion density imaging (NODDI).

Methods: We enrolled patients with AIS from 1/2022 to 4/2024 who underwent multi-shell diffusion imaging on a 3.0-Tesla scanner to generate DTI, NODDI and MAP measures. Mean intensity and standard deviation (SD) were calculated for the infarcted regions-of-interest in b0, fractional anisotropy (FA), mean diffusivity (MD), intra-cellular volume fraction (ICVF), free water fraction (FWF), and orientation dispersion index (ODI), return to the origin probability (RTOP), return to the plane probability (RTPP), return to the axis probability (RTAP), propagator anisotropy (PA), q-space Mean Square Displacement (QMSD), and non-Gaussianity (NG).

Results: Twenty-two patients were included with an average age of 69.5 ± 13.5, mean NIHSS of 12.4 ± 7.7, and median infarct of 73.3 ± 10.1 ml. ICVF was correlated with RTPP (ρ = 0.82, p < 0.01), RTAP (ρ = 0.76, p < 0.01) and RTOP (ρ = 0.79, p < 0.01), ODI with PA (ρ = -0.83, p < 0.01), FWF with RTOP (ρ = -0.73, p < 0.01), RTAP (ρ = -0.69, p < 0.01), and RTPP (ρ = -0.73, p < 0.01), MD with RTPP (ρ = -0.80, p < 0.01), RTOP (ρ = -0.79, p < 0.01), and RTAP (ρ = -0.77, p < 0.01), FA with RTAP (ρ = 0.77, p < 0.01), RTOP (ρ = 0.67, p = 0.01), PA (ρ = 0.74, p < 0.01), and SD PA (ρ = 0.85, p < 0.01). Multivariable linear regression identified the SD QMSD (β = 0.406, p = 0.008), thrombectomy (β = 0.481, p = 0.002), and infarct volume (β = 0.292, p = 0.051) as predictive of stroke severity based on NIHSS.

Conclusions: Given its short processing time, MAP MRI is a valuable alternative with potential for clinical use in AIS.