Diffusion-derived vessel density (DDVD) for penumbra delineation in brain acute ischemic stroke: initial proof-of-concept results using single NEX DWI

Neuroimaging is a cornerstone in the diagnosis and treatment decision-making for brain acute ischemic stroke. A rapid and accurate diagnosis is the key, specifically for time-critical reperfusion therapies. Successful reperfusion of salvageable penumbra can reduce the extent of ischemic stroke and thus improve clinical outcomes, whereas reperfusion of irreversibly affected brain tissue is thought to be futile and may result in harm due to the risk of hemorrhagic transformation. For neuroimaging work-up of acute stroke, computed tomography (CT) is more commonly applied than magnetic resonance imaging (MRI), due to the wider availability of CT scanners in emergency settings. However, the CT perfusion readout thresholds to define infarct area remain controversial. Diffusion-weighted (DW) MRI remains the best imaging modality to define the infarct area. Low-cost portable MRI scanners are available in recent years. MRI diffusion-derived vessel density (DDVD) reflects <i>in vivo</i> microvascular status. The analysis of DDVD requires DW images of only two <i>b</i>-values (with one being <i>b</i>=0 s/mm² and the other being non-zero low <i>b</i>-value), with a significantly shorter scanning time than contrast enhanced CT/MRI. In this article, we describe our preliminary results of three brain acute ischemic stroke cases scanned with a DDVD protocol. These cases prove the concept that DDVD pixelwise map assessments of brain ischemic area/volume are consistent with perfusion CT results, and a combination of DDVD pixelwise map and high <i>b</i>-value DW image identify the exitance and the size of a penumbra.