Revisiting the Optimal Apparent Diffusion Coefficient Threshold for Ischemic Core Delineation.

Area of Science:

• Neuroimaging
• Stroke Research
• Medical Image Analysis

Background:

• The standard apparent diffusion coefficient (ADC) threshold for ischemic core delineation was established using older recanalization assessment timelines and without edema correction.
• Previous methods may overestimate the ischemic core due to delayed recanalization assessment and lack of vasogenic edema correction in follow-up imaging.

Purpose of the Study:

• To re-evaluate the optimal ADC threshold for delineating the ischemic core in patients with early recanalization after endovascular therapy (EVT).
• To assess the impact of edema correction (EC) and early follow-up imaging (≈24 hours) on ADC threshold determination.

Main Methods:

• Retrospective analysis of patients who underwent EVT with successful recanalization within 90 minutes and had ≈24-hour follow-up MRI.
• Manual delineation of baseline ischemic lesions and final infarcts (Infarct24h) on diffusion-weighted imaging (DWI).
• Application of nonlinear coregistration for edema correction (EC) and receiver operating characteristic analysis to determine the optimized ADC threshold (OptADC).

Main Results:

• The optimized ADC threshold (OptADC) with edema correction was 612 × 10^-6 mm²/s, with an area under the curve of 0.704.
• The median individual OptADC was 621.5 × 10^-6 mm²/s.
• The optimized threshold resulted in a marginally smaller baseline core volume compared to the reference threshold, with minimal clinical difference observed.

Conclusions:

• The optimized ADC threshold determined using stringent methodology (early recanalization, 24-hour follow-up MRI, EC) is comparable to the reference threshold.
• Methodological refinements, including edema correction, are crucial for future research on ADC core delineation in acute ischemic stroke.