Time dependence in diffusion MRI predicts tissue outcome in ischemic stroke patients

Area of Science:

• Neuroimaging
• Biomedical Engineering
• Radiology

Background:

• Reperfusion therapy is crucial for ischemic stroke treatment within 4-6 hours.
• Patient outcomes vary, with some benefiting from treatment up to 24 hours.
• Advanced imaging is needed to identify suitable candidates for extended reperfusion therapy.

Purpose of the Study:

• To investigate if time dependence in diffusion MRI can predict tissue outcome in ischemic stroke.
• To determine if diffusion MRI parameters can identify patients who benefit from delayed reperfusion therapy.

Main Methods:

• Diffusion MRI data acquired with multiple diffusion times in five non-reperfused stroke patients at 2, 9, and 100 days post-stroke.
• Derived maps of "rate of kurtosis change" (k), mean kurtosis, ADC, and fractional anisotropy.
• Compared diffusion parameters between lesions and normal-appearing tissue, and between infarcted and viable lesion tissue at day 100.

Main Results:

• Positive "rate of kurtosis change" (k) values observed in lesions on days 2 and 9 indicated diffusional exchange.
• High k values on days 2 and 9, low mean kurtosis on day 2, and low fractional anisotropy on day 9 predicted tissue infarction.
• ADC values alone did not accurately predict infarction by day 100.

Conclusions:

• Diffusion MRI time dependence is a more accurate predictor of ischemic stroke tissue outcome than ADC values.
• This diffusion time dependence may aid in identifying patients eligible for reperfusion therapy beyond the standard 6-hour window.