A Method for Imaging the Ischemic Penumbra with MRI Using Intravoxel Incoherent Motion

Area of Science:

• Neurology
• Radiology
• Medical Imaging

Background:

• Assessing local cerebral blood flow (CBF) distal to occlusion in acute ischemic stroke is crucial for predicting infarct growth and treatment response.
• Dynamic susceptibility contrast (DSC) MRI with a local arterial input function (AIF) measures local-qCBF and reflects collateral supply.
• Intravoxel incoherent motion (IVIM) MRI offers a potential noncontrast alternative for measuring local-qCBF.

Purpose of the Study:

• To compare IVIM local-qCBF with DSC local-qCBF in the ischemic penumbra.
• To compare perfusion-weighted imaging/diffusion-weighted imaging (PWI/DWI) mismatch measurements.
• To determine if local-qCBF improves prediction of final infarct volume.

Main Methods:

• Eight preclinical canine middle cerebral artery occlusion experiments were conducted.
• IVIM, DSC, and DWI MRI were acquired 2.5 hours postocclusion.
• IVIM and DSC parameters were compared, including local-qCBF, and correlated with infarct volume measured at 2.5 and 4 hours.

Main Results:

• IVIM local-qCBF strongly correlated with DSC local-qCBF (R²=0.69) in the noninfarcted territory.
• Both IVIM and DSC local-qCBF strongly predicted final infarct volume (R²=0.61 and R²=0.78, respectively).
• IVIM PWI/DWI ratio correlated with infarct growth (R²=0.70).

Conclusions:

• Noncontrast IVIM measurement of local-qCBF shows promise in assessing collateral circulation.
• IVIM local-qCBF and PWI/DWI mismatch may enhance prediction of infarct growth in acute ischemic stroke.