Acute human stroke studied by whole brain echo planar diffusion-weighted magnetic resonance imaging

Area of Science:

• Neuroimaging
• Radiology
• Medical Physics

Background:

• Acute cerebral ischemia, or stroke, is a time-sensitive medical emergency.
• Early detection of ischemic changes is crucial for timely intervention and improved patient outcomes.
• Conventional MRI techniques may not detect ischemic changes in the earliest hours.

Purpose of the Study:

• To utilize whole-brain echo planar magnetic resonance imaging (MRI) for identifying and characterizing diffusion abnormalities in acute cerebral ischemia.
• To assess the sensitivity of diffusion-weighted imaging (DWI) in detecting early ischemic lesions.

Main Methods:

• Studied 40 patients presenting with acute cerebral ischemia symptoms.
• Employed whole-brain echo planar DWI with varying diffusion sensitivities (max b = 1,271 sec/mm2).
• Measured apparent diffusion coefficients (ADC) and generated synthetic ADC maps.

Main Results:

• DWI identified hyperintense regions of decreased ADC in all patients who later developed infarction, preceding conventional MRI changes in cases <6 hours.
• Lesions as small as 4 mm were detectable.
• Mean ADC in ischemic regions was 56% of control values within 6 hours, remaining reduced for 3-4 days.
• ADC normalized and then elevated in later stages, distinguishing acute from chronic lesions.

Conclusions:

• DWI using echo planar imaging detects a unique physiological parameter sensitive to ischemic changes earlier than conventional MRI.
• This technique allows for early identification and characterization of acute ischemic lesions.
• DWI shows potential for quantitative studies in stroke pathophysiology and therapeutic evaluation.