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Published on: June 21, 2016
Comparing two methods for assessment of perfusion-diffusion mismatch in a rodent model of ischaemic stroke: a pilot
1Department of Radiology, University Hospitals, Catholic University of Leuven, Herestraat 49, B-3000 Leuven, Belgium.
Abstract:
This stroke experiment was designed to define the mismatch between perfusion-weighted imaging (PWI) and diffusion-weighted imaging (DWI) in MRI by applying early or instantly acquired PWI. Eight rats were induced with stroke through photothrombotic occlusion of the middle cerebral artery and scanned serially between 1 h and day 3 after induction using DWI and PWI with a 1.5 T MR scanner. The relative lesion volumes (rLV) on MRI and triphenyl tetrazolium chloride-stained specimens were defined as the proportion of lesion volume over brain volume. Discrepancies in the rLV between PWI- and DWI-derived apparent diffusion coefficient (ADC) maps were expressed by subtraction of the ADC from PWI, resulting in three possible patterns: (i) (PWI-ADC > 10% of PWI) denoting a mismatch; (ii) (-(10% of PWI)
Insights
This study defines MRI perfusion-weighted imaging (PWI) and diffusion-weighted imaging (DWI) mismatch in stroke models. Findings show PWI-DWI discrepancies evolve over time, with instant PWI being more adequate at day 3.
Area of Science:
- Neuroimaging
- Stroke Research
- Medical Physics
Background:
- Perfusion-weighted imaging (PWI) and diffusion-weighted imaging (DWI) are crucial MRI techniques for stroke assessment.
- Understanding the mismatch between PWI and DWI is vital for accurate diagnosis and treatment.
- Early or instant PWI acquisition may refine the detection of perfusion-diffusion discrepancies.
Purpose of the Study:
- To define and analyze the mismatch between PWI and DWI in a rat stroke model.
- To evaluate the evolution of PWI-DWI discrepancies using early (ePWI) and instant (iPWI) perfusion data compared to instant DWI (iADC).
- To determine the optimal PWI acquisition timing for characterizing stroke-related imaging patterns.
Main Methods:
- Photothrombotic middle cerebral artery occlusion was induced in eight rats.
- Serial MRI scans (DWI and PWI) were performed between 1 hour and 3 days post-induction.
- Relative lesion volumes (rLV) were calculated, and PWI-ADC discrepancies were categorized as mismatch, match, or reverse mismatch based on a 10% threshold.
Main Results:
- PWI-ADC discrepancies evolved over time from mismatch to match, then to reverse mismatch.
- A PWI-ADC mismatch persisted in 1-3 rats at 3 days post-occlusion.
- Instant PWI (iPWI) showed a higher mismatch rate within day 1, while early PWI (ePWI) was more indicative at day 3; iPWI was deemed more adequate at day 3.
Conclusions:
- Both ePWI and iPWI are useful for defining PWI-ADC patterns within the first day after stroke.
- Instant PWI (iPWI) provides a more adequate characterization of PWI-ADC patterns at 3 days post-stroke.
- The study highlights the dynamic nature of PWI-DWI mismatch and the importance of acquisition timing in stroke imaging.
