Temporal Imaging Dynamics in ischemic Stroke: Intensity- vs. volume-based metrics.

Area of Science:

• Neurology
• Radiology
• Biomedical Imaging

Background:

• The progression of ischemic tissue damage after a thromboembolic occlusion is influenced by hypoperfusion and reperfusion timing.
• Temporal dynamics of hypoperfusion and tissue damage in acute ischemic stroke remain incompletely understood.

Purpose of the Study:

• To compare the association between onset-to-imaging time and volumetric versus intensity-based imaging markers in acute ischemic stroke.
• To investigate how different imaging modalities (CT and MRI) and metrics reflect tissue damage over time.

Main Methods:

• Retrospective analysis of 288 CT and 275 MR acute stroke examinations.
• Estimation of hypoperfusion and infarct core volumes using VEOcore software with standard thresholds.
• Quantification of tissue damage using ASPECTS and normalized signal intensities (NCCT, ADC, DWI, CBF, Tmax).
• Multivariable linear regression was used to assess associations with onset-to-imaging time, adjusting for covariates.

Main Results:

• Volumetric measures showed limited time-dependence: ASPECTS decreased by -0.33 points/h and ADC-core volume increased by +1.8 mL/h.
• Perfusion-related volumetric measures (CBF < 30%, Tmax > 6s) did not significantly change with time.
• Intensity measures demonstrated significant time-dependence: NCCT intensity decreased by -1.1%/h, ADC intensity by -0.69%/h, while DWI-b0 and DWI-b1000 increased by +2.3%/h and +4.9%/h, respectively.

Conclusions:

• Tissue signal intensities in acute ischemic stroke exhibit a stronger time-dependence compared to volumetric measures.
• Infarct evolution appears to reflect progressive tissue injury rather than solely volumetric expansion.
• Intensity-based metrics from NCCT and DWI may be more suitable for assessing "infarct growth rate" than perfusion-based metrics.