Percent infarct mapping: an R1-map-based CE-MRI method for determining myocardial viability distribution

Area of Science:

• Cardiovascular Imaging
• Biomedical Engineering
• Radiology

Background:

• Myocardial infarction (MI) management requires accurate infarct size assessment.
• Current signal intensity (SI)-based MRI methods may overestimate infarct size.
• Longitudinal relaxation-rate enhancement (DeltaR1) offers an intrinsic parameter for precise quantification.

Purpose of the Study:

• To introduce and validate a DeltaR1-based contrast-enhanced MRI (CE-MRI) method called percent infarct mapping (PIM).
• To quantify myocardial viability and infarct size following delayed persistent contrast agent (PCA) accumulation.
• To assess the accuracy and reproducibility of PIM compared to histochemistry.

Main Methods:

• Developed a DeltaR1-based PIM method for CE-MRI.
• Utilized a canine MI model (N=6) with a persistent contrast agent (PCA).
• Generated voxel-by-voxel R1 maps and calculated PI values at 24 and 48 hours post-PCA administration, validated with triphenyltetrazolium-chloride (TTC) histochemistry.

Main Results:

• PIM demonstrated significant correlations (P<0.01, R=0.97) with TTC-based infarct size measurements.
• Median deviations of PIM from TTC were minimal (1.01% at 24 hr, -0.53% at 48 hr).
• Median deviations from the true infarction fraction were low (1.23% at 24 hr, 0.49% at 48 hr), with no significant difference between 24 and 48 hr PIM.

Conclusions:

• DeltaR1-based PIM is an accurate and reproducible method for quantifying myocardial viability distribution.
• PIM enhances the clinical utility of CE-MRI for myocardial infarction assessment.
• This technique provides precise per-voxel percentage of infarcted tissue, improving patient management.