Verification of Pathologic ECV Estimated with Clinical T1 Mapping Methods Using an Isotope-based Reference

Area of Science:

• Cardiovascular Imaging
• Radiology
• Medical Physics

Background:

• Cardiac MRI T1 mapping sequences are clinically used to measure extracellular volume fraction (ECV).
• Accurate ECV measurement is crucial for diagnosing and managing various cardiac pathologies.
• Independent validation of these sequences against a reference standard is necessary.

Purpose of the Study:

• To verify the accuracy of clinically used cardiac MRI T1 mapping sequences for measuring ECV.
• To assess ECV measurement accuracy across a spectrum of pathologic values using an independent reference standard.
• To compare ECV measurements from different T1 mapping sequences (MOLLI and SASHA) against ex vivo SPECT.

Main Methods:

• Acute myocardial ischemia was induced in six pigs, followed by 7 days of reperfusion.
• In vivo ECV was measured using three modified Look-Locker inversion recovery (MOLLI) and one saturation recovery single-shot acquisition (SASHA) sequences.
• Ex vivo SPECT imaging with technetium 99m diethylenetriamine pentaacetic acid served as the reference standard for ECV calculation.

Main Results:

• All T1 mapping sequences demonstrated high correlation with the reference standard (r² range, 0.71-0.99).
• MOLLI 5(3)3 and MOLLI 5s(3s)3s sequences overestimated ECV in the infarct region compared to SPECT.
• All sequences, including SASHA, showed ECV overestimation in the remote myocardium compared to the reference standard.

Conclusions:

• Clinically used cardiac MRI T1 mapping sequences show high correlation with a radioisotope-based reference standard for ECV measurement.
• Certain MOLLI sequences may overestimate ECV in infarct and remote myocardial regions.
• This study validates the use of T1 mapping sequences for ECV quantification, highlighting potential biases in specific sequences.