Phase-based vascular input function: Improved quantitative DCE-MRI of atherosclerotic plaques.

Area of Science:

• Cardiovascular Imaging
• Biomedical Engineering
• Radiology

Background:

• Quantitative pharmacokinetic modeling of dynamic contrast-enhanced (DCE)-MRI assesses atherosclerotic plaque microvasculature.
• Plaque microvasculature is a key indicator of plaque vulnerability.

Purpose of the Study:

• To compare magnitude-based vascular input functions (m-VIF) versus phase-based vascular input functions (ph-VIF) in pharmacokinetic modeling.
• To gain insight into the differences between m-VIF and ph-VIF through model calculations and flow phantom experiments.

Main Methods:

• Acquired population-averaged m-VIF and ph-VIFs from 11 patients with carotid plaques.
• Performed pharmacokinetic analysis in 17 additional patients.
• Conducted simulations using Bloch equations and flow phantom experiments to assess the impact of blood velocity on signal enhancement.

Main Results:

• Simulations and phantom experiments showed that lumen flow severely underestimates m-VIF but not ph-VIF.
• In vivo, peak m-VIF concentration was significantly lower than ph-VIF (p < 0.001).
• Quantitative model parameters (K(trans), vp) derived from m-VIF and ph-VIF were moderately to strongly correlated.

Conclusions:

• Local blood velocity significantly influences m-VIF, causing underestimation of contrast agent concentration.
• ph-VIF is recommended for accurate DCE-MRI analysis of carotid plaques.