A robust adiabatic constant amplitude spin-lock preparation module for myocardial T_1ρ quantification at 3 T

Area of Science:

• Cardiovascular Magnetic Resonance Imaging
• Quantitative MRI
• Biomedical Engineering

Background:

• T1ρ quantification offers a contrast-agent-free method for assessing myocardial fibrosis.
• Conventional spin-lock (SL) preparations are susceptible to B1 and B0 field inhomogeneities, causing artifacts in cardiac imaging at 3T.
• Severe banding artifacts limit the diagnostic accuracy of T1ρ mapping in the heart.

Purpose of the Study:

• To develop a robust spin-lock (SL) preparation module for myocardial T1ρ quantification at 3T.
• To mitigate banding artifacts caused by magnetic field inhomogeneities.
• To improve the accuracy and reliability of T1ρ mapping in cardiac applications.

Main Methods:

• Designed a novel spin-lock preparation module using the tan/tanh pulse (tan/tanh-SL).
• Optimized pulse shape parameters via Bloch simulations for pulse durations of 8, 4, and 2 ms.
• Evaluated the tan/tanh-SL module in phantom studies and in vivo cardiac T1ρ quantification on a 3T scanner, comparing it with composite SL and hyperbolic secant SL (HS-SL) pulses.

Main Results:

• Bloch simulations yielded feasible pulse shape parameters for the tan/tanh-SL module.
• The tan/tanh-SL module demonstrated reduced quantification errors compared to HS-SL (27.7% for 8 ms, 75.6% for 4 ms).
• Phantom studies showed lower sensitivity to B0 and B1 inhomogeneities for tan/tanh-SL compared to composite SL and HS-SL pulses.
• In vivo cardiac T1ρ maps exhibited fewer banding artifacts with tan/tanh-SL.

Conclusions:

• The proposed tan/tanh-SL preparation module significantly enhances robustness against B0 and B1 field inhomogeneities.
• This novel module effectively reduces banding artifacts in cardiac T1ρ quantification at 3T.
• The tan/tanh-SL method provides a more reliable approach for contrast-agent-free myocardial fibrosis assessment.