Repeatability of Open-MOLLI: An open-source inversion recovery myocardial T1 mapping sequence for fast prototyping

Area of Science:

• Cardiovascular Magnetic Resonance Imaging
• Medical Physics
• Open-Source Software Development

Background:

• Cardiac T1 mapping is crucial for assessing myocardial tissue characteristics.
• Current methods can be limited by accessibility and proprietary software.
• Developing open-source tools enhances research flexibility and collaboration.

Purpose of the Study:

• To create an open-source prototype for myocardial T1 mapping, named Open-MOLLI.
• To evaluate the repeatability and performance of Open-MOLLI.
• To improve accessibility for cardiac T1 mapping research and development.

Main Methods:

• Developed Open-MOLLI, an inversion-recovery sequence with a balanced SSFP readout, based on the MOLLI sequence in Pulseq.
• Acquired data using Open-MOLLI and MOLLI sequences in an ISMRM/NIST phantom and 21 healthy volunteers.
• Conducted test-retest studies in 18 volunteers to assess repeatability.

Main Results:

• Phantom T1 values were comparable between Open-MOLLI and MOLLI, particularly for values near healthy myocardium.
• In vivo T1 estimates showed similar mean values between Open-MOLLI (998 ± 52 ms) and MOLLI (1004 ± 33 ms).
• Open-MOLLI exhibited slightly higher repeatability coefficients (4.4%) compared to MOLLI (3.0%), despite noisier images.

Conclusions:

• The open-source Open-MOLLI sequence is viable for in vivo cardiac T1 mapping, yielding similar T1 values to the established MOLLI method.
• Open-MOLLI enhances accessibility to cardiac T1 mapping techniques.
• It serves as a foundational sequence for implementing and testing future improvements and modifications.