Retrospective phase-based gating for cardiac proton spectroscopy with fixed scan time

Area of Science:

• Cardiovascular Magnetic Resonance Imaging
• MR Spectroscopy Techniques
• Medical Imaging Physics

Background:

• Respiratory motion significantly degrades the quality and duration of in vivo cardiac proton MR spectroscopy.
• Prospective navigator gating is commonly used to mitigate respiratory motion but results in unpredictable, subject-dependent scan times.

Purpose of the Study:

• To implement cardiac proton MR spectroscopy (MRS) with a fixed scan duration using retrospective phase-based gating.
• To compare the novel retrospective gating method against conventional prospective navigator-gated MRS.

Main Methods:

• Eighteen healthy volunteers underwent cardiac proton MRS at 1.5T using both prospective navigator-gating and navigator-free retrospective phase-based gating with fixed scan times.
• Retrospective gating utilized a threshold based on the standard deviation of water and triglyceride phases for motion compensation.
• Scan time, gating efficiency, and reproducibility of triglyceride-to-water ratios were assessed.

Main Results:

• Prospective navigator-gated scans had variable durations (mean 10:05 min, efficiency 40.4%), while retrospective gating achieved a fixed 11:44 min scan time.
• Retrospective phase-based gating demonstrated a higher gating efficiency (72.7%) and a coefficient of variation (CoV) of 9.8% for triglyceride-to-water ratios, comparable to the navigated reference.
• Intrasubject reproducibility for retrospective gating showed a CoV of 9.5%.

Conclusions:

• Cardiac proton MRS with retrospective phase-based gating is feasible and offers reproducible triglyceride-to-water ratio measurements within a fixed scan time.
• This technique provides predictable exam durations, independent of respiratory motion, enhancing motion compensation strategies for cardiac proton MRS.