Characterization of imaging latency for real-time MRI-guided radiotherapy

Area of Science:

• Medical Physics
• Radiotherapy Technology
• Magnetic Resonance Imaging

Background:

• Hybrid MR-linac systems enable real-time tumor tracking and adaptive radiotherapy through fast dynamic MRI.
• Minimizing imaging latency is crucial for effective real-time treatment adaptation.

Purpose of the Study:

• To investigate the influence of different acquisition parameters on imaging latency in hybrid MR-linac systems.
• To evaluate methods for reducing imaging latency in dynamic MRI for adaptive radiotherapy.

Main Methods:

• Measured imaging latency for Cartesian readouts with linear, reverse-linear, and high-low phase encode orderings.
• Measured imaging latency for radial readouts with linear and golden angle profile orderings.
• Implemented a spatio-temporal (k-t) filter for the golden angle radial sequence to reduce latency.

Main Results:

• Cartesian readouts with high-low ordering achieved three times lower latency than linear ordering.
• The k-t filter reduced radial acquisition latency from 50% to 25% of the acquisition time.
• The implemented filter did not negatively impact signal-to-noise ratio or artifact power.

Conclusions:

• Acquisition parameter optimization, specifically high-low ordering for Cartesian and k-t filtering for radial sequences, significantly reduces imaging latency.
• Reduced imaging latency in dynamic MRI is achievable without compromising image quality.
• These findings support the advancement of real-time adaptive radiotherapy using hybrid MR-linac systems.