Respiration artifact correction in three-dimensional proton resonance frequency MR thermometry using phase navigators

Area of Science:

• Magnetic Resonance Imaging
• Biomedical Engineering
• Medical Physics

Background:

• Accurate real-time temperature monitoring is crucial for effective thermal therapy.
• Respiration-induced B0 field variations can degrade the accuracy of 3D echo planar imaging (EPI) temperature measurements.
• Proton resonance frequency (PRF) thermometry is a key technique for monitoring temperature during treatments.

Purpose of the Study:

• To develop a reliable method for 3D segmented EPI (seg-EPI) PRF temperature monitoring.
• To mitigate the impact of respiration-induced B0 field variations on temperature accuracy.
• To enhance the precision of temperature monitoring during MR-guided focused ultrasound (MRgFUS) treatments.

Main Methods:

• Incorporated a free induction decay (FID) phase navigator into a 3D seg-EPI sequence.
• Monitored B0 field variations before and after EPI readout.
• Applied k-space phase correction to remove respiratory-induced off-resonance effects.
• Evaluated the technique in phantoms with simulated breathing and in vivo human breasts.

Main Results:

• K-space phase correction improved the standard deviation of magnitude images by an average factor of 1.5.
• PRF temperature measurements in volunteer breasts showed an average improvement factor of 2.1.
• Demonstrated enhanced accuracy of temperature estimates during MRgFUS heating in phantoms.

Conclusions:

• Phase correction using FID navigators effectively addresses field variations caused by respiration.
• This technique shows promise for robust 3D temperature monitoring in thermal therapy.
• Enables more reliable real-time feedback for MR-guided thermal treatments.