Cardiorespiratory motion-tracking via self-refocused rosette navigators.

Area of Science:

• Medical Imaging
• Biomedical Engineering
• Physics

Background:

• Accurate tracking of cardiorespiratory motion is crucial for high-quality MR and PET-MR imaging.
• Existing methods often require additional hardware or significant sequence modifications.

Purpose of the Study:

• To develop a flexible, hardware-independent method for tracking respiratory and cardiac motion during MR and PET-MR body examinations.
• To minimize sequence modification requirements for motion tracking integration.

Main Methods:

• A contrast-neutral rosette navigator module was incorporated post-RF excitation.
• Spatial encoding gradients were applied to the Free Induction Decay (FID) signal.
• Blind source separation techniques were used to extract motion signals.
• Validation was performed using a PET-MR-compatible motion phantom and 13 human subjects.

Main Results:

• Reliable extraction of both respiratory and cardiac motion from phantom and patient studies.
• MR-derived motion signals in phantom studies were validated against ground truth measurements (diaphragm displacement, left ventricle triggering pulse).

Conclusions:

• The proposed method provides accurate respiratory and cardiac motion tracking.
• The navigator module is short (1.76 ms), self-refocusing, and minimally impacts sequence design.