Respiratory and cardiac motion induced B0 fluctuations in the breast: implications for PRFS-based temperature monitoring
Peters N, Bartels L, Lalezari F, Vincken K, Verwoerd J, Mali W, Bakker C
University Medical Center Utrecht
Proton resonance frequency shift based temperature mapping in the breast is hindered by local magnetic field inhomogeneities. We postulate a method for measuring field disturbances in the breast due to respiration and cardiac motion and describe the implications for PRFS-based thermometry. Field disturbances due to regular respiration were approximately 0.15 ppm (+/- 15C), due to maximum capacity respiration 0.25 ppm (+/- 25C), and less than 0.03 ppm (+/- 3C) due to cardiac motion. We concluded that respiration-induced field disturbances cause significant phase shifts in the breasts that need correction for accurate thermometry during MR-guided focused ultrasound.