Sensitivity of Transmit Coil B1+ to Lung Inflation in Hyperpolarised 3He MRI

Jim M. Wild¹, Martin H. Deppe¹, Salma Ajraoui¹, Helen Marshall¹, Graham Norquay¹, Titus Lanz², Matthias Behr², Francesco Padormo³, Juan Parra-Robles¹, Sebastian Kozerke⁴

Hyperpolarised gas MRI is highly sensitive to RF flip angle (FA) and B1+ homogeneity, thus accurate knowledge of the delivered flip angle and a spatially homogeneous B1+ field are both highly desirable. Chest birdcage coils have been developed for both 3He and 129Xe lung MRI at 1.5T providing homogenous B1+ fields over the lung FOV. In 1H multi-transmit coil imaging of the abdomen at 3T, modulation of the delivered B1+ has been reported as a function of breathing cycle. In this work the effect of lung inflation upon the B1+ field delivered by two 3He chest birdcage coils was investigated at 1.5T and 3T.