Correction Accuracy in B1 measurement for high field Image Intensity Correction

H. Kabasawa, C. Guclu, Z. Li Applied Science Laboratory Japan, GE Yokogawa Medical Systems, Hino-shi, Tokyo, Japan, GE Healthcare-Technologies, 3200 Grandview Blvd, Waukesha, WI, United States [Introduction] MR imaging with phased array receive coils became available at 3T and higher field strengths. In lower field strength systems, uniformity correction methods using body coil image as homogeneous reference image are widely used, but this correction method does not perform well at high field because of dielectric effect. To correct for image non-uniformity caused by dielectric effect, in-vivo B1 mapping-based image correction methods were recently presented [1-2]. The B1 field or flip angle (FA) field map may be perturbed due to various reasons including susceptibility artifact, tissue relaxation parameters, etc.. To reduce the sensitivity to these measurement errors, a simulation analysis was performed to characterize noise variation in the B1 map. Then a novel B1 field estimation and filtering method was proposed based on the simulation results. [Materials and Methods] To measure the B1 field spatial distribution, calibration images with two different FAs (using FGRE) were acquired with body coil[3-4] and surface coil reference scan with same FA was acquired to measure coil receive sensitivity. When the FA of α degree and α/2 degree were used in the calibration scan, one can estimate FA spatial distribution from the following simple equation: