| 摘要 |
FIELD: physics.SUBSTANCE: coil elements (18) generate a Bexcitation field in an examination region (14), wherein said Bexcitation field is distorted by patient loading (e.g., wavelength effects). Passive shimming elements (22, 24) are placed between the coil elements and the subject in order to improve the Bfield uniformity. In one embodiment, passive shimming elements include one or more dielectric rods (55) placed below the subject which generate no substantial MR proton signal and which have a permittivity of at least 100 and preferably greater than 500. In another embodiment, tubes (24) adjacent to each coil element are supplied with a dielectric liquid, wherein the thickness of the dielectric liquid between the coil element and the subject adjusts the phase of the Bfield generated by the coil element. Active Bshimming may be combined with passive shimming elements (22, 24) to achieve an improved RF field homogeneity result.EFFECT: improving homogeneity of exciting the Bexcitation field, improving the MR imaging operating process at high field intensity and improved signal-to-noise ratio.15 cl, 14 dwg |
