Even when a more homogeneous birdcage coil is used, the B1 field variation is nonnegligible (e.g., 10% or more), especially when the imaged object occupies a large portion of the coil volume.

• 就算使用均匀的鸟笼型线圈，B1 场的在不同部位的差异值也是不容忽视的（10%25或更多），特别是成像物体占据线圈体积的大部分的时候。