[Evaluation of prototype for additional pad packing (polystyrene ball bullet) for homogenously fat suppressed magnetic resonance imaging].

Purpose: Homogeneity of static magnetic field (B(0)) is unstable for head and neck magnetic resonance (MR) examination; consequently, chemical shift selective fat suppression becomes inhomogeneous. There is a commercially available additional pad to attenuate the B(0) inhomogeneity, but it is expensive. It has been reported that uncooked rice can be used as a material in the pad, but it has hygienic and weight problems. We searched for a material which can replace the uncooked rice, and evaluated its performance.

Method: After filling various materials into the cylindrical phantom, each material was evaluated by image distortion of gradient filed echo and spin echo single-shot echo planar images. A prototype additional pad was made with a material which showed less image distortion in the phantom experiment and is easily available in clinical examination. For comparison, an uncooked rice pad with the same volume was also prepared. Fat suppressed head and neck magnetic resonance imaging (MRI) of normal volunteers were visually compared when the three additional pads, including the commercial product, were used or not.

Result: The polystyrene ball bullet (BB bullet) was adopted as a material for the additional pad. The improvement of the fat suppression in the head and neck MRI was almost the same between the three additional pads. BB bullet pad was the lightest.

Conclusion: BB bullet can be used as a material of additional pad attenuating the B(0) inhomogeneity instead of uncooked rice.