Experimental study of fast and ultrafast T2-weighted imaging sequences using AMI-25 superparamagnetic iron oxide (SPIO)

The objective of this study was to evaluate fast and ultrafast T2-weighted images (T2WI), including echo planar imaging (EPI), using an AMI-25 agar ph antom. Image quality for conventional spin echo (CSE) and turbo spin echo ( TSE) was almost equivalent. In high-resolution TSE, image quality was highe st due to the use of a 512 x 256 matrix. Half-Fourier single-shot turbo SE (HASTE) was associated with blurring of images, and turbo-gradient SE (TGSE ) showed a deterioration of image quality. EPI also suffered from poor imag e quality because this method is very sensitive to magnetic [field inhomoge neity. CSE showed good signal-to-noise ratio (S/N) and contrast ratio (CR), but also required the longest imaging times. Among the TSE sequences, TSE with a short echo train length (ETL) was superior in terms of S/N, The CR o f EPI and fast low angle shot (FLASH) images were improved in proportion to the effective echo time (TE). At present, TSE is inferior to CSE in terms of S/N and CR. However, taking into consideration scanning time, TSE with a short ETL is thought to be suitable for routine examinations. Effective TE is an important factor in gradient echo (GRE) examinations.