| Popis: |
Both long examination times and long acquisition times have been considered significant disadvantages in the routine clinical application of MRI. Since 1985 several so-called fast-imaging pulse sequences have been developed. A number of these pulse sequences, like fast low-angle shot imaging (FLASH) and fast imaging with steady precession (FISP), are based on a steady state, using very short repetition times (TR), very short echo times (TE) produced by gradient echos, and variable flip angles (Oppelt et al. 1986; Weber et al. 1986; Frahm et al. 1986; Mills et al. 1987; Matthaei et al. 1986; Weber and Deimling 1987; Krestin et al. 1986). |
