Butts R K, Farzaneh F, Riederer S J, Rydberg J N, Grimm R C
Magnetic Resonance Laboratory, Mayo Clinic, Rochester, MN 55905.
Radiology. 1991 Aug;180(2):551-6. doi: 10.1148/radiology.180.2.2068326.
Use of intraacquisition modification of pulse-sequence parameters to reduce acquisition time for conventional T2-weighted spin-echo images was evaluated. With this technique (variable-rate spin-echo pulse sequence), the repetition time and echo time (TR msec/TE msec) were reduced during imaging as a function of the phase-encoding view. To maintain T2-based contrast, TR and TE for the low-spatial-frequency views were left at their prescribed values (eg, 2,000/80). TR and TE for the high-spatial-frequency views were progressively reduced during imaging (eg, to 1,000/20). Acquisition time was reduced by as much as 25%. In one pulse sequence, the duration of multisection imaging nominally performed at TR 2,000 and with 256 phase-encoding views was reduced from 9 minutes 30 seconds to 6 minutes 30 seconds. In all sequences, edges and small structures were enhanced, and T2 contrast was somewhat decreased in high spatial frequencies. Filtering of the raw data before reconstruction can suppress these effects and provide a net increase in contrast-to-noise ratio.
评估了使用采集期间脉冲序列参数的修改来减少传统T2加权自旋回波图像的采集时间。采用这种技术（可变速率自旋回波脉冲序列），成像过程中重复时间和回波时间（TR毫秒/TE毫秒）作为相位编码视图的函数而缩短。为维持基于T2的对比度，低空间频率视图的TR和TE保持在规定值（例如，2000/80）。成像过程中高空间频率视图的TR和TE逐渐降低（例如，降至1000/20）。采集时间减少了多达25%。在一个脉冲序列中，名义上在TR 2000和256个相位编码视图下进行的多层面成像持续时间从9分30秒减少至6分30秒。在所有序列中，边缘和小结构得到增强，并且高空间频率下的T2对比度有所降低。重建前对原始数据进行滤波可抑制这些影响并使对比度噪声比净增加。
