FAST SCAN RESEARCH

Fast scanning techniques under study in the MR Laboratory include single and multi-shot echo-planar imaging (EPI), gradient echo methods, and RARE fast-spin-echo techniques. Additionally, research is being done in the development of high speed reconstruction methods and interactive scanner control, or "MR Fluoroscopy." As these techniques are developed, they are applied in various ways clinically, including abdominal, cardiovascular, and neurologic imaging.

The purpose of this project is to develop a rapid, interactive method for providing images which have high spatial resolution and high immunity to inhomogeneity artifact in exchange for some reduction of the image formation rate into the range of 0.5 to 1.0 Hz. This is done by using single-shot fast spin-echo (SSFSE) methods. With this approach the effective time can be adjusted by variation of the phase encoding order, and echo times from 60 msec to 500 msec or more are permitted. The image generation rate can be controlled in two ways. In the first, the frame rate is fixed; selected by the operator at 1.0 Hz or slower.

The second approach uses "on demand" acquisition in which an image is acquired only when the operator specifies acquisition with a mouse click or when the plane of section is modified. This method allows fuller recovery of magnetization and thus higher SNR as well as a reduction in the number of unnecessary images than a fixed rate approach. With both techniques the operator can interactively adjust parameters such as the field of view and oblique angulation. The principal applications of this method thusfar have been for imaging of the pelvic floor and fetal imaging.

Reference: Busse RF, Riederer SJ, Fletcher JG, Bharucha AE, Brandt KR, "Interactive fast spin echo imaging." Magn Reson in Med 44:339-348 (2000).