th  - 1987 - 51st ENC Conference

WF76
RAPID ~ F R A M E IMAGING
Kenneth R. Metz* and John P. Boehmer
Department of Radiology
The Pennsylvania State University College of Medicine
~he M. S. Hershey Medical Center
P. O. Box 850
Hershey, Pennsylvania 17033
Since its introduction [Hcult, J~R, 33, 183 (1979)], rotating-frame
imging (RFI) has excited growing interest. This technique employs
radiofrequency field (B I) gradients to produce a spatial (x) dependence
of the NMR nutation frequency: Fl(x) = ~Bl(X)/2~. Ordinarily, a one-
dimensional spat/al image is formed using a t%D-dimensional pulse
sequence of the genen~l type:
(Preparation - n-P - FID Acquisition - Relaxation Delay) n [RFI]
where the rf pulse width n-P increases with the number of stored FID's.
2DPT processing with respect to the pulse width (t I) and acquisition time
(t 2) yields a 2D frequency-dum~in map correlating the NMR spectrum along
the F 2 axis with the spatial position along the F 1 axis.
In many cases, the obserut~ chemical species (e.g., IH20 or 23Na+)
may exhibit only a single spectral line. ~his allows the rotating-frame
imge to be formed using the sequence:
Preparation - (P - Acquire One Point) n - Relaxation Delay [Rapid RFI]
where n s~ssi~ individual points are acquired between pulses (P) in a
long train. The rapid RFI method uses only a small fraction of the rf
power normally required, provides, good spatial resolution, and is
extremely fast, as shown by the I~ image below for a three-c/hamber
phantcm acquired in 41 ms.
l ' ' ' i ' ' ' I ' '
6000 4000 2000 Hz