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Proceedings Paper

Faster MR Imaging Methods
Author(s): Paul Margosian; Franz Schmitt
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Paper Abstract

Two different types of methods for acquiring MR data more quickly have been explored here. The first set of methods uses half the normal number of measurements and is capable of shortening acquisition times by a factor of two. The second type of method uses measurements from multiple echoes to synthesize a 'conventional' spin-warp raw data set. This second method is capable of shortening data acquisition times by factors of four to eight. Three types of 'half the data' methods have been tested. The first uses the central half of the phase encoding steps, and reconstructs on the usual 256 x 256 matrix using a sinc interpolation; with this first method, signal to noise ratio is improved, but spatial resolution in the phase encoding direction is reduced. The second method uses all the upper (or lower) half of the normal phase encoding steps, places them in an otherwise empty 256 x 256 matrix, reconstructs, makes a phase correction, takes the real part. This 'half Fourier' method uses the phase information to retain full resolution with only half the data (really 53%) but at the cost of a reduction of signal to noise ratio. for the third method, every second phase encoding measurement is taken, along with eight extras in the center of the data space, empty data lines are filled by cubic interpolation, and a FFT recontruction is done. For this method, spatial resolution and signal to noise ratio are maintained, but two 'ghost' images (low amplitude-occur because of the inherent undersampling of this method. The 'multiple echo' method for faster data acquisition makes use of a sequence that acquires different phase encoding steps in the data from different echoes. the best strategy is to take the central (low frequency) measurements from the lowest numbered echoes, and the higher frequency measurements from the later echoes. The practical details of this method include correcting position, phase, and amplitude of measurements from different echoes. It is also important to use data acquisition sequences that are very well adjusted refered to stimulated echoes and eddy currents. The result is that data can be acquired four to eight times faster than normal for spin-warp imaging, almost full resolution is retained, and signal to noise ratio is reduced somewhat.

Paper Details

Date Published: 5 May 1986
PDF: 8 pages
Proc. SPIE 0593, Medical Image Processing, (5 May 1986); doi: 10.1117/12.952139
Show Author Affiliations
Paul Margosian, Siemens AG UB Med (West Germany)
Franz Schmitt, Siemens AG UB Med (West Germany)

Published in SPIE Proceedings Vol. 0593:
Medical Image Processing
Paul Suetens; Ian T. Young, Editor(s)

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