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1. (GB2234594) Nuclear magnetic resonance imaging methods
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- 7 CLAIM
1. A method of obtaining NMR imaging information from a solid object comprising subjecting the object to a static magnetic field, applying a gradient magnetic field which varies sinusoidally in amplitude about a zero value, applying a repetitive sequence of radio frequency pulses at instants around the zero value of the said gradient field each of such frequency, magnitude and duration and successive pulses of the sequence being of such relative rf phase, that selected nuclei in the object precess with accumulated phase in each sequence, and measuring the resulting NMR signal from the object.
2. The method as claimed in Claim I in which the sequence of radio frequency pulses is such that the pulses of the sequence are separated by constant interpulse window lengths equal to half the magnetic gradient field cycle time.
3. The method as claimed in either one of the preceding claims in which a sinusoidal offset magnetic field of spatially uniform amplitude is superimposed on the sinusoidally time-varying gradient magnetic field to shift spikes in the measured signal after Fourier transformation caused by rf phase errors away from areas of interest.
4. The method as claimed in any one of the preceding claims in which an initial radio frequency preparation pulse is applied before the repetitive sequence of radio frequency pulses.
5. The method as claimed in Claim 4 in which the preparation pulse and the sequence of pulses each comprise 900 rf pulses, the rf phases of which are in relative phase quadrature with each other and according to the following pattern 90-y-"-(90-x-"-90-y-'c-90-x-'c-90-x-'c-90-y-1-90-x-7-)n where -y and -x indicate rf relative phase quadrature, -c is a predetermined time interval and n is an integer equal to the number of repetitions of the sequence.
6. The method as claimed in any one of the preceding claims in which the measuring of the resultant nmr signal from the object takes place in the time interval between the preparation pulse and the sequence of pulses and between the last two pulses of a repeated sequence.
1 C 7. The method as claimed in any one of the preceding claims which is repeated with different directions of gradient magnetic field relative to the sample.
8. The method as claimed in Claim 7in which the direction of a 05 gradient magnetic field is determined by applying two sinusoidally varying electric currents of predetermined ratio to two magnetic coils positioned in relative quadrature to each other.
9. A method of obtaining NMR imaging information from a solid 10 object substantially as described herein with reference to the accompanying drawings.
UK 5/90 1 Published 1991 at The Patent Office, State House. 66/71 High Holborn. IA)ndonWCIR4TP. Further copies Tnay be obtained from Sales Branch. Unit 6. Nine Mile Point, C%nnfelinfach, Cross Keys. Newport. NPI 7HZ- Printed by Multiplex techniques'ltd. St Mary Cray. Kent