Importance

Loading Importance Indicators...

Abstract

A method of NMR spectroscopy or tomography, wherein a sequence of temporarily offset radio frequency pulses is applied onto a spin ensemble, is characterized in that after a sequence of pulses with flip angles .alpha..sub.1 . . . .alpha..sub.n (with .alpha..sub.1 . . . .alpha..sub.n.gtoreq.0.degree.) and phases .phi..sub.1 . . . .phi..sub.n between which spins are dephased by .phi..sub.1 . . . .phi..sub.n, a central refocusing pulse is applied as (n+1)th pulse, followed by a pulse sequence which is mirror-symmetrical to the central refocusing pulse, wherein the flip angles .alpha..sub.n+2 . . . .alpha..sub.2n+1 and phases .phi..sub.n+2 . . . .phi..sub.2n+1 of the pulses have, in comparison with the mirror-symmetrical pulses with .alpha..sub.n . . . .alpha..sub.1 and .phi..sub.n . . . .phi..sub.1, negative sign with respect to amplitude and phase and the dephasings .phi..sub.n+2 . . . .phi..sub.2n+1 which are also mirror-symmetrical to the central refocusing pulse in the sequence are equal to the respective mirror-symmetrical dephasings .phi..sub.n . . . .phi..sub.1 such that at the end of the pulse sequence, an output magnetization M.sub.A (Mx,My,Mz) of the spin ensemble is refocused with respect to the central refocusing pulse through application of rotation corresponding to the symmetrical relation M.sub.R (-Mx,My,-Mz)=Rot.sub.y (180.degree.)*M.sub.A (Mx,My,Mz) into a final magnetization M.sub.R =(-Mx,My,-Mz) (=hyperecho formation). In this fashion, even after application of refocusing pulses of any flip angles, the occurring signal losses can be cancelled and the complete signal amplitude can be regained with respect to dephasing through chemical shift, susceptibility and field inhomogeneity.

Loading the Abstract Image...

First Claim