US 4,901,020 AGranted

Pulse sequence for operating a nuclear magnetic resonance tomography apparatus for producing images with different T.sub.2 contrast

AssigneeSiemens Aktiengesellschaft

InventorsRalf Ladebeck, Hubertus Fischer, Franz Schmitt

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Abstract

A pulse sequence is disclosed for operating a nuclear magnetic resonance tomography apparatus for producing images having different T.sub.2 contrast. A signal for the gradient-echo imaging is first acquired after excitation of the nuclei subsequently, the magnetization, which is already prepared for imaging, is refocused by a 180.degree. radio-frequency pulse, and a second echo is measured in the presence of a readout gradient. Independent images having different T.sub.2 contrast can be reconstructed with the gradient echo and with the spin echo. It is thus possible to simultaneously measure a gradient echo image having a significantly lower T.sub.2 contrast during the measuring time for a spin echo image.

Claims12

Dependent claims

A method for generating a pulse sequence for operating a nuclear magnetic resonance tomography apparatus for producing separate images having respectively different T.sub.2 contrast comprising the steps of:

(a) generating a first, selective radio-frequency pulse simultaneously with a gradient in the z-direction as a slice selection gradient;
(b) generating a gradient in the y-direction with a directional sign for dephasing spins in the y-direction simultaneously with a gradient in the x-direction for phase coding spins in the x-direction, said gradient in the x-direction having characteristics from which an amplitude-time integral associated with said gradient in the x-direction can be calculated;
(c) reversing the directional sign of said gradient in the y-direction thereby generating a first radio signal, and reading out said radio signal;
(d) generating a second radio-frequency pulse with a flip angle of approximately 180.degree.;
(e) generating another gradient in the y-direction having the same operational sign as in step (c) thereby generating a second radio signal, and reading-out said second radio signal;
(f) executing steps (a) through (e) a plurality of times and varying said characteristics of said gradient in said x-direction from execution-to-execution so that said amplitude-time integral varies from execution-to-execution, said plurality of said executions resulting in a data set of said first radio signals and a data set of said second radio signals;
(g) constructing a first image having a T.sub.2 contrast from said data set of said first radio signals;
and
(h) constructing a second image having a T.sub.2 contrast differing from the T.sub.2 contrast of said first image from said data set of said second radio signals,
said x-, y- and z-directions being orthogonal.

7 more elements

A method for generating a pulse sequence for operating and NMR tomography apparatus for producing separate images having respectively different T.sub.2 contrast comprising the steps of:

(a) generating a first, selective radio-frequency pulse simultaneously with a gradient in the z-direction as slice selection gradient, said gradient in the z-direction having a directional sign;
(b) reversing the directional sign of said gradient in the z-direction for rephasing spins in the z-direction, and simultaneously generating a gradient in the x-direction for pre-phasing spins in the x-direction;
(c) generating a gradient in the y-direction having a directional sign and multiply reversing said directional sign of said gradient in the y-direction thereby generating a first radio-frequency signal at each directional sign reversal, and reading-out the respective first radio-frequency signals after each directional sign reversal, and simultaneously generating a further gradient in the x-direction having characteristics from which an amplitude-time integral of said further gradient in the x-direction can be calculated and varying said characteristics from directional sign reversal-to-directional sign reversal of said gradient in the y-direction to increase said amplitude-time integral from directional sign reversal-to-directional sign reversal;
(d) generating a second radio-frequency pulse with a flip angle of approximately 180.degree.;
(e) generating a further gradient in the y-direction thereby generating a second radio-frequency signal, and reading out said second radio-frequency signal;
(f) using said first radio signals to generate a first image having a T.sub.2 contrast;
and
(g) using said second radio-frequency signal to generate a second image having a T.sub.2 contrast different from said T.sub.2 contrast of said first image,
said x-, y- and z-directions being orthogonal.

6 more elements

Dependencies are inferred from the claim text.