Electricity: measuring and testing – Particle precession resonance – Using a nuclear resonance spectrometer system
Patent
1993-08-19
1995-11-21
Arana, Louis M.
Electricity: measuring and testing
Particle precession resonance
Using a nuclear resonance spectrometer system
324307, G01V 300
Patent
active
054690609
ABSTRACT:
A method and apparatus for time encoded magnetic resonance imaging is presented. In accordance with the present invention, a static magnetic field oriented in a first direction is generated, with the sample to be imaged disposed within this static magnetic field, whereby the magnetization vector created by atomic particles is constant in size and direction as a result of the static magnetic field. The sample is then exposed to a first linear magnetic field gradient oriented in a second direction to define a slice. The sample is then excited with a radio frequency (RF) pulse, at the resonance frequency, the pulse being oriented in a third direction perpendicular to the first direction. This causes the magnetization vector of the atomic particles to rotate 90.degree. into a plane perpendicular to the first direction. The sample is then exposed to a two dimensional, non-uniform, magnetic field gradient oriented in a plane perpendicular to the first direction. The sample is then exposed to a second uniform magnetic field gradient oriented in a fourth direction perpendicular to the second direction. A spin echo is produced by pulse or gradient reversal then the RF signals are detected. RF signals are emitted as a result of the spin echo, these RF signals vary in time as a result of the exposure to the two dimensional, non-uniform, gradient magnetic field. This time variance is indicative of spacial position within the slice. The RF signals received as a function of time are converted to a set of frequency domain functions at specific times relating to specific strips in the image by, for example, Short Time Fourier Transformer (STFT). These frequency domain functions in the form of strips, are combined sequentially to form the entire time-frequency domain function or the image.
REFERENCES:
patent: 5122748 (1992-06-01), Oh et al.
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