Method for improving the signal-to-noise ratio in a nuclear magnetic resonance tomography apparatus

DETAILED DESCRIPTION We claim as our invention 1.
A method for improving the signal-to-noise ratio in a nuclear magnetic resonance tomography apparatus comprising the steps of: generating an RF excitation pulse for exciting nuclear spins in an examination subject; simultaneously generating a gradient magnetic field in a first direction thereby making said RF pulse slice-selective; generating a phase-coding magnetic field gradient in a second direction; generating a read-out magnetic field gradient pulse sequence alternating in polarity from pulse-to-pulse; acquiring, in the presence of said read-out gradient, nuclear magnetic resonance signal arising from said nuclear spins; phase-demodulating said nuclear magnetic resonance signal to obtain a real signal part and an imaginary signal part; subjecting said real and imaginary signal parts to respective bandpass filtration, said bandpass filtration having a bandwidth; digitizing said real and imaginary signal parts at a varying sampling rate; adapting said bandwidth to said sample rate by increasing said bandwidth as said sampling rate increases; entering the digitized values of said real and imaginary signal parts per read-out gradient pulse in respective rows of a raw data matrix; subjecting said raw data matrix to a two-dimensional Fourier transformation to obtain an image matrix; and producing a visual image of the selected slice of said subject from said image matrix.
2.
A method as claimed in claim 1 wherein the step of generating a read-out magnetic gradient field pulse sequence is further defined by generating a read-out magnetic field gradient pulse sequence having a sinusoidal chronological curve and wherein the step of subjecting said real and imaginary signal parts to respective bandpass filtration is further defined by subjecting said real and imaginary signal parts to respective bandpass filtration in respective bandpass filters each having a bandwidth .
DELTA.
f.
sub.
s having the following chronological curve: ##EQU6## wherein