Digital combination and correction of quadrature magnetic resonance receiver coils

In a magnetic resonance system in which a subject is disposed in a temporally constant magnetic field and magnetic resonance signals from the subject are received by a quadrature coil assembly including first and second coils which lack a true quadrature relationship over their mutual field of view, the improvement comprising:

• a transforming means for transforming the resonance signals received by the first coil into a first complex domain image including a first array of vector values each having a magnitude and a direction and for transforming resonance signals received by the second coil into a second complex image including a second array of vector values each having a magnitude and a direction;
• a normalizing means for normalizing at least one of the magnitude and the direction of corresponding vector values of the first and second complex domain images;
• an image adder for combining corresponding vector values of the first and second complex domain images;
• and,
• a display means for converting magnitudes of the combined vector values of the combined first and second complex domain images into a human-readable magnitude display.

A magnetic resonance imaging apparatus comprising:

• magnets for generating a temporally constant magnetic field through an examination region;
• gradient coils and current amplifiers for generating magnetic field gradient pulses across the examination region;
• a quadrature radio frequency coil assembly for receiving magnetic resonance signals from the examination region, the quadrature coil assembly including a first coil and a second coil which have variations in the relative phase angle and signal strength of signals received from various points within the examination region;
• a pair of receivers each connected with one of the first and second coils for demodulating radio frequency magnetic resonance signals therefrom and analog-to-digital converters for digitizing the demodulated magnetic resonance signals into raw, complex data signals;
• array processors for separately inversely Fourier transforming the raw data signals from the first and second coils into first and second complex images, each complex image including an array of data values;
• a phase correction means for adjusting a phase angle of individual data values of the first and second complex images such that corresponding data values in both complex images have a common phase angle;
• an adder for adding the corresponding data values of the phase angle adjusted complex images to form a combined image;
• an image memory for storing a magnitude image derived from the combined complex image;
• a monitor for converting the magnitude image into a human-readable display.

A magnetic resonance imaging method comprising:

• generating a temporally constant magnetic field through an examination region;
• generating magnetic field gradient pulses across the examination region;
• receiving magnetic resonance signals from the examination region with a first coil and a second coil which have variations in the relative phase angle and signal strength of signals received from various points within the examination region;
• demodulating and digitizing radio frequency magnetic resonance signals received by the first and second coils to generate first and second raw, complex data signals;
• separately inversely Fourier transforming the first and second raw data signals into first and second complex images, each complex image including an array of data values, each data value having a phase angle value and a magnitude;
• adjusting at least one of the phase angle value and the magnitude of each pair of corresponding data values of the first and second complex images such that each pair of corresponding data values has at least one of a normalized phase angle and magnitude;
• adding the first and second complex images;
• converting the added images into a human-readable display.