Method for measurement of magnetic fields, method for production of gradient coils, gradient coil, and apparatus for magnetic resonance imaging

A method for measurement of magnetic fields comprising the steps of:

• arranging a magnetically resonant sample at a measuring point on the surface of an imaginary sphere in a measuring space;
• arranging another magnetically resonant sample at the center of said sphere;
• applying a gradient magnetic field to said measuring space;
• carrying out RF excitation after stopping the application of said gradient magnetic field to measure FID signals generated by said samples;
• calculating a magnetic field intensity at said measuring point on the basis of differences in differentials of the phases of FID signals generated by the samples at said measuring point and at the center of said sphere;
• and
• fitting said magnetic field intensity into a spheric surface function representing a magnetic field intensity distribution in said measuring space.

A method for measurement of magnetic fields comprising the steps of:

• arranging a magnetically resonant sample at a measuring point on the surface of an imaginary sphere in a measuring space;
• applying intermittently a gradient magnetic field while the gradient is successively varied from the maximum gradient in one polarity to the maximum gradient in the reverse polarity and then the gradient is successively varied from the maximum gradient in said reverse polarity to the maximum gradient in said first polarity;
• carrying out RF excitation during the intermittence of said gradient magnetic field to measure FID signals generated by said sample;
• calculating differentials of the phases of said FID signals;
• calculating a magnetic field intensity at said measuring point on the basis of the hysteresis of differences in said differentials accompanying the completion of said round of gradients;
• and
• fitting said magnetic field intensity into a spheric surface function representing a magnetic field intensity distribution in said measuring space.

A method for measurement of magnetic fields comprising the steps of:

• arranging a magnetically resonant sample at a measuring point on the surface of an imaginary sphere in a measuring space;
• arranging another magnetically resonant sample at the center of said sphere;
• applying intermittently a gradient magnetic field while the gradient is successively varied from the maximum gradient in one polarity to the maximum gradient in the reverse polarity and then the gradient is successively varied from the maximum gradient in said reverse polarity to the maximum gradient in said first polarity;
• carrying out RF excitation during the intermittence of said gradient magnetic field to measure FID signals generated by said samples;
• calculating differences in differentials of the phases of FID signals generated by the samples at said measuring point and at the center of said sphere;
• calculating a magnetic field intensity at said measuring point on the basis of the hysteresis of the differences in said differentials accompanying the completion of said round of gradients;
• and
• fitting said magnetic field intensity into a spheric surface function representing a magnetic field intensity distribution in said measuring space.