Method for detecting gradient magnetic field focus in magnetic resonance imaging system

The invention discloses a method for detecting a gradient magnetic field focus in a magnetic resonance imaging system. According to the method, the offset of the center of a gradient magnetic field in each direction is measured by utilizing the characteristic that the magnetic field intensity of the center of the gradient magnetic field is unchanged when positive and negative gradients are applied and combining the relationship between the magnetic field intensity and proton resonance frequency, so that whether three paths of gradient magnetic fields have a common center or not is judged, namely whether a gradient magnetic field focus exists or not is judged, and the position of the gradient magnetic field focus is determined. The detection method provided by the invention does not need an additional detection instrument, is simple in detection process and easy to implement, can measure the offset of the gradient magnetic field center in each direction, can provide a reference basis for correcting gradient co