MRI apparatus having a feed-forward loop, which is inserted in the loop gradient

摘要

(57) and generated by the control circuit in the MRI apparatus SUMMARY magnetic field gradient pulses, it is easy to generate the effects of interference in the control circuit, therefore, gradient current pulse is input in the (33) input of the control circuit is not formed exactly as specified by the signal. Can be reduced by feedback, this effect, but because of the dielectric element (3,51), a deviation of a few still remain and / or capacitive various in the control circuit. Because of limited bandwidth in the control circuit, these deviations, it is not possible to adequately compensate. In accordance with the present invention, the control circuit is provided (57) filter is the inverse of the impedance characteristics of the (3,51) component the filter characteristic leads to inclined feed-forward loop, including (61, 63). Case of providing no feedback loop in the control circuit, can be inserted in the signal path in the case of a digital embodiment, the A / D converter 41, the error signal e (t) becomes very small, the feed forward loop to delay the signal from (57), can also be inserted (35) delay member prior to the analog-to-digital converter. At this time, it is possible to be realized to have a small bit width, the analog-to-digital converter (41), as a result, the conversion rate reaches the value desired high.