MRI gradient drive current control using all digital controller
AssigneeThe Regents of the University of California
InventorLawrence E. Crooks
Life of this patent
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Abstract
An all digital controlled current driver is used for each pulsed electromagnet (e.g., gradient coils) in a magnetic resonance imaging (MRI) system. Such an all digital current controller may be advantageously employed in either closed loop or open loop gradient coil control circuits. The elimination of analog components decreases cost, increases operating efficiency and improves operating characteristics of the MRI system.
Claims19
In a magnetic resonance imaging system which generates a control signal representing a desired level of electromagnet coil current to be supplied from a switchable electrical power supply via a filter, a method comprising the steps of:
- digitally generating said control signal to have a ratio of first digit values to second digit values that corresponds to the desired level of electromagnet coil current;
- and
- using said control signal to control the switched duty cycle of said electrical power supply.
In a magnetic resonance imaging system which generates a multi-bit digital control signal representing drive current to be attained in an electromagnet coil, the improvement comprising:
- a controlled electrical power supply including a switched drive power source directly connected to multi-bit digital signal processing circuits which directly switch said switched electrical drive power source with digital signals generated by digital signal processing of said digital control signal thus directly controlling the instantaneous duty cycle of electrical power supplied to said electromagnet coil via a smoothing filter.
In a magnetic resonance imaging system having a main magnet producing a static field B.sub.o and at least one electromagnet coil for superimposing a magnetic field onto said static field in response to a supplied flux demand signal, an improvement comprising:
- sense means for sensing the coil drive current or magnetic flux produced thereby and for producing an analog sense signal corresponding thereto;
- an analog to digital converter connected to convert said analog sense signal to a corresponding digital sense signal;
- a digital signal processor connected to receive said digital sense signal and a digital flux demand signal, to compare said received signals and to generate a digital on/off output signal representing the instantaneous duty cycle of electrical power to be supplied via a filter to said electromagnet coil to generate a gradient flux corresponding to said flux demand;
- and
- a switchable electrical power source connected to be switched responsive to said digital on/off output signal suppling electrical current via said filter to said electromagnet coil.
In a magnetic resonance imaging system having a main magnet producing a static field B.sub.o and at least one electromagnet coil for superimposing a magnetic field onto said static field in response to a supplied flux demand signal, an improvement comprising:
- a digital signal processor connected to receive a digital flux demand signal together with digital signals characterizing the magnetic field generating portions of the magnetic resonance imaging system and to generate a digital on/off output signal representing the instantaneous duty cycle of current to be supplied via a filter to said electromagnet coil to generate a magnetic field flux corresponding to said flux demand;
- and
- a switchable electrical power source connected to be switched responsive to said digital on/off output signal into and out of a filter circuit supplying electrical power to said coil.
Dependencies are inferred from the claim text.