Delay based active noise cancellation for magnetic resonance imaging
AssigneeThe United States of America as represented by the Secretary of the Air Force
InventorDouglas S. Brungart
Life of this patent
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Abstract
System and method for actively canceling the acoustic noise generated by changes in the electric current within the gradient coils of a magnetic resonance imager based on the finding that the acoustic noise in the magnetic resonance imager is highly periodic but that the period of the magnetic resonance imager noise changes substantially during a scan. The acoustic noise signal is measured at the ears of a patient undergoing a magnetic resonance imaging, delayed by a variable number of samples and the resulting signal is subtracted from the acoustic noise signal. Magnetic resonance imaging noise cancellation occurs at the level of 20 decibels or more.
Claims18
An improved patient comfort, magnetic resonance imaging noise cancellation system comprising:
- a magnetic resonance imaging system,
- a patient mounted pneumatic headset system;
- an error microphone connected to said patient mounted pneumatic headset measuring an acoustic noise signal at an ear of said patient;
- and
- a noise cancellation processor producing an acoustic noise signal canceling waveform, said acoustic noise signal canceling waveform being a delayed and inverted acoustic noise signal output from said error microphone.
An improved patient comfort, delay based active noise cancellation method for magnetic resonance imaging comprising the steps of:
- measuring an acoustic noise signal at an ear of said patient undergoing magnetic resonance imaging;
- selecting three delay values representing a repetition of said acoustic noise signal using an auto-correlation algorithm;
- comparing an acoustic noise signal with each of said three delay values from said selecting step with said acoustic noise signal and selecting a delay that produces a most effective noise cancellation waveform;
- inverting said noise cancellation waveform selected in said comparing step;
- and
- communicating said noise cancellation waveform from said inverting step to said patient using pneumatic headphones thereby canceling the acoustic noise signal received by said patient.
Dependencies are inferred from the claim text.