AUTOMATED NON-MAGNETIC MEDICAL MONITOR USING SHAPE MEMORY ACTUATORS

摘要

When employing a valve in a medical device in or near a bore of a magnetic resonance (MR) scanner, MR-compatible materials are employed to minimize the susceptibility of the valve to the strong magnetic fields generated by the MR scanner. An MR-compatible actuator comprises a shame memory alloy (SMA) wire or member (12) that is actuated by application of a constant power signal. The constant power signal is supplied by a control circuit (50) that is generated using a power feedback signal derived from measured current and voltage feedback signals. Once the SMA member is actuated, the power signal can be reduced and pulse width modulated to maintain the SMA member in an active state, which in turn maintains the valve in a closed state until the power signal is terminated.