Implantable medical devices, and methods of use therewith, that detect MRI systems with enhanced specificity

A method for use with an implantable medical device (IMD) having a magnetic field sensor and an accelerometer capable of mode switching to a magnetic resonance imaging (MRI) safe mode, the method comprising:

• (a) using the magnetic field sensor to determine whether a first magnetic field condition is detected;
• (b) in response to determining that the first magnetic field condition is detected, using the accelerometer to determine whether a positional condition is detected;
• (c) in response to determining that the positional condition is detected, using the magnetic field sensor to determine whether a second magnetic field condition is detected, wherein the second magnetic field condition differs from the first magnetic field condition;
• and
• (d) performing a mode switch to the MRI safe mode, based at least in part on determining that the first and second magnetic field conditions and the positional condition are detected;
• wherein:
• the first magnetic field condition comprises a measured magnetic field along a first-axis exceeding a first-axis threshold;
• the second magnetic field condition comprises a measured magnetic field along the first-axis exceeding an increased first-axis threshold;
• step (a) comprises using the magnetic field sensor to determine whether the measured magnetic field along the first-axis exceeds the first-axis threshold;
• step (b) comprises, in response to determining that the measured magnetic field along the first-axis exceeds the first-axis threshold, using the accelerometer to determine whether the positional condition is detected;
• step (c) comprises, in response to determining that the positional condition is detected, using the magnetic field sensor to determine whether the measured magnetic field along the first-axis exceeds the increased first-axis threshold;
• and
• step (d) comprises performing the mode switch to the MRI safe mode, based at least in part on determining at step (a) that the measured magnetic field along the first-axis exceeds the first-axis threshold, determining at step (b) that the positional condition is detected, and determining at step (c) that the measured magnetic field along the first-axis exceeds the increased first-axis threshold.

An implantable medical device (IMD), comprising:

• a magnetic field sensor;
• an accelerometer;
• and
• a controller configured to
• use the magnetic field sensor to determine whether a first magnetic field condition is detected;
• use the accelerometer to determine whether a positional condition is detected;
• use the magnetic field sensor to determine whether a second magnetic field condition is detected, in response to both the first magnetic field condition being detected and the positional condition being detected, wherein the second magnetic field condition differs from the first magnetic field condition;
• and
• cause the IMD to enter a magnetic resonance imaging (MRI) safe mode based at least in part on the first and second magnetic field conditions and the positional condition being detected;
• and
• wherein the first magnetic field condition comprises a measured magnetic field along a first-axis exceeding a first-axis threshold;
• and
• wherein the second magnetic field condition comprises a measured magnetic field along the first-axis exceeding an increased first-axis threshold.

An implantable medical device (IMD), comprising:

• a magnetic field sensor capable of measuring magnetic fields along more than one axes;
• an accelerometer capable of detecting posture of a patient within which the IMD is implanted and capable of detecting motion of the patient;
• and
• a controller configured to
• use the magnetic field sensor to detect when a magnetic field along a first-axis exceeds a first-axis threshold;
• use the accelerometer to detect when a patient is supine and stationary;
• and
• use the magnetic field sensor to detect when a magnetic field along a second-axis exceeds a second-axis threshold, wherein the second-axis is orthogonal to the first-axis;
• the controller also configured to cause the IMD to enter a magnetic resonance imaging (MRI) safe mode based at least in part on the magnetic field sensor being used to detect that magnetic field along the first-axis exceeds the first-axis threshold, the accelerometer being used to detect that the patient is supine and stationary, and the magnetic field sensor being used to detect that magnetic field along the second-axis exceeds the second-axis threshold.