Method and apparatus for disconnecting the tip electrode during MRI

A method for selectively connecting a pulse generator and an electrode, the method comprising:

• controlling a state of a first switch coupled along a first conductive path between the pulse generator and the electrode such that, in the absence of a magnetic field, the first switch is closed to electrically connect the pulse generator and the electrode via the first conductive path, and in the presence of the magnetic field, the first switch is open to electrically disconnect the first conductive path between the pulse generator and the electrode;
• and
• controlling a state of a second switch coupled along a second conductive path between the pulse generator and the electrode such that the second switch is open to electrically disconnect the second conductive path between the pulse generator and the electrode when a voltage applied across the second switch is less than or equal to a threshold voltage, and second switch is closed to electrically connect the pulse generator and the electrode via the second conductive path when the voltage applied across the second switch is greater than the threshold voltage.

A method for delivering therapy from a pulse generator to an electrode, the pulse generator connected to the electrode via first and second conductive paths, comprising:

• delivering one or more therapy signals at a first voltage level when the pulse generator is operating in a normal mode in the absence of a magnetic field, the one or more therapy signals at the first voltage level reaching the electrode via the first conductive path;
• and
• delivering one or more therapy signals from the pulse generator at a second voltage level when the pulse generator is operating in an MRI mode in the presence of the magnetic field, the second voltage level greater than the first voltage level, the one or more therapy signals from the pulse generator at the second voltage level reaching the electrode via the second conductive path.