Active adaptive detuning systems and methods for interventional devices

摘要

Active MRI compatible interventional devices, such as catheters, include at least one RF antenna so that they are visible under MRI analysis. However, metallic structures within intravascular devices may heat up significantly during interventional MRI procedures due to eddy current formation over the conductive transmission lines. The electrical field coupling that occurs between interventional devices and RF signals depend on the position and orientation of interventional device within the bore and the insertion length of the interventional device. The system detects an induced current signal during RF transmission phase and selectively adjusts the impedance value associated with the interventional device by using a varactor and integrated circuit components in such a manner that the currents induced in the interventional device are below a threshold current level, thereby controlling current levels and heating in the interventional device.

主权项

1. An active adaptive detuning system for use during a magnetic resonance imaging procedure, the system comprising:
a magnetic resonance imaging system to:
apply a radio frequency radiation signal across a selected portion of a subject; anddiscontinue application of the radio frequency radiation signal across the selected portion of the subject; an interventional device for insertion into the subject and proximate to the selected portion of the subject, the interventional device comprising:
a radio frequency antenna at a distal end of the interventional device to receive an induced current based on another radio frequency signal emitted from tissue surrounding the radio frequency antenna when the interventional device is inserted in the subject; andan inner conductor along a length of the interventional device and connected to the radio frequency antenna to conduct the induced current; an adaptive detuning circuit connected to the inner conductor to:
iteratively adjust an impedance value of the interventional device through each of a plurality of impedance values;determine a corresponding magnitude of the induced current in the inner conductor for each of the plurality of impedance values; andset the impedance value of the interventional device to a first one of the plurality of impedance values where the corresponding magnitude of the induced current is below a threshold current level to limit heating of the interventional device when inserted within the subject;the adaptive detuning circuit comprising:
a balun circuit to balance impedances between the interventional device and the magnetic resonance imaging system;a matching circuit to dynamically vary the impedance value of the inner conductor to disrupt resonant conditions;a detuning circuit to connect and disconnect the radio frequency antenna from the magnetic resonance imaging system in response to a DC control signal; anda control circuit to:
generate the DC control signal when the magnetic resonance imaging system applies the radio frequency radiation signal;detect the magnitude of the induced current in the inner conductor;retrieve the threshold current level from a memory;iteratively adjust the impedance value by adjusting an adaptive detuning capacitance of the adaptive detuning circuit through a series of detuning capacitance values based on the detected magnitude of the induced current;determine the corresponding magnitude of the induced current in the inner conductor for each of the detuning capacitance values;compare the corresponding magnitude of each induced current to the threshold current value; andset the detuning capacitance value to a first one of the detuning capacitance values where the corresponding magnitude of the induced current is below the threshold current level.