Induced current measurement systems and methods

• US 8,014,856 B2
• Filed: 12/14/2010
• Issued: 09/06/2011
• Est. Priority Date: 02/28/2007
• Status: Expired due to Fees

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Wedan, Steve R.
• Primary Examiner(s): Manuel; George
• Assistant Examiner(s): Wieland; Robert N
• Application Number:
  US12/967,949
• Publication Number:
  US 20110084714A1
• Time in Patent Office: 266 Days
• Field of Search: 600/423, 623/1.13, 607/2, 607/9, 607/63, 607/27
• US Class Current: 607/2
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61N 1/3718 Monitoring of or protection against external electromagnetic fields or currents
• CPC Class Codes: G01R 19/0092 measuring current only all subgroups of G01R19/00 take precedence
• CPC Class Codes: G01R 33/285 Invasive instruments, e.g. catheters or biopsy needles, specially adapted for tracking, guiding or visualization by NMR
• CPC Class Codes: G01R 33/288 Provisions within MR facilities for enhancing safety during MR, e.g. reduction of the specific absorption rate [SAR], detection of ferromagnetic objects in the scanner room

Abstract

In an embodiment, the invention includes a measurement system for measuring induced currents within an implantable medical device undergoing magnetic resonance imaging. The measurement system can include a resistor connected in series with a conductive loop and electronic circuitry configured to generate a signal representative of a voltage differential across the resistor. In some embodiments, the measurement system includes a fiber optic cable configured to transmit the signal away from the area subject to magnetic resonance imaging. In some embodiments, the measurement system includes a transmitter to wirelessly transmit the signal away from the area subject to magnetic resonance imaging. In an embodiment, the invention can include an implantable medical device including a measurement system for measuring induced currents. In an embodiment, the invention can include a method of measuring an induced current in an implantable medical device undergoing magnetic resonance imaging. Other embodiments are described herein.

Claims

1. A measurement system for measuring induced current in an implantable medical device undergoing magnetic resonance imaging, the measurement system comprising an implantable medical device comprising:

a resistor;

a conductive loop comprising a pulse generator and a lead, the conductive loop in series with the resistor;

electronic circuitry configured to generate an electronic signal representative of a voltage differential across the resistor; and

telemetry circuitry configured to allow the implantable medical device to communicate with an external device.

2. The measurement system of claim 1, further comprising an external device configured to receive a wireless signal from the implantable medical device.

3. The measurement system of claim 1, wherein the resistor has a resistance of between about 1 ohms and about 50 ohms.

4. The measurement system of claim 3, the resistor connected in series between the pulse generator and the lead.

5. The measurement system of claim 1, the electronic signal representing a voltage differential between two locations less than 5 mm apart.

6. The measurement system of claim 1, the electronic circuitry comprising an analog to digital converter.

7. The measurement system of claim 2, wherein the computing device is further configured to determine an induced current level from the voltage differential signal.

8. The measurement system of claim 2, the induced current having a frequency of less than about 20 kHz.

9. A method of measuring an induced current in an implantable medical device undergoing magnetic resonance imaging, the method comprising:

(i) using an implantable medical device to generate an electronic signal representative of the voltage differential across a resistor connected in series with a conductive loop in the implantable medical device, wherein the conductive loop comprises a pulse generator and a lead; and

(ii) wirelessly communicating the signal from the implantable medical device to an external device using wireless telemetry.

10. The method of claim 9, the resistor connected in series between a pulse generator and the lead.

11. The method of claim 9, the electronic voltage differential signal representing the voltage differential between two locations less than 5 mm apart.

12. The method of claim 9, further comprising the step of converting the electronic signal from analog to digital.

13. The method of claim 9, the computing device further configured to determine an induced current level from the voltage differential signal.

14. The method of claim 9, wherein the wireless communication between the implantable medical device and the external device occurs in real time while a patient undergoes an MRI procedure.

15. A measurement system for measuring induced current in an implantable medical device undergoing magnetic resonance imaging, the measurement system comprising:

(i) a lead;

(ii) a resistor configured to be connected in series with a conductive loop of the implantable medical device defined by the lead and a pulse generator, the resistor disposed outside of the pulse generator;

(iii) electronic circuitry configured to generate an electronic signal representative of a voltage differential across the resistor and to generate an optical signal corresponding to the electronic signal; and

(iv) a fiber optic cable configured to transmit the optical signal away from an area subject to magnetic resonance imaging.