METHOD AND APPARATUS FOR DIGITAL SIGNAL PROCESSING FOR RADIO FREQUENCY SURGERY MEASUREMENTS

• US 20090157067A1
• Filed: 12/17/2007
• Published: 06/18/2009
• Est. Priority Date: 12/17/2007
• Status: Active Grant

• Current Assignee: Thermage Incorporated (Bausch Health Cos., Inc.)
• Original Assignee: Thermage Incorporated (Bausch Health Cos., Inc.)
• Inventors: Kane, Mark L., Wyeth, Richard
• Granted Patent: US 8,180,458 B2
• Time in Patent Office: Days
• US Class Current: 606/33
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 18/1233 with circuits for assuring patient safety
• CPC Class Codes: A61B 2018/00684 using lookup tables
• CPC Class Codes: A61B 2018/00827 Current

Abstract

A method and apparatus for calculating current lost through a patient during a treatment of a patient using an electromagnetic energy delivery system is disclosed. The system generates electromagnetic energy, contacts a skin surface of the patient, transfers the electromagnetic energy to tissue beneath the surface of the skin, detects a value of at least one characteristic of the electromagnetic energy utilizing synchronous undersampling, and calculates the current lost through the patient. The characteristic measured may be a value of current of the electromagnet energy. An adjustable matching network may be utilized to maximize power to the tissue of the patient. Values of the impedance of the matching network may be utilized to determine the electromagnetic energy delivered to the tissue of the patient. A current correction factor is determined from the impedance of the matching network and utilized to calculate the current lost through the patient.

Claims

1. A method of measuring electromagnetic energy generated from an electromagnetic energy delivery system, the method comprising:

contacting a skin surface of the patient with a skin contacting portion of the electromagnetic energy delivery system;

generating electromagnetic energy, wherein the electromagnetic energy is a radio-frequency signal;

transferring the electromagnetic energy from the electromagnetic energy delivery system to tissue beneath the skin surface of the patient through the skin contacting portion;

detecting a value of at least one characteristic of the electromagnetic energy, wherein the value is detected utilizing synchronous undersampling; and

calculating a value of current lost through the patient.

2. The method of claim 1, wherein detecting the value of the at least one characteristic comprises:

measuring a value of current from the electromagnetic energy.

3. The method of claim 2, wherein calculating the value of current lost through the patient comprises:

establishing a matching network having an adjustable impedance for the electromagnetic energy delivery system; and

calculating a current correction factor based on a value of patient tissue resistance and a value of tuning inductance,

wherein the matching network is configured to match an impedance of the patient, and a resistive value of the impedance of the matching network corresponds to the value of patient tissue resistance, and an inductive value of the impedance of the matching network corresponds to the value of tuning inductance of the electromagnetic energy delivery system.

4. The method of claim 3, wherein the electromagnetic energy delivery system includes a memory, and calculating the current correction factor comprises:

referencing a software lookup table to determine the current correction factor using the value of patient tissue resistance and the value of tuning inductance, wherein the software lookup table is stored in the memory.

5. The method of claim 3, wherein calculating the value of current lost through the patient further comprises:

calculating the current lost through the patient from the current correction factor and the measured value of current.

6. The method of claim 3, further comprising:

determining the electromagnetic energy transferred to the patient from the value of current lost through the patient and the value of patient tissue resistance.

7. The method of claim 6, further comprising:

substantially terminating the transfer of electromagnetic energy from the electromagnetic energy delivery system when a predetermined value of electromagnetic energy has been transferred to the tissue of the patient.

8. An apparatus for determining a value of current lost through a patient from an electromagnetic energy delivery system during a treatment of the patient, the apparatus comprising:

an electromagnetic energy source operable to generate electromagnetic energy, wherein the electromagnetic energy is a radio-frequency signal;

a coaxial cable electrically connected to the electromagnetic energy source;

an electromagnetic energy delivery device having a skin contacting portion, wherein the electromagnetic energy delivery device is electrically connected to the coaxial cable and configured to contact a skin surface of the patient with the skin contacting portion, and wherein the skin contacting portion transfers the electromagnetic energy to a tissue beneath the skin surface of the patient during the treatment of the patient; and

a control unit electrically connected to the electromagnetic energy source and in electrical communication with the coaxial cable, wherein the control unit is operable to detect a value of at least one characteristic of the electromagnetic energy utilizing synchronous undersampling of the radio-signal on the coaxial cable and to calculate the value of current lost through the patient.

9. The apparatus of claim 8, further comprising:

a sensor electrically connected to the coaxial cable; and

the sensor in electrical communication with the control unit and configured to transmit the value of the least one characteristic of the electromagnetic energy to the control unit.

10. The apparatus of claim 9, wherein the control unit further comprises:

a processing unit; and

a memory.

11. The apparatus of claim 10, further comprising:

an adjustable matching network electrically connected to the coaxial cable, the adjustable matching network configured to maximize power transferred to the patient through the skin contacting portion of the electromagnetic energy delivery device.

12. The apparatus of claim 11, wherein the control unit is further operable to adjust the adjustable matching network.

13. The apparatus of claim 9, wherein the sensor transmits a value of current from the electromagnetic energy to the control unit.

14. The apparatus of claim 13, wherein the control unit is further operable to calculate a current correction factor based on a value of patient tissue resistance and a value of tuning inductance, and a resistive value of the impedance of the matching network corresponds to the value of patient tissue resistance, and an inductive value of the impedance of the matching network corresponds to the value of tuning inductance of the electromagnetic energy delivery system.

15. The apparatus of claim 14, wherein the control unit is further operable to reference a software lookup table in memory to determine the current correction factor using the value of the tissue resistance of the patient and the value of the tuning inductance.

16. The apparatus of claim 14, wherein the control unit is further operable to determine the value of current lost through the patient from the current correction factor and the value of current transmitted by the sensor.

17. The apparatus of claim 14, wherein the control unit is further operable to determine the electromagnetic energy transferred to the patient from the value of current lost through the patient and the value of patient tissue resistance.

18. The apparatus of claim 17, wherein the control unit is further operable to substantially terminate the transfer of electromagnetic energy from the electromagnetic energy delivery system when a predetermined value of electromagnetic energy has been transferred to the tissue of the patient.

19. The apparatus of claim 8, further comprising:

an interface in electrical communication with the control unit.