Circuit apparatus and method for electrothermal treatment of cancer eye

• US 4,644,955 A
• Filed: 03/04/1985
• Issued: 02/24/1987
• Est. Priority Date: 12/27/1982
• Status: Expired due to Term

• Current Assignee: RDM International, Inc.
• Original Assignee: RDM International, Inc.
• Inventors: Mioduski, Paul
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US06/708,007
• Time in Patent Office: 722 Days
• Field of Search: 128/422, 128/399, 128/736, 128/303.1, 128/800, 128/804, 128/419 R, 128/421, 128/303.13
• US Class Current: 607/99
• CPC Class Codes: A61B 18/12 by passing a current through the tissue to be heated, e.g. high-frequency current
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 18/14 Probes or electrodes therefor
• CPC Class Codes: A61B 18/1402 Probes for open surgery
• CPC Class Codes: A61B 2017/00084 Temperature
• CPC Class Codes: A61B 2017/00088 using thermistors
• CPC Class Codes: A61B 2017/00115 with audible or visual output
• CPC Class Codes: A61B 2017/00132 Setting operation time of a device A61B2017/00123 takes precedence
• CPC Class Codes: A61B 2018/0066 without feedback, i.e. open loop control
• CPC Class Codes: A61D 1/00 Surgical instruments for veterinary use

Abstract

Circuitry for use in a hand-held electronic probe for passing high frequency current through malignant eye tissue of livestock or other tissue such as warts includes a thermistor in a probe tip that contacts the tissue, producing a voltage that controls a voltage controlled oscillator which drives an audio transducer. If, during treatment, the probe tip is held against the malignant tissue with sufficient force, the pitch of a sound emitted by the audio transducer steadily increases, indicating to the user that proper pressure is being maintained to ensure heating of the tissue to the desired treatment temperature. The circuitry then causes the transducer to emit periodic beeping signals which the user can count to ensure that the tissue is maintained in a desired elevated temperature range for a desired amount of time. Circuitry responsive to the temperature sensor varies the duty cycle of the high frequency current applied to the tissue to maintain the elevated temeperature thereof within a predetermined range. Initially, the high frequency current is applied at a substantially reduced duty cycle to prevent excessive temperature lag between the tissue and the probe tip to prevent initial temperature overshoot of the tissue before the thermistor and circuitry can respond to reduce the duty cycle.

Claims

1. In an apparatus for electrothermal treatment of unhealthy tissue, a circuit for producing a flow of a high frequency current through the unhealthy tissue to heat it without damaging adjacent healthy tissue, said electrothermal apparatus including first and second spaced current probes each having a contact surface for electrically contacting the surface of said unhealthy tissue to thereby conduct said high frequency current through said unhealthy tissue, said electrothermal treatment apparatus also including output oscillating circuit means for producing a high frequency voltage signal for application across said first and second current probes to cause said high frequency current to flow through said unhealthy tissue if said contact surfaces are held sufficiently forcefully against the surface of said unhealthy tissue, said output oscillating circuit means including a control input for receiving a duty cycle signal for regulating the duty cycle of the flow of high frequency current,

said circuit comprising in combination:

(a) temperature sensing means for sensing the temperature of said first current probe to produce a first electrical signal representative of the temperature of said first probe, the temperature of said first current probe being indicative of the temperature of said unhealthy tissue and hence the amount of said high frequency current flowing through said unhealthy tissue, the amount of said high frequency current flowing through said unhealthy tissue being dependent upon the contact resistance between said unhealthy tissue and said first and second current probes, said contact resistance between said unhealthy tissue and said first and second current probes being dependent upon the force with which said first and second current probes are held against said unhealthy tissue;

(b) voltage controlled oscillating circuit means responsive to said first electrical signal for producing an audio signal representative of the temperature of said first current probe and indicative of the sufficiency the forces pressing said contact surfaces of first and second current probes against said unhealthy tissue;

(c) audio transducer means responsive to said audio sound for producing an audible sound, the pitch of which represents the temperature of said first current probe and hence the temperature of said unhealthy tissue, the rate of change of the pitch being indicative of said sufficiency of said forces when said unhealthy tissue is being heated by said high frequency current;

(d) regulating circuit means for generating said duty cycle signal for application to said control input of said oscillating circuit means; and

(e) delay circuit means for reducing the duty cycle of said high frequency current to a predetermined level for a predetermined initial time period after initial application of operating power to said circuit, to prevent initial overheating of said tissue due to thermal lag between heating of said unhealthy tissue by said high frequency current and heating of said first current probe by themal conduction of heat thereto from said unhealthy tissue;

whereby the user of said electrothermal treatment apparatus can be immediately notified of a condition of insufficient contact surface pressure of the either of said first and second current probes against said unhealthy tissue by a predetermined change in the pitch of said audible sound and can thereby immediately increase the contact surface pressure.

2. In an apparatus for electrothermal treatment of unhealthy tissue, a circuit for producing a flow of a high frequency current through the unhealthy tissue to heat it without damaging adjacent healthy tissue, said electrothermal apparatus including first and second spaced current probes each having a contact surface for electrically contacting the surface of said unhealthy tissue to thereby conduct said high frequency electrical current through said unhealthy tissue, said electrothermal treatment apparatus also including output oscillating circuit means for producing a high frequency voltage signal for application across said first and second current probes to cause said high frequency current to flow through said unhealthy tissue if said contact surfaces are held sufficiently forcefully against the surface of said unhealthy tissue, said output oscillating circuit means including a control input,

said circuit comprising in combination:

(a) temperature sensing means for sensing the temperature of said first current probe to produce a first electrical signal representative of the temperature of said first probe;

(b) delay circuit means for reducing the duty cycle of said high frequency current to a predetermined level for a predetermined initial time period after initial application of operating power to said circuit, to prevent initial overheating of said tissue due to thermal lag between heating of said unhealthy tissue by said high frequency current and heating of said first current probe by thermal conduction of heat thereto from said unhealthy tissue;

(c) means responsive to said control input for halting oscillation of said output oscillating circuit means when said control input is at a first signal level; and

(d) regulating circuit means responsive to said first electrical signal and coupled to so said control input means for periodically interrupting oscillating of said output oscillating circuit means after said predetermined initial time period in order to reduce a duty cycle of said high frequency current and thereby reduce the amount of heating of said unhealthy tissue by said high frequency current.

3. A method of operating an apparatus to electrothermally treat unhealthy tissue by conducting high frequency current through first and second current probes and through said unhealthy tissue to cause heating of said unhealthy tissue to at least a first predetermined temperature for at least a predetermined amount of time in order to kill said unhealthy tissue without causing undue damage to adjacent healthy tissue, said method comprising the steps of:

(a) pressing each of said first and second current probes against the surface of said unhealthy tissue with sufficient force to reduce the contact resistance between said first and second probes and said unhealthy tissue to a level that enables a predetermined amount of said high frequency current to flow through the unhealthy tissue disposed between said first and second current probes;

(b) applying electrical power to a circuit that produces a high frequency voltage across said first and second current probes to cause said high frequency current to flow, the voltage and current being at a particular duty cycle;

(c) conducting said high frequency current from one of said first and second current probes through said unhealthy tissue between said first and second current probes to the other of said first and second current probes to cause heating of that unhealthy tissue, heat from said unhealthy tissue flowing by thermal conduction to said first current probe and raising the temperature thereof, the temperature of said first current probe being indicative of the temperature of said unhealthy tissue and hence the amount of said high frequency current flowing through said unhealthy tissue, the amount of said high frequency current flowing through said unhealthy tissue being dependent upon the contact resistance between said unhealthy tissue and said first and second current probes, said contact resistance between said unhealthy tissue and said first and second current probes being dependent upon the force with which said first and second current probes are held against said unhealthy tissue;

(d) sensing the temperature of said first probe to produce a first electrical signal;

(e) producing an audio frequency signal representative of the temperature of said first current probe and indicative of said sufficieny of said forces, and applying said audio frequency signal to an audio frequency sound transducer which produces an audible sound, the pitch of which is presentative of the temperature of said first current probe, and the rate of change of said pitch being indicative of said sufficiency of said forces, the pitch of said sound gradually increasing and informing a person operating said apparatus whether that person is applying adequate pressure on both of said first and second current probes to cause adequate electrical current to flow through said first and second current probes and said unhealthy tissue to raise the temperature thereof at a satisfactory rate; and

(f) limiting the duty cycle of said high frequency voltage and said high frequency current to a predetermined duty cycle for a predetermined amount of time after the beginning of said conducting of said high frequency current through said unhealthy tissue, said predetermined duty cycle having a value which prevents initial heating of said unhealthy tissue at a rate that excessively exceeds the rate of thermal conductive heating of said first probe by the heated unhealthy tissue.

4. In an apparatus for electrothermal treatment of unhealthy tissue, a circuit for producing a flow of high frequency current through the unhealthy tissue to heat it without damaging adjacent healthy tissue, said electrothermal apparatus including first and second spaced current probes each having a contact surface for electrically contacting the surface of said unhealthy tissue to thereby conduct said high frequency electrical current through said unhealthy tissue, said electrothermal treatment apparatus also including output oscillating circuit means for producing a high frequency voltage signal for application across said first and second current probes to cause said high frequency current to flow through said unhealthy tissue if said contact surfaces are held sufficiently forcefully against the surface of said unhealthy tissue,

said circuit comprising in combination:

(a) temperature sensing means for sensing the temperature of said first current probe to produce a first electrical signal representative of the temperature of said first probe, the temperature of said first current probe being indicative of the temperature of said unhealthy tissue and hence the amount of said high frequency current flowing through said unhealthy tissue, the amount of said high frequency current flowing through said unhealthy tissue being dependent upon the contact resistance between said unhealthy tissue and said first and second current probes, said contact resistance between said unhealthy tissue and said first and second current probes being dependent upon the force with which said first and second current probes are held against said unhealthy tissue;

(b) voltage controlled oscillating circuit means responsive to said first electrical signal for producing an audio signal representative of the temperature of said first current probe and indicative of the sufficiency of the forces pressing said contact surfaces of first and second current probes against said unhealthy tissue;

(c) audio transducer means responsive to said audio signal for producing an audible sound, the pitch of which represents the temperature of said first current probe and hence the temperature of said unhealthy tissue, the rate of change of the pitch being indicative of said sufficiency of said forces when said unhealthy tissue is being heated by said high frequency current; and

whereby the user of said electrothermal treatment apparatus can be immediately notified of a condition of insufficient contact surface pressure of the other of said first and second current probes against said unhealthy tissue by a predetermined change in the pitch of said audible sound and can thereby immediately increase the contact surface pressure.