Surgical needle probe for electrical impedance measurements

• US 6,337,994 B1
• Filed: 04/27/1999
• Issued: 01/08/2002
• Est. Priority Date: 04/30/1998
• Status: Active Grant

• Current Assignee: Johns Hopkins University
• Original Assignee: Johns Hopkins University
• Inventors: Stoianovici, Dan, Jackman, Stephen, Allaf, Mohamad, Kavoussi, Louis R.
• Primary Examiner(s): Lateef, Marvin M.
• Assistant Examiner(s): Lin, Jeoyuh
• Application Number:
  US09/300,277
• Time in Patent Office: 987 Days
• Field of Search: 600/547, 600/372, 600/373, 600/424, 606/130, 433/32, 433/27, 433/72
• US Class Current: 600/547
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/0538 invasively, e.g. using a catheter
• CPC Class Codes: A61B 5/6848 Needles

Abstract

An electrical impedance probe is provided that includes a surgical needle. In an exemplary embodiment, the probe is a two-part trocar needle designed to acquire impedance measurements at its tip. The impedance measurements are representative of the local properties of a biological substance at the needle tip. Thus, the probe may be used to confirm needle insertion into a desired anatomical target or to identify the nature of the cells surrounding the tip of the needle. In urology, this sensor is used for confirming the needle insertion into the urinary tract, for localizing renal cell carcinoma, and prostate cancer.

Claims

1. A surgical probe for obtaining impedance measurements, comprising:

a hollow trocar sleeve having a proximal end portion, a distal end, a first electrically conductive portion defining a first electrode adjacent said distal end, and means for electrically connecting said first electrically conductive portion to said proximal end portion;

a stylet having a proximal end portion, a distal end, a second electrically conductive portion defining a second electrode adjacent said distal end, and means for electrically connecting said second electrically conductive portion to said proximal end portion, said stylet being housed within said trocar sleeve;

an electrical insulator disposed between said trocar sleeve and said stylet; and

impedance meter means operatively coupled to said proximal end portion of each of said trocar sleeve and said stylet so as to be electrically coupled to said first and second electrodes, for indicating the impedance of a biological substance contacting said electrodes.

2. A surgical probe as in claim 1, wherein said distal end of said stylet has a sharp, pointed tip.

3. A surgical probe as in claim 1, wherein said electrical insulator comprises a sleeve of insulating material disposed on said stylet, wherein said stylet is selectively slidably removable from said trocar sleeve, and wherein said sleeve of insulating material is removable from said trocar sleeve with said stylet.

4. A surgical probe as in claim 1, wherein said trocar sleeve is formed from an electrically conductive material whereby said means for electrically connecting said first electrically conductive portion to said proximal end portion comprises a wall of the trocar sleeve intermediate said proximal end portion and said distal end thereof.

5. A surgical probe as in claim 1, wherein said stylet is formed from an electrically conductive material whereby said means for electrically connecting said second electrically conductive portion to said proximal end portion comprises a main body of the stylet intermediate said proximal end portion and said distal end thereof.

6. A surgical probe as in claim 1, further comprising an electrical lead extending from said proximal end portion of each of said stylet and said trocar sleeve, and wherein said impediance meter is electrically coupled to said electrical leads.

7. A surgical probe as in claim 1, further comprising a layer of insulating material disposed in surrounding relation to said trocar sleeve, proximal of said first electrode, so as to electrically insulate the trocar sleeve, proximal of said first electrode, from a material into which the probe has been inserted.

8. A method for determining the position of a probe in tissue, comprising the steps of:

providing an impedance probe including a hollow needle barrel having a proximal end portion, a distal end, a first electrically conductive portion defining a first electrode adjacent said distal end, and means for electrically connecting said first electrically conductive portion to said proximal end portion;

a stylet having a proximal end portion, a distal end, a second electrically conductive portion defining a second electrode adjacent said distal end, and means for electrically connecting said second electrically conductive portion to said proximal end portion, said stylet being slideably housed within said needle barrel; and

an electrical insulator disposed between said needle barrel and said stylet; and

impedance meter means operatively coupled to said proximal end portion of each of said needle barrel and said stylet so as to be electrically coupled to said first and second electrodes, for indicating the impedance of a biological substance contacting said electrodes;

inserting the impedance probe into a patient'"'"'s body;

measuring the impedance between two points in a biological substance at a distal tip of said probe, corresponding to said first and second electrodes; and

determining the location of the distal tip of said probe by monitoring the measured impedance.

9. A method as in claim 8, further comprising identifying the biological substance from the measured impedance.

10. A diagnostic impedance measuring system comprising:

an elongate tissue-penetrating needle having a distal end and a proximal end;

a first portion of said distal end of said tissue penetrating needle being electrically conductive;

at least one electrode structure mounted to the needle and disposed adjacent the distal end of the needle and axially spaced from said first portion thereof, said first portion and said at least one electrode being electrically connected to an impedance measuring device for measuring an electrical impedance of a biological substance contacting said first portion and said electrode.

11. A diagnostic impedance measuring system as in claim 10, wherein said electrically conductive electrode structure comprises a sleeve sized to be slidably received on said tissue-penetrating needle, at least a distal portion of said sleeve being electrically conductive;

and further comprising an insulating material disposed between said first portion of said tissue-penetrating needle and said electrically conductive distal portion of said sleeve.

12. An impedance-based method for monitoring a position of a surgical needle comprising the steps of:

providing a needle probe comprising a hollow sleeve and a tissue piercing stylet slidably received therewithin, said stylet being formed from an electrically conductive material whereby a distal end thereof defines a first electrode structure, at least a distal portion of said sleeve comprising an electrically conductive material thereby defining a second electrode structure, said first and second electrodes being electrically insulated from one another;

electrically connecting said electrodes to an impedance meter;

inserting said needle into a patient, toward a target anatomical structure; and

monitoring during said insertion step the impedance between the two electrodes.

13. A method as in claim 12, further comprising determining a location of the distal end of the needle probe from the measured impedance.

14. A method as in claim 12, further comprising identifying the biological substance adjacent the distal end of the needle probe from the measured impedance.