Ultra miniature pressure sensor and guide wire using the same and method

• US 6,106,476 A
• Filed: 08/15/1997
• Issued: 08/22/2000
• Est. Priority Date: 09/02/1994
• Status: Expired due to Term

• Current Assignee: Volcano Corporation (Koninklijke Philips N.V.)
• Original Assignee: Endosonics Corporation (JOMED NV)
• Inventors: Ortiz, John E., Obara, Robert Z., Corl, Paul D.
• Primary Examiner(s): Nasser, Robert L.
• Application Number:
  US08/912,879
• Time in Patent Office: 1,103 Days
• Field of Search: 600/501, 600/488, 600/486, 600/437
• US Class Current: 600/486
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/6851 Guide wires
• CPC Class Codes: A61B 8/06 Measuring blood flow measuring volume flow in general G01F, e.g. G01F1/66, G01F1/72; measuring speed of fluids in general G01P5/00
• CPC Class Codes: A61B 8/12 in body cavities or body tracts, e.g. by using catheters catheters per se A61M25/00
• CPC Class Codes: A61M 2025/0002 with a pressure sensor at the distal end
• CPC Class Codes: A61M 2025/09008 having a balloon
• CPC Class Codes: A61M 2025/09083 having a coil around a core
• CPC Class Codes: A61M 25/09 Guide wires
• CPC Class Codes: A61M 25/10 Balloon catheters A61M25/0125 takes precedence; embolectomy A61B17/22032; retractors A61B17/02; inflatable balloons for placing stents or stent-grafts A61F2/958 ; stomach balloons for treatment of obesity A61F5/0003; oesophagal tubes A61J15/00
• CPC Class Codes: G01L 19/0084 to the outside of the housing other details about the housing see G01L19/14
• CPC Class Codes: G01L 19/141 Monolithic housings, e.g. molded or one-piece housings
• CPC Class Codes: G01L 19/147 Details about the mounting of the sensor to support or covering means
• CPC Class Codes: G01L 19/149 of immersion sensor, e.g. where the sensor is immersed in the measuring medium or for in vivo measurements, e.g. by using catheter tips
• CPC Class Codes: G01L 9/0054 integral with a semiconducting diaphragm

Abstract

A guide wire having pressure sensing capabilities for measuring the pressure of liquid in a vessel comprising a flexible elongate member and having proximal and distal extremities and having an outside diameter of 0.018" or less. The distal extremity of said flexible elongate member is adapted to be disposed in the liquid in said vessel. A housing is carried by the flexible elongate member and has a diameter substantially the same as the diameter of the flexible elongate member. The housing has a space therein with a pressure sensor mounted in the space in the housing. The pressure sensor has a diaphragm that is sensitive to changes of pressure in the liquid in the vessel. The diaphragm is rectangular in shape and is bordered by a rim surrounding the well. A backing plate is formed of an insulating material bonded to the crystal and serves to reinforce the rim of the crystal of semiconductor material. The backing plate has a cavity therein underlying the diaphragm and is in substantial registration with the diaphragm. The cavity serves to provide a pressure reference.

Claims

1. A guide wire having pressure sensing capabilities for measuring the pressure of liquid in a vessel comprising a flexible elongate member and having proximal and distal extremities and having an outside diameter of 0.018" or less, said distal extremity of said flexible elongate member being adapted to be disposed in the liquid in said vessel, a housing carried by the distal extremity of the flexible elongate member and having an outer surface with a diameter substantially the same as the diameter of the flexible elongate member and being axially collinear with the flexible elongate member so that it forms an integral portion of the distal extremity of the flexible elongate member, said housing having a space therein, a pressure sensor mounted in the space in the housing, and having an outer surface flush with the outer surface of the housing the pressure sensor comprising a crystal of semiconductor material having a well therein open to ambient defined in part by a bottom wall forming a diaphragm having a thickness, said diaphragm being disposed in the housing in a manner so that it is sensitive to changes of pressure in the liquid in the vessel, said diaphragm being rectangular in shape and being bordered by a rim surrounding the well and formed of the crystal of semiconductor material, a backing plate formed of an insulating material bonded to the crystal and serving to reinforce the rim of the crystal of semiconductor material, said backing plate having a cavity therein underlying the diaphragm and providing a pressure reference, said cavity having the same size as the diaphragm and in substantial registration with the diaphragm so that the diaphragm is free of the backing plate, said crystal of semiconductor material having at least one diffused region therein formed of an impurity, said diffused region overlying the portion of the diaphragm where deflection will occur whereby upon the application of a pressure to the diaphragm a change in resistance will occur in the diffused region, conductive means carried by the crystal of semiconductor material and coupled to said at least one diffused region, a power source connected to the conductor means for supplying electrical energy to said at least one diffused region and means measuring the change in resistance in said at least one diffused region to ascertain the pressure being applied to the diaphragm by the liquid in the vessel.

2. A guide wire as in claim 1 together with means connected to the conductive means including no more than three leads for compensating for temperature changes of the pressure sensor during the time that pressures are being sensed by the pressure sensor.

3. A guide wire as in claim 1 wherein said diaphragm has first and second spaced-apart portions wherein said diffused region includes first and second diffused portions, said first and second diffused portions overlying said first and second spaced-apart -portions of the diaphragm and serving as first and second resistor elements having opposite ends to provide a two-resistor device.

4. A guide wire as in claim 3 wherein said resistor elements have nominal resistances ranging from 2.5 to 4.5 kilohms and wherein the first and second diffused regions will provide nominally a 100 millivolt output with a 1 milliampere drive, and a pressure change of 300 mm of mercury.

5. A guide wire as in claim 1 together with adhesive means carried by the housing for securing said pressure sensor in said housing.

6. A guide wire as in claim 1 together with a velocity sensor including a velocity transducer mounted on the distal extremity of the guide wire so as to make possible simultaneous pressure and velocity measurements.

7. A guide wire as in claim 1 wherein said housing is a tip housing and wherein said pressure sensor is mounted in the tip housing.

8. A guide wire as in claim 7 wherein said vessel is an arterial vessel with a stenosis therein together with an additional housing spaced from the tip housing and an additional pressure sensor mounted in said additional housing to make possible simultaneous pressure measurements on the proximal and distal extremities of the stenosis in the arterial vessel after the guide wire has been advanced through the stenosis.

9. A guide wire as in claim 1 together with a balloon mounted on the distal extremity of the guide wire.

10. A guide wire as in claim 1 together with means enclosing the pressure sensor within the housing and having a pin hole opening therein in communication with the well in the semiconductor crystal overlying the diaphragm.

11. A guide wire as in claim 10 together with a viscous fluid underlying said covering means and serving to establish communication through the pin hole of the pressure of liquid in the vessel encountered by the distal extremity of the guide wire.

12. Apparatus for measuring the pressure proximally and distally of a stenosis in a blood carrying vessel, a flexible elongate member having a diameter of 0.018" or less and having a flexible floppy distal extremity with first and second spaced-apart coils, said flexible elongate member including means providing torsion capabilities facilitating steering of the distal extremity in the vessel a housing having an outer surface and having a space therein secured to and formed integral with and being collinear within the 0.018" diameter of the distal extremity of the flexible elongate member and disposed distally of at least one of the first and second coils, a pressure sensor mounted in the housing and having an outer surface flush with the outer surface of the housing and leads connected to the pressure sensor and extending through the flexible elongate member, said pressure sensor including a movable diaphragm that is adapted to be placed in communication with the pressure of the blood in the vessel and deflecting in accordance with the pressure of the blood in the vessel, first and second resistive elements carried by the diaphragm, leads coupled to the resistive elements and extending to the proximal extremity of the flexible elongate member, means for supplying a current to the resistive elements and means for measuring changes in voltage as the diaphragm is deflected to ascertain the pressure being measured by the pressure sensor.

13. A guide wire for making measurements in liquid in a vessel and for use with a catheter comprising a flexible elongate member having proximal and distal extremities and having an outside diameter of 0.018" or less, said distal extremity of said flexible elongate member having at least one coil therein to provide a floppy distal extremity, said floppy distal extremity being adapted to be disposed in the liquid in said vessel, said flexible elongate member including means for providing torsion capabilities facilitating steering of the floppy distal extremity in the vessel, said distal extremity including a flexible coil having proximal and distal extremities, an ultrasonic transducer, means securing the ultrasonic transducer to the distal extremity of the coil, a housing having an outer surface and secured to the proximal extremity of the coil and being formed integral with and collinear within the 0.018" diameter of the distal extremity of the flexible elongate member, a piezoresistive pressure sensor mounted in the housing, and having an outer surface flush with the outer surface of the housing conductive leads connected to the pressure sensor and to the ultrasonic transducer extending through the flexible elongate member to the proximal extremity, a removable housing removably secured to the proximal extremity of the flexible elongate member, said housing including means for making electrical contact with the leads connected to the pressure sensor and to the ultrasonic transducer, said removable housing being removable so as to provide a low profile on the proximal extremity of the flexible elongate member so that if necessary the catheter can be advanced or retracted over the guide wire while the distal extremity of the guide wire is in a fixed position within the vessel.

14. A guide wire as in claim 13, wherein said distal extremity of said flexible elongate member is provided with an additional coil having proximal and distal extremities with the distal extremity of the additional coil being secured to the housing carrying the pressure transducer and wherein the proximal extremity of the additional coil is secured to the distal extremity of the flexible elongate member.

15. A guide wire having pressure sensing capabilities for measuring the pressure of liquid in a vessel comprising a flexible elongate member and having proximal and distal portions and having an outside diameter of 0.018" or less, said distal portion of said flexible elongate member being adapted to be disposed in the liquid in said vessel, a housing carried by the distal portion of the flexible elongate member and having an outer surface with a diameter substantially the same as the diameter of the flexible elongate member and being axially collinear with the flexible elongate member so that it forms an integral portion of the distal portion of the flexible elongate member, said housing having a space therein, a pressure sensor mounted in the space in the housing, and having an outer surface flush with the outer surface of the housing the pressure sensor comprising a crystal of semiconductor material including having a well therein open to ambient defined in part by a bottom wall forming a diaphragm having a thickness, said diaphragm being disposed in the housing in a manner so that it deflects in response to changes of pressure in the liquid in the vessel, and a backing plate underlying the body of semiconductor material and having a cavity therein underlying the diaphragm for providing a pressure reference, said cavity having the same size as the diaphragm and in substantial registration with the diaphragm so that the diaphragm is free of the backing plate, the body of semiconductor material having at least one resistor overlying a portion of the diaphragm where deflection will occur whereby upon the application of a pressure to the diaphragm a change in resistance will occur in the resistor.

16. A guide wire having pressure and velocity sensing capabilities for measuring the pressure and velocity of a moving liquid in a vessel comprising a flexible elongate member having proximal and distal extremities and having an outside diameter of 0.018" or less, said distal extremity of said flexible elongate member being adapted to be disposed in the liquid in said vessel, a housing carried by the distal extremity of the flexible elongate member and having an outer surface with a diameter substantially the same as the diameter of the flexible elongate member and being axially collinear with the flexible elongate member so that it forms an integral portion of the distal extremity of the flexible elongate member, said housing having a space therein, a pressure sensor including a pressure transducer providing an electrical output mounted in the space in the housing, and having an outer surface flush with the outer surface of the housing an electrical connector connected to the pressure transducers said pressure transducer serving to ascertain the pressure being applied to the pressure transducer by the liquid in the vessel, a velocity sensor including a velocity transducer providing an electrical output mechanically coupled to the distal extremity of the flexible elongate member for measuring the velocity of the moving liquid in the vessel, and electrical conductors connected to the pressure transducer and the velocity transducer for receiving the electrical outputs provided by the pressure transducer and the velocity transducer.

17. A guide wire as in claim 16, wherein the distal extremity of the flexible elongate member includes a coil disposed between the housing and the velocity sensor.

18. A guide wire as in claim 17, wherein which the velocity transducer is an ultrasonic transducer.

19. A guide wire as in claim 16, wherein said flexible elongate member includes means providing torsion capabilities facilitating steering of the distal extremity in the vessel.