Non-invasive in vivo pressure measurement

• US 20020052550A1
• Filed: 10/30/2001
• Published: 05/02/2002
• Est. Priority Date: 06/12/1998
• Status: Active Grant

• Current Assignee: George A. Taylor, Joseph R. Madsen
• Original Assignee: George A. Taylor, Joseph R. Madsen
• Inventors: Taylor, George A., Madsen, Joseph R.
• Granted Patent: US 6,547,734 B2
• Time in Patent Office: Days
• US Class Current: 600/438
• CPC Class Codes: A61B 5/0053 by applying pressure, e.g. compression, indentation, palpation, grasping, gauging
• CPC Class Codes: A61B 8/04 Measuring blood pressure
• 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 8/0808 for diagnosis of the brain

Abstract

Apparatus and methods are disclosed for non-invasive measurement of blood velocity in otherwise inaccessible body regions, and for correlating such measurements with externally applied pressure to detect and/or assess diseases or physiological abnormalities. The blood velocity measurements can be based on the Doppler shift that occurs when an ultrasonic wave is scattered by moving particles within the blood. Since blood vessels have elastic walls, the geometry of the walls, and therefore the flow dynamics, will change in response to elevated in vivo pressure. The change in resistance to blood flow resulting from these pressure induced changes to the blood vessel wall geometry can provide a measure of intracranial pressure, ophthalmic pressure or various other body conditions that affect blood perfusion. Since the blood vessel wall geometry changes rapidly in response to such changes in pressure, the invention can be used to detect hydrocephalus, retinopathy, papilledema and other physiological abnormalities manifested by pressure changes.

Claims

1. An apparatus for ultrasonically evaluating an in vivo pressure, the apparatus comprising:

an ultrasonic transducer for transmitting a first ultrasonic wave to an in vivo target region and detecting a second ultrasonic wave reflected from the in vivo target region;

a pressure applicator acoustically coupled to the ultrasonic transducer for applying an external pressure to the target region, the pressure applicator being filled with an acoustically transmissive medium for propagation of the first and second ultrasonic waves between the transducer and the target region;

a pressure sensor coupled to the pressure applicator for measuring the external pressure applied by the pressure applicator; and

a data processor in communication with the pressure sensor and the ultrasonic transducer for evaluating an in vivo pressure based on the external pressure and the first and second ultrasonic waves.

2. The apparatus according to claim 1 wherein the pressure applicator comprises a bladder filled with an acoustically transmissive medium.

3. The apparatus of claim 1 wherein the acoustically transmissive medium comprises a liquid.

4. The apparatus of claim 3 wherein the liquid is water.

5. The apparatus of claim 1 wherein the ultrasonic transducer is adapted to detect a second ultrasonic wave which is a Doppler shifted transformation of the first ultrasonic wave.

6. The apparatus of claim 1 wherein the pressure applicator is adapted for placement against a fontanelle on the neonatal cranium.

7. A method for ultrasonically evaluating an in vivo pressure, the method comprising the steps of:

transmitting a first ultrasonic wave into the target region;

applying a pressure applicator filled with an acoustically transmissive medium to the target region, thereby developing an external pressure in the target region;

detecting a second ultrasonic wave, the second ultrasonic wave generated by an interaction between the first ultrasonic wave and the target region;

measuring the applied external pressure, thereby generating an external pressure measurement;

calculating the in vivo pressure in the target region based on the first and second ultrasonic waves and on the external pressure measurement.

8. The method of claim 7 wherein the step of applying an external pressure to the target region comprises the step of placing a bladder against the target region, the bladder being filled with an acoustically transmissive medium.

9. The method of claim 8 wherein the step of measuring the applied external pressure comprises the step of providing a transducer coupled to the bladder.

10. The method according to claim 7 wherein the acoustically transmissive medium is a liquid.

11. The method according to claim 10 wherein the liquid is water.

12. The method according to claim 7 wherein the step of detecting a second ultrasonic wave comprises the step of detecting a Doppler shifted transformation of the first ultrasonic wave.

13. The method according to claim 7 further comprising the step of selecting the target region to be a neonatal cranium and the step of measuring the applied external pressure includes the step of placing the pressure applicator against a fontanelle on the cranium.

15. The applicator of claim 14 wherein the applicator further comprises a pressure transducer coupled to the bladder to provide a measurement of pressure applied by the contact surface.

16. The applicator of claim 14 wherein the applicator further comprises a pressure regulator for regulating the pressure applied by the bladder.

14. A pressure applicator for coupling to an ultrasonic probe, the pressure applicator comprising:

a bladder containing an acoustically transmissive medium, the bladder having a contact surface for exerting an applied pressure against a target region, and a side wall;

a housing enclosing at least a portion of the bladder to provide support for the bladder; and

for coupling the bladder to an ultrasonic probe, thereby permitting ultrasonic waves to propagate through the bladder between the ultrasonic probe and the target region.