Method for noninvasive intracranial pressure measurement

• US 6,117,089 A
• Filed: 04/25/1995
• Issued: 09/12/2000
• Est. Priority Date: 04/25/1995
• Status: Expired due to Fees

• Current Assignee: Los Alamos National Security LLC (Government of the United States of America)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Sinha, Dipen N.
• Primary Examiner(s): O'Connor, Cary
• Assistant Examiner(s): WINGOOD, PAMELA LYNN
• Application Number:
  US08/428,940
• Time in Patent Office: 1,967 Days
• Field of Search: 128/660.02, 128/660.03, 128/748, 128/774, 73/772, 73/716
• US Class Current: 600/561
• CPC Class Codes: A61B 5/031 Intracranial pressure

Abstract

An ultrasonic-based method for continuous, noninvasive intracranial pressure (ICP) measurement and monitoring is described. The stress level in the skull bone is affected by pressure. This also changes the interfacial conditions between the dura matter and the skull bone. Standing waves may be set up in the skull bone and the layers in contact with the bone. At specific frequencies, there are resonance peaks in the response of the skull which can be readily detected by sweeping the excitation frequency on an excitation transducer in contact with a subject'"'"'s head, while monitoring the standing wave characteristics from the signal received on a second, receiving transducer similarly in contact with the subject'"'"'s head. At a chosen frequency, the phase difference between the excitation signal and the received signal can be determined. This difference can be related to the intracranial pressure and changes therein.

Claims

1. A method for measuring changes in intracranial pressure of a subject, which comprises the steps of:

a. applying an ultrasonic, oscillatory excitation to the head of the subject, thereby generating a standing-wave in the skull bone of the subject;

b. detecting the resulting vibration in the skull bone at a chosen distance from the region of generating the standing-wave pattern;

c. choosing a frequency for said step of ultrasonic, oscillatory excitation such that the detected vibration corresponds to a resonance in the skull bone; and

d. measuring the phase difference between the detected resonant vibration and the applied ultrasonic excitation, whereby changes in the intracranial pressure may be related to changes in the measured phase difference.

2. The method for measuring changes in intracranial pressure of a subject as described in claim 1, wherein said steps of applying ultrasonic, oscillatory excitation to the head of the subject, and detecting the resulting vibrations in the skull bone of the subject are performed using piezoelectric transducers.

3. The method for measuring changes in intracranial pressure of a subject as described in claim 2, wherein the transducers are contacted to the subject'"'"'s head using a coupling gel.

4. The method for measuring changes in intracranial pressure of a subject as described in claim 1, wherein said step of choosing an ultrasonic frequency such that the detected vibrations have a chosen amplitude is accomplished by choosing the region of maximum amplitude of a resonance in the skull bone.