Systems and methods for determining intracranial pressure non-invasively and acoustic transducer assemblies for use in such systems

Abstract

Systems and methods for determining ICP based on parameters that can be measured using non-invasive or minimally invasive techniques are provided. Systems for acquiring acoustic data from a desired target site in a subject's body using various types of acoustic source and detector elements are also provided, including single use acoustic source / detector combinations are also provided. Acoustic arrays for use with these systems may include multiple capacitive micro-machined ultrasound transducer (cMUT) elements, and may include a combination of different types of acoustic arrays. Methods of targeting localized sites within a broad target area based on acoustic data having various properties are also disclosed.

Description

REFERENCE TO PRIORITY APPLICATION[0001]This application is a divisional application of U.S. patent application Ser. No. 10 / 861,197, filed Jun. 3, 2004, which claims priority to U.S. Provisional Application No. 60 / 475,803 filed Jun. 3, 2003 and U.S. Provisional Application No. 60 / 508,836 filed Oct. 1, 2003. U.S. patent application Ser. No. 10 / 861,197 is also a continuation-in-part of U.S. patent application Ser. No. 09 / 995,897, filed Nov. 28, 2001, issued as U.S. Pat. No. 6,875,176 on Apr. 4, 2005 and which claims priority to U.S. Provisional Application No. 60 / 253,959, filed Nov. 28, 2000. These patent applications are incorporated herein by reference in their entireties.GOVERNMENT SUPPORT AND RIGHTS[0002]Subject matter disclosed in this application was supported by federally sponsored research and development funding. The U.S. Government may have certain rights in inventions disclosed in this application as provided for by the terms of Grant No. K25NS02234-02 awarded by the Nationa...

AI Technical Summary

Benefits of technology

The present invention provides methods and systems for accurately assessing and monitoring intracranial pressure (ICP) based on non-invasive or minimally invasive parameters such as acoustic scatter or flow velocity in cerebral blood vessels or arterial blood pressure. These methods and systems can provide accurate assessments of ICP in real-time or near-real-time, which can aid in the diagnosis and monitoring of various medical conditions such as brain injuries or intracranial hemorrhages. The invention also takes into account other physiological properties of blood and tissue, such as tissue stiffness or displacement, to determine ICP. The methods and systems use ultrasound techniques, such as TCD or Doppler, to measure these parameters. Overall, the invention provides a non-invasive and reliable way to assess and monitor ICP.

Problems solved by technology

Under some conditions, elevated intracranial pressures may cause the brain to be mechanically compressed, and to herniate.

The most common cause of elevated intracranial pressure is head trauma.

Changes in intracranial pressure, particularly elevated intracranial pressure, are very serious and may be life threatening.

All of these methods and systems are invasive.

The subarachnoid bolt / screw technique requires minimal penetration of the brain, it has a relatively low risk of infection, and it provides a direct pressure measurement, but it does require penetration of an intact skull and it poorly drains CSF.

The ventriculostomy catheter technique provides CSF drainage and sampling and it provides a direct measurement of intracranial pressure, but the risks of infection, intracerebral bleeding and edema along the cannula track are significant, and it requires transducer repositioning with head movement.

All of these conventional techniques require invasive procedures and none is well suited to long term monitoring of intracranial pressure on a regular basis.

Moreover, these procedures can only be performed in hospitals staffed by qualified neurosurgeons.

The hypothesis that ICP is altered in microgravity environments is difficult to test, however, as a result of the invasive nature of conventional ICP measurement techniques.

The model of Schmidt et al. was able to realistically simulate ICP curves in a subset of patients, although not to a clinically useful degree.

While this mode of measurement is simple and inexpensive to perform, it does not provide the most accurate measure of ABP, and it is susceptible to artifacts resulting from the condition of arterial wall, the size of the patient, the hemodynamic status of the patient, and autonomic tone of the vascular smooth muscle.

Additionally, repeated cuff measurements of ABP result in falsely elevated readings of ABP, due to vasoconstriction of the arterial wall.

While such catheters are very reliable and provide the most accurate measure of ABP, they require placement by trained medical personnel, usually physicians, and they require bulky, sophisticated, fragile, sterile instrumentation.

Additionally, there is a risk of permanent arterial injury causing ischemic events when these catheters are placed.

As a result, these invasive monitors are only used in hospital settings and for patients who are critically ill or are undergoing operative procedures.

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