Elsevier

Ultrasonics

Volume 40, Issues 1–8, May 2002, Pages 829-833
Ultrasonics

Investigation of intracranial media ultrasonic monitoring model

https://doi.org/10.1016/S0041-624X(02)00216-0Get rights and content

Abstract

The objectives are to investigate the peculiarities of the ultrasound pulse propagation through human extra/intracranial media by mathematical simulation and to confirm the simulation results experimentally by proving the suitability of the ultrasonic time-of-flight measurement method for human intracranial media (IM) physiological non-invasive monitoring. The mathematical model of ultrasound pulse propagation through the human extra/intracranial media is described. The simulation of various physiological phenomena were performed to determine the relationship between the characteristics of the transmitted ultrasound pulse through the human head and the acoustic properties of the IM. It is shown that non-invasive monitoring of the IM acoustic properties is possible by measuring the changes of the ultrasonic signal time-of-flight and the oscillation period. The influence made by variations in acoustic parameters of the external tissue/skull bones on the non-invasive measurement data is investigated and methods of compensation of that influence are presented. The models were applied for developing of a new non-invasive sonographic intracranial pressure (ICP) monitor (Vittamed). Comparative studies of this monitor with the invasive ICP monitor (Camino) have shown the possibility of achieving clinically acceptable accuracy of the long term non-invasive ICP monitoring of head injured patients in intensive care units.

Introduction

Various methods of non-invasive human intracranial pressure (ICP) measurement have appeared since 1980. However, the need for new non-invasive ICP monitoring technologies that are reliable and suitable for clinical application still exists [1]. The main problem is to find suitable parameter of human cerebrospinal system which would be a stable and repeatable function related to the ICP or cerebral perfusion pressure (CPP). In addition, this function need to be independent of factors such as arterial blood pressure (ABP) or cerebral blood flow autoregulation.

Recently, a new method [2] for the non-invasive measurement of intracranial volume or pressure has been created that is based on the ultrasonic time-of-flight measurement technique. It is capable of measuring the acoustic properties of the intracranial media (IM) such as ultrasound speed and ultrasound attenuation. The aim of this study is to answer the following questions:

  • what is the relationship between the characteristics of the ultrasonic signal (time-of-flight, period of oscillation) measured non-invasively by the time-of-flight technique and the acoustic properties of the IM?

  • how does it reflect the ICP changes or physiological state of the human brain?

  • what is the influence that the skull bones (SB)/external tissues (ET) make on the time-of-flight measurement results and how to minimise that influence?

Section snippets

Theoretical model

The idea of measuring the changes of intracranial component volumes non-invasively is based on the transmission of a broadband ultrasonic signal through the human head and monitoring such signal parameters as the time-of-flight and the oscillation period [2], [3], [4]. As all intracranial components (brain tissue, cerebrospinal fluid (CSF), blood) have different acoustic properties (ultrasound speed, frequency dependent attenuation), changes of their content inside the acoustic path will

Influence of skull bones and external tissues

The influence of SB and ET must be taken into account while performing non-invasive transintracranial ultrasonic measurements. The variation of ET acoustic properties caused by the hemodynamics or swelling in these tissues influences the change of measurement results, separately to the state of the IM.

The methods of non-invasive measuring of the acoustic properties of IM with a compensation of SB/ET influence are shown in Fig. 3. Signal delays in the SB/ET are evaluated by measuring the

Results

A new non-invasive ultrasonic Vittamed monitor based on the models of the ultrasound speed in cerebral parenchymal acoustic path measurement was designed and tested in an intensive care unit (ICU). The example of simultaneous long term (more than 3 h) ICP monitoring with a new non-invasive Vittamed monitor and with a Camino V420 invasive monitor for a head injury patient in the ICU is shown in Fig. 4. The non-invasive ICP data are calculated from the time-of-flight measured data using the

Conclusions

The investigation of the human IM physiological monitoring model allows us to develop the concepts for non-invasive ICP/CPP measurements:

  • The intraventricular or supraventricular parenchymal acoustic path which crosses the human head is used for non-invasive measurements. The parenchymal arterioles that are located in this path are responsible for cerebral blood flow autoregulation [12]. The ultrasound speed inside the parenchymal acoustic path mainly depends on the blood volume inside this path.

References (12)

  • Part B: Description of Scientific/Technological Objectives and Work Plan, Proposal for Research and Technological...
  • A. Ragauskas, G. Daubaris, A method and apparatus for non-invasively deriving and indicating of dynamic characteristics...
  • V Petkus et al.

    Mathematical modeling of ultrasonic signal transmission through the human skull and brain

    Matavimai

    (2000)
  • V Petkus et al.

    Theoretical model of intracranial media ultrasonic attenuation measurement method

    Ultragarsas

    (2000)
  • W.J. Thoman, S. Lampotang, D. Gravenstein, J. Van der Aa, A computer model of intracranial dynamics, Proc. IEEE/EMBS,...
  • K Hynynen et al.

    Trans-skull ultrasound therapy: The feasibility of using image-derived skull thickness information to correct the phase distortion

    IEEE Ulltrason. Ferroelec. Freq. Cont.

    (1999)
There are more references available in the full text version of this article.

Cited by (43)

  • Non-invasive estimation of static and pulsatile intracranial pressure from transcranial acoustic signals

    2016, Medical Engineering and Physics
    Citation Excerpt :

    The use of TCA signals for estimation of nICP belongs to the methods utilizing the properties of the intracranial structures to estimate nICP, as opposed to the methods utilizing properties of extra-cranial organs connected to the intracranial compartment [3]. Other methods relying on the properties of the intracranial contents include ultrasound time of flight, which assumes that changes in ICP cause change in the physical dimensions and acoustic properties of the cranial content [12]. Transcranial Doppler ultrasonography utilizes the Doppler effect to measure the velocity of blood flow through the intracranial vessels and estimates the ICP based on these measurements [13].

  • Intracranial Hypertension and Brain Monitoring

    2011, Pediatric Critical Care: Expert Consult Premium Edition
  • Blood-Brain Barrier (BBB) Disruption Using a Diagnostic Ultrasound Scanner and Definity® in Mice

    2009, Ultrasound in Medicine and Biology
    Citation Excerpt :

    With a higher attenuation and speed of sound than tissue, variable thicknesses in the skull lead to changes in the pressure delivered in vivo due to increased attenuation and phase aberration (Tanter et al. 1998). Similarly, the fluid in the ventricles will also impact the pressure delivered due to a lower attenuation compared with tissue (Petkus et al. 2002). The doses of Definity (Bristol-Myers Squibb Medical Imaging.

View all citing articles on Scopus
View full text