1995-01-11
1996-11-19
Manuel, George
Surgery
Truss
Pad
A61B 800
Patent
active
055752896
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the measurement of parameters of fluid flow in a conduit within a human or animal body. It has more specific application to flowmeters of Doppler ultrasound form, and in a particular application is for use in monitoring a patient's blood flow.
Flowmeters of the Doppler ultrasound type are routinely used in medical practice for measuring and monitoring blood flow in patients. These meters are usually designed for transcutaneous application, but some have been developed for catheterised application into a blood vessel of interest. A device suitable for invasive ultrasonic investigation is described in U.S. Pat. No. 4,546,771. This device comprises a needle with a sharp point for insertion into a human body, the needle containing transducer means and beam directing means for directing acoustical beams radially from the needle to a point outside of the needle.
Meters known from the prior art are often limited to the provision of measures only of blood velocity, whereas the medical community frequently has an interest in knowing the blood volume flow rate in the relevant vessel. This interest extends particularly to the case in which the vessel is the ascending aorta because the rate is then an effectively direct indication of cardiac output. Blood velocity may be measured using the Doppler ultrasound method, and blood volume flow rate is provided simply as the product of velocity and the vessel cross-sectional area. The velocity used in such a calculation is a weighted average velocity value to take into account the velocity distribution across the vessel diameter. A problem remains in attaining an indication of the area in question, and in the case of the interest in cardiac output, area is often estimated for a given patient by way of a quite separate imaging procedure. Margins of error for such measurements can be as high as 20%. Access for non-invasive ultrasound monitoring equipment to the aorta presents particular problems, as the sternum of the body provides an effective screen to ultrasound signals. Access is possible via the suprasternal notch, but this space is very limited in size.
It is an object of the present invention to improve this situation and to this end there is provided, according to one aspect of the invention, a medical probe suitable for use in measuring parameters of fluid flow in a conduit within a human or animal body, the probe comprising:
a hollow housing having an ultrasound transparent wall part;
transducer means mounted within the housing and operable to emit and detect ultrasound beam signals along a path; and
reflecting means within the housing and disposed in said path to divert the beam through an angle so as to emerge from the housing through an exit portion of the ultrasound transparent wall part;
wherein the external dimension of the housing transverse to said path reduces substantially from the region of the transducer means to the region of the exit portion, characterised in that the reflecting means are mounted for rotation in the narrowed exit portion region.
Preferably, the probe has a distal part with a smoothly contoured external shaping to permit safe non-invasive use.
The type of transducer used in a scanning ultrasound device is likely to be of relatively large size, as a narrow ultrasound beam is required, necessitating a relatively large crystal. However the very restricted access provided by the suprasternal notch renders it very difficult to introduce a probe with a large transducer directly into the notch. The particular advantage of the invention is that the part of the probe where the exit section is situated can be located within the notch, and by use of a rotatable reflecting means the ultrasound beam can be scanned whilst the transducer means itself remains at some distance from the access point.
Mounting the reflecting means in the region of the exit portion allows the use of a small rotating reflector in the tip of the probe.
Preferably, the drive means to rotate the reflecting means is mounted within the housing. Th
REFERENCES:
patent: 4246791 (1981-01-01), Glenn
patent: 4313444 (1982-02-01), Glenn
patent: 4317370 (1982-03-01), Glenn
patent: 4509526 (1985-04-01), Barnes et al.
patent: 4546771 (1985-10-01), Eggleton et al.
patent: 4757823 (1988-07-01), Hofmeister et al.
patent: 5054492 (1991-10-01), Scribner et al.
patent: 5085220 (1992-02-01), Nudell et al.
British Technology Group Limited
Manuel George
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