WO1995023555A1

WO1995023555A1 - Display of vessels encoded by features of flow measured by ultrasound

Info

Publication number: WO1995023555A1
Application number: PCT/AU1995/000108
Authority: WO
Inventors: Robert Wyatt Gill; Thanasis Loupas; George Kossoff
Original assignee: Commonwealth Scientific And Industrial Research Organisation - (Division Of Radiophysics)
Priority date: 1994-03-04
Filing date: 1995-03-03
Publication date: 1995-09-08
Also published as: AUPM424694A0

Abstract

A method of displaying vessel(s). The method comprising measuring the flow in the vessel(s) or a part thereof by an ultrasonic transducer (2) to provide a set of measurements, which are processed (5, 6). The measured parameters are then compared by a classifier (9) with characteristic parameters (7, 8) to identify the measured vessel (1), which is then displayed (10).

Description

DISPLAY OF VESSELS ENCODED BY FEATURES OF FLOW MEASURED BY ULTRASOUND

TECHNICAL FIELD

This invention relates to the measurement of the flow of fluids in vessels by ultrasonic techniques, and the calculation of a set of features based on the spatial and temporal flow characteristic in such vessels, and to the display of such vessels, selected on the basis of their fluid flow features. The invention has particular medical application to identification of specific vessel(s), and/or the detection and/or diagnosis of the presence and/or extent of disease in specific vessels, or in the organs or body regions which are supplied with blood by the vessels.

BACKGROUND OF THE INVENTION

Measurement of various parameters of flow in liquids and gases by continuous and/or pulsed ultrasound is well established. The measured parameters include the displacement and velocity, and their spatial and temporal characteristics. Other parameters can be derived from these by calculation. These include, for example in the human circulation, the various pulsatility indices which describe the temporal nature of flow as a function of cardiac cycle. Acceleration, energy and power content, turbulence, shear rate, and Reynold's number are examples of other parameters which can be derived by calculation.

Colour Doppler imaging is an example of a well established technique used in diagnostic ultrasound. The method is based on the measurement of the component of the blood velocity along the direction of the ultrasonic beam. The value of this parameter or those that can be derived by calculation, or related parameters such as the amplitude or power of the blood flow signal is/are displayed in its/their appropriate spatial position using colour coding.

In the human body, most vessels have been shown to have characteristic flow patterns. For example, flow in veins is continuous, whilst that in arteries is pulsatile in response to the cardiac cycle. The pulsality index of flow in many arteries is specific to the vessel. For example, the pulsality index in renal arteries differs from that in the hepatic and splenic arteries. Changes in flow pattern can occur with factors such as respiration, breath holding, exercise and feeding. Characteristic changes also occur with disease. All of these are used either individually or collectively to identify specific vessels and to detect and/or diagnose the presence and/or extent of disease.

SUMMARY OF THE INVENTION

The present invention seeks to provide a method/apparatus for calculating a set of features based on the spatial and temporal characteristics of flow in blood vessels.

The present invention seeks to provide a method/apparatus for identifying vessels or specific disease states on the basis of features of fluid flow.

The present invention also seeks to provide a method and apparatus for displaying, under user control, vessels in which the flow has a selected range of features.

In one broad form, the present invention provides a method of displaying at least part of at least one vessel, comprising the steps of: measuring the flow in said vessel(s) by ultrasonic techniques to provide a set of measurements; deriving from said measurements, a set of derived parameters pertaining to said flow in said vessel(s); selecting said vessel(s) or disease state(s) thereof to be displayed; identifying from a predetermined analysis, which of said set of characteristic parameters are typical of said vessel(s) or disease state(s) thereof to be displayed; and, displaying said vessel(s) determined to have derived parameters corresponding to said characteristic parameters.

Preferably, in said measuring step, said set of measurements includes the displacement and/or velocity, and/or spatial and/or temporal characteristics thereof. Also preferably, said derived parameters include various pulsality indices - which describe the temporal nature of flow as a function of cardiac cycle acceleration, energy and/or power content, turbulence, shear rate, and/or Reynolds number, etc.

Preferably, the method of the present invention further comprises the step of examining said displayed vessel to identify changes in flow pattern as a function of factors such as respiration, breath holding, exercise and/or feeding and/or detecting and/or diagnosing presence and/or extent of disease.

In alternatively preferred embodiments of the invention, in said displaying step, said display is in grey scale or in colour, on a cathode ray tube, or a television screen or the like.

Preferably, in said selecting/identifying steps, each selected vessel(s) or disease state(s) thereof is allocated a grey scale or colour code, e.g. red, blue, yellow, etc., such that, in said displaying step, the selected vessels or other features of the flow can be displayed in grey scale or colour coding.

In a further broad form, the present invention provides an apparatus for displaying at least part of at least one vessel comprising: an ultrasonic measuring device, to measure fluid flow in said vessel(s); microprocessor means to derive parameters from measurements detected by said ultrasonic measuring device, to receive data input from an operator, and to correlate said input data with said derived parameters from said measurements; and, display means to display selected vessel(s).

BRIEF DESCRIPTION OF THE DRAWING

The present invention will become more fully understood by the following detailed description of a preferred but non-limiting embodiment thereof, described in connection with the accompanying drawing, which identifies, in schematic form, the primary modules comprising the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

In the drawing, the main components and steps are illustrated. At least a part of at least one vessel to be measured, designated by the numeral 1 , is positioned proximal to a transducer 2, and an ultrasonic transmitter 3 operated to transmit ultrasonic radiation to the vessel 1. The transmitted signal undergoes alteration, including attenuation and reflection , depending upon the characteristics of the vessel 1 and the intervening tissues, the modified signal then being received by receiver 4. The measured signal, received by receiver 4, is then processed and compared with predetermined characteristic features of various vessels such that the vessel 1, or regions of it with specific disease states, being measured is identified, and displayed.

The figure illustrates preferred steps, whereby flow feature estimates 5 are determined and processed in a spatial and temporal flow feature processor 6 . Various characteristic parameters are stored in a vessel feature knowledge database 8, such that by appropriate correlation the various features selected by the user using the user interface

7 can be determined by a classifier 9 and then displayed 10.

In short, the invention calculates as set of features based on the spatial and temporal flow characteristics in blood vessels, identifies vessels or specific portions of vessels on the basis of various features of fluid flow through those vessels, and then displays, as selected, particular vessels or portions of vessels, in which the flow has a selected range of features.

For example, selection of vessels with non-pulsatile flow features results in the display of veins only. Alternatively, only arteries are portrayed if vessels with features of pulsatile flow are selected for display.

Specific vessels can be selected for display on the basis of their features. For example, the internal carotid artery can be selectively displayed in cross sectional or volumetric scans which exclude the external carotid artery, on the basis of selection of display of features in vessels in which the pulsality index is in the range found in internal carotid arteries - but outside those encountered in external carotid arteries. Other combinations of measured and/or calculated features can also be selected for display. This allows selective representation of multi-parametric features of flow. For example, portions of flow in vessels within the required range of shear rate and/or of Reynold's number can be displayed.

The following table lists, by way of example only, typical features of flow pattern which may be selected to identify particular vessels.

flow pattern vessel identification (selection criteria) continuous flow veins pulsatile flow arteries pulsatile flow with peak systolic velocity above v, and end disatolic velocity above v₂ renal artery pulsatility index above P, internal carotid but below P₂ artery shear rate above S, artery with significant stenotic disease Reynolds number above R, arteries with potential for turbulent flow

The display can be in grey scale or in colour. Different colours can be selected to image vessels specified by their features. As an example, in the liver, flow in the hepatic artery, hepatic veins and portal vein and its branches, differs on the basis of the pulsatility index and respiration dependence. On the basis of selection of these features, these vessels can be identified in cross-sectional and volumetric scans and selectively displayed by different colours. For example, flow in the hepatic artery can be displayed in red, that in the hepatic vein in blue, while that in the portal vein and its branches is portrayed in yellow. This allows identification of these vessels in the scans and appreciation of effects of disease processes in the vessels and effects on them such as displacement caused by adjacent disease processes. Alternatively, once vessels have been selected on the basis of their features of flow, the selected features or some other set of features of flow can be displayed by grey scale or colour coding.

The present invention, as hereinbefore described, will be understood, by persons skilled in the art, to have a wide variety of applications for use, such as, but not limited to, the individual and/or collective identification of specific vessels and the detection and/or diagnosis of the existence and/or extent of disease.

It will be understood by the persons skilled in the art that there are various method and apparatus components for implementing/fulfilling the invention. All such apparatus capable of fulfilling the basic aims of the invention should be considered to fall within the scope of the invention. It should therefore be noted that although a specific implementation and application of the present invention has been described hereinbefore, the present invention is not limited to that implementation and application. Variations of and modifications to the present invention may be made without departing from the spirit and scope of the present inventive concept.

Claims

THE CLAIMS

1. A method of displaying at least part of at least one vessel, comprising the steps of: measuring the flow in said vessel(s) by ultrasonic techniques to provide a set of measurements; deriving from said measurements, a set of derived parameters pertaining to said flow in said vessel(s); producing images based on the said derived parameters characterising the spatial and temporal flow pattern in said vessel; selecting said vessel(s) or disease state(s) thereof to be displayed; identifying from a predetermined analysis, which of said set of characteristic parameters are typical of said vessel(s) or disease state(s) thereof to be displayed; and, displaying said vessel(s) determined to have derived parameters corresponding to said characteristic parameters.

2. A method as claimed in claim 1, wherein in said measuring step, said set of measurements includes the displacement and/or velocity, and/or spatial and/or temporal characteristics thereof.

3. A method as claimed in claim 1 or 2, wherein said derived parameters include various indices - which describe the temporal and spatial nature of flow as a function of cardiac cycle-pulsality acceleration, energy and/or power content, turbulence, shear rate, and/or Reynolds number, etc.

4. A method as claimed in any one of claims 1 to 3, wherein after said displaying step said method further comprises the step of: examining said displayed vessel to identify changes in flow pattern as a function factors such as respiration, breath holding, exercise and/or feeding and/or detect and/or diagnose presence and/or extent of disease.

5. A method as claimed in any one of claims 1 to 4, wherein in said displaying step, said display is in grey scale or in colour, on a cathode ray tube, or a television screen or the like.

6. A method as claimed in claim 5, wherein in said selecting/identifying steps, each selected vessel(s) or disease state(s) thereof is allocated a grey scale or colour code, e.g. red, blue, yellow, etc., such that, in said displaying step, the selected vessel(s) or other features of the flow can be displayed in grey scale or colour coding.

7. An apparatus for displaying at least part of one or more vessel(s) comprising: an ultrasonic measuring device, to measure fluid flow in said vessel(s); microprocessor means to derive parameters from measurements detected by said ultrasonic measuring device, to receive data input from an operator, and to correlate said input data with said derived parameters from said measurements; and, display means to display selected vessel(s).

8. A method of displaying at least part of at least one vessel(s), substantially as herein described.

9. An apparatus for displaying at least part of one or more vessel(s), substantially as herein described with reference to the accompanying drawings.