Ultrasonic method and apparaus for determination of vessel location and size

• US 5,280,787 A
• Filed: 09/16/1992
• Issued: 01/25/1994
• Est. Priority Date: 01/25/1990
• Status: Expired due to Fees

• Current Assignee: Commonwealth Scientific & Industrial Research Organisation (Commonwealth Of Australia As Represented By Department Of Industry, Innovation, Climate Change, Science, Research And Tertiary Education)
• Original Assignee: Commonwealth Scientific & Industrial Research Organisation (Commonwealth Of Australia As Represented By Department Of Industry, Innovation, Climate Change, Science, Research And Tertiary Education)
• Inventors: Gill, Robert W., Dadd, Michael J., Wilson, Laurence S.
• Primary Examiner(s): JAWORSKI, FRANCIS J
• Application Number:
  US07/915,841
• Time in Patent Office: 496 Days
• Field of Search: 128/660.04-660.05, 128/662.07-661.10, 128/662.04, 128/662.06
• US Class Current: 600/456
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/489 Blood vessels
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 8/06 Measuring blood flow measuring volume flow in general G01F, e.g. G01F1/66, G01F1/72; measuring speed of fluids in general G01P5/00
• CPC Class Codes: A61B 8/0858 involving measuring tissue layers, e.g. skin, interfaces
• CPC Class Codes: G01S 15/8979 Combined Doppler and pulse-echo imaging systems
• CPC Class Codes: G01S 7/5206 Two-dimensional coordinated display of distance and direction; B-scan display
• CPC Class Codes: G01S 7/52073 Production of cursor lines, markers or indicia by electronic means

Abstract

An improved technique for establishing the position, dimensions and orientation of a vessel which is essentially free of internal acoustic discontinuities involves scanning the vessel with a beam of ultrasonic energy and, from the ultrasonic echoes received in the A-mode lines of sight of the ultrasonic beam, establishing a B-mode image of the vessel. An angle marker, in the form of a short line segment, is established, using the B-mode image, on or near a straight axis of the vessel. The length of the angle marker is divided into a number of sub-sectors, each of which receives approximately the same number of A-mode lines of sight of the ultrasonic beam. An average A-mode signal is obtained for each sub-sector. Comparison of the average A-mode signals provides information about the orientation of the angle marker relative to the axis of the vessel. Combining the average A-mode signals to obtain a composite signal and performing edge-detection analysis of the composite signal enables the edges of the vessel to be established with precision, and the diameter of the vessel to be determined accurately. A single computer can programmed to perform the analysis and re-position the angle markers (if necessary) on to the axis of the vessel. Using information obtained from this technique, accurate values of the flow rate of a fluid moving within the vessel can be obtained when Doppler frequency shift measurements are made.

Claims

1. A method of establishing the dimensions and orientation of a vessel which, when subjected to ultrasonic echoscopy examination, is found to be essentially free of substantial internal acoustic discontinuities, said vessel having an axis which is straight in least part of the vessel, said method comprising the steps of

(a) obtaining a B-mode ultrasonic echogram image of said vessel or the part thereof in which said axis is straight from a number of A-mode ultrasonic images, each corresponding to a respective A-mode line of sight of a beam of ultrasonic energy which is scanned over said vessel or said part thereof;

(b) establishing an angle marker in the form of a short line segment within or close to the B-mode image of said vessel or said part thereof;

(c) establishing a plurality of adjacent sub-sectors within the B-mode echogram image of said vessel or part thereof;

each of said sub-sectors being intersected by said angle marker;

each sub-sector receiving substantially the same number of adjacent A-mode lines of sight of said scanning beam;

(d) obtaining an average video-detected A-mode signal for each of said sub-sectors,

(e) performing a comparison of said average A-mode signals of the sub-sectors and determining from said comparison the difference between the orientation of the axis of said vessel and said angle marker and the orientation of said axis of said vessel;

(f) combining said average A-mode signals to obtain a composite A-mode signal for said vessel or part thereof; and

(g) performing edge-detection analysis on said composite A-mode signal, to obtain a value of the diameter of said vessel or part thereof.

2. A method as defined in claim 1, in which the step of performing edge-detection analysis includes the sub-steps of

(i) smoothing the waveform of the composite A-mode signal and identifying a minimum value therein which corresponds to the position of the axis of said vessel;

(ii) differentiating the smoothed waveform of the composite A-mode signal;

(iii) identifying a minimum in the differentiated waveform, which occurs between the generation point of the beam of ultrasonic energy and the axis of said vessel and which corresponds to one wall of the vessel and identifying a maximum in the differentiated waveform, farther from generation point of the beam of ultrasonic energy than the axis of said vessel, which corresponds to the other wall of the vessel; and

(iv) adopting the distance between the minimum identified in step (iii) and the maximum identified in step (iii) as the diameter of the vessel.

3. A method as defined in claim 2, including the additional step of repeating steps (a) to (g) and using the information obtained from step (e) of the last preceding sequence of steps (a) to (g) to perform the step of establishing the angle marker so that the angle marker is positioned substantially on said axis of said vessel.

4. A method as defined in claim 3, in which, when step (e) provides information showing that the B-mode image of said vessel indicates that said vessel is non-linearly tapered in diameter over at least one of said sub-sectors, in the next repeat of said sequence of steps (a) to (g), the establishment of the angle marker is effected so that the angle marker is effectively moved generally lengthwise of its last preceding position.

5. A method as defined in claim 4, in which said B-mode image is displayed on a screen of a television set or cathode ray oscilloscope.

6. A method as defined in claim 4, including the additional step of performing a Doppler frequency shift measurement in respect of fluid flowing through said vessel, and using the established orientation and cross-sectional dimensions of said vessel to calculate the flow rate of said fluid.

7. A method as defined in claim 1 or claim 2, including the additional step of repeating steps (a) to (g) and using the information obtained from step (e) of the last preceding sequence of steps (a) to (g) to perform the step of establishing the angle marker so that the angle marker is positioned substantially on said axis of said vessel.

8. A method as defined in claim 7, in which, when step (e) provides information showing that the B-mode image of said vessel indicates that said vessel is non-linearly tapered in diameter over at least one of said sub-sectors, in the next repeat of said sequence of steps (a) to (g), the establishment of the angle marker is effected so that the angle marker is effectively moved generally lengthwise of its last preceding position.

9. A method as defined in claim 1, in which said B-mode image is displayed on a screen of a television set or cathode ray oscilloscope.

10. A method as defined in claim 1, including the additional step of performing a Doppler frequency shift measurement in respect of fluid flowing through said vessel, and using the established orientation and cross-sectional dimensions of said vessel to calculate the flow rate of said fluid.

11. Apparatus for establishing the orientation and cross-sectional dimensions of a vessel having an axis, said apparatus comprising:

(a) conventional apparatus for generating a beam of ultrasonic energy and scanning said beam over at least part of said vessel, to obtain a B-mode ultrasonic echogram image of said vessel or part thereof from a number of A-mode ultrasonic images, each corresponding to a respective A-mode line of sight of said beam;

(b) operator-activated means for establishing an angle marker in the form of a short line segment within or close to the B-mode image of said vessel or part thereof;

(c) accumulation means for accumulating echoes relating to respective sub-sectors of a plurality of sub-sectors of said B-mode image, said sub-sectors (i) being adjacent to each other, (ii) being intersected by said angle marker, and (iii) containing substantially equal numbers of adjacent A-mode lines of sight of said scanning beam;

(d) averaging means for producing a respective average A-mode signal for each of said sub-sectors;

(e) comparison means for comparing said average A-mode signals and for obtaining differences between the average A-mode signals, to enable the orientation of said axis relative to said angle marker to be computed;

(f) combining means for combining said average A-mode signals to produce a composite A-mode signal; and

(g) analytical means to perform edge analysis on said composite A-mode signal and to obtain therefrom a value of the diameter of said vessel or part thereof.

12. Apparatus as defined in claim 11, in which said accumulation means, averaging means, comparison means, combining means and analytical means are constituted by a single computer programmed to sequentially perform the functions of said accumulation means, averaging means, comparison means, combining means and analytical means.

13. Apparatus as defined in claim 12, including Doppler frequency shift measuring means for measuring the Doppler frequency shift of ultrasonic signals due to the flow of liquid through said vessel.

14. Apparatus as defined in claim 11, including a screen for display of said B-mode echogram image.

15. Apparatus as defined in claim 11, including Doppler frequency shift measuring means for measuring the Doppler frequency shift of ultrasonic signals due to the flow of liquid through said vessel.