Method for ultrasonic imaging, particularly of moving bodies, such as surgical utensils, tissues, flows, or the like

• US 6,652,460 B2
• Filed: 05/04/2001
• Issued: 11/25/2003
• Est. Priority Date: 05/05/2000
• Status: Expired due to Term

• Current Assignee: Esaote SpA
• Original Assignee: Esaote SpA
• Inventors: Merlanti, Marco, Fabiano, Mauro, Pellegretti, Paolo
• Primary Examiner(s): Manuel, George
• Assistant Examiner(s): Jung, William C.
• Application Number:
  US09/850,627
• Publication Number:
  US 20010044580A1
• Time in Patent Office: 935 Days
• Field of Search: 600/437-472
• US Class Current: 600/443
• 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 8/08 Detecting organic movements or changes, e.g. tumours, cysts, swellings A61B8/02 - A61B8/06 take precedence
• CPC Class Codes: A61B 8/0833 involving detecting or locating foreign bodies or organic structures
• CPC Class Codes: A61B 8/0841 for locating instruments
• CPC Class Codes: A61B 8/13 Tomography A61B8/10, A61B8/12 take precedence; tomography for radiation diagnosis A61B6/02
• CPC Class Codes: A61B 8/488 involving Doppler signals
• CPC Class Codes: G01S 15/8909 using a static transducer configuration
• CPC Class Codes: G01S 5/30 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: G01S 7/52026 Extracting wanted echo signals Doppler systems G01S15/50; Doppler short range imaging systems G01S15/8979
• CPC Class Codes: G01S 7/52036 using analysis of echo signal for target characterisation

Abstract

A method for ultrasonic imaging, particularly of moving bodies, such as surgical utensils, tissues, flows, or the like, which includes the following steps:—Periodically emitting ultrasonic pulses along a predetermined view line and with a predetermined repetition rate through one or more transducers;—Receiving the echoes produced by the body and/or the tissues or flows and transforming them into echo signals;—Processing the echo signals for extracting information therefrom and for generating an image based on such information. According the invention, the following steps are additionally provided:—determining a real time vector difference between the echo signals of two pulses successively emitted at predetermined time intervals;—using said difference signal as an information signal for ultrasonic imaging.

Claims

1. A method for ultrasonic imaging, particularly of moving bodies, comprising the following steps:

periodically emitting ultrasonic pulses along a predetermined view line and with a predetermined repetition rate through one or more transducers;

receiving echoes produced by first and second objects and transforming them into echo signals;

processing the echo signals for extracting information therefrom and for generating an image based on such information,

characterized by the following additional steps;

determining real time vector difference signals between echo signals of two pulses successively emitted at predetermined time intervals from said first and second objects;

applying a threshold level to said difference signals to form first and second signal level regions such that the difference signal from said one of said objects substantially falls within said first region and said difference signal from said other object substantially falls within said second region; and

attenuating the level of said echo signals from said object whose difference signal substantially falls within said first region in order to enhance the image of said other object.

2. A method as claimed in claim 1, characterized in that a non linear filtering of the difference signal between two successive echo signals is performed to retain for reconstructing the image high intensity components of the difference signal or low intensity component of the difference signal for alternatively or parallel neutralize signals due to non echogenic regions and image bodies, tissues or structures having echogenic or hyperechogenic responses and executing micromovements or displacements relating to the probe or neutralize signal flashes generated by relative micromovements between the probe and the echogenic or hyperechogenic tissues surrounding non echogenic bodies like physiologic flows.

3. A method as claim in claim 2, characterized in that the portions of the difference signal between two successive echo signals exceeding the maximum threshold are set to zero or attenuated below a predetermined value or according to a predetermined attenuation factor, whereas the portions of the signal below the maximum threshold are retained and transformed into images.

4. A method as claimed in claim 2, characterized in that the portions of the difference signal between two successive echo signals below the maximum threshold are set to zero or attenuated below a predetermined value or according to a predetermined attenuation factor, whereas the portions of the signal above the maximum threshold are retained and transformed into images.

5. A method as claimed in claim 2, characterized in that it provides partial subtraction of the second echo signal from the first echo signal, by appropriate weighting, to attenuate without completely suppressing the contribution to the difference signal by stationary tissues, so that a combination of the flow image with an attenuated image of the tissues surrounding the flow may be obtained.

6. A method as claimed in claim 1 or 2, characterized in that a maximum and/or minimum threshold is set for filtering the difference signal between two successive echo signals, the difference signal part above and or below and or within said thresholds being used for reconstructing the image, while the other part of the signal is at least attenuated or set to zero.

7. A method as claimed in claim 6, characterized in that filtering is performed by using two thresholds, a minimum and a maximum threshold, on echo signals being determined, with the B-Mode method, as signal levels for stationary tissues and flow and/or for echogenic or hyperechogenic materials executing micromovements or displacements relatively to the probe.

8. A method as claimed in claim 1, characterized in that a minimum threshold is also defined for the difference signal between two successive echoes, below which the signal is set to zero or attenuated, while the part of the signal within the minimum and maximum threshold is alternatively attenuated or set to zero, partially attenuated and retained to reconstruct the image in combination with the part of the signal above the maximum threshold or retained without attenuation for reconstructing the image alone or in combination with the part of the signal above the maximum threshold.

9. A method according to claim 8, characterized in that the signal parts above the maximum threshold, below the minimum threshold and between the two said thresholds is retained for imaging being evaluated in parallel and independently to each other and combined with different weights to form a combined image.

10. A method according to claim 1, characterized in that a minimum threshold is also defined for the difference signal between two successive echoes, below which the signal is retained to reconstruct the image, while the part of the signal within the minimum and maximum threshold is alternatively attenuated or set to zero, partially attenuated and retained to reconstruct the image in combination with the part of the signal below the minimum threshold or retained without attenuation for reconstructing the image alone or in combination with the part of the signal below the minimum threshold, while above the maximum threshold the signal is attenuated or set to zero.

11. A method as claimed in claim 1, characterized in that its use is provided in combination with the introduction of contrast agents in spontaneous flow.

12. A method as claimed in claim 11, characterized in that a minimum threshold is defined for the difference signal between two successive echoes, below which the difference signal is set to zero or strongly attenuated.

13. A method as claimed in claim 1, characterized in that it is used for detecting displacements of invasive surgical instruments, such as microinstruments, intraoperative probes, and needles.

14. A method as claim in claim 1, characterized in that it is used for the detection of calcifications or similar structures.

15. An apparatus for ultrasonic imaging, comprising:

a probe for emitting RF ultrasonic pulses, generally consisting of a set of transducers aligned on at least one line;

transducers for receiving the echo signals reflected by a first object and a second object while the illuminating ultrasonic pulses propagate therein;

processing means, including means for generating an image from said echo signals received from said first and second objects;

means for determining difference signals between two received echo signals from said first and second objects;

means for applying a threshold level to said difference signals to form first and second signal level regions such that the difference signal from one of said objects substantially falls within said first region and said difference signal from said other object substantially falls within said second region; and

means for attenuating the level of said echo signals from said object whose difference signal substantially falls within said first region in order to enhance the image of said other object.

16. An apparatus as claimed in claim 15, characterized in that it includes a unit for generating a maximum threshold for the difference signal and means for discriminating the parts of the signal above and below the threshold as well as means for attenuating, setting to zero or retaining one of the two parts of the signal discriminated by the threshold.

17. An apparatus as claimed in claim 15, characterized in that it includes a unit for generating a minimum threshold for the difference signal and means for discriminating the parts of the signal above and below the threshold as well as means for attenuating, setting to zero or retaining one of the two parts of the signal discriminated by the threshold.

18. An apparatus according to claim 15, characterized in that it includes a unit for generating at least a maximum and at least a minimum threshold for the difference signal and means for discriminating the parts of the signal in relation to the thresholds as well as means for attenuating, setting to zero or retaining one or more of the parts of the signal discriminated by the thresholds.

19. An apparatus as claimed in claim 15, characterized in that it includes a “

B-Mode”

echo signal processing unit.

20. An apparatus as claimed in claim 15, characterized in that it includes means for weighting echo signals to be subtracted, so that a signal of a certain predetermined level may be obtained even with the contributions of stationary tissues.

21. An apparatus as claimed in claim 15, characterized in that it is used for detecting displacements of invasive surgical instruments, such as microinstruments, intraoperative probes, and needles.

22. An apparatus as claimed in claim 15, characterized in that it is used for the detection of calcifications or similar structures.