Ultrasound-based characterization of particles in a fluid-filled hollow structure

Abstract

In accordance with a method for characterization of particles in a fluid-filled hollow structure, an ultrasound signal with a frequency spectrum, which exhibits a local maximum at a variable measurement frequency, is emitted in the direction of a part area of the hollow structure and reflected components are detected. The measurement frequency is tuned in a predetermined measurement interval, and depending on the detected reflected components, a spectral response curve is acquired as a function of the measurement frequency. Depending on the response curve, at least one characteristic property for a part of the particles located in the part area of the hollow structure is determined. The characteristic property includes a measure for an adhesion of the particles of the part of the particles located in the part area of the hollow structure.

Claims

1. A method for characterization of a mobility of particles in a fluid-filled blood vessel, the method comprising: emitting an ultrasound signal with a frequency spectrum, which has a local maximum at a variable measurement frequency, in a direction of a part area of the fluid-filled blood vessel; detecting reflected components of the ultrasound signal as a result of an ultrasound reflection of the ultrasound signal; tuning the variable measurement frequency in a predetermined measurement interval; acquiring a spectral response curve of the ultrasound reflection as a function of the variable measurement frequency based on the reflected components; and determining a restriction of movement of the particles in a fluid of the fluid-filled blood vessel via: (1) an adhesion of the particles to an inner wall of the fluid-filled blood vessel, or (2) an adhesion of the particles to a medical instrument in the fluid-filled blood vessel, wherein the restriction of movement is deduced via at least one curve property of the spectral response curve of the ultrasound reflection, wherein the restriction of movement of the particles reflects a mobility of the particles located in the part area of the fluid-filled blood vessel, and wherein the particles are embolization beads having diameters in a range of 10 micrometers to 500 micrometers.

2. The method of claim 1, further comprising: determining an additional measure for an amount of the particles located in the part area of the fluid-filled blood vessel based on the spectral response curve of the ultrasound reflection.

3. The method of claim 2, further comprising: determining an amplitude value of the spectral response curve of the ultrasound reflection at a predefined frequency value of the variable measurement frequency in the predetermined measurement interval, wherein the additional measure is determined depending on the amplitude value.

4. The method of claim 3, wherein the predefined frequency value corresponds to a local maximum point of the spectral response curve of the ultrasound reflection.

5. The method of claim 1, further comprising: comparing the at least one curve property of the spectral response curve of the ultrasound reflection with at least one predetermined reference curve property, wherein the restriction of movement of the particles is determined based on a result of the comparing.

6. The method of claim 5, wherein the at least one curve property of the spectral response curve of the ultrasound reflection comprises a widening and a shifting of a resonance peak of the spectral response curve of the ultrasound reflection, and wherein the widening and/or the shifting, with respect to the at least one predetermined reference curve property, of the resonance peak of the spectral response curve of the ultrasound reflection corresponds to the restriction of movement of the particles.

7. The method of claim 6, wherein a strength of the spectral response curve of the ultrasound reflection corresponds to an amount of the particles located in the part area of the fluid-filled blood vessel.

8. The method of claim 1, further comprising: determining a characteristic correlation value based on the spectral response curve of the ultrasound reflection and a reference curve, wherein the restriction of movement is determined based on the characteristic correlation value.

9. The method of claim 1, wherein the predetermined measurement interval lies within a range of 5 MHz to 12 MHz.

10. The method of claim 1, wherein a bandwidth of the frequency spectrum of the emitted ultrasound signal is greater than or equal to 1 kHz and less than or equal to 100 kHz.

11. The method of claim 1, further comprising: emitting a further ultrasound signal with a further frequency spectrum in the direction of the part area of the fluid-filled blood vessel before the emitting of the ultrasound signal, wherein a bandwidth of the further frequency spectrum is greater than a bandwidth of the frequency spectrum; detecting further reflected components of the further ultrasound signal; and checking, based on the further reflected components, whether the part area of the fluid-filled blood vessel is hiding a further blood vessel or a further part area of the fluid-filled blood vessel in a direction of propagation of the further ultrasound signal, wherein the ultrasound signal is emitted based on a result of the check.

12. The method of claim 1, wherein the medical instrument is a catheter or a guide wire.

13. The method of claim 1, wherein the determining of the restriction of movement is via both the adhesion of the particles to the inner wall of the fluid-filled blood vessel and the adhesion of the particles to the medical instrument in the fluid-filled blood vessel.

14. An ultrasound system for characterization of a mobility of particles in a fluid-filled blood vessel, the ultrasound system comprising: an ultrasound probe configured to emit an ultrasound signal with a frequency spectrum that has a local maximum at a variable measurement frequency, in a direction of a part area of the fluid-filled blood vessel and to detect reflected components of the ultrasound signal as a result of an ultrasound reflection of the ultrasound signal; a control unit configured to actuate the ultrasound probe, which is configured to tune the variable measurement frequency in a predetermined measurement interval; and an evaluation unit configured to acquire a spectral response curve of the ultrasound reflection as a function of the variable measurement frequency based on the reflected components, and determine a restriction of movement of the particles in a fluid of the fluid-filled blood vessel via: (1) an adhesion of the particles to an inner wall of the fluid-filled blood vessel, or (2) an adhesion of the particles to a medical instrument in the fluid-filled blood vessel, wherein the restriction of movement is deduced via at least one curve property of the spectral response curve of the ultrasound reflection, wherein the restriction of movement of the particles reflects a mobility of the particles located in the part area of the fluid-filled blood vessel, and wherein the particles are embolization beads having diameters in a range of 10 micrometers to 500 micrometers.

15. The ultrasound system of claim 14, wherein the ultrasound probe is an endocorporeally insertable ultrasound probe.

16. The ultrasound system of claim 14, wherein the at least one curve property of the spectral response curve of the ultrasound reflection comprises a widening and a shifting of a resonance peak of the spectral response curve of the ultrasound reflection, and wherein the widening and/or the shifting, with respect to at least one predetermined reference curve property, of the resonance peak of the spectral response curve of the ultrasound reflection corresponds to the restriction of movement of the particles.

17. The ultrasound system of claim 16, wherein a strength of the spectral response curve of the ultrasound reflection corresponds to an amount of the particles located in the part area of the fluid-filled blood vessel.

18. The ultrasound system of claim 14, wherein the ultrasound probe is configured to create the ultrasound signal so that the predetermined measurement interval lies within a range of 5 MHz to 12 MHz.

19. The ultrasound system of claim 14, wherein the ultrasound probe is configured to create the ultrasound signal with a bandwidth of the frequency spectrum that is greater than or equal to 1 kHz and less than or equal to 100 kHz.

20. A non-transitory computer program product with commands that, when executed by an ultrasound system, cause the ultrasound system to: emit, by an ultrasound probe of the ultrasound system, an ultrasound signal with a frequency spectrum, which has a local maximum at a variable measurement frequency, in a direction of a part area of a fluid-filled blood vessel; detect, by the ultrasound probe, reflected components of the ultrasound signal as a result of an ultrasound reflection of the ultrasound signal; actuate the ultrasound probe by a control unit of the ultrasound system; tune, by the control unit, the variable measurement frequency in a predetermined measurement interval; acquire, by an evaluation unit of the ultrasound system, a spectral response curve of the ultrasound reflection as a function of the variable measurement frequency based on the reflected components; and determine, by the evaluation unit, a restriction of movement of particles in a fluid of the fluid-filled blood vessel via: (1) an adhesion of the particles to an inner wall of the fluid-filled blood vessel, or (2) an adhesion of the particles to a medical instrument in the fluid-filled blood vessel, wherein the restriction of movement is deduced via at least one curve property of the spectral response curve of the ultrasound reflection, wherein the restriction of movement of the particles reflects a mobility of the particles located in the part area of the fluid-filled blood vessel, and wherein the particles are embolization beads having diameters in a range of 10 micrometers to 500 micrometers.

21. The non-transitory computer program product of claim 20, wherein the at least one curve property of the spectral response curve of the ultrasound reflection comprises a widening and a shifting of a resonance peak of the spectral response curve of the ultrasound reflection, and wherein the widening and/or the shifting, with respect to at least one predetermined reference curve property, of the resonance peak of the spectral response curve of the ultrasound reflection corresponds to the restriction of movement of the particles.

22. The non-transitory computer program product of claim 21, wherein a strength of the spectral response curve of the ultrasound reflection corresponds to an amount of the particles located in the part area of the fluid-filled blood vessel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the figures:

(2) FIG. 1 depicts a schematic diagram of an example of a form of embodiment of an ultrasound system.

(3) FIG. 2 depicts a schematic diagram of a response curve in accordance with an example of a form of embodiment of a method and also a reference curve.

DETAILED DESCRIPTION

(4) Shown in FIG. 1 is a schematic diagram of an example of a form of embodiment of an ultrasound system 1. The ultrasound system 1 has an ultrasound probe 2, a control unit 3, which for actuation of the ultrasound probe 2 is connected to the latter. The ultrasound system 1 also includes an evaluation unit 3, which is connected to the ultrasound probe 2 and/or the control unit 3. The control unit 3 and the evaluation unit 3, in various forms of embodiment, may be implemented in a common control and evaluation unit or as separate units.

(5) The control unit 3 may actuate the ultrasound probe 2, so that the probe creates an ultrasound signal with an adjustable or variable measurement frequency. In this case, an ultrasound signal with a specific frequency may be understood as an ultrasound signal with a frequency spectrum that has a local maximum at the specific frequency, e.g., the measurement frequency here.

(6) The ultrasound signal may be emitted in the direction of a fluid-filled hollow structure 8 of an object 5 and partly reflected, whereupon the reflected components may in their turn be detected by the ultrasound probe 2. The ultrasound probe 2 creates a corresponding measurement signal depending on the intensity of the reflected proportions and transfers the measurement signal to the evaluation unit 3.

(7) The object 5 may involve a part of the body or an organ of a human being. The fluid-filled hollow structure 8 may involve a blood vessel or a part of a vessel tree. In particular, the hollow structure 8 is located at least partly in a relevant region of interest 7, which may correspond to a tumor or the like. The control unit 3 is configured to tune the measurement frequency in a predetermined measurement interval and the evaluation unit 3 is designed accordingly to acquire a spectral response curve as a function of the respective reflected components of the ultrasound signal. The intensity of the reflected components, thus also the measurement signal and thus the spectral response curve, is influenced by at least one characteristic property of particles 9 that are located in the fluid-filled hollow structure 8. The particles 9 involve previously introduced embolization beads, which where necessary may also elute a medicament.

(8) The shape and/or height of the spectral response curve may in particular depend on the local concentration of particles 9 and/or on their mobility. The mobility of the particles in this case may depend in particular on adhesion of the particles 9 to inner walls of the hollow structure 8, instruments or the like. On the other hand, location and amount of the adhering particles are of great interest for a person carrying out the treatment.

(9) The greater the concentration of the particles 9 in the correspondingly analyzed part area of the hollow structure 8 is, the greater the intensity of the reflected components tends to be, in particular if a resonance condition in respect of the measurement frequency is present. The greater is the proportion of adhering particles 9 compared to the particles 9 able to move freely in the fluid, the more heavily distributed and/or shifted is the response curve compared to a reference curve, wherein the reference curve describes the theoretical or idealized frequency response of freely moving particles 9 in the fluid.

(10) This is shown schematically in FIG. 2. Shown in FIG. 2 as a dashed line are the response curve 11 as a function of the measurement frequency and the reference curve 12 as a solid line. The resonance peak of the response curve 11 is widened or shifted to higher frequencies here compared to the resonance peak of the reference curve 12 by the adhesion of a part of the particles 9 to the inner wall of the hollow structure.

(11) From the widening and/or shifting of the resonance peak, the evaluation unit 3 may deduce the proportion of the adhering particles 9. From the amplitude of the response curve 11 at the resonant frequency or from the maximum amplitude of the response curve 11, the evaluation unit 3 may deduce the local concentration of the particles 9 in the correspondingly analyzed part area of the hollow structure 8.

(12) The particles 9 may involve embolization beads, which are introduced by a catheter 10 beforehand into the vessel tree 6 and in this way are partly also forced forward into the hollow structure 8 or the analyzed part area of the hollow structure 8. The described evaluation of the response curve 11 by the evaluation unit 3 thus enables a user to check the current status of the embolization or the progress or the success or the embolization.

(13) In various forms of embodiment, the ultrasound system 1 has a display 4, which is connected to the evaluation unit 3. The evaluation unit 3 may then actuate the display 4, in order to display on the latter, the at least one characteristic property of the particles 9 encoded in color and/or brightness, for example, as an overlay on a conventional B-mode scan, for example.

(14) In various forms of embodiment, as outlined in FIG. 1, the ultrasound probe 2 may be embodied as an endovascular insertable ultrasound probe 2, in particular, at least partly able to be introduced into the vessel tree 6. In this way, higher frequencies are possible, because a shorter range is required. The higher frequencies in their turn lead to an improved spatial resolution. In other forms of embodiment, the ultrasound probe 2 may be embodied as a conventional ultrasound probe 2, which is applied from outside the body.

(15) In accordance with various forms of embodiment, e.g., via the width and/or shape of the response curve 11 with the aid of the spectral ultrasound resonance of the particles 9, information about the spatial distribution of particles 9 swimming freely in the fluid or adhering is determined.

(16) To do this, an ultrasound probe operating at high frequency may be inserted, for example, endovascularly. The measurement frequency of the ultrasound probe is tunable, so that at least two different frequency spectra with corresponding local maxima may be emitted and received. A corresponding narrow size dispersion of the particles 9 or of the embolization beads makes possible a good definition of the ultrasound resonance curve, e.g., of the response curve 11. Because the spectral resonance response of an individual particle 9 is dependent on whether the particle 9 is swimming freely in the fluid or whether it is adhering to something, the characteristic properties of the particles 9 on average may be analyzed by the response curve 11.

(17) In various forms of embodiment, the ultrasound reflection, for example, in B-mode, is measured as a narrowband measurement with the ultrasound probe, in particular endovascularly. The measurement frequency is tuned and, for each relevant location in the tissue being examined or in the object being examined, a corresponding spectral response curve as described is recorded. The response curve may be recorded in this case at the basic frequency of the measurement frequency or at higher harmonics or in a combination. For each measured section of the hollow structure in the target region the spectral response curve is evaluated accordingly. The strength of the signal, in particular in the range of the resonant frequency, may correspond to the amount of particles of the concentration of particles in this region. A widening and/or shifting of the resonance peak corresponds to an adhesion of the particles in this region. The more the resonance peak is widened or shifted, the greater is the proportion of adhering particles. The proportion of adhering particles may be determined via a correlation, (e.g., a value of a convolution integral), between measured frequency response and the idealized frequency response of freely moving particles, (e.g., between the response curve and the reference curve). As an alternative or in addition, a curve fit may be carried out, with the aid of which width and central frequency of the resonance peak may be determined and reconciled.

(18) The narrowband measurement leads to temporally longer pulses, so that the axial resolution of the ultrasound measurement falls correspondingly. Therefore it may be provided by a conventional wideband B-node ultrasound scan that two hollow structures filled with particles do not lie closely behind one another. If this is the case, the alignment of the ultrasound may be adapted accordingly. Optionally, an automatic algorithm may be employed, which checks this condition and enables the analysis with the aid of the narrowband ultrasound signal, provided no corresponding hollow structures lying behind one another are present in the target region.

(19) Via the wideband B-mode scan, (e.g., the B-mode scan with temporally short pulses), a registration may also be determined, so that with the resonance signal determined in the narrowband measurement, (e.g., the response curve), the respective section may be assigned to the hollow structure and for example the measurement result may then be displayed for this section.

(20) Between the individual B-mode images at various frequencies, an image-based movement correction may be undertaken. For this, in various forms of embodiment, for example, a narrowband ultrasound at the respective measurement frequency with long pulses for resonance measurement and a wideband ultrasound with short pulses for the imaging necessary for the movement correction may be employed alternately.

(21) It is to be understood that the elements and features recited in the appended claims may be combined in different ways to produce new claims that likewise fall within the scope of the present disclosure. Thus, whereas the dependent claims appended below depend from only a single independent or dependent claim, it is to be understood that these dependent claims may, alternatively, be made to depend in the alternative from any preceding or following claim, whether independent or dependent, and that such new combinations are to be understood as forming a part of the present specification.

(22) While the present disclosure has been described above by reference to various embodiments, it may be understood that many changes and modifications may be made to the described embodiments. It is therefore intended that the foregoing description be regarded as illustrative rather than limiting, and that it be understood that all equivalents and/or combinations of embodiments are intended to be included in this description.