Ultrasound probe and intravascular ultrasound imaging method

Abstract

The invention relates to an ultrasound probe (100) extending in a longitudinal direction along an axis (105), the ultrasound probe comprising an interconnection substrate (130) having a first face and a second face opposite the first face, a first number of first ultrasound transducers (110A) which have a first elevation (HA) and are arranged on the first face of the interconnection substrate (130), and a second number of second ultrasound transducers (110B) which have a second elevation (HB) and are arranged on the first face of the interconnection substrate (130) next to the first ultrasound transducers (110A) along the axis (105).

Description

DESCRIPTION TITLE: Ultrasound probe and intravascular ultrasound imaging method This patent application claims priority from French patent application FR24 / 07294, which will be considered an integral part of this description. technical field

[0001] This description generally relates to ultrasonic probes comprising ultrasonic transducers.

[0002] An example of the application of such an ultrasound probe concerns intravascular ultrasound imaging procedures, the ultrasound probe being, for example, integrated into a catheter. Previous technique

[0003] It has already been proposed to integrate small ultrasound probes into a catheter intended for insertion into the body, for example, into a blood vessel, of a human or animal patient, particularly for intravascular ultrasound (IVUS) imaging, for example, for intravascular ultrasound diagnostic or treatment applications, or even to evaluate the effectiveness of a treatment (post-treatment diagnosis). An intravascular ultrasound imaging device, or IVUS device, comprising, for example, several ultrasound transducers that form the ultrasound probe, can be introduced into a vessel and guided to an area to be imaged. The ultrasound transducers emit ultrasound waves that are at least partially reflected by specific elements of the vessels.The reflected ultrasonic waves are captured by the ultrasonic transducers which transmit electrical signals representative of the ultrasonic waves captured at. A processing device that handles these electrical signals to produce an image of the vessel in which the IVUS device is placed. The resulting image is called an ultrasound image.

[0004] Given the large range of vessel sizes, intravascular imaging devices emitting ultrasound at different fixed frequencies are commercially available.

[0005] To simplify intravascular ultrasound imaging procedures, it may be desirable to be able to emit ultrasound signals at different frequencies with the same ultrasound probe. Ultrasound probes exist that include broadband ultrasound transducers capable of emitting ultrasound waves at different frequencies.

[0006] The optimal resolution of ultrasonic images obtainable from ultrasonic transducers depends, in particular, on the transducer elevation, which increases as the frequency of the emitted ultrasonic waves decreases. Since the transducer elevation is fixed, broadband ultrasonic transducers can only be optimized for a single frequency, so the resolution of the resulting ultrasonic images may not be optimal for multiple operating frequencies. Summary of the invention

[0007] One embodiment overcomes all or part of the disadvantages of known ultrasonic probes.

[0008] One embodiment provides for an ultrasonic probe extending in a longitudinal direction along an axis, the ultrasonic probe comprising: - an interconnection substrate comprising a first face and a second face opposite to the first face; - a first number of first ultrasonic transducers having a first elevation and arranged on the first face of the interconnecting substrate; and - a second number of second ultrasonic transducers having a second elevation and arranged on the first face of the interconnecting substrate, next to, along the axis, the first ultrasonic transducers.

[0009] According to one embodiment, the first ultrasonic transducers are broadband ultrasonic transducers configured to emit first ultrasonic waves centered on an operating frequency that can vary between a low operating frequency of between 30 MHz and 80 MHz and a high operating frequency of between 30 MHz and 120 MHz, the low operating frequency being lower than the high operating frequency.

[0010] According to one embodiment, the first number and the first elevation of the first ultrasonic transducers are optimized for operation of the first ultrasonic transducers at the high operating frequency.

[0011] According to one embodiment, the second ultrasonic transducers are broadband ultrasonic transducers or fixed operating frequency ultrasonic transducers.

[0012] According to one embodiment, the second number of the second ultrasonic transducers is optimized for operation of the second ultrasonic transducers at the low operating frequency.

[0013] According to one embodiment, the first number is equal to the second number.

[0014] According to one embodiment, each first ultrasonic transducer is electrically connected with one of the second ultrasonic transducers.

[0015] According to one embodiment, the second elevation of the second ultrasonic transducers is chosen so that the sum of the first and second elevations is optimized for operation of the first and second ultrasonic transducers at the low operating frequency.

[0016] According to one embodiment, the second elevation is equal to the first elevation.

[0017] According to one embodiment, the first ultrasonic transducers and the second ultrasonic transducers are arranged in a first region of the ultrasonic probe, the ultrasonic probe further comprising at least one control circuit arranged in a second region of the ultrasonic probe and on the first face or the second face of the interconnecting substrate, the second region being distinct from the first region.

[0018] According to one embodiment, the first face is an external face of the interconnecting substrate and the second face is an internal face of the interconnecting substrate.

[0019] According to one embodiment, the second region is axially offset relative to the first region.

[0020] According to one embodiment, the ultrasonic probe has an external cylindrical shape around the axis, the first transducers being distributed, for example regularly distributed, around the axis and the second transducers being distributed, for example regularly distributed, around the axis.

[0021] One embodiment also provides for the use of an ultrasonic probe as defined previously, comprising, in a first mode of operation, the emission of first ultrasonic waves by the first and second ultrasonic transducers, and, in a second mode of operation, the emission of second ultrasonic waves only by the first ultrasonic transducers.

[0022] According to one embodiment, in the first operating mode, the first ultrasonic transducers are controlled to emit the first ultrasonic waves at the low operating frequency, and, in the second operating mode, the first ultrasonic transducers are controlled to emit the first ultrasonic waves at the high operating frequency.

[0023] According to one embodiment, the use further includes, in a third mode of operation, the emission of third ultrasonic waves only by the second ultrasonic transducers. Brief description of the drawings

[0024] These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, given by way of non-limiting example, in relation to the attached figures, among which:

[0025] Figure 1 is a partial and schematic perspective view of a known ultrasonic probe;

[0026] Figure 2 is an enlarged view of a portion of the probe in Figure 1 shown spread out in a plane;

[0027] Figure 3 is a partial, schematic perspective view of another known ultrasonic probe;

[0028] Figure 4 is a partial and schematic perspective view of one embodiment of an ultrasonic probe;

[0029] Figure 5 is an enlarged view of a portion of the probe in Figure 4 shown spread out in a plane;

[0030] Figure 6 and Figure 7 are partial and schematic perspective views of variant embodiments of the ultrasonic probe of Figure 4;

[0031] Figure 8 is a perspective view representing an ultrasonic probe according to a more detailed embodiment;

[0032] Figure 9 is a side view of the ultrasonic probe in Figure 8; and

[0033] Figure 10 is a cross-sectional view of the ultrasonic probe in Figure 9. Description of the implementation methods

[0034] The same elements have been designated by the same reference numerals in the different figures. In particular, structural and / or functional elements common to the different embodiments may have the same reference numerals and may have identical structural, dimensional and material properties.

[0035] For the sake of clarity, only the steps and elements necessary for understanding the described embodiments have been shown and detailed. In particular, the ultrasonic transducers of the described ultrasonic probes have not been detailed, as the described embodiments are compatible with all or most known ultrasonic transducer structures. Furthermore, the control circuits of the described ultrasonic probes have not been detailed, the embodiments described being compatible with all or most common control circuits for ultrasonic transducers.

[0036] Unless otherwise specified, when referring to two connected elements, this means directly connected without any intervening elements other than conductors, and when referring to two coupled elements, this means that these two elements can be connected or linked via one or more other elements. Furthermore, the terms "insulator" and "conductor" are understood here to mean "electrically insulating" and "electrically conductive," respectively.

[0037] In the description that follows, when referring to absolute positional qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative positional qualifiers, such as the terms "above", "below", "superior", "inferior", etc., or to orientational qualifiers, such as the terms "horizontal", "vertical", etc., unless otherwise specified, reference is made to the orientation of the figures in a normal position of use.

[0038] Unless otherwise specified, the expressions "approximately", "roughly", "about", and "on the order of" mean within 10% or 10°, preferably within 5% or 5°.

[0039] In the following description, when referring to a longitudinal direction, we are referring to a direction parallel to the axis of the ultrasonic probe. This can also be called an axial direction. The longitudinal direction corresponds to the Z direction shown in the figures. A transverse direction corresponds to a direction taken in a plane perpendicular to the longitudinal direction. longitudinal. The figures illustrate two transverse directions X and Y. A section corresponds to a shape defined in a plane transverse to the longitudinal direction.

[0040] In the following description, unless otherwise specified, a transducer is referred to as an ultrasonic transducer, and unless otherwise specified, a probe is referred to as an ultrasonic probe. An ultrasonic transducer is a transducer adapted to convert an electrical signal into an ultrasonic wave, and conversely, to convert an ultrasonic wave into an electrical signal. Depending on the type of transducer, the electrical signal may correspond to a voltage, a current, or an electrical charge. In the following description, a parameter of an ultrasonic transducer array (including the number of ultrasonic transducers in the array, the elevation of the ultrasonic transducers in the array, etc.) is referred to as an ultrasonic transducer.) is said to be optimized for an operating frequency of the ultrasonic transducers when it allows obtaining an ultrasonic image of maximum resolution when the ultrasonic transducers are driven at the operating frequency.

[0041] Figure 1 is a partial, schematic perspective view of a known ultrasonic probe 10.

[0042] The ultrasound probe 10 can be integrated into the distal part of a catheter. The ultrasound probe 10 can be part of an ultrasound imaging device (not shown), for example an intravascular ultrasound imaging device, or IVUS device.

[0043] The ultrasonic probe 10 has a substantially cylindrical external shape around an axis 105. The ultrasonic probe 10 comprises an array of ultrasonic transducer elements, designated ultrasonic transducers 11, adapted to emit and receive ultrasonic waves. The transducers The 11 ultrasonic transducers are distributed around axis 105. The 11 ultrasonic transducers are distributed around axis 105 and are identical.

[0044] During operation, the ultrasonic transducers 11 emit ultrasound waves (US) which are at least partially reflected by specific elements of the vessels. The reflected ultrasound waves are captured by the ultrasonic transducers 11, which transmit electrical signals representative of the captured ultrasound waves to a processing device (not shown). This device processes these electrical signals to produce an ultrasound image of the environment in which the probe is placed.

[0045] Figure 2 is an enlarged view of part of probe 10 of figure 1 shown spread out in a plane parallel to axis 105.

[0046] The ultrasonic transducer array 11 is characterized by the following parameters: - the number N of ultrasonic transducers 11; - the height H, also called elevation, of an ultrasonic transducer 11 which corresponds to the dimension of the ultrasonic transducer 11 parallel to the axis 105; - the step p which corresponds to the center-to-center distance between two successive ultrasonic transducers 11; - the width e of an individual ultrasonic transducer 11; - the gap g between the opposite edges of two successive ultrasonic transducers 11; and - the distance A, also called the total opening for the deflection direction or the active direction, equal to the product of N and p.

[0047] In the embodiment illustrated in Figure 1, the ultrasonic transducers 11 are arranged all around the axis 105. The total opening angle of the probe 10 is then 360 degrees. However, in this variant, the ultrasound transducers 11 can be arranged around the axis 105 over an angular sector of less than 360 degrees. The probe 10 can then include means for rotating the array of ultrasound transducers 11 around the axis 105 to explore an entire blood vessel.

[0048] The distribution of the ultrasound transducers 11 around the axis 105 allows for the acquisition of a 360° ultrasound image. For intravascular ultrasound imaging applications, the penetration of ultrasound waves into blood vessel tissue depends primarily on the operating frequency. The lower the operating frequency, the deeper the ultrasound waves penetrate into the blood vessel tissue. Furthermore, for a given operating frequency, among the dimensional parameters described previously, it is primarily the elevation H that determines the penetration depth at which optimal resolution is obtained for the images derived from the ultrasound waves reflected and captured by the probe 10. The step size p also plays a role in optimal resolution, but to a lesser extent than in the case of a planar transducer array.The step size p and elevation H required to achieve optimal resolution increase as the operating frequency decreases. Typically, the step size p and elevation H are therefore chosen based on the operating frequency of the probe 10 to obtain optimal resolution. Furthermore, other considerations must be taken into account when determining the optimal step size p. Indeed, for better radial resolution, the number N of transducers 11 is generally increased (which leads to a decrease in the step size p for a given total aperture A). However, a decrease in the step size p can lead to... a decrease in width e. Indeed, the gap g can be constant regardless of the number N of transducers 11 because it can be imposed by the manufacturing process of the transducers 11, in particular the cutting step used to delimit the transducers 11. This therefore leads to a decrease in the active area (equal to the product of the width e by the elevation H) of each transducer 11 and therefore a decrease in the signal-to-noise ratio of the transducer 11. There is therefore a compromise to be found between signal-to-noise ratio and resolution for the determination of the optimal step size p.

[0049] Figure 3 is a partial, schematic perspective view of another known ultrasonic probe 20. The ultrasonic probe 20 comprises an array of ultrasonic transducers 11 like the ultrasonic probe 10 but has a smaller step size p and elevation H than the ultrasonic probe 10. The ultrasonic probe 10 is therefore optimized to operate at a low operating frequency, for example 10 MHz, while the ultrasonic probe 20 is optimized to operate at a high operating frequency, for example 20 MHz.

[0050] Most often, the bandwidth of transducers is limited. As a general rule, good image quality is obtained with a bandwidth, measured at -6 dB, greater than 60% of the center frequency. This center frequency is typically chosen as the probe's operating frequency. Generally, an ultrasonic transducer is designed to operate at a fixed frequency, dictated by the area of ​​interest for which optimal image resolution is desired. This operating frequency determines the optimal dimensions of the transducer structure. Therefore, several different ultrasonic probes must be used if... We need ultrasonic images obtained at different operating frequencies.

[0051] There are so-called broadband ultrasonic transducers whose operating frequency can be varied within a range of frequencies between a low operating frequency and a high operating frequency. However, since the step size p and the elevation H of the ultrasonic probe are fixed, they can only be optimized for a single frequency within the frequency range, so the resolution of the obtained ultrasonic images is not optimal over the entire frequency range.

[0052] Figure 4 is a partial, schematic perspective view of one embodiment of an ultrasonic probe 100. Figure 5 is an enlarged view of a portion of probe 100 from Figure 4, shown spread out on a plane. Figures 6 and 7 are partial, schematic perspective views of alternative embodiments of the ultrasonic probe 100 of Figure 4.

[0053] The 100 ultrasound probe can be integrated into a catheter. The 100 ultrasound probe can be part of an ultrasound imaging device (not shown), for example, an intravascular ultrasound imaging device, or IVUS device, which typically includes a catheter, a guidewire, and / or a guide catheter, and is adapted to be introduced into a lumen of a vessel or other anatomical space in a human or animal patient. The ultrasound probe can be positioned at a distal end of the imaging device. The imaging device may include a transmission line, for example, in the form of a cable bundle, extending to a proximal end of the imaging device. At its proximal end, the imaging device may include, or be connected to, a treatment device. adapted to control the ultrasonic probe to produce ultrasonic waves in emission, and to process ultrasonic waves received by the ultrasonic probe to produce a corresponding image.

[0054] The ultrasound probe 100 has a substantially cylindrical external shape with a circular base around an axis 105, parallel to the Z direction. To allow insertion into a space with a small cross-section or diameter, the external diameter DI of the ultrasound probe can be less than 5 mm, or even less than 3 mm. This can correspond to the external diameter of an imaging device in which the ultrasound probe 100 is integrated.

[0055] The ultrasonic probe 100 comprises a first array of first ultrasonic transducers and a second array of second ultrasonic transducers 110B. The first ultrasonic transducers 110A are distributed around the axis 105 on an interconnecting substrate 130. The second ultrasonic transducers 110B are distributed around the axis 105, on the interconnecting substrate 130 next to the first ultrasonic transducers 110A.

[0056] In the following description, the parameters, described previously in relation to Figure 2, are followed by the fixed suffix A when used for the first ultrasonic transducer array and the first 110A ultrasonic transducers, and by the fixed suffix B when used for the second ultrasonic transducer array and the second 110B ultrasonic transducers. Therefore, the first ultrasonic transducer array comprises NA ultrasonic transducers, the first 110A ultrasonic transducers have an elevation HA and a step size pA, the second ultrasonic transducer array comprises NB ultrasonic transducers, and the second ultrasonic transducers 110A have an elevation HB and a pitch pB. The total elevation HT is the sum of the elevations HA and HB.

[0057] In one embodiment, the first 110A ultrasonic transducer array comprises broadband ultrasonic transducers, i.e., transducers that can be controlled at an operating frequency within a frequency range from a low operating frequency to a high operating frequency. In one embodiment, the low operating frequency is between 30 MHz and 80 MHz. In another embodiment, the high operating frequency is between 60 MHz and 150 MHz. In yet another embodiment, the difference between the high and low operating frequencies is between 30 MHz and 120 MHz.

[0058] According to one embodiment, the pitch pA of the broadband ultrasonic transducer array 110A corresponds to the pitch that would be chosen for the ultrasonic probe 20 shown in Figure 3, i.e., optimized to operate at the high operating frequency. According to another embodiment, the elevation HA of the first ultrasonic transducer array 110A is equal, to within 10%, to the elevation that would be chosen for the ultrasonic probe 20 shown in Figure 3, i.e., optimized to operate at the high operating frequency.

[0059] According to one embodiment, the second ultrasonic transducer array 110B also includes broadband ultrasonic transducers, preferably in substantially the same frequency range as the ultrasonic transducers 110A of the first ultrasonic transducer array 110A. According to another embodiment, the second ultrasonic transducer array 110B includes ultrasonic transducers with a fixed operating frequency, preferably equal to the frequency of low operating frequency. The frequency band, measured at -6 dB, of the ultrasonic wave spectrum emitted by ultrasonic transducers with fixed operating frequency, measured at -6 dB, is greater than 60% of the center frequency.

[0060] According to one embodiment, the total elevation HT is equal, to within 10%, to the elevation which would be chosen for the ultrasonic probe 10 shown in Figure 1, i.e. optimized to operate at the low operating frequency.

[0061] Broadband 110A and / or 110B ultrasonic transducers can be microelectromechanical systems (MEMS), employing microelectronic manufacturing technologies. A MEMS transducer typically consists of a deformable membrane suspended above a cavity. In one embodiment, the deformable membrane is displaced or deformed by capacitive force using an electrode attached to the membrane and a separate electrode separated by the cavity. This type of ultrasonic transducer is known by the acronym CMUT, from the English Capacitive Micro-machined Ultrasonic Transducer, i.e., a micro-machined ultrasonic capacitive transducer, or capacitive membrane transducer. According to another embodiment, the deformable membrane is displaced or deformed by piezoelectric effect using a layer of piezoelectric material equipped with two electrodes attached to the membrane.A piezoelectric material is a material that expands or contracts when a voltage is applied to it. This type of ultrasonic transducer is known by the acronym PMUT, from the English Piezoelectric Micro-machined Ultrasonic Transducer, that is to say a micro-machined ultrasonic piezoelectric transducer, or membrane piezoelectric transducer.

[0062] When the ultrasonic probe 100 includes a fixed-frequency 110B transducer array, the ultrasonic transducers may be CMUT, PMUT type transducers, or may consist of a layer of a single-crystal or polycrystalline piezoelectric material, for example PZT (Lead-Zirconia Titanate), or of a composite material comprising at least one piezoelectric material, for example a layer of PZT including polymer-filled grooves, or of a polymer piezoelectric material, for example PVDF (polyvinylidene fluoride), sandwiched between two electrodes.

[0063] Each 110A, 110B transducer network can include ultrasonic transducers of different types.

[0064] Each 110A, 110B transducer network can include any number of 110A, 110B ultrasonic transducers, for example between 10 and 200 transducers, for example 40 transducers.

[0065] All or part of the ultrasonic waves emitted by transducers 110A and 110B may be reflected by specific features of the medium into which the ultrasonic probe 100 is inserted, for example, specific features of a vessel. The reflected ultrasonic waves can be received by the ultrasonic transducers 110A and 110B. The electrical signals corresponding to the reflected ultrasonic waves can be processed by a processing device to produce an ultrasonic image of the medium in which the ultrasonic probe is placed, for example, to visualize specific features.

[0066] According to one embodiment, the ultrasonic probe 100 can be controlled according to at least two operating modes from among a first operating mode, a second operating mode, and a third operating mode.

[0067] In the first operating mode, the 110A ultrasonic transducers of the first 110A ultrasonic transducer array and the 110B ultrasonic transducers of the first 110B ultrasonic transducer array are used simultaneously. The first 110A ultrasonic transducers, which are broadband, are driven at a low operating frequency. The second 110B ultrasonic transducers, when broadband, are also driven at a low operating frequency. The second 110B ultrasonic transducers, when at a fixed operating frequency, emit ultrasonic waves at a low operating frequency. The probe 100 then emits USA+USB ultrasonic waves at the low operating frequency. The HT rise is advantageously optimized for the emission of USA+USB ultrasonic waves at the low operating frequency.

[0068] In the second operating mode, only the 110A ultrasonic transducers of the first 110A ultrasonic transducer array are used; the 110B ultrasonic transducers of the second 110B ultrasonic transducer array are not used. According to one embodiment, the first broadband 110A ultrasonic transducers are driven at the high operating frequency. The probe 100 therefore emits USA ultrasonic waves at the high operating frequency. The HA elevation is advantageously optimized for the emission of USA ultrasonic waves at the high operating frequency.

[0069] Optimal resolution ultrasonic images at two operating frequencies can advantageously be obtained with the same ultrasonic probe.

[0070] In the third operating mode, only the 110B ultrasonic transducers of the second array of Ultrasound transducers 110B are used, while the ultrasonic transducers 110A from the first array of ultrasonic transducers 110A are not used. In one embodiment, the second broadband ultrasonic transducers 110B are driven at the high operating frequency. The probe 100 therefore emits USB ultrasonic waves at the high operating frequency. The HB elevation is advantageously optimized for the emission of USB ultrasonic waves at the high operating frequency.

[0071] The first and second transducer arrays 110A and 110B are preferably uniformly distributed to form approximately a cylinder with axis 105 and diameter DI. This is not, however, a limitation; the transducers 110A and 110B can be arranged on a cylindrical surface with an oval base or even on a prismatic surface with a polygonal base. The base is then inscribed in the circle with axis 105 and diameter DI. DI is, for example, less than 6 mm, or even less than 3 mm. The number of transducers forming the first and second transducer arrays is between 20 and 200. The number of transducers in the first transducer array 110A is, for example, greater than or equal to the number of transducers in the second transducer array 110B. The gaps gA and gB between two transducers 110A and 110B generally depend on the cutting process used to separate the transducers and are typically identical.The gaps gA and gB are between 10 pm and 100 pm. The aperture AA of the first ultrasonic transducer array 110A is equal to the aperture AB of the second ultrasonic transducer array 110B. The distances AA or AB are equal to the perimeter of the base of the cylinder with axis 105 and diameter DI. This is not, however, a limitation; the transducers can be arranged accordingly. to image an angular sector less than 360°. The width eA of each first ultrasonic transducer 110A and the width eB of each second ultrasonic transducer 110B are deduced from the characteristics stated above.

[0072] In the embodiment illustrated in Figure 4, only the first ultrasonic transducers 110A are broadband, while the second ultrasonic transducers 110B are fixed-frequency transducers. According to one embodiment, shown in Figure 4, the elevation HA differs from the elevation HB. In the embodiment illustrated in Figure 4, the pitch pA of the first array of ultrasonic transducers 110A is equal to the pitch that would be chosen for the ultrasonic probe 20 shown in Figure 3, i.e., optimized to operate at the high operating frequency. The second array of ultrasonic transducers 110B can be controlled at a fixed operating frequency, for example, the low operating frequency.Preferably, the pitch pB of the second ultrasonic transducer array 110B is equal to the pitch that would be chosen for the ultrasonic probe 10 shown in Figure 1, i.e., optimized for operation at the low operating frequency. The pitch pA is then different from the pitch pB. The probe 100, according to the embodiment illustrated in Figure 4, can be controlled according to the first and second operating modes. In this embodiment, it is easier to obtain both that the elevation HA is equal to the elevation that would be chosen for the ultrasonic probe 20 shown in Figure 3, i.e., optimized for operation at the high operating frequency, and that the elevation HT is equal to the elevation that would be chosen for the ultrasonic probe 10 shown in Figure 1, i.e., optimized for operation at the low operating frequency.

[0073] In the embodiment illustrated in Figure 4, the step size pA of the transducers 110A may not be optimized for operation at the low operating frequency. Furthermore, the number NA of transducers 110A may differ from the number NB of transducers 110B. If NA is greater than NB, the imaging device's processing unit may perform a composition of the received signals (weighting, delay, and summation) using two or more transducers 110A that extend longitudinally, i.e., in a direction parallel to axis 105, in whole or in part, from each transducer 110B to correspond to the same direction as the signals received by that transducer 110B.Similarly, in the case where NB is greater than NA, the processing device of the imaging device can perform a composition of the received signals (weighting, delay and sum) by two or more transducers 110B which extend longitudinally in whole or in part each transducer 110A in order to correspond to the same direction as the signals received by this transducer 110A.

[0074] Alternatively, in the embodiment illustrated in Figure 4, NA is chosen to be equal to NB, which has the dual advantage of simplifying the separation by cutting of transducers 110A and 110B and simplifying the calculations performed by the imaging device's processing unit. Alternatively, in the embodiment illustrated in Figure 4, NA is chosen to be equal to NB, and transducer 110A is electrically connected to its adjacent transducer 110B. In this case, in the first operating mode, these two transducers 110A and 110B operate together, and in the second operating mode, the cutoff frequency of transducer 110B prevents it from transmitting. The fact that transducer 110A and its adjacent transducer 110B are connected Electrically, this arrangement is advantageous because the number of connections in the first and second networks is then reduced to NA connections. Alternatively, in the embodiment illustrated in Figure 4, NA is chosen to be equal to NB, and the elevation HA is substantially equal to the elevation HB. This advantageously allows obtaining two images of the same quality, offset longitudinally, using the second and third operating modes.

[0075] In the variant illustrated in Figure 6, the first ultrasonic transducers 110A and the second ultrasonic transducers 110B are broadband ultrasonic transducers operating in the same frequency range. Furthermore, the HA elevation differs from the HB elevation. In this embodiment, it is easier to ensure that the HA elevation is equal to the elevation that would be chosen for the ultrasonic probe 20 shown in Figure 3, i.e., optimized for operation at the high operating frequency, and that the HT elevation is equal to the elevation that would be chosen for the ultrasonic probe 10 shown in Figure 1, i.e., optimized for operation at the low operating frequency. In the variant illustrated in Figure 6, the pA step size is substantially equal to the pB step size and is equal to the step size that would be chosen for the ultrasonic probe 20 shown in Figure 3, i.e., optimized for operation at the high operating frequency.Advantageously, NA is equal to NB, which simplifies the separation of transducers 110A and 110B by cutting and the calculations performed by the imaging device's processing unit. The probe 100, according to the variant illustrated in Figure 6, can be controlled in both the first and second operating modes.

[0076] In the variant illustrated in Figure 7, the first 110A ultrasonic transducers and the second transducers The 110B ultrasonic transducers are broadband ultrasonic transducers operating in the same frequency range. Furthermore, in Figure 7, the HA elevation is substantially equal to the HB elevation. In this embodiment, it may be more difficult to simultaneously ensure that the HA elevation is equal to the elevation chosen for the ultrasonic probe 20 shown in Figure 3 (i.e., optimized for operation at the high operating frequency) and that the HT elevation is equal to the elevation chosen for the ultrasonic probe 10 shown in Figure 1 (i.e., optimized for operation at the low operating frequency). However, this variant has the advantage that the first 110A ultrasonic transducers can be identical to the second 110B ultrasonic transducers. The manufacturing process for probe 100 is then simplified.Furthermore, two ultrasonic images are obtained at the high operating frequency on two adjacent planes that are symmetrical with respect to the plane of the image obtained at the low operating frequency. In addition, in Figure 7, the step size pA is approximately equal to the step size pB and is equal to the step size that would be chosen for the ultrasonic probe 20 shown in Figure 3, i.e., optimized for operation at the high operating frequency. Advantageously, NA is equal to NB, which simplifies the separation by cutting of the transducers 110A and 110B and the calculations performed by the imaging device's processing unit. The probe 100, according to the variant illustrated in Figure 7, can be controlled according to the first, second, and third operating modes.

[0077] In summary, in the embodiments described above and illustrated in Figures 4, 6, and 7, the first 110A ultrasonic transducers are broadband ultrasonic transducers. Preferably, the The number NA and the elevation HA of the first array of ultrasonic transducers 110A are those that would be chosen for the ultrasonic probe 20 shown in Figure 3, i.e., optimized to operate at the high operating frequency. The second ultrasonic transducers 110B can be fixed-frequency transducers (embodiment illustrated in Figure 4) or broadband ultrasonic transducers (embodiments illustrated in Figures 6 and 7). The number NB of ultrasonic transducers 110B can be chosen equal to the number N that would be chosen for the ultrasonic probe 10 shown in Figure 1, i.e., optimized to operate at the low operating frequency, or it can be chosen equal to the number NA, which then allows each ultrasonic transducer 110B to be electrically connected to the adj. ultrasonic transducer 110A.The HB elevation of the second ultrasonic transducer array 110B can be chosen so that the HT elevation is equal to the H elevation which would be chosen for the ultrasonic probe 10 shown in Figure 1 (embody illustrated in Figure 6), i.e. optimized to operate at the low operating frequency, or be chosen substantially equal to the HA elevation (embody illustrated in Figure 7).

[0078] Figure 8 is a perspective view of a more detailed embodiment of the ultrasonic probe 100. Figure 9 is a side view of the ultrasonic probe 100 of Figure 8. Figure 10 is a cross-sectional view of the ultrasonic probe 100 of Figure 9.

[0079] The cross-sectional view in Figure 10 is taken along the section plane AA identified in Figure 9. Section AA is taken in a region of transducers 101 described later.

[0080] In the following description, a distal end refers to the end through which the ultrasound probe, or imaging device, is introduced into the medium to be analyzed, and a proximal end refers to the end opposite the distal end. The proximal end typically corresponds to the electrical connection, or wiring, end of the ultrasound probe, or imaging device.

[0081] The first ultrasonic transducers 110A extend along a first circumferential band of the ultrasonic probe, around the axis 105. The second ultrasonic transducers 110B extend along a second circumferential band of the ultrasonic probe, around the axis 105. In one embodiment, the first circumferential band is located next to the second circumferential band along the axis 105. The first array of transducers 110A, the first circumferential band, the second array of transducers 110B, and the second circumferential band extend longitudinally in a first region 101, or transducer region, of the ultrasonic probe 100.

[0082] The ultrasonic transducers 110A and 110B are formed by several elements. Schematically, in Figure 10, each ultrasonic transducer 110A is represented very schematically by a stack of two sectors 111 and 112. The transducers 110A are separated from each other by slots 113. Each transducer 110A and 110B can comprise two electrodes, not shown.

[0083] The transducers 110 can be surrounded by a protective sheath 108, which is preferably biocompatible, and which is only shown in Figure 10.

[0084] The ultrasonic probe 100 also includes an electrical component, for example an inductor, and / or a electronic control circuit, or control circuit, not visible in the figures, and preferably a network of electronic control circuits, or control circuits. Each control circuit may be a controller, a control integrated circuit, an application-specific integrated circuit, known by the acronym ASIC, from the English "Application Specific Integrated Circuit", or any other electronic circuit suitable for controlling one or more 110A, 110B transducers.

[0085] The control circuits can be configured to select specific transducers 110A and 110B for ultrasonic transmission / reception, to transmit control signals to the selected transducers to generate and transmit ultrasonic waves, and / or to accept or even amplify return signals from the selected transducer elements when they receive reflected ultrasonic waves. More generally, several types of signals, such as control, power, and / or data signals, can be exchanged between transducers 110A and 110B and the control circuits.

[0086] The control circuits are arranged, or distributed, along a third circumferential band of the ultrasonic probe, around the axis 105. The network of control circuits, and the third circumferential band, extend longitudinally into a second region 102, or control region, of the ultrasonic probe 100. The second region 102 is positioned axially at a distance from the first region 101.

[0087] Each control circuit can be configured to control multiple 110A and / or 110B transducers, for example, to control between three and thirty 110A and / or 110B transducers. In other words, there can be a number The number of control circuits is less than the number of transducers. Four control circuits have been shown, but this is a non-limiting example.

[0088] The ultrasonic probe 100 may include a third region 104, or connector region, extending the control region 102 opposite the transducer region 101.

[0089] The transducer region 101 can be positioned at a distal end of the ultrasonic probe 100. The control region 102 or the connection region 104 can be positioned at a proximal end of the ultrasonic probe 100.

[0090] The ultrasonic probe 100 further includes the interconnecting substrate 130 around the axis 105. The interconnecting substrate 130 has an external face 130A, or upper face, and an internal face 130B, or lower face.

[0091] The interconnecting substrate 130 has a distal end 130C, which is an end positioned at the transducers 110, and a proximal end 130D which is opposite the distal end 130C.

[0092] The interconnection substrate 130 is configured to provide an electrical connection between the ultrasonic transducers 110A and 110B and the control circuits, as well as with circuits, connectors and / or components external or internal to the ultrasonic probe 100. The interconnection substrate 130 can also form a structural support for the ultrasonic transducers 110A and 110B and the control circuits.

[0093] The interconnecting substrate 130 generally comprises a set of conductive tracks 135 insulated from each other and arranged in and / or on a dielectric layer 136. The interconnecting substrate 130 may be multilayered and comprise a stack of two layers dielectrics 136 or more of two dielectric layers 136 and, for each dielectric layer 136, a set of conductive tracks 135 insulated from each other and arranged in and / or on the dielectric layer 136. By way of example, an interconnect substrate 130 comprising two dielectric layers 136, with a set of conductive tracks 135 in each dielectric layer 136, is shown in Figure 10.

[0094] The interconnect substrate 130 is flexible, allowing it to be wound around the axis 105. Each dielectric layer 136 is, for example, a film of polymer material, such as polyimide. Several other materials are suitable for a flexible dielectric support, such as polyester, polyethylene polynaphthalate, or polyetherimide. The interconnect substrate 130 can be a flexible printed circuit board. The interconnect traces 135 are, for example, metallic traces, advantageously made of a malleable material, such as gold or copper.

[0095] Some of these conductive tracks 135 can connect the transducers 110A and / or 110B to the control circuits, for example, to carry control, power, and / or data signals between the control circuits and the transducers 110A and / or 110B. Some of these conductive tracks 135 can be connected to the electrodes of the transducers 110A and / or 110B. Other conductive tracks 135 can connect the control circuits to circuits, connectors, and / or components external or internal to the ultrasonic probe 100, for example, to another interconnecting substrate, to a flexible or rigid printed circuit board, for example, via cables.

[0096] The 130 interconnecting substrate can be extended by connecting tabs, blades, or strips, not The connecting strips can be part of the interconnect substrate 130 and positioned at the proximal end 130D of the interconnect substrate 130, i.e., the end furthest from the transducers 110A, 110B. The connecting strips can be connected to cables 140 to couple the interconnect substrate 130 to circuits, connectors, and / or components external or internal to the ultrasonic probe 100.

[0097] Preferably, the interconnecting substrate 130 extends in the longitudinal direction Z in one piece, i.e. in a single piece.

[0098] The interconnecting substrate 130 may comprise several portions along the longitudinal direction Z: - a first portion 131 which is substantially at the same axial level as the region of transducers 101; - a second portion 132 which is substantially at the same axial level as the control region 102; and - a third portion 134, or connecting portion, the second portion 132 being between the first portion 131 and the third portion 134.

[0099] The third portion 134 can be positioned axially at the level of the connection region 104.

[0100] The connecting strips can be arranged at the level of the third portion 134 of the interconnecting substrate 130.

[0101] The connecting strips and cables 140 can be arranged in the connector area 104.

[0102] The transducers 110A and 110B are positioned on the outer face 130A of the first portion 131 of the interconnecting substrate 130, and the control circuits and cables 140 are positioned on the outer face 130A or on the inner face 130B of the second portion 132 of the substrate interconnection substrate 130. Preferably, the transducers 110A, 110B and the control circuits 120 are axially spaced and positioned on two different faces, preferably two opposite faces, of the interconnection substrate 130. In other words, the transducers 110A, 110B and the control circuits are positioned in two axial portions and on two different faces, preferably opposite faces, of the interconnection substrate 130.

[0103] Furthermore, as illustrated in Figure 10, the first portion 131 of the interconnecting substrate 130 has a cylindrical shape whose cross-section (first section) is substantially circular. By cylindrical shape, we must understand a broad definition of a cylinder, namely a shape defined by a surface consisting of parallel lines connecting two parallel planes, the cross-section of the cylinder corresponding to the surface of either of the planes.

[0104] Preferably, the substantially circular cross-section of the first portion 131 of the interconnecting substrate 130 has flat sections beneath the transducers 110A and 110B, these flat sections being connected by rounded or arc-shaped sections. Thus, the cross-section of the first portion 131 can be likened to a polygonal section with at least N sides, which are by definition flat, N being the number of transducers, preferably with rounded sections between the sides. The first portion 131 of the interconnecting substrate 130 can therefore comprise N facets.

[0105] The second portion 132 of the interconnecting substrate 130 may have a prismatic cross-section (second section) substantially polygonal with several sides, at least M sides, where M is the number of control circuits, for example at least four sides. Preferably, the section The substantially polygonal shape of the second portion 132 includes rounded (arc-shaped) sections between its sides, which are flat by definition. In other words, the second portion 132 of the interconnecting substrate 130 has a multifaceted prismatic shape, preferably with rounded edges between the facets. The second portion 132 comprises M facets.

[0106] The first and second sections 131 and 132 have the same axis, corresponding approximately to axis 105.

[0107] A transitional portion of shape, not shown, can be provided between the first and second portions 131 and 132.

[0108] The transition portion of the shape has a form suitable for transforming: - a substantially circular section into a substantially polygonal section, and vice versa; or - a substantially polygonal section with N sides into a substantially polygonal section with M sides, where N is greater than M.

[0109] According to one embodiment, the number of facets N of the first portion 131 is greater than or equal to three times the number of facets M of the second portion 132, or greater than or equal to ten times the number of facets M of the second portion 132, or even greater than or equal to twenty times the number of facets M of the second portion 132.

[0110] In each of the first and second portions of the interconnecting substrate, the rounded portions between the sides, and thus the rounded edges between the facets, can form folding regions of the interconnecting substrate when it changes from a flat shape to a cylindrical or prismatic shape.

[0111] The control circuits can be positioned on the inner faces of the facets of the second portion 132 of the interconnection substrate 130. The transducers 110A and 110B are positioned on the cylindrical outer face of the first portion 131 of the interconnection substrate 130, for example on flat portions of the first portion 131.

[0112] The ultrasonic probe 100 may include electronic components, not shown, for example passive components, in the control region 102. The electronic components may be arranged axially away from the control circuits, for example between the control circuits and the connection region 104 of the ultrasonic probe 100. The electronic components may advantageously be positioned on the second portion 132 and on the inner face 130B of the interconnecting substrate 130, for example on the inner face of one or more facets.

[0113] Figure 10 shows the first portion 131 of the interconnecting substrate 130 as a cylinder with a substantially circular cross-section, preferably with flat sections, but this is not limiting. For example, the first portion 131 may be in the form of a cylinder with another cross-section, for example oval, or, as indicated above, in the form of a prism with more facets than the prism of the second portion, for example at least ten facets or at least fifty facets.

[0114] The ultrasonic probe 100 may also include stiffeners in the control region 102. The stiffeners are preferably distributed radially along the control circuits, with the interconnecting substrate 130 located between the stiffeners and the control circuits. The stiffeners serve, in particular, to protect the control circuits. For example, the stiffeners may have a thickness of approximately 50 µm. For example, the stiffeners may be made of a polymer, such as polyimide.

[0115] The stiffeners may each have one end facing the transducer region 101, which may be pointed or arrow-shaped, or any other shape suitable for constraining the interconnect substrate 130 to change its cross-sectional shape in the transition portion where present. For example, each stiffener may constrain the interconnect substrate 130 to flatten in the second portion 132 to obtain the flat sections to support the control circuits, or it may widen the flat sections of the first portion 131 to form the wider flat sections in the second portion 132.

[0116] The stiffeners can extend into the shape transition portion when present.

[0117] The ultrasonic probe 100 may further include a support element 106 around which the interconnecting substrate 130 is positioned.

[0118] Preferably, the interconnecting substrate 130 is not in contact with the support element 106, at least not along the entire length of the interconnecting substrate 130. Indeed, the space between the support element 106 and the interconnecting substrate 130 is at least partly occupied by elements, these elements being different depending on whether one is in the transducer region 101 or in the control region 102, or even in the shape transition region when it is present.

[0119] In the transducer region 101, the space between the support element 106 and the interconnecting substrate 130 can advantageously be filled, at least partially, by a sound-dampening material 114, which may be known by the English term "backing". The sound-dampening material 114 may have the advantage to attenuate the ultrasonic waves emitted by the transducers.

[0120] The space between the support element 106 and the interconnecting substrate 130 in the shape transition region, when present, can also be at least partially filled by the acoustic attenuation material 114. This can have the advantage of protecting the attachment, for example the gluing, of the transducers 110 on the interconnecting substrate 130 at the edge of the shape transition region.

[0121] In the control region 102, the control circuits, and possibly the electronic components, occupy at least part of the space between the support element 106 and the interconnecting substrate 130, i.e. the space between the support element 106 and the second portion 132 of the interconnecting substrate 130. All or part of the control circuits 120 may be in contact with the support element 106.

[0122] As an alternative, outside the transducer region 101, the acoustic attenuation material 114 can be extended under the rest of the interconnecting substrate 130 by a cylindrical piece of the same shape made of a different material than the acoustic attenuation material 114, for example metal or polymer.

[0123] The support element 106 may be made of a metallic material, for example, stainless steel, or of a non-metallic material, for example, a polymer or a plastic. The material of the support element 106 may, for example, be a biocompatible material. A layer 109 of a biocompatible material may be coated on the inner face of the support element 106. Preferably, the support element 106 is made of a material that ensures or improves the mechanical strength of the ultrasonic probe 100.

[0124] The support element 106 shown is a cylindrical tube with a circular cross-section whose axis corresponds substantially to the axis 105 of the ultrasonic probe 100. The interior of the tubular support element 106 defines an internal cavity 107. Other forms of support element can be considered, including polygonal, oval, symmetrical or asymmetrical, geometric or non-geometric cross-sectional profiles, the support element preferably being hollow.

[0125] The internal cavity 107 can be adapted to accommodate a guide wire, or another flexible element such as a tube ending in an inflatable balloon, or a sheath ending in a tool. The diameter D2 of the cavity is, for example, greater than 0.5 mm, for example, greater than or equal to 1.3 mm. A larger cavity diameter can be considered, but this may then require increasing the external diameter DI of the ultrasonic probe 100.

[0126] The second region 102 of the ultrasonic probe 100 can be covered by a protective sheath 108. The sheath 108 is preferably made of a biocompatible material. The sheath 108 serves, in particular, to protect the control circuits 120. The protective sheath 108 of the second region 102 is preferably an extension of the protective sheath 108 of the first region 101, and can thus also cover the first 101 and third 103 regions of the ultrasonic probe 100. The protective sheath 108 can also extend into at least part of the connection region 104.

[0127] Compared to a configuration in which the transducers are positioned radially around the control circuits, the configuration shown in Figures 8 to 10 allows for a reduction in the diameter of the ultrasonic probe. This can also help maintain an annular space between The interconnecting substrate and the support element in the transducer region can be used, for example, to insert acoustic attenuation material. Furthermore, compared to a configuration in which the transducers and control circuits are axially spaced but positioned on the same face of the interconnecting circuit, the configuration shown in Figures 8 to 10 allows the annular space between the interconnecting substrate and the support element to be used to position the control circuits in the control region. This annular space between the interconnecting substrate and the support element in the transducer region can advantageously be filled with acoustic attenuation material. Moreover, the configuration shown in Figures 8 to 10 is particularly advantageous because it allows the interconnecting substrate 130 to be contained within a cylindrical envelope whose diameter remains constant along portions 131 and 132.In other words, the unrolled interconnect substrate has the same width along its entire length, and for example does not require any adjustments (folds or partial cutting for example).

[0128] The ultrasound probe, depending on the embodiment, can find applications in the field of diagnostics (pre-treatment or post-treatment diagnosis), or intravascular ultrasound treatment, the ultrasound probe being able, for example, to be integrated into a catheter.

[0129] Various embodiments and variations have been described. A person skilled in the art will understand that some features of these various embodiments and variations could be combined, and other variations will become apparent to a person skilled in the art.

[0130] Finally, the practical implementation of the described embodiments and variants is within the reach of the person in the trade based on the functional specifications given above.

Claims

DEMANDS 1. Ultrasonic probe (100) extending in a longitudinal direction (Z) along an axis (105), the ultrasonic probe comprising: - an interconnection substrate (130) comprising a first face (130A) and a second face (130B) opposite the first face; - a first number (NA) of first ultrasonic transducers (110A) having a first elevation (HA) and arranged on the first face (130A) of the interconnecting substrate (130); and - a second number (NB) of second ultrasonic transducers (110B) having a second elevation (HB) and arranged on the first face (130A) of the interconnecting substrate (130), next to, along the axis (105), the first ultrasonic transducers (110A), wherein the first ultrasonic transducers (110A) are broadband ultrasonic transducers configured to emit and receive first ultrasonic waves centered on an operating frequency that can vary between a low operating frequency within a first range and a high operating frequency within a second range, the low operating frequency being lower than the high operating frequency.

2. Ultrasonic probe (100) according to claim 1, wherein the first range is from 30 MHz to 80 MHz and the second range is from 60 MHz to 150 MHz.

3. Ultrasonic probe (100) according to claim 2, wherein the first number (NA) and the first elevation (HA) of the first ultrasonic transducers (110A) are optimized for operation of the first ultrasonic transducers (110A) at the high operating frequency.

4. Ultrasonic probe (100) according to any one of claims 2 and 3, wherein the second ultrasonic transducers (110B) are broadband ultrasonic transducers or fixed operating frequency ultrasonic transducers.

5. Ultrasonic probe (100) according to any one of claims 2 to 4, wherein the second number (NB) of the second ultrasonic transducers (110B) is optimized for operation of the second ultrasonic transducers (110B) at the low operating frequency.

6. Ultrasonic probe (100) according to any one of claims 2 to 4, wherein the first number (NA) is equal to the second number (NB).

7. Ultrasonic probe (100) according to claim 6, wherein each first ultrasonic transducer (110A) is electrically connected with one of the second ultrasonic transducers (110B).

8. Ultrasonic probe (100) according to any one of claims 2 to 7, wherein the second elevation (HB) of the second ultrasonic transducers (110B) is chosen so that the sum of the first and second elevations (HA, HB) is optimized for operation of the first and second ultrasonic transducers (110A, 110B) at the low operating frequency.

9. Ultrasonic probe (100) according to any one of claims 2 to 7, wherein the second elevation (HB) is equal to the first elevation (HA).

10. Ultrasonic probe (100) according to any one of claims 1 to 9, wherein the first ultrasonic transducers (110A) and the second ultrasonic transducers (110B) are arranged in a first region (101) of the ultrasonic probe (100), the ultrasonic probe (100) further comprising at least one control circuit disposed in a second region (102) of the ultrasonic probe (100) and on the first face (130A) or the second face (130B) of the interconnecting substrate (130), the second region (102) being distinct from the first region (101).

11. Ultrasonic probe (100) according to claim 10, wherein the first face (130A) is an external face of the interconnecting substrate (130) and the second face (130B) is an internal face of the interconnecting substrate (130).

12. Ultrasonic probe (100) according to claim 10 or 11, wherein the second region (102) is axially offset with respect to the first region (101).

13. Ultrasonic probe (100) according to any one of claims 1 to 12, wherein the ultrasonic probe has an external cylindrical shape around the axis (105), the first transducers (110A) being distributed, for example regularly distributed, around the axis (105) and the second transducers (110B) being distributed, for example regularly distributed, around the axis (105).

14. Use of an ultrasonic probe (100) according to any one of claims 1 to 13, comprising, in a first mode of operation, the emission of first ultrasonic waves (USA+USB) by the first and second ultrasonic transducers (110A, 110B), and, in a second mode of operation, the emission of second ultrasonic waves (USA) only by the first ultrasonic transducers (110A).

15. Use according to claim 14, wherein the first ultrasonic transducers (110A) are according to claim 2, wherein, in the first operating mode, the first ultrasonic transducers (110A) are controlled to emit the first ultrasonic waves (USA+USB) at the low operating frequency, and wherein, in the second operating mode, the first ultrasonic transducers (110A) are controlled to emit the first ultrasonic waves (USA+USB) at the high operating frequency.

16. Use according to claim 13 or 14, further comprising, in a third mode of operation, the emission of third ultrasonic waves (USB) only by the second ultrasonic transducers (110B).

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