Ultrasound probe and intravascular ultrasound imaging procedure

Abstract

Ultrasound Probe and Intravascular Ultrasound Imaging Method. This description relates to an ultrasound probe (100) extending longitudinally along an axis (105). The ultrasound probe comprises an interconnecting substrate (130) having a first face and a second face opposite the first face. A first number of first ultrasound transducers (110A) having a first elevation (HA) and arranged on the first face of the interconnecting substrate (130), and a second number of second ultrasound transducers (110B) having a second elevation (HB) and arranged on the first face of the interconnecting substrate (130), adjacent to the first ultrasound transducers (110A) along the axis (105). Figure for the abstract: Fig. 4

Description

Title of the invention: Ultrasound probe and method for intravascular ultrasound imaging. Technical field

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

[0002] An example of the application of such an ultrasound probe relates to 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 for evaluating 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 particular elements of the vessels.The reflected ultrasound waves are captured by the ultrasound transducers, which transmit electrical signals representative of the captured ultrasound waves to a processing device. This device processes 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 dimensions, 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 so-called 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 elevation of the ultrasonic transducers, this elevation increasing as the frequency of the ultrasonic waves emitted decreases. Since the elevation of ultrasonic transducers is fixed, broadband ultrasonic transducers can only be optimized for a single frequency, so the resolution of the obtained 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 connected electrically with one of the second ultrasonic transducers.

[0015] According to one embodiment, the second elevation of the second transducers ultrasound is chosen so that the sum of the first and second elevations is optimized for operation of the first and second ultrasonic transducers at 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 disposed in a first region of the ultrasonic probe, the ultrasonic probe further comprising at least one control circuit disposed 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 with respect 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 above, 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 accompanying figures, among which:

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

[0026] [Fig.2] is an enlarged view of a part of the probe of [Fig.1] shown in spread-out form in a plane;

[0027] [Fig.3] is a partial and schematic perspective view of another known ultrasonic probe;

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

[0029] [Fig.5] is an enlarged view of a part of the probe of [Fig.4] shown spread out in a plane;

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

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

[0032] [Fig. 9] is a side view of the ultrasonic probe of [Fig. 8]; and

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

[0034] The same elements have been designated by the same reference numerals in the different figures. In particular, the 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 are 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, as the described embodiments are compatible with all or most common control circuits for ultrasonic transducers.

[0036] Unless otherwise specified, when referring to two interconnected 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 taken to mean "electrically insulating" and "electrically conductive," respectively.

[0037] In the following description, 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 Orientation qualifiers, such as the terms "horizontal", "vertical", etc., refer, unless otherwise specified, to the orientation of the figures in a normal position of use.

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

[0039] In the following description, when referring to a longitudinal direction, it refers to a direction parallel to the axis of the ultrasonic probe. It 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 in a plane perpendicular to the longitudinal direction. 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, references to a transducer refer to an ultrasonic transducer, and unless otherwise specified, references to a probe refer to 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 array of ultrasonic transducers (in particular, the number of ultrasonic transducers in the array, the elevation of the ultrasonic transducers in the array, etc.)) 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] Fig. 1 is a partial and 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 about 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 ultrasonic transducers 11 are distributed around the axis 105. The ultrasonic transducers 11 are distributed around the axis 105 and are identical.

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

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

[0046] The network of ultrasonic transducers 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 pitch 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 aperture for the deflection direction or the active direction, equal to the product of N and p.

[0047] In the embodiment illustrated in [Fig. 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 ultrasonic 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 ultrasonic transducers 11 around the axis 105 to scan an entire blood vessel.

[0048] The distribution of the ultrasound transducers 11 around the axis 105 allows for obtaining 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 above, 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 the elevation H required to achieve optimal resolution increase as the operating frequency decreases. Typically, the step size p and the elevation H are therefore chosen according to the operating frequency of the probe 10 to obtain the optimal resolution. There are also other considerations to take 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 the width e. This is because the gap g can be constant regardless of the number N of transducers 11, as it may be imposed by the manufacturing process of the transducers 11, in particular the cutting step used to define the transducers 11. This therefore results in a decrease in the active area (equal to the product of the width e and the elevation H) of each transducer 11 and thus a decrease in the signal-to-noise ratio of the transducer 11.Therefore, a compromise must be found between signal-to-noise ratio and resolution for determining 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 lower 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] Transducer bandwidth is usually limited. Generally, 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 to be the probe's operating frequency. An ultrasonic transducer is generally 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 ultrasonic images are required at different operating frequencies.

[0051] There are so-called broadband ultrasonic transducers whose operating frequency can be varied within a range between a low 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 the probe 100 of Figure 4, shown spread out in a plane. Figures 6 and 7 are partial, schematic perspective views of alternative embodiments of the ultrasonic probe 100 of Figure 4.

[0053] The ultrasound probe 100 can be integrated into a catheter. The ultrasound probe 100 can be part of an ultrasound imaging device (not shown), for example, an intravascular ultrasound imaging device, or IVUS device, which generally includes a catheter, a guidewire, and / or a guide catheter, and which 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 can 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 processing device adapted to control the ultrasound probe to produce emitted ultrasound waves, and to process ultrasound waves received by the ultrasound probe to produce a corresponding image.

[0054] The ultrasonic probe 100 has a substantially cylindrical external shape with a circular base about an axis 105, parallel to the Z direction. To allow it to be inserted into a space with a small cross-section or diameter, the external diameter DI of the ultrasonic 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 ultrasonic 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 [Fig. 2] are followed by the suffix A when used for the first ultrasonic transducer array and for the first 110A ultrasonic transducers, and by the suffix B when used for the second ultrasonic transducer array and for 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, and the second ultrasonic transducer array comprises NB ultrasonic transducers. 110B, and the second ultrasonic transducers 110A have an elevation HB and a step size pB. The total elevation HT is called the sum of the elevations HA and HB.

[0057] According to one embodiment, the first ultrasonic transducer array 110A 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 [Fig. 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 [Fig. 3], i.e., optimized to operate at the high operating frequency.

[0059] According to one embodiment, the second ultrasonic transducer array 110B also comprises 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 comprises ultrasonic transducers with a fixed operating frequency, preferably equal to the low operating frequency. The frequency band, measured at -6 dB, of the spectrum of ultrasonic waves emitted by ultrasonic transducers with a 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 represented in [Fig.1], i.e. optimized to operate at the low operating frequency.

[0061] The 110A and / or 110B broadband ultrasonic transducers can be microelectromechanical systems, or MEMS (Micro-Electro-Mechanical System), implementing microelectronic production technologies. A MEMS-type transducer generally consists of a deformable membrane suspended above a cavity. In one embodiment, the deformable membrane is displaced or deformed by capacitive effect using an electrode attached to the membrane and an electrode separated by the cavity. This type of ultrasonic transducer is known by the acronym CMUT (Capacitive Micro-Ultrasonic Transducer). A micro-machined ultrasonic transducer (PMUT) is a micro-machined ultrasonic capacitive transducer, also known as a membrane capacitive transducer. In another embodiment, the deformable membrane is displaced or deformed by piezoelectricity 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, for Piezoelectric Micro-machined Ultrasonic Transducer.

[0062] When the ultrasonic probe 100 includes an array of fixed operating frequency transducers 110B, the ultrasonic transducers may be CMUT type transducers, 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 transducer network 110A, 110B can include ultrasonic transducers of different types.

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

[0065] All or part of the ultrasonic waves emitted by the transducers 110A, 110B may be reflected by particular elements of the medium into which the ultrasonic probe 100 is introduced, for example, particular elements of a vessel. The reflected ultrasonic waves may be received by the ultrasonic transducers 110A, 110B. The electrical signals corresponding to the reflected ultrasonic waves may 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 particular elements.

[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 broadband ultrasonic transducers are driven at the low operating frequency. The second 110B ultrasonic transducers, when they The broadband transducers are also controlled at the low operating frequency. The second ultrasonic transducers 110B, when at a fixed operating frequency, emit ultrasonic waves at the 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 ultrasonic transducers 110A of the first array of ultrasonic transducers 110A are used; the ultrasonic transducers 110B of the second array of ultrasonic transducers 110B are not used. According to one embodiment, the first broadband ultrasonic transducers 110A are controlled 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] Ultrasonic images with optimal resolution at two operating frequencies can advantageously be obtained with the same ultrasonic probe.

[0070] In the third operating mode, only the ultrasonic transducers 110B of the second ultrasonic transducer array 110B are used; the ultrasonic transducers 110A of the first ultrasonic transducer array 110A are not used. According to 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. Advantageously, the HB elevation is 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 substantially a cylinder with axis 105 and diameter DI. This is not, however, a limitation; the transducers 110A and 110B may 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 differences g A and g B between two transducers 110A and 110B generally depend on the cutting process used to separate the transducers and are typically identical.The gaps g A and g B 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 Dl. This is not, however, a limitation; the transducers can be arranged to image an angular sector of 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 [Fig. 4], only the first ultrasonic transducers 110A are broadband, while the second ultrasonic transducers 110B are fixed-frequency transducers. According to one embodiment, in [Fig. 4], the elevation HA is different from the elevation HB. In the embodiment illustrated in [Fig. 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 [Fig. 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 array of ultrasonic transducers 110B is equal to the pitch that would be chosen for the ultrasonic probe 10 shown in [Fig. 3].l], that is, optimized to operate at the low operating frequency. The step size pA is then different from the step size pB. The probe 100 according to the embodiment illustrated in [Fig.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 represented in [Fig.3], that is, optimized to operate at the high operating frequency, and that the elevation HT is equal to the elevation that would be chosen for the ultrasonic probe 10 represented in [Fig.l], that is, optimized to operate at the low operating frequency.

[0073] In the embodiment illustrated in [Fig. 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. In the case where NA is greater than NB, the processing device of the imaging device may perform a composition of the received signals (weighting, delay, and summation) by two or more transducers 110A that extend longitudinally, i.e., in a direction parallel to the axis 105, in whole or in part, each transducer 110B in order 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 imaging device's processing unit can perform a composition of the received signals (weighting, delay, and summation) by two or more 110B transducers that 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 [Fig. 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 processing device of the imaging device. Alternatively, in the embodiment illustrated in [Fig. 4], NA is chosen to be equal to NB and transducer 110A is electrically connected to the 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 the adjacent transducer 110B are electrically connected together is advantageous because the number of connections in the first and second networks is then reduced to NA connections.As an alternative, in the embodiment illustrated in [Fig.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 and longitudinally offset using the second and third operating modes.

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

[0076] In the variant illustrated in [Fig. 7], the first ultrasonic transducers 110A and the second ultrasonic transducers 110B are broadband ultrasonic transducers over the same frequency range. Furthermore, in [Fig. 7], the HA elevation is substantially equal to the HB elevation. In this embodiment, it can be It is more difficult to obtain both a HA elevation equal to the elevation that would be chosen for the ultrasonic probe 20 shown in [Fig. 3], i.e., optimized to operate at the high operating frequency, and a HT elevation equal to the elevation that would be chosen for the ultrasonic probe 10 shown in [Fig. 1], i.e., optimized to operate at the low operating frequency. However, this variant has the advantage that the first ultrasonic transducers 110A can be identical to the second ultrasonic transducers 110B. The manufacturing process of probe 100 is then simplified. In addition, 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. Furthermore, in [Fig.[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 [Fig. 3], i.e., optimized to operate 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 processing unit of the imaging device. The probe 100 according to the variant illustrated in [Fig. 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 ultrasonic transducers 110A are broadband ultrasonic transducers. Preferably, 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 [Fig. 3], i.e., optimized to operate at the high operating frequency. The second ultrasonic transducers 110B can be fixed-frequency transducers (embody illustrated in [Fig. 4]) or broadband ultrasonic transducers (embodyments illustrated in Figures 6 and 7). The number NB of ultrasonic transducers 110B can be chosen to be equal to the number N that would be chosen for the ultrasonic probe 10 shown in [Fig. 3].l], i.e., optimized to operate at the low operating frequency, or be chosen equal to the number NA, which then allows each ultrasonic transducer 110B to be electrically connected together with the adjacent ultrasonic transducer 110A. The elevation HB of the second array of ultrasonic transducers 110B can be chosen so that the elevation HT is equal to the elevation H that would be chosen for the ultrasonic probe 10 shown in [Fig.1] (an embodiment illustrated in [Fig.6]), i.e., optimized to operate at the low operating frequency, or be chosen substantially equal to the elevation HA (an embodiment illustrated in [Fig.7]).

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

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

[0080] In the following description, a distal end refers to an end through which the ultrasound probe, or imaging device, is introduced into the medium to be analyzed, and a proximal end refers to an end opposite the distal end. The proximal end generally corresponds to an 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. According to 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 [Fig. 10], each ultrasonic transducer 110A is very schematically represented 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 may comprise two electrodes, not shown.

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

[0084] The ultrasonic probe 100 further comprises an electrical component, for example an inductor, and / or an 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 (Application-Specific Integrated Circuit), or any other electronic circuit suitable for controlling one or more transducers 110A, 110B.

[0085] The control circuits can be configured to select some of the transducers 110A, 110B to be used for the transmission / reception of ultrasonic waves, to transmit control signals to the transducers selected to generate and transmit ultrasonic waves, and / or to accept or even amplify return signals from the selected transducer elements when the latter 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 several 110A and / or 110B transducers, for example, to control between three and thirty 110A and / or 110B transducers. In other words, there may be fewer control circuits than transducers. Four control circuits are 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 level of the transducers 110, and a proximal end 130D which is opposite the distal end 130C.

[0092] The interconnecting 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 interconnecting 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 one another and arranged in and / or on a dielectric layer 136. The interconnecting substrate 130 may be multilayered and comprise a stack of two or more dielectric layers 136. dielectrics 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. As an 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 [Fig.10].

[0094] The interconnecting substrate 130 is flexible, so that it can be wound around the axis 105. Each dielectric layer 136 is, for example, in the form of a film of polymer material, for example, polyimide. Several other materials can be suitable for a flexible dielectric support, for example, polyester, polyethylene polynaphthalate, or polyetherimide. The interconnecting substrate 130 can be a flexible printed circuit board. The interconnecting tracks 135 are, for example, metallic tracks, advantageously made of a malleable material, for example, 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 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 interconnecting substrate 130 can be extended by connecting tabs, blades, or strips, not shown. The connecting strips can be part of the interconnecting substrate 130 and positioned at the proximal end 130D of the interconnecting substrate 130, i.e., the end furthest from the transducers 110A, 110B. The connecting strips can be connected to cables 140 to couple the interconnecting 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, that is to say in one 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 the cables 140 can be arranged in the connection 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 interconnecting 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 interconnecting 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 interconnecting substrate 130.

[0103] Furthermore, as illustrated in [Fig. 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, a broad definition of a cylinder is to be understood, 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 one or the other of the planes.

[0104] Preferably, the substantially circular cross-section of the first portion 131 of the interconnecting substrate 130 has flat portions beneath the transducers 110A, 110B, the flat portions being connected by rounded or arc-shaped portions. Thus, the cross-section of the first portion 131 can be likened to a polygonal cross-section with at least N sides, which are by definition flat, N being the number of transducers, preferably with rounded portions 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) that is 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 substantially polygonal cross-section of the second portion 132 has rounded (arc-shaped) portions between the sides, which are by definition flat. 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 portions 131 and 132 have the same axis, corresponding substantially to axis 105.

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

[0108] The transition portion of shape has a shape adapted to transform: - 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 passes from a flat shape to a cylindrical or prismatic shape.

[0111] The control circuits can be positioned on the internal faces of the facets of the second portion 132 of the interconnecting substrate 130. The transducers 110A and 110B are positioned on the cylindrical external face of the first portion 131 of the interconnecting 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 at a distance 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] The first portion 131 of the interconnecting substrate 130 is represented in [Fig. 10] as a cylinder of substantially circular cross-section, preferably with flat portions, but this is not limiting. For example, the first portion 131 may be in the form of a cylinder having another cross-section, for example oval, or, as indicated above, in the form of a prism having 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 further 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 an end facing the transducer region 101, which may have a pointed or arrow-shaped form, or any other shape suitable for constraining the interconnect substrate 130 to change its cross-sectional shape in the shape transition portion when 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 to 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 it is 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 an acoustic attenuation material 114, which may be known by the English term "backing". The acoustic attenuation material 114 may have the advantage of attenuating 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 a portion of the space between the support element 106 and the interconnecting substrate 130, i.e. the space included 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 be, for example, 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 Taxe 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, in particular 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 allow the passage of 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 notably protects 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 at least into a portion of the connection region 104.

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

[0128] The ultrasound probe according to the embodiments 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 certain 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 embodiments and variants described is within the reach of a person skilled in the art, based on the functional indications given above.

Claims

Demands

1. Ultrasonic probe (100) extending in a longitudinal direction (Z) along an axis (105), the ultrasonic probe comprising: - an interconnecting 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).

2. Ultrasonic probe (100) according to claim 1, wherein the first ultrasonic transducers (110A) 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.

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 operating mode, 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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