Patent Description:
Minimally invasive surgeries have been enabled by the advance of various medical technologies. For example, diagnostic and therapeutic ultrasound catheters have been designed for imaging inside areas of the human body. In the cardiovascular system, two common diagnostic ultrasound methods are intravascular ultrasound (IVUS) and intra-cardiac echocardiography (ICE). Typically a single rotating transducer or an array of transducer elements is used to transmit ultrasound at the tips of the catheters. The same transducers (or separate transducers) are used to receive echoes from the tissue. A signal generated from the echoes is transferred to a console which allows for the processing, storing, display, or manipulation of the ultrasound-related data.

IVUS catheters are typically used in the large and small blood vessels (arteries or veins) of the body, and are almost always delivered over a guidewire having a flexible tip. ICE catheters are usually used to image chambers of the heart and surrounding structures, for example, to guide and facilitate medical procedures, such as transseptal lumen punctures, left atrial appendage closures, atrial fibrillation ablation, and valve repairs. Commercially-available ICE catheters are not designed to be delivered over a guidewire, but instead have distal ends which can be articulated by a steering mechanism located in a handle at the proximal end of the catheter. For example, an ICE catheter may be inserted through the femoral or jugular artery when accessing the anatomy, and steered in the heart to acquire images necessary to the safety of the medical procedures.

An ICE catheter typically includes an ultrasound imaging component that generates and receives acoustic energy. The imaging component is encased in a tip assembly located at a furthest distal tip of the catheter. The tip assembly is covered with acoustic adhesive materials. An electrical cable is connected to the imaging component and extends through the core of the body of the catheter. The electrical cable may carry control signals and echo signals to facilitate imaging of the heart anatomy. The device may provide rotational, <NUM>-way, or <NUM>-way steering mechanisms such that anterior, posterior, left, and/or right views of the heart anatomy may be imaged.

Surface imaging components may include a matrix array of ultrasound transducers fabricated with an application-specific integrated circuit (ASIC) coupled to a backside of the matrix array opposite a front side of the matrix array where ultrasound waves are emitted. The matrix array can include a large number of ultrasound transducers (e.g., hundreds of ultrasound transducers). The matrix array can provide high-quality two-dimensional (2D) and three-dimensional (3D) imaging. The ASIC can be pitch-matched to the ultrasound transducers. The ASIC is typically formed from a silicon material. The ASIC can perform micro-beamforming on the ultrasound echo signals collected by the ultrasound transducers. The surface imaging components can include a de-matching layer and a backing layer to eliminate or reduce unwanted acoustic distortions. The de-matching layer typically has a thickness of about a quarter of a wavelength of the ultrasound waves. The de-matching layer can reflect forward ultrasound waves travelling toward the backside of the matrix array. The backing layer is typically formed from a polymeric material and has a thickness less than <NUM> centimeter (cm). The backing layer can disperse or dampen remaining backward travelling ultrasound waves.

For a given material, the degree of expansion during heating and contraction during cooling is represented by a coefficient of thermal expansion (CTE). The silicon material of the ASIC and the polymeric material of the backing layer have highly differentiating CTEs. In surface transducers, the backing layer can be made sufficiently thick so that the two continuous layers (e.g., the ASIC and the backing layer) of materials with highly differentiating CTEs may not cause surface transducers to warp or bend under thermal excursions, which may vary from about -<NUM> degree Celsius (°C) to about <NUM>.

In order to fabricate matrix array transducers for catheter imaging, the form factor of the matrix array transducers is required to be significantly reduced. For example, catheter imaging components may be limited to a diameter about <NUM> millimeter (mm) for ICE devices and less than <NUM> for IVUS devices. Thus, the backing layer in a catheter imaging component is required to be significantly thinner than a surface imaging component. When the backing layer is thin, the varying CTEs between the ASIC and the backing layer can cause the catheter imaging component to warp or bend under thermal excursions. The bending can result in damages to the imaging component and provide poor reliability.

<CIT> discloses a system for Volume scanning along different planes using angling of elements. Rather than orthogonal dicing of a slab, kerfs are formed at non-parallel and non-perpendicular angles to the azimuth axis of the array or longitudinal axis of the slab. Apertures formed from selected groups of the angled elements and/or parts of angled elements may be used to steer along planes that extend at an angle of <NUM> degrees or more away from the azimuth or longitudinal axis. By walking the aperture, different parallel planes are scanned with a one-dimensional array of elements.

<CIT> discloses an ultrasonic probe comprising: a semiconductor substrate having a plurality of CMUT cells formed on its surface; an acoustic lens that is provided on the front face side of the CMUT cells; and a backing layer that is provided on the rear face side of the semiconductor substrate. The backing layer is formed by a first backing layer that makes contact with the semiconductor substrate, and a second backing layer that is provided on the rear face side of the backing layer. The acoustic impedance of the backing layer is set based on the sheet thickness of the semiconductor substrate.

<CIT> discloses an ultrasonic probe wherein the warpage of a CMUT due to thermal stress produced at the joint between a backing layer and the CMUT is minimized. To accomplish this the ultrasonic probe is provided with: a CMUT having vibratory elements; a backing layer adhered to the rear side of the ultrasonic transmission surface of the CMUT; and a thermal-stress balancing member to be adhered to the backing layer while being disposed facing the CMUT in such a manner that the backing layer is sandwiched therebetween so as to minimize the warpage of the CMUT due to thermal stress produced between the CMUT.

The invention provides devices, systems, and related methods for providing intraluminal imaging components that overcome the limitations associated with previous designs.

Embodiments of the present disclosure provide an intraluminal imaging component with improved stability and reliability by reducing or eliminating thermal stress in the imaging component during thermal excursions. The imaging component includes an array of ultrasound transducer elements and a backing material layer coupled to opposite sides of an integrated circuit (IC) layer composed of a semiconductor material. In one embodiment, the thermal stress is reduced by selecting a backing material with a coefficient of thermal expansion (CTE) closer to the CTE of the semiconductor material of the IC layer but still provide sufficient acoustic attenuation. In another embodiment, the thermal stress is eliminated by adding an additional support layer with a similar material or the same material as the semiconductor material of the IC layer. The support layer is coupled to the backing layer opposite the IC layer. The addition of the support layer enables the backing layer to be constructed from a standard or commonly used backing material without compromising acoustic attenuation performance.

In one embodiment, an imaging catheter assembly is provided. The imaging catheter assembly includes a flexible elongate member including a distal portion and a proximal portion; and an imaging component coupled to the distal portion of the flexible elongate member, wherein the imaging component includes: an integrated circuit (IC) layer that includes a semiconductor material; an array of ultrasound transducer elements coupled to a first side of the IC layer; and a backing layer coupled to a second side of the IC layer opposite the first side, wherein the backing layer includes a backing material, and wherein a coefficient of thermal expansion (CTE) difference between the semiconductor material and the backing material is less than <NUM> parts per million per degree Centigrade (ppm/C).

The backing material is selected from the group of materials consisting of high density particles in a hard epoxy matrix. The backing material includes a CTE between <NUM> parts per million per degree Centigrade (ppm/C) and <NUM> ppm/C. In some embodiments, the backing layer provides an acoustic attenuation between <NUM> decibels per millimeter (dB/mm) to <NUM> dB/mm. In some embodiments, the backing layer includes a thickness less than <NUM> millimeter (mm). In some embodiments, the IC layer includes a thickness less than <NUM> millimeter (mm). In some embodiments, the imaging component further includes a support layer coupled to the backing layer opposite the IC layer. In some embodiments, the support layer is configured to balance a CTE-based stress in the imaging component. In some embodiments, the support layer includes a same material as the semiconductor material of the IC layer.

In one embodiment, an imaging catheter assembly is provided. The imaging catheter assembly includes a flexible elongate member including a distal portion and a proximal portion; and an imaging component coupled to the distal portion of the flexible elongate member, wherein the imaging component includes: an integrated circuit (IC) layer that includes a first material; an array of ultrasound transducer elements coupled to a first side of the IC layer; a backing layer coupled to a second side of the IC layer opposite the first side; and a support layer coupled to the backing layer opposite the IC layer, wherein the support layer includes a second material, and wherein a coefficient of thermal expansion (CTE) difference between the first material and the second material is less than <NUM> parts per million per degree Centigrade (ppm/C).

In some embodiments, the first material and the second material are the same material. In some embodiments, the first material and the second material include silicon. In some embodiments, the backing layer includes a thickness less than <NUM> millimeter (mm). In some embodiments, the support layer includes a thickness less than <NUM> millimeter (mm). In some embodiments, the IC layer includes a thickness less than <NUM> millimeter (mm).

In one embodiment, a method of manufacturing an imaging catheter assembly is provided. The method includes forming an imaging component by: providing an integrated circuit (IC) layer that includes a semiconductor material; coupling an array of ultrasound transducer elements to a first side of the IC layer; and coupling a backing layer to a second side of the IC layer opposite the first side, wherein the backing layer includes a backing material, and wherein a coefficient of thermal expansion (CTE) difference between the semiconductor material and the backing material is less than <NUM> parts per million per degree Centigrade (ppm/C); and coupling the imaging component to a distal portion of a flexible elongate member.

The backing material is selected from the group of materials consisting of dense particles in epoxy matrices. In some embodiments, the backing layer includes a thickness less than <NUM> millimeter (mm). In some embodiments, the IC layer includes a thickness less than <NUM> millimeter (mm). In some embodiments, the method further comprises coupling a support layer to the backing layer opposite the IC layer. In some embodiments, the support layer includes a same material as the semiconductor material of the IC layer.

In one embodiment, a method of manufacturing an imaging catheter assembly is provided. The method includes forming an imaging component by: providing an integrated circuit (IC) layer that includes a first material; coupling an array of ultrasound transducer elements to a first side of the IC layer; coupling a backing layer to a second side of the IC layer opposite the first side; and coupling a support layer to the backing layer opposite the IC layer, wherein the support layer includes a second material, wherein a coefficient of thermal expansion (CTE) difference between the first material and the second material is less than <NUM> parts per million per degree Centigrade (ppm/C); and coupling the imaging component to a distal portion of a flexible elongate member.

For example, while the intraluminal system is described in terms of cardiovascular imaging, it is understood that it is not intended to be limited to this application. The system is equally well suited to any application requiring imaging within a confined cavity.

<FIG> is a schematic diagram of an intraluminal imaging system <NUM> according to embodiments of the present disclosure. The system <NUM> may include an intraluminal device <NUM>, a connector <NUM>, a control and processing system <NUM>, such as a console and/or a computer, and a monitor <NUM>. The intraluminal device <NUM> includes a tip assembly <NUM>, a flexible elongate member <NUM>, and a handle <NUM>. The flexible elongate member <NUM> includes a distal portion <NUM> and a proximal portion <NUM>. The distal end of the distal portion <NUM> is attached to the tip assembly <NUM>. The proximal end of the proximal portion <NUM> is attached to the handle <NUM> for example, by a resilient strain reliever <NUM>, for manipulation of the intraluminal device <NUM> and manual control of the intraluminal device <NUM>. The tip assembly <NUM> can include an imaging component with ultrasound transducer elements and associated circuitry. The handle <NUM> can include actuators <NUM>, a clutch <NUM>, and other steering control components for steering the intraluminal device <NUM>. In an embodiment, the intraluminal device <NUM> is an ICE device.

The handle <NUM> is connected to the connector <NUM> via another strain reliever <NUM> and an electrical cable <NUM>. The connector <NUM> may be configured in any suitable configurations to interconnect with the processing system <NUM> and the monitor <NUM> for processing, storing, analyzing, manipulating, and displaying data obtained from signals generated by the imaging core at the tip assembly <NUM>. The processing system <NUM> can include one or more processors, memory, one or more input devices, such as keyboards and any suitable command control interface device. The processing system <NUM> can be operable to facilitate the features of the intraluminal imaging system <NUM> described herein. For example, the processor can execute computer readable instructions stored on the non-transitory tangible computer readable medium. The monitor <NUM> can be any suitable display device, such as liquid-crystal display (LCD) panel or the like.

In operation, a physician or a clinician advances the flexible elongate member <NUM> into a vessel within a heart anatomy. The physician or clinician can steer the flexible elongate member <NUM> to a position near the area of interest to be imaged by controlling the actuators <NUM> and the clutch <NUM> on the handle <NUM>. For example, one actuator <NUM> may deflect the tip assembly <NUM> and the distal portion <NUM> in a left-right plane and the other actuator <NUM> may deflect the tip assembly <NUM> and the distal portion <NUM> in an anterior-posterior plane. The clutch <NUM> provides a locking mechanism to lock the positions of the actuators <NUM> and in turn the deflection of the flexible elongate member <NUM> while imaging the area of interest.

The imaging process may include activating the ultrasound transducer elements on the tip assembly <NUM> to produce ultrasonic energy. A portion of the ultrasonic energy is reflected by the area of interest and the surrounding anatomy, and the ultrasound echo signals are received by the ultrasound transducer elements. The connector <NUM> transfers the received echo signals to the processing system <NUM> where the ultrasound image is reconstructed and displayed on the monitor <NUM>. In some embodiments, the processing system <NUM> can control the activation of the ultrasound transducer elements and the repletion of the echo signals. In some embodiments, the processing system <NUM> and the monitor <NUM> may be part of the same system.

The system <NUM> may be utilized in a variety of applications such as transseptal lumen punctures, left atrial appendage closures, atrial fibrillation ablation, and valve repairs and can be used to image vessels and structures within a living body. In addition, the tip assembly <NUM> may include any suitable physiological sensor or component for diagnostic, treatment, and/or therapy. For example, the tip assembly can include an imaging component, an ablation component, a cutting component, a morcellation component, a pressure-sensing component, a flow-sensing component, a temperature-sensing component, and/or combinations thereof.

<FIG> is a schematic diagram of a portion of the intraluminal device <NUM> according to embodiments of the present disclosure. The tip assembly <NUM> and the flexible elongate member <NUM> are shaped and sized for insertion into vessels of a patient body. The flexible elongate member <NUM> can be composed of any suitable material, such as Pebax® polyether block amides. The distal portion <NUM> and the proximal portion <NUM> are tubular in shape and may include one or more lumens extending along a length of the flexible elongate member <NUM>. In some embodiments, one lumen (e.g., a primary lumen) may be sized and shaped to accommodate an electrical cable <NUM> (shown in <FIG>) interconnecting the tip assembly <NUM> and the connector <NUM> for transferring echo signals obtained from the transducer elements. In addition, the lumen may be shaped and sized to accommodate other components for diagnostic and/or therapy procedures. In some other embodiments, one or more lumens (e.g., secondary lumens) may be sized and shaped to accommodate steering wires, for example, extending from the distal portion <NUM> to the handle <NUM>. The steering wires may be coupled to the actuators <NUM> and the clutch <NUM> such that the flexible elongate member <NUM> and the tip assembly <NUM> are deflectable based on actuations of the actuators <NUM> and the clutch <NUM>. Dimensions of the flexible elongate member <NUM> can vary in different embodiments. In some embodiments, the flexible elongate member <NUM> can be a catheter having an outer diameter between about <NUM> and about <NUM> French (Fr) and can have a total length <NUM> between about <NUM> centimeters (cm) to about <NUM>, where the proximal portion <NUM> can have a length <NUM> between about <NUM> to about <NUM> and the distal portion <NUM> can have a length <NUM> between about <NUM> to about <NUM>.

<FIG> is a schematic diagram of the tip assembly <NUM> according to embodiments of the present disclosure. <FIG> provides a more detailed view of the tip assembly <NUM>. The tip assembly <NUM> includes a tip member <NUM>, an imaging component <NUM>, and an interposer <NUM>. The tip member <NUM> has a tubular or semi-tubular body sized and shaped for insertion into a patient body. The tip member <NUM> can be composed of a thermoplastic elastomer material or any suitable biocompatible material that has acoustic impedance matching to blood within a vessel of a patient body when in use. For example, the tip member <NUM> can be composed of Pebax® polyether block amides. Dimensions of the tip member <NUM> can vary in different embodiments and may depend on the size of the catheter or the flexible elongate member <NUM>. In some embodiments, the tip member <NUM> can include a length <NUM> between about <NUM> millimeter (mm) to about <NUM> and a width <NUM> between about <NUM> to about <NUM>.

The interposer <NUM> interconnects the imaging component <NUM> to an electrical cable <NUM>. The imaging component <NUM> emits ultrasound energy and receives ultrasound echo signals reflected by surrounding tissues and vasculatures. The imaging component <NUM> is described in greater detail herein with references to <FIG>. The electrical cable <NUM> extends along a length of the flexible elongate member <NUM> and may be coupled to the cable <NUM>. The electrical cable <NUM> carries the ultrasound echo signals to the processing system <NUM> for image generation and analysis. In addition, the electrical cable <NUM> can carry control signals for controlling the imaging component <NUM>. Further, the electrical cable <NUM> can carry power for powering the imaging component <NUM>.

<FIG> is a cross-sectional view of the imaging component <NUM> taken along the line <NUM> of <FIG> according to embodiments of the present disclosure. The imaging component <NUM> is a planar component including an acoustic layer <NUM>, an IC layer <NUM>, and a backing layer <NUM>. The acoustic layer <NUM> may include multiple layers of piezoelectric materials. The IC layer <NUM> is positioned between the acoustic layer <NUM> and the backing layer <NUM>.

The acoustic layer <NUM> includes an array of ultrasound transducer elements <NUM>. The ultrasound transducer elements <NUM> are composed of piezoelectric material. Exemplary transducers for ICE have a typical thickness of approximately <NUM> in the piezoelectric material to enable an <NUM> megahertz (MHz) ultrasound signal to be generated and transmitted at a typical velocity of <NUM> meter per second (m/sec) through blood. The ultrasound signal may propagate in the direction as shown by the dashed arrows. The transducer thickness can be of various thicknesses ranging approximately from <NUM> to <NUM> to generate sufficient penetration depth in tissue imaging. In general, the thickness of the transducers can be adjusted for the frequency of sound in the transmission medium for the desired penetration depth in any tissue imaging. Image intensity can be adjusted by a driving voltage on the transducers.

In some embodiments, the acoustic layer <NUM> may include about <NUM> to about <NUM> ultrasound transducer elements <NUM> arranged in a one-dimensional (1D) pattern for two-dimensional (2D) imaging. In some embodiments, the acoustic layer <NUM> may include about <NUM> to about <NUM> ultrasound transducer elements <NUM> arranged in a 2D pattern for three-dimensional (3D) imaging.

The IC layer <NUM> includes an application-specific integrated circuit (ASIC) formed from a semiconductor material, such as silicon. The ASIC may multiplex control signals, for example, generated by the processing system <NUM>, and transfer the control signals to corresponding ultrasound transducer elements <NUM>. The controls signals can control the emission of ultrasound pulses and/or the reception of echo signals. In the reverse direction, the ASIC may receive ultrasound echo signals reflected by target tissue and received by the ultrasound transducer elements <NUM>. The ASIC may convert the ultrasound echo signals into electrical signals and transfer the electrical signals through the interposer <NUM> and the electrical cable <NUM> to the processing system <NUM> for processing and/or display. The ASIC may perform signal conditioning before transferring the signals. Signal conditioning may include filtering, amplification, and beamforming.

The backing layer <NUM> is composed of an acoustically absorptive material so that the backing layer <NUM> can absorb or deaden the ultrasonic waves coming from the back of the acoustic layer <NUM>. The backing layer <NUM> may be composed of a polymeric material. Some examples of commonly used backing materials may include Boron Nitride particles in an epoxy matrix.

Dimensions of the imaging component <NUM> may vary in different embodiments and may be dependent on the size of the tip member <NUM>. For example, the acoustic layer <NUM> can have a thickness <NUM> between about <NUM> to about <NUM>. The IC layer <NUM> can have a thickness <NUM> between about <NUM> to about <NUM>. The backing layer <NUM> can have a thickness <NUM> between about <NUM> to about <NUM>.

As described above, the IC layer <NUM> is commonly constructed from a silicon material, which has a low CTE (e.g., about <NUM> parts per million per degree Centigrade (ppm/C)). However, the polymeric material of the backing layer <NUM> is typically constructed from a polymeric material with a high CTE of about <NUM> to provide an acoustic attenuation of about <NUM> decibel per millimeter (dB/mm). Thus, the IC layer <NUM> and the backing layer <NUM> have a CTE difference of about <NUM>. The highly differentiating CTEs between the two continuous thin layers (e.g., the IC layer <NUM> and the backing layer <NUM>) can cause the imaging component <NUM> to warp or bend under thermal excursions. For example, temperature may vary from about -<NUM> degree Celsius (°C) to about <NUM> during shipping and storage of the imaging component <NUM>.

In an embodiment, to reduce CTE-based stress (e.g., warping and bending) under thermal excursions, a material with a CTE closer to the CTE of the silicon material of the IC layer <NUM> is selected for the backing layer <NUM>. Developing a material with a same CTE or a similar CTE as the silicon material of the IC layer <NUM> and having a sufficient amount of acoustic attenuation may be difficult due to the competing structural, process, and acoustic requirements of the imaging component <NUM>. One approach to providing an imaging component with a better thermal stress-balance is to select or develop a backing material with a CTE better matched to the CTE of the IC layer <NUM>, but may compromise for a lower acoustic attenuation. The following table shows some example backing materials that may be used to construct the backing layer <NUM>:.

The material A is a standard or commonly used backing material with a CTE of about <NUM> ppm/C. The material A can provide an acoustic attenuation of about <NUM> dB/mm. Some examples of the material A may include Boron Nitride particles in a soft epoxy matrix. The material B has a reduced CTE of about <NUM> ppm/C and can provide an acoustic attenuation of about 3dB/mm. Some examples of the material B may include Graphite particles in an epoxy matrix. The material C has a further reduced CTE of about <NUM> ppm/C and can provide an acoustic attenuation of about <NUM> dB/mm. Some examples of the material C may include Alumina particles in a hard epoxy matrix. The material A can provide the best acoustic attenuation for the imaging component <NUM>, but can cause bending during thermal excursions. The material B has a good compromise between CTE matching and acoustic attenuation. The material B can reduce the CTE difference between the IC layer <NUM> and the backing layer <NUM> from about <NUM> ppm/C to about <NUM> ppm/C and can provide about <NUM> percent (%) of the acoustic attenuation when compared to the material A. The material C can reduce the CTE difference to about <NUM> ppm/C and can provide about <NUM> % of the acoustic attenuation when compared to the material A. Thus, the backing material for the backing layer <NUM> can be selected based on particular transducer requirements to trade-off between acoustic attenuation and CTE-based stress.

<FIG> is a cross-sectional view of an imaging component <NUM> including a support layer <NUM> according to embodiments of the present disclosure. The imaging component <NUM> can be employed by the tip assembly <NUM> in place of the imaging component <NUM>. The cross-sectional view is taken along the line <NUM> of <FIG>. The imaging component <NUM> is substantially similar to the imaging component <NUM>, but includes the additional support layer <NUM>. As shown, the imaging component <NUM> includes an acoustic layer <NUM>, an IC layer <NUM>, a backing layer <NUM>, and a support layer <NUM>. The acoustic layer <NUM> is similar to the acoustic layer <NUM>. The acoustic layer <NUM> includes any array of ultrasound transducer elements <NUM> similar to the ultrasound transducer elements <NUM>. The IC layer <NUM> is similar to the IC layer <NUM>. The backing layer <NUM> is similar to the backing layer <NUM>, but may include a different backing material. The support layer <NUM> is attached to a bottom side of the backing layer <NUM> opposite the IC layer <NUM>. The support layer <NUM> may be a thin layer composed of a similar material or the same material as the IC layer <NUM>. As such, the support layer <NUM> can have a similar CTE or the same CTE as the IC layer <NUM>. Thus, the support layer <NUM> can balance CTE-based stress in the imaging component <NUM>. The addition of the support layer <NUM> enables the backing layer <NUM> to be constructed from the same standard or commonly used backing material. Thus, the imaging component <NUM> can provide the same acoustic attenuation performance as imaging components with standard backing materials and eliminate bending during thermal excursions.

Dimensions of the imaging component <NUM> can vary in different embodiments. In some embodiments, the acoustic layer <NUM>, the IC layer <NUM>, and the backing layer <NUM> can have similar thicknesses as the acoustic layer <NUM>, the IC layer <NUM>, and the backing layer <NUM>. The support layer <NUM> can have a thickness <NUM> between about <NUM> to about <NUM>. When the support layer <NUM> is constructed from the same material as the IC layer <NUM>, the support layer <NUM> and the IC layer <NUM> can have about the same thickness, which may provide a perfect balance with no warping regardless of temperature. When the support layer <NUM> is thinner than the IC layer <NUM>, the support layer <NUM> may be constructed from a stiffer material with a lower CTE than the IC layer <NUM> in order to perfectly balance the bending forces that may occur due to temperature changes.

<FIG> is a flow diagram of a method <NUM> of manufacturing the imaging component <NUM> according to embodiments of the present disclosure. It is understood that additional steps can be provided before, during, and after the steps of method <NUM>, and some of the steps described can be replaced or eliminated for other embodiments of the method. The steps of the method <NUM> can be carried out by a manufacturer of a catheter in the order as shown or in any suitable order (e.g., in a reverse order).

At step <NUM>, the method <NUM> includes providing an IC layer (e.g., the IC layer <NUM>). The IC layer can be constructed from a semiconductor material (e.g., silicon). At step <NUM>, the method <NUM> includes coupling an array of ultrasound transducer elements (e.g., the ultrasound transducer elements <NUM>) to the IC layer. At step <NUM>, the method <NUM> includes coupling a backing layer (e.g., the backing layer <NUM>) to the IC layer opposite the array of ultrasound transducer elements. The backing layer can be constructed from a backing material. The backing material can be selected such that the CTE of the backing material is close to the CTE of the material of the IC layer. For example, a CTE difference between the semiconductor material of the IC layer and the backing material of the backing layer may be less than <NUM> ppm/C. In some embodiments, the backing material may have a CTE between about <NUM> ppm/C to about <NUM> ppm/C. The backing material can be selected from the group of materials consisting of high density particles in a hard epoxy matrix.

<FIG> is a flow diagram of a method <NUM> of manufacturing the imaging component <NUM> according to embodiments of the present disclosure. It is understood that additional steps can be provided before, during, and after the steps of method <NUM>, and some of the steps described can be replaced or eliminated for other embodiments of the method. The steps of the method <NUM> can be carried out by a manufacturer of a catheter in the order as shown or in any suitable order.

At step <NUM>, the method <NUM> includes providing an IC layer (e.g., the IC layer <NUM>). The IC layer can be constructed from a first material (e.g., silicon). At step <NUM>, the method <NUM> includes coupling an array of ultrasound transducer elements (e.g., the ultrasound transducer elements <NUM>) to the IC layer. At step <NUM>, the method <NUM> includes coupling a backing layer (e.g., the backing layer <NUM>) to the IC layer opposite the array of ultrasound transducer elements. At step <NUM>, the method <NUM> includes coupling a support layer (e.g., the support layer <NUM>) to the backing layer opposite the IC layer. The support layer can be constructed from a second material similar to or the same as the first material. Thus, a CTE difference between the first material of the IC layer and the second material of the support layer can be less than <NUM> ppm/C. Alternatively, the second material and the first material may be the same material to provide a perfect CTE match. The support layer can balance CTE-based stress in the imaging component. Thus, the backing layer can be constructed from any of the material A, B, and/or C shown in Table <NUM>. For example, the backing layer can be constructed from commonly used backing material such as the material A described in Table <NUM> without compromising acoustic attenuation performance.

Claim 1:
An imaging catheter assembly, comprising:
a flexible elongate member (<NUM>) including a distal portion and a proximal portion; and
an imaging component (<NUM>) coupled to the distal portion (<NUM>) of the flexible elongate member, wherein the imaging component includes:
an integrated circuit (IC) layer (<NUM>) that includes a semiconductor material;
an array of ultrasound transducer elements (<NUM>) coupled to a first side of the IC layer; and
a backing layer (<NUM>) coupled to a second side of the IC layer opposite the first side, wherein the backing layer includes a backing material, characterized in that a coefficient of thermal expansion (CTE) difference between the semiconductor material and the backing material is less than <NUM> parts per million per degree Centigrade (ppm/C) and in that the backing material is selected from the group of materials consisting of high density particles in a hard epoxy matrix and includes a CTE between <NUM> parts per million per degree Centigrade (ppm/C) and <NUM> ppm/C.