Bias-corrected intravascular ultrasound catheter

Abstract

An intravascular ultrasound catheter is provided which includes multiple transducers arranged to face the same radial angle or offset radially from one another. The multiple transducers are located on a plane offset from a centerline perpendicular to the axis of the catheter. This plane may be offset from the centerline by -10 to 10 degrees.

Description

Technical Field

[0001] The present disclosure relates to medical devices and / or medical device systems. Specifically, the present disclosure relates to an intravascular ultrasound catheter and a transducer within such a catheter. This application claims the benefit of U.S. Provisional Patent Application No. 63 / 453,869, filed on Mar. 22, 2023, the disclosure of which is incorporated herein by reference.

Background Art

[0002] A wide variety of intravascular medical devices have been developed for medical applications, such as intravascular applications. Some of these devices include guidewires, catheters, etc. A subset of these devices includes an ultrasonic transducer configured to generate ultrasonic signals that can be used to reproduce an image of a blood vessel. Signals from such devices (e.g., intravascular ultrasound (IVUS) devices, etc.) are routinely used to determine the diameter of a blood vessel, the degree and / or location of calcification or other stenosis, and to select an appropriate intervention method (e.g., stent, balloon angioplasty, etc.). However, the measurements generated by an IVUS catheter assume that the catheter is parallel to the axis of the blood vessel. The angle of the IVUS catheter, i.e., the angle of the image, is susceptible to guidewire bias and can result in a distorted image. In blood vessels with a large diameter and a large bending angle, such as the iliocaval vein in the deep pelvis, the error due to bias increases, which may have a significant adverse effect on the resulting image. Therefore, there is a need for a more accurate IVUS catheter system that is less affected by the errors induced by guidewire bias.

Summary of the Invention

[0003] The present disclosure provides an IVUS catheter incorporating two or more transducers at an oblique angle that, when used with various signal processing algorithms, enables a more faithful rendering of a blood vessel than when using a conventional IVUS catheter.

[0004] The present disclosure may be implemented as an imaging head for an intravascular ultrasound (IVUS) catheter. The imaging head may comprise a transducer bed having a plurality of planes, a first ultrasonic transducer provided on a first of the plurality of planes, and a second ultrasonic transducer provided on a second of the plurality of planes.

[0005] In a further embodiment of the imaging head, the first plane and the second plane among the plurality of planes are located on the same side of the transducer bed.

[0006] In a further embodiment of the imaging head, the first plane and the second plane among the plurality of planes are radially offset from each other by an angle of 0 to 20 degrees.

[0007] In a further embodiment of the imaging head, the first plane and the second plane among the plurality of planes are provided on both sides of the transducer bed.

[0008] In a further embodiment of the imaging head, the first plane and the second plane among the plurality of planes are radially offset from each other by 170 to 190 degrees.

[0009] In a further embodiment of the imaging head, the first of the plurality of planes is offset longitudinally from the center line of the imaging head at a first angle, and the second of the plurality of planes is offset longitudinally from the center line of the imaging head at a second angle.

[0010] In a further embodiment of the imaging head, the first angle is -10 degrees or more and 10 degrees or less, and the second angle is -10 degrees or more and less than 10 degrees. In a further embodiment of the imaging head, the first angle and the second angle are the same.

[0011] In a further embodiment of the imaging head, the first angle is -10 degrees or more and 0 degrees or less, and the second angle is 0 degrees or more and 10 degrees or less. In a further embodiment, the imaging head may include a third ultrasonic transducer located on a third plane among the plurality of planes.

[0012] In a further embodiment of the imaging head, the third plane among the plurality of planes is located on the opposite side of at least the first plane among the plurality of planes in the transducer bed.

[0013] In a further embodiment, the imaging head may include a fourth ultrasonic transducer provided on the fourth plane among the plurality of planes. In a further embodiment of the imaging head, the third plane and the fourth plane of the plurality of planes are located on opposite sides of the transducer bed to the first plane and the second plane of the plurality of planes.

[0014] In a further embodiment, the imaging head may include an ultrasonic receiver located on a third plane among the plurality of planes. In a further embodiment of the imaging head, the first plane and the second plane are located on the same side of the transducer bed, and the third plane is located on the opposite side of the transducer bed from the first and second planes.

[0015] The present disclosure may be implemented as an imaging head for an intravascular ultrasound (IVUS) catheter. The imaging head may comprise a transducer bed having a plurality of planes, a first ultrasonic transducer provided on a first plane among the plurality of planes, a second ultrasonic transducer provided on a second plane among the plurality of planes, and a third ultrasonic transducer provided on a third plane among the plurality of planes.

[0016] In a further embodiment of the imaging head, the third plane among the plurality of planes is located on the opposite side of at least the first plane among the plurality of planes in the transducer bed.

[0017] In a further embodiment, the imaging head may include a fourth ultrasonic transducer provided on the fourth plane among the plurality of planes. In a further embodiment of the imaging head, the third plane and the fourth plane of the plurality of planes are located on opposite sides of the transducer bed to the first plane and the second plane of the plurality of planes.

[0018] In a further embodiment, the imaging head may include an ultrasonic receiver located on a third plane among the plurality of planes. In a further embodiment of the imaging head, the first plane and the second plane are located on the same side of the transducer bed, and the third plane is located on the opposite side of the transducer bed from the first and second planes.

[0019] The present disclosure can be implemented as an intravascular ultrasound (IVUS) catheter. The IVUS catheter may include a catheter sheath, a drive cable configured to be coupled to a motor drive unit, and an imaging core coupled to the drive cable. The imaging core may include a transducer bed having a plurality of planes, a first ultrasonic transducer provided on a first plane among the plurality of planes, and a second ultrasonic transducer provided on a second plane among the plurality of planes.

[0020] In a further embodiment of the IVUS catheter, the first plane among the plurality of planes and the second plane among the plurality of planes are provided on the same side of the transducer bed.

[0021] In a further embodiment of the IVUS catheter, the first plane among the plurality of planes and the second plane among the plurality of planes are radially offset from each other by 0 degrees to 20 degrees.

[0022] In a further embodiment of the IVUS catheter, the first plane among the plurality of planes and the second plane among the plurality of planes are provided on both sides of the transducer bed.

[0023] In a further embodiment of the IVUS catheter, the first plane among the plurality of planes and the second plane among the plurality of planes are radially offset from each other by 170 degrees to 190 degrees.

Brief Description of the Drawings

[0024] [Figure 1] FIG. 1 shows an embodiment of an intravascular imaging system. [Figure 2A] FIG. 2A shows in more detail an embodiment of a part of the intravascular imaging system of FIG. 1. [Figure 2B] FIG. 2B shows in more detail an embodiment of another part of the intravascular imaging system of FIG. 1. [Figure 3]FIG. 3 shows the distal end of a conventional IVUS catheter. [Figure 4A] FIG. 4A shows an exemplary common iliac vein. [Figure 4B] FIG. 4B shows the guide wire bias within the common iliac vein of FIG. 4A. [Figure 4C] FIG. 4C shows the actual lumen boundary of the common iliac vein of FIG. 4A together with an IVUS-based rendering of the lumen boundary in the first region. [Figure 4D] FIG. 4D shows the actual lumen boundary of the common iliac vein of FIG. 4A together with an IVUS-based rendering of the lumen boundary in the second region. [Figure 5] FIG. 5 shows the distal end of an IVUS catheter according to at least one embodiment. [Figure 6] FIG. 6 shows the distal end of an IVUS catheter according to at least one embodiment. [Figure 7] FIG. 7 shows the distal end of yet another IVUS catheter according to at least one embodiment. [Figure 8] FIG. 8 shows the distal end of yet another IVUS catheter according to at least one embodiment. [Figure 9] FIG. 9 shows the distal end of a further different IVUS catheter according to at least one embodiment. [Figure 10] FIG. 10 shows the distal end of another different IVUS catheter according to at least one embodiment. [Figure 11] FIG. 11 shows a graph depicting an error due to the catheter-to-vessel tilt of a conventional IVUS catheter compared to an IVUS catheter according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0025] As described above, numerous imaging modalities exist for evaluating vascular lesions, such as magnetic resonance imaging (MRI), computed tomography (CT), intravascular ultrasound (IVUS), optical coherence tomography (OCT), optical coherence elastography (OCE), and spectroscopy, which can provide insight into the extent to which vascular lesions deviate from healthy tissue. This disclosure relates to the acquisition of IVUS signals, and in particular to the placement of transducers in an IVUS catheter. However, prior to describing such embodiments, the overall IVUS system will be described. To facilitate identification of the description of an element or process, the most significant one or more digits of the reference code refer to the figure number in which that element was first introduced.

[0026] Figure 1 shows an exemplary IVUS imaging system 100. The IVUS imaging system 100 includes an image acquisition device 102, an IVUS catheter 104, a motor drive unit (MDU) 106, and an imaging subsystem 108. The image acquisition device 102 is coupled to the IVUS catheter 104 via the MDU 106 and also to the imaging subsystem 108. Specifically, the image acquisition device 102 is coupled to the MDU 106 via the MDU bus 110, and the MDU 106 is coupled to the IVUS catheter 104 via the catheter bus 112. In some embodiments, the MDU bus 110 and the catheter bus 112 can be transmission lines (or other conductors) arranged to transmit signals between various components. For example, the MDU bus 110 and the catheter bus 112 may be configured to transmit radio frequency signals (e.g., control signals, ultrasound pulse generation signals, ultrasound signals, etc.) between the illustrated components of the IVUS imaging system 100.

[0027] Generally, the image acquisition device 102 is configured to control the MDU 106 and receive signals from the IVUS catheter 104 via the MDU 106. The image acquisition device 102 is also configured to process the received signals to generate an image and transmit that image to the imaging subsystem 108. Therefore, the image acquisition device 102 is coupled to the imaging subsystem 108 via an imaging subsystem bus 114, which may be a wired or wireless connection. In a specific example, the imaging subsystem bus 114 may be an Ethernet® connection. In some examples, the imaging subsystem 108 may be a display, a tablet computer, or another device configured to display images rendered by the image acquisition device 102. While the imaging subsystem 108 is shown outside the image acquisition device 102, in some embodiments, the imaging subsystem 108 may be integrated into the same housing as the image acquisition device 102.

[0028] The image acquisition device 102 includes an imaging processing circuit 116, a computer subsystem 118, and other subsystems 120. As described above, this disclosure provides an improved IVUS catheter and transducer arrangement that can be implemented as part of the image acquisition device 102, and in particular as part of the IVUS catheter 104. However, before detailing the transducer arrangement covered by this disclosure, a brief description of the components of the IVUS imaging system 100 and the image acquisition device 102 is provided.

[0029] Figures 2A and 2B show a side view and a perspective view of the IVUS catheter 104 of the IVUS imaging system 100 in Figure 1. The other subsystem 120 is configured to supply power to the MDU 106 and to transmit signals to the IVUS catheter 104, particularly to one or more transducers 202 located within the IVUS catheter 104, thereby causing the IVUS catheter 104 to output an ultrasound signal.

[0030] Furthermore, mechanical energy from the MDU 106 may be used to drive the imaging core 204 located within the IVUS catheter 104. One or more transducers 202 are further configured to receive reflected signals (e.g., echo signals) in response to outputting an ultrasound signal. These reflected signals are transmitted to the image acquisition device 102 via the catheter bus 112, MDU 106, and MDU bus 110 for processing by the imaging processing circuit 116 and the computer subsystem 118.

[0031] In some embodiments, the other subsystem 120 may be configured to control, for example, the rotational speed of the imaging core 204 by the MDU 106, or the speed or length of the pullback of the imaging core 204 by the MDU 106, by controlling at least one of the frequency or duration of the electrical pulses transmitted from the image acquisition device 102 to the MDU 106.

[0032] The IVUS catheter 104 includes a long member 206 and a hub 208. The long member 206 includes a proximal end 210 and a distal end 212. The proximal end 210 of the long member 206 may be connected to the hub 208. The distal end 212 of the long member 206 is configured and positioned to allow percutaneous insertion into the patient. Optionally, the IVUS catheter 104 may define at least one flush port, such as a flush port 214. The flush port 214 may be defined within the hub 208. The hub 208 may be configured and positioned to connect to the MDU 106 of the IVUS imaging system 100.

[0033] In some examples, the elongated member 206 and the hub 208 are formed as a single unit. In other examples, the elongated member 206 and the catheter hub 208 are formed separately and then assembled.

[0034] Figure 2B is a perspective view of one embodiment of the distal end 212 of the elongated member 206 of the IVUS catheter 104. The elongated member 206 includes a sheath 216 having a longitudinal axis (e.g., a central longitudinal axis extending axially through the center of the sheath 216 and / or the IVUS catheter 104) and a lumen 222. An imaging core 224 is provided within the lumen 218. The imaging core 204 includes an imaging device 220 coupled to the distal end of a drive shaft 222, which is rotatable manually or using a computer-controlled drive mechanism (e.g., MDU 106). One or more transducers 202 may be mounted on the imaging device 220. One or more transducers 202 may be used to transmit and receive acoustic signals. The sheath 216 may be formed from any flexible biocompatible material suitable for insertion in a patient. Examples of suitable materials include polyethylene, polyurethane, plastics, spiral-cut stainless steel, Nitinol Hypo tubing, or combinations thereof.

[0035] In some embodiments, an array of transducers 202 is mounted on the imaging device 220, for example, as shown in the figure. Alternatively, a single transducer may be used. Any suitable number of transducers 202 may be used. For example, there may be 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 16, 20, 25, 50, 100, 500, 1000 or more transducers. As can be understood, other numbers of transducers may also be used. When multiple transducers 202 are used, the transducers 202 may be configured in any suitable array, including, for example, a ring array, a rectangular array, etc.

[0036] One or more transducers 202 may be formed from a material capable of converting applied electrical pulses into pressure strains on the surface of one or more transducers 230, and vice versa. Examples of suitable materials include piezoelectric ceramic materials, piezoelectric composite materials, piezoelectric plastics, barium titanate, lead zirconate titanate, lead metaniobate, and polyvinylidene fluoride. Other transducer technologies include composite materials, single-crystal composite materials, and semiconductor devices (e.g., capacitive microfabrication ultrasonic transducers ("cMUT"), piezoelectric microfabrication ultrasonic transducers ("pMUT"), etc.).

[0037] Pressure strain on the surface of one or more transducers 202 forms acoustic pulses of a frequency based on the resonant frequencies of the one or more transducers 202. The resonant frequencies of the one or more transducers 202 may be influenced by the size, shape, and material used to form the one or more transducers 202. The one or more transducers 202 may be formed into any shape suitable for placement within the IVUS catheter 104 and for propagating acoustic pulses of a desired frequency in one or more selected directions. For example, the transducers may be disk-shaped, block-shaped, rectangular, elliptical, etc. The one or more transducers may be formed into a desired shape by any process including, for example, dicing, die-and-fill, machining, micro-machining, etc.

[0038] As an example, each of one or more transducers 202 may include a layer of piezoelectric material sandwiched between a matching layer and a conductive backing material formed from an acoustic absorbing material (e.g., an epoxy substrate having tungsten particles). During operation, the piezoelectric layer can be electrically excited to cause the emission of acoustic pulses.

[0039] One or more transducers 202 may be used to form a radial cross-sectional image of the surrounding space. For example, when one or more transducers 202 are placed in an IVUS catheter 104 and inserted into a patient's blood vessel, one or more transducers 202 may be used to capture acoustic signals processed by the imaging device 102, in particular the analog front end (AFE) described herein.

[0040] The imaging core 204 is rotated around the longitudinal axis of the IVUS catheter 104. As the imaging core 204 rotates, one or more transducers 202 emit acoustic signals in different radial directions (e.g., along different radial scan lines). For example, one or more transducers 202 may emit acoustic signals in regular (or irregular) increments, such as 256 radial scan lines per rotation. Alternatively, it may be understood that other numbers of radial scan lines can be emitted per rotation.

[0041] When an emitted acoustic pulse with sufficient energy reaches one or more medium boundaries, such as one or more tissue boundaries, a portion of the emitted acoustic pulse is reflected back to the transducer that emitted it as an echo pulse. Each echo pulse that reaches the transducer with sufficient energy for detection is converted into an electrical signal in the receiving transducer. One or more converted electrical signals are transmitted to the imaging processing circuit 116 of the image acquisition device 102 for processing and digitization. The digitized signals are communicated to the computer subsystem 118 and can be used to form an image of blood vessels, which can then be displayed on the imaging subsystem 108. In some examples, the rotation of the imaging core 204 is driven by the MDU 106, and this rotation is controlled by another subsystem 120.

[0042] When one or more transducers 202 are rotated about (or parallel to) the longitudinal axis of the distal end of the IVUS catheter 104 that emits acoustic pulses, multiple images may be formed that collectively form radial cross-sectional images (e.g., tomographic images) of a portion of the region surrounding the one or more transducers 202, such as the wall of the vessel of interest and the surrounding tissue. The imaging core 204 may also move longitudinally along the vessel into which the IVUS catheter 104 is inserted, so that multiple cross-sectional images can be formed along the longitudinal length of the vessel. During the imaging process, one or more transducers 202 may be retracted (e.g., pulled back) along the longitudinal length of the IVUS catheter 104. The IVUS catheter 104 may include at least one expandable section that can be retracted during the pullback of one or more transducers 202. In some examples, an MDU 106 drives the pullback of the imaging core 204 within the IVUS catheter 104. The pullback distance of the MDU 106 of the imaging core 204 can be any suitable distance, for example, including at least 5 cm, 10 cm, 15 cm, 20 cm, 25 cm, or more. The entire IVUS catheter 104 can be retracted during imaging, regardless of whether the imaging core 204 moves longitudinally independently of the IVUS catheter 104.

[0043] The quality of images generated at different depths by one or more transducers 202 may be influenced by one or more factors, including, for example, bandwidth, transducer focus, beam pattern, and acoustic pulse frequency. The frequency of the acoustic pulses output from one or more transducers 202 may also affect the penetration depth of the acoustic pulses output from one or more transducers 202. Generally, as the frequency of the acoustic pulse decreases, the penetration depth of the acoustic pulse in patient tissue increases. In some examples, the endovascular IVUS imaging system 100 operates within a frequency range of 5 MHz to 200 MHz.

[0044] One or more conductors 224 can electrically couple the transducer 202 and the catheter bus 112. In this way, the electrical signal captured by the transducer 202 can be received by the image processing circuit 116 of the image acquisition device 102.

[0045] The IVUS imaging system 100 described above utilizes the mechanical rotation of the transducer 202 (for example, via the MDU 106). However, other IVUS imaging systems may include an array of transducers in which multiple transducers are positioned perpendicular to the catheter axis so that transducer rotation is not required. In such cases, the IVUS imaging system does not require an MDU. As described above, this disclosure provides several exemplary transducer arrangements that mitigate the effects of guidewire bias. While examples are described with reference to the IVUS imaging system 100 and the rotating transducer mechanism, the exemplary arrangements described herein are also applicable to fixed array IVUS catheters and corresponding imaging systems.

[0046] Figure 3 shows an example of the distal end of a conventional IVUS catheter 300. The IVUS catheter 300 includes an imaging core 302, an imaging head 304, and a transducer 306 positioned within the imaging head 304 at an angle 308. As can be seen from the figure, the angle 308 is offset from the vertical or radial angle of the imaging head 304. Conventionally, this angle is 5 degrees. As described above, conventional IVUS catheters (e.g., IVUS catheter 300) are susceptible to guidewire bias.

[0047] Figure 4A shows an exemplary iliac vena cava 400 with a right iliac vein 402 and a left iliac vein 404. The iliac vena cava 400 is located within the pelvic region and can be affected by several diseases for which intracellular imaging (e.g., IVUS imaging) may be useful for diagnosis and / or treatment. However, depending on the size and shape of the iliac vena cava 400, the image may be distorted due to what is called guidewire bias.

[0048] Figure 4B shows the left iliac vein 404 with a guidewire installed within it. The true centerline 406 of the left iliac vein 404 is highlighted along with the guidewire route 408. As can be seen from the figure, due to the anatomical structure of the left iliac vein 404, the true centerline 406 and the guidewire route 408 branch at various points along the left iliac vein 404. This branching leads to guidewire bias. For example, when the guidewire route 408 branches off from the true centerline 406, the distance from the transducer of the IVUS catheter connected to the guidewire to the wall of the left iliac vein 404 will differ on one side and the other. Furthermore, the angle of incidence of the ultrasound signal to the wall of the left iliac vein 404 will differ on one side and the other at the point where the guidewire route 408 branches off from the true centerline 406. The larger this branching, the greater the difference in distance and angle of incidence between the transducer and the bilateral walls of the left iliac vein 404. This difference in distance and angle of incidence causes distortion in the resulting ultrasound image.

[0049] For example, regions 410 and 412 are highlighted on the left iliac vein 404. Figure 4C shows images of the actual lumen boundary 414 and the IVUS lumen boundary 416 from region 410. As can be seen from the figure, the guidewire path 408 branches significantly from the true centerline 406 in region 410. As a result, the ultrasound image from region 410 is distorted. This is evident at the lumen boundary. The IVUS lumen boundary 416 is significantly larger than the actual lumen boundary 414 within region 410.

[0050] On the other hand, Figure 4D shows images of the actual lumen boundary 414 and the IVUS lumen boundary 416 from region 412. As can be seen from the figure, compared to region 410, the guidewire path 408 does not branch off as much from the true centerline 406 in region 412. As a result, there is less significant distortion in the ultrasound image from region 412. This is evident at the lumen boundary. The IVUS lumen boundary 416 is closer to and coincides with the actual lumen boundary 414 in region 412.

[0051] Figure 5 shows an example of the distal end of an IVUS catheter 500 provided according to at least one embodiment of the present disclosure. The IVUS catheter 500 includes an imaging core 502, an imaging head 504, and transducers 506a, 506b positioned within the imaging head 504 at angles 508a, 508b offset from the centerline 510.

[0052] As can be seen in the figure, the IVUS catheter 500 includes multiple transducers (e.g., transducers 506a, 506b) that are radially offset from each other. For example, as can be seen in the figure, transducers 506a and 506b are radially offset from each other by approximately 180 degrees. Furthermore, transducers 506a and 506b are positioned at an angle offset from the centerline 510. As used herein, the term “centerline” means a line perpendicular to the longitudinal axis of the IVUS catheter 500. Therefore, when the IVUS catheter 500 is not parallel to the central axis of a blood vessel (e.g., left iliac vein 404), one transducer (e.g., transducer 506a) will be deflected more perpendicularly to the blood vessel wall than the other (e.g., transducer 506b). Transducers that are more perpendicular to the blood vessel wall produce a higher contrast image and show the venous wall closer to the catheter. In contrast, transducers that are more inclined relative to the vessel wall produce lower-contrast images of the vein wall away from the catheter.

[0053] The imaging head 504 includes a molded transducer bed having several planes 512 formed at an angle to the centerline 510, which provides a platform and support for transducers 506a, 506b. In some examples, angles 508a, 508b are between -10 and 10 degrees. Angles 508a and 508b do not have to be the same. For example, angle 508a could be 5 degrees and angle 508b could be 10 degrees. Beyond the scope of this disclosure, image processing software can render a composite vascular image using algorithms that utilize both signals (e.g., from transducers 506a, 506b).

[0054] The plane 512 may be on the same side of the imaging head 504 (see, for example, Figure 6), or it may be on both sides of the imaging head 504 (as shown, for example, in Figure 5). Furthermore, in some embodiments, multiple planes 512 may be radially offset from one another. For example, one of the multiple planes 512 may be radially offset from the other planes 512 by 170 to 190 degrees.

[0055] Figure 6 shows an example of the distal end of an IVUS catheter 600 provided according to at least one embodiment of the present disclosure. The IVUS catheter 600 includes an imaging core 602, an imaging head 604, and transducers 606a and 606b positioned on the imaging head 604 at angles 608a and 608b, respectively, offset from the centerlines 610a and 610b. As can be seen from the figure, the IVUS catheter 600 includes a plurality of transducers offset from the field of view plane of the imaging head 604, where the field of view plane is a plane perpendicular to the longitudinal axis of the imaging head 604. In this case, one transducer is offset at a positive angle from the field of view plane, and the other transducer is offset at a negative angle from the field of view plane. In this example, transducers 606a and 606b are angled toward each other. In some examples, angles 608a and 608b are between -10 and 10 degrees. Angles 608a and 608b do not need to be the same.

[0056] As described above, in some examples, the plane 612 on which transducers 606a and 606b are provided is not offset radially. In other examples, the planes 612 are slightly offset radially from each other, for example, between 0 and 20 degrees.

[0057] Figure 7 shows an example of the distal end of an IVUS catheter 700 provided according to at least one embodiment of the present disclosure. The IVUS catheter 700 includes an imaging core 702, an imaging head 704, and transducers 706a and 706b mounted on the imaging head 704 at angles 708a and 708b offset from the centerlines 710a and 710b, respectively. As can be seen from the figure, the IVUS catheter 700 includes a plurality of transducers offset from each other with respect to the field of view plane. In this example, transducers 706a and 706b are angled away from each other. In some examples, angles 708a and 708b are between -10 degrees and 10 degrees. Angles 708a and 708b do not need to be the same.

[0058] Figure 8 shows an example of the distal end of an IVUS catheter 800 provided according to at least one embodiment of the present disclosure. The IVUS catheter 800 includes an imaging core 802, an imaging head 804, and transducers 806a, 806b, and 806c located within the imaging head 804. As can be seen from the figure, the IVUS catheter 800 includes a plurality of transducers radially offset from each other. The IVUS catheter 800 includes transducers 806a and 806b that are oriented at substantially the same radial angle and offset from the centerlines 810a and 810b, respectively. The IVUS catheter 800 also includes transducer 806c that is radially offset from transducers 806a and 806b (for example, by about 180 degrees) and positioned at an angle 808c offset from the centerline 810b. Transducers 806a and 806b are shown facing away from each other, but they may also be positioned facing each other (for example, as transducers 606a and 606b in Figure 6). In some examples, angles 808a, 808b, and 808c are between -10 degrees and 10 degrees. Angles 808a, 808b, and 808c do not need to be the same.

[0059] Figure 9 shows an example of the distal end of an IVUS catheter 900 provided according to at least one embodiment of the present disclosure. The IVUS catheter 900 includes an imaging core 902, an imaging head 904, and transducers 906a, 906b, 906c, and 906d located within the imaging head 904. As can be seen from the figure, the IVUS catheter 900 includes a plurality of transducers radially offset from each other. The IVUS catheter 900 includes transducers 906a and 906b arranged at substantially the same radial angle and offset from the centerlines 910a and 910b, respectively. The IVUS catheter 900 also includes transducers 906c and 906d, which are radially offset from transducers 906a and 906b (for example, by about 180 degrees, etc.) and arranged at angles 908c and 908d offset from the centerlines 910a and 910b, respectively. These transducers are shown facing away from each other, but they may also be arranged facing each other (for example, transducers 606a and 606b in Figure 6). In some embodiments, angles 908a, 908b, 908c, and 908d are between -10 degrees and 10 degrees. Angles 908a, 908b, 908c, and 908d do not need to be the same.

[0060] Figure 10 shows an example of the distal end of an IVUS catheter 1000 provided according to at least one embodiment of the present disclosure. The IVUS catheter 1000 includes an imaging core 1002, an imaging head 1004, and a transducer 1006 positioned within the imaging head 1004 at an angle 1008 offset from the centerline 1010. Furthermore, the IVUS catheter 1000 includes an ultrasound receiver 1012 positioned in the imaging head on the opposite side of the transducer 1006 and at an angle 1014 offset from the centerline 1010. In some examples, angles 1008 and 1014 are between -10 degrees and 10 degrees. Angles 1008 and 1014 do not need to be the same.

[0061] Other embodiments described herein may have one or more transducers and two or more receivers. As another example, the apparatus of the present disclosure may have two or more transducers and one or more receivers. For example, the transducers 806a and / or transducers 806c of the IVUS catheter 800 in Figure 8 may be ultrasound receivers.

[0062] As described above, conventional IVUS catheters with a single transducer set in the imaging head are affected by guidewire bias. More specifically, the inclination between the catheter and the vessel, or the deviation of the vessel centerline (e.g., true centerline 406) from the catheter centerline (e.g., guidewire path 408), can range from 0 to 45 degrees. The inclination between the catheter and the vessel can have an average angle of 10 to 15 degrees, and this inclination can be significantly higher in areas with large changes in curvature or at confluence points. As a result, the degree of guidewire bias increases as described above.

[0063] High bias in areas where size measurement is critical can lead to inaccurate measurement results (e.g., balloon or stent selection). However, this disclosure provides a significant reduction in tilt error. For example, Figure 11 shows a graph 1100 for two different IVUS catheters, with the catheter-to-vascular tilt (degrees) on the x-axis 1102 and the error as a percentage on the y-axis 1104. Plot 1106 shows the error for catheter-to-vascular tilt of a conventional IVUS catheter (e.g., IVUS catheter 300) having a single transducer offset by 5 degrees from the centerline. On the other hand, plot 1108 shows the error for catheter-to-vascular tilt of an IVUS catheter according to this disclosure, specifically an IVUS catheter (e.g., IVUS catheter 500) having two transducers offset by 10 degrees from the centerline.

[0064] As can be seen from the figure, the error of the IVUS catheter according to this disclosure decreases significantly as the inclination between the catheter and the blood vessel increases. Terms used herein are given their common meanings in the relevant technical field, or the meanings indicated by their use in the context; however, where a clear definition is provided, that meaning shall prevail.

[0065] In this specification, references to “one embodiment” or “a certain embodiment” do not necessarily refer to the same embodiment, nor do they necessarily refer to the same embodiment. Unless the context clearly indicates otherwise, throughout this specification and the claims, words such as “equipped with,” “equipped with,” etc., are interpreted comprehensively, as opposed to exclusive or exhaustive, meaning “including but not limited to.” Terms used singular or plural include both singular and plural, respectively, unless expressly limited to one or more. Also, when used in this application, words such as “in this specification,” “above,” “below,” and similar words refer to the entire application, not to any part thereof. When the claims use the word “or” in relation to a list of two or more items, the word includes any item in the list, all items in the list, and any combination of items in the list, unless expressly limited to one or the other. Any term not expressly defined in this specification has its conventional meaning as generally understood by those skilled in the art.

Claims

1. An imaging head for an intravascular ultrasound (IVUS) catheter, A transducer bed containing multiple planes, A first ultrasonic transducer provided on the first plane among the plurality of planes, A second ultrasonic transducer provided on a second plane among the plurality of planes, An imaging head equipped with the following features.

2. The imaging head according to claim 1, wherein the first plane and the second plane among the plurality of planes are provided on the same side of the transducer bed.

3. The imaging head according to claim 1 or 2, wherein the first plane and the second plane among the plurality of planes are offset from each other by 0 to 20 degrees with respect to a field of view plane perpendicular to the longitudinal axis of the transducer bed.

4. The imaging head according to claim 1, wherein the first plane and the second plane among the plurality of planes are provided on both sides of the transducer bed.

5. The imaging head according to claim 1 or 4, wherein the first plane and the second plane among the plurality of planes are radially offset from each other by 170 to 190 degrees.

6. The imaging head according to claim 1, wherein the first plane among the plurality of planes is offset longitudinally at a first angle from the center line of the imaging head, and the second plane among the plurality of planes is offset longitudinally at a second angle from the center line of the imaging head.

7. The imaging head according to claim 6, wherein the first angle is -10 degrees or more and 10 degrees or less, and the second angle is -10 degrees or more and less than 10 degrees.

8. The imaging head according to claim 7, wherein the first angle is -10 degrees or more and 0 degrees or less, and the second angle is 0 degrees or more and 10 degrees or less.

9. The imaging head according to claim 8, wherein the first angle and the second angle are the same.

10. The imaging head according to any one of claims 1 to 9, comprising a third ultrasonic transducer provided on a third plane among the plurality of planes.

11. The imaging head according to claim 10, wherein the third plane among the plurality of planes is located on the opposite side of at least the first plane among the plurality of planes in the transducer bed.

12. The imaging head according to claim 10, further comprising a fourth ultrasonic transducer provided on the fourth of the plurality of planes.

13. The imaging head according to claim 12, wherein the third plane and the fourth plane among the plurality of planes are located on opposite sides of the transducer bed to the first plane and the second plane among the plurality of planes.

14. The imaging head according to claim 1, further comprising an ultrasonic receiver provided on a third plane among the plurality of planes.

15. The imaging head according to claim 14, wherein the first plane and the second plane are provided on the same side of the transducer bed, and the third plane is provided on the side of the transducer bed opposite to the first and second planes.

Images