Patent Application
20140257102
The present disclosure relates generally to the field of invasive imaging systems, and in particular, to devices, systems, and methods comprising a catheter for dual image intravascular ultrasound (IVUS).
IVUS imaging is widely used in interventional cardiology as a diagnostic tool for assessing a diseased vessel, such as an artery, within the human body to determine the need for treatment, to guide the intervention, and/or to assess its effectiveness. IVUS imaging uses ultrasound echoes to form an image of the vessel of interest. Typically, the ultrasound transducer on an IVUS catheter both emits ultrasound pulses and receives the reflected ultrasound echoes. The ultrasound waves pass easily through most tissues and blood, but they are partially reflected by discontinuities arising from tissue structures (such as the various layers of the vessel wall), red blood cells, and other features of interest. The IVUS imaging system, which is connected to the IVUS catheter by way of a patient interface module, processes the received ultrasound echoes to produce an image of the vessel where the catheter is located.
There are primarily two types of IVUS catheters in common use today: solid-state and rotational. Solid-state IVUS catheters use an array of ultrasound transducers (typically 64) distributed around the circumference of the catheter and connected to an electronic multiplexer circuit. The multiplexer circuit selects array elements for transmitting an ultrasound pulse and receiving the echo signal. By stepping through a sequence of transmit-receive pairs, the solid-state IVUS system can synthesize the effect of a mechanically scanned transducer element, but without moving parts. Since there is no rotating mechanical element, the transducer array can be placed in direct contact with the blood and vessel tissue with minimal risk of vessel trauma and the solid-state scanner can be wired directly to the imaging system with a simple electrical cable and a standard detachable electrical connector.
In the typical rotational IVUS catheter, a single ultrasound transducer element fabricated from a piezoelectric ceramic material is located at the tip of a flexible driveshaft that spins inside a sheath inserted into the vessel of interest. The typical transducer element is oriented such that the ultrasound beam propagates generally perpendicular to the axis of the catheter. In the typical IVUS catheter, the fluid-filled (e.g., saline-filled) sheath protects the vessel tissue from the spinning transducer and driveshaft while permitting ultrasound signals to freely propagate from the transducer into the tissue and back. As the driveshaft rotates (typically at 30 revolutions per second), the transducer is periodically excited with a high voltage pulse to emit a short burst of ultrasound. The ultrasound is emitted from the transducer, through the saline-fill and sheath wall, in a direction generally perpendicular to the axis of rotation of the driveshaft. The same transducer then listens for the returning echoes reflected from various tissue structures, and the IVUS imaging system assembles a two dimensional image of the vessel cross-section from a sequence of several hundred of these ultrasound pulse/echo acquisition sequences occurring during a single revolution of the transducer.
Current methods for treating vascular occlusions involve crossing the occlusion with a guide wire prior to opening the occluded vasculature. A true lumen (i.e., natural vascular lumen) crossing technique involves passing the guidewire through the occlusion. Using current IVUS systems for guide wire placement, clinicians are often unable to navigate the IVUS catheter through the occlusion and remain within the true lumen. Sub-intimal crossing is another technique for guide wire placement that involves advancing the guidewire through a sub-intimal passage, tangentially past the occlusion. The guide wire re-enters the true lumen after passing the occlusion. Both of these techniques carry the risk of vasculature perforation because the clinician is unable to visualize the true lumen on the opposite side of the occlusion and, as a consequence, may direct the IVUS catheter toward or through the vascular wall.
While existing IVUS catheters deliver useful therapeutic information, there is a need for improved imaging capability to assist navigation, vasculature evaluation, and delivery of treatment.
The embodiments of the invention are summarized by the claims that follow below.
In one embodiment, system for imaging a vessel of a patient comprises an elongated sheath with proximal and distal ends. The elongated sheath includes a flexible body with a first lumen in communication with a distal opening at the distal end. The system further includes an imaging core disposed within the first lumen and rotatable about an axis of rotation. The imaging core includes a first transducer subassembly adapted to transmit a first beam, distally of the flexible body, through the distal opening. The imaging core also includes a second transducer subassembly adapted to transmit a second beam through the flexible body in a transverse direction to the axis of rotation.
In another embodiment, a method of imaging a vessel of a patient comprises providing an elongated sheath having a proximal end and a distal end. The sheath includes a flexible body with a first lumen in communication with a distal opening at the distal end. The method further includes rotating a first transducer subassembly about an axis of rotation within the first lumen while directing a first beam from the distal opening and rotating a second transducer subassembly about the axis of rotation within the first lumen while directing a second beam approximately transversely to the axis of rotation. The method further includes receiving reflected first and second beams.
Additional aspects, features, and advantages of the present disclosure will become apparent from the following detailed description.
Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It is nevertheless understood that no limitation to the scope of the disclosure is intended. Any alterations and further modifications to the described devices, systems, and methods, and any further application of the principles of the present disclosure are fully contemplated and included within the present disclosure as would normally occur to one skilled in the art to which the disclosure relates. In particular, it is fully contemplated that the features, components, and/or steps described with respect to one embodiment may be combined with the features, components, and/or steps described with respect to other embodiments of the present disclosure. For the sake of brevity, however, the numerous iterations of these combinations will not be described separately.
Referring first to
The IVUS catheter 102 includes an elongated, flexible catheter sheath 110 shaped and configured for insertion into a lumen of a blood vessel (not shown) such that a longitudinal axis LA of the catheter 102 substantially aligns with a longitudinal axis of the vessel at any given position within the vessel lumen. In that regard, the curved configuration illustrated in
In some embodiments, a rotating imaging core 112 extends within the sheath 110. Accordingly, in some embodiments imaging core 112 is rotated relative to the sheath 110. The sheath 110 has both a proximal end portion 114 and a distal end portion 116. The imaging core 112 has a proximal end portion 118 disposed within the proximal end portion 114 of the sheath 110 and a distal end portion 120 disposed within the distal end portion 116 of the sheath 110.
The distal end portion 116 of the sheath 110 and the distal end portion 120 of the imaging core 112 are inserted into a patient during the operation of the system 100. The usable length of the catheter 102 (e.g., the portion that can be inserted into a patient) can be any suitable length and can be varied depending upon the application.
The proximal end portion 114 of the sheath 110 and the proximal end portion 118 of the imaging core 112 are connected to the interface module 104. The proximal end portions 114, 118 are fitted with a catheter hub 124 that is removably connected to the interface module 104.
The distal end portion 120 of the imaging core 112 includes a transducer subassembly 122 and a transducer subassembly 123. The transducer subassemblies 122, 123 can be of any suitable type for visualizing a vessel and, in particular, a severe occlusion in a vessel. In this embodiment, the transducer subassembly 122 is configured for forward scanning to capture images of the vessel area distal of the transducer subassembly 122. In this embodiment, the transducer subassembly 123 is configured for side scanning to capture images of a cross-sectional area of the vessel. The transducer subassemblies 122, 123 are configured to be rotated (either by use of a motor or other rotary device) to obtain the images of the vessel. Accordingly, the transducer subassemblies may be an ultrasound transducer array (e.g., arrays having 16, 32, 64, or 128 elements are utilized in some embodiments) or single ultrasound transducers. In alternative embodiments, one or more optical coherence tomography (“OCT”) elements (e.g., mirror, reflector, and/or optical fiber) may be included in or comprise the transducer subassembly. Suitable transducer subassemblies may include, but are not limited to, one or more advanced transducer technologies such as Piezoelectric Micromachined Ultrasonic Transducer (“PMUT”) and Capacitive Micromachined Ultrasonic Transducer (“CMUT”).
The rotation of imaging core 112 within sheath 110 is controlled by PIM 104. For example, PIM 104 provides user interface controls that can be manipulated by a user. In some embodiments PIM 104 may receive and analyze information received through imaging core 112. It will be appreciated that any suitable functionality, controls, information processing and analysis, and display can be incorporated into PIM 104. Thus, PIM 104 may include a processor circuit 154 and a memory circuit 155 to execute operations on catheter 102 and receive, process, and store data from catheter 102. In some embodiments, PIM 104 receives data from ultrasound signals (echoes) detected by imaging core 112 and forwards the received echo data to control system 106. Control system 106 may include a processor circuit 156 and a memory circuit 157 to execute operations on catheter 102 and receive, process, and store data from catheter 102. In some embodiments, PIM 104 performs preliminary processing of the echo data prior to transmitting the echo data to control system 106. PIM 104 may perform amplification, filtering, and/or aggregating of the echo data, using processor circuit 154 and memory circuit 155. PIM 104 can also supply high- and low-voltage DC power to support operation of catheter 102 including the circuitry within transducer assembly 122.
In some embodiments, wires associated with IVUS imaging system 100 extend from control system 106 to PIM 104. Thus, signals from control system 106 can be communicated to PIM 104 and/or vice versa. In some embodiments, control system 106 communicates wirelessly with PIM 104. Further according to some embodiments, catheter 102 may communicate wirelessly with PIM 104. Similarly, it is understood that, in some embodiments, wires associated with the IVUS imaging system 100 extend from control system 106 to monitor 108 such that signals from control system 106 can be communicated to monitor 108 and/or vice versa. In some embodiments, control system 106 communicates wirelessly with monitor 108.
Electrical cables 208 with optional shielding 210 extends through an inner lumen of the flexible drive shaft 204. Leads from one of the cables 208 are soldered, welded, or otherwise electrically coupled to a transducer subassembly 215. At least a portion of the cables 208 further extends past the subassembly 215, and the leads of another one of the cables 208 are soldered, welded, or otherwise electrically coupled to a transducer subassembly 216. The proximal end of the cables 208 terminate in a series of rings for electrical interface with an interface module through a hub (similar to hub 124).
The transducer subassemblies 215, 216 are secured to the housing 206 by a backing material such an epoxy or a similar bonding agent. The backing material may also serve to absorb acoustic reverberations within the housing 206 and as a strain relief for the electrical cable 208 where it is attached to the transducer subassemblies.
The transducer subassembly 216 includes a generally circular or elliptical planar face 220 mounted at an oblique mounting angle MA with respect to a rotational axis RA of the imaging core 202. In one embodiment, the mounting angle MA may be 45°, but larger or smaller mounting angles may also be suitable. For example, mounting angles of 55°, 35°, or 15° with respect to the rotational axis may be suitable depending upon the desired field of view.
The transducer housing 206 includes an opening 228 bounded by a wall section 230, a wall section 232, and a wall section 233. The wall section 230 is angled with respect to the rotational axis RA and may, for example, be angled at the mounting angle MA. The wall section 232 may be generally transverse to the rotational axis RA. The wall section 233 may be generally parallel to the rotational axis RA and/or parallel to the planar face of the transducer assembly 215. The transducer housing 206 has an outer diameter D1.
In use, as configured, the transducer subassembly 216 produces a forward-imaging ultrasound beam 234 propagating generally perpendicular to the face 220 of the transducer subassembly 216. The beam 234 passes through the opening 228 of the transducer housing 206 and propagates distally from the catheter system 200 into a vascular region distal (i.e., forward) of the catheter. After reflecting off tissue, including blockages or occlusions, located distally of the transducer subassembly 216, an echo beam is detected by the transducer subassembly and sent to a control system for processing and display.
The side-scanning transducer subassembly 215 may include, for example, a PMUT MEMS transducer layer arranged approximately parallel to the rotational axis RA, with a spherically focused portion facing the opening 228. In some embodiments, transducer subassembly 215 may include an application-specific integrated circuit (ASIC) (not shown) within the imaging core 202. The ASIC may be electrically coupled to the transducer layer. In some embodiments of the present disclosure the ASIC may include an amplifier, a transmitter, and a protection circuit associated with the transducer layer. In some embodiments, the ASIC is flip-chip mounted to a substrate of the PMUT MEMS transducer layer using anisotropic conductive adhesive or suitable alternative chip-to-chip bonding method.
In use, as configured, the transducer subassembly 215 produces a side-imaging ultrasound beam 238 propagating generally perpendicular to the face of the transducer subassembly 215. The beam 238 passes through the opening 228 and propagates radially away from the catheter system 200 into a lateral vascular region. After reflecting off tissue, including blockages or occlusions, located laterally of the transducer subassembly 215, an echo beam is detected by the transducer subassembly and sent to a control system for processing and display.
Referring now to
The sheath 300 includes a distal wall 301 having a distal opening 302 in communication with a lumen 304 that extends the length of the sheath 300. The lumen 304 is centered about a longitudinal axis A1 and has a diameter D2 which is sufficiently larger than the outer diameter D1 of the transducer housing 206 to permit rotation of the transducer housing and transducer subassemblies 215, 216 within the lumen 304. In one embodiment, for example, the diameter D2 of the lumen 302 may be approximately 0.035-0.020 inches. The distal wall 301 extends generally perpendicular to the longitudinal axis A1.
The imaging core 202, including transducer housing 206 and transducer subassemblies 215, 216 are inserted into and rotate within the lumen 304. (
The sheath 300 also includes an opening 306 in the distal wall 301. The opening 306 is in communication with a lumen 308 that may extend the length of or a partial length of the sheath 300. The lumen 308 may be sized to receive a guide wire 350 (See
Optionally, at step 378, an image of the tissue located distally of the sheath is generated on a display based on information from the forward-scanning transducer subassembly 216. Because the guide wire 350 may be visible in the generated image, a user may rotate the sheath 300 relative to the interface module. In doing so, the location of the wire 350 in the generated image may be rotated either away from an area of interest to reduce obstruction of view or into an area of interest to serve as a referencing landmark. Optionally, at step 380, an image of a radial cross-section of the vessel is generated on a display based upon information from the side-scanning transducer assembly 215.
Optionally, at step 382, the images from the forward-scanning and side-scanning transducers are displayed on a common display. The synchronization of the two images may provide the clinician with information regarding the position and orientation of the distal end of catheter 200 within the patient vessel.
For example,
If, as shown in
Some methods for treating vascular occlusions involve crossing the occlusion with a guide wire prior to opening the occluded vasculature. These methods are true lumen (i.e., natural vascular lumen) crossing techniques and involve passing the guidewire through the occlusion. When crossing the occlusion through the true lumen, the clinician attempts to keep the catheter centered within the vessel lumen. The forward-scanning transducer assembly allows the clinician to visualize the vessel, plaque morphology, and other vessel lumens near the true lumen. The use of dual transducer assemblies provides the clinician with additional information to help the clinician keep the catheter within the true lumen. The dual image display with synchronized or desynchronized images indicates the position and orientation of the distal tip of the catheter with respect to the vessel lumen. When the images become desynchronized, indicating that the distal catheter tip has become angled within the patient vessel, the clinician may initiate deflection changes to the catheter to steer the catheter back to a centered pose. As the catheter is recentered, dual images become re-synchronized.
Sub-intimal crossing is another technique for guide wire placement that involves advancing the guidewire through a sub-intimal passage, tangentially past the occlusion. The guide wire re-enters the true lumen after passing the occlusion. With a single transducer subassembly, re-entry into the true lumen may be challenging with the catheter advancing well beyond the occlusion before re-entry. Using a dual scanning catheter system may facilitate true lumen re-entry by locating and selecting a sub-intimal passage that returns the catheter to the true lumen near the distal side of the occlusion. The dual scanning catheter thus reduces the likelihood of uncontrolled advancement of the catheter, allowing the catheter to re-enter the true lumen immediately after the occlusion has been crossed.
The use of a dual scanning catheter may also provide information to the clinician about the patient's blood flow. With the ability to scan the blood flow at 45° with the forward-scanning transducer subassembly and at 90° with the side-scanning transducer subassembly, the velocity of the blood flow may be calculated. The 45° image provides a Doppler effect for the blood flow. By adding the images together, subtracting the images from one another, or other methods of comparison, the blood flow can be computed. The computed information about the blood flow velocity allows images of relative blood flow to be mapped and imaged. The blood flow velocity information may also allow blood speckle to be removed from the displayed images.
The use of dual scanning also may allow the clinician to determine where the guide wire is located. For example, as the clinician advances the guide wire, with the catheter held relatively stationary, the guide wire is visualized twice, first in the side-scanning image and second in the forward-scanning image. From the images, the clinician may determine the location of the guide wire.
OTW catheters have a lumen that extends inside the entire length of the catheter into which a guide wire can be inserted. With RX catheters, the guide wire only enters into the catheter body near its distal end, instead of entering at the proximal-most end, and extends inside the catheter body to the distal most end of the catheter where it exits.
There are advantages and disadvantages to both designs. The OTW catheters allow easy exchange of guide wires should additional catheter support, from a stiffer guide wire, or a change in the shape or stiffness of the guide wire tip be necessary. The RX catheters allow the operator to more rapidly change from one catheter to another while leaving the guide wire in place, thereby preserving the placement of the guide wire distal tip, which may have been difficult to achieve. Although “standard” length (typically approximately 190 cm) guide wires usually have a proximal extension capability built in (extending the overall length to approximately 300 cm), the use of these accessories is cumbersome and can require two sterile operators.
Typically, about 190 cm guide wires are required to span a vessel from the most distal anatomy that the interventionalist or operator wishes to treat to the point where the guide catheter, enters the patient's body. The entry point may be located, for example, at the femoral artery in a patient's groin, or on occasion, the radial artery in a patient's arm. If the catheter being loaded over the guide wire is an OTW catheter, the guide wire must be long enough so that the entire length of the OTW catheter can be slid over the proximal end of the guide wire and yet there remain some length of the guide wire exposed where it enters the patient's body. That is, the guide wire for an OTW catheter must be approximately twice as long as one that is to be used only with RX catheters, because it must simultaneously accommodate both the length inside the patient's body and the length of the OTW catheter. Further, the “threading” of the OTW catheter over the distal or proximal end of the guide wire may be time consuming, and the added length of the guide wire can be cumbersome to handle while maintaining sterility.
Since the RX design catheters typically have the guide wire running inside them for only the most distal approximately 1 cm to approximately 30 cm, the guide wire employed need only have a little more than the required approximately 1 cm to 30 cm after it exits the patient's body. While the loading of an approximately 140 cm OTW catheter over an approximately 280 cm to 300 cm guide wire is time consuming and tedious, loading the distal approximately 10 cm of an RX catheter over a shorter guide wire is easily done.
However, OTW catheters may track the path of the guide wire more reliably than RX catheters. That is, the guide wire, acting as a rail, prevents buckling of the catheter shaft when it is pushed forward from its proximal end over the guide wire. RX catheters can, however, given a sufficiently wide target site, such as a sufficiently wide artery, and a sufficiently tortuous guide wire path, buckle as they are advanced along the guide wire by pushing on the proximal end of the catheter. In addition, when an RX catheter is withdrawn from a patient, the RX portion can pull on the guide wire and cause the guide wire to buckle near the point that it exits the proximal end of the RX channel.
Referring again to
The imaging core 402 is terminated at a proximal end by a rotational interface 432 providing electrical and mechanical coupling to an interface module (See
In alternative embodiments, rotating imaging cores may be coupled to more than two transducer subassemblies to generate images from more than two vantage points within the patient vessel.
One or more elements in embodiments of the invention may be implemented in software to execute on a processor of a computer system such as control system 106. When implemented in software, the elements of the embodiments of the invention are essentially the code segments to perform the necessary tasks. The program or code segments can be stored in a processor readable storage medium or device that may have been downloaded by way of a computer data signal embodied in a carrier wave over a transmission medium or a communication link. The processor readable storage device may include any medium that can store information including an optical medium, semiconductor medium, and magnetic medium. Processor readable storage device examples include an electronic circuit; a semiconductor device, a semiconductor memory device, a read only memory (ROM), a flash memory, an erasable programmable read only memory (EPROM); a floppy diskette, a CD-ROM, an optical disk, a hard disk, or other storage device, The code segments may be downloaded via computer networks such as the Internet, Intranet, etc.
Note that the processes and displays presented may not inherently be related to any particular computer or other apparatus. Various general-purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct a more specialized apparatus to perform the operations described. The required structure for a variety of these systems will appear as elements in the claims. In addition, the embodiments of the invention are not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the invention as described herein.
Persons skilled in the art will recognize that the apparatus, systems, and methods described above can be modified in various ways. Accordingly, persons of ordinary skill in the art will appreciate that the embodiments encompassed by the present disclosure are not limited to the particular exemplary embodiments described above. In that regard, although illustrative embodiments have been shown and described, a wide range of modification, change, and substitution is contemplated in the foregoing disclosure. It is understood that such variations may be made to the foregoing without departing from the scope of the present disclosure. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the present disclosure.
The present application claims priority to and the benefit of U.S. Provisional Patent Application No. 61/774,365, filed Mar. 7, 2013, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61774365 | Mar 2013 | US |
