Related Application

This application claims the benefit of and priority to U.S. Provisional No. 61/740,266, filed December 20, 2012, which is incorporated by reference in its entirety.

Field of the Invention

The invention generally relates to devices and methods for imaging and aspirating biological material from a vessel.

Background

Blood clots, such as emboli and thrombi, can pose serious health risks. Blood clots may form on an interior surface of a blood vessel and grow in size to occlude the blood vessel at the point of clot formation. Alternately, a portion of the clot may break free from the vessel wall, forming an embolus capable of occluding a blood vessel anywhere within the vascular system. When the obstruction occludes a vessel supplying blood to the brain, a stroke may result causing temporary or lasting paralysis of a part of the body or, in severe cases, death. Obstruction of the pulmonary artery or one of its branches can create difficulty in breathing and can potentially cause the patient to die. Blockage of other blood vessels can occur as well, causing attendant health concerns.

Interventional vascular procedures such as angioplasty, atherectomy, and stent placement, are exemplary procedures used to eliminate clots from the vasculature system. Aspiration catheters are used commonly with such procedures to aspirate debris that may result from the procedure. They are also useful in removing thrombus (clot masses) that may be present in a blood vessel before the interventional catheterization procedure is initiated. Additionally, aspiration catheters are also used to remove clots whether or not other intravascular procedures are performed. Such procedures are referred to as aspiration thrombectomy or aspiration embolectomy.

During an aspiration thrombectomy or other related procedure, contrast material is injected into a blood vessel to visualize the obstruction using an external x-ray imaging system. Once visualized, an aspiration catheter is inserted into the blood vessel and passed to the site of the obstruction. The catheter typically includes a radiopaque marker so that it also can be visualized by the external imaging system while the catheter is in the vessel. The treatment area is visualized by the external x-ray imaging system during and subsequent to the removal to ensure that the obstruction has been removed by the catheter.

A problem with known aspiration thrombectomy procedures is that there is no way to simultaneously visualize a blood clot in a vessel and remove the clot. Additionally, certain types of blood clots cannot be visualized by an angiogram.

Summary

The invention generally relates to devices and methods that allow for real-time imaging of a vessel area being treated during an aspiration thrombectomy. Aspects of the invention are accomplished by providing a device with an integrated imaging assembly. Such a device allows an operator to see a blood clot in a vessel and to the aspirate the clot while visualizing the removal with the same device. Having an imaging assembly integrated with an aspiration catheter also eliminates issues associated with aspirating too much blood or aspirating the wrong location in a vessel.

In certain aspects, devices of the invention include a body configured to fit within a lumen of a vessel, the body having an opening. Within the body there is an aspiration channel. A distal end of that channel is connected to the opening. There is also an imaging assembly coupled to the body. Devices of the present invention may be used in a variety of body lumens, including but not limited to intravascular lumens such as coronary arteries. Typically, devices of the invention are used to remove blood clots, but they may alternatively or also be used to remove one or more other materials.

The body of devices of the invention generally includes a proximal portion and a distal portion. The distal portion generally includes the opening. The opening may be located at a distal end of the body or may be located along a sidewall of the body. In certain embodiments, the opening is located on a sidewall in a distal portion of the body. The opening may be any size. The body may have any configuration that allows it to fit within a lumen of a vessel.

Generally, the opening may include a slidable cover that is closed during insertion of the device into a vessel lumen, and opened once the catheter is properly positioned near a blood clot. In certain embodiments, the device is a catheter, and the opening is located on a sidewall of the catheter.

The aspiration channel generally runs the length of the body and is coaxial with the length of the body. The aspiration channel has a distal end that is coupled to the opening, and a proximal end configured to be coupled to an aspiration device. The aspiration device may be any vacuum source known in the art. In certain embodiments, the channel may be integrally formed with the body. The channel may have any inner diameter.

The catheter body generally includes a proximal portion and a distal portion, with the distal portion having the opening. In catheter embodiments, the catheter may have many various sizes and configurations. In one embodiment, for example, the distal portion has an outer diameter of between about 0.1 cm and about 0.22 cm and the opening has a length of between about 0.12 cm and about 0.25 cm. The proximal portion and the distal portion of the catheter body typically define a channel having a longitudinal axis.

In devices and methods of the invention, an imaging assembly is coupled to the body. In certain embodiments, the imaging assembly is positioned to allow imaging of an opening in the device. Such placement of the imaging assembly greatly improves visualization during the aspiration thrombectomy procedure. Any imaging assembly may be used with devices and methods of the invention, such as opto-acoustic sensor apparatuses, intravascular ultrasound (IVUS) or optical coherence tomography (OCT).

In certain embodiments, the imaging assembly includes at least one opto-acoustic sensor.

Generally, the opto-acoustic sensor will include an optical fiber having a blazed fiber Bragg grating, a light source that transmits light through the optical fiber, and a photoacoustic transducer material positioned so that it receives light diffracted by the blazed fiber Bragg grating and emits ultrasonic imaging energy. The sensor may be positioned on an internal wall of the device, opposite the opening. In certain embodiments, the at least one sensor is a plurality of sensors and the sensors are arranged in a semi-circle.

Another aspect of the invention provides methods for imaging and removing biological material from a vessel wall that involve providing an imaging and aspirating device that includes a body configured to fit within a lumen of a vessel. Within the body there is an aspiration channel. A distal end of that channel is connected to the opening. There is also an imaging assembly coupled to the body. The method further involves inserting the device into a lumen of a vessel, and simultaneously imaging while aspirating biological material from inside the vessel that is exposed to the aspiration channel via the opening.

Brief Description of the Drawings

FIG. 1 shows an exemplary embodiment of a side view of a device of the invention in which the imaging assembly looks sideways.

FIG. 2A shows another view of FIG. 1, illustrating a guidewire in a channel that is distinct from an aspiration channel.

FIG. 2B shows another embodiment of devices of the invention in which a single channel is both an aspiration channel and a guidewire channel.

FIG. 3 shows a connector fitting that connects to devices of the invention.

FIG. 4A shows an exemplary embodiment of a side view of a device of the invention in which the imaging assembly looks sideways and is positioned to image the opening.

FIG. 4B shows an exemplary embodiment of a side view of a device of the invention in which the imaging assembly looks forward.

FIG. 5 is a schematic diagram of a conventional optical fiber.

FIG. 6 is a cross-sectional schematic diagram illustrating generally one example of a distal portion of an imaging assembly that combines an acousto-optic Fiber Bragg Grating (FBG) sensor with an photoacoustic transducer.

FIG. 7 is a schematic diagram of a Fiber Bragg Grating based sensor.

FIG. 8 is a cross-sectional schematic diagram illustrating generally one example of the operation of a blazed grating FBG photoacoustic transducer.

FIG. 9 is a schematic diagram illustrating generally one technique of generating an image by rotating the blazed FBG optical-to-acoustic and acoustic-to-optical combined transducer and displaying the resultant series of radial image lines to create a radial image.

FIG. 10 is a schematic diagram that illustrates generally a phased array example, in which the signal to/from each array transducer is combined with the signals from the other transducers to synthesize a radial image line. FIG. 11 is a schematic diagram that illustrates generally an example of a side view of a distal portion of a device.

FIG. 12 is a schematic diagram that illustrates generally one example of a cross-sectional side view of a distal portion of a device.

FIG. 13 is a block diagram illustrating generally one example of the imaging assembly and associated interface components.

FIG. 14 is a block diagram illustrating generally another example of the imaging assembly and associated interface components, including tissue characterization and image enhancement modules.

Detailed Description

The invention generally relates to devices and methods for aspirating and imaging biological material from inside a vessel. In certain embodiments, the devices and methods of the present invention are designed to aspirate blood clots, such as such as emboli and thrombi and other occlusive material from body lumens. The body lumens generally are diseased body lumens and in particular coronary arteries. The defect in the body lumen can be a de novo clot or an in-stent clot for example. The devices and methods, however, are also suitable for treating stenosis of body lumens and other hyperplastic and neoplastic conditions in other body lumens, such as the ureter, the biliary duct, respiratory passages, the pancreatic duct, the lymphatic duct, and the like. Neoplastic cell growth will often occur as a result of a tumor surrounding and intruding into a body lumen. Removal of such material can thus be beneficial to maintain patency of the body lumen. The devices and methods of the present invention can collect lumenectomy samples or materials. While the remaining discussion is directed at aspirating, imaging, and passing through atheromatous or thrombotic occlusive material in a coronary artery, it will be appreciated that the systems, devices, and methods of the present invention can be used to aspirate and/or pass through a variety of occlusive, stenotic, or hyperplastic material in a variety of body lumens.

FIG. 1 shows an exemplary embodiment of a side view of a device of the invention. Devices of the invention include a body 1000 configured to fit within a lumen of a vessel, the body having an opening 1001. Within the body 1000 there is an aspiration channel 1002. A distal end of that channel is connected to the opening 1000. There is also an imaging assembly 1003 coupled to the body 1000. FIG. 1 shows that the imaging assembly 1003 emits a signal that produces an image of an inside of a vessel. That image overlaps with the position of the opening 1001 in the body 1000. In this manner, an operator can see a blood clot in a vessel and can aspirate the clot while visualizing the removal with the same device. In this embodiment, the imaging assembly 1003 is place distal to the opening 1001. This is only an exemplary configuration of devices of the invention and other configurations will be discussed in greater detail below.

The body 1000 generally includes a proximal and a distal portion. The distal portion generally includes the opening 1001. The opening 1001 may be located at a distal end of the body 1000 or may be located along a sidewall of the body 1000. FIG. 1 shows the opening 1001 located on a sidewall of the body 1000. The body 1000 may have any configuration that allows it to fit within a lumen of a vessel. In certain embodiments, the opening 1001 may include a slidable cover (not shown) that is closed during insertion of the device into a vessel lumen, and opened once the opening 1001 is properly positioned near an obstruction.

In certain embodiments, the device is a catheter and the body is a catheter body. The catheter and catheter body are configured for intraluminal introduction to the target body lumen. The dimensions and other physical characteristics of the catheter bodies will vary significantly depending on the body lumen that is to be accessed. In the exemplary case of aspiration catheters intended for intravascular introduction, the proximal portions of the catheter bodies will typically be very flexible and suitable for introduction over a guidewire to a target site within the vasculature. In particular, catheters can be intended for "over-the-wire" introduction when a guidewire channel extends fully through the catheter body or for "rapid exchange" introduction where the guidewire channel extends only through a distal portion of the catheter body.

FIG. 1 shows an exemplary guidewire channel 1004. In the exemplary embodiment shown in FIG. 1, the guidewire channel 1004 is separate from the aspiration channel 1002.

Another view of this embodiment in shown in FIG. 2A, which shows the guidewire 1008 in a distinct guidewire channel 1004. That guidewire channel 1004 is separate from aspiration channel 1002. In other embodiments, the device is a single channel device, in which the single channel serves as both the aspiration channel and the guidewire channel. FIG. 2B shows such a device, in which the aspiration channel 1002, also accepts the guidewire 1008. Additionally, the configuration of the guidewire channel 1004 being situated below the aspiration channel 1002 in FIG. 1 is only exemplary. Any configuration of the two channels is within the scope of the invention. For example, the guidewire channel 1004 could be situated on top of the aspiration channel or the guidewire channel 1004 could be side-by- side the aspiration channel 1002. In other cases, it may be possible to provide a fixed or integral coil tip or guidewire tip on the distal portion of the catheter or even dispense with the guidewire entirely. For convenience of illustration, guide wires will not be shown in all embodiments, but it should be appreciated that they can be incorporated into any of these embodiments.

Catheter bodies intended for intravascular introduction will typically have a length in the range from 50 cm to 200 cm and an outer diameter in the range from 1 French to 12 French (0.33 mm: 1 French), usually from 3 French to 9 French. In the case of coronary catheters, the length is typically in the range from 125 cm to 200 cm, the diameter is preferably below 8 French, more preferably below 7 French, and most preferably in the range from 2 French to 7 French. Catheter bodies will typically be composed of an organic polymer that is fabricated by conventional extrusion techniques. Suitable polymers include polyvinylchloride, polyurethanes, polyesters, polytetrafluoroethylenes (PTFE), silicone rubbers, natural rubbers, and the like. Optionally, the catheter body may be reinforced with braid, helical wires, coils, axial filaments, or the like, in order to increase rotational strength, column strength, toughness, pushability, and the like.

Suitable catheter bodies may be formed by extrusion, with one or more channels being provided when desired. The catheter diameter can be modified by heat expansion and shrinkage using conventional techniques. The resulting catheters will thus be suitable for introduction to the vascular system, often the coronary arteries, by conventional techniques. Additional description of aspiration catheters is provided in each of U.S. 7,947,012; U.S. 7,942,852; and U.S.

6,719,717, the content of each of which is incorporated by reference herein in its entirety.

The distal portion of the catheters of the present invention may have a wide variety of forms and structures. In many embodiments, a distal portion of the catheter is more rigid than a proximal portion, but in other embodiments the distal portion may be equally as flexible as the proximal portion. One aspect of the present invention provides catheters having a distal portion with a reduced rigid length. The reduced rigid length can allow the catheters to access and treat tortuous vessels and small diameter body lumens. In most embodiments a rigid distal portion or housing of the catheter body will have a diameter that generally matches the proximal portion of the catheter body, however, in other embodiments, the distal portion may be larger or smaller than the flexible portion of the catheter.

A rigid distal portion of a catheter body can be formed from materials that are rigid or which have very low flexibilities, such as metals, hard plastics, composite materials, NiTi, steel with a coating such as titanium nitride, tantalum, ME-92 (antibacterial coating material), diamonds, or the like. Most usually, the distal end of the catheter body will be formed from stainless steel or platinum/iridium. The length of the rigid distal portion may vary widely, typically being in the range from 5 mm to 35 mm, more usually from 10 mm to 25 mm, and preferably between 6 mm and 8 mm. In contrast, conventional catheters typically have rigid lengths of approximately 16 mm. The opening 1001 of the present invention will typically have a length of approximately 2 mm. In other embodiments, however, the opening can be larger or smaller.

The catheter may include a flexible atraumatic distal tip coupled to the rigid distal portion of the catheter. For example, an integrated distal tip can increase the safety of the catheter by eliminating the joint between the distal tip and the catheter body. The integral tip can provide a smoother inner diameter for ease of tissue movement into a collection chamber in the tip. During manufacturing, the transition from the housing to the flexible distal tip can be finished with a polymer laminate over the material housing. No weld, crimp, or screw joint is usually required.

The atraumatic distal tip permits advancing the catheter distally through the blood vessel or other body lumen while reducing any damage caused to the body lumen by the catheter.

Typically, the distal tip will have a guidewire channel to permit the catheter to be guided to the target lesion over a guidewire. In some exemplary configurations, the atraumatic distal tip includes a coil. In some configurations the distal tip has a rounded, blunt distal end. The catheter body can be tubular and have a forward-facing circular aperture which communicates with the atraumatic tip. A collection chamber can be housed within the distal tip to store material removed from the body lumen. The combination of the rigid distal end and the flexible distal tip is approximately 30 mm.

The body 1000 includes an aspiration channel 1002 extending through the body 1000. A distal end of the channel 1002 is coupled to the opening 1001, and a proximal end of the channel is configured for connection to an aspiration device. In certain embodiments, the aspiration channel 1002 is connected to the aspiration device via a connector fitting 1005 (See FIG. 3). Connector fitting 1005 is attached at the proximal end of the body 1000. Connector fitting 1005 provides a functional access port at the proximal end of devices of the invention. Connector fitting 1005 is attached to the body 1000 and has a central passageway 1006 in communication with the aspiration channel 1002 to allow passage of various fluids, such as saline and heparin. Connector fitting 1005 further includes an adaptor 1006 in fluid communication with aspiration channel 1002 and adapted for connection to a vacuum source (not shown) to aspirate blood and particulates through aspiration channel 1002. In the field of aspiration catheters, the terms suction, vacuum, partial vacuum, reduced pressure, and negative pressure are all used

interchangeably.

The aspiration channel 1002 may include a single material or may be a multi-layer composite. In one embodiment, aspiration channel 1002 includes an outer polymeric layer, an inner polymeric layer and a reinforcement layer disposed between the outer polymeric layer and the inner polymeric layer. The inner polymeric layer defines the aspiration channel 1002.

The aspiration channel 1002 may be composed of any suitable biocompatible material or combination of materials. The outer polymeric layer and inner polymeric layer may be composed of the same or different biocompatible materials such as, for example, polyamide, polyethylene block amide copolymer (PEBA), fluoropolymers (e.g. PTFE, FEP), polyolefins (e.g.

polypropylene, high-density polyethylene), or high density polyamides.

The reinforcement layer is positioned between and is substantially coaxial with the outer polymeric layer and the inner polymeric layer. The reinforcement layer resists collapse of aspiration channel 1002 during aspiration, and enhances the torsional strength and inhibits kinking of the aspiration channel 1002 during advancement of devices of the invention within the patient's vasculature. In some embodiments of the present invention, aspiration channel 1002 includes the reinforcement layer within a proximal portion of aspiration channel 1002 and does not include the reinforcement layer in a distal region of aspiration channel 1002. The

reinforcement layer is omitted in the distal portion to increase flexibility of the distal portion of aspiration channel 1002. In various embodiments, the reinforcement layer may be formed by braiding multiple filaments or winding at least one filament over the inner polymeric layer or by applying a metal mesh over the inner polymeric layer. Braided or wound filaments may include high-modulus thermoplastic or thermo-set plastic materials, such as, for example, liquid crystal polymer (LCP), polyester, or aramid polymer. Alternatively, braided or wound filaments may comprise metal wires of stainless steel, superelastic alloys such as nitinol (TiNi), refractory metals such as tantalum, or a work-hardenable super alloy comprising nickel, cobalt, chromium and molybdenum. The reinforcing filaments may have cross sections that are round or rectangular.

The outer polymeric layer provides support to the body 1000 and coverage of the reinforcement layer. The outer polymeric layer is coaxial with the inner polymeric layer and the reinforcement layer, and may be a single or unitary tube that continuously extends from the proximal end to the distal end of aspiration channel 1002. The outer polymeric layer may be thermoplastically extruded over, and forced into any interstices in, the reinforcement layer to promote adhesion between the outer and inner polymeric layers and to encapsulate the reinforcement layer.

Devices of the invention also include an imaging assembly 1003 coupled to the body 1000. The imaging assembly may be placed distal to the opening 1001 (as shown in FIGS. 1 and 3) or positioned elsewhere, such as proximal to the opening. The imaging assembly 1003 can be angled to image perpendicular to the opening 1001 (as shown in FIG. 1) or could be angled to image just forward or behind the opening depending on the position of the imaging assembly 1003. In certain embodiments, the imaging assembly 1003 is positioned to imaging the opening 1001 in the device (FIG. 4A). In embodiments in which the opening 1001 is at a distal end of the body 1000, the imaging assembly may be placed next to the opening to image forward (FIG. 4B). In this manner, the imaging assembly can image the interaction of the removal assembly with tissue that is exposed to the imaging assembly via the opening. Such a device allows an operator to see a blood clot in a vessel and to the aspirate the clot while visualizing the removal with the same device. Having an imaging assembly integrated with an aspiration catheter also eliminates issues associated with aspirating too much blood or aspirating the wrong location in a vessel.

Any imaging assembly may be used with devices and methods of the invention, such as optical-acoustic imaging apparatus, intravascular ultrasound (IVUS), forward-looking intravascular ultrasound (FLIVUS) or optical coherence tomography (OCT).

In certain embodiments, the device is a solid state IVUS catheter (or phased array) having an array of transducer elements (for example 64 elements). The elements may be arrayed around an outside of the catheter to encircle that catheter. The aspiration channel 1002 passes through the center of the catheter and through the array of transducers. FIG. 3 is an exemplary embodiment of such a device. Solid state IVUS catheters having an array of transducer elements are further described in Yock, U.S. Pat. Nos. 4,794,931, 5,000,185, and 5,313,949; Sieben et al., U.S. Pat. Nos. 5,243,988, and 5,353,798; Crowley et al., U.S. Pat. No. 4,951,677; Pomeranz, U.S. Pat. No. 5,095,911, Griffith et al., U.S. Pat. No. 4,841,977, Maroney et al., U.S. Pat. No. 5,373,849, Born et al., U.S. Pat. No. 5,176,141, Lancee et al., U.S. Pat. No. 5,240,003, Lancee et al., U.S. Pat. No. 5,375,602, Gardineer et at., U.S. Pat. No. 5,373,845, Seward et al., Mayo Clinic Proceedings 71(7):629-635 (1996), Packer et al., Cardiostim Conference 833 (1994),

"Ultrasound Cardioscopy," Eur. J.C.P.E. 4(2): 193 (June 1994), Eberle et al., U.S. Pat. No.

5,453,575, Eberle et al., U.S. Pat. No. 5,368,037, Eberle et at., U.S. Pat. No. 5,183,048, Eberle et al., U.S. Pat. No. 5,167,233, Eberle et at., U.S. Pat. No. 4,917,097, Eberle et at., U.S. Pat. No. 5,135,486, the content of each of which is incorporated by reference herein in its entirety. As shown in FIG. 3, the transducers are arrayed at or near the distal tip.

In certain embodiments, the imaging assembly is an optical-acoustic imaging apparatus. Exemplary optical-acoustic imaging sensors are shown for example in, US 7,245,789; US

7,447,388; 7,660,492; US 8,059,923; US 2012/0108943; and US 2010/0087732, the content of each of which is incorporated by reference herein in its entirety. Additional optical-acoustic sensors are shown for example in US 6,659,957; US 7,527,594; and US 2008/0119739, the content of each of which is incorporated by reference herein in its entirety.

An exemplary optical-acoustic imaging apparatus includes a photoacoustic transducer and a blazed Fiber Bragg grating. Optical energy of a specific wavelength travels down a fiber core of optical fiber and is reflected out of the optical fiber by the blazed grating. The outwardly reflected optical energy impinges on the photoacoustic material. The photoacoustic material then generates a responsive acoustic impulse that radiates away from the photoacoustic material toward nearby biological or other material to be imaged. Acoustic energy of a specific frequency is generated by optically irradiating the photoacoustic material at a pulse rate equal to the desired acoustic frequency.

The optical-acoustic imaging apparatus utilizes at least one and generally more than one optical fiber, for example but not limited to a glass fiber at least partly composed of silicon dioxide. The basic structure of a generic optical fiber is illustrated in FIG. 5, which fiber generally consists of layered glass cylinders. There is a central cylinder called the core 1. Surrounding this is a cylindrical shell of glass, possibly multilayered, called the cladding 2. This cylinder is surrounded by some form of protective jacket 3, usually of plastic (such as acrylate). For protection from the environment and more mechanical strength than jackets alone provide, fibers are commonly incorporated into cables. Typical cables have a polyethylene sheath 4 that encases the fibers within a strength member 5 such as steel or Kevlar strands.

FIG. 6 is a cross-sectional schematic diagram illustrating generally one example of a distal portion of an imaging assembly that combines an acousto-optic Fiber Bragg Grating (FBG) sensor 100 with an photoacoustic transducer 325. The optical fiber includes a blazed Fiber Bragg grating. Fiber Bragg Gratings form an integral part of the optical fiber structure and can be written intracore during manufacture or after manufacture. As illustrated in FIG. 7, when illuminated by a broadband light laser 7, a uniform pitch Fiber Bragg Grating element 8 will reflect back a narrowband component centered about the Bragg wavelength λ given by λ =2ηλ, where n is the index of the core of the fiber and λ represents the grating period. Using a tunable laser 7 and different grating periods (each period is approximately 0.5μιη) situated in different positions on the fiber, it is possible to make independent measurement in each of the grating positions.

Referring back to FIG. 6, unlike an unblazed Bragg grating, which typically includes impressed index changes that are substantially perpendicular to the longitudinal axis of the fiber core 115 of the optical fiber 105, the blazed Bragg grating 330 includes obliquely impressed index changes that are at a nonperpendicular angle to the longitudinal axis of the optical fiber 105. As mentioned above, a standard unblazed FBG partially or substantially fully reflects optical energy of a specific wavelength traveling down the axis of the fiber core 115 of optical fiber 105 back up the same axis. Blazed FBG 330 reflects this optical energy away from the longitudinal axis of the optical fiber 105. For a particular combination of blaze angle and optical wavelength, the optical energy will leave blazed FBG 330 substantially normal (i.e.,

perpendicular) to the longitudinal axis of the optical fiber 105. In the illustrative example of FIG. 22, an optically absorptive photoacoustic material 335 (also referred to as a "photoacoustic" material) is placed on the surface of optical fiber 105. The optically absorptive photoacoustic material 335 is positioned, with respect to the blazed grating 330, so as to receive the optical energy leaving the blazed grating. The received optical energy is converted in the optically absorptive material 335 to heat that expands the optically absorptive photoacoustic material 335. The optically absorptive photoacoustic material 335 is selected to expand and contract quickly enough to create and transmit an ultrasound or other acoustic wave that is used for acoustic imaging of the region of interest.

FIG. 8 is a cross-sectional schematic diagram illustrating generally one example of the operation of photoacoustic transducer 325 using a blazed Bragg grating 330. Optical energy of a specific wavelength, λ _1; travels down the fiber core 115 of optical fiber 105 and is reflected out of the optical fiber 105 by blazed grating 330. The outwardly reflected optical energy impinges on the photoacoustic material 335. The photoacoustic material 335 then generates a responsive acoustic impulse that radiates away from the photoacoustic material 335 toward nearby biological or other material to be imaged. Acoustic energy of a specific frequency is generated by optically irradiating the photoacoustic material 335 at a pulse rate equal to the desired acoustic frequency.

In another example, the photoacoustic material 335 has a thickness 340 (in the direction in which optical energy is received from blazed Bragg grating 330) that is selected to increase the efficiency of emission of acoustic energy. In one example, thickness 340 is selected to be about 1/4 the acoustic wavelength of the material at the desired acoustic transmission/reception frequency. This improves the generation of acoustic energy by the photoacoustic material.

In yet a further example, the photoacoustic material is of a thickness 300 that is about 1/4 the acoustic wavelength of the material at the desired acoustic transmission/reception frequency, and the corresponding glass-based optical fiber sensing region resonant thickness 300 is about 1/2 the acoustic wavelength of that material at the desired acoustic transmission/reception frequency. This further improves the generation of acoustic energy by the photoacoustic material and reception of the acoustic energy by the optical fiber sensing region.

In one example of operation, light reflected from the blazed grating excites the photoacoustic material in such a way that the optical energy is efficiently converted to substantially the same acoustic frequency for which the FBG sensor is designed. The blazed FBG and photoacoustic material, in conjunction with the aforementioned FBG sensor, provide both a transmit transducer and a receive sensor, which are harmonized to create an efficient unified optical-to-acoustic-to-optical transmit/receive device. In one example, the optical wavelength for sensing is different from that used for transmission. In a further example, the optical transmit/receive frequencies are sufficiently different that the reception is not adversely affected by the transmission, and vice-versa.

FIG. 9 is a schematic diagram illustrating generally one technique of generating an image of biological material and a vessel wall 600 through an opening in a device. The technique involves rotating the blazed FBG optical-to-acoustic and acoustic-to-optical combined transducer 500 and displaying the resultant series of radial image lines to create a radial image. In another example, phased array images are created using a substantially stationary (i.e., non-rotating) set of multiple FBG sensors, such as FBG sensors 500A-J. FIG. 10 is a schematic diagram that illustrates generally one such phased array example, in which the signal to/from each array transducer 500A-J is combined with the signals from one or more other transducers 500A-J to synthesize a radial image line. In this example, other image lines are similarly synthesized from the array signals, such as by using specific changes in the signal processing used to combine these signals.

FIG. 11 is a schematic diagram that illustrates generally an example of a side view of a distal portion 800 of an elongate device 805. In this example, the distal portion 800 of the device 805 includes one or more openings 810A, 810B, . . . , 810N located slightly or considerably proximal to a distal tip 815 of the device 805. Each opening 810 includes one or more optical-to- acoustic transducers 325 and a corresponding one or more separate or integrated acoustic-to- optical FBG sensors 100. In one example, each opening 810 includes an array of blazed FBG optical-to-acoustic and acoustic-to-optical combined transducers 500 (such as illustrated in FIG. 10) located slightly proximal to distal tip 815 of device 805 having mechanical properties that allow the device 805 to be guided through a vascular or other lumen.

FIG. 12 is a schematic diagram that illustrates generally one example of a cross-sectional side view of a distal portion 900 of another device 905. In this example, optical fibers 925 are distributed around a bottom portion of device 905. In this example, the optical fibers 925 are at least partially embedded in a polymer matrix or other binder material that bonds the optical fibers 925 to the device 905. The binder material may also contribute to the torsion response of the resulting device 905. In one example, the optical fibers 925 and binder material is overcoated with a polymer or other coating 930, such as for providing abrasion resistance, optical fiber protection, and/or friction control. In one example, before the acoustic transducer(s) is fabricated, the device 905 is assembled, such as by binding the optical fibers 925 to the device 905, and optionally coating the device 905. The opto-acoustic transducer(s) are then integrated into the imaging assembly, such as by grinding one or more grooves in the device wall at locations of the opto-acoustic transducer window 810. In a further example, the depth of these groove(s) in the optical fiber(s) 925 defines the resonant structure(s) of the opto-acoustic transducer(s).

After the opto-acoustic transducer windows 810 have been defined, the FBGs added to one or more portions of the optical fiber 925 within such windows 810. In one example, the FBGs are created using an optical process in which the portion of the optical fiber 925 is exposed to a carefully controlled pattern of UV radiation that defines the Bragg gratings. Then, a photoacoustic material is deposited or otherwise added in the transducer windows 810 over respective Bragg gratings. One example of a suitable photoacoustic material is pigmented polydimethylsiloxane (PDMS), such as a mixture of PDMS, carbon black, and toluene.

FIG. 13 is a block diagram illustrating generally one example of the imaging assembly 905 and associated interface components. The block diagram of FIG. 26 includes the imaging assembly 905 that is coupled by optical coupler 1305 to an optoelectronics module 1400. The optoelectronics module 1400 is coupled to an image processing module 1405 and a user interface 1410 that includes a display providing a viewable still and/or video image of the imaging region near one or more acoustic-to-optical transducers using the acoustically-modulated optical signal received therefrom. In one example, the system 1415 illustrated in the block diagram of FIG. 13 uses an image processing module 1405 and a user interface 1410 that are substantially similar to existing acoustic imaging systems.

FIG. 14 is a block diagram illustrating generally another example of the imaging assembly 905 and associated interface components. In this example, the associated interface components include a tissue characterization module 1420 and an image enhancement module 1425. In this example, an input of tissue characterization module 1420 is coupled to an output from optoelectronics module 1400. An output of tissue characterization module 1420 is coupled to at least one of user interface 1410 or an input of image enhancement module 1425. An output of image enhancement module 1425 is coupled to user interface 1410, such as through image processing module 1405. In this example, tissue characterization module 1420 processes a signal output from optoelectronics module 1400. In one example, such signal processing assists in distinguishing blood clots from nearby vascular tissue. Such clots can be conceptualized as including, among other things, cholesterol, thrombus, and loose connective tissue that build up within a blood vessel wall. Calcified plaque typically reflects ultrasound better than the nearby vascular tissue, which results in high amplitude echoes. Soft plaques, on the other hand, produce weaker and more texturally homogeneous echoes. These and other differences distinguishing between plaque deposits and nearby vascular tissue are detected using tissue characterization signal processing techniques.

For example, such tissue characterization signal processing may include performing a spectral analysis that examines the energy of the returned ultrasound signal at various frequencies. A blood clot deposit will typically have a different spectral signature than nearby vascular tissue without such clot, allowing discrimination therebetween. Such signal processing may additionally or alternatively include statistical processing (e.g., averaging, filtering, or the like) of the returned ultrasound signal in the time domain. Other signal processing techniques known in the art of tissue characterization may also be applied. In one example, the spatial distribution of the processed returned ultrasound signal is provided to image enhancement module 1425, which provides resulting image enhancement information to image processing module 1405. In this manner, image enhancement module 1425 provides information to user interface 1410 that results in a displaying blood clots in a visually different manner (e.g., by assigning clots a discernable color on the image) than other portions of the image. Other image enhancement techniques known in the art of imaging may also be applied.

The opto-electronics module 1400 may include one or more lasers and fiber optic elements. In one example, such as where different transmit and receive wavelengths are used, a first laser is used for providing light to the imaging assembly 905 for the transmitted ultrasound, and a separate second laser is used for providing light to the imaging assembly 905 for being modulated by the received ultrasound. In this example, a fiber optic multiplexer couples each channel (associated with a particular one of the optical fibers 925) to the transmit and receive lasers and associated optics. This reduces system complexity and costs.

In one example, the sharing of transmit and receive components by multiple guidewire channels is possible at least in part because the acoustic image is acquired over a relatively short distance (e.g., millimeters). The speed of ultrasound in a human or animal body is slow enough to allow for a large number of transmit/receive cycles to be performed during the time period of one image frame. For example, at an image depth (range) of about 2 cm, it will take ultrasonic energy approximately 26 microseconds to travel from the sensor to the range limit, and back. In one such example, therefore, an about 30 microseconds transmit/receive (T/R) cycle is used. In the approximately 30 milliseconds allotted to a single image frame, up to 1,000 T/R cycles can be carried out. In one example, such a large number of T/R cycles per frame allows the system to operate as a phased array even though each sensor is accessed in sequence. Such sequential access of the photoacoustic sensors in the guidewire permits (but does not require) the use of one set of T/R opto-electronics in conjunction with a sequentially operated optical multiplexer.

In one example, instead of presenting one 2-D slice of the anatomy, the system is operated to provide a 3-D visual image that permits the viewing of a desired volume of the patient's anatomy or other imaging region of interest. This allows the physician to quickly see the detailed spatial arrangement of structures, such as lesions, with respect to other anatomy.

In one example, in which the imaging assembly 905 includes 30 sequentially- accessed optical fibers having up to 10 photoacoustic transducer windows per optical fiber, 30 x 10= 300 T/R cycles are used to collect the image information from all the openings for one image frame. This is well within the allotted 1,000 such cycles for a range of 2 cm, as discussed above. Thus, such an embodiment allows substantially simultaneous images to be obtained from all 10 openings at of each optical fiber at video rates (e.g., at about 30 frames per second for each transducer window). This allows real-time volumetric data acquisition, which offers a distinct advantage over other imaging techniques. Among other things, such real-time volumetric data acquisition allows real-time 3-D vascular imaging, including visualization of the topology of a blood vessel wall, the extent and precise location of blood clots, and, therefore, the ability to identify blood clots.

In another embodiment, the imaging assembly uses intravascular ultrasound (IVUS). IVUS imaging assemblies and processing of IVUS data are described for example in Yock, U.S. Pat. Nos. 4,794,931, 5,000,185, and 5,313,949; Sieben et al., U.S. Pat. Nos. 5,243,988, and 5,353,798; Crowley et al., U.S. Pat. No. 4,951,677; Pomeranz, U.S. Pat. No. 5,095,911, Griffith et al., U.S. Pat. No. 4,841,977, Maroney et al., U.S. Pat. No. 5,373,849, Born et al., U.S. Pat. No. 5,176,141, Lancee et al., U.S. Pat. No. 5,240,003, Lancee et al., U.S. Pat. No. 5,375,602, Gardineer et at., U.S. Pat. No. 5,373,845, Seward et al., Mayo Clinic Proceedings 71(7):629-635 (1996), Packer et al., Cardiostim Conference 833 (1994), "Ultrasound Cardioscopy," Eur.

J.C.P.E. 4(2): 193 (June 1994), Eberle et al., U.S. Pat. No. 5,453,575, Eberle et al., U.S. Pat. No. 5,368,037, Eberle et at., U.S. Pat. No. 5,183,048, Eberle et al., U.S. Pat. No. 5,167,233, Eberle et at., U.S. Pat. No. 4,917,097, Eberle et at., U.S. Pat. No. 5,135,486, and other references well known in the art relating to intraluminal ultrasound devices and modalities.

In another embodiment, the imaging assembly uses optical coherence tomography (OCT). OCT is a medical imaging methodology using a miniaturized near infrared light- emitting probe. As an optical signal acquisition and processing method, it captures micrometer- resolution, three-dimensional images from within optical scattering media (e.g., biological tissue). Recently it has also begun to be used in interventional cardiology to help diagnose coronary artery disease. OCT allows the application of interferometric technology to see from inside, for example, blood vessels, visualizing the endothelium (inner wall) of blood vessels in living individuals.

OCT systems and methods are generally described in Castella et al., U.S. Patent No.

8,108,030, Milner et al., U.S. Patent Application Publication No. 2011/0152771, Condit et al., U.S. Patent Application Publication No. 2010/0220334, Castella et al., U.S. Patent Application Publication No. 2009/0043191, Milner et al., U.S. Patent Application Publication No.

2008/0291463, and Kemp, N., U.S. Patent Application Publication No. 2008/0180683, the content of each of which is incorporated by reference in its entirety.

Some exemplary methods of the present invention will now be described. One method of the present invention includes delivering a device to a target site in the body lumen. Once at or near the target site, a slidable cover on the opening is retracted and the imaging assembly is activated. This allows the images of the tissue seen through the opening to be obtained and transmitted back to an operator prior to tissue removal.

The device can be percutaneously advanced through a guide catheter or sheath and over a conventional or imaging guidewire using conventional interventional techniques. The device can be advanced over the guidewire and out of the guide catheter to the diseased area. If there is a cover, the opening will typically be closed. Although, a cover is not required. The device will typically have at least one hinge or pivot connection to allow pivoting about one or more axes of rotation to enhance the delivery of the catheter into the tortuous anatomy without dislodging the guide catheter or other sheath. The device can be positioned proximal of the blood clot.

Once positioned, biological material may be removed from the body lumen by activating the aspirating device, which causes suction within the aspiration channel of the device. In some embodiments that include a cover, the cover is first retracted. Thereafter, the operator can move the entire device through the lumen, using the imaging data to guide the operator. The device is then used to aspirate the blood clot or other biological material to be removed from the inside of the vessel. When it is determined that the blood clot or other obstructive material has been removed, the catheter can be removed from the body lumen. The removed clot or other obstructive material may be stored or tested as needed.

Incorporation by Reference

References and citations to other documents, such as patents, patent applications, patent publications, journals, books, papers, web contents, have been made throughout this disclosure. All such documents are hereby incorporated herein by reference in their entirety for all purposes.

Equivalents

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting on the invention described herein. Scope of the invention is thus indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.