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Optical coherence tomography catheter for elastographic property mapping of lumens utilizing micropalpation




Title: Optical coherence tomography catheter for elastographic property mapping of lumens utilizing micropalpation.
Abstract: An optical coherence tomography (OCT) catheter, for performing high performance elastographic deformation mapping of tissues and plaques, comprises: a catheter having elongated catheter body extending longitudinally between a proximal end and a distal end along a longitudinal axis, the catheter body including a distal portion at the distal end and a catheter lumen; a palpator, disposed in the distal portion, to apply one of a directed fluid or a mechanical indenter to produce a surface-applied palpation force to a target area of the interior body to mechanically displace the interior body and cause elastographic deformation of the target area of one or more surface and subsurface tissues and plaques; and OCT imaging sensor, disposed in the distal portion, to direct and deliver OCT beam for OCT deformation detection including elastographic deformation measurement to provide elastographic mapping of the target area. ...


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USPTO Applicaton #: #20120265062
Inventors: John Sliwa, Yu Liu


The Patent Description & Claims data below is from USPTO Patent Application 20120265062, Optical coherence tomography catheter for elastographic property mapping of lumens utilizing micropalpation.

RELATED APPLICATIONS

This application is based on and claims the benefit of U.S. Provisional Patent Application No. 61/475,173, filed Apr. 13, 2011, the entire disclosure of which is incorporated herein by reference.

BACKGROUND

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OF THE INVENTION

The present invention relates generally to medical imaging, and more specifically to a catheter having a palpator that applies a tip-directed fluid or tip-directed indenter to cause elastographic deformation and an optical coherence tomography (OCT) imager to provide high speed elastographic property mapping.

Vascular catheter based elastography palpation using OCT (OCTe) has been done using global (noninvasive) compression or using the natural blood pressure cycle as the palpation force inducing the observed tissue deformations. Such an approach tends to be slow and incapable of producing high strain gradients, thereby reducing the resolution of the elastographic property mapping and the speed at which the mapping is done. A more recent development provides a combined system that synchronizes OCT and acoustic radiation force for simultaneously imaging and mechanically displacing tissue in a patient as a detection and analytical tool. The combined system provides an endoscopic probe having a piezoelectric element that generates the acoustic force to displace the tissue and an OCT scanner that images the tissue. The mechanical displacement of the tissue can be determined and any cancer and arterial plaques can be recognized from the mechanical displacement. See U.S. Pat. No. 7,999,945.

BRIEF

SUMMARY

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OF THE INVENTION

Embodiments of the present invention provide a catheter having a palpator that applies a directed fluid or mechanical indenter to cause elastographic deformation and an OCT imager to provide high speed elastographic property mapping.

An aspect of the present invention is directed to an optical coherence tomography (OCT) catheter for performing high performance elastographic deformation mapping of tissues and plaques of an interior body. The OCT catheter comprises: a catheter having an elongated catheter body extending longitudinally between a proximal end and a distal end along a longitudinal axis, the catheter body including a distal portion at the distal end and a catheter lumen from the proximal end to the distal end; a palpator, disposed in the distal portion, to apply one of a directed fluid or a mechanical indenter to produce a surface-applied palpation force to a target area of the interior body to mechanically displace the interior body and cause elastographic deformation of the target area of one or more surface and subsurface tissues and plaques; and an OCT imaging sensor, disposed in the distal portion, to direct and deliver an OCT beam for OCT deformation detection including elastographic deformation measurement to provide elastographic mapping of the target area.

The palpator may comprise a thermal microbubble driven emitter to explosively evaporate a fluid to create one or more microbubbles which cause emission of some of the fluid to produce palpating shock waves. The palpator may comprise a flowable liquid jet or orifice to apply a directed fluid flow force for a period. In that case, the palpator is configured to generate pulse pressure in the distal portion to produce pulsed fluid palpation to apply the directed fluid flow force via the flowable liquid jet or orifice.

In some embodiments, the palpation force has a palpation force vector, and the palpation force vector and the OCT beam are substantially concentric. The palpator is configured to apply the directed fluid to produce at least one pair of palpation forces, each pair being in opposite directions. The OCT catheter further comprises a closed balloon disposed around the distal portion and being filled with a liquid that is transparent to OCT wavelengths. The closed balloon is inflatable against a surface of the interior body. Palpation by the palpator and elastographic mapping by the OCT imaging sensor are performed through a balloon wall of the balloon. The OCT catheter further comprises a biasing member to bias the distal portion against the target area of the interior body. The biasing member comprises a balloon which is inflatable to bias the distal portion against the target area of the interior body. The distal portion is in contact with the target area for delivery of the palpation force and has a shape to cause nonuniform tissue deformation and tissue shear strains that are elastographically mappable.

In specific embodiments, the OCT imaging sensor includes a movable reflector to receive light from a light source, and an actuator device to move the movable reflector in at least one of translation or rotation to direct the light to scan across the target area to illuminate the one or more surface and subsurface tissues and plaques before and during delivery of the palpation force. The OCT imaging sensor includes a lens to focus the OCT beam at a distance. The OCT catheter further comprises an acoustic imaging transducer, disposed in the distal portion, to provide ultrasonic imaging of the target area.

In some embodiments, the OCT catheter further comprises a control device to synchronize the palpation force and the OCT beam to perform OCT deformation detection including elastographic deformation measurement to provide elastographic mapping of the one or more surface and subsurface tissues and plaques. The OCT catheter further comprises an analysis module to determine displacement of the target area resulting from delivery of the palpation force. The analysis module is configured to perform OCT deformation detection in a manner which takes into account any simultaneous deformations due to blood flow or perfusion. The analysis module is configured to implement an additional optical analytical modality utilizing at least some common portion of the OCT beam's optical path to produce additional optical spectroscopic information. The analysis module is configured to provide compositional mapping of the target area using both the elastographic deformation measurement and the additional optical spectroscopic information in combination.

In specific embodiments, the OCT catheter further comprises a mechanism to change orientation of the OCT beam and the palpation force to be directed to different target areas of the interior body. The OCT catheter further comprises an analysis module to provide three dimensional mapping of the one or more surface and subsurface tissues and plaques of the interior body based on OCT deformation detection including elastographic deformation measurement by the OCT imaging sensor of the different target areas of the interior body. Deformations detected in the OCT deformation detection include both temporary deformations and permanent plastic deformations, the temporary deformations being at least one of elastic or viscoelastic.

Another aspect of the invention is directed to a method for performing elastographic deformation mapping of tissues and plaques. The method comprises: introducing a distal portion of a catheter to an interior of an interior body of a patient, the catheter including an elongated catheter body extending longitudinally between a proximal end and a distal end along a longitudinal axis, the catheter body including the distal portion at the distal end and a catheter lumen from the proximal end to the distal end; applying, from a palpator in the distal portion, one of a directed fluid or a mechanical indenter to produce a surface-applied palpation force to a target area of the interior body to mechanically displace the interior body and cause elastographic deformation of the target area of one or more surface and subsurface tissues and plaques; and directing and delivering an OCT (optical coherence tomography) beam, from an OCT imaging sensor in the distal portion, for OCT deformation detection including elastographic deformation measurement to provide elastographic mapping of the target area.

These and other features and advantages of the present invention will become apparent to those of ordinary skill in the art in view of the following detailed description of the specific embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

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FIG. 1 shows a catheter device disposed in a vessel of a patient to provide high speed elastographic property mapping of the lumen utilizing micropalpation delivered from an OCT-equipped catheter tip portion.

FIG. 2 is a partial sectional view of the distal portion of the catheter showing the fluidic palpator, OCT imaging sensor, and acoustic imaging sensor according to an embodiment of the invention.

FIG. 2A schematically illustrates an example of the OCT imaging sensor.

FIG. 3 is a partial sectional view of the distal portion of the catheter showing a balloon around the distal portion according to another embodiment of the invention.

FIG. 4A is a partial sectional view of the distal portion of the catheter showing the palpator utilizing a mechanical indenter according to another embodiment of the invention.

FIG. 4B is an enlarged view of the mechanical indenter of FIG. 4A.

DETAILED DESCRIPTION

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OF THE INVENTION

In the following detailed description of the invention, reference is made to the accompanying drawings which form a part of the disclosure, and in which are shown by way of illustration, and not of limitation, exemplary embodiments by which the invention may be practiced. In the drawings, like numerals describe substantially similar components throughout the several views. Further, it should be noted that while the detailed description provides various exemplary embodiments, as described below and as illustrated in the drawings, the present invention is not limited to the embodiments described and illustrated herein, but can extend to other embodiments, as would be known or as would become known to those skilled in the art. Reference in the specification to “one embodiment,” “this embodiment,” or “these embodiments” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention, and the appearances of these phrases in various places in the specification are not necessarily all referring to the same embodiment. Additionally, in the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that these specific details may not all be needed to practice the present invention. In other circumstances, well-known structures, materials, circuits, processes and interfaces have not been described in detail, and/or may be illustrated in block diagram form, so as to not unnecessarily obscure the present invention.

In the following description, relative orientation and placement terminology, such as the terms horizontal, vertical, left, right, top and bottom, is used. It will be appreciated that these terms refer to relative directions and placement in a two dimensional layout with respect to a given orientation of the layout. For a different orientation of the layout, different relative orientation and placement terms may be used to describe the same objects or operations.

Exemplary embodiments of the invention, as will be described in greater detail below, provide a catheter having a palpator that applies a directed fluid or, alternatively, a mechanical indenter, to cause elastographic deformation and an OCT imager to provide high speed elastographic property mapping.

FIG. 1 shows a catheter device disposed in a vessel of a patient to provide high speed elastographic property mapping of the lumen utilizing one of fluidically pressurized or indenter-based micropalpation delivered from an OCT-equipped catheter tip portion. The catheter (shown), scope or endoscopic supporting device may be introduced into a patient via a lumen, natural orifice, or manmade surgical puncture to perform one or both of a diagnostic function and a therapeutic function on an organ or tissue such as, for example, brain heart, liver, kidney, pancreas, spleen, and neural/CNS tissue. As seen in FIG. 1, the vessel 10 has a vessel wall that defines a lumen 12 such as a blood lumen. The vessel 10 is merely illustrative; the catheter device may be placed in some other cavity for mapping a different anatomy of the patient. The catheter 20 has an elongated catheter body 22 extending longitudinally between a proximal end and a distal end along a longitudinal axis. The catheter body 22 includes a distal portion or distal tip 24 at the distal end, a catheter lumen 26 from the proximal end to the distal end, and typically a handle 25 at the proximal end to manipulate or operate the catheter body 22 and/or other components such as a palpator, OCT components, sensors, and the like in the tip 24. The catheter 20 may be introduced into the lumen 12 of the vessel 10 using a guidance sheath or guiding wire (neither shown), or the like.

The catheter 20 is an OCT catheter for performing high resolution elastographic deformation mapping of tissues and plaques. The catheter 20 includes a palpator 30, disposed in the distal portion 24, to apply one of a directed fluid or a movable indenter to produce a surface-applied palpation force to a target area of an interior body such as the vessel wall to mechanically displace the interior body and cause elastographic deformation of the palpated target area of one or more surface and subsurface tissues and plaques. By “surface applied” we mean that the palpating force is directed only upon the tissue surface and that all deformations in the surface and subsurface tissue have their origin in the surface force and any inward pushing of the tissue from that surface. Clearly prior art acoustic radiation force applied at depth directly is not included in this definition. An OCT imaging sensor 34 is disposed in the distal portion 24 to direct and deliver an OCT beam for OCT deformation detection including elastographic deformation measurement to provide elastographic mapping of the target area. The deformations detected in the OCT deformation detection include both temporary elastic and/or viscoelastic deformations and possibly some permanent plastic deformations. An optional acoustic imaging sensor 36 (not used as a radiation-force palpator) is also disposed in the distal portion 24 to provide ultrasonic imaging of the target area. Thus, the device depicted in FIG. 1 is a combined OCT/IVUS catheter with OCT-based elastographic analysis capabilities. A control device 27 is provided to control operation of the components in the distal portion 24 to obtain the data for elastographic deformation mapping, as described below. An analysis module 28 is provided to analyze the data, as described below.

FIG. 2 is a partial sectional view of the distal portion 24 of the catheter 20 showing the fluidic palpator 30, OCT imaging sensor 34, and acoustic imaging sensor 36 according to an embodiment of the invention. The distal portion 24 is typically surrounded by blood, saline, contrast agent, or a mixture thereof. The acoustic imaging sensor 36 includes an acoustic transducer 40 (typically piezoceramic) and attenuative backer 42. FIG. 2 shows an outline 44 of the acoustic beam 44 from the acoustic imaging sensor 36. This optional sensor 36 acts as an intravascular ultrasound (IVUS) imaging transducer to provide measurements of lumen and vessel size, plaque area and volume, and the location of key anatomical landmarks. The ultrasound imaging can be combined with ultrasonic spectral analysis of echoes for composition and structure. For example, Volcano\'s VH® IVUS technology is marketed as helping to differentiate the four plaque types: fibrous, fibro-fatty, necrotic core and dense calcium. IVUS provides relatively far field imaging (e.g., extending to several mm) while OCT provides relatively nearer field imaging (e.g., performing best within about 2 mm) but at 10× finer resolution.

The palpator 30 of FIG. 2 applies a directed fluid to produce a fluidic palpation force or shockwaves. Relative to prior art radiation-force palpation, the inventive fluidic palpation (or indenter palpation discussed below) can apply higher forces or can apply deforming forces over a broader area from a tissue (internal or external) surface without the complexity of a focused or scanned palpation transducer. Although acoustic palpation can focus palpation at depth inside tissue, the fact is that for our lumen based applications herein, the tissues of interest are relatively shallow comprising much of the near-field lumen walls, i.e. at depth focusing is not necessary. Our fluidic (or indenter-based) palpation can provide detectable strains over a much broader region directly in front of the tip 24, while at the same time limiting the maximum strain so as to avoid rupturing fragile plaques or fibrous caps. Our fluidic and indenter palpators can also palpate without any appreciable heating of the tissue target or of the tip 24 unlike radiation-force palpation. They are ideally designed for near field tissue elastographic property mapping by applying a gently varying (therefore still locally deforming in the area of interest) nonuniform load over a wide area in front of the tip 24.




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stats Patent Info
Application #
US 20120265062 A1
Publish Date
10/18/2012
Document #
File Date
12/31/1969
USPTO Class
Other USPTO Classes
International Class
/
Drawings
0


Palpation

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20121018|20120265062|optical coherence tomography catheter for elastographic property mapping of lumens utilizing micropalpation|An optical coherence tomography (OCT) catheter, for performing high performance elastographic deformation mapping of tissues and plaques, comprises: a catheter having elongated catheter body extending longitudinally between a proximal end and a distal end along a longitudinal axis, the catheter body including a distal portion at the distal end and |St-Jude-Medical-Inc
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