OPTICAL IMAGING CATHETER FOR ABERRATION BALANCING
An Optical imaging catheter that balances optical aberrations and allows recording of high quality optical images while relaxing the requirement of a fluid occupying the space between the prism and the inner sheath of the catheter.
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This application claims priority to PCT application No. PCT/US2009/043183, which was filed May 7, 2009 and which claims priority to U.S. Provisional application Ser. No. 61/051,340, which was filed May 7, 2008, and claims priority to U.S. patent application Ser. No. 12/172,922, which was filed Jul. 14, 2008 and claims priority to U.S. provisional application Ser. No. 60/949,511, which was filed Jul. 12, 2007, all herein incorporated by reference.
BACKGROUND OF THE INVENTIONThe present invention relates generally to an apparatus for in vivo imaging, and more particularly, pertains to a catheter for optical imaging within luminal systems, such as imaging the vasculature system, including, without limitation, cardiovascular, neurovascular, gastrointestinal, genitor-urinary tract, or other anatomical luminal structures.
Still more specifically, the present invention relates to an imaging catheter that does not require an optical transmitter placed between the prism and the outer sheath of the catheter. Typically, a fluid with an index of refraction is matched to the medium exterior the catheter to prevent image distortion due to astigmatism, and the like. The present invention solves these problems, as well as others.
SUMMARY OF THE INVENTIONThe Optical imaging catheter substantially reduces the composite optical aberrations in optical imaging, such as astigmatism, by balancing the contributions of each optical interface to any optical aberrations. By aberration balancing, the Optical imaging catheter provides good imaging performance without introducing a fluid in the space between the prism and inner surface of the outer catheter sheath. The aberration balancing is accomplished through the contributions of the various optical interfaces including, but not limited to, the following elements: a prism/gas (air), a gas/inner surface of the outer catheter sheath interface, and an outer surface of catheter sheath/flush material interface.
Generally speaking, the Optical imaging catheter 100 is shown in
The optical catheter 100 is optically coupled to an imaging modality for imaging of anatomical passageways, such as cardiovascular, neurovascular, gastrointestinal, genitor-urinary tract, or other anatomical luminal structures. In one embodiment, the imaging modality is an Optical Coherence Tomography (“OCT”) system. OCT is an optical interferometric technique for imaging subsurface tissue structure with micrometer-scale resolution. Alternative optical imaging modalities include spectroscopy, optical therapies, Raman spectroscopy, and the like. In another embodiment, the imaging modality is an ultrasound imaging modality, such as intravascular ultrasound (“IVUS), either alone or in combination with OCT imaging. The OCT system may include tunable light source, a tunable laser, a broadband light source, or a tunable superluminescent diode, or multiple tunable light sources with corresponding detectors, may be a spectrometer based OCT system or a Fourier Domain OCT system, as disclosed in U.S. application Ser. No. 12/172,980, herein incorporated by reference, or may be a Doppler OCT system. The Optical imaging catheter may be integrated with IVUS by an OCT-IVUS catheter for concurrent imaging, as described in U.S. application Ser. No. 12/173,004, herein incorporated by reference. Alternatively, the imaging modality may be spectroscopic, ultrasound or IVUS, therapeutic modalities, diagnostic modalities, or alternative imaging modalities.
As shown in
A number of factors can contribute to the optical aberrations, such as spherical aberration, coma, astigmatism, field curvature, chromatic aberration, distortion, and the like, in the Optical imaging catheter system. Astigmatism occurs with different focal lengths for rays of different orientations, resulting in a distortion of the image. In particular, rays of light in horizontal and vertical planes are not focused at the same plane. Chromatic aberration occurs when bringing different colors or wavelengths of light that are focused at different points. Distortion is caused because the transverse magnification may be a function of the off-axis image distance. Distortion is classified as positive (so-called pincushion distortion), or negative (so-called barrel distortion). Field curvature (a.k.a. Petzval field curvature) results because the focal plane is actually not planar, but spherical. Field curvature and distortion are not typically of concern for catheter-based designs in which the entire optical system is moved for each point; and these would be considered if, for example, the lens was stationary and some other scanning element moved in order to point the beam at the location of interest. Spherical aberration commonly occurs in a spherical lens or mirror because these do not focus parallel rays to a point, but instead along a line. Therefore, off-axis rays are brought to a focus closer to the lens or minor than are on-axis rays. Spherical aberration can have a sign—positive or negative.
The Optical imaging catheter balances the optical aberrations due to different surfaces at the optical interfaces so that the composite aberration or total aberration is substantially reduced or nearly zero. The Optical imaging catheter system reduces optical aberrations such as astigmatism, by aberration balancing all of the optical interfaces while maintaining the space 130 between the prism and inner surface of the catheter sheath filled with air.
There is an assumption that air at the inner catheter 122 and prism 110 interface, the cylinder of the sheath 120 distorts the optical image and introduces astigmatism and other optical aberrations into the optics of the catheter making the system unsuitable for imaging. Typically, a fluid is introduced into space between the inner surface 122 and prism 110 interface to reduce the optical power of the inner surface 122 of the catheter sheath. Reduction of the optical power of the inner surface of the catheter sheath 122 reduces optical aberrations (e.g., astigmatism) so as to prevent the OCT image quality from being altered. By not including the fluid in the space 130 between the prism 110 and inner surface 122 of the catheter sheath, a reduction of NURD, maintaining sterility of the catheter environment, and relaxing requirement for additional ports to allow air and some index-matched fluid to exit the distal end of the catheter are implicated for the Optical imaging catheter 100.
The magnitude of aberrations introduced at each surface is dependent on the curvature of the surface, tilt or angular orientation of the surface, difference in refractive index of materials on each side of the interface. For a spherical surface, the optical power is given by power=(n_1−n_2)/R where n_1 is refractive index of the first material, n_2 is the refractive index of the second material and R is the radius of curvature. The curvature of a surface may be anisotropic where the principal surface curvatures are unequal. The inner surface 122 of the catheter sheath is a surface with anisotropic curvature, because the curvature in a plane perpendicular to longitudinal axis of the catheter is not equal to the curvature in a plane containing the longitudinal axis of the catheter. Surfaces with anisotropic curvature introduce astigmatism (one of the third order Seidel aberrations).
Alternatively, the index mismatch between the air in the space 130 and inner surface 122 of the catheter sheath may contribute to clear images, when not including a fluid in the space 130 between the prism 110 and the inner surface 124 of the catheter sheath. When a gas (such as air) occupies the space 130 between the prism 110 and inner surface 122 of the catheter sheath, the anisotropic curvature of the inner surface 122 of the catheter sheath introduces astigmatism and other aberrations into the optical radiation 118. The outer surface 124 of the catheter can also introduce optical aberrations if the flushing fluid is not index matched to the catheter outer sheath material.
In the Optical imaging catheter 100, the space 130 between the prism 110 and inner surface 124 of the outer catheter sheath is occupied by a gas and the aberrations introduced by the inner surface 124 of the outer catheter sheath are balanced by configuring other elements of the catheter. For example, by tilting the prism by an angle of 1-10 degrees off the y-axis or x-axis so that light exiting the prism is not directed perpendicular to the longitudinal axis of the Optical imaging catheter, as shown in
Alternatively, the prism 110 and lens 150 may be a bi-cylindrical integrated micromirror/microlens 162 for collecting, redirecting, and focusing light, as shown in
Alternatively, the prism 110 comprises a toroidal minor to collect light diverging longitudinally out of a fiber optic cable, redirect the light with a radial component (in the y-axis), and then refocus the light onto a sample. The toroidal minor includes a mirrored surface with a toroidal surface to collect and refocus and a tilt to introduce radial component. The toroidal surface is not spherical or parabolic and compensates for astigmatism introduced by tilting the reflecting element. The toroidal surface can also be designed to compensate for astigmatism introduced into the beam by an encapsulating cylindrical element. The toroidal mirror can be rotated for cylindrical/radial scanning apparatus, or translated longitudinally for linear scanning apparatus. The toroidal minor's mirrored surface can be on concave (air) side or substrate (convex) side of element and the mirrored surface could include a metallic coating similar to any standard mirror.
Alternatively, the prism 100 comprises a curved output face with a radius of curvature similar to that of the optical fiber or inner surface 122 or radius of the catheter sheath. In this design, the prism 110 curved output face and the inner surface 122 of the catheter sheath act as a negative and positive lens, cancelling out the majority of the focusing power in this lateral dimension and eliminating much (not all) of the advantage of a fluid filled catheter design.
In another embodiment, the refractive index of the catheter sheath 120 material may be selected to control the aberrations introduced at the inner surface 122 of the outer catheter sheath and the outer surface 124 of the outer catheter sheath. In one embodiment, a polymer with a refractive index equal to 1.34 may be used. The polymer of the sheath is detailed below, such as perfluoroalkoxy (PFA) polymer, polytetrafluoroethylene (PTFE) partially covered with a polyether block amide (Pebax®) at the distal end, or tetrafluoroethylene and hexafloropropylene co-polymer (FEP), and the like. Alternatively, the catheter sheath 120 may include a refractive index similar to the medium outside exterior surface 168 at which the catheter is imaging, such as saline or blood. Alternatively, the catheter sheath 120 may have a refractive index so that the aberrations (astigmatism) of the flush-sheath material balance other aberrations in the imaging system.
In one embodiment, the catheter sheath may include an index of refraction between about 1.29 to 1.39; alternatively, between about 1.30 to 1.38; alternatively, between about 1.31 to 1.37; alternatively, between about 1.30-1.39. In one embodiment, the catheter sheath 120 includes a reduced refractive index, which is approximately 1.34. The inner surface 122 of the catheter sheath includes a radius of curvature, where the radius of curvature is larger than the outer surface 124 of the catheter sheath, and where a smaller radius results in more optical power.
Air, catheter sheath material, and the fluid material each has an optical power contributing or affecting the refractive index. The optical power is equal to the index of refraction divided by the radius of the surface. The optical power of the inner surface may be related by Equation (1):
index of sheath−index of air=optical power of the inner surface (1) radius of the inner surface
The optical power of the outer surface of the sheath may be related by Equation (2)
index of flushing agent−index of outer surface=optical power of the outer surface (2) radius of the outer surface
The two optical powers of the inner and outer surface may cancel each other or provide for compensating optical power as to reduce aberrations. In one embodiment, the absolute value of the optical power of the inner surface 122 is higher than the outer surface 124 because the radius of the inner surface is shorter than the outer surface, as discussed below.
The cylindrical lens effects of the sheath are shown in
In one embodiment, the R1 is between about 0.3000 to 0.4000 mm; alternatively, between about 0.3100 to 0.3900 mm; alternatively, between about 0.3200 to abut 0.3800 mm; alternatively, about 0.3302 mm. In one embodiment, the R2 is between about 0.4100 to 0.5100 mm; alternatively between about 0.4200 to 0.5000 mm; alternatively, between about 0.4400 to 0.4900 mm; alternatively, about 0.4826. In one embodiment, the capsule thickness T is between about 0.1300 to 0.1700 mm; alternatively, between about 0.1400 to 0.1600 mm; alternatively, between about 0.1500 to 0.1599 mm; alternatively about 0.1524 mm. In one embodiment, the thickness T contributes to maintaining a ratio between R1 and R2, such that the ratio of R1:R2 is between about 0.60 to 0.80; alternatively, between about 0.65 to 0.75; alternatively between about 0.67 to 0.70; alternatively about 0.68. In one embodiment, the cylindrical surface of the inner surface 122 of the outer sheath contributes to an optical power and the cylindrical surface of the outer surface 124 of the outer sheath contributes to an optical power. The optical power of the inner surface 122 is cancelled by the optical power of the outer surface 124 to prevent any major detriments or aberrations to the imaging quality of the Optical imaging catheter system. Therefore, the index-matching of the sheath material to the sample medium is no longer necessary. If the flush material has a small refractive index compared to the catheter sheath material then some aberration balancing is obtained.
Alternatively, the optical power given by a flushing fluid, for example, saline or a blood-substitute, which may have an index of refraction of ˜1.3, then the sheath 120 is made with a similar index of refraction, i.e., ˜1.3 by varying the optical power of the inner surface 122 and the outer surface 124 of outer sheath. The differences between the refractive indices of the sample medium, the air between the sheath and the prism is accounted for by the optical power of the catheter sheath 120. Lenses that have an aspheric surface are also within the scope of the embodiments. Aspheric lenses are most easily made using the reflow technology generally known in the art.
Optical Imaging Catheter System
With particular reference to
The catheter system 10 construct for in vivo imaging, particularly, imaging of anatomical passageways, such as cardiovascular, neurovascular, gastrointestinal, genitor-urinary tract, or other anatomical luminal structures. The catheter 10 is coupled to an imaging modality, and in one embodiment the imaging modality is an Optical Coherence Tomography (“OCT”) system. OCT is an optical interferometric technique for imaging subsurface tissue structure with micrometer-scale resolution. In another embodiment, the imaging modality is an ultrasound imaging modality, such as intravascular ultrasound (“IVUS), either alone or in combination with OCT imaging. The OCT system may include tunable laser or broadband light source or multiple tunable laser sources with corresponding detectors, and may be a spectrometer based OCT system or a Fourier Domain OCT system, as disclosed in U.S. Provisional Application 60/949,467, herein incorporated by reference. The catheter system 10 may be integrated with IVUS by an OCT-IVUS catheter for concurrent imaging, as described in U.S. Provisional Application 60/949,472, herein incorporated by reference. As shown in
As shown in
The rotary drive shaft 40 is concentrically or coaxially positioned within the central lumen of the monolithic outer sheath 120 and substantially extends along the longitudinal length D of the central lumen. Coaxially engagement between the rotary drive shaft 40 and the central lumen of the monolithic outer sheath 120 may be accomplished with the OD of the rotary drive shaft 40 matching the ID of the monolithic outer sheath 120 or varying the OD of the rotary drive shaft to the ID of the monolithic outer sheath 120. The rotary drive shaft 40 terminates at its distal end in proximity to the distal end of the central lumen adjacent the proximal end of the catheter 10. The optical train 30 is carried by the rotary drive shaft 40, with the optical fiber 50 running the length of the rotary drive shaft 40 through the drive shaft lumen. The rotary drive shaft 40 permits transmission of torque from the rotary motor to the optical train 30 along the entire length of the catheter shaft. As such, the rotary dive shaft 40 includes having sufficient torsional rigidity or torqueability and lateral flexibility or flexion to navigate potentially tortuous anatomical pathways while minimizing NURD to ensure accurate imaging. Torqueability is the ability of the rotary drive shaft to be turned or rotated while traversing bends or turns in the patient's vasculature.
In one embodiment, the rotary drive shaft 40 includes a hypotube metal over a proximal portion or the entire proximal section of the rotary drive shaft 40. Alternatively, the rotary drive shaft 40 includes a stranded hollow core shaft extending the substantial length of the rotary drive shaft 40. The stranded hollow core shaft may comprise a plurality of helically wound wire strands so that mechanical rotation of the rotary drive shaft is in the same direction as the helical wire strands. The stranded hollow core shaft may include an inner stranded drive shaft and outer stranded drive shaft, where in outer stranded drive shaft is wound in the opposite helical direction than the inner stranded drive shaft. The protection bearing 170 may be coupled to either the stranded hollow core shaft or the hypotube metal. The stranded hollow core shaft, the hypotube metal, or a combination thereof provides sufficient lateral flexibility to ensure access through highly tortuous passageways, such as the aortic arch and coronary arteries. In another embodiment, the hypotube metal is concentrically or coaxially fitted over a proximal portion or the entire proximal section of the stranded hollow core shaft. The coaxial fitting of the hypotube metal over the stranded hollow core shaft may be accomplished by allowing the OD of the stranded hollow core shaft to vary from the ID of the hypotube metal tube by about 0.001 to 0.009 inches. In this manner the highly flexible stranded hollow core shaft lessens NURD by the relatively less flexible hypotube metal at the more distal end of the catheter to permit greater distal end flexion or lateral flexibility. While maintaining flexibility, the rotary drive shaft also maintains the pushability, the ability of the catheter to be efficiently and easily pushed through the vasculature of the patient without damage to the catheter or patient, getting blocked, kinked, whipped, etc.
In accordance with another embodiment, the rotary drive shaft 40 includes a shortened hypotube metal shaft attached in a generally overlapping attachment with a section of stranded hollow core shaft, with there being a very slight mismatch in the outer diameters between the hypotube metal and the stranded hollow core shaft to permit concentric or coaxial engagement and attachment between the respective end sections. Alternatively, the hypotube metal and the stranded hollow core shaft may have generally the same outer diameter to permit end-to-end connection, such as a butt weld there between. The stranded hollow core shaft includes single layer uni-directional and multi-layer directional winding configurations when coupled to the hypotube metal shaft.
In one embodiment of the monolithic outer sheath 120, at least a portion of the monolithic outer sheath is fabricated of an optically transparent polymer, such as, for example, perfluoroalkoxy (PFA) polymer, polytetrafluoroethylene (PTFE) partially covered with a polyether block amide (Pebax®) at the distal end, or tetrafluoroethylene and hexafloropropylene co-polymer (FEP). The optically transparent polymer is transparent in the spectral region of light being used for imaging. Similar biocompatible optically transparent polymers having similar properties of lubricity, flexibility, optical clarity, biocompatible and sterilizability may alternatively be employed to form the catheter shaft. In accordance with one embodiment, FEP is used to fabricate the catheter sheath. The catheter sheath is fabricated in a monolithic manner such that the central lumen terminates at the atraumatic monolithic tip without any intervening joints. Atraumatic is not producing injury or damage. As shown in
As shown in
In accordance with a another embodiment, the rotary drive shaft 40 includes the protection bearing 170, which houses the distal end optics or distal end acoustics at the distal end of the catheter 10, as shown in
In accordance with one embodiment, the optical train 30 includes the monolithic outer sheath 120 the optical fiber 50 in association with the rotary drive shaft 40, the protection bearing 170 housing a ferrule/gradient index lens (“GRIN”) assembly 80 at a distal end of the optical fiber 50, as shown in
As shown in
Some of the incident light may not be redirected radially outward. The prism angles may be constructed to provide a balancing of astigmatism introduced by the catheter sheath. The incident light may not necessarily all be used for imaging, where additional optical energy beams are for therapeutic purposes or possibly some other energy source, as disclosed in commonly assigned application entitled “Method and Apparatus for Simultaneous Hemoglobin Reflectivity Measurement and OCT Scan of Coronary Arteries, Thrombus Detection and Treatment, and OCT Flushing”, PCT application No. PCT/US2009/038832, filed Mar. 30, 2009, herein incorporated by reference.
Catheter Sheath
As shown in
The guidewire lumen 256, as shown in phantom depicted in
The monolithic outer sheath 120 includes the absence of or potential for uneven surfaces that may irritate or damage tissues in anatomical passageways or interfere with the guiding catheter during retraction or advancement of the catheter, the absence of joints which could separate and dangerously embolize, and the absence of joints which could leak fluid into or out of the sheath. Because of its monolithic construction, the central lumen of the outer catheter sheath may be filled with air or a fluid that could serve to (a) provide lubrication between the monolithic outer sheath and the rotary shaft, (b) reduce optical astigmatism originating from the cylindrical curvature of the inner sheath surface due to the lower index of refraction mismatch of liquid when compared with air, (c) provide additional column strength and kink resistance to the catheter, (d) viscously dampen NURD, or (e) provide negative torsional feedback to stabilize or dampen non-uniformities in rotation.
The monolithic design of the catheter outer sheath and the monolithic atraumatic tip further permit different engineering of material properties along the length of the monolithic outer sheath. For example, the durometer of the catheter sheath may be varied along the length of the catheter sheath during manufacture of the sheath precursor material; the inner and/or outer diameter of the catheter sheath may be made to vary, such as by tapering, along the length of the continuous monolithic tube; the wall thicknesses of the catheter sheath and the concomitant flexibility profiles may be varied along the longitudinal length of the catheter sheath, or the catheter sheath may be variably reinforced to alter the flexibility profiles along the longitudinal axis of the catheter sheath, such as by applying a braiding material, a concentric reinforcement, such as another overlaid tube, or combinations of the foregoing. The braiding material may be a polymer formed from conventional braiding machines. The durometer is the hardness of the material, as defined as the material's resistance to permanent indentation. The two most common scales, using slightly different measurement systems, are the ASTM D2240 type A and type D scales. The A scale is for softer plastics, while the D scale is for harder ones. However, the ASTM D2240-00 testing standard calls for a total of 12 scales, depending on the intended use; types A, B, C, D, DO, E, M, O, OO, OOO, OOO-S, and R. Each scale results in a value between 0 and 100, with higher values indicating a harder material.
Rotary Drive Shaft
Turning now to
As shown in
The distal part of the rotary drive shaft 40 may be the stranded hollow core 500 design, where flexibility is required at the entry point to the body. From the proximal portion to the distal portion of the rotary drive shaft 40, a single layer or double layer wound stranded hollow core may be included at the proximal portion, a hypotube metal drive shaft 400, and a single layer or double layer wound at the distal portion as to have a flexible distal tip.
The hypotube metal drive shaft 400 may include a solid wall extending substantially the entire longitudinal length of the central lumen of the rotary drive shaft 40 in combination with the stranded hollow core shaft 500, which (a) increases torsional rigidity of the rotating shaft and reduces NURD; (b) increases column strength or axial rigidity to improve the pushability of the catheter assembly; (c) reduces or eliminates the possibility of the stranded or coiled hollow core shaft unraveling or disassociating under the torsional forces applied; (d) improves the frictional interface by replacing an interrupted or more concentrated load transference between individual strands and the monolithic outer sheath with a continuous and more distributed load across the solid-walled hypotube metal shaft; and (e) the hypotube metal shaft offers a good fluid seal against the monolithic outer sheath over the proximal section of a fluid-filled catheter due to the solid-walled design.
The solid-walled hypotube metal drive shaft 400 may, alternatively be used in conjunction with the stranded hollow core shaft by either butt-joining a distal end of the hypotube metal shaft 400 onto a proximal end of the stranded hollow core shaft 500, as illustrated in
Longer sections of the hypotube metal shaft 400 may be employed proximal of the rotary drive shaft 40 to achieve a greater reduction of NURD. Due to its relative rigidity, the length of the hypotube metal shaft 400 should not extend too far distally so as to interfere with the distal flexibility of the catheter and prevent it from navigating tortuous anatomical passageways. The wall-thickness of the hypotube metal shaft 400 may be varied along its length to impart variable stiffness along the longitudinal axis of the hypotube metal shaft 400. In this manner, relatively thinner wall-thicknesses may be formed distally than those formed more proximally, to impart greater flexibility at the distal end of the hypotube metal shaft 400. The wall thickness may be varied by extrusion processing, mechanical means, such as grinding, abrasive blasting, turning, by chemical or electrochemical means, such as electro-polishing or etching, or by combinations of the foregoing. Alternatively, slots, holes or other aperture shape formations may be formed by means of cutting, etching, ablating or other means to generate designs in the tubular structure which permit additional flexibility of the distal region of the hypotube metal shaft 400 while retaining substantial torsional rigidity.
The rotary drive shaft 40 design can include the following considerations: (1) the material type and geometry of the material that comprise a given segment; and (2) a number of distinct material segments when progressing from the proximal to distal portions of the catheter.
In one embodiment, the design of the rotary drive shaft 40 includes setting the lateral flexibility of the material at the proximal end to a specific point and increasing the lateral flexibility from the proximal end to the distal segments of the rotary drive shaft. Generally speaking, a higher lateral flexibility is desired in portions of the catheter that experience the greatest geometric curvature when used for imaging. In addition, the diameter of the rotary drive shaft may become gradually or stepwise smaller from the proximal end to the distal portions of the rotary drive shaft. By reducing the wall thickness or by reducing the ID and OD or both the ID and OD, the diameter of the rotary drive shaft becomes smaller. The geometry of catheter at the surgical entry point and the geometry of the human coronary tract generally put these regions at the surgical entry point to the body and the aortic arch and the coronary blood vessel being interrogated.
The material type and the geometry of the materials in a given segment may vary in the rotary drive shaft. Different geometries are recognized for a given segment of the rotary drive shaft. Examples include, but are not limited to: (1) homogeneous solid (e.g., nitinol, PEEK, or some polymer); (2) stranded hollow core shaft (single wound, double counter-wound, or triple coil-wound or generally multiple wound); (3) braided multi-stranded hollow core shaft; (4) fibrous composite (fibers in a matrix); (5) patterned solid (#1 with patterned holes or apertures); and (6) patterned composite (#4 with patterned holes or apertures).
In one embodiment, the number of distinct segments may vary. A two segment rotary drive shaft includes the metal hypotube shaft in the proximal portion and a stranded hollow core at the distal portion. Other possibilities and combinations include, but are not limited to: (1) metal hypotube shaft proximal, and patterned metal hypotube shaft distal with a selected hole pattern, where the lateral flexibility of the solid metal hypotube shaft and patterned metal hypotube shaft may be graded when going from proximal to distal portions for increased flexibility; (2) a filament wound or fiber reinforced composite material at the proximal end with increased fiber density and a composite material at the distal end with a decreased fiber density (i.e., with increased lateral flexibility) or a fiber density that is graded downward going from the proximal end to the distal end; (3) a composite material at the proximal end with increased fiber density, nitinol in the mid-portion and stranded hollow core at the distal end. The joints between any segments may be joined end-to-end with for example a butt-couple, weld, epoxy or other jointing technique. Alternately, an overlapping style of joint may be used, i.e. male-female joints, or by coaxial engagement, concentric alignment, and the like. Connection of the segments of an overlapping style of joint may be accomplished by means of welding, adhesive, or over-molding given that at least one element is polymer.
In addition, a gradation, either gradual or stepwise, may be accomplished by a change in material properties along the length of the rotary drive shaft. For example, the material properties may be adjusted such as the modulus of elasticity of the material via methods including, but not limited to annealing, carburization, or heat treat and subsequent quenching techniques. In the case of nitinol, one may adjust the transition temperature (Af) along the length by means of heat treatment, cold working, or some combination thereof. Mf is the temperature at which the transition to Martensite is finished during cooling. Accordingly, during heating As and Af are the temperatures at which the transformation from Martensite to Austenite starts and finishes. Nitinol is typically composed of approximately 50 to 55.6% nickel by weight. Making small changes in the composition can change the transition temperature of the alloy significantly. For this reason, nitinol may or may not be superelastic at certain temperatures, thus allowing the modulus of elasticity to be adjusted according to the temperature of use.
The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the articles, devices, systems, and/or methods claimed herein are made and evaluated, and are intended to be purely exemplary and are not intended to limit the scope of articles, systems, and/or methods. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), but some errors and deviations should be accounted for.
Resolution Mask
A resolution mask may be used to determine the resolution of the OCT image. The resolution mask is formed from a material with a sheet or planar geometry immersed in a scattering medial with alternating spatial regions of high/low reflectivity. The alternating regions of high/low reflectivity have a fixed spatial period and allow testing the lateral spatial resolving power of the OCT catheter imaging system. On an OCT image the resolution mask appear as the lined images on the lower side of the OCT image and are measured such that the length indicated is the resolution from leading edge of one line to the leading edge of the next line. In other words, the length indicated is 2 times the line width, such that a 50 μm line width mask would consist of a 50 μm line with high reflection and a 50 μm line with low reflection or a 100 μm resolution mask.
Zemax Modeling
The optical imaging catheter design was modeled in Zemax Modeling software (Zemax Development Corporation, Bellevue, Wash.) using a GRIN lens design for the lens 150 (GrinTech, Jena, Germany), a BK7 glass for the prism 110, and a refractive index of n=1.34 for the catheter sheath 120 constructed from FEP, as shown in
The catheter system is modeled using ray-tracing with all rays in a sequential format. Modeling of multiple scattering/reflection events within an element is not included. As a result of the prism 110, which by design has a second reflection or scattering event at the angled face, is modeled as two standard surfaces with a zero-width fold-mirror between them. The Zemax simulation represents a realistic model of the system in terms of optical path, diffraction, and dispersion.
The surfaces following the prism are modeled as toroidal geometries with a defined radius of curvature and an infinite radius of rotation, making them essentially cylindrical lenses consistent with the sheath geometry. The image plane is also considered a cylindrical surface in this system, with a radius of curvature given by distance from the central axis.
As shown
In the orthogonal lateral dimension (along the x-axis of the catheter), the catheter axial dimension, the resolution is approximately 25 μm for both filled and unfilled cases.
While the embodiments have been described, it will be understood that the invention is capable of further modifications. This application is intended to cover any variations, uses or adaptations of the invention following, in general, the principles of the invention, and including such departures from the present disclosure as, within the known and customary practice within the art to which the invention pertains.
Claims
1. An optical imaging catheter comprising:
- a prism to receive and direct optical radiation through a catheter sheath; and
- a space is between the prism and the catheter sheath to balance optical aberrations in optical images obtained from a sample.
2. The catheter of claim 1, wherein the space is occupied by air or gas.
3. The catheter of claim 1, wherein the catheter sheath includes an inner surface and an outer surface, wherein the inner surface and outer surface include an optical power and a refractive index.
4. The catheter of claim 3, wherein the absolute value of the optical power of the inner surface is higher than the outer surface.
5. The catheter of claim 3, wherein the catheter sheath includes a refractive index matched to the refractive index of a medium exterior the outer surface.
6. The catheter of claim 3, wherein the inner surface includes a radius between about 0.3000 to 0.4000 mm and the outer surface includes a radius between about between about 0.4100 to 0.5100 mm.
7. The catheter of claim 1, wherein the prism includes a bi-cylindrical micromirror/microlens comprising a reflective cylindrical surface to collect the optical radiation diverging longitudinally out of an optical fiber and redirect the optical radiation with a cylindrical surface into a radial component, and a second cylindrical transmissive/lensing surface to focus the optical radiation along an axis orthogonal to the longitudinal axis of the catheter body.
8. The catheter of claim 1, wherein the prism is a toroidal minor including a mirrored surface with a toroidal surface to collect, refocus, and tilt the optical radiation into a radial component non-perpendicular with the longitudinal axis of the catheter body.
9. The catheter of claim 1, wherein the catheter is coupled to an imaging modality.
10. A method for performing optical imaging through a catheter, comprising:
- directing optical radiation through a prism and a catheter sheath, wherein a space is between the prism and the catheter sheath to balance optical aberrations in an optical image obtained from a sample.
11. The catheter of claim 10, wherein the space is occupied by air or gas.
12. The method of claim 10, wherein the catheter sheath includes an index of refraction matched to the refractive index of a medium exterior the outer surface of the catheter sheath.
13. The method of claim 10, wherein the catheter sheath includes an inner surface and an outer surface, wherein the inner surface and outer surface include an optical power and a refractive index.
14. The method of claim 13, wherein the absolute value of the optical power of the inner surface is higher than the outer surface.
15. The method of claim 13, wherein the catheter sheath includes a refractive index matched to the refractive index of a medium exterior the outer surface.
16. The method of claim 13, wherein the inner surface includes a radius between about 0.3000 to 0.4000 mm and the outer surface includes a radius between about between about 0.4100 to 0.5100 mm.
17. The method of claim 10, wherein the prism includes a bi-cylindrical micromirror/microlens comprising a reflective cylindrical surface to collect the optical radiation diverging longitudinally out of an optical fiber and redirect the optical radiation with a cylindrical surface into a radial component, and a second cylindrical transmissive/lensing surface to focus the optical radiation along an axis orthogonal to the longitudinal axis of the catheter body.
18. The method of claim 10, wherein the prism is a toroidal minor including a mirrored surface with a toroidal surface to collect, refocus, and tilt the optical radiation into a radial component non-perpendicular with the longitudinal axis of the catheter body.
19. The method of claim 10, wherein the catheter is coupled to an imaging modality.
20. A system for performing optical imaging through a catheter, comprising: a prism to receive and direct optical radiation through a catheter sheath; a space is between the prism and the catheter sheath to balance aberrations in optical images obtained from a sample; the space is occupied by air or gas with a refractive index of about 1; the catheter sheath includes an inner surface and an outer surface; the inner surface and outer surface include an optical power and a refractive index, wherein the absolute value of the optical power of the inner surface is higher than the outer surface; and the catheter sheath includes a refractive index matched to the refractive index of a medium exterior the outer surface.
Type: Application
Filed: Nov 8, 2010
Publication Date: Jun 9, 2011
Applicant: Volcano Corporation (San Diego, CA)
Inventors: Thomas E. Milner (Austin, TX), Nathaniel J. Kemp (Concord, MA)
Application Number: 12/941,548
International Classification: A61B 1/06 (20060101);