Percutaneous, ultrasound-guided introduction of medical devices

Described are methods and systems and system components useful for percutaneously delivering or retrieving vascular implant devices, such as filters, utilizing intravenous ultrasound (IVUS) imaging alone or in combination with external (e.g. transabdominal) ultrasound or other imaging technology. Implants deliverable by such systems, such as vena cava or other vascular filters, can have two or more echogenic markers spaced at such a distance that they are separately discernible by IVUS and/or external ultrasound imaging.

BACKGROUND

The present invention pertains generally to medical devices and systems for their introduction. In certain aspects, the invention relates to systems and methods for percutaneously introducing vascular devices such as vascular filters under ultrasound guidance, and to delivery components and implant features that are useful therein.

Vascular devices are commonly percutaneously introduced under fluoroscopic guidance. For example, vena cava filters are most often placed under fluoroscopic guidance with the injection of contrast agent to provide a cavogram characterizing the site of intended implantation. Such fluoroscopic procedures must be performed in a specially equipped room such as an X-ray suite. This not only necessitates transport of an often critically ill patient to the suite but also adds significant expense to the procedure.

Ultrasound imaging technology, including intravenous ultrasound (IVUS) imaging, has been used to some extent in the diagnosis and in the treatment of patients. However, the images generated with IVUS and other ultrasound technology are often more difficult to interpret for purposes of implant guidance, particularly for physicians or other health care providers who are more accustomed to fluoroscopic images.

Needs exists for improved and/or alternative methods, systems and device features whereby the introduction of vascular devices such as vena cava filters can be guided under ultrasound imaging techniques. In certain of its aspects, the present invention is addressed to these needs.

SUMMARY

In some embodiments, the present invention relates to methods and systems for percutaneously delivering or retrieving vascular implant devices, such as filters, utilizing intravenous ultrasound (IVUS) imaging alone or in combination with external (e.g. transabdominal) ultrasound imaging technology. Delivery systems of the invention can include distally-positioned echogenic markers and proximally-positioned visible indicia which together provide enhanced guidance during implant introduction. Implants deliverable by such systems, such as vena cava or other vascular filters, can have two or more echogenic markers spaced at such a distance that they are separately discernible by IVUS and/or external ultrasound imaging. Additional embodiments include IVUS-enabled catheters, IVUS-enabled sheaths, and IVUS-enabled vascular snares, useful for example in the placement or retrieval of vena cava filters, and IVUS-facilitated confirmation of device placement following deployment and systems therefor.

Ultrasound-guiding systems and methods described herein can utilize a combination of IVUS and external (e.g. transabdonimal) ultrasound images, real-time-generated images and stored images (e.g. three-dimensional maps) generated using IVUS imaging, and/or a combination of IVUS images and displayed graphical markers generated by non-imaging techniques. Still further aspects of the invention, and features and advantages thereof, will be apparent to those of ordinary skill in the art from the description herein.

DETAILED DESCRIPTION

As disclosed above, certain aspects of the invention relate to methods and systems that include features which enhance functionality and/or safety during delivery of the vascular devices using ulstrasound imaging techniques. Additionally, aspects of the invention relate to vascular devices, and in particular embodiments vascular filters, including two or more echogenic markers located thereon, as well as percutaneous delivery or retrieval devices that include unique echogenic features and/or IVUS imaging capability.

With reference now toFIG. 1, shown is a vascular filter20in an expanded state. Vascular filter20as depicted is suitable for use as a vena cava filter in humans. Filter20includes a hub21having a plurality of primary struts22and plurality of secondary struts23emanating therefrom. In particular, in the depicted embodiment, filter20includes four primary struts21and eight secondary struts23extending from hub21. Hub21crimps together ends of struts22and23in a compact bundle extending generally along a central or longitudinal axis of filter20. The struts22and23can be formed of a superelastic metal alloy, such as a superelastic nickel-titanium (Ni—Ti) alloy (e.g. Nitinol), stainless steel, or any other suitable material that will result in a self-expanding filter. The struts of filter20can provide a filter structure configured to trap embolic matter in the vascular vessel. Other filters of the invention can include alternate strut configurations or other member(s) positionable within the vessel to trap embolic matter.

Filter20also includes a retrieval/delivery element including a generally straight elongate neck24connected to a reversely-turned hook25, with the hook terminating in ball component26. This retrieval/delivery feature can be used in retrieving and/or initially placing the filter20. Although neck24as illustrated is generally straight, it will be understood that other neck configurations, including curved configurations, can be used. Hub21includes a shoulder27or other feature, preferably extending around its entire circumference, that serves as an echogenic marker and thus generates an ultrasound image discernable from surrounding media or device components. In addition, ball component26effectively serves as such an echogenic marker.

In the illustrated device, shoulder27and ball26, or other echogenic features in their place, are longitudinally spaced a distance “d” from one another sufficient to enable separate and discrete visualization of ball/marker26and shoulder/marker27by IVUS imaging, external ultrasound imaging, or both. In particular embodiments, when using IVUS imaging, distance “d” is sufficiently great that the IVUS probe for generating the IVUS image can be positioned within longitudinal distance “d” without picking up either ball/marker26or shoulder/marker27in the image. In this manner, the IVUS probe and other device components adjacent thereto (e.g. the tip of a snare catheter) can be reliably and recognizably positioned within longitudinal distance “d” by advancing or withdrawing the IVUS probe to separately view ball/marker26and shoulder/marker27, and then positioning the IVUS probe therebetween to a point where neither marker is visible in the IVUS image. The attending physician or other user can thereby develop confidence that the IVUS probe and device components nearby are properly positioned for action within the span of longitudinal distance “d”. Illustratively, as discussed in greater detail below, a retrieval snare having an IVUS probe at or near its distal tip can be reliably positioned within longitudinal distance “d” for closure of a snare loop to capture the retrieval element of filter20. In addition or alternatively, distance “d” can be sufficiently large that marker26and marker27generate separate and discrete images using external (e.g. transabdominal) imaging techniques. External imaging can then be used to view the positioning of third echogenic marker, for example on another device such as the end of a snare, between marker26and27, for action within the span of distance “d”. In certain embodiments, distance “d” is greater than 3 mm, for example in the range of 4 mm to 10 mm.

Filter20may also have echogenic markers positioned on one or a plurality of its primary and/or secondary struts. These echogenic markers can for example be echogenic elements mounted around the struts, including for example sonically-reflective metal coils discernable by IVUS or external ultrasound (US) imaging, or cannular segments with dimpled, grooved or otherwise textured surfaces, or any other suitable echogenic structure. In the illustrated device, echogenic coils28are mounted around the primary struts22. Further, echogenic markers28can include projecting filaments such as whiskers or barbs29, which can serve to enhance interaction of the struts with the vessel walls, for example providing improved anchorage and/or resistance to strut migration through the vessel walls.

Referring now toFIGS. 1A and 1B, shown are a partial cutaway views of additional embodiment of filters20A and20B of the invention, respectively. Except where described otherwise, filters20A and20B can have features that are the same as those of filter20. In filter20A, a delivery/retrieval element is provided that includes a shoulder27A on the hub as in filter20, and a generally straight neck portion24A connected to a terminating, larger-diameter ball component25A. Ball component25A is of sufficient dimension to serve as a graspable feature utilizing a vascular snare. Ball component25A also serves as an echogenic marker for the filter20A. In filter20B (FIG. 1B), a delivery/retrieval element is provided that includes a shoulder27B on the hub as in filter20, and a generally straight neck portion24B connected to a terminating closed hoop25B. Hoop25B defines an internal opening and is of sufficient dimension to serve as a graspable feature, for example utilizing a retrieval hook device. Hoop component25B also includes at least one echogenic marker thereon and in certain embodiments a plurality of echogenic markers (25B′,25B″,25B′″) which may for example be any echogenic structure, component or material described herein, attached to or integrally occurring within or upon the material of hoop25B.

WhileFIGS. 1, 1A and 1Billustrate specific retrieval elements for incorporation within the structure of the vascular filter, it will be understood that other retrieval structures or materials can also be used within aspects of the invention. For example, any attachment structure that can be engaged by mechanical elements and/or using field forces (e.g. magnetic), or by other means, can be used. In certain embodiments, as in the illustrated filters, the retrieval element of the filter can be configured to reside generally centrally in the vessel lumen when the filter is deployed.

With reference toFIG. 2, shown is a partial cutaway view of a system useful for implanting a vascular device such as a filter. System40includes a dilator41for percutaneous introduction, a guide device42such as a wire guide, and an outer delivery sheath43. Dilator41includes an IVUS probe44including one or more ultrasound transducers, such as piezoelectric crystal elements, for producing and/or receiving ultrasonic sound waves. IVUS probe44is preferably a transducer array with a plurality of ultrasound transducers, but can also be provided by a single rotating transducer as known. IVUS probe44and other IVUS elements disclosed herein can, for example, be configured to provide data for two-dimensional and/or three-dimensional IVUS images. IVUS probe44is connected electronically, such as by a wire and connector (not shown) positioned within or along dilator41, to an IVUS imaging system that may include a display device and a computer processor for processing data gathered by IVUS probe44and displaying images correlated thereto. Sheath43of system40includes a distal tip region having an echogenic marker45and a fluoroscopic marker46. Echogenic marker45and fluoroscopic marker46can be provided by the same physical structure or by differing physical structures.

In one embodiment, the markers45/46are both provided by a radiopaque material, such as platinum, titanium, tungsten or another a metal (including alloys), positioned outside and/or within the material making up the body of the sheath43. Illustratively, a platinum structure, such as a platinum hoop or ring, can be attached around the outside of sheath43to provide a fluoroscopically-discernible marker. Such a radiopaque structure can also contain structural features rendering it effective as an echogenic marker. These features may for example include dimples, grooves, or other textured surface features rendering the marker material visually discernible by ultrasound imaging. The fluoroscopic and/or echogenic markers can also be provided by other structures or materials or combinations thereof. Illustratively, in one embodiment, the markers45and46can be located closely adjacent one another, with the fluoroscopic marker46provided by a radiopaque material such as a metal, and the echogenic marker45provided by a separate element with any of the patterned features as discussed hereinabove for echogenic markers, or containing internal materials or features that have an acoustic impedance that significantly differs from the surrounding media so as to be discernible by ultrasonic imaging. The incorporated features or materials can include for example gas-filled spaces embedded within polymeric materials (e.g. bubbles), or acoustic impedance-mismatched, sonically-reflective materials such as glass, ceramic, metal or other particles (e.g. beads) incorporated within or coated upon a polymeric material. For additional information about echogenic markers that can be used herein, reference can be made for example to U.S. Pat. No. 5,201,314.

The markers45/46can be associated with sheath43in any suitable fashion including positioning on the outside, inside, within the body or wall of the sheath43, or combinations thereof. Sheath43also includes a more proximally located marking feature47that is visible to the eye of the user when positioned externally of the patient. Visible marking feature47in the illustrated embodiment demarks the distance from locations within feature47to the distal tip of the sheath43. For these purposes, the marking feature47can include a plurality of visible marking features48spaced longitudinally from one another along the length of sheath43, such as lines, scores, or other markings partially or completely circumscribing the circumference of the sheath43. In the illustrated embodiment, the marking feature47also includes numeric markings49associated with markings48which numerically indicate the distance of the respective associated markings48from the tip of the sheath43. In one example, the marking feature47includes markings48offset longitudinally from one another by a regular distance such as 1 mm or 1 cm, and associated numerical markings49providing an indication of how many millimeters or centimeters, respectively, each marking48is spaced from the distal tip of the sheath43. The marking feature47is positioned along the length of the sheath43such that at least some of or the entire marking feature47will occur externally of the patient during use of the sheath43to deliver the filter or other vascular device. For these purposes, the marking feature47can for example be positioned so as to include markings at skin level at a percutaneous insertion site through which system40is introduced. In this regard, it will be understood that other reference points external of the patient against which the marking feature47can be reliably tracked during a procedure to determine the distance to the distal tip of the sheath may also be used. Fixed external reference points are particularly useful for these purposes.

In one mode of use, the IVUS-enabled dilator41can be advanced within a vascular vessel of the patient along guide42, and the IVUS probe44can be operated to generate signals translated to images of features of the vessel. IVUS probe44can then be positioned to and image a target position to which it is desired to move the distal tip of the sheath43. Thereupon, the sheath43can be advanced coaxially along the dilator41until the distal tip of the sheath43detectably abuts or overlies IVUS probe44or regions proximate thereto. This detection can, for example, be by way of a tactile resistance to advancement of the sheath43over the IVUS probe44or some region or feature of sheath43proximate thereto, or by a change in an ultrasound image generated based signals from IVUS probe44due to the distal tip of the sheath43overlying some or all of IVUS probe44(for example, a change in the brightness of the image). This change in the image, in certain embodiments, can be enhanced by the presence of the echogenic marker45at the distal end region of sheath43. At this point, the user knows that the distal tip of the sheath43is in essentially the same target position as the IVUS probe44. Thereafter, the dilator41and guide42can be withdrawn from sheath43, and a delivery catheter or other delivery instrument for delivering the vascular device can be advanced through sheath43, while continuing to hold stable the position of the sheath43with its distal tip at the target position. In certain embodiments, the distal tip of the vascular implant to be deployed can then be aligned with the distal tip of the sheath43while maintaining the stable position of the sheath43, and sheath43can be withdrawn proximally a distance while holding stable the position of the delivery instrument to reliably deploy the vascular device at the target site.

The alignment of the distal end of the vascular implant with the distal end of the sheath43can be accomplished in any suitable manner, including by tracking the position of the distal tip of the vascular implant ultrasonically (e.g. transabdominally with the assistance of a tip-located echogenic markers, such as marker26on filter20and marker45on sheath43) and/or through other means. In certain embodiments, the vascular device is carried by a delivery catheter or other instrument having a first visible marker that remains external of the patient and which aligns with an external reference point, such as the proximal end of the sheath43or a connected accessory (e.g. a Touhy-Borst adaptor), when the distal end of the vascular implant is at the distal tip of the sheath43. The delivery instrument may also include a second visible marker, proximal to the first visible marker, to which the sheath can be withdrawn, to signal a stage of deployment, e.g. when the vascular implant has been completely deployed out of the sheath. Other measures for accomplishing similar signaling alignments may also be used.

The use of system40ofFIG. 2to deliver a vena cava filter to a patient will now be described with reference toFIGS. 3-7.FIG. 3shows system40having been introduced into the vena cava50through a percutaneous access site51in the right femoral vein of a patient. Right renal vein52A and left renal vein52B feed into the vena cava50, and in the illustrated embodiment it is desired to deploy a filter generally below the renal veins52A and52B, or “caudal” thereto. Depicted inFIG. 3is dilator41advanced into vena cava50and at a position at which IVUS probe44can generate an image of at least the lowest-positioned renal vein, in most instances that being the right renal vein52A. Prior to reaching this position, the IVUS probe44can be used to generate images of vascular landmarks distal to the renal veins, for example the right atrium, the hepatic veins, or other features. In certain embodiments the IVUS probe44will have a longitudinal resolution such that an image showing both renal veins52A and52B can be obtained. Sheath43is also percutaneously inserted into the vena cava, which insertion may have been before, with, or after that of dilator41. The distal tip of sheath43is shown positioned well below the IVUS probe44so that it does not obscure IVUS probe44and thereby degrade generated image data. As can also be seen, the marking feature47includes at least portions remaining at skin level on the patient, and demarking the shaft distance from skin level to the distal tip of sheath43. Further, in the illustrated embodiment, a repositionable scale marker54is positioned about sheath43and can be advanced to locations within marker feature47. Scale marker54can include a stop or locking mechanism55which can be actuated to selectively release and secure the position of scale marker54along sheath43. Any suitable mechanism can be used for this purpose including, for example, spring actuated friction stops against the sheath43, tightenable screws or knobs which abut sheath43or cinch marker54, or the like.

Referring toFIG. 17, the marker54can comprise a spring collar54A, which itself represents another aspect of the invention, receivable around the sheath43(see illustrativeFIG. 3B; it will be understood that spring collar54A can also be used as marker54in other FIGs. in which marker54is shown). Spring collar54A includes a wire spring120with a wire coiled to provide one or more wire loops and preferably a plurality of wire loops121, which can be positioned adjacent to one another. Spring collar54A can also include a first wire segment122extending from the wire loop(s)121and a second wire segment123extending from the wire loop(s)121. In a relaxed (unstressed) condition, the segments122and123extend in directions that are radially offset from one another about a central axis “A” of the wire loop(s)121, preferably at an offset of less than about 140 degrees about central axis “A”. The spring collar54A is configured such that the segments122and123can be moved radially toward one another, for example by squeezing them toward one another, to cause the internal diameter of the wire loop(s)121to increase in size in the resulting stressed condition of the spring collar54A. In this fashion, spring collar54A can be received around sheath43or another elongate, percutaneously introduced device, and can be sized to frictionally engage the outer surface of the sheath43or other device when in its relaxed condition or at least biasing toward its relaxed condition, and then frictionally disengage (or at least engage with less friction) when segments122and123are moved toward one another to increase the loop(s) diameter. This action can be used to facilitate repositioning the spring collar54A along the sheath43or other device by disengaging, moving and then re-engaging the spring collar54A. Other actions that reduce the diameter of loop(s)121may also be used, including for instance an action in which moving segments122and123toward one another causes such diameter to decrease while introducing stress into the spring collar. In such a design, for frictional engagement with the sheath43or other device, a feature for holding the segments122and123in position once the sheath/device is stressed and thereby engaged could be used, for example a clip or cap. The clip, cap or other feature could thereafter be removed or released to disengage the spring collar from the sheath43/device, move the spring collar, and then re-applied after squeezing segments122and123toward one another to re-engage the sheath/device.

As illustrated inFIG. 17, the spring collar54A can optionally include a molded plastic or other jacket attached to and that at least partially covers the wire spring120. Such a jacket can be provided by one piece or optionally multiple pieces, and desirably includes at least tab portions connected respectively to each of the wire segments122and123, with the tab portions providing a widened (relative to the diameters of the wire segments122and123) area that can be used for manually gripping and manipulating the spring collar54A for the engagement/disengagement operations discussed above. In the illustrated embodiment, the jacket includes a first jacket piece124and a second jacket piece125. First and second jacket pieces124,125include respective tab portions126,127which define respective grooves128,129for receiving respective portions of wire segments122,123. Grooves128and129terminate along the lengths of tab portions126and127, and tab portions126and127include portions130and131outward of the grooves128and129which define respective apertures132and133for receiving outward end portions of the wire segments122and123. If desired, a bonding agent can be applied within apertures132and133or at other locations to help to secure the jacket pieces124and125to the wire spring120. Jacket pieces124and125can also include structures for jacketing the wire loop(s)121of the wire spring120. With reference to first jacket piece124, it includes a loop-covering portion134that includes one or more fingers135, preferably two or more fingers. Second jacket piece125includes a loop covering portion136that includes one or more fingers137, preferably two or more fingers. When jacket pieces124and125are assembled on the wire spring, finger(s)135and finger(s)137interleave but remain slidably disposed with respect to one another. In this fashion, when tab portions126and127are squeezed or otherwise forced toward one another to enlarge the loop(s)121, finger(s)135and137will slide relative to one another so as to decrease their extent of interleaved overlap while still providing a structure that generally surrounds the loop(s)121. Release of the tab portions126and127will then cause finger(s)135and137to slide again relative to one another so as to increase their extent of interleaved overlap while providing a loop(s)-surrounding structure. Jacket portions124and125can optionally each be monolithic pieces, as illustrated, providing both the respective tab portions and loop(s)-surrounding portions.

When the spring collar54A or other scale marker54is frictionally engaged with the sheath43or other device, it can do so while compressing the sheath43or other device at a level which does not substantially deform the shape of the sheath43or other device (e.g. leaving open an internal lumen thereof) but which creates sufficient friction to resist movement of the collar54A or other marker54along the sheath43or other device during use. For example, such friction can be sufficient to require a force of greater than 2 Newtons applied to the engaged collar54A/marker54in the direction of the longitudinal axis of the sheath43or other device in order to cause sliding movement of the engaged collar54A/marker54, more preferably in the range of about 3 Newtons to 10 Newtons, and most preferably about 4 to about 5 Newtons. It will be understood that other force values could be utilized in varied circumstances depending for instance upon the particular percutaneously-introduced device and procedure requirements associated therewith. It will also be understood that the friction and resultant resistance to linear displacement of the engaged spring collar54A or other marker54can depend, for instance, upon the extent of surface contact, the surface characteristics and materials of construction of the collar or marker and those of the sheath or other percutaneous device, which can also be varied in achieving the desired result. The variation of these and other parameters will be within the purview of those skilled in the field given the teachings herein. Moreover, as shown inFIG. 3C, in accordance with certain inventive embodiments, a spring collar54A or other biased marker54can be equipped with a retainer device54B that holds the collar54A or other marker54in an unrelaxed (or stressed) condition when received around the sheath43or other device. For example, the sheath or other device can be packaged or handled with the collar54A or other marker54received therearound, but equipped with the applied retainer device54B to disengage or reduce compression of the sheath43or other device by the collar54A or other marker54. In this fashion, potential deformation of the sheath43or other device over time, e.g. during storage prior to use, can be reduced or eliminated. As illustrated, retainer device54B can be a cap in which tab portions126and127are received and held closer together than they would be in a relaxed condition of the collar54A, although other retainer elements or devices that resist return of the spring collar54A to its relaxed condition could also be used.

Returning to a discussion of an illustrative procedure, with particular reference toFIG. 4, while holding the position of IVUS probe44stationary, sheath43is advanced coaxially over dilator41until the distal tip of sheath43advances over IVUS probe44. This event can be sensed tactilely as discussed above, and/or through a change in the image generated by IVUS probe44due to being covered by the wall of sheath43(potentially enhanced by the presence of echogenic marker46, which can be configured to reflect ultrasonic energy sourced from the probe44within). At this point, the user knows that the distal tip of sheath43is positioned at the target position found with the IVUS probe44. The user can then reference the scale markings within the marking feature47that coincide with the skin level of the percutaneous insertion site51. A correlation can thereby be drawn between the positioning of the distal tip of the sheath43at the target site and a scale marking within marking feature47. Again, in one embodiment, such scale marking includes a numeric value correlating to the distance from the marking to the distal tip of sheath43. The repositionable scale marker54, when present, can also be advanced and secured to abut the percutaneous insertion site51with the distal tip of sheath43at this target position. The dilator41and if still present the wire guide can then be removed from the sheath43while holding the sheath stably in position with the distal tip of the sheath43at the target position.

Referring now toFIGS. 5 and 6, thereafter, a filter introducer system carrying filter20(FIG. 1) is advanced into the sheath43. InFIG. 5, shown is filter introducer system60advanced into sheath43to position the distal tip of filter20substantially at the distal tip of sheath43. As noted above, this positioning can be discerned in any suitable manner. In the embodiment shown, filter introducer60includes proximal, visible markers62and63spaced longitudinally from one another, and positioned on introducer60so as to remain external of the patient during the procedure. When the distal-most marker62aligns with a distal-most portion of the sheath43, or aligns with another identifiable reference associated with sheath43, the distal tip of filter20is aligned with the distal tip of sheath43.

With reference now toFIGS. 5 and 6together, at this point, sheath43can be withdrawn until the proximal end of sheath43(or the associated reference point) is flush with marker63, whereupon filter20is externalized from sheath43at the target location. In the illustrated embodiment, at this stage, the secondary legs23of filter20are deployed outwardly against the wall of the inferior vena cava50; however, the primary struts22remain engaged by retaining element61, such as a metal mount, located at the tip of introducer60. Retaining device61is actuatable from a position external of the patient to release primary struts22of filter20, for example by operating a button, switch, lever, or any other suitable mechanism. Such a mechanism is in use at present on the COOK® CLECT® filter set for femoral vein approach (William Cook Europe, Denmark), which mechanism can be used herein. Additionally, reference can be made to U.S. Pat. No. 5,324,304, which describes similar release mechanisms that can be used herein.

After release of the primary struts22from the retaining element61, filter20fully deploys in vena cava50, and sheath43and any other percutaneously introduced devices can thereafter be withdrawn from the patient. Shown inFIG. 7is an enlarged view of filter20as deployed within the inferior vena cava50, with both secondary struts23and primary struts22having expanded radially outwardly against the wall of vena cava50. With filter device20so deployed, in certain embodiments the echogenic markers26and27are sufficiently spaced to be viewed by transabdominal ultrasound as distinct images. Still further, in desirable embodiments, echogenic markers28are located on primary struts22so as to be positioned against the caval or other vessel wall when in the expanded, deployed condition. The position of echogenic markers28and thus of the associated strut regions can thus be confirmed with ultrasound images. As noted above, the elongate generally straight filaments29extending from markers28can aid in the fixation of device20against the walls of vena cava50and/or can help to prevent migration of the struts22through the caval or other vessel wall.

In advantageous operations, after deployment of the filter20from sheath43and release of the primary struts22from retaining device61, the filter introducer60is withdrawn while leaving sheath43percutaneously inserted. The guide42can then be reinserted through sheath43and an IVUS-enabled catheter such as dilator41can be reintroduced over the guide42. With the guide42extending into or beyond the filter20, the IVUS-enabled dilator41can be advanced within vena cava50and the IVUS probe44can be used in the generation of images to confirm the deployment position of filter20. In one mode, the IVUS images generated can be used to inspect the position of the primary struts22and/or secondary struts23against the wall of vena cava50. To facilitate this inspection, echogenic markers (e.g.28) positioned on struts22and/or23and configured to be opposed against the wall of vena cava50upon proper deployment of the filter20can be used to generate images from which such apposition can be confirmed or denied. The IVUS probe44can also if desired be advanced beyond filter20to generate an image of renal vein or veins52A and/or52B to confirm position of the filter20caudal thereto. After this inspection, and potentially also electronic storage of the confirming images for the patient record, the guide device42and IVUS-enabled dilator41can be withdrawn from the patient. For example, shown inFIG. 16are images of a vena cava filter implanted in the vena cava of a sheep, obtained by advancing an IVUS-enabled catheter beyond the implanted filter and generating IVUS images during a pull-back of the catheter. Shown at the top is a projection image generated from a series of axial images, depicting the lower renal junction, the vena cava filter hook, the filter legs, and the ilio-caval bifurcation. The projection image has interpretive markings added by the user, in the form of color-coded vertical lines corresponding to anatomical landmarks and features of the implanted device. Desirably, the projection image or other IVUS-generated image(s) will depict the first and second ends of the device, which can optionally be marked on the image by the user. Shown at the bottom are axial IVUS images corresponding to the device features and anatomic landmarks discussed above and depicted in the projection image, and color coded to the vertical lines added to the projection image. These and other marking and/or indexing measures can be taken to add clarity to the interpretation of the image(s). Such an image or images can be obtained of an implanted vena cava filter or other vascular filter or other device, with accompanying physiologic landmarks from the patient, to confirm proper placement of the device following deployment. The optional presence of echogenic features on the device, e.g. on the filter hook and/or filter legs, can enhance the ability to visualize the device features in the confirming ultrasound images. The utilization of IVUS-generated device placement images to confirm the location of the implanted device after deployment, and for purposes of maintaining a patient medical record relating to the surgery, constitutes another embodiment of the invention and can be used in conjunction with any system or placement method described herein or otherwise. The collected IVUS data can be filtered to improve the IVUS image, for example by excluding data from certain segments or regions. For example, the projection image inFIG. 16(top) was generated from data taken from the longitudinal volume depicted between the dotted lines in the left-most axial image found below. This technique and/or other filtering techniques can be used to improve the image quality given the teachings herein. The IVUS-generated images can be electronically stored in the patient record, e.g. using a data capture and storage system directly coupled to the IVUS device or system, or by otherwise transferring the electronic data to the patient record, and/or by retaining printouts or other “hard copy” version of the captured confirming images. In certain embodiments, the IVUS-generated image can serve as an alternative to any radiographic image (e.g. X-ray image) where no radiographic confirmation of placement is taken, and in other embodiments the IVUS-generated image can serve as an addition to a placement-confirming X-ray or other radiographic image in the patient record.

FIGS. 7-9illustrate an embodiment of a delivery system for a vascular device, such as a vascular filter, that is useful from an approach descending downwardly within the vena cava, e.g. through a percutaneous access site in the left or right jugular vein. System70has numerous features which correspond directly with features of system40discussed above, to which reference can be made for details. System70includes an IVUS-enabled dilator having an IVUS probe78, for percutaneous insertion through percutaneous access site71. System70includes a sheath72translatable coaxially over the dilator. An echogenic marker73is provided at the distal end of sheath72. Sheath72further includes an echogenic marker74spaced proximally of marker73a longitudinal distance75. Markers73and74can optionally include physically discrete or physically integrated fluoroscopic markers as discussed above. Longitudinal distance75corresponds to a desired distance for advancement of the distal tip of sheath72beyond IVUS probe78to position the sheath for deployment of a vascular device, as discussed in further detail below. Sheath72also includes a marking feature76corresponding to marking feature47of sheath43, desirably a numeric distance scale, as discussed above. It will be understood in this regard that the relative position of marking feature76along sheath72may differ from the position of marking feature47along sheath43, due to the differing distances from the respective percutaneous entry sites the target site. System70also includes a guide device79such as a wire guide. Shown inFIG. 7is the dilator with the IVUS probe78in position to image and identify a location at or just below the renal veins52A and52B which feed into inferior vena cava50. This position is intended to be at or near the uppermost portion of the vascular implant when deployed. Sheath72is shown inFIG. 7in position with its distal tip proximal of IVUS probe78for best viewing conditions.

Referring now particularly toFIG. 8, while holding the IVUS probe78in the target position, sheath72has been advanced along the dilator. In doing so, the advancement of the distal sheath tip over the IVUS probe78is recognizable by the user by a change in the generated IVUS image, which can be enhanced through the presence of an echogenic marker73. As the sheath72is advanced further, the user will again note a change in the IVUS image as the more proximal echogenic marker74arrives overtop the IVUS probe78. If desired, sheath72can be configured to also provide a tactile signal of this positioning. In this position, the distal tip of the sheath72has been advanced to a target location distal of the IVUS probe78from which pull-back of sheath72will be initiated for deployment of the implant. At this point also, the user can make visual reference to the visible marker feature76and in a particular embodiment to scale markings therein which align at skin level at the percutaneous entry site71, or with any other suitable location correlating to the position of the distal tip of the sheath72. While holding the sheath in position, potentially with continuing reference to the position of scale markings within the marking feature76, the dilator including IVUS probe78and the guide79can then be withdrawn.

With reference now toFIG. 9, a filter introducer80carrying filter20can then be inserted through sheath72. Filter20can for example be held by introducer80with a loop, hook or similar retaining device84located at the distal end of introducer80and engaging the hook of filter device20. Similar to system40above, filter introducer80includes proximally-positioned external visible markers82and83spaced longitudinally along the shaft of device80. The distal marker82aligns generally with a reference point, for instance the proximal end of sheath72or an element connected thereto, when the distal end of filter20is generally aligned with the distal tip of sheath72. After advancing filter introducer80to this position while holding sheath72in place, sheath72can be withdrawn proximally until the distal end of sheath72(or piece associated therewith) is generally flush with marker83, giving indication that the filter device20has been deployed from the distal opening of sheath72. Retaining device84can then be actuated to release filter device20from introducer80, thus leaving filter device20deployed within the inferior vena cava. Thereafter, if desired, the guide device79and the IVUS-enabled dilator can be re-introduced through sheath72and used to inspect the deployed filter20and the apposition of its struts against the caval wall. Echogenic markers28positioned on the primary struts22and/or the secondary struts23can facilitate capturing images showing those markers at or against the wall of vessel50to provide assurance that the filter20has properly and completely deployed. The guide79, the dilator with IVUS probe78and if still present the sheath72can then be withdrawn from the patient.

In additional aspects of the invention, provided are IVUS-enabled and/or echogenically-marked percutaneously-insertable devices that can be used in the retrieval or delivery of vascular filters or other implant devices.FIG. 11is a partial cut-away view of a percutaneous vascular snare device90embodiment of the invention. Vascular snare90includes an elongate shaft91having an internal lumen and a snare loop92, for example made of a flexible filament(s) such as wire, which can be controllably deployed from and withdrawn into the lumen. Snare device90includes an echogenic marker92on at least a portion of the snare loop92. Echogenic marker92can include a grooved structure, a coil such as a wire coil, a dimpled and/or grooved structure such as dimpled and/or grooved cannula, or any other suitable echogenic structure or material as discussed herein. Further, marker92can be mounted over the wire or other elongate filament forming the snare loop92, or can be integrally formed into the wire or other elongate filament. Echogenic marker92is sized and configured to permit the deployment of the snare loop92smoothly out of and into the cannulated device91without substantial damage to either, so as to facilitate capturing devices with the snare. In certain embodiments, the snare device90includes an IVUS probe94. The IVUS probe94can be used in obtaining ultrasound-generated images of a device to be captured and potentially retrieved with snare device90. Still further, in some embodiments, the echogenic marker93of snare device90can be positioned on the snare loop92, and the snare loop can deploy to a configuration, such that at least a portion of the marker93can be imaged using an ultrasonic signal generated with the IVUS probe94. For these purposes, the snare loop92can deploy, at least in part, laterally from the lumen of the cannulated device91, so as to position at least a portion of the echogenic marker93, and potentially the entire marker92, within the range of longitudinal resolution of the IVUS probe94. In this manner, a user of snare device90can confirm deployment and position of the snare loop92in an open position by viewing images generated with IVUS probe94. For these purposes, the snare loop92can be deploy to an open condition in which at least a portion of echogenic marker93aligns longitudinally with at least a portion of IVUS probe94, or is longitudinally offset no more than about 3 mm therefrom. Echogenic marker93can, of course, also be visualized using an externally-generated (e.g. transabdominal) ultrasound image, to assist in guiding a capture or retrieval operation. Such external ultrasound imaging can also be used in conjunction with IVUS imaging derived from IVUS probe94in guiding the operation.

With continued reference toFIG. 11and also toFIG. 12, in one mode, vascular snare90can be used to capture and retrieve an implanted vascular filter, for instance filter20described herein. External (e.g. transabdominal) ultrasound imaging can be used to discretely visualize echogenic markers26and27of filter20and echogenic marker93of snare device20(in an open condition) positioned therebetween and around neck25of filter20. Snare loop92can then be closed by withdrawing it into the cannulated shaft91so as to capture filter20, with the closed snare loop ultimately catching in hook25. Alternatively or in addition, when IVUS probe94is present, vascular snare90can be used in generating an IVUS image to discretely and sequentially visualize marker27and marker26of filter20, to guide positioning of the snare loop therebetween and around the neck25of the filter20, whereupon it can be closed to capture the filter20. After capture of the filter in the snare loop92in a closed condition, a cannulated retrieval device95(FIG. 12) such as a catheter or sheath can be advanced over device91and over filter20to force struts23and22radially inwardly to retrieve the filter20into the cannulated retrieval device95. The snare90, filter20and cannulated retrieval device95can then be removed from the patient. Alternatively, such a capture and/or retrieval operation can be used to reposition the filter20after deployment.

FIG. 13illustrates another embodiment of an IVUS-enabled filter delivery system100of the invention. System100includes a filter delivery sheath101with filter20housed in a lumen thereof. Delivery sheath101can have all of the attributes of sheath43discussed hereinabove, including but not limited to marking feature47and repositionable scale marker54(see, e.g.,FIGS. 2-6). Delivery sheath101also has an IVUS probe102mounted proximate its distal tip. As discussed above, wire(s) and connectors for powering IVUS transducer element102and for transmitting signal data can be suitably routed along sheath101embedded within shaft walls, within additional lumens thereof, or properly positioned and protected, may share a lumen with filter20. Any of these same arrangements or combinations thereof can be used for routing wire(s) and connectors for any of the IVUS probes disclosed herein. The presence of IVUS probe102on the implant delivery sheath101itself can eliminate the need to use a separate IVUS-enabled device (e.g., the IVUS-enabled dilator41discussed above), although in certain modes of use both types of IVUS-enabled devices could be used in guiding the device delivery.

Delivery sheath101also includes an echogenic marker103and/or a fluoroscopic marker104. As discussed above, markers103and104, when both present, can be provided by a single structure or material with dual function, or by separate pieces or structures. The arrangements discussed above can be suitably used. IVUS-enabled filter delivery system100also includes a filter introducer device105, such as a catheter, having an elongate shaft106and a retaining element107, such as a metal mount, in which the ends of primary struts22of filter20are received, and are releasably held. The ends of primary struts22can be released from retaining element107upon actuation of a button, switch or other suitable mechanism of introducer device105, as discussed above for other embodiments.

Delivery sheath101can be used to percutaneously deliver vena cava filter20to a position generally as shown inFIGS. 3-6, with modification. To do so, sheath101can be percutaneously introduced (conventionally along with a dilator, which is then removed), e.g. through the right or left femoral vein, and advanced to a position to view the renal veins using the IVUS probe102. With the position of the probe102generally at or caudal to the lower renal vein (typically the right), the position of the sheath101can be noted (e.g. using visible scale markings corresponding to feature47above). Holding the sheath101in place, the filter introducer105can be used to advance the hook of filter20to the distal tip of the sheath101, for example using alignment of external, visible proximal marker108on introducer105with a feature on or associated with sheath101to signal that the distal tip of filter20is aligned with the distal tip of sheath101. The position of the distal tip of sheath101within the inferior vena cava can then be confirmed using the external (e.g. skin-level) visible scale markings on the sheath and/or using the IVUS probe102to visualize the renal vein(s) again. The sheath can then be pulled back to align the feature on or associated with sheath101with external, visible marker109to signal that filter20has been deployed from the distal opening of sheath101. The release actuator for retention device107can then be operated to release primary struts22of filter20to fully deploy the filter20.

FIG. 14illustrates still another embodiment of an IVUS-enabled filter delivery system110of the invention. System110includes a filter delivery sheath111with filter20housed in a lumen thereof. Delivery sheath111can have all of the attributes of sheaths discussed hereinabove, including but not limited to external visible marking features (e.g.76,FIGS. 8-10) and a repositionable scale marker (e.g.54,FIGS. 2-6). Delivery sheath111also has an IVUS probe112a distance proximal to its distal tip. The presence of IVUS probe112on the implant delivery sheath111itself can eliminate the need to use a separate IVUS-enabled device (e.g., an IVUS-enabled dilator as discussed above), although in certain modes of use both types of IVUS-enabled devices could be used in guiding the device delivery.

Delivery sheath111also includes an echogenic marker113and/or a fluoroscopic marker114proximate its distal tip, the construction of which can be as discussed hereinabove. System110also includes a filter introducer device115, such as a catheter, having an elongate shaft116and a retaining element117, such as a hook, releasably engaging the hook of filter20. The hook of filter20can be released from retaining element117upon actuation of a button, switch or other suitable mechanism of introducer device115, as discussed above for other embodiments.

Delivery sheath111can be used to percutaneously deliver vena cava filter20to a position generally as shown inFIGS. 8-10, with modification. To do so, sheath111can be percutaneously introduced (conventionally along with a dilator, which is then removed), e.g. through the right or left jugular vein, and advanced to a position to view the renal veins using the IVUS probe112. With the position of the probe112generally at or caudal to the lower renal vein (typically the right), the position of the sheath111can be noted (e.g. using external visible scale markings corresponding to features47or76above). Due to the distance between IVUS probe112and the distal end of sheath, this position will place the distal end of sheath111well caudal the renal vein(s), at a position corresponding to the desired lowermost point of the deployed filter implant. In the illustrated embodiment, the distance from IVUS probe112to the distal sheath tip is approximately equal to or slightly greater than (e.g. up to about 130% of) the length of filter20when deployed. Holding the sheath111in place, the filter introducer115can be used to advance the distal leg ends of filter20to the distal tip of the sheath111, for example using alignment of external, visible proximal marker118with a feature on or associated with sheath111to signal that the distal tip of filter20is aligned with the distal tip of sheath111. The position of the distal tip of sheath111within the inferior vena cava can then be confirmed using the external (e.g. skin-level) visible scale markings on the sheath and/or using the IVUS probe112to again visualize the renal vein(s). The sheath can then be pulled back to align a feature on or associated with sheath111with external, visible marker119to signal that filter20has been deployed from the distal opening of sheath111. The release actuator for retention device117can then be operated to release the hook25of filter20to fully deploy the filter20.

In additional embodiments, unique ultrasound image guidance methods and systems are provided. These methods and systems can be used in conjunction with implant devices and delivery/retrieval components discussed hereinabove, or with other devices or components. In one aspect, ultrasound guidance of percutaneous procedures can be provided using a combination of real time IVUS images and electronically-stored images. The electronically-stored images can, for example, be sequential images of a vessel acquired during pull-back of an IVUS probe (e.g., on IVUS-enabled dilators, sheaths or snares as discussed above) within the vessel, desirably at a constant speed, or generated images reconstructed from a plurality of such sequential images. Constant-speed pull-back devices for these purposes are known and commercially available. The generated, stored images can for example be three-dimensional or two-dimensional images of the length of vessel in which an implant such as a filter is to be deployed, reconstructed from a plurality of sequential, cross-sectional or otherwise segmental images of the vessel.

With reference toFIG. 15, provided is a schematic showing components of one embodiment of such a system. System200as depicted includes IVUS-enabled dilator41as described above (FIGS. 2-4), although other IVUS-enabled devices such as the dilator ofFIGS. 8-9, snare94(FIG. 11) or delivery sheaths101(FIG. 13) or111(FIG. 14) can be substituted for dilator41. Dilator41includes IVUS probe44and also includes a marking feature47A, which can be the same as marking feature47discussed hereinabove in connection withFIGS. 2-6) and thus include individual scale markings48denoting a distance from the marking to a distal feature of dilator41, such as the distance from the individual scale marking to the IVUS probe44, and associated numerical markings49. Dilator is shown percutaneously inserted with scaled regions of marking feature47A occurring at skin level at entry site51on the patient.

System200includes a computer processor201, which can also include an electronic memory storage for storing data and images. Computer processor201receives signal data from IVUS probe44via data transmission connection202, which can for example be a wired or wireless connection. Computer processor201generates ultrasound images of vessel50using the transmitted signal data. Processor201is electronically connected via connection203to a visual display device204such as a display monitor. Display device204displays two-dimensional, real time IVUS images205generated using IVUS probe44. In the depicted image205, shown are the left and right renal veins generated by IVUS probe44positioned closely thereby. Display device204also displays an image206generated by reconstructing a plurality of previously-acquired two-dimensional, cross-sectional image data sets from IVUS probe44. Algorithms for these purposes are known and are also available in commercially available IVUS devices and associated software, including those available from Volcano Corporation (San Diego, Calif., USA). The previously-acquired data sets for reconstructing image206can be obtained during a pull-back of dilator41, desirably at constant speed, during which IVUS image data are collected, desirably at regular time intervals. A pull-back device206A can be used for these purposes, embodiments of which are also commercially available from Volcano Corporation.

In one embodiment, a graphical scale207is displayed on or in conjunction with image206. Scale207can have scale markings208which correlate to individual scale markings48on dilator41. Scale207can also have respective associated numerical markings209which correlate to respective associated numerical markings49on dilator41. Thus, for example, a scaled marker on graphical scale207that is numbered “10 cm” will align longitudinally on or next to image206at a point correlated to the longitudinal position of IVUS probe44when a corresponding “10 cm” scaled marker of marking feature47A occurs at skin level of entry site51. Reliable external reference points for marking feature47A other than skin level could also be used. In one manner of generating and locating graphical scale207, at the starting point for pull-back, a user can input to the processor201the numeric indicia49having associated marker28at skin level. Using time-elapsed and constant-speed information provided to processor201by pull-back device206A via connection206B, processor201can ascertain how far probe44has traveled when generating a given image data set to be incorporated in the reconstruction of image206, and can thereby accurately generate scale207in reference to the reconstructed image206. In other modes of accurately generating scale207, pull-back device206A can include a device for directly measuring the distance traveled by dilator41during the pull-back, for example by detecting revolutions of a roller wheel of known circumference, or any other suitable means, and can communicate traveled distances to processor201that correlate to images acquired. Alternatively, such a direct measuring device can be provided in a separate position-tracking device212which communicates similar information to processor201concerning dilator41shaft travel distance during image acquisition via connection213. As another alternative, during pull-back, a user can manually communicate shaft travel increments to processor201during image capture while watching marking feature47A as it moves past skin level or another reference point. These or other measures for accurately associating scale207with image206can be used.

In certain embodiments, a graphical image210having features generally correlating to those of dilator41or the other device in use is displayed in association with image206, potentially also in combination with scale207. The graphical image210can include a graphical representation211of the IVUS probe44, the distal tip of the device in use, and/or other device features. The position and movement of the image210relative to image206can be correlated to the position of dilator41(or the other device in use) within the vessel50. This can be accomplished by inputting to processor201information related to shaft travel of dilator41during the procedure, starting from a known reference point which may for example be manually inputted by a user based upon visual observation of marking feature47A relative to skin level or another reference point, and/or may be a direct continuation of the above-described positional tracking of the device41during the pull-back/image acquisition phase, for which the original positional input information from the user at the start of pull-back may continue to serve as a known reference point. To track shaft travel, devices for directly measuring shaft travel (e.g. as a part of the pull-back device206A or a separate position-tracking device23), or manual entry by a user, can be used, as discussed above.

In a different mode, sequential images that continue to be acquired by IVUS probe41during the procedure can be compared, using an appropriate algorithm and processor201, to prior-acquired images obtained to generate image206. The newly-acquired images can then be registered to prior-acquired images of known position along image206, and the graphical image210can be positioned accordingly, e.g. by aligning graphical IVUS probe image211with the registered prior-acquired image.

System200can also include an external ultrasound imaging probe214(e.g. a transdominal probe) connected to processor201via transmission connection215. Alternatively or in addition to graphical images207and/or210discussed above, real-time external ultrasound images can be positionally registered to prior-acquired and generated IVUS image206and displayed therein or adjacent thereto, via appropriate fiduciary points established during the generation of IVUS image206, for example by fixing the position of probe214during the procedure and acquiring fiduciary points during the pull-back operation, such as the location of the starting and finishing positions of an externally-imaged echogenic marker (e.g.45,FIG. 2) respectively at the start and end of the pull-back to generate image206. In this manner, historic IVUS data and real time external ultrasound data can be together used to guide a device delivery or retrieval operation. Of course, real-time IVUS data and images can also be used in conjunction with the historic IVUS data and real time external ultrasound data.

The display204can also include patient-specific information216and date/time information217, as well as appropriate image descriptors218and219, or other standard system performance or setting information.

In still further embodiments of the invention, systems and methods as described above which employ an ultrasound-emitting IVUS probe on a percutaneously-introduced device, can be used in conjunction with an external (e.g. transabdominal) ultrasound unit that is tuned to receive an ultrasound signal from the IVUS probe, and thereby detect the location of the IVUS probe as an “active” ultrasound marker in the system, or detect the location of a separate echogenic marker(s) on the introduced IVUS device or neighboring devices based upon the reflection by the separate marker(s) of the internally-generated IVUS signal. In this fashion the relative location of portions of the introduced device(s) can be detected with external ultrasound based on the IVUS-probe-generated, and potentially reflected, ultrasound signal. In addition or alternatively, the internally-generated IVUS probe signal can be received by the external ultrasound unit and processed to develop images of biological structures, thus providing an “inside out” ultrasound image generation system. In some embodiments, the external receipt and processing of the signals from the IVUS probe can be accomplished using an external ultrasound unit also used simultaneously or intermittently to emit and detect reflected ultrasound for development of ultrasound images, as discussed hereinabove. Alternatively, separate external ultrasound units can be used, one tuned to detect the IVUS probe-generated signals, and one functioning to generate images of biological structures and potentially other features of the introduced device from externally-generated ultrasound. In certain modes of practice, images or corresponding signals generated from both ultrasound emitted by the internal IVUS probe and by an external unit can be used together, either displayed as separate images to a user or processed and combined using an algorithm (e.g. with registration) to generate a single, enhanced image for display. Such processing can be achieved using a computer processor as described herein. Systems and methods as here described having images developed using IVUS probe-generated ultrasound that is detected externally, alone or in combination with externally-generated ultrasound, form additional embodiments of the invention whether used with the specific systems described in conjunction with the drawings above, or otherwise.

It will be understood that although embodiments described herein are at times discussed in connection with the delivery of, or features of, a vascular filter and related sheath and/or catheter deployment devices, embodiments of the invention can likewise involve the delivery of, and features of, other percutaneously-deliverable vascular devices such as stents, stent valves, occluders, embolization devices, anastomosis devices, and the like. These and other permutations will be within the purview of those of ordinary skill in the art given the teachings herein.

Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Of course, variations of those preferred embodiments will become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context. In addition, all publications cited herein are indicative of the abilities of those of ordinary skill in the art and are hereby incorporated by reference in their entirety as if individually incorporated by reference and fully set forth.