Patent Description:
A medical device may be enabled with shape sensing by embedding an optical fiber(s) within the device. Optical shape sensing (OSS) or Fiber-Optical RealShape™ (hereinafter, "FORS™") employs light along an optical fiber for device localization and navigation during surgical intervention. One principle involved makes use of distributed strain measurements in the optical fiber using characteristic Rayleigh backscatter or controlled grating patterns. Multiple optical fibers can be used together to reconstruct a 3D shape, or a single optical fiber with multiple cores that may also be helixed for a lower-profile sensor. The shape along the optical fiber begins at a specific point along the sensor, known as the launch or z=<NUM>, and the subsequent shape position and orientation are relative to that point. FORS™ fibers can be integrated into medical devices to provide live guidance of the devices during minimally invasive procedures.

The inclusion of a FORS™ shape sensing device permits the determination of the shape of the device and a virtual visualization without requiring an imaging device such as an x-ray imaging device. However, the shape sensing device requires customizing the mechanical design of the device to add an additional space for the fiber. Adding the fiber also adds cost to the device and necessitates the use of a shape sensing system. Therefore, to determine the shape of each interventional device a fiber may be added to each device and additional shape sensing systems are required. Alternatively, a hub may be used in connection with a single shape sensed device.

Locking devices such as hubs have been used in connection with shape sensed interventional devices to provide a shape or curvature deformation in the device. The shape of a non-shape-sensed device, such as a catheter that is employed over a guidewire having FORS™ shape sensing, will be defined by the shape of the guidewire for the length over which the devices overlap. The locking device may provide a fixed relationship between the FORS™ guidewire and the catheter.

If the shape-sensed device and non-shape-sensed device are attached to a hub, the starting position may be where the non-shape-sensed device locks onto the hub. However, in order to accurately visualize the non-shape-sensed device as a virtual device, the length and rotation of the non-shape-sensed device with respect to the FORS™ guidewire is needed for a registration step. The length of the device provided by the manufacturer is often inaccurate due to manufacturing variances, etc. However, precise measurements of the length are often required to determine a virtual shape of the non-shape-sensed device. It would be advantageous to register a conventional interventional device that does not have a shape sensing fiber and a shape sensed interventional device that are used with a hub to determine the length and angle of the non-shape-sensed device and accurately visualize the device.

Furthermore, the interaction between a shape-sensed guidewire and an interventional instrument, such as a catheter, may be critical for certain applications. Therefore, it would be advantageous to determine the state of the shape-sensed guidewire with respect to the interventional instrument by monitoring the curvature of the guidewire.

<CIT> provides a medical device deployment system includes a main body (<NUM>) and a guidewire (<NUM>) capable of being passed through the main body and including a lumen. An optical shape sensing (OSS) system (<NUM>) is configured to pass through the lumen in the guidewire. The OSS system is configured to measure shape, position or orientation of an endograft (<NUM>) relative to a blood vessel for placement of the endograft.

<CIT> discloses a method for reconstructing 3D shape of a longitudinal device using an optical fiber with optical shape sensing (OSS) properties, e.g. Bragg gratings. By attaching the optical fiber to the longitudinal device, such that the optical fiber follows its 3D shape upon bending, known OSS techniques can be applied to reconstruct 3D shape of the optical fiber, and thus also the longitudinal device, e.g. a medical catheter. the optical fiber, e.g. placed in a guide wire, can be inserted in a lumen of the longitudinal device. Hereby, one OSS system can be used for 3D tracking a plurality of non-shape sensed catheters or other longitudinal devices. In case the longitudinal device is longer than the optical fiber, the position and shape of the remaining part of the longitudinal device may be estimated and visualized to a user, e.g. based on a known length of the longitudinal device, and based on an orientation of an end point of the optical fiber, e.g. using knowledge about the stiffness or other properties of the longitudinal device.

The objects, features and advantages of the present disclosure will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.

This disclosure will present in detail the following description of preferred embodiments with reference to the following figures wherein:.

In accordance with the present principles, a system for determining the length of a non-shape-sensed interventional device is provided. The system is configured to determine the position of the non-shape-sensed interventional device by utilizing a FORS™ guidewire received in the lumen of the device. The FORS™ guidewire and non-shape-sensed interventional device are preferably secured to a hub. A registration module is configured to register a position of the distal tip of the non-shape-sensed interventional to a position of the FORS™ guidewire. A determination module is configured to determine the length of the non-shape-sensed interventional device using a known position of the non-shape-sensed interventional device in the hub and the position of the distal tip of the non-shape-sensed interventional device.

The system provides improvements for the visualization of the non-shape-sensed interventional device during an interventional procedure by the generation of a virtual interventional device having the precise length of the interventional device. The system permits the interventional device to be a conventional over the counter device, such as a catheter, which does not require a FORS™ shape sensing system to be incorporated in the device in order for its shape, position and orientation to be tracked and visualized.

The system also includes a detection module which is configured to determine the state of the FORS™ guidewire with respect to an interventional device (either a FORS™ or a non-shape-sensed device). The detection module is configured to receive curvature data from the shape sensing system of the FORS™ guidewire and determine the state of the FORS™ guidewire and interventional device. The system may provide feedback to the user concerning the detected state. The feedback permits a user to restrict the performance of procedures to certain states or to verify the state of the devices. For example, the system may verify that the FORS™ guidewire protrudes from the interventional device in a registration procedure. The status of the FORS™ guidewire protruding from the interventional device may also indicate that the system is in a proper state for visualization by the FORS™ guidewire. The length of the interventional device may also be determined by analyzing the 3D shape position of the guidewire when the state of the FORS™ guidewire indicates that the distal tip of the guidewire is aligned with the distal tip of the interventional device.

It should be understood that the present invention will be described in terms of medical instruments; however, the teachings of the present invention are much broader and are applicable to any fiber optic instruments. In some embodiments, the present principles are employed in tracking or analyzing complex biological or mechanical systems. In particular, the present principles are applicable to internal tracking procedures of biological systems and procedures in all areas of the body such as the lungs, gastro-intestinal tract, excretory organs, blood vessels, etc. The elements depicted in the FIGS. may be implemented in various combinations of hardware and software and provide functions which may be combined in a single element or multiple elements.

The functions of the various elements shown in the FIGS. can be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions can be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which can be shared. Moreover, explicit use of the term "processor" or "controller" should not be construed to refer exclusively to hardware capable of executing software, and can implicitly include, without limitation, digital signal processor ("DSP") hardware, read-only memory ("ROM") for storing software, random access memory ("RAM"), non-volatile storage, etc..

Moreover, all statements herein reciting principles, aspects, and embodiments, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future (i.e., any elements developed that perform the same function, regardless of structure). Thus, for example, it will be appreciated by those skilled in the art that the block diagrams presented herein represent conceptual views of illustrative system components and/or circuitry embodying the principles of the invention. Similarly, it will be appreciated that any flow charts, flow diagrams and the like represent various processes which may be substantially represented in computer readable storage media and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.

Furthermore, embodiments can take the form of a computer program product accessible from a computer-usable or computer-readable storage medium providing program code for use by or in connection with a computer or any instruction execution system. For the purposes of this description, a computer-usable or computer readable storage medium can be any apparatus that may include, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The medium can be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system (or apparatus or device) or a propagation medium. Examples of a computer-readable medium include a semiconductor or solid state memory, magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disk and an optical disk. Current examples of optical disks include compact disk - read only memory (CD-ROM), compact disk - read/write (CD-R/W), Blu-Ray™ and DVD.

Reference in the specification to "one embodiment" or "an embodiment" of the present principles, as well as other variations thereof, means that a particular feature, structure, characteristic, and so forth described in connection with the embodiment is included in at least one embodiment of the present principles. Thus, the appearances of the phrase "in one embodiment" or "in an embodiment", as well any other variations, appearing in various places throughout the specification are not necessarily all referring to the same embodiment.

It is to be appreciated that the use of any of the following "/", "and/or", and "at least one of", for example, in the cases of "A/B", "A and/or B" and "at least one of A and B", is intended to encompass the selection of the first listed option (A) only, or the selection of the second listed option (B) only, or the selection of both options (A and B). As a further example, in the cases of "A, B, and/or C" and "at least one of A, B, and C", such phrasing is intended to encompass the selection of the first listed option (A) only, or the selection of the second listed option (B) only, or the selection of the third listed option (C) only, or the selection of the first and the second listed options (A and B) only, or the selection of the first and third listed options (A and C) only, or the selection of the second and third listed options (B and C) only, or the selection of all three options (A and B and C). This may be extended, as readily apparent by one of ordinary skill in this and related arts, for as many items listed.

It will also be understood that when an element such as a layer, region or material is referred to as being "on" or "over" another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" or "directly over" another element, there are no intervening elements present.

Referring now to the drawings in which like numerals represent the same or similar elements and initially to <FIG>, a system <NUM> for determining the length of a non-shape-sensed interventional device <NUM>, such as a catheter <NUM>, utilizing a shape-sensed guidewire <NUM>, such as a FORS™ guidewire, is illustratively shown in accordance with one embodiment. While the non-shape-sensed interventional device <NUM> is illustratively described as being a catheter <NUM>, in other embodiments, the device may be any medical device or instrument that includes a lumen <NUM> which may receive a guidewire, such as a sheath, a probe, an endograft deployment device, a robot, an electrode, a filter device, a balloon device, a graft, a stent or other medical component. The device that is configured to receive the FORS™ guidewire may be referred to as an "over-the-wire" device.

System <NUM> may include a workstation or console <NUM> from which a procedure is supervised and/or managed. Workstation <NUM> preferably includes one or more processors <NUM> and memory <NUM> for storing programs and applications. Memory <NUM> may store an optical sensing module <NUM> configured to interpret optical feedback signals from a shape sensing device or FORS™ system <NUM>. The FORS™ guidewire <NUM> is configured to receive the system <NUM> therethrough. The optical sensing module <NUM> is configured to use the optical signal feedback (and any other feedback) to reconstruct deformations, deflections and other changes associated with shape sensed devices.

In a preferred embodiment, the non-shaped sensed interventional device <NUM> includes a hub <NUM> that may be configured within the device <NUM>, applied (connected/coupled) to the device <NUM> or configured to fit within the device <NUM>. The hub <NUM> is employed to create shape deformation in the FORS™ guidewire <NUM>. In certain embodiments, the hub <NUM> may include a male Luer lock component at a proximal end of the guidewire lumen in the catheter <NUM>. The Luer lock is used to flush the device with saline prior to use, or to flush with contrast during use. The hub <NUM> may also have a female Luer lock on its distal portion which can mate onto the proximal end of the catheter <NUM>. This effectively extends the guidewire lumen, and the extended portion is employed to create a known curvature change.

The shape sensing system <NUM> includes one or more optical fibers which may be arranged in a set pattern or patterns. The optical fibers <NUM> connect to the workstation <NUM> through cabling. The cabling may include fiber optics, electrical connections, other instrumentation, etc., as needed.

System <NUM> with fiber optics may be based on fiber optic Bragg grating sensors, Rayleigh scattering, or other types of scattering. Inherent backscatter in conventional optical fiber can be exploited, such as Raleigh, Raman, Brillouin or fluorescence scattering. One such approach is to use Rayleigh scatter in standard single-mode communications fiber. Rayleigh scatter occurs as a result of random fluctuations of the index of refraction in the fiber core. These random fluctuations can be modeled as a Bragg grating with a random variation of amplitude and phase along the grating length. By using this effect in three or more cores running within a single length of multi-core fiber, or in multiple single-core fibers arranged together, the 3D shape and dynamics of the surface of interest can be followed.

A fiber optic Bragg grating (FBG) system may also be employed for system <NUM>. FBG is a short segment of optical fiber that reflects particular wavelengths of light and transmits all others. This is achieved by adding a periodic variation of the refractive index in the fiber core, which generates a wavelength-specific dielectric mirror. A fiber Bragg grating can therefore be used as an inline optical filter to block certain wavelengths, or as a wavelength-specific reflector.

Fresnel reflection at each of the interfaces where the refractive index is changing is measured. For some wavelengths, the reflected light of the various periods is in phase so that constructive interference exists for reflection and, consequently, destructive interference for transmission. The Bragg wavelength is sensitive to strain as well as to temperature. This means that Bragg gratings can be used as sensing elements in fiber optical sensors.

Incorporating three or more cores permits a three dimensional form of such a structure to be precisely determined. From the strain measurement, the curvature of the structure can be inferred at that position. From the multitude of measured positions, the total three-dimensional form is determined. A similar technique can be used for multiple single-core fibers configured in a known structure or geometry.

The workstation <NUM> includes a display <NUM> for viewing internal images of a subject <NUM> or volume. The workstation <NUM> includes an image processing module <NUM> that is configured to generate a virtual representation <NUM> of the non-shape-sensed device as an overlay on medical images such as x-ray images, computed tomography (CT) images, magnetic resonance images (MRI), real-time internal video images or other images as collected by an imaging system <NUM> in advance or concurrently. Display <NUM> may also permit a user to interact with the workstation <NUM> and its components and functions, or any other element within the system <NUM>. This is further facilitated by an interface <NUM> which may include a keyboard, mouse, a joystick, a haptic device, or any other peripheral or control to permit user feedback from and interaction with the workstation <NUM>.

In a preferred embodiment, as shown in <FIG>, the system <NUM> includes a catheter <NUM> which has a FORS™ guidewire <NUM> passing therethrough. The catheter <NUM> and FORS™ guidewire <NUM> are locked to a hub <NUM> which includes a Luer lock or other locking mechanism. The system <NUM> further includes an imaging system <NUM>, such as an x-ray imaging device. The x-ray imaging device is configured to acquire images of the subject <NUM> in a coordinate system of the x-ray imaging space.

The system <NUM> includes a registration module <NUM> which is configured to register the catheter <NUM> to the FORS™ guidewire <NUM>. In one embodiment, the registration module <NUM> is configured to receive a selection of the positions of the distal tip <NUM> of the FORS™ guidewire and the distal tip <NUM> of the catheter at different angles. As illustratively shown in <FIG>, in images <NUM>, <NUM>, the distal tip <NUM> of the guidewire is selected at two different angles to register the FORS™ guidewire <NUM> to the x-ray imaging space. In images <NUM>, <NUM>, the distal tip <NUM> of the catheter is selected at two different angles to register the catheter to the x-ray imaging space.

The position of the tips <NUM>, <NUM> of the FORS™ guidewire and the catheter in the images may be determined manually. For example, the registration module <NUM> may be configured to receive a command from a user through the interface <NUM> while viewing the x-ray images on a display <NUM>. Alternatively, the positions of the distal tips <NUM>, <NUM> of the FORS™ guidewire and catheter may be automatically determined by optical recognition techniques and/or markers as is generally known in the art. For example, to automatically select the catheter tip <NUM>, the catheter <NUM> may be moved to two or more positions and imaged by the imaging system <NUM>. Optical recognition techniques such as a search algorithm may be employed as is generally known in the art, to locate the catheter tip <NUM> and/or FORS™ guidewire tip <NUM>.

A determination module <NUM> is configured to receive the position of the FORS™ guidewire tip <NUM> as well as the position of the start of the FORS™ guidewire and catheter based on their securement to the hub <NUM> at a known position in the x-ray coordinate space. The determination module <NUM> is configured to determine the position of the catheter tip <NUM> relative to the hub position using the x-ray coordinates and determine the length of the catheter in order to provide an improved visualization of a virtual catheter during an interventional procedure.

The system <NUM> is also configured to determine rotation of the hub <NUM>. The registration module <NUM> is configured to register an initial angle of the hub <NUM>. For example, as shown in image <NUM> of <FIG>, the imaging system <NUM>, such as an x-ray imaging device, is configured to acquire an image of the hub <NUM>, catheter <NUM> and/or FORS™ guidewire <NUM> at a first position. The angle of the hub <NUM> at the first position is initialized to <NUM> and this position is stored by the registration module <NUM>. The imaging system <NUM> is configured to acquire additional images of the hub <NUM>, catheter <NUM> and/or FORS™ guidewire <NUM> as the hub is rotated during an interventional procedure. For example, image <NUM> of <FIG>, shows the hub <NUM>, catheter <NUM> and FORS™ guidewire <NUM> after they have been rotated. The determination module <NUM> is configured to compare the current angle of the hub <NUM> with the initial angle of the hub to determine an angular rotation of the hub. In a preferred embodiment, the hub has a unique shape or a marker which allows the current angle to be easily determined with respect to the initial angle in images acquired by the imaging system <NUM>.

Since the FORS™ guidewire <NUM> and the catheter <NUM> are both secured to the hub <NUM>, any rotation of the hub will cause a corresponding rotation of the catheter. As shown in <FIG>, the catheter <NUM> may include a distinctively shaped distal tip <NUM>. The registration module <NUM> is preferably configured to register a shape and orientation of the distal tip <NUM> of the catheter with the initial angle of rotation of the hub <NUM>. The distal tip <NUM> of the catheter is preferably in a non-foreshortened configuration during the initial registration to increase the accuracy of the registration. Furthermore, the catheter <NUM> preferably has a degree of torsional stiffness.

The determination module <NUM> is configured to utilize the comparison of the current angle of the hub <NUM> with the initial angle of the hub to determine the shape and orientation of the distal tip <NUM> of the catheter. This permits the system <NUM> to provide an accurate virtual representation <NUM> of the non-shape-sensed device even in situations where there is no shape information concerning the tip of the catheter, such as when the FORS™ guidewire <NUM> is pulled back inside the lumen <NUM> of the catheter. In alternative embodiments, the determination module <NUM> is configured to acquire the current orientation and shape of the distal tip <NUM> of the catheter in an image acquired by the imaging system <NUM> and determine the angle of rotation of the hub by comparing the current orientation and shape of the distal tip of the catheter with the registered shape and orientation of the distal tip of the catheter at the initial angle of rotation of the hub.

Alternatively, as shown in <FIG>, the system <NUM> may be configured to determine the length of the catheter <NUM> without an explicit registration of the catheter to the x-ray imaging space. In this embodiment, the registration module <NUM> is configured to store a predetermined length <NUM> of the catheter, such as the length set by the manufacturer for the device. As shown in image <NUM>, the system <NUM> is configured to generate a virtual catheter <NUM> utilizing the location of the hub <NUM> as the starting point and the predetermined length. The virtual catheter <NUM> is superimposed over an image of the catheter <NUM> acquired by the imaging system <NUM>. The actual catheter tip <NUM> in the image is selected manually or automatically.

As shown in image <NUM>, the length of the virtual catheter <NUM> differs from the actual length of the catheter shown in the image. The determination module <NUM> is configured to determine the length of the catheter <NUM> by calculating the difference <NUM> between the tip of the virtual catheter and the actual position of the catheter tip <NUM> selected in the x-ray image. As shown in image <NUM>, the system <NUM> is then configured to generate an updated virtual catheter <NUM> in accordance with the length determined by the determination module <NUM>.

In another embodiment, system <NUM> is configured to determine the length of the catheter <NUM> by registering a position of the distal tip <NUM> of the catheter when it is aligned with the distal tip <NUM> of the FORS™ guidewire. In this embodiment, the catheter tip <NUM> and the FORS™ guidewire tip <NUM> are aligned while having the catheter <NUM> and FORS™ guidewire <NUM> locked to the hub <NUM>. The registration module <NUM> is configured to designate the known position of the hub <NUM> as the start of the catheter <NUM>. The registration module <NUM> is configured to designate the position of the distal tip <NUM> of the FORS™ guidewire determined by the FORS™ system <NUM> as the ending position of the catheter <NUM>. The determination module <NUM> is configured to receive the positions and calculate the difference between the distal tip <NUM> of the FORS™ guidewire and the known position of the hub <NUM> to determine the length of the catheter <NUM>. In a preferred embodiment, smart clips are clamped over the catheter <NUM> and the FORS™ guidewire <NUM> to bend both devices at the same place and in the same direction for improved calibration.

In another embodiment shown in <FIG>, the system includes a tip hub <NUM> that is configured to interact with the distal tip <NUM> of the catheter to secure the catheter tip at a known position. In a preferred embodiment shown in <FIG>, the tip hub <NUM> is configured so that the distal end of the catheter <NUM> is secured to the tip hub <NUM> in a known, repeatable manner. For example, the lumen of the tip hub <NUM> may have dimensions which permit the FORS™ guidewire <NUM> to pass through the lumen but are too narrow to permit the catheter <NUM> to pass therethrough. In this embodiment, the distal tip <NUM> of the catheter is secured flush against the hub. The determination module <NUM> is configured to subtract the known position of the hub <NUM> and tip hub <NUM> to determine the length of the catheter <NUM>.

The tip hub <NUM> may also be configured to shape the FORS™ guidewire <NUM> in a specific manner which automatically triggers registration, such as based on a software configured to trigger the registration module <NUM> to perform registration upon recognizing a specific shape. In other embodiments, the shape of the FORS™ guidewire <NUM> within the tip hub <NUM> is uniquely identifiable. The uniquely identifiable shape allows registration to be performed automatically using a minimum length recorded.

The tip hub <NUM> is preferably temporarily installed during the registration step to determine the length of the catheter <NUM> and is removed after the registration step. The tip hub <NUM> may be temporarily secured via a clip, clamp, by hand or other methods known in the art.

The registration module <NUM> may utilize the position and initial rotational information of the FORS™ guidewire <NUM> in the hub <NUM> to correct for twisting or rotation of the catheter <NUM> as it extends from the hub to the tip hub <NUM>. For example, the extent of mismatch between the rotational angles of the proximal and distal ends of the catheter <NUM> may be determined to correct the virtual catheter or for calibration purposes.

In a preferred embodiment, the registration module <NUM> is configured to subtract the rotation angles of the device at the tip hub <NUM> from the initial position and rotational angle. The registration module <NUM> may include a look-up table <NUM> which utilizes the initial rotational information of the FORS™ guidewire <NUM> in the hub <NUM> to correct for twisting or rotation of the catheter <NUM> in the registration.

In another embodiment shown in <FIG>, the system <NUM> includes a fixture <NUM> which is configured to receive a portion of the catheter tip <NUM> which is looped back onto the fixture from the hub <NUM>. The registration module <NUM> is configured to register the catheter <NUM> using the known position of the fixture <NUM> in x-ray imaging space. In a preferred embodiment, the fixture <NUM> is fixed to a proximal segment of the FORS™ guidewire <NUM>.

Alternatively, the user may loop the catheter tip <NUM> back to the FORS™ guidewire <NUM> and hold the catheter tip in that position without the use of a fixture <NUM>. In this embodiment, the registration module <NUM> is configured to determine the position of the catheter tip <NUM> by locating a crossover point as the closest two points of the sensor.

In another embodiment, the system may include a second FORS™ guidewire. A second hub is configured to receive the second FORS™ guidewire and fix its position. The second hub is also configured to receive the catheter tip <NUM> which extends from the hub <NUM>. The position of the catheter tip <NUM> is measured by the second FORS™ guidewire and the registration module <NUM> is configured to register the catheter tip using the position of the catheter tip. Alternatively, the catheter tip <NUM> may be placed by the user in contact with a second FORS™ device that is not a guidewire.

In alternative embodiments, the catheter tip <NUM> may be determined by another localization device or procedure that is registered to the shape sensing system <NUM>. For example, the localization device or procedure may include a fixed point in space, a mechanical fixture, EM tracking, optical tracking, image-based tracking, etc. The localizer device or procedure provides determination of the position of the catheter tip <NUM>. The determination module <NUM> is configured to utilize the position of the catheter tip <NUM> determined by the registration module <NUM> and the known position of the beginning point of the catheter in the catheter hub to determine the length of the catheter <NUM> or other non-shape-sensed device <NUM>.

In another embodiment shown in <FIG>, the FORS™ guidewire <NUM> and the non-shape-sensed device <NUM>, such as a catheter <NUM>, are configured to extend from the hub <NUM> towards an internal region of the subject <NUM> with the tip of the non-shaped sensed device, such as a catheter tip <NUM>, positioned at the body insertion point <NUM>, and the FORS™ guidewire <NUM> inside the subject. The shape sensing system <NUM> of the FORS™ guidewire <NUM> is configured to measure temperature-induced strain to determine the transition point between the interior of the subject <NUM> and the exterior of the subject. The registration module <NUM> is configured to register the transition point as the distal tip of the non-shape-sensed device <NUM>. The beginning point of the non-shape-sensed device <NUM> is the hub <NUM>. The determination module <NUM> is configured to receive the positions of the proximal and distal ends of the non-shape-sensed device and determine the length of the device.

In another embodiment shown in <FIG>, the imaging system <NUM>, such as an x-ray imaging system, is configured to image the entire non-shape-sensed device <NUM> in a field of view. For example, the non-shape-sensed device <NUM> may be coiled or folded in a manner that avoids overlap with itself. The position of the non-shape-sensed device <NUM> may then be obtained in x-ray imaging coordinates. The determination module <NUM> is configured to determine the length of the non-shape-sensed device <NUM> based on the positions of the body of the non-shape-sensed device in the image. The determination module <NUM> is also configured to utilize the rotation angle of the hub to determine the length of the non-shape-sensed device based on registration of the initial rotation angle, as previously described.

As shown in <FIG>, in a further embodiment, the determination module <NUM> is configured to determine the location that an interventional tool <NUM>, such as a balloon, stent, graft, is located along the non-shape-sensed device <NUM>. In this embodiment, the interventional tool <NUM> may include radiopaque markers to help identify the interventional tool in an image, such as an x-ray image. As shown in image <NUM>, the determination module <NUM> is configured to receive a selection of the tip <NUM> of the FORS™ guidewire and the tip <NUM> of the catheter, either manually or automatically, in the x-ray image. As shown in image <NUM>, the determination module <NUM> is also configured to receive a selection of the position of the first and second ends <NUM>, <NUM> of the interventional tool <NUM> which may be selected either manually or automatically in the x-ray image. As shown in image <NUM>, the determination module <NUM> is configured to receive the position of the ends <NUM>, <NUM> of the interventional tool <NUM> and the image processing module <NUM> is configured to provide a visualization <NUM> of the interventional tool along with the virtual catheter <NUM>.

As shown in <FIG>, in other embodiments, the determination module <NUM> is configured to determine the location of an interventional tool having increased complexity, such as a fenestrated endograft <NUM>, utilizing numerous radiopaque markers based on the determined rotation of the hub <NUM>. As shown in image <NUM> of <FIG>, the fenestrated endograft <NUM> has several radiopaque markers <NUM> which help the physician orient the graft once inside the body. The registration module <NUM> may be configured to receive a selection by the user of the position of at least one of the radiopaque markers <NUM> in an image when the hub <NUM> is at an initial rotation angle. As shown in image <NUM> of <FIG>, the radiopaque markers <NUM> may be color coded with respect to the initial rotational angle of the hub/interventional tool handle and displayed as part of the virtual representation <NUM> of the endograft. When the hub <NUM> is rotated, the determination module <NUM> is configured to determine the rotation of the hub. The image processing module <NUM> is configured to rotate the color-coded radiopaque markers <NUM> on the virtual representation an amount corresponding to the rotation of the hub. The system is configured provide the virtual representation of the endograft and the radiopaque markers in non-deployed, semi-deployed, and fully deployed states of the interventional tool.

The system <NUM> also includes a detection module <NUM> that is configured to receive curvature data from the shape sensing system <NUM> concerning the tip <NUM> of the FORS™ guidewire to determine the relationship between the FORS™ guidewire <NUM> and the non-shape-sensing device <NUM>, such as the catheter <NUM>. For example, during an interventional procedure the relationship of the tip <NUM> of the FORS™ guidewire and the tip <NUM> of the catheter may have three general states: the guidewire tip may be protruding from the catheter, the guidewire tip may be inside the catheter or the catheter tip and the guidewire tip are aligned. The determination of one of these states by the detection module <NUM> is advantageous for determining whether shape registration should be performed and the appropriate image processing procedure for such registration. The determination that the tips <NUM>, <NUM> are aligned may also permit determination of the length of the catheter <NUM> or other non-shape-sensed device <NUM>.

The system <NUM> is configured to determine a maximum curvature of the FORS™ guidewire tip in a default position when there are no forces applied on the FORS™ guidewire tip and the shape of the tip is in its default form. In one embodiment, the tip <NUM> of the FORS™ guidewire is released for a relatively short period of time and the detection module <NUM> is configured to receive the shape information concerning the FORS™ guidewire <NUM> from the shape sensing system <NUM> and calculate a maximum curvature at the tip <NUM> of the FORS™ guidewire for various incoming shapes and a range of the maximum curvature of the guidewire tip. The maximum curvature estimates are stored in the detection module <NUM>. Alternatively, the maximum curvature may be measured during an initial device calibration step and stored in the detection module <NUM>.

The FORS™ guidewire <NUM> is configured to measure its curvature during a training phase wherein the guidewire is moved through a catheter lumen at numerous different positions with respect to the catheter lumen <NUM>. The detection module <NUM> is configured to collect the curvature data concerning the FORS™ guidewire from the shape sensing system <NUM> during the training phase.

In a preferred embodiment, the system <NUM> may include a training module <NUM> which is configured to provide instructions to the user concerning the movements for the FORS™ guidewire <NUM> required for the training stage so that a sufficient number of data points are collected and the data points are associated with each of the three states. The training module <NUM> may be configured to provide the instructions on the display <NUM> or through other feedback such as audio or haptic feedback. For example, the training module <NUM> may be configured to instruct the user to place the FORS™ guidewire <NUM> in various positions while inside the catheter <NUM>, protruding from the catheter and aligned with the catheter. In an alternative embodiment, a robot is utilized to manipulate the FORS™ guidewire with respect to the catheter <NUM> to acquire a large amount of curvature data.

The collection of a large amount of data in the training phase may permit the detection module <NUM> to apply sophisticated algorithms, such as deep learning to determine the curvature data and its parameters. In some embodiments, a statistical learning approach may be implemented on the training data.

As shown in <FIG>, the detection module <NUM> is configured to receive the curvature data from the shape sensing system <NUM> and plot the curvature data as a graph <NUM>. The detection module <NUM> is configured to analyze peaks <NUM> in the graph and the training data to determine the state of the FORS™ guidewire <NUM> with respect to the catheter <NUM> or other non-shape-sensed device <NUM>. For example, <FIG> show curvature data for the FORS™ guidewire <NUM> as it progresses from protruding from the catheter to its distal tip <NUM> being aligned with the distal tip <NUM> of the catheter.

In the curvature data shown in <FIG>, the first peak <NUM> has a magnitude of approximately <NUM> and the training data indicates that the catheter <NUM> is bent. The second peak <NUM> in <FIG> has a smaller magnitude that it is more distally located. The training data indicates that this curvature data is associated with the FORS™ guidewire tip <NUM> being in a state where it is protruding from the catheter <NUM>.

The detection module <NUM> is configured to determine that FORS™ guidewire tip <NUM> is protruding from the catheter <NUM> when there are two peaks visible based on the training data. The detection module <NUM> is configured to determine that the tips <NUM>, <NUM> of the FORS™ guidewire and the catheter are aligned when there is only one peak as shown in <FIG>. <FIG> show curvature data as the FORS™ guidewire <NUM> is being pulled back further inside the catheter <NUM>. The curvature data in <FIG> has a raised curvature on the rightmost side of the curvature plot indicating that the FORS™ guidewire <NUM> is just inside the catheter <NUM>. The raised curvature decreases in <FIG> until it no longer exists in <FIG>. The curvature plot in <FIG> indicates that the FORS™ guidewire <NUM> is farther inside the catheter <NUM>.

In an alternative embodiment shown in <FIG>, the detection module is configured to project the shape sensing data from the FORS™ guidewire <NUM> onto an x, y, z plane and determine 2D curvature to determine the state of the FORS™ guidewire <NUM> and catheter <NUM>. For example, the specific (x,y) projection <NUM> shown in <FIG> indicates that the guidewire tip <NUM> is protruding out of the catheter <NUM> when there are two peaks in the curvature data. The specific (x,y) projection <NUM> shown in <FIG> indicates that the tips <NUM>, <NUM> of the FORS™ guidewire and catheter are aligned with one peak in the curvature data. The specific (x,y) projection <NUM> shown in <FIG> indicates that the FORS™ guidewire <NUM> is inside the catheter <NUM> with no peak in the curvature data. The 2D curvature data computed at the aforementioned positions is useful for identifying the transition between the states. The 2D curvature may be used by the detection module <NUM> in combination with the 3D curvature data or by itself.

In one embodiment, the detection module <NUM> is configured to analyze the maximum curvature and compare the curvature to the training data acquired during the training phase. When the maximum curvature detected by the detection module <NUM> is below a threshold value determined from the training data, the detection module is configured to determine that the FORS™ guidewire tip <NUM> is inside the catheter <NUM> and the catheter tip <NUM> is protruding from the guidewire. When the maximum curvature is above the threshold, the detection module <NUM> is configured to determine that the guidewire tip <NUM> is protruding the catheter <NUM>. The determined maximum curvature of the FORS™ guidewire tip <NUM> in the default position may be utilized to normalize the measured curvature.

The detection module <NUM> is configured to send feedback to the user concerning the state of the catheter <NUM> and FORS™ guidewire <NUM>. The feedback may be provided by a graphic generated on the display <NUM> or by other feedback known in the art including audio signals or haptic feedback. For example, the feedback provided by the detection module <NUM> concerning the state of the FORS™ guidewire <NUM> and catheter <NUM> may be useful for registration, such as shape to x-ray or shape to shape registration where it is preferable that the registration procedure be performed when the guidewire protrudes from the catheter.

The state of the guidewire <NUM> and catheter <NUM> may also be utilized to determine the length of the catheter. The user may position the guidewire <NUM> so that it protrudes from the catheter <NUM> and then retracts the guidewire so that the guidewire tip <NUM> is initially aligned with the catheter tip <NUM> and the guidewire tip is then moved within the catheter. The detection module <NUM> is configured to receive the 3D shape position of the guidewire at the aligned state and estimate the catheter length using a learned model.

In an alternative embodiment shown in <FIG>, the curvature data from the FORS™ guidewire <NUM> is used to determine the catheter length from the start of the catheter to the position where the maximum curvature is exhibited. The imaging system <NUM>, such as an x-ray imaging device, is utilized to measure the length of the remaining portion of the catheter. For example, in <FIG>, the length of the catheter <NUM> between points <NUM> and <NUM> is measured by the FORS™ guidewire <NUM> in a manner previously discussed. The most distal portion of the catheter tip <NUM> is measured by identifying the points in an x-ray image.

Referring to <FIG>, methods <NUM> for determining the length of a non-shape-sensed interventional device <NUM>, such as a catheter <NUM>, are illustratively shown in accordance with the present principles. In block <NUM>, the non-shape-sensed interventional device and the FORS™ guidewire are secured to a hub having a lumen. The FORS™ guidewire is received in the lumen of the non-shape-sensed interventional device.

In block <NUM>, a position of the distal tip of the non-shape-sensed interventional device is determined. The angle of rotation of the non-shape-sensed interventional device may also be determined based on measuring the rotation of the hub or the rotation of the distal tip of the catheter. The determination of the position of the distal tip of the non-shape-sensed interventional device preferably also involves the registration <NUM> of the position of the distal tip of the non-shape-sensed interventional device to a position of the FORS™ guidewire. As previously explained, the registration of the non-shape-sensed interventional device may include a manual or automatic selection of the positions of the tip of the FORS™ guidewire and the catheter from a plurality of different angles utilizing an imaging system, such as an x-ray imaging device. Alternatively, the catheter tip and the FORS™ guidewire tip may be aligned while the devices are locked to a hub to perform the registration. The known position of the hub and the aligned tips are utilized to register the positions of the proximal and distal end of the catheter.

In another embodiment, the FORS™ guidewire and the catheter may be secured to a hub at a proximal end and the tips are secured to a tip hub to register the positions of the proximal and distal tip of the catheter. In a further embodiment, the distal tip of the catheter is received by a fixture. The catheter and the FORS™ guidewire are received by a hub and the distal tip of the catheter is looped back onto the fixture from the hub to register the distal tip of the catheter.

In another embodiment, the FORS™ guidewire and catheter extend from the hub. The tip of the catheter is positioned at the body insertion point and the FORS™ guidewire extends into the body of the subject. The FORS™ guidewire is configured to measure temperature-induced strain to determine the transition point between the interior and exterior of the subject. The hub represents the beginning point of the catheter and the transition point represents the distal tip of the catheter.

Alternatively, the position of the distal tip of the catheter may be determined without an explicit registration step. For example, the difference between the length of a catheter visualized by an imaging system and a predetermined length may be determined and the actual length may be adjusted. In another embodiment, an imaging system is configured to image the entire non-shape-sensed device, such as the catheter, in a field of view and determine the length of the catheter.

In block <NUM>, the length of the catheter is determined using the known position of the non-shape-sensed interventional device in the hub and the position of the distal tip of the non-shape-sensed interventional device.

In block <NUM>, a virtual catheter is generated based on the determined length.

In block <NUM>, the location of the interventional tool positioned along the non-shape-sensed device may also be determined as previously described utilizing radiopaque markers and an x-ray imaging registration procedure. A virtual representation of the interventional tool may be generated.

Referring to <FIG>, methods <NUM> for determining the state of a FORS™ guidewire with respect to a catheter (either a FORS™ catheter or non-shape-sensed catheter) are illustratively shown in accordance with the present principles. In block <NUM>, the FORS™ guidewire having a shape sensing system is received in a lumen of an interventional device. In block <NUM>, a maximum curvature of the FORS™ guidewire tip in a default position may be determined. In block <NUM>, the guidewire and catheter may be manipulated in a sufficient number of positions during a training phase and training data is collected.

In block <NUM>, curvature data for the FORS™ guidewire is acquired from the FORS™ shape sensing system. As previously described, the curvature data may be in the form of a graph. In block <NUM>, the curvature data is analyzed and the state of the FORS™ guidewire with respect to the interventional device is determined. For example, the curvature data may be analyzed with respect to the training data to determine the state of the FORS™ guidewire and catheter. In block <NUM>, feedback is provided to the user concerning the state of the FORS™ guidewire and catheter. In block <NUM>, the length of the catheter may be determined by the 3D shape position of the guidewire when it is aligned with the FORS™ guidewire.

Referring to <FIG>, a variable mechanical connection <NUM> is shown between a fixation point (a "torquer" <NUM>) (which may be a hub or be located proximally from a hub and catheter (shown here together as <NUM>) on a FORS-tracked guidewire <NUM> and non-shape sensed interventional device such as a catheter <NUM>. The variable mechanical connection may be in the form of a string <NUM> or rod or concertina shape tubing or braiding (coaxially around the guide wire). The torquer <NUM> is positioned and clamped at a suitable position on the guide wire <NUM>, the string <NUM> or other variable mechanical connector is attached to the torquer <NUM> with a length such that the end of the catheter <NUM> and the tip of the guide wire coincide (as shown by the stretched string <NUM> in <FIG>). The catheter <NUM> is then free to slide over a length <NUM> (the swing) of guide wire <NUM> as shown in <FIG>). The position of the torquer <NUM> and length of string 361used may be adjusted to optimize the maximum swing. A hemostatic valve <NUM> in <FIG> serves as an endpoint for sliding motion of the torquer <NUM>.

Registration of the tip of one device with respect to another is described above.

A spool may be provided, into which the string or other variable mechanical connection may be retracted. The spool may be configured to keep track of the length of the variable mechanical connection that is deployed or the length wrapped on the spool.

Very elastic tubing may be provided around a guide wire and/or braiding to keep the guidewire and variable mechanical connection together and to prevent the formation of knots or loops in the guidewire and variable mechanical connection that may catch on other parts during use.

An elastically bendable rod may connect a torquer and hub, the rod having a sliding end stop.

A quick release mechanism such as a spring, camlock, detent or lever may be provided on the torquer or hub to detach the string or other variable mechanical connection.

As explained above with respect to detection module <NUM>, the detection module <NUM> may indicate during an intervention that the guidewire tip is inside the catheter or that the catheter tip and the guidewire tip are aligned. The determination of one of these states by the detection module <NUM> is advantageous for determining whether shape registration should be performed and the appropriate image processing procedure for such registration. Then, in addition or alternatively to the torquer and variable mechanical connection's mechanically preventing the guidewire from retracting and being unable to detect the shape and position of a part of the catheter, a visual and/or haptic warning may be provided to the physician that he or she has gone beyond an appropriate operating parameter. The warning may be a buzzer or light blinking. The warning may also be generated solely based on a detected maximum extension of the variable mechanical connection.

Some materials that could realistically be used for string or braiding are those with high young's modulus, such as Kevlar and Twaron, as shown in the following Table:.

Other materials may be chosen from among the Liquid Crystal Polymers (LCPs) which are thermoplastic resins that exhibit unique, exceptional mechanical strength, heat tolerance for autoclaving, and chemical inertness. These materials are used for, among other things catheter braiding. The young's modulus is <NUM>-<NUM> GPa.

Some common shapes that may be used for the variable mechanical connection, instead of or in addition to, a string, are a shape like a concertina paper decoration <NUM> with central wire <NUM> as shown in <FIG> or a rubber bellows shape <NUM> as shown in <FIG>. Shape and material properties taken into account when specifying the variable mechanical connection may include: (<NUM>) short (flat) when folded/compressed, (<NUM>) long when expanded/deployed, (<NUM>) very little force required to go between the folded and expanded state (not elastic), and (<NUM>) when completely expanded the force required to expand further should abruptly become very high.

Claim 1:
A system (<NUM>) for determining the length of a non-shape-sensed interventional device (<NUM>), comprising:
a non-shape-sensed interventional device (<NUM>) having a lumen (<NUM>);
a shape-sensed guidewire (<NUM>) having a shape sensing system (<NUM>), configured to be received in and passing through the lumen of the non-shape-sensed interventional device;
a hub (<NUM>) configured to receive the shape-sensed guidewire and the non-shape-sensed interventional device, to secure a position of the non-shape-sensed interventional device in the hub to a position on the shape-sensed guidewire, and to encode this position as a known position;
a registration module (<NUM>) configured to register a position of a distal tip (<NUM>) of the non-shape-sensed interventional device to a position on the shape-sensed guidewire, when the shape-sensed guidewire is received in and passing through the lumen of the non-shape-sensed interventional device;
a determination module (<NUM>) configured to determine the length of the non-shape-sensed interventional device using the known position of the non-shape-sensed interventional device in the hub and the registered position of the distal tip of the non-shape-sensed interventional device; and
an image processing module (<NUM>) that is configured to generate a virtual image (<NUM>) of the non-shape-sensed interventional device based on the length determined by the determination module.