Apparatus and method for intraluminal location detection - Patents.com

Abstract

A system and method for measuring a relative displacement between at least two flexible elongate instruments in a body lumen is provided. The system includes a first flexible elongate instrument including a plurality of spatially encoded markers and a second flexible elongate instrument including two detectors. Each detector includes a single-element sensor configured to acquire a signal from the spatially encoded markers. The single-element sensor of one of the two detectors is offset from the single-element sensor of the other of the two detectors. The first and second flexible elongate instruments are configured to move relatively within the body lumen. The system further includes a controller configured to measure a relative displacement of the first and second flexible elongate instruments based on the signals acquired from the two detectors and the detected offset of the acquired signals.

Description

[Technical field]

[0001] Related Applications This application claims the benefit of U.S. Provisional Application No. 63 / 269,215, filed March 11, 2022. The entire teachings of the above application are incorporated herein by reference. [Background technology]

[0002] Intracoronary imaging is often used to accurately measure vessel and stenosis dimensions, assess vessel integrity, characterize lesion morphology, and support endoluminal procedures, including percutaneous coronary intervention (PCI) procedures. The frequency of complex percutaneous coronary interventions has steadily increased in recent years due to the clinical benefits provided by interventions that can improve life expectancy and quality of life for patients with endovascular neurosurgery, cardiovascular, and peripheral arterial disease. A variety of diagnostic and therapeutic medical devices (e.g., guidewires, balloons, atherectomy, lithotripsy, stents, imaging and physiological diagnostic modalities, x-ray angiography, and fluoroscopy) allow radiologists, cardiologists, and vascular specialists to visualize inside a patient's vessels to guide treatment decisions and perform interventional procedures. X-ray fluoroscopy with contrast injection is often used to guide physicians to place devices (e.g., stents, guidewires, and balloons) along guidewires inside the vessels toward the location of the target lesion.

[0003] In a PCI procedure, blood vessels are typically accessed through an arterial entry point, such as the radial, brachial, or femoral artery, or through a venipuncture. From the entry point, a physician can access the vasculature of organs, such as the heart, lungs, kidneys, and brain, by advancing a guidewire into the patient's body until the distal end of the guidewire crosses, for example, the lesion to be treated. After the guidewire is positioned and visible on an angiogram image, a desired therapeutic and / or diagnostic device is attached to the proximal end of the guidewire. The therapeutic and / or diagnostic device is then advanced toward the distal end to the feature of interest.

[0004] Depending on the clinical situation, imaging and / or physiological probes such as intravascular ultrasound (IVUS), optical coherence tomography (OCT), and fractional flow reserve (FFR) devices can be used to perform pre-intervention assessments such as determining lesion location, lesion dimensions, plaque morphology, and coronary pressure in the region of interest. Intraluminal diagnostic modalities such as IVUS, OCT, and FFR can generate more detailed vessel lumen information than can be obtained from x-ray imaging alone and are widely used in minimally invasive PCI procedures.

[0005] Guidance of intraluminal devices typically requires a live display of the device's movement within the body lumen. Currently available methods of guidance and positioning are based on real-time X-ray angiographic imaging, resulting in a continuous view of both the luminal pathway of the blood vessel and the intraluminal device during the procedure. X-ray imaging for vascular diagnostics and device guidance delivers X-rays at many frames per second and often requires the injection of a contrast agent, which allows visualization of the blood vessels and helps the physician locate and place the medical instrument. This method not only exposes both the patient and the physician to large amounts of radiation, but also delivers large amounts of contrast agent to the patient, which is harmful to the kidneys.

[0006] A need exists for improved systems and methods for providing intraluminal device guidance and locating medical devices within a body lumen. Summary of the Invention

[0007] SUMMARY OF THE DISCLOSURE Systems and methods are provided that enable improved position detection, including orientation and direction detection, of flexible, elongated instruments placed within a body lumen.

[0008] A system for measuring relative displacement between at least two flexible elongated instruments in a body lumen includes a first flexible elongated instrument including a plurality of spatially encoded markers and a second flexible elongated instrument including two detectors. Each detector includes a single-element sensor configured to acquire signals from the spatially encoded markers. The single-element sensor of one of the two detectors is offset from the single-element sensor of the other of the two detectors. The first and second flexible elongated instruments are configured to move relatively within the body lumen. The system further includes a controller configured to measure the relative displacement of the first and second flexible elongated instruments based on the signals acquired from the two detectors and the detected offset of the acquired signals.

[0009] The sensor offset may be a spatial offset in at least one direction, e.g., a longitudinal offset, an angular offset, or a combination thereof. In the case of a longitudinal offset, for example, one sensor is placed at a greater distance from the distal end of the device than the other sensor. This allows one sensor to lead the other sensor during instrument movement. In the case of an angular offset, for example, one sensor may be placed at a different angle relative to the first flexible elongated instrument than the other sensor, such that each sensor can see a different circumferential portion of the first flexible elongated instrument. The offset between the single element sensors may be fixed. The controller may be further configured to determine a relative direction of movement between the first and second flexible elongated instruments based on the detected offset, determine a relative change in orientation between the first and second flexible elongated instruments based on the detected offset, or a combination thereof. The spatially encoded marker may include a pattern that varies around the circumference of the first flexible elongated instrument, thereby allowing changes in orientation and / or rotation to be detected.

[0010] The position of the first flexible elongated instrument may be fixed in the reference coordinate frame, and the controller may be further configured to determine an absolute position of the second flexible elongated instrument in the reference coordinate frame based on a detected offset of the signals obtained from the two detectors.

[0011] The controller may be further configured to convert the acquired signals into code characters and determine an absolute position of one of the first and second flexible elongated instruments based on the code characters. Alternatively or additionally, the controller may be further configured to determine an incremental change in position between the first and second flexible elongated instruments based on at least one of amplitude, frequency, phase, and timing variations between the acquired signals. The determined incremental change in position may be converted into an absolute position of one of the first and second flexible elongated instruments based on the detected offset of the acquired signals from the two detectors. Typically, one of the first and second flexible elongated instruments is fixed in a reference coordinate frame. Thus, the system may detect a change in position and / or orientation of the second flexible elongated instrument relative to the first flexible elongated instrument and determine the position and / or orientation of the second flexible elongated instrument in the reference coordinate frame.

[0012] The detectors may be optical detectors and each single element sensor may be a single element optical sensor, or the detectors may be magnetic field detectors and each single element sensor may be a Hall effect sensor.

[0013] A stimulation energy source (e.g., a light source) associated with at least one of the two detectors can be configured to deliver pulsed or continuous energy. A stimulation energy source may be associated with each of the two detectors, and the stimulation energy associated with one source can vary in at least one of phase, timing, amplitude, and frequency relative to the stimulation energy of the other source.

[0014] The system may further include a localization sensor or localization marker for spatially aligning at least a subset of the coding markers to positions defined in both the system coordinate frame of reference and the coordinate frame of reference of another modality. The localization markers may be imaging markers.

[0015] The multi-modality localization method includes aligning one of the first and second flexible, elongated instruments with respect to a localization sensor or localization marker, and registering a position and orientation of one of the first and second flexible, elongated instruments based on a detected position and orientation of the localization sensor or localization marker in both a system coordinate frame of reference and a coordinate frame of reference of another modality.

[0016] The method may further include updating spatial measurements obtained from another modality based on the relative displacement of the first and second flexible elongate instruments measured by the system.

[0017] A method for measuring relative displacement between at least two flexible elongated instruments in a body lumen includes measuring relative displacement between a first flexible elongated instrument and a second flexible elongated instrument based on signals acquired from each of two detectors of the second flexible elongated instrument and a detected offset of the acquired signals. The first flexible elongated instrument includes a plurality of spatially encoded markers. The second flexible elongated instrument includes two detectors, each detector including a single-element sensor configured to acquire signals from the spatially encoded markers. The single-element sensor of one of the two detectors is offset from the single-element sensor of the other of the two detectors. The first and second flexible elongated instruments are configured to move relative to each other within the body lumen.

[0018] The method may further include determining a relative direction of movement between the first and second flexible elongate instruments based on the detected offset, determining a relative change in orientation between the first and second flexible elongate instruments based on the detected offset, or a combination thereof.

[0019] The position of the first flexible elongated instrument may be fixed in the reference coordinate frame, and the method may further include determining an absolute position of the second flexible elongated instrument in the reference coordinate frame based on the detected offset of the signals obtained from the two detectors.

[0020] The method may further include converting the acquired signal into a code character and determining an absolute position of one of the first and second flexible elongate instruments based on the code character.

[0021] The method may further include determining an incremental change in position between the first and second flexible elongate instruments based on at least one of amplitude, frequency, phase, and timing variations between the acquired signals. The determined incremental change in position may be converted to an absolute position of one of the first and second flexible elongate instruments based on the detected offset of the acquired signals from the two detectors.

[0022] The foregoing will become apparent from the following more particular description of exemplary embodiments, as illustrated in the accompanying drawings, in which like reference characters refer to the same parts throughout the different views, and in which the drawings are not necessarily to scale, emphasis instead being placed upon illustrating the embodiments. [Brief description of the drawings]

[0023] [Figure 1A] FIG. 1 is a schematic diagram of an exemplary system for measuring the relative displacement of a flexible elongated instrument within a body lumen, showing a cross-sectional schematic diagram of a catheter including two detectors having an angular offset relative to the guidewire lumen. [Figure 1B] FIG. 2 is a schematic diagram of an exemplary system for measuring relative displacement of a flexible elongated instrument within a body lumen, showing two detectors with a longitudinal offset. [Figure 1C] FIG. 1 is a schematic diagram of an exemplary system for measuring relative displacement of a flexible, elongated instrument within a body lumen, the schematic diagram showing system components having an encoded guidewire disposed within the guidewire lumen. [Diagram 2] FIG. 13 shows an exemplary detection signal obtained from a coded guidewire using a system including two detectors for detecting directional movement. [Diagram 3] FIG. 13 shows an exemplary detection signal obtained from a coded guidewire using a system including two detectors to detect rotational movement. [Figure 4] FIG. 1 is a schematic diagram of an example of a system having two photodetectors, each with a dedicated light source, and an optical coupler that can be placed outside the body. [Diagram 5] FIG. 13 is a schematic diagram of another example of a system having two photodetectors with a shared light source. [Figure 6] 1 is a schematic diagram of an exemplary configuration of two detectors in a catheter. [Figure 7A] FIG. 1 is a schematic diagram of another exemplary configuration of two detectors with a shared light source in a catheter; FIG. 2 is a cross-sectional view of a catheter with two detectors. [Figure 7B] FIG. 2 is a schematic diagram of another exemplary configuration of two detectors with a shared light source in a catheter; [Figure 8] FIG. 1 illustrates an exemplary coordinate frame of reference and alignment of device position within the coordinate frame. [Figure 9A] FIG. 1 is a schematic diagram of a prior art photodetector configuration showing an exemplary detector having an array-type sensor. [Figure 9B] FIG. 1 is a schematic diagram of a prior art photodetector configuration, showing an example of a detector having a single element sensor. [Figure 9C]FIG. 1 is a schematic diagram of a prior art photodetector configuration showing another example of a detector having a single element sensor. [Figure 10] FIG. 1 is a schematic diagram of a system having magnetic encoding and a magnetic field detector. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Examples of systems and methods providing position detection of an intraluminal instrument are described in International Publication No. WO 2022 / 126101, entitled "Methods and Systems for Body Lumen Medical Device Location," the entire teachings of which are incorporated herein by reference. Among such systems and methods are optically-based linear coding instruments. For example, such systems can include optical sensors and optical fibers incorporated in or on a flexible elongated instrument, such as a guidewire or catheter-based device, for insertion into a body lumen. Coding placed on or within another flexible elongated instrument, such as a diagnostic or therapeutic delivery device, can be detected by the optical sensor, thereby enabling relative position detection of the instrument within the body lumen. Such systems and methods can advantageously provide a profile small enough to be placed, for example, within a blood vessel, while allowing for precise location of an intraluminal diagnostic or therapeutic device within a body lumen.

[0025] Below follows a description of exemplary embodiments.

[0026] Improvements are provided to the systems and methods described in WO 2022 / 126101 that may improve position detection, including orientation and direction detection, of a flexible elongate instrument placed within a body lumen.

[0027] An exemplary system for measuring relative displacement between at least two flexible elongated instruments in a body lumen is shown in Figures 1A-1C. The system 100 includes a first flexible elongated instrument 106 (e.g., a guidewire, Figure 1C) and a second flexible elongated instrument 104 (e.g., a catheter, Figure 1A, which may be a microcatheter providing access to a diagnostic or therapeutic device). The first flexible elongated instrument 106 includes a plurality of spatially encoded markers 108 (e.g., markers that encode at least one of displacement, position, and orientation). The second flexible elongated instrument 104 includes two detectors 110, 120 (e.g., photodetectors).

[0028] As shown in Figures 1A-1C, the spatial coding marker 108 is included on or in the guidewire of the system, and the detectors 110, 120 are included on or in the catheter of the system. However, it should be understood that the coding marker may alternatively be included on the catheter or in the guidewire, and the detector may alternatively be included on or in the guidewire. For example, the guidewire may include two integrated optical fibers, and the coding placed on the microcatheter may be detected by an optical window placed on the guidewire as the microcatheter moves over the guidewire. Optionally, a guidewire catheter 102 is included, and a guidewire 106 is placed within the guidewire catheter 102 as one of the instruments is displaced relative to the other. The guidewire catheter may be made of a material that is transparent to the stimulation energy used for detection (e.g., a clear tube for optical detection, a material that allows for magnetic detection, etc.).

[0029] Each detector 110, 120 may be, for example, a photodetector. Each photodetector 110, 120 may include a single element optical sensor 112, 122 configured to acquire a signal from the displacement coding marker 108. Each photodetector 110, 120 may be, for example, an optical fiber or a tube including an optical fiber. The detectors 110, 120 may be fixed relative to each other such that the spatial offset of the two sensors 112, 122 is fixed. The offset may be a longitudinal offset (L) as shown in FIG. 1B and / or an angular offset (θ) as shown in FIG. 1A. The longitudinal offset allows the relative direction of movement between the first and second flexible elongated instruments to be determined. The angular offset allows the relative change in orientation between the first and second flexible elongated instruments to be determined. Thus, the system may not only detect linear displacement between the instruments, but also rotational displacement between the instruments, and may further detect the displacement direction in either or both cases.

[0030] A diagram illustrating an exemplary operation of system 100 is shown in Figure 2. This example is described where the detector is a photodetector and the sensor is, for example, an aperture in an optical fiber through which light reflected from the coded marker may enter the detector, although it should be understood that other types of detectors may be used, including additional examples described further herein.

[0031] As shown in FIG. 2, the coding markers 208 are markers having high and low optical reflectance and can provide binary (e.g., 0, 1) coding. Such binary markings can be further organized to provide multi-bit coding along the length of the guidewire to detect the absolute position of the catheter as it moves along the guidewire. For example, a 4-bit binary coding can detect up to 16 unique positions along the guidewire. If the position of the guidewire is fixed in another reference frame, e.g., a reference imaging frame (e.g., an x-ray image), the position of the catheter can be accurately correlated to the reference imaging frame based on the detected coding. This allows for more accurate positioning of the catheter for diagnostic or therapeutic procedures, especially when reference to another imaging modality is necessary or desirable to provide proper positioning.

[0032] Methods and systems that provide absolute position encoding and correlation with other reference frames are further described in WO 2022 / 126101. Such systems and methods utilize optical detectors integrated into either a guidewire, catheter, or other intraluminal device, such detectors being able to detect encoding placed on the other of the two devices. Such configurations can provide significant improvements over conventional systems, as further described in WO 2022 / 126101.

[0033] In endoluminal procedures, such as percutaneous coronary intervention (PCI) procedures, there may be inconsistencies or slight variations in the advancement or retraction of the instrument. It may be desirable to provide detection of the direction of movement, but this may be difficult when using a single optical detector. For example, if a detector associated with a catheter delivering a therapeutic device is moving distally and stops in an area of ​​low reflectivity (e.g., a "1"), and there is a short period of proximal movement before distal movement resumes (as may occur when a physician is manually advancing an instrument), it may not be possible to distinguish whether the next detected area of ​​high reflectivity (e.g., a "0") indicates that the device has moved proximally or distally, and code detection may be interrupted.

[0034] Returning to FIG. 2, the longitudinal offset between the two photodetector apertures 212, 222 results in a phase shift in the detected signals. For example, when moving from left to right, the detected signal 21a from aperture 212 (light grey) precedes the detected signal 22a from aperture 222 (dark grey). Similarly, when moving from right to left, the detected signal 22b from aperture 222 (dark grey) precedes the detected signal 21b from aperture 212 (light grey). The dimension of the longitudinal offset between the two apertures 212, 222 can be known, allowing the signals to be compared to distinguish between directions and, optionally, different widths of high and low reflectivity regions, as shown in FIG. 2.

[0035] A diagram illustrating another exemplary operation of the system 100 is shown in FIG. 3. Here, there is an angular offset between the apertures 312, 322 of the two photodetectors. The angular offset, together with the coding pattern 308 that varies around the circumference of the guidewire, can detect rotational and / or orientation changes between the instruments. For example, the amplitude of the signal 31 detected from aperture 312 (light grey) may differ from the amplitude of the signal 32 detected from aperture 322 (dark grey) due to different widths of high and low reflectivity regions at a given location. The dimension of the angular offset between the two apertures 312, 322 can be known, allowing the signals to be compared to distinguish orientation changes between the instruments.

[0036] Although coding having varying widths is shown in Figures 2 and 3, other measurable patterns can be used. For example, the coding of the first flexible elongate instrument can include a pattern having one or more characteristics (e.g., code bars of width, color, depth of inscription, and / or density) that vary with position around the circumference of the instrument and / or along the length of the instrument.

[0037] Including two detectors in a system (e.g., detectors 110, 120) allows for more robust signal detection and more accurate conversion to code characters. The detectors can also be used with simpler coding (e.g., two width, color, or depth coding markers), thereby reducing the complexity of decoding while still allowing directional information to be obtained from the offset of the signals from the two detectors.

[0038] Orientation and direction detection can improve mapping with other modalities. For example, the inclusion of at least two sensors in the system can provide additional degrees of measurement, such as degrees of rotation in the system reference coordinate frame. Taking into account the measured degrees of rotation in addition to other position coordinates (e.g., x, y, z coordinates in 3D space), the position of the device within the body lumen can be more accurately determined.

[0039] In conventional systems, the displacement of the diagnostic device (e.g., IVUS, FFR) is actuated by a motor drive unit located outside the patient's body, and the tracking of the displacement is also performed outside the body lumen. There may be a large discrepancy between the measured displacement of the diagnostic device estimated by the motor drive unit and the actual sensor displacement inside the body lumen. The discrepancy may be caused by the difference in diameter between the moving medical device and the guide catheter, and the effect of inherent vascular elasticity. Furthermore, accurate length measurements of vascular features may be required to properly select the size of the treatment device (e.g., angioplasty balloons, cutting balloons, and stents). Although steady-state x-ray angiography can be used to track the movement of the diagnostic sensor displacement, this method exposes the patient to undesirable amounts of contrast solution and exposes both the patient and the operator to high levels of x-ray radiation.

[0040] When a vascular endoluminal diagnostic procedure is performed, which provides more detailed information about the vessel lumen than an x-ray angiogram, a treatment decision is often made based on the endoluminal diagnostic information. The treatment decision can be based on the exact location in the vessel of the lesion. Typically, the subsequent treatment procedure is guided solely by x-ray imaging. Even with the advantage of vessel location correlation between x-ray and endoluminal diagnostic images, it may be desirable to directly visualize in real time or near real time the location of a treatment device moving inside the vessel lumen on a previously generated endoluminal diagnostic image to aid in placing the diagnostic and / or treatment device at the target vessel location identified on the diagnostic image. In some cases, a clinician may use features visible on both x-ray and endoluminal diagnostic scans, such as vessel bifurcations or severe stenosis, to identify the corresponding location in an attempt to improve the measurement accuracy of the treatment and / or diagnostic device induced during PCI.

[0041] It may therefore be advantageous to obtain instrument position tracking data using sensors placed at locations of interest within a body lumen, as opposed to relying on displacement measurements obtained from sensors placed outside the body. The use of a "single element sensor" allows the detector (or at least the sensing portion thereof) to be small enough to be incorporated into an intraluminal device.

[0042] As used herein, the term "single element sensor" refers to a non-array sensor. A "single element sensor" may be a single pixel sensor or a multiple pixel sensor that provides a single output signal. Examples of single element sensors and photodetectors that include single element sensors are further described in International Application No. PCT / US2021 / 072780. A single element sensor may be, for example, a single pixel photosensor or a Hall effect plate.

[0043] Examples of single element sensors for use in the provided system and a comparison with array type sensors are shown in Figures 9A-9C. Figure 9A shows a prior art array type sensor 4200 that is commonly used for absolute position encoding. A light source 4210 illuminates a code track 4220. Light from the light source 4210 is reflected off the code track, passes through an optical lens 4230, and is focused onto an array type sensor 4240. The array sensor 4240 includes several sensing elements or pixels. A typical array type sensor can be, for example, a CCD sensor or a CMOS sensor. The array can be either a linear array oriented in the direction of movement, or a two-dimensional array that can include thousands of pixels. The spacing information of the code lines is captured by the array sensor and communicated to a computer processor.

[0044] 9B-9C show two prior art examples of systems 4300a, 4300b with single sensing element sensors. As shown in FIG. 9B, a code track 4310 is illuminated by a light source 4320. Any type of light source can be used for illumination. Light is projected onto the code track 4310, illuminating a finite illumination area 4352 having a finite width 4350 in the direction of movement between the code track 4310 and a detector 4360. Reflected light from the code track 4310 is captured by a sensor 4370, which is a single sensing element sensor (also called a single pixel sensor). Optionally, multiple sensing elements or pixels can be used, but each sensing element or pixel may not provide a separate output, rather the sensing can be combined into a single output or single channel such that position information of each individual pixel is not captured.

[0045] As shown in FIG. 9C, the detector 4362 includes an optical fiber 4315 that transmits light from a light source 4316. A reflective surface 4325 is shown as a 45 degree polished end face of the fiber 4315 having a reflective coating. The coating can be made from many materials, such as aluminum, silver, chromium, gold, platinum, and the like, which can be applied to the surface, for example, by vacuum deposition. The light is reflected by the reflective surface 4325 and exits through a window 4365 to illuminate a finite illumination area 4335 on the code track 4310. The finite area 4335 has a finite width 4355 in the direction of travel. A portion of the reflected light from the code track 4310 re-enters the window 4365 and follows the optical fiber to a light sensor. The optical fiber can transmit light from the light source to illuminate the code track and transmit reflected light from the code track to a light sensor.

[0046] The detectors (e.g., detectors 110, 120) can be positioned within the catheter 104 (e.g., catheter 104) in various configurations relative to each other and relative to the light source (or other stimulating energy source). As shown in FIG. 1A, the detectors 110, 120 are positioned adjacent to each other and may be "active" detectors (i.e., each detector has an associated light source or other stimulating energy source). Alternatively, as shown in FIG. 6, the detectors 610, 620 can be positioned within the catheter 604 such that the detectors 610, 620 are on either side of the guidewire catheter 602. The sensors 612, 622 of each detector can be positioned to detect encoding on either side of a guidewire (not shown) positioned within the guidewire catheter 602.

[0047] 7A-7B, detectors 710, 720 may be "passive" detectors that utilize a shared light source 730 disposed within catheter 704. The shared light source 730 may illuminate a guidewire (not shown) within guidewire catheter 702. For example, as shown in FIG. 7B, an aperture 732 associated with light source 730 may be disposed between offset apertures 712, 722 of detectors 710, 720, thereby illuminating a coded marker for detection by each detector.

[0048] Additional exemplary configurations are shown in Figures 4 and 5. The system 400 includes two detectors 410, 420, each of which may include a fiber optic tube with an opening configured to allow emission of light to illuminate a code track on the guidewire and detection of light reflected from the code track. To minimize the profile of the device, optical connectors 418, 428 may be provided at locations outside the body to couple the optical fibers of the detectors 410, 420 to respective light sources 432, 438 and respective optical sensors 434, 436. A controller 440 may be configured to operate the light sources 432, 438 and receive signals from the sensors 434, 436.

[0049] If desired, a single light source can be included instead. The system 500 includes two detectors 510, 520. One detector 510 is coupled to an optical connector 518 providing a connection to a light source 532 that may be shared with the other detector 520. Each detector is coupled to a respective light sensor 534, 536. A controller 540 can be configured to operate the light source 532 and receive signals from the sensors 534, 536.

[0050] One or more light sources of the system can be configured to provide pulsed light. For example, the pulses applied to each of the two light detectors (e.g., detectors 410, 420) can have a phase shift to avoid light contamination from one detector to the other. A 180° phase shift can be applied so that the light source associated with one detector is turned on and the light source associated with the other detector is turned off. Alternatively or additionally, light detectors can be placed on both sides of the first flexible elongated instrument to reduce or avoid light contamination from each detector (see, e.g., FIG. 6).

[0051] The stimulation energy (eg, light) associated with one light source can vary in at least one of phase, timing, amplitude, and frequency relative to the stimulation energy associated with the other light source.

[0052] If desired, one light source can be provided for use with each of two light detectors (e.g., detectors 510, 520). The light sources can be located common to each of the detectors (see, e.g., Figures 7A-7B), or the detectors can be passive detectors.

[0053] A controller (e.g., controller 440, 540) can be configured to measure a relative displacement of the first and second flexible elongate instruments (e.g., guidewire 106 and catheter 104) based on the acquired signals from the two detectors and the detected offset of the acquired signals (e.g., as shown in Figures 2 and 3). The measured relative displacement can be used by the controller to determine an absolute position of the second flexible elongate instrument (e.g., based on conversion of the detected code characters to position data, taking into account the detected direction / orientation change). For example, if the position of the first flexible elongate instrument is fixed and known in a reference coordinate frame (see, e.g., Figure 8), the absolute position of the second flexible elongate instrument can be determined.

[0054] Alternatively or additionally, an incremental position change between the first and second flexible elongate instruments can be determined by the controller. The incremental position change can be based on at least one of amplitude, frequency, phase, and timing variations between the acquired signals. The determined incremental position change can be converted to a determined absolute position to increase the accuracy of measuring the position of one of the instruments during a procedure.

[0055] As shown in FIG. 8, the system may optionally include a localization sensor / marker 800 (e.g., an imaging visible marker) that may enable alignment of the system coordinate frame of reference with the coordinate frame of reference of another modality. For example, the localization markers / sensors 802, 804 may be included in a first and a second flexible elongated instrument, each of which may be a marker 800 that may appear in the imaging modality, or one of which may be a marker 800 and the other a detector that may detect the marker 800. In one example, the spatially encoded marker (or the position of the device detected from the spatially encoded marker) may be spatially aligned with one or more imaging visible markers of the system. The spatial alignment allows for alignment (e.g., automatic alignment) of the system coordinate frame of reference with the imaging frame of reference. In another example, the spatially encoded marker (or the position of the device detected from the spatially encoded marker) of the system may be spatially aligned with a localization marker that is visible or otherwise detectable in another modality.

[0056] Alignment may be performed such that at least one of the first and second flexible elongate instruments is located at a defined position and / or orientation in a complementary coordinate system, such as a coordinate system used in electromagnetic tracking / localization, ultrasound-based localization, or optical shape sensing based localization. Aligning and registering portions of the device in both coordinate systems allows the system's determination of position and orientation to be used to verify, refine, or augment spatial measurements obtained by the other modality.

[0057] Although the exemplary systems and methods have been described with respect to where the detectors are photodetectors and the stimulation energy is light, other types of detectors configured to detect other types of stimulation energy may be used.

[0058] For example, a system in which magnetic encoding and magnetic detectors are used is shown in FIG. 10. The system 900 includes a first flexible elongated instrument 906 (e.g., a guidewire as shown) and a second flexible elongated instrument 904 including two detectors 910, 920. The first flexible elongated instrument 906 includes a plurality of spatially encoded markers 908, which may be magnetically variable dimples or magnetic rings disposed on the guidewire. The sensors of the detectors 910, 920 may be Hall effect plates. Hall effect sensors are commonly known in the art. Each Hall effect plate may be supplied with a regulated voltage in one direction and may have a signal output connection laterally, such that when in a magnetic field, the Hall effect plate generates a voltage signal proportional to the magnetic field strength. In the exemplary configuration shown in FIG. 10, the output voltage from each plate is further connected to a low noise amplifier, a Schottky buffer, and an open drain field effect transistor (FET) to complete the Hall effect sensor configuration. Such elements may be positioned at locations outside the body lumen to provide a minimal device profile for insertion. As the second flexible elongate instrument 904 is displaced relative to the first flexible elongate instrument 908, the detectors 910, 920 each acquire a signal from the spatially encoded marker 908, and the separation distance between each of the detectors 910, 920 may provide an offset.

[0059] Returning to the example where the system includes photodetectors, signal conditioning can be performed on the acquired signals. For example, the signal returning from each photodetector can be an analog output from a photodiode optimized for reception of a desired wavelength (e.g., about 1310 nm). This signal can have digital attributes in that there are high amplitude regions as the sensor passes over highly reflective portions of the barcode and low amplitudes as it passes over low reflective regions of the coding marker (alternatively referred to herein as a code track or barcode). The desired wavelength can be one that has low absorption losses in water or blood (e.g., 1310 nm).

[0060] It may be advantageous to process this signal with an optimized SNR (signal-to-noise ratio). To achieve this, the signal can be adjusted to present a value close to full scale for A / D conversion. The first operation is to level-shift the signal to remove its natural offset beyond zero volts. This can be achieved by a programmable subtractor circuit, which can be adjusted to bring the minimum amplitude value of the signal close to zero volts. The second operation is to provide the necessary gain or attenuation to adjust the maximum amplitude of the signal close to the full scale value of the conversion window.

[0061] Due to signal noise and signal strength variations, further processing may be split into two paths, as described below.

[0062] The first path is to continue to treat the signal as an analog signal and perform an A / D conversion on it. Software operations can be performed to create high and low thresholds. Above the high threshold the signal is treated as a logic "1" and below the low threshold it is treated as a logic "0". The lead-lag characteristics of the two channel signal allow the direction of movement to be determined and the duration of the signal at constant amplitude allows its location within the pseudo-random serialized barcode to be identified and therefore its position.

[0063] The second path is to digitally process the conditioned signal and feed that signal to a comparator input. The comparator output can retain the lead-lag characteristics of the two-channel detector, so that the direction of movement can be determined. These digitized signals can be input directly to a timer / counter, thereby allowing the duration of the signal at a constant amplitude to be precisely measured, so that its position within the pseudo-random serialized barcode can be identified.

[0064] These two paths may be complementary, as each may be used alone to achieve both precise position and direction of movement.

[0065] The teachings of all patents, published applications and references cited herein are incorporated by reference in their entirety.

[0066] Although exemplary embodiments have been particularly shown and described, it will be understood by those skilled in the art that various changes in form and detail can be made therein without departing from the scope of the embodiments encompassed by the appended claims.

Claims

1. 1. A system for measuring relative displacement between at least two flexible elongated instruments within a body lumen, comprising: a first flexible elongate instrument including a plurality of spatially encoded markers; a second flexible, elongated instrument including two detectors, each detector including a single-element sensor configured to acquire a signal from the spatially encoded marker, the single-element sensor of one of the two detectors being offset from the single-element sensor of the other of the two detectors, and the first and second flexible, elongated instruments configured for relative movement within a body lumen; and a controller configured to measure a relative displacement of the first and second flexible elongate instruments based on the signals acquired from the two detectors and a detected offset of the acquired signals.

2. The system of claim 1 , wherein the sensor offset is a longitudinal offset, an angular offset, or a combination thereof.

3. The system of claim 1 or claim 2, wherein the offset between the single element sensors is fixed.

4. The system of any one of claims 1 to 3, wherein the controller is further configured to determine a relative direction of movement between the first and second flexible elongate instruments based on the detected offset.

5. The system of any one of claims 1 to 4, wherein the controller is further configured to determine a relative change in orientation between the first and second flexible elongate instruments based on the detected offset.

6. The system of any one of claims 1 to 5, wherein the position of the first flexible, elongated instrument is fixed within a reference coordinate frame, and the controller is further configured to determine an absolute position of the second flexible, elongated instrument in the reference coordinate frame based on the detected offset of the signals obtained from the two detectors.

7. 7. The system of claim 1, wherein the controller is further configured to determine an incremental change in position between the first and second flexible elongate instruments based on at least one of amplitude, frequency, phase, and timing variations between the acquired signals.

8. The system of claim 7 , wherein the controller is further configured to convert the determined incremental changes in position into an absolute position of one of the first and second flexible elongate instruments.

9. The system of any one of claims 1 to 8, wherein the spatially coded markers comprise a pattern that varies around the circumference of the first flexible elongate instrument.

10. The system of any one of claims 1 to 9, wherein the at least two detectors are photodetectors and the single element sensor is a single element photosensor.

11. The system of any one of claims 1 to 9, wherein the at least two detectors are magnetic field detectors and the single element sensor is a Hall effect plate.

12. The system of any one of claims 1 to 10, wherein a stimulation energy source associated with at least one of the two detectors is configured to deliver pulsed energy or continuous energy.

13. 11. The system of claim 1, wherein a stimulation energy source is associated with each of the two detectors, and the stimulation energy associated with one source varies in at least one of phase, timing, amplitude, and frequency relative to the stimulation energy associated with the other source.

14. The system of any one of claims 1 to 13, further comprising a localization sensor or localization markers for spatially aligning at least a subset of the encoded markers to positions defined in both the system's coordinate frame of reference and a coordinate frame of reference of another modality.

15. The system of claim 14 , wherein the localization marker is an imaging marker.

16. 1. A multi-modality localization method, comprising: Using the system according to any one of claims 1 to 15, further comprising a location sensor or a location marker, aligning one of the first and second flexible elongate instruments with respect to the location sensor or location marker; and registering a position and orientation of one of the first and second flexible elongate instruments based on the detected position and orientation of the localization sensor or localization marker in both the system's coordinate frame of reference and another modality's coordinate frame of reference.

17. 17. The method of claim 16, further comprising updating spatial measurements obtained from the other modality based on the relative displacement of the first and second flexible elongate instruments measured by the system.

18. 1. A method for measuring relative displacement between at least two flexible elongated instruments within a body lumen, comprising: A method comprising: measuring a relative displacement between the first flexible, elongated instrument and the second flexible, elongated instrument based on signals acquired from each of two detectors of the second flexible, elongated instrument and a detected offset of the acquired signals, wherein the first flexible, elongated instrument comprises a plurality of spatially encoded markers, the second flexible, elongated instrument comprises two detectors, each detector comprising a single-element sensor configured to acquire a signal from the spatially encoded markers, the single-element sensor of one of the two detectors being offset from the single-element sensor of the other of the two detectors, and the first and second flexible, elongated instruments are configured to move relative to one another within a body lumen.

19. The method of claim 18 , wherein the sensor offset is a longitudinal offset, an angular offset, or a combination thereof.

20. 20. The method of claim 18 or 19, wherein the offset between the single element sensors is fixed.

21. The method of any one of claims 18 to 20, further comprising determining a relative direction of movement between the first and second flexible elongate instruments based on the detected offset.

22. The method of any one of claims 18 to 21, further comprising determining a relative change in orientation between the first and second flexible elongate instruments based on the detected offset.

23. A method according to any one of claims 18 to 22, wherein the position of the first flexible, elongated instrument is fixed within a reference coordinate frame, the method further comprising determining an absolute position of the second flexible, elongated instrument in the reference coordinate frame based on the detected offset of the signals obtained from the two detectors.

24. 24. The method of any one of claims 18 to 23, wherein the method further comprises determining an incremental change in position between the first and second flexible elongate instruments based on at least one of amplitude, frequency, phase and timing variations between the acquired signals.

25. 25. The method of claim 24, further comprising converting the determined incremental changes in position into an absolute position of one of the first and second flexible elongate instruments.

26. The method of any one of claims 18 to 25, wherein the spatially coded markers comprise a pattern that varies around the circumference of the first flexible elongate instrument.

27. The method of any one of claims 18 to 26, wherein the at least two detectors are photodetectors and the single element sensor is a single element photosensor.

28. The method according to any one of claims 18 to 26, wherein the at least two detectors are magnetic field detectors and the single element sensor is a Hall effect sensor.

29. The method of any one of claims 18 to 27, wherein a stimulation energy source associated with at least one of the two detectors is configured to deliver pulsed energy or continuous energy.

30. 30. The method of any one of claims 18 to 29, wherein a stimulation energy source is associated with each of the two detectors, and the stimulation energy associated with one source varies in at least one of phase, timing, amplitude, and frequency relative to the stimulation energy associated with the other source.

31. aligning one of the first and second flexible elongate instruments with respect to a location sensor or a location marker; The method of any one of claims 18 to 30, further comprising: registering a position and orientation of one of the first and second flexible elongate instruments based on the detected position and orientation of the localization sensor or localization marker in both the system coordinate frame of reference and a coordinate frame of reference of another modality.

32. The method of claim 31 , wherein the localization marker is an imaging marker.

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