US20100030061A1 - Navigation system for cardiac therapies using gating - Google Patents

Abstract

An image guided navigation system for navigating a region of a patient which is gated using ECG signals to confirm diastole. The navigation system includes an imaging device, a tracking device, a controller, and a display. The imaging device generates images of the region of a patient. The tracking device tracks the location of the instrument in a region of the patient. The controller superimposes an icon representative of the instrument onto the images generated from the imaging device based upon the location of the instrument. The display displays the image with the superimposed instrument. The images and a registration process may be synchronized to a physiological event.

Description

FIELD OF THE INVENTION
• The present invention relates generally to image guided surgery, and more specifically, to systems and methods for using one or more medical images to assist in navigating an instrument through internal body structures, in particular for navigating a catheter in a moving body structure, such as the heart, during a surgical procedure.
BACKGROUND OF THE INVENTION
• Image guided medical and surgical procedures utilize patient images obtained prior to or during a medical procedure to guide a physician performing the procedure. Recent advances in imaging technology, especially in imaging technologies that produce two, three, and four dimensional images, such as computed tomography (CT), magnetic resonance imaging (MRI), isocentric C-arm fluoroscopic imaging, positron emission tomography (PET), and ultrasound imaging (US), has increased the interest in image guided medical procedures.
• At present, cardiac catheterization procedures are typically performed with the aid of fluoroscopic images. Two-dimensional fluoroscopic images taken intra-procedurally allow a physician to visualize the location of a catheter being advanced through cardiovascular structures. However, use of such fluoroscopic imaging throughout a procedure exposes both the patient and the operating room staff to radiation, and exposes the patient to contrast agents. Therefore, the number of fluoroscopic images taken during a procedure is preferably limited to reduce the radiation exposure to the patient and staff.
• An image guided surgical navigation system that enables the physician to see the location of an instrument relative to a patient's anatomy, without the need to acquire real-time fluoroscopic images throughout the surgical procedure is generally disclosed in U.S. Pat. No. 6,470,207, entitled “Navigational Guidance Via Computer-Assisted Fluoroscopic Imaging,” issued Oct. 22, 2002, which is incorporated herein by reference in its entirety. In this system, representations of surgical instruments are overlaid on pre-acquired fluoroscopic images of a patient based on the position of the instruments determined by a tracking sensor.
• Other types of procedures include the use of electro-physiologic mapping catheters to map the heart based on measured electrical potentials. Such mapping catheters are useful in identifying an area of tissue that is either conducting normally or abnormally, however, some mapping catheters may not aid in actually guiding a medical device to a targeted tissue area for medical treatment.
• Other procedures that could benefit from a navigation system include cardiac lead placement. Cardiac lead placement is important in achieving proper stimulation or accurate sensing at a desired cardiac location. Endocardial is one type of lead placement procedure that is an internal procedure where coronary vein leads are generally implanted with the use of a guide catheter and/or a guide wire or stylet to achieve proper placement of the lead. Epicardial is another type of procedure that is an external procedure for cardiac lead placement that may also benefit from this navigation system. A coronary vein lead may be placed using a multi-step procedure wherein a guide catheter is advanced into the coronary sinus ostium and a guide wire is advanced further through the coronary sinus and great cardiac vein to a desired cardiac vein branch. Because the tip of a guide wire is generally flexible and may be preshaped in a bend or curve, the tip of the guide wire can be steered into a desired venous branch. The guide wire tip is directed with a steerable guide catheter, and with the appropriate pressure, it is manipulated into the desired vein branch.
• A cardiac lead may therefore be advanced to a desired implant location using a guide wire extending entirely through the lead and out its distal end. Cardiac leads generally need to be highly flexible in order to withstand flexing motion caused by the beating heart without fracturing. A guide wire provides a flexible lead with the stiffness needed to advance it through a venous pathway. Leads placed with the use of a guide wire are sometimes referred to as “over-the-wire” leads. Once the lead is placed in a desired location, the guide wire and guide catheter may be removed. A guide wire placed implantable lead is disclosed in U.S. Pat. No. 6,192,280, entitled “Guide wire Placed Implantable Lead With Tip Seal,” issued Feb. 20, 2001. A coronary vein lead having a flexible tip and which may be adapted for receiving a stylet or guide wire is disclosed in U.S. Pat. No. 5,935,160, entitled “Left Ventricular Access Lead for Heart Failure Pacing”, issued Aug. 10, 1999, each of which are hereby incorporated by reference.
• Also, pacing lead procedures currently performed today for use in heart failure treatment are not optimized. In this regard, the lead placement is not optimized due to the lack of having real-time anatomic information, navigation and localization information, hemo-dynamic data, and electro-physiological data. Currently, pacing leads are simply “stuffed” into the heart without any optimization being performed due to lack of information that can be used for this optimization.
• Advancement of a guide catheter or an over-the-wire lead through a vessel pathway and through cardiac structures requires considerable skill and can be a time-consuming task. This type of procedure also exposes the patient to an undesirable amount of radiation exposure and contrast agent. Therefore, it is desirable to provide an image guided navigation system that allows the location of a guide catheter being advanced within the cardiovascular structures for lead placement to be followed in either two, three, or four dimensional space in real time. It is also desirable to provide an image guided navigation system that assists in navigating an instrument, such as a catheter, through a moving body structure or any type of soft tissue.
• With regard to navigating an instrument through a moving body structure, difficulties arise in attempting to track such an instrument using known tracking technology as the instrument passes adjacent or through a moving body structure, since the virtual representation of the instrument may be offset from the corresponding anatomy when superimposed onto image data. Accordingly, it is also desirable to acquire image data and track the instrument in a synchronized manner with the pre-acquired image using gating or synchronization techniques, such as ECG gating or respiratory gating.
• Other difficulties with cardiac procedures include annual check-ups to measure early indications for organ rejection in heart transplant patients. These indicators include white blood cells, chemical change, blood oxygen levels, etc. During the procedure, an endovascular biopsy catheter is inserted into the heart and multiple biopsies are performed in the septum wall of the heart. Again, during this procedure, radiation and contrast agent is utilized to visualize the biopsy catheter, thereby exposing both a patient and the doctor to potential excess radiation and contrast agents during the procedure. As such, it would also be desirable to provide an image guided navigation system that assists in performing this type of procedure in order to reduce radiation and contrast agent exposure.
SUMMARY OF THE INVENTION
• A navigation system is provided including a catheter carrying single or multiple localization sensors, a sensor interface, a user interface, a controller, and a visual display. Aspects of the present invention allow for the location of a catheter advanced within an internal space within the human body, for example within the cardiovascular structures, to be identified in two, three or four dimensions in real time. Further aspects of the present invention allow for accurate mapping of a tissue or organ, such as the heart or other soft tissue, and/or precise identification of a desired location for delivering a medical lead, or other medical device or therapy, while reducing the exposure to fluoroscopy normally required during conventional catheterization procedures. These types of therapies include, but are not limited to, drug delivery therapy, cell delivery therapy, ablation, stenting, or sensing of various physiological parameters with the appropriate type of sensor. In cardiac applications, methods included in the present invention compensate for the effects of respiration and the beating heart that can normally complicate mapping or diagnostic data. Aspects of the present invention may be tailored to improve the outcomes of numerous cardiac therapies as well as non-cardiac therapies, such as neurological, oncological, or other medical therapies, including lung, liver, prostate and other soft tissue therapies, requiring the use of a catheter or other instrument at a precise location.
• The steerable catheter provided by the present invention features at least one or more location sensors located near the distal end of an elongated catheter body. The location sensors may be spaced axially from each other and may be electromagnetic detectors. An electromagnetic source is positioned externally to the patient for inducing a magnetic field, which causes voltage to be developed on the location sensors. The location sensors may each be electrically coupled to twisted pair conductors, which extend through the catheter body to the proximal catheter end. Twisted pair conductors provide electromagnetic shielding of the conductors, which prevents voltage induction along the conductors when exposed to the magnetic flux produced by the electromagnetic source. Alternatively, the sensors and the source may be reversed where the catheter emits a magnetic field that is sensed by external sensors.
• By sensing and processing the voltage signals from each location sensor, the location of the catheter tip with respect to the external sources and the location of each sensor with respect to one another may be determined. The present invention allows a two, three, or four-dimensional reconstruction of several centimeters of the distal portion of the catheter body in real time. Visualization of the shape and position of a distal portion of the catheter makes the advancement of the catheter to a desired position more intuitive to the user. The system may also provide a curve fitting algorithm that is selectable based upon the type of catheter used, and based upon the flexibility of the catheter, based upon a path finding algorithm, and based upon image data. This enables estimated curved trajectories of the catheter to be displayed to assist the user.
• The location sensor conductors, as well as conductors coupled to other physiological sensors present, are coupled to a sensor interface for filtering, amplifying, and digitizing the sensed signals. The digitized signals are provided via a data bus to a control system, embodied as a computer. Programs executed by the control system process the sensor data for determining the location of the location sensors relative to a reference source. A determined location is superimposed on a two, three, or four-dimensional image that is displayed on a monitor. A user-interface, such as a keyboard, mouse or pointer, is provided for entering operational commands or parameters.
• In one embodiment, an image guided navigation system for guiding an instrument through a region of the patient includes an anatomic gating device, an imaging device, a tracking device, a controller, and a display. The anatomic gating device senses a first and second physiological event. The imaging device captures image data in response to the first and second physiological event. The tracking device tracks the position of the instrument in the region of the patient. The controller is in communication with the anatomic gating device, the imaging device and the tracking device, and registers the image data with the region of a patient in response to the first and second physiological event. The controller also superimposes an icon representing the instrument onto the image data, based on the tracked position. The display shows the image data of the region of the patient with the superimposed icon of the instrument.
• Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
• The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
• FIG. 1 is a diagram of a catheter navigation system according to the teachings of the present invention;
• FIGS. 2aand2bare diagrams representing undistorted and distorted views from a fluoroscopic C-arm imaging device;
• FIG. 3 is a logic block diagram illustrating a method for navigating a catheter during cardiac therapy;
• FIG. 4 is a logic block diagram illustrating the R-wave detector associated with the method for navigating a catheter during cardiac therapy as shown inFIG. 3;
• FIG. 5 is a logic block diagram illustrating the diastole detector associated with the method for navigating a catheter during cardiac therapy as shown inFIG. 3; and
• FIG. 6 is a logic block diagram illustrating the gating phase of the diastole detector illustrated inFIG. 5.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. As indicated above, the present invention is directed at providing improved, non-line-of-site, image-guided navigation of an instrument, such as a catheter, balloon catheter, implant, lead, stent, needle, guide wire, insert, and/or capsule, that may be used for physiological monitoring, delivering a medical therapy, or guiding the delivery of a medical device in an internal body space, such as the heart or any other region of the body.
• FIG. 1 is a diagram illustrating an overview of an image-guidedcatheter navigation system10 for use in non-line-of-site navigating of a catheter during cardiac therapy or any other soft tissue therapy. It should further be noted that thenavigation system10 may be used to navigate any other type of instrument or delivery system, including guide wires, needles, drug delivery systems, cell delivery systems, gene delivery systems, and biopsy systems. Moreover, these instruments may be used for cardiac therapy or any other therapy in the body or be used to navigate or map any other regions of the body, such as moving body structures. However, each region of the body poses unique requirements to navigate, as disclosed herein. For example, thenavigation system10 addresses multiple cardiac, neurological, organ and other soft tissue therapies, including drug delivery, cell transplantation, gene delivery, electro-physiology ablations, revascularization, biopsy guidance, mitral valve repair, aortic valve repair, leadless pacemaker placement, leadless pressure sensor placement, and virtual echography imaging.
• Thenavigation system10 may include animaging device12 that is used to acquire pre-operative or real-time images of apatient14. Theimaging device12 is a fluoroscopic x-ray imaging device that may include a C-arm16 having anx-ray source18, anx-ray receiving section20, an optional calibration and trackingtarget22, andoptional radiation sensors24. The calibration and trackingtarget22 includes calibration markers26 (seeFIGS. 2a-2b), further discussed herein. A C-arm controller28 captures the x-ray images received at the receivingsection20 and stores the images for later use. The C-arm controller28 may also control the rotation of the C-arm16. For example, the C-arm16 may move in the direction ofarrow30 or rotates about the long axis of the patient, allowing anterior or lateral views of the patient14 to be imaged. Each of these movements involve rotation about amechanical axis32 of the C-arm16. In this example, the long axis of thepatient14 is substantially in line with themechanical axis32 of the C-arm16. This enables the C-arm16 to be rotated relative to thepatient14, allowing images of the patient14 to be taken from multiple directions or about multiple planes. An example of a fluoroscopic C-armx-ray imaging device12 is the “Series 9600 Mobile Digital Imaging System,” from OEC Medical Systems, Inc., of Salt Lake City, Utah. Other exemplary fluoroscopes include bi-plane fluoroscopic systems, ceiling fluoroscopic systems, cath-lab fluoroscopic systems, fixed C-arm fluoroscopic systems, isocentric C-arm fluoroscopic systems, 3D fluoroscopic systems, etc.
• In operation, theimaging device12 generates x-rays from thex-ray source18 that propagate through thepatient14 and calibration and/or trackingtarget22, into thex-ray receiving section20. The receivingsection20 generates an image representing the intensities of the received x-rays. Typically, the receivingsection20 includes an image intensifier that first converts the x-rays to visible light and a charge coupled device (CCD) video camera that converts the visible light into digital images. Receivingsection20 may also be a digital device that converts x-rays directly to digital images, thus potentially avoiding distortion introduced by first converting to visible light. With this type of digital C-arm, which is generally a flat panel device, the optional calibration and/or trackingtarget22 and the calibration process discussed below may be eliminated. Also, the calibration process may be eliminated or not used at all for cardiac therapies. Alternatively, theimaging device12 may only take a single image with the calibration and trackingtarget22 in place. Thereafter, the calibration and trackingtarget22 may be removed from the line-of-sight of theimaging device12.
• Two-dimensional fluoroscopic images taken by theimaging device12 are captured and stored in the C-arm controller28. Multiple two-dimensional images taken by theimaging device12 may also be captured and assembled to provide a larger view or image of a whole region of a patient, as opposed to being directed to only a portion of a region of the patient. For example, multiple image data of a patient's leg may be appended together to provide a full view or complete set of image data of the leg that can be later used to follow a contrast agent, such as Bolus tracking. These images are then forwarded from the C-arm controller28 to a controller orwork station34 having adisplay36 and auser interface38. Thework station34 provides facilities for exhibiting on thedisplay36, and saving, digitally manipulating, or printing a hard copy of the received images. Theuser interface38, which may be a keyboard, mouse, touch pen, touch screen or other suitable device, allows a physician or user to provide inputs to control theimaging device12 via the C-arm controller28, or adjust the display settings of thedisplay36. Thework station34 may also direct the C-arm controller28 to adjust therotational axis32 of the C-arm16 to obtain various two-dimensional images along different planes in order to generate representative two-dimensional and three-dimensional images. When thex-ray source18 generates the x-rays that propagate to thex-ray receiving section20, theradiation sensors24 sense the presence of radiation, which is forwarded to the C-arm controller28 to identify whether or not theimaging device12 is actively imaging. This information is also transmitted to acoil array controller48, further discussed herein. Alternatively, a person or physician may manually indicate when theimaging device12 is actively imaging or this function can be built into thex-ray source18,x-ray receiving section20, or thecontrol computer28.
• Fluoroscopic C-arm imaging devices12 that do not include adigital receiving section20 generally require the optional calibration and/or trackingtarget22. This is because the raw images generated by the receivingsection20 tend to suffer from undesirable distortion caused by a number of factors, including inherent image distortion in the image intensifier and external electromagnetic fields. An empty undistorted or ideal image and an empty distorted image are shown inFIGS. 2aand2b, respectively. The checkerboard shape, shown inFIG. 2a, represents theideal image40 of the checkerboard-arrangedcalibration markers26. The image taken by the receivingsection20, however, can suffer from distortion, as illustrated by the distortedcalibration marker image42, shown inFIG. 2b.
• Intrinsic calibration, which is the process of correcting image distortion in a received image and establishing the projective transformation for that image, involves placing thecalibration markers26 in the path of the x-ray, where thecalibration markers26 are opaque or semi-opaque to the x-rays. Thecalibration markers26 are rigidly arranged in pre-determined patterns in one or more planes in the path of the x-rays and are visible in the recorded images. Because the true relative position of thecalibration markers26 in the recorded images are known, the C-arm controller28 or the work station orcomputer34 is able to calculate an amount of distortion at each pixel in the image (where a pixel is a single point in the image). Accordingly, the computer orwork station34 can digitally compensate for the distortion in the image and generate a distortion-free or at least a distortion-improved image40 (seeFIG. 2a). A more detailed explanation of exemplary methods for performing intrinsic calibration is described in the references: B. Schuele, et al., “Correction of Image Intensifier Distortion for Three-Dimensional Reconstruction,” presented at SPIE Medical Imaging, San Diego, Calif., 1995; G. Champleboux, et al., “Accurate Calibration of Cameras and Range Imaging Sensors: the NPBS Method,” Proceedings of the IEEE International Conference on Robotics and Automation, Nice, France, May, 1992; and U.S. Pat. No. 6,118,845, entitled “System And Methods For The Reduction And Elimination Of Image Artifacts In The Calibration Of X-Ray Imagers,” issued Sep. 12, 2000, the contents of which are each hereby incorporated by reference.
• While thefluoroscopic imaging device12 is shown inFIG. 1, any other alternative 2D, 3D or 4D imaging modality may also be used. For example, any 2D, 3D or 4D imaging device, such as isocentric fluoroscopy, bi-plane fluoroscopy, ultrasound, computed tomography (CT), multi-slice computed tomography (MSCT), magnetic resonance imaging (MRI), high frequency ultrasound (HIFU), positron emission tomography (PET), positron emission tomography-computed tomography (PET/CT), high definition computed tomography (HDCT), dual source computed tomography, optical coherence tomography (OCT), intra-vascular ultrasound (IVUS), ultrasound, intra-operative CT or MRI, may also be used to acquire 2D, 3D or 4D pre-operative or real-time images or image data of thepatient14. The images may also be obtained and displayed in two, three or four dimensions. In more advanced forms, four-dimensional surface rendering of the heart or other regions of the body may also be achieved by incorporating heart data or other soft tissue data from an atlas map or from pre-operative image data captured by MRI, CT, or echocardiography modalities. A more detailed discussion on optical coherence tomography (OCT), is set forth in U.S. Pat. No. 5,740,808, issued Apr. 21, 1998, entitled “Systems And Methods For Guilding Diagnostic Or Therapeutic Devices In Interior Tissue Regions” which is hereby incorporated by reference.
• Image datasets from hybrid modalities, such as positron emission tomography (PET) combined with CT, or single photon emission computer tomography (SPECT) combined with CT, could also provide functional image data superimposed onto anatomical data to be used to confidently reach target sights within the heart or other areas of interest. It should further be noted that thefluoroscopic imaging device12, as shown inFIG. 1, provides a virtual bi-plane image using a single-head C-arm fluoroscope12 by simply rotating the C-arm16 about at least two planes, which could be orthogonal planes to generate two-dimensional images that can be converted to three-dimensional volumetric images. By acquiring images in more than one plane, an icon representing the location of a catheter or other instrument, introduced and advanced in thepatient14, may be superimposed in more than one view ondisplay36 allowing simulated bi-plane or even multi-plane views, including two and three-dimensional views.
• These types of imaging modalities may provide certain distinct benefits and disadvantages for their use. For example, magnetic resonance imaging (MRI) is generally performed pre-operatively using a non-ionizing field. This type of imaging provides very good tissue visualization in three-dimensional form and also provides anatomical and functional information from the imaging. MRI imaging data is generally registers and compensates for motion correction using dynamic reference frames that are discussed herein.
• Positron emission tomography (PET) imaging is generally a pre-operative imaging procedure that exposes the patient to some level of radiation to provide a 3D image. PET imaging provides functional information and also generally requires registration and motion correction using dynamic reference frames.
• Computed tomography (CT) imaging is also generally a pre-operative technique that exposes the patient to a limited level of radiation. CT imaging, however, is a very rapid imaging procedure. A multi-slice CT system provides 3D images having good resolution and anatomical information. Again, CT imaging is generally registered and needs to account for motion correction via dynamic reference frames.
• Fluoroscopy imaging is generally an intra-operative imaging procedure that exposes the patient to certain amounts of radiation to provide either two-dimensional or rotational three-dimensional images. Fluoroscopic images generally provide good resolution and anatomical information. Fluoroscopic images can be either manually or automatically registered and also need to account for motion correction using dynamic reference frames.
• Ultrasound imaging is also generally an intra-operative procedure using a non-ionizing field to provide either 2D, 3D, or 4D imaging, including anatomical and blood flow information. Ultrasound imaging provides automatic registration and does not need to account for any motion correction.
• Thenavigation system10 further includes an electromagnetic navigation or trackingsystem44 that includes atransmitter coil array46, thecoil array controller48, anavigation probe interface50, anelectromagnetic catheter52 or any other type of instrument and adynamic reference frame54. Further, it should further be noted that theentire tracking system44 or parts of thetracking system44 may be incorporated into theimaging device12, including thework station34 andradiation sensors24. Incorporating thetracking system44 will provide an integrated imaging and tracking system. Any combination of these components may also be incorporated into theimaging device12, which again can include a fluoroscopic C-arm imaging device or any other appropriate imaging device.
• Thetransmitter coil array46 is shown attached to the receivingsection20 of the C-arm16. However, it should be noted that thetransmitter coil array46 may also be positioned at any other location as well. For example, thetransmitter coil array46 may be positioned at thex-ray source18, within or atop the OR table56 positioned below thepatient14, on siderails associated with the table56, or positioned on the patient14 in proximity to the region being navigated, such as on the patient's chest. Thetransmitter coil array46 includes a plurality of coils that are each operable to generate distinct electromagnetic fields into the navigation region of thepatient14, which is sometimes referred to as patient space. Representative electromagnetic systems are set forth in U.S. Pat. No. 5,913,820, entitled “Position Location System,” issued Jun. 22, 1999, and U.S. Pat. No. 5,592,939, entitled “Method and System for Navigating a Catheter Probe,” issued Jan. 14, 1997, each of which are hereby incorporated by reference.
• Thetransmitter coil array46 is controlled or driven by thecoil array controller48. Thecoil array controller48 drives each coil in thetransmitter coil array46 in a time division multiplex or a frequency division multiplex manner. In this regard, each coil may be driven separately at a distinct time or all of the coils may be driven simultaneously with each being driven by a different frequency. Upon driving the coils in thetransmitter coil array46 with thecoil array controller48, electromagnetic fields are generated within thepatient14 in the area where the medical procedure is being performed, which is again sometimes referred to as patient space. The electromagnetic fields generated in the patient space induces currents insensors58 positioned in thecatheter52. These induced signals from thecatheter52 are delivered to thenavigation probe interface50 and subsequently forwarded to thecoil array controller48. Thenavigation probe interface50 provides all the necessary electrical isolation for thenavigation system10. Thenavigation probe interface50 also includes amplifiers, filters and buffers required to directly interface with thesensors58 incatheter52. Alternatively, thecatheter52 may employ a wireless communications channel as opposed to being coupled directly to thenavigation probe interface50.
• Thecatheter52 may be equipped with at least one, and generally multiple,localization sensors58. Thecatheter52 may also be a steerable catheter that includes a handle at a proximal end and themultiple location sensors58 fixed to the catheter body and spaced axially from one another along the distal segment of thecatheter52. Thecatheter52, as shown inFIG. 1, includes fourlocalization sensors58. Thelocalization sensors58 are generally formed as electromagnetic receiver coils, such that the electromagnetic field generated by thetransmitter coil array46 induces current in the electromagnetic receiver coils orsensors58. Thecatheter52 may also be equipped with one or more sensors, which are operable to sense various physiological signals. For example, thecatheter52 may be provided with electrodes for sensing myopotentials or action potentials. An absolute pressure sensor may also be included, as well as other electrode sensors. Thecatheter52 may also be provided with an open lumen to allow the delivery of a medical device or pharmaceutical/cell/gene agents. For example, thecatheter52 may be used as a guide catheter for deploying a medical lead, such as a cardiac lead for use in cardiac pacing and/or defibrillation or tissue ablation. The open lumen may alternatively be used to locally deliver pharmaceutical agents, cell, or genetic therapies. A representative catheter which may be used is that which is disclosed in U.S. Patent Publication No. 2004/0097805 entitled “Navigation System for Cardiac Therapies”, filed Jul. 14, 2003, which is hereby incorporated by reference.
• In an alternate embodiment, the electromagnetic sources or generators may be located within thecatheter52 and one or more receiver coils may be provided externally to thepatient14, forming a receiver coil array similar to thetransmitter coil array46. In this regard, the sensor coils58 would generate electromagnetic fields, which would be received by the receiving coils in the receiving coil array similar to thetransmitter coil array46. Other types of localization sensors or systems may also be used, which may include an emitter, which emits energy, such as light, sound, or electromagnetic radiation, and a receiver that detects the energy at a position away from the emitter. This change in energy, from the emitter to the receiver, is used to determine the location of the receiver relative to the emitter. Other types of tracking systems include optical, acoustic, electrical field, RF and accelerometers. Accelerometers enable both dynamic sensing due to motion and static sensing due to gravity. An additional representative alternative localization and tracking system is set forth in U.S. Pat. No. 5,983,126, entitled “Catheter Location System and Method,” issued Nov. 9, 1999, which is hereby incorporated by reference. Alternatively, the localization system may be a hybrid system that includes components from various systems.
• Thedynamic reference frame54 of theelectromagnetic tracking system44 is also coupled to thenavigation probe interface50 to forward the information to thecoil array controller48. Thedynamic reference frame54 is a small magnetic field detector that is designed to be fixed to the patient14 adjacent to the region being navigated so that any movement of thepatient14 is detected as relative motion between thetransmitter coil array46 and thedynamic reference frame54. This relative motion is forwarded to thecoil array controller48, which updates registration correlation and maintains accurate navigation, further discussed herein. Thedynamic reference frame54 can be configured as a pair of orthogonally oriented coils, each having the same center or may be configured in any other non-coaxial coil configuration. Thedynamic reference frame54 may be affixed externally to thepatient14, adjacent to the region of navigation, such as on the patient's chest, as shown inFIG. 1 or on the patient's back. Thedynamic reference frame54 can be affixed to the patient's skin, by way of a stick-on adhesive patch. Thedynamic reference frame54 may also be removably attachable tofiducial markers60 also positioned on the patient's body as further discussed herein.
• Alternatively, thedynamic reference frame54 may be internally attached, for example, to the wall of the patient's heart or other soft tissue using a temporary lead that is attached directly to the heart. This provides increased accuracy since this lead will track the regional motion of the heart. Gating, as further discussed herein, will also increase the navigational accuracy of thesystem10. An exemplarydynamic reference frame54 andfiducial marker60, is set forth in U.S. Pat. No. 6,381,485, entitled “Registration of Human Anatomy Integrated for Electromagnetic Localization,” issued Apr. 30, 2002, which is hereby incorporated by reference. It should further be noted that multipledynamic reference frames54 may also be employed. For example, an externaldynamic reference frame54 may be attached to the chest of thepatient14, as well as to the back of thepatient14. Since certain regions of the body may move more than others due to motions of the heart or the respiratory system, eachdynamic reference frame54 may be appropriately weighted to increase accuracy even further. In this regard, thedynamic reference frame54 attached to the back may be weighted higher than thedynamic reference frame54 attached to the chest, since thedynamic reference frame54 attached to the back is relatively static in motion.
• The catheter andnavigation system10 further includes a gating device or an ECG orelectrocardiogram62, which is attached to thepatient14, viaskin electrodes64, and in communication with thecoil array controller48. Respiration and cardiac motion can cause movement of cardiac structures relative to thecatheter52, even when thecatheter52 has not been moved. Therefore, localization data may be acquired on a time-gated basis triggered by a physiological signal. For example, the ECG or EGM signal may be acquired from theskin electrodes64 or from a sensing electrode included on thecatheter52 or from a separate reference probe. As will be discussed more fully below, a characteristic of this signal may be used as to gate or trigger image acquisition during the imaging phase with theimaging device12. By event gating at a point in a cycle the image data and/or the navigation data, the icon of the location of thecatheter52 relative to the heart at the same point in the cardiac cycle may be displayed on thedisplay36, further discussed herein.
• Additionally or alternatively, a sensor regarding respiration may be used to trigger data collection at the same point in the respiration cycle. Additional external sensors can also be coupled to thenavigation system10. These could include a capnographic sensor that monitors exhaled CO₂concentration. From this, the end expiration point can be easily determined. The respiration, both ventriculated and spontaneous causes an undesirable elevation or reduction, respectively, in the baseline pressure signal. By measuring systolic and diastolic pressures at the end expiration point, the coupling of respiration noise is minimized. As an alternative to the CO₂sensor, an airway pressure sensor can be used to determine end expiration.
• Briefly, thenavigation system10 operates as follows. Thenavigation system10 creates a translation map between all points in the radiological image generated from theimaging device12 and the corresponding points in the patient's anatomy in patient space. After this map is established, whenever a tracked instrument, such as thecatheter52 or pointing device is used, thework station34, in combination with thecoil array controller48 and the C-arm controller28, uses the translation map to identify the corresponding point on the pre-acquired image, which is exhibited ondisplay36. This identification is known as navigation or localization. An icon representing the localized point or instruments are shown on thedisplay36 within several two-dimensional image planes, as well as on three and four dimensional images and models.
• To enable navigation, thenavigation system10 must be able to detect both the position of the patient's anatomy and the position of thecatheter52 or other surgical instrument. Knowing the location of these two items allows thenavigation system10 to compute and display the position of thecatheter52 in relation to the patient14 on the radiological images. Thetracking system44 is employed to track thecatheter52 and the anatomy simultaneously.
• Thetracking system44 essentially works by positioning thetransmitter coil array46 adjacent to the patient space to generate a low-energy magnetic field generally referred to as a navigation field. Because every point in the navigation field or patient space is associated with a unique field strength, theelectromagnetic tracking system44 can determine the position of thecatheter52 by measuring the field strength at thesensor58 location. Thedynamic reference frame54 is fixed to the patient14 to identify the location of the patient in the navigation field. Theelectromagnetic tracking system44 continuously recomputes the relative position of thedynamic reference frame54 and thecatheter52 during localization and relates this spatial information to patient registration data to enable image guidance of thecatheter52 within thepatient14.
• Patient registration is the process of determining how to correlate the position of the instrument orcatheter52 on the patient14 to the position on the diagnostic or pre-acquired images. To register thepatient14, the physician or user may use point registration by selecting and storing particular points from the pre-acquired images and then touching the corresponding points on the patient's anatomy with apointer probe66. Thenavigation system10 analyzes the relationship between the two sets of points that are selected and computes a match, which correlates every point in the image data with its corresponding point on the patient's anatomy or the patient space. The points that are selected to perform registration are the fiducial arrays orlandmarks60. Again, the landmarks orfiducial points60 are identifiable on the images and identifiable and accessible on thepatient14. Thelandmarks60 can beartificial landmarks60 that are positioned on the patient14 or anatomical landmarks that can be easily identified in the image data. Thesystem10 may also perform registration using anatomic surface information or path information, further discussed herein. Thesystem10 may also perform 2D to 3D registration by utilizing the acquired 2D images to register 3D volume images by use of contour algorithms, point algorithms or density comparison algorithms, as is known in the art. An exemplary 2D to 3D registration procedure, as set forth in U.S. Patent Publication No. 2004/0215671, entitled “Method and Apparatus for Performing 2D to 3D Registration,” which is hereby incorporated by reference. The registration process may also be synched to an anatomical function, for example, by the use of theECG device62, further discussed herein.
• In order to maintain registration accuracy, thenavigation system10 continuously tracks the position of the patient14 during registration and navigation. This is because thepatient14,dynamic reference frame54, andtransmitter coil array46 may all move during the procedure, even when this movement is not desired. Therefore, if thenavigation system10 did not track the position of the patient14 or area of the anatomy, any patient movement after image acquisition would result in inaccurate navigation within that image. Thedynamic reference frame54 allows theelectromagnetic tracking system44 to register and track the anatomy. Because thedynamic reference frame54 is attached to thepatient14, any movement of the anatomy or thetransmitter coil array46 is detected as the relative motion between thetransmitter coil array46 and thedynamic reference frame54. This relative motion is communicated to thecoil array controller48, via thenavigation probe interface50, which updates the registration correlation to thereby maintain accurate navigation.
• Turning now toFIG. 3, a logic flow diagram illustrating an exemplary operation of thenavigation system10 is set forth in further detail. First, should theimaging device12 or the fluoroscopic C-arm imager12 not include adigital receiving section20, theimaging device12 is first calibrated using thecalibration process68. Thecalibration process68 begins atblock70 by generating an x-ray by thex-ray source18, which is received by thex-ray receiving section20. Thex-ray image70 is then captured or imported atimport block72 from the C-arm controller28 to thework station34. Thework station34 performs intrinsic calibration atcalibration block74, as discussed above, utilizing thecalibration markers26, shown inFIGS. 2aand2b. This results in an empty image being calibrated atblock76. This calibrated empty image is utilized for subsequent calibration and registration, further discussed herein.
• Once theimaging device12 has been calibrated, thepatient14 is positioned within the C-arm16 between thex-ray source18 and thex-ray receiving section20. The navigation process begins atdecision block78 where it is determined whether or not an x-ray image of thepatient14 has been taken. If the x-ray image has not been taken, the process proceeds to block80 where the x-ray image is generated at thex-ray source18 and received at thex-ray receiving section20. In some embodiments, when thex-ray source18 is generating x-rays, theradiation sensors24 identified inblock82 may activate to identify that thex-ray image80 is being taken. This enables thetracking system44 to identify where the C-arm16 is located relative to the patient14 when the image data is being captured. In some embodiments, however, thetracking system44 may not need to be triggered by theradiation sensors24.
• The process then proceeds todecision block84 where it is determined if the x-ray image acquisition will be gated to physiological activity of thepatient14. If so, theimage device12 will capture the x-ray image at this desired gating time. For example, the physiological change may be the beating heart, which is identified by ECG gating atblock86. The ECG gating enables the x-ray image acquisition to take place at the end of diastole atblock88, as will be more fully discussed below. Diastole is the period of time between contractions of the atria or the ventricles during which blood enters the relaxed chambers from systemic circulation and the lungs. Diastole is often measured as the blood pressure at the instant of maximum cardiac relaxation. ECG gating of myocardial injections also enables optimal injection volumes and injection rates to achieve maximum cell retention. The optimal injection time period may go over one heart cycle. During the injection, relative motion of the catheter tip to the endocardial surface needs to be minimized. Conductivity electrodes at the catheter tip may be used to maintain this minimized motion. Also, gating the delivery of volumes can be used to increase or decrease the volume delivered over time (i.e., ramp-up or ramp-down during cycle). Again, the image may be gated to any physiological change like the heartbeat, respiratory functions, etc. The image acquired atblock88 is then imported to thework station34 atblock90. If it is not desired to physiologically gate the image acquisition cycle, the process will proceed from thex-ray image block80 directly to theimage import block90.
• Once the image is received and stored in thework station34, the process proceeds to calibration and registration atblock92. First, atdecision block94, it is determined whether theimaging device12 has been calibrated, if so, the empty image calibration information fromblock76 is provided for calibration registration atblock92. The empty image calibration information fromblock76 is used to correct image distortion by establishing projective transformations using known calibration marker locations (seeFIGS. 2aand2b).Calibration registration92 also requires tracking of thedynamic reference frame54. In this regard, it is first determined atdecision block96 whether or not the dynamic reference frame is visible, viablock98. With thedynamic reference frame54 visible or in the navigation field and the calibration information provided, thework station34 and thecoil array controller48, via thenavigation probe interface50 performs thecalibration registration92 functions. In addition to monitoring thedynamic reference frame54, the fiducial array orlandmarks60 may also be used for image registration.
• Once thenavigation system10 has been calibrated and registered, navigation of an instrument, such as thecatheter52 is performed. In this regard, once it is determined atdecision block100 that thecatheter54 is visible or in the navigation field atblock102, an icon representing thecatheter52 is superimposed over the pre-acquired images atblock104. Should it be determined to match the superimposed image of thecatheter52 with the motion of the heart atdecision block106, ECG gating atblock108 is performed. Thecatheter52 may then be navigated, vianavigation block110 throughout the anatomical area of interest in thepatient14.
• The ECG gating atblocks86 and108 will now be fully described with respect toFIGS. 4-7. The ECG gating signals generated byblocks86 and108 may use different characteristics of the ECG signal to generate gating signal, and may include the use of an R-wave detector112 as shown inFIG. 4, or adiastole detector140 as shown inFIGS. 5 and 6. In addition, the ECG gating signals generate atblocks86 and108 may include the use of an onset R-wave detector as shown in FIG.7. Each of these detectors for ECG gating atblocks86 and108 will now be described in greater detail.
• As discussed above, the ECG gating performed atblocks86 and108 may include an R-wave detector112 as illustrated inFIG. 4. The R-wave detector112 has two phases: alearning phase114 and adetection phase116. In this regard, the threshold characteristics associated with the ECG signals from the patient are initially acquired during thelearning phase114. Once thelearning phase114 has been completed, thedetection phase116 associated with the R-wave detector112 is performed which generates a gating signal by comparing the characteristics of the current ECG signal to the thresholds calculated during thelearning phase114.
• As shown inFIG. 4, thelearning phase114 of the R-wave detector112 includesblock118 in which the ECG signal is initially acquired. Once the ECG signal is acquired atblock118, thelearning phase114 calculates certain characteristics of the ECG signal atblock120 including slew, turning point and amplitude. The slew of the ECG signal is the slope of the ECG signal taken by selecting 10 samples within a 25 millisecond window. The turning point represents the running sum of 20 samples taken at a rate of 400 samples per second and represents a near term extrema of the ECG signal. The amplitude determined atblock120 is simply the amplitude of a ECG signal.
• Once the slew, turning point and amplitude of the ECG signal are calculated at theblock120, thelearning phase114 of the R-wave detector112 adds these values to a threshold database atblock122. The threshold database contains a 10 period moving average of the slew, turning point and amplitude of the ECG signals. Once the values for slew, turning point and amplitude have been added to the threshold database atblock122, thelearning phase114 determines whether the learning phase is completed atblock124 by calculating whether 10 cardiac cycles have occurred since thelearning phase114 began. If 10 cardiac cycles have occurred, then the R-wave detector112 initiates thedetection phase116. However, if fewer then 10 cardiac cycles have occurred, thelearning phase114 acquires another ECG signal atblock118.
• As discussed above, if thelearning phase114 has obtained information from 10 cardiac cycles, the R-wave detector112 then initiates thedetection phase116. As shown inFIG. 4, thedetection phase116 initially acquires the current ECG signal atblock126. After the current ECG signal is acquired atblock126, thedetection phase116 then calculates the slew, turning point and amplitude of the current ECG signal atblock128. The slew, turning point and amplitude are calculated in the same manner as discussed above with respect to block120.
• After the slew, turning point and amplitude have been calculated atblock128, thedetection phase116 then determines whether the slew of the current ECG signal is greater than a threshold atblock130. In this regard, the slew threshold may be about 0.9 times the average slew that is stored in the threshold database atblock122 during thelearning phase114. It will be understood, however, that other values for the slew threshold may be used. If the slew of the current ECG signal is greater than the threshold as determined atblock130, then thedetection phase116 determines whether the amplitude of the current ECG signal is greater than an amplitude threshold. In this regard, thedetection phase116 determines whether the amplitude of the current ECG signal is greater than about 0.9 times the average amplitude of the ECG signal stored in the threshold database atblock122 during thelearning phase114. If the amplitude of the current ECG signal is less than the amplitude threshold as compared atblock132, a new sample is acquired atblock126. However, if the amplitude of the current ECG signal is greater than the amplitude threshold as determined byblock132, then thedetection phase116 compares atblock134 the turning point of the current ECG signal to the turning point threshold. In this regard, thedetection phase116 determines whether the turning point of the current ECG signal is greater or lesser than the turning point threshold stored in the threshold database atblock122. If the turning point of the current ECG signal is less than the turning point threshold determined atblock134, then thedetection phase116 assumes that the current ECG signal does not contain an R-wave and therefore a new sample is acquired atblock126.
• However, if the turning point of the current ECG sample is greater than the turning point threshold as determined atblock134, then thedetection phase116 assumes that the ECG signal contains an R-wave. When this occurs, a gating signal is generated byblock138 following a delay period from onset of the R-wave that was detected. For example, thedetection phase116 may generate a gating signal after a delay of 70% of the interval between adjacent R-waves (hereinafter the “R-R interval”). In this case, if the temporal spacing between two adjacent R-waves is 670 milliseconds, a gating signal may be generated after a delay of approximately 469 milliseconds after the R-wave that was detected. However, other delay periods may be suitable.
• As discussed above, the ECG gating atblocks86 and108 may also include the use of adiastole detector140 as illustrated inFIGS. 5 and 6. Thediastole detector140 has alearning phase142 and agating phase144. Thelearning phase142 of thediastole detector140 calculates the mean and standard deviation of the R-R interval as will be fully discussed below. Thegating phase144 of thediastole detector140 is used for confirming that a diastolic region of the ECG signal is present before causing a gating signal to be generated atblocks86 and108. Thelearning phase142 and thegating phase144 of thediastole detector140 will now be described in greater detail.
• In thelearning phase142 of thediastole detector140, the presence of an R-wave is first detected atblock146. In this regard, the R-wave detector112, as shown inFIG. 4, may be used for detecting the presence of an R-wave. However, other suitable R-wave detectors may be used. After the R-wave is detected atblock146, the time interval between the current R-wave and immediately proceeding R-wave is calculated atblock148. After the R-R interval has been calculated atblock148, thelearning phase142 determines whether the R-R interval is too short at block150 (e.g., when arrhythmias may have occurred). In one embodiment, the R-R interval may be too short if the R-R interval is less than about 300-350 milliseconds. If the R-R interval is too short as determined byblock150, thelearning phase142 then waits until the next R-wave occurs as indicated byblock146. If the R-R interval is sufficiently long as determined byblock150, thelearning phase142 then adds the R-R interval as well as the slew to the interval database atblock152. Once the R-R interval is added to the interval database, thelearning phase142 then calculates the mean and standard deviation of the R-R intervals stored in the database, as well as determines the minimum slew of the slew data of the ECG signals that have been evaluated during thelearning phase142. After the mean and standard deviation of the R-R interval are calculated, thediastole detector140 determines whether the learning phase is complete atblock156. The learning phase may be determined to be complete after it has processed 10 cardiac cycles of sufficient length, as described above.
• Once thelearning phase156 is complete, the gating phase of thediastole detector140 is initiated. In this regard, thegating phase144 initially determines the location of a diastolic detection window. The diastolic detection window is the region of the ECG signal in which the heart is believed to be in diastole, and in which ECG signals are evaluated to confirm the heart is in diastole. The width of the diastolic detection window may be about 75 milliseconds, though other suitable widths may be used. The location of the diastolic detection window with respect to the current ECG signal may be determined by the variation of the R-R interval calculated during thelearning phase142. In this regard, if there is a relatively high standard deviation in the R-R interval as calculated atblock154, there is a relatively high likelihood of that the ECG signal may contain arrhythmias or ectopic beats. Under these circumstances, it may be desirable to center the diastolic detection window at approximately 45% of the R-R interval following the onset of an R-wave. In contrast, if the standard deviation of the R-R interval calculated atblock154 is relatively small, then it is likely that the ECG signal corresponds to normal sinus rhythms. In this case, the diastolic detection window may be centered later in the cardiac cycle, such as at 70% (or about 62% to about 80%) of the duration R-R interval following the detection of an R-wave. It is to be understood, however, that the diastolic detection window may be centered at other suitable locations.
• After the location of the diastolic detection window is determined at158, thegating phase144 detects the presence of an R-wave block160 (such as by using the R-wave detector112). Once an R-wave is detected atblock160, the current ECG signals located in the diastolic detection window are recorded during the diastolic detection window by waiting until the diastolic detection window opens by means ofblocks162 and164. Once the diastolic detection window has opened, thegating phase144 determines whether an R-wave has occurred within the diastolic detection window atblock166. This may be performed using the R-wave detector112 shown inFIG. 4, though other suitable R-wave detectors may be used. If an R-wave has occurred during the diastolic detection window, thegating phase144 may prevent the generation of a gating signal atblocks86 and108 by waiting until the occurrence of the next R-wave as indicated byblock160. If no R-wave has been detected during the diastolic detection window as determined byblock166, then thegating phase144 may determine whether the slew associated with the current ECG signal is relatively high. In this regard, thegating phase144 may select 30 samples (at a rate of 400 samples per second) and determine whether the slew is greater than 5 times the minimum slew as calculated atblock154. If the slew of the ECG signal is sufficiently high, thegating phase144 may not cause the generation of a gating signal fromblocks86 and108 but waits until the next R-wave is detected atblock160.
• If the slew of the current ECG signal is not high as determined atblock168, thegating phase144 may determine whether there is a DC offset associated with the current ECG signal. If there is a DC offset to the current ECG signal, then thegating phase144 may also not cause the generation of a gating signal atblocks86 and108 but waits until another R-wave is detected atblock160. If there is no DC offset, then thegating phase144 may trigger the generation of a gating signal atblocks86 and108 as indicated byblock172.
• It will be appreciated that the check for DC offset atblock170 may occur during normal sinus rhythms and may not generally be necessary when arrhythmias may be present. In addition, also during normal sinus rhythms, once a gating signal is generated byblocks86 and108, thegating phase144 may prevent the generation of another gating signal fromblocks86 and108 for a period of time (such as, for example, 70% of the R-R interval following the next R-wave).
• As discussed above, the ECG gating atblocks86 and108 can also include an onset R-wave detector174 as illustrated inFIG. 7. The onset R-wave detector174 is used for sensing the onset of an R-wave during a cardiac cycle, and causing the navigation system to display the previously acquired image of the catheter when the heart was in diastole. As indicated byblock176, the onset R-wave detector174 initially acquires the ECG signal as well as the catheter image. Once the ECG signal and catheter image has been acquired atblock176, the onset R-wave detector174 may calculate the slew and amplitude characteristics of the ECG signal atblock178. In addition, the onset R-wave detector174 may store the catheter image in a frame buffer atblock180. If the slew or the amplitude of the ECG signal exceed respectively thresholds (as determined byblocks182 and184), the onset R-wave detector174 determines that R-wave onset has occurred and, therefore, retrieves the previous catheter image from the frame buffer for use to register the image of the catheter as illustrated byblock186. If either of the slew or the amplitude are not greater than their respective thresholds as determined byblock182 and184, then the current image is used for purposes of registration and a new ECG signal and catheter image are then obtained atblock176.
• The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.

Claims (25)

1. An image guided navigation system for guiding an instrument through a region of a patient, said image guided navigation system comprising:

an anatomical gating device operable to sense a first physiological event and a second physiological event, the first physiological event being different from the second physiological event;

an imaging device operable to capture image data of the region of the patient in response to the second physiological event by comparing one characteristic of the first physiological event with respect a first threshold and when a second characteristic of said second physiological event to a second threshold;

a tracking device operable to track the position of the instrument in the region of the patient;

a controller in communication with said anatomical gating device, said imaging device and said tracking device and operable to register said image data with the region of the patient in response to the first and second physiological events, said controller further operable to superimpose an icon representing the instrument onto the image data of the region of the patient based upon the position tracked by said tracking device; and

a display operable to display the image data of the region of the patient with the superimposed icon of the instrument.

2. The image guided navigation system for guiding an instrument through a region of a patient as set forth inclaim 1, wherein the first physiological event is the generation of an R-wave during a cardiac cycle and the second physiological event is diastole during a cardiac cycle.

3. The image guided navigation system for guiding an instrument through a region of a patient as set forth inclaim 2, the anatomical gating device generates a diastolic detection window for confirming whether the patient is in diastole before capturing image data.

4. The image guided navigation system for guiding an instrument through a region of a patient as set forth inclaim 3, wherein the anatomical gating device is operable to confirm diastole during the diastolic detection window by comparing at least one characteristic of the ECG signal to one previously stored characteristic being selected from the group consisting of the presence of an R-wave, slew and DC offset.

5. The image guided navigation system for guiding an instrument through a region of a patient as set forth inclaim 3, wherein the diastolic detection window extends from about 62% to about 80% of the duration of the R-R interval following the detection of an R-wave.

6. The image guided navigation system for guiding an instrument through a region of a patient as set forth inclaim 3, wherein the diastolic detection window is centered at about 70% of the duration of the R-R interval following the detection of an R-wave during normal sinus rhythms.

7. The image guided navigation system for guiding an instrument through a region of a patient as set forth inclaim 3, wherein the diastolic detection window is centered at about 45% of the duration of the R-R interval following R-wave detection during arrhythmias.

8. The image guided navigation system for guiding an instrument through a region of a patient as set forth inclaim 1, wherein the first physiological event is associated with the presence of an R-wave of an ECG signal, the anatomical gating device operable to determine the presence of an R-wave by comparing at least one characteristic of the ECG signal to at least one corresponding threshold, the at least one characteristic selected from the group consisting of slew, turning point and amplitude.

9. The image guided navigation system for guiding an instrument through a region of a patient as set forth inclaim 1, wherein the anatomical gating device is operable to detect the onset of systole by calculating slew, amplitude and turning point of an ECG signal to determine the presence of an R-wave in the ECG signal, and generate a diastolic detection window in response to the variability of the interval between adjacent R-waves in the ECG signal.

10. The image guided navigation system as defined inclaim 1 wherein said imaging device is selected from a group of 2D, 3D or 4D imaging devices comprising a C-arm fluoroscopic imager, a magnetic resonance imager (MRI), a computed tomography (CT) imager, a positron emission tomography (PET) imager, an isocentric fluoroscopy imager, a bi-plane fluoroscopy imager, an ultrasound imager, a multi-slice computed tomography (MSCT) imager, positron emission tomography-computed tomography (PET/CT), high definition computed tomography (HDCT), dual source computed tomography, a high-frequency ultrasound (HIFU) imager, an optical coherence tomography (OCT) imager, an intra-vascular ultrasound imager (IVUS), an ultrasound imager, an intra-operative CT imager, an intra-operative MRI imager, a single photon emission computer tomography (SPECT) imager, and a combination thereof.

11. The image guided navigation system as defined inclaim 1, wherein said instrument is operable to deliver a therapy to the patient, the therapy is selected from a group comprising lead placement, drug delivery, gene delivery, cell delivery, ablation, mitral valve repair, aortic valve repair, leadless pacemaker placement, leadless pressure sensor placement, and a combination thereof.

12. The image guided navigation system as defined inclaim 1, wherein said instrument is selected from a group comprising a catheter, a guide wire, a stylet, an insert, a needle and a combination thereof.

13. Method for image guiding an instrument in a region of a patient, the method comprising:

identifying a first physiological event;

comparing at least one characteristic of the first physiological event to a first predetermined threshold;

identifying a second physiological event different from the first physiological event;

comparing at least one characteristic of the second physiological event to a second predetermined threshold;

capturing image data during the second physiological event when the at least one characteristic of the first physiological event exceeds the first threshold and when the at least one characteristic of the second physiological event exceeds the second threshold;

registering the captured image data to the patient during the second physiological event; and

displaying the location of the instrument on the image data of the region of the patient by superimposing an icon of the instrument on the image data.

14. The method for guiding an instrument to a region of a patient as set forth inclaim 13, wherein the identification of a first physiological event is the identification of an R-wave during a cardiac cycle.

15. The method for guiding an instrument to a region of a patient as set forth inclaim 14, wherein identifying a second physiological event is the identification of diastole during a cardiac cycle.

16. The method for guiding an instrument to a region of a patient as set forth inclaim 15, wherein the identification of an R-wave during a cardiac cycle includes comparing at least one characteristic of an ECG signal to a corresponding threshold, the at least one characteristic selected from the group consisting of slew, turning point and amplitude.

17. The method for guiding an instrument to a region of a patient as set forth inclaim 15, wherein the identification of diastole during the cardiac cycle includes comparing at least one characteristic of an ECG signal to a previously stored characteristic selected from the group consisting of the presence of an R-wave, slew and DC offset.

18. A method for image guiding an instrument in a region of a patient, said method comprising:

generating a gating signal from an anatomical gating device, the gating signal responsive to the presence of arrhythmias and ectopic beats;

capturing image data during diastole in response to the gating signal generated by the anatomical gating device;

registering the captured image data to the patient; and

displaying the location of the instrument on the image data of the region of the patient by superimaging an icon of the instrument on the image data.

19. The method for image guiding an instrument in a region of a patient as set forth inclaim 18, further comprising detecting at the onset of systole by calculating slew, amplitude and turning point of an ECG signal to determine the presence of an R-wave in the ECG signal, and generating a diastolic detection window in response to the variability of the interval between adjacent R-waves in the ECG signal.

20. The method for image guiding an instrument in a region of a patient as set forth inclaim 19, wherein generating a diastolic detection window includes comparing the turning point of the ECG signal to a predetermined threshold.

21. The method for image guiding an instrument in a region of a patient as set forth inclaim 19, wherein generating a diastolic detection window includes comparing the amplitude of the ECG signal to a predetermined threshold.

22. The method for image guiding an instrument in a region of a patient as set forth inclaim 20, wherein the diastolic detection window is centered at about 45% to about 70% of the duration of the R-R interval following the onset of an R-wave.

23. The method for image guiding an instrument in a region of a patient as set forth inclaim 20, wherein the width of the diastolic detection window is about 75 milliseconds.

24. The method for image guiding an instrument in a region of a patient as set forth inclaim 18, wherein generating a gating signal from the anatomical gating device includes determining whether the onset of an R-wave has occurred.

25. The method for image guiding an instrument in a region of a patient as set forth inclaim 24, wherein displaying the location of the instrument on the image data includes displaying a previously acquired image of the instrument when the onset of an R-wave has occurred.

Images