Abstract:
A method for planning left atrial appendage (LAA) occlusion for a patient includes obtaining acquisition data from a medical imaging system, and generating a 3D model of the left atrium of the patient. One or more left atrial anatomical landmarks are identified on the 3D model, and saved views of the 3D model are registered on an interventional system. One or more of the registered saved views are visualized with the interventional system.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present disclosure relates generally to cardiac implant systems and, more particularly, to a cardiac imaging system and method for planning isolation of the left atrial appendage of the heart.  
           [0002]    Atrial fibrillation (AF) is an arrhythmia in which the atria (upper chambers of the heart) stop contracting properly as they fibrillate, and is the most common of heart rhythm irregularities. It is estimated that over 2.2 million Americans have been diagnosed with AF, with over 140,000 new cases being diagnosed each year. Patients with AF have a high risk of stroke, and about 15 percent of all strokes occur in people with atrial fibrillation. Each year, about 600,000 Americans suffer a new or recurrent stroke. In 1991, the Framingham study showed that a diagnosis of AF increased the risk of stroke 3 to 5 times higher, rising from 1.5% in the fifth decade of life to over 23% by the eighth decade.  
           [0003]    More specifically, previous studies indicate that more than 90 percent of nonrheumatic AF-related strokes result from a blood clot that forms in the left atrial appendage (LAA), a small, thumb-shaped pouch in the heart&#39;s left upper chamber. Such clots can block a blood vessel leading to the brain, thereby causing a stroke. Several large randomized trials have shown the efficacy of warfarin, a blood thinner, in reducing the risk of stroke. In clinical practice, however, in over 40 percent of patients the drug is contraindicated or cannot be used because of the side effects, such as bleeding. Another approach to treating AF is a surgical intervention, such as the Maze procedure, in which strategic placement of incisions in both atria stops the formation and the conduction of errant electrical impulses. The maze procedure channels the normal electrical impulse to travel in one direction from the top of the heart to the bottom by producing a scar tissue that permanently blocks the travel routes of the electrical impulses that cause AF, thus eradicating the arrhythmia. In such procedures, the LAA is routinely removed, as recommended in the American College of Cardiology-American Heart Association guidelines.  
           [0004]    Recently, in order to provide still an alternative strategy for preventing stroke, minimally invasive techniques involving deliberate occlusion of the LM are being implemented. In particular, a catheter is used to place a blocking device at the mouth of the LAA. The blocking device is a self-expanding metal cage of nitinol that pops open as the metal warms up inside the body. The cage is covered with a membrane, which blocks the atrial appendage and allows normal tissue to grow into the device. In one study of this procedure, called PLAATO (percutaneous left atrial appendage transcatheter occlusion), the patients&#39; implants ranged in diameter from 18 to 32 millimeters with the average procedure time being 92.7 minutes. However, in 25% of those patients, the initial device was removed and replaced with one of a different size. As such, there is a need for an improved system and method for determining an effective roadmap for LAA anatomy and, where appropriate, a roadmap for effective LAA isolation and/or occlusion.  
         SUMMARY OF THE INVENTION  
         [0005]    The above discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by a method for planning left atrial appendage (LM) occlusion for a patient. In an exemplary embodiment, the method includes obtaining non-invasive acquisition data from a medical imaging system, and generating a 3D model of the left atrium of the patient. One or more left atrial anatomical landmarks are identified on the 3D model, and saved views of the 3D model are registered on an interventional system. One or more of the registered saved views are visualized with the interventional system.  
           [0006]    In another aspect, a method for planning left atrial appendage (LAA) occlusion for a patient includes obtaining acquisition data from a medical imaging system using a protocol directed toward the left atrium. The acquisition data is segmented using a 3D protocol so as to visualize the left atrium, including the LAA. A 3D model of the left atrium of the patient is generated, and one or more left atrial anatomical landmarks on the 3D model are identified. Saved views of the 3D model are registered on an interventional system, and one or more of the registered saved views are visualized on the interventional system. The orientation and size of the LM, as well as any anomalies associated therewith, are identified from the 3D model.  
           [0007]    In still another aspect, a method for planning left atrial appendage (LAA) occlusion for a patient includes obtaining acquisition data from a cardiac imaging system such as computed tomography (CT) scanner using a protocol directed toward the left atrium. The acquisition data are segmented using a 3D protocol so as to visualize the left atrium, including the LAA. A 3D model of the left atrium of the patient is generated, and one or more left atrial anatomical landmarks on the 3D model are identified. Saved views of the 3D model are registered on a fluoroscopy system, and one or more of the registered saved views are visualized with the fluoroscopy system. The orientation and size of the LAA, as well as any anomalies associated therewith, are identified from the 3D model.  
           [0008]    In still another aspect, a system for planning left atrial appendage (LAA) occlusion for a patient includes a medical imaging system for generating non-invasive acquisition data, and an image generation subsystem for receiving the acquisition data and generating one or more images of the left atrium of the patient. An operator console or post-processing device is configured for identifying one or more left atrial anatomical landmarks on the one or more images. The workstation includes post processing software for saving views of the 3D model that can be registered on an interventional system. The interventional system is configured for visualizing one or more of the registered saved views therewith and identifying the orientation and size of the LAA.  
           [0009]    In still another aspect, a system for planning left atrial appendage occlusion for a patient includes a cardiac computed tomography (CT) imaging system for generating acquisition data, the CT imaging system using a protocol directed toward the left atrium. An image generation subsystem receives the acquisition data and generates one or more images of the left atrium of the patient. The image generation system is further configured for segmenting the acquisition data using a 3D protocol so as to visualize the left atrium, including the LAA. An operator console is configured for identifying one or more left atrial anatomical landmarks on the one or more images, and a workstation includes post processing software for registering saved views of the 3D model on a fluoroscopy system. The fluoroscopy system is configured for visualizing one or more of the registered saved views therewith and identifying the orientation and size of the LAA. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    Referring to the exemplary drawings wherein like elements are numbered alike in the several Figures:  
         [0011]    [0011]FIG. 1 is a schematic diagram of a medical imaging system, such as a computed tomography (CT) system, suitable for planning left atrial appendage isolation, in accordance with an embodiment of the invention; and  
         [0012]    [0012]FIG. 2 is a flow diagram of a method for planning left atrial appendage isolation, in accordance with a further embodiment of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0013]    Disclosed herein is a cardiac computed tomography (CT) system and method for LAA isolation/occlusion that provides information for planning interventional procedures that enable an electrophysiologist, cardiologist and/or surgeon to plan in advance a desired approach to take for the procedure. Additionally, with a more detailed three-dimensional (3D) geometrical representation of the LM, as may be obtained from imaging modalities such as CT, magnetic resonance (MR) and ultrasound, the practitioner can identify the orientation, size and any anomalies of the LM. Thus, a device or implant of the correct size may be selected during planning so as to avoid the problem of incorrectly sized implants encountered with this procedure. The 3D images obtained may also be used to plan for isolation of LAA from outside (i.e., epicardially).  
         [0014]    Although the exemplary embodiments illustrated hereinafter are described in the context of a CT imaging system, it will be appreciated that other imaging systems known in the art are also contemplated with regard to planning LM isolation/occlusion.  
         [0015]    Referring initially to FIG. 1, there is shown an overview of an exemplary cardiac computed tomography (CT) system.  100  with support for cardiac imaging. Again, it should be understood that the cardiac CT system  100  is presented by way of example only, since other imaging systems known in the art (e.g., magnetic resonance, ultrasound) may also be used in an embodiment of the present invention. A scanner portion  102  of the system  100  includes an electrocardiographic (EKG) monitor  104  that outputs R-peak events into a scanner  106  through a scanner interface board  108 . A suitable example of a scanner interface board  108  is a Gantry interface board that can be used to couple an EKG system to the scanner. The cardiac CT subsystem defined by scanner portion  102  utilizes EKG-gated acquisition or image reconstruction capabilities to image the heart free of motion in its diastolic phase, as well as in multiple phases of systole and early diastole.  
         [0016]    Data is outputted from the scanner portion  102  into a subsystem  110  that includes software for performing data acquisition, data control and image generation. In addition, data that is outputted from the scanner  106 , including R-peak time stamps, is stored in an acquisition database  112 , Acquisition is performed according to one or more acquisition protocols that are optimized for imaging the heart and specifically the left atrium. Image generation is performed using one or more optimized 3D protocols for automated image segmentation of the CT image dataset for the inner surface of the LAA.  
         [0017]    The image data stream  114  is sent to an operator console  116 . The data used by software at the operator console  114  for exam prescription and visualization is stored in an image database  118 , along with the data from the image data stream  114 . Display screens  120  are provided to the operator of the exam prescription and visualization processes. The image data may be archived, put on film or sent over a network  122  to a workstation  124  for analysis and review, including 3D post processing. The post processing software depicted in the workstation  124  provides “immersible” views of the ostium of the LM and body of the LAA, which can be visualized from the inside. These special views can be saved and viewed by the practitioner.  
         [0018]    The 3D protocols of the post processing software enable the software to provide the certain quantitative features of the LM, such as contour, position orientation and dimensions (e.g., circumference) of the atrium at different distances from the end of appendage, as well as between the ostia, LAA and pulmonary veins. These features may be provided automatically or semi-automatically with user input and interaction, and saved into 3D rendering files  126  for use by the practitioner for interventional planning and procedure. The post processing software also provides for the export of detailed 3D models  128  of the left atrium and LM. The 3D models  128  (which may be viewed on display screen  132  associated with workstation  124 ) are configured to include geometric markers inserted into the volume at landmarks of interest such that the left atrium and the LAA are visualized in a translucent fashion with the opaque geometric landmarks.  
         [0019]    In addition, the 3D models  128  may be exported in any of several formats, including but not limited to: a wire mesh geometric model, a set of surface contours, a segmented volume of binary images, and a DICOM (Digital Imaging and Communications in Medicine) object using the radiation therapy (RT) DICOM object standard or similar object. Other formats known in the art can also be used to store and export the 3D models  128 .  
         [0020]    Referring now to FIG. 2, there is shown a flow diagram  200  illustrating a method for planning LAA isolation, in accordance with a further embodiment of the invention. Beginning at block  202 , a volume of data is initially acquired on the cardiac CT system, using a protocol that is preferably optimized for the left atrium (LA) region of the heart. At block  204 , the image dataset is segmented with post-processing software using a 3D protocol preferably optimized for the LA and designed to extract the surfaces of the heart chambers, including the. LA. Automated procedures may be employed, where appropriate, with or without queues from the operator (e.g., location of anteroposterior, left anterior oblique, posterolateral, oblique and right anterior oblique views).  
         [0021]    Then, as shown in block  206 , the LM is visualized using 3D surface and/or volume rendering to create 3D models of the LAA, which also preferably include an immersible view (i.e., a view from the inside the chamber). In this manner, the ostial size and contour of the LAA may be measured, as is illustrated at block  208 . As shown in block  210 , explicit geometric markers are inserted into the volume at landmarks of interest, wherein the markers may be subsequently visualized in a translucent fashion. Then, as illustrated at block  212 , specific 3D renderings and axial images (such as DICOM images, video clips, films, multimedia formats, etc.) are saved as desired for subsequent visual reference during the interventional planning and for use during the interventional procedure. The saved views are then exported and registered with the projection image on the fluoroscopy system or alternatively, with the tomosynthesis images of the 3D fluoroscopy system, as shown in block  214 .  
         [0022]    The interventional system is accessed and the imported registered models therewith are visualized by the practitioner, as shown in block  216 . Finally, at block  218 , the practitioner identifies the orientation, size and any anomalies of the LM such that a device or implant of the appropriate size can be selected and implanted within the LAA. It will be appreciated that automatic techniques may be employed to perform any of the above steps by using one or more of the several computer-assisted detection, localization and visualization methods available. Moreover, these methods could be completely automatic when the procedure and the organ of interest is specified or partly interactive with input from the user.  
         [0023]    It will further be appreciated that through the use of the above described method and system embodiments, the planning of LAA occlusion is improved in that the imaging information generated and registered allows for an appropriately tailored approach to the interventional/procedure. In choosing the appropriate approach, the duration of the procedure itself is reduced and any unnecessary procedures are also eliminated. More particularly, a detailed 3D geometric representation of the LAA wall increases the precision of the isolation/occlusion procedure by providing the contour, position orientation and dimensions (e.g., circumference) of the atrium at different distances from the end of appendage, as well as between the ostia, LM and pulmonary veins. These features may be further provided automatically or semi-automatically with user input and interaction.  
         [0024]    While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.