Abstract:
An imaging and navigation system is disclosed herein. The imaging and navigation system includes a computer and an ultrasonic imaging device disposed at least partially within an ultrasound catheter. The ultrasonic imaging device is connected to the computer and is adapted to obtain a generally real time three-dimensional image. The imaging and navigation system also includes a tracking system connected to the computer. The tracking system is adapted to estimate a position of a medical instrument. The imaging and navigation system also includes a display connected to the computer. The display is adapted to depict the generally real time three-dimensional image from the ultrasonic imaging device and to graphically convey the estimated position of the medical instrument.

Description:
RELATED APPLICATIONS 
     This application claims priority to Provisional Application No. 60/938,356 filed on May 16, 2007, and is hereby incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein relates to an imaging and navigation system. 
     Atrial fibrillation is characterized by very rapid uncoordinated electrical signals in the atria of the heart resulting in a rapid and irregular heart beat. Atrial fibrillation can significantly impact a patient&#39;s quality of life producing symptoms such as shortness of breath, weakness, difficulty exercising, sweating, dizziness, and fainting. In some patients, atrial fibrillation can be associated with increased risk of stroke, heart failure, or heart muscle disease. It is known to treat atrial fibrillation using a process referred to as cardiac ablation wherein a small section of heart tissue is killed or otherwise rendered inactive thereby breaking the electrical pathways causing the fibrillation. 
     One problem with interventional procedures such as cardiac ablation is that it is difficult to precisely direct treatment to targeted anatomic regions without damaging surrounding tissue. Another problem with these procedures is that it is difficult to visualize and access appropriate anatomic regions in a minimally invasive manner such that the risk of complications and patient recovery time are minimized. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The above-mentioned shortcomings, disadvantages and problems are addressed herein which will be understood by reading and understanding the following specification. 
     In an embodiment, an imaging and navigation system includes a computer and an ultrasonic imaging device disposed at least partially within an ultrasound catheter. The ultrasonic imaging device is connected to the computer and is adapted to obtain a generally real time three-dimensional image. The imaging and navigation system also includes a tracking system connected to the computer. The tracking system is adapted to estimate a position of a medical instrument. The imaging and navigation system also includes a display connected to the computer. The display is adapted to depict the generally real time three-dimensional image from the ultrasonic imaging device and to graphically convey the estimated position of the medical instrument. 
     In another embodiment, an imaging and navigation system includes a computer and an ultrasound catheter connected to the computer. The ultrasound catheter is adapted to obtain a generally real time three-dimensional image. The ultrasound catheter system includes a transducer array disposed at least partially within a catheter housing, and a controller coupled with the transducer array. The controller is configured to control the transducer array in order to image a three-dimensional volume. The imaging and navigation system also includes an ablation control system connected to the computer and to an ablation catheter, and a tracking system connected to the computer. The tracking system is adapted to estimate a position of the ablation catheter. The imaging and navigation system also includes a display connected to the computer. The display is adapted to depict the generally real time three-dimensional image from the ultrasound catheter and to graphically convey the estimated position of the ablation catheter. 
     In another embodiment, an imaging and navigation system includes a computer and an ICE catheter connected to the computer. The ICE catheter is adapted to obtain a generally real time three-dimensional image. The ICE catheter includes a transducer array disposed at least partially within a catheter housing, and a motor coupled with the transducer array. The motor is configured to rotate the transducer array within the catheter housing in order to image a three-dimensional volume. The imaging and navigation system also includes an ablation control system connected to the computer and to an ablation catheter, and a tracking system connected to the computer. The tracking system is adapted to estimate a position and orientation of the ablation catheter. The imaging and navigation system also includes a display connected to the computer. The display is adapted to depict the generally real time three-dimensional image from the ICE catheter and to graphically convey the estimated position and orientation of the ablation catheter. 
     Various other features, objects, and advantages of the invention will be made apparent to those skilled in the art from the accompanying drawings and detailed description thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic representation of an imaging and navigation system in accordance with an embodiment; and 
         FIG. 2  is a partially cutaway schematic illustration of an ICE catheter in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments that may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical and other changes may be made without departing from the scope of the embodiments. The following detailed description is, therefore, not to be taken as limiting the scope of the invention. 
     Referring to  FIG. 1 , a system  10  is shown in accordance with one embodiment. The system  10  will hereinafter be described as an imaging and navigation system adapted for treating atrial fibrillation using an ablation procedure. The system  10  will also hereinafter be described as implementing intracardiac echocardiography (ICE) to facilitate the performance of the ablation procedure. It should, however, be appreciated that the system  10  may also be implemented to treat other medical conditions and to perform other procedures, and that the system  10  may implement alternate ultrasonic technologies in place of ICE. 
     The navigation portion of the imaging and navigation system  10  includes a tracking system  26  that is operatively connected to a plurality of tracking elements  12 ,  14  and  20 . According to one embodiment, the tracking system  26  and tracking elements  12 ,  14  and  20  implement electromagnetic (EM) tracking technology, however, alternate tracking technologies and/or tracking systems may be envisioned. The tracking element  12  is adapted for attachment to an ablation catheter  16 , and the tracking element  14  is adapted for attachment to an ICE catheter  18 . For purposes of this disclosure, a catheter is defined to include any flexible medical delivery system such as, for example, an endoscope. The tracking element  20  can be rigidly attached to an internal organ (e.g., the heart  24 ) or to the external body of the patient  22  in a conventional manner. A tracking element  20  secured to the patient&#39;s heart  24  may be referred to as a “dynamic reference” because it is adapted to move along with the heart  24 . An exemplary method of attaching the tracking element  20  to the patient&#39;s heart  24  is through a minimally invasive procedure using a dynamic reference catheter (not shown). 
     The present invention will hereinafter be described in accordance with an embodiment wherein the tracking element  20  comprises a field generator  21 , the tracking element  12  comprises one or more field sensors  13 , and the tracking element  14  comprises one or more field sensors  15 . It should, however, be appreciated that according to alternate embodiments the tracking element  20  may include a field sensor and the tracking elements  12 ,  14  may include field generators. The field generator  21  generates a magnetic field  25  in an area that includes the target site (e.g., the patient&#39;s heart  24 ). The field sensors  13 ,  15  are adapted to measure the magnetic field  25 , and to transmit the magnetic field measurements to the tracking system  26 . The tracking system  26  implements the magnetic field measurements to calculate the position and orientation of the tracking elements  12 ,  14 . After calculating the position and orientation of the tracking elements  12 ,  14 , the position and orientation of the ablation catheter  16  and the ICE catheter  18  respectively attached thereto can also be calculated in a known manner. 
     The tracking system  26  transmits the catheter position and orientation data to a computer  28 . The computer  28  registers the position and orientation data to an image obtained from a preoperative/intraoperative imaging device  30  and/or to an image obtained from an ICE imaging device  32 . The preoperative/intraoperative imaging system  30  may, for example, include a CT imaging device, a MR imaging device, a PET imaging device, an ultrasound imaging device, an X-ray imaging device, or any other known imaging device, as well as any combinations thereof. The preoperative/intraoperative imaging device  30  may provide 2D, 3D or 4D images. For purposes of this disclosure, 4D refers to the three primary dimensions (i.e., as measured along X, Y and Z axes) and the fourth dimension which is time. Therefore, for purposes of this disclosure, 4D is synonymous with generally real time 3D. Also for purposes of this disclosure, a generally real time image includes a maximum image delay of approximately one second. The ICE imaging device  32  is configured to obtain imaging data from the ICE catheter  18  and produce 2D, 3D or 4D images as will be described in detail hereinafter. 
     The catheter position and orientation data can be visualized on the display  34 . According to one embodiment, graphic representations corresponding to the ablation catheter  16  and the ICE catheter  18  may be virtually superimposed on a patient image obtained from the preoperative/intraoperative imaging device  30  and/or the ICE imaging device  32 . In the embodiment of  FIG. 1 , the graphic representations include the cross-hairs  46 ,  48  respectively representing the distal end portions of the ablation catheter  16  and the ICE catheter  18 , however other embodiments may include a more complete rendering showing the catheters  16 ,  18  in detail. 
     The input device  49  may include any known apparatus or system such as a keyboard, mouse, touch screen, joystick, etc., and is generally adapted to allow a user to manually input data into the system  10 . Although shown in  FIG. 1  as a separate component, the input device  49  may alternatively be incorporated into one of the other system  10  components such as the computer  28  or the display  34 . As an example, the input device  49  may include a touch screen device integrated into the design of the display  34  and adapted to facilitate surgical planning. According to one embodiment, the exemplary touch screen input device  49  could be implemented to highlight or otherwise identify specific regions of interest on a patient image obtained from one of the imaging devices  30 ,  32 . According to another embodiment, the exemplary touch screen input device  49  could be implemented to assign a priority sequence to a plurality of regions of interest. 
     A catheter control system  36  is operatively connected to both the ablation catheter  16  and the ICE catheter  18 . The catheter control system  36  is adapted to translate and steer the catheters  16 ,  18  through the patient  22  to a predefined destination at or near the patient&#39;s heart  24 . The catheter control system  36  may be configured to translate and steer the catheters  16 ,  18  in response to manual operator inputs, or may be configured to automatically direct the catheters  16 ,  18  to a selectable target site. The catheter control system  36  may also be operatively connected to and configured to control a dynamic reference catheter (not shown) adapted to facilitate the attachment of the tracking element  20  to the patient&#39;s heart  24 . 
     An ablation control system  38  controls the energy transfer to the ablation catheter  16 . Accordingly, when an operator determines that the distal end of the ablation catheter  16  is in sufficiently close proximity to a targeted cardiac region, the ablation control system  38  can be implemented to transmit a selectable amount of energy. The transmission of energy in this manner kills or otherwise renders inactive the targeted region in order to break electrical pathways causing atrial fibrillation. In a non-limiting manner, the ablation control system  38  may implement radio frequency (RF), cryogenic, ultrasound, or laser technologies. 
     One or more respiratory sensors  40  can be positioned near the patient&#39;s mouth and/or nose in order to monitor respiration, and one or more cardiac sensors  44  can be positioned near the patient&#39;s heart  24  to monitor cardiac activity. The respiratory sensors  40  and the cardiac sensors  44  are operatively associated with and adapted to transmit sensor data to a monitoring system  42 . Any sensor data collected by the monitoring system  42  is transferable to the computer  28  such that the computer  28  may be implemented to synchronize the operation of the tracking system  26 , the imaging device  30 , and/or the imaging device  32  with the patient&#39;s cardiac and respiratory activity. According to one example, the computer  28  may implement data from the monitoring system  42  to acquire images during predefined portions of a patient&#39;s cardiac or respiratory cycle. According to another example, the computer  28  may implement data from the monitoring system  42  to sequence a series of 2D images or slices in a manner that corresponds with a patient&#39;s cardiac or respiratory cycle in order to provide a generally real time rendering of a dynamic object such as the patient&#39;s heart  24 . 
     Referring to  FIG. 2 , a more detailed illustration of the ICE catheter  18  is shown. The ICE catheter  18  will hereinafter be described in detail in accordance with an embodiment. It should, however, be appreciated that the ICE catheter  18  may be replaced with a similar catheter system adapted to retain any known ultrasonic imaging device. 
     The ICE catheter  18  comprises a transducer array  50 , a motor  52 , which may be internal or external to the space-critical environment, a drive shaft  54  or other mechanical connections between motor  52  and the transducer array  50 , and an interconnect  56 . The ICE catheter  18  further includes a catheter housing  58  enclosing the transducer array  50 , motor  52 , interconnect  56  and drive shaft  54 . In the depicted embodiment, the transducer array  50  is mounted on drive shaft  54  and the transducer array  50  is rotatable with the drive shaft  54 . The rotational motion of the transducer array  50  is controlled by motor controller  60  and motor  52 . Interconnect  56  refers to, for example, cables and other connections coupling the transducer array  50  with the ICE imaging device  32  (shown in  FIG. 1 ) for use in receiving and/or transmitting signals therebetween. In an embodiment, interconnect  56  is configured to reduce its respective torque load on the transducer array  50  and motor  52 . The catheter housing  58  is of a material, size and shape adaptable for internal imaging applications and insertion into regions of interest. According to the embodiment depicted in  FIG. 2 , the catheter housing  58  is generally cylindrical defining a longitudinal axis  62 . 
     The catheter housing  58 , or at least the portion that intersects the ultrasound imaging volume, is acoustically transparent, e.g. low attenuation and scattering, acoustic impedance near that of blood and tissue (Z˜1.5M Rayl). The space between the transducer and the housing can be filled with an acoustic coupling fluid (not shown), e.g., water, with acoustic impedance and sound velocity near those of blood and tissue (Z˜1.5 M Rayl, V˜1540 m/sec). 
     According to one embodiment, the transducer array  50  is a 64-element one-dimensional array having 0.110 mm azimuth pitch, 2.5 mm elevation and 6.5 MHz center frequency. The elements of the transducer array  50  are electronically phased in order to acquire a sector image parallel to the longitudinal axis  62  of the catheter housing  58 . The transducer array  58  is mechanically rotated about the longitudinal axis  62  to image a three-dimensional volume. The transducer array  50  captures a plurality of two-dimensional images as it is being rotated. The plurality of two-dimensional images are transmitted to the ICE imaging device  32  (shown in  FIG. 1 ) which is configured to sequentially assemble the two-dimensional images in order to produce a three-dimensional image. 
     The rate at which the transducer array  50  is rotated about the longitudinal axis  62  can be regulated by the motor controller  60 . The transducer array  50  can be rotated relatively slowly to produce a 3D image, or relatively quickly to produce a generally real time 3D image (i.e., a 4D image). The motor controller  60  is also operable to vary the direction of rotation to produce an oscillatory transducer array motion. In this manner, the range of motion and imaged volume are restricted such that the transducer array  50  can focus on imaging a specific region and can update the 3D image of that region more frequently, thereby providing a generally real time 3D, or 4D, image. 
     Referring to  FIGS. 1 and 2 , an embodiment of the ICE catheter  18  includes an integrally attached tracking element  14  disposed within the catheter housing  58 . The integrally attached tracking element  14  is adapted to work in combination with the tracking element  20  and the tracking system  26  to estimate the position and/or orientation of the ICE catheter  18 . As previously described, the tracking element  14  may comprise either the field sensor  15  or a field generator (not shown) similar to the field generator  21 . 
     It should be appreciated by those skilled in the art that the previously described ICE catheter  18  is a single embodiment, and that alternate configurations may be envisioned. For example, the transducer array  50 , motor  52  and drive shaft  54  define a mechanical 4D ICE embodiment that could be replaced by a functionally equivalent electrical 4D ICE embodiment (not shown). The electrical 4D ICE embodiment may, for example, comprise a 2D matrix transducer array (not shown) integrated with an electronic device (not shown) configured to steer the ultrasound beam in azimuth and elevation. In this manner, the electrical 4D ICE embodiment could image a 3D or 4D volume without necessarily moving the transducer array. 
     While the invention has been described with reference to preferred embodiments, those skilled in the art will appreciate that certain substitutions, alterations and omissions may be made to the embodiments without departing from the spirit of the invention. Accordingly, the foregoing description is meant to be exemplary only, and should not limit the scope of the invention as set forth in the following claims.