Abstract:
A method for associating EKG waveform data with computed tomography image data using a data synchronization scheme including generating the EKG waveform data using an electrocardiogram device, operating a computed tomography imaging system so as to create the computed tomography image data, communicating an exposure marker-in signal to the electrocardiogram device such that the exposure marker-in signal is associated with the EKG waveform data and processing the computed tomography image data, the EKG waveform data and the exposure marker-in signal, so as to correlate the EKG waveform data with the computed tomography image data. Also claimed is a medium encoded with a machine-readable computer program code for associating EKG waveform data with image data generated by an imaging system using a data synchronization scheme, the medium including instructions for causing controller to implement the aforementioned method.

Description:
BACKGROUND OF INVENTION 
     This invention relates generally to a method and system for synchronizing multiple data signals and more particularly to a method and system for synchronizing an EKG waveform generated via an electrocardiogram (EKG) with an x-ray image generated via a computed tomography (CT) imaging system. 
     In many cardiac applications, it is desirable to have the ability to display a CT image of a patients&#39; heart along with a simultaneously generated patient EKG waveform. This would allow a physician or technician to visually observe the physical condition of the patients&#39; heart while simultaneously observing the cardiac electrical function of a patient. However, if the heart is moving or beating (cardiac motion) during the scanning process, the CT projection data may include motion artifacts and other noises making accurate reconstruction of the CT image more difficult, or in some cases impossible. 
     One technique currently available to reduce the effect of cardiac motion is to synchronize the CT imaging system with the patient heart cycle so that the CT scans only occur between heart beats. In order to accomplish this task, current cardiac scanning techniques synchronize a patient CT scan with the electrical heart cycle of the patient via an EKG monitoring device communicated with a CT imaging system. Referring to  FIG. 1 , an example of a patient EKG waveform  100  is shown and includes an R-Peak  102  and an exposure indicator  104 , wherein exposure indicator  104  identifies the period in EKG waveform  100  where the CT scan and thus patient exposure occurs. As can be seen, exposure indicator  104  is disposed between heartbeats indicating that the CT scan occurred while the patients&#39; heart was resting. 
     One problem with this technique is that, although most EKG monitoring devices provide a means to read EKG waveform data as it is being collected, most CT imaging systems do not. As a result, a delay in time occurs between the collection of the EKG data and the collection of the CT projection data making accurate correlation between the EKG data and the CT projection data extremely difficult or impossible. Therefore, there is a need for a method that facilitates the correlation of EKG data and CT projection data, wherein the method utilizes existing CT imaging systems and EKG monitoring devices and wherein the method does not significantly increase the data collection time. 
     SUMMARY OF INVENTION 
     The above discussed and other drawbacks and deficiencies are overcome or alleviated by a method for associating EKG waveform data with computed tomography image data using a data synchronization scheme comprising: generating the EKG waveform data using an electrocardiogram device; operating a computed tomography imaging system so as to create the computed tomography image data; communicating an exposure marker-in signal to the electrocardiogram device such that the exposure marker-in signal is associated with the EKG waveform data; and processing the computed tomography image data, the EKG waveform data and the exposure marker-in signal, so as to correlate the EKG waveform data with the computed tomography image data. 
     A medium encoded with a machine-readable computer program code for associating EKG waveform data with computed tomography image data using a data synchronization scheme, the medium including instructions for causing a controller to implement a method comprising: generating the EKG waveform data using an electrocardiogram device; operating a computed tomography imaging system so as to create the computed tomography image data; communicating an exposure marker-in signal to the electrocardiogram device such that the exposure marker-in signal is associated with the EKG waveform data; and processing the computed tomography image data, the EKG waveform data and the exposure marker-in signal, so as to correlate the EKG waveform data with the computer tomography image data. 
     A method for associating EKG waveform data with image data generated by an imaging system using a data synchronization scheme comprising: obtaining the imaging system, an electrocardiogram device and an object to be examined; associating the object with the imaging system and the electrocardiogram device; and processing the image data and the EKG waveform data using the data synchronization scheme wherein the data synchronization scheme, generates the EKG waveform data using an electrocardiogram device; operates the imaging system so as to create the image data; communicates an exposure marker-in signal to the electrocardiogram device such that the exposure marker-in signal is associated with the EKG waveform data; and processes the image data, the EKG waveform data and the exposure marker-in signal, so as to correlate the EKG waveform data with the image data. 
     A system for associating EKG waveform data with computed tomography image data using a data synchronization scheme comprising: a gantry having an x-ray source and a radiation detector array, wherein the gantry defines an object cavity and wherein the x-ray source and the radiation detector array are rotatingly associated with the gantry so as to be separated by the object cavity; an object support structure movingly associated with the gantry so as to allow communication with the object cavity; and a processing device having the data synchronization scheme, wherein the data synchronization scheme, generates the EKG waveform data using an electrocardiogram device; operates a computed tomography imaging system so as to create the computed tomography image data; communicates an exposure marker-in signal to the electrocardiogram device such that the exposure marker-in signal is associated with the EKG waveform data; and processes the computed tomography image data, the EKG waveform data and the exposure marker-in signal, so as to correlate the EKG waveform data with the computer tomography image data. 
     A system for associating EKG waveform data with image data using a data synchronization scheme comprising: an imaging system; an object disposed so as to be communicated with the imaging system, wherein the imaging system generates image data responsive to the object; and a processing device having the data synchronization scheme, wherein the data synchronization scheme, generates the EKG waveform data using an electrocardiogram device; operates the imaging system so as to create the image data; communicates an exposure marker-in signal to the electrocardiogram device such that the exposure marker-in signal is associated with the EKG waveform data; and processes the image data, the EKG waveform data and the exposure marker-in signal, so as to correlate the EKG waveform data with the image data. 
     The above discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Referring to the exemplary drawings wherein like elements are numbered alike in the several Figures: 
         FIG. 1  is an example of an EKG waveform illustrating the timing between a CT exposure and a patient cardiac rhythm; 
         FIG. 2  is a perspective view of an EKG monitoring device communicated with a CT imaging system; 
         FIG. 3  is a block schematic diagram of a CT imaging system communicated with an EKG monitoring device; 
         FIG. 4  is an example of an EKG waveform illustrating the synchronization timing between a CT exposure and a patient cardiac rhythm, in accordance with an exemplary embodiment; and 
         FIG. 5  is a flow diagram describing a method for synchronizing an EKG waveform with a CT image, in accordance with an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In accordance with an exemplary embodiment, while a method and system for synchronizing EKG waveform data with an x-ray image is described and discussed hereinbelow with reference to a computed tomography (CT) imaging system, it should be understood that the method and system of the invention may be applied to other imaging systems, such as Magnetic Resonance Imaging (MRI) and/or Positron Emission Tomography (PET). 
     Referring to  FIG. 2  and  FIG. 3 , an EKG monitoring device  2  and a CT imaging system  4  is shown, wherein EKG monitoring device  2  is communicated with CT imaging system  4 . EKG monitoring device  2  includes an EKG output  6 , an EKG sync marker input  8 , an EKG data transfer device  10  and a plurality of EKG input leads  12 , wherein EKG monitoring device  2  is communicated with a patient  14  via EKG input leads  12  and wherein EKG monitoring device  2  is communicated with CT imaging system  4  via EKG data transfer device  10 . 
     CT imaging system  4  includes a gantry  16  having an x-ray source  18 , a radiation detector array  20 , a patient support structure  22  and a patient cavity  24 , wherein x-ray source  18  and radiation detector array  20  are opposingly disposed so as to be separated by patient cavity  24  and wherein radiation detector array  20  includes a plurality of detector elements  26 . X-ray source  18  and radiation detector array  20  are rotatingly disposed relative to gantry  16  and patient support structure  22 , so as to allow x-ray source  18  and radiation detector array  20  to rotate around patient support structure  22  when patient support structure  22  is disposed within patient cavity  24 . X-ray source  18  and radiation detector array  20  are communicated with a control mechanism  28  associated with CT imaging system  4 . 
     Control mechanism  28  controls the rotation and operation of x-ray source  18  and radiation detector array  20 . Control mechanism  28  includes an x-ray controller  30  communicated with x-ray source  18 , a gantry motor controller  32  communicated with gantry  16 , and a data acquisition system (DAS)  34  communicated with radiation detector array  20 , wherein x-ray controller  30  provides power and timing signals to x-ray source  18 , gantry motor controller  32  controls the rotational speed and angular position of x-ray source  18  and radiation detector array  20  and DAS  34  receives electrical signal data produced by detector elements  26  and converts this data into digital signals for subsequent processing. 
     CT imaging system  4  also includes an image reconstruction device  36 , a data storage device  38  and a processing device  40 , wherein processing device  40  is communicated with EKG monitoring device  2 , image reconstruction device  36 , gantry motor controller  32 , x-ray controller  30 , data storage device  38 , an input device  42  and a CT output device  44 . Moreover, CT imaging system  4  also includes a table controller  46  communicated with processing device  40  and patient support structure  22 , so as to control the position of patient support structure  22  relative to patient cavity  24 . 
     Referring to  FIG. 4 , EKG waveform data  200  is shown and includes a plurality of cardiac events having a first cardiac event  202  and a second cardiac event  204 . First cardiac event  202  includes a first atrial depolarization event  206 , a first Q event  208 , a first R-Peak event  210 , a first ventricular depolarization event  212  and a first ventricular re-polarization event  214 . Second cardiac event  204  includes a second atrial depolarization event  216 , a second Q event  218 , a second R-Peak event  220 , a second ventricular depolarization event  222  and a second ventricular re-polarization event  224 . 
     Again, referring to  FIG. 2 ,  FIG. 3  and  FIG. 4 , EKG monitoring device  2  and CT imaging system  4  are operated as discussed hereinbelow. Patient  14  is disposed on patient support structure  22  which is positioned so as to be within patient cavity  24 . EKG input leads  12  are non-movably associated with the chest area  48  of patient  14  so as to allow EKG monitoring device  2  to receive EKG waveform data  200  from patient  14 , wherein EKG waveform data  200  is responsive to the cardiac function of patient  14 . As the heart of patient  14  beats, this beat is sensed by EKG input leads  12  and communicated to EKG monitoring device  2  in the form of EKG waveform data  200 . EKG monitoring device  2  then examines EKG waveform data  200  so as to identify the occurrence of an R peak event  210 . Upon the occurrence of an R peak event  210 , EKG monitoring device  2  outputs an event signal responsive to R peak event  210 , which is communicated to EKG sync marker input  8  as an R marker-in signal  226 , so as to overlay EKG waveform data  200  and indicate the occurrence of an R peak event  210 , wherein R marker-in signal  226 , also referred to as defibrillator sync signal, is responsive to R peak event  210 . Although R marker-in signal  226  is preferably a positive impulse signal, R marker-in signal  226  may be any signal suitable to the desired end purpose. 
     CT imaging system  4  is then preferably operated so as to create CT image data. To do this, processing device  40  instructs x-ray source  18  to emit and project a collimated x-ray beam  54  toward radiation detector array  20  so as to pass through patient  14 . X-ray beam  54  passes through patient  14  so as to create an attenuated x-ray beam  56 , which is received by radiation detector array  20 . Detector elements  26  receive attenuated x-ray beam  56 , produces electrical signal data responsive to the intensity of attenuated x-ray beam  56  and communicates this electrical signal data to DAS  34 . DAS  34  then converts this electrical signal data to digital signals and communicates both the digital signals and the electrical signal data to image reconstruction device  36 , which performs high-speed image reconstruction. In order to obtain a full series of scans, gantry motor controller  32  is operated via processing device  40  so as to cause x-ray source  18  and radiation detector array  20  to rotate relative to patient  14  thus generating CT image data. 
     As CT imaging system  4  begins to operate, CT imaging system  4  generates a CT event signal herein referred to as exposure marker-in signal  228 , wherein exposure marker-in signal  228  is a negative impulse signal. Exposure marker-in signal  228  is then communicated to EKG monitoring device  2  via EKG sync marker input  8  so as to overlay EKG waveform data  200  and indicate the start of a CT scan. Although exposure marker-in signal  228  is preferably a negative impulse signal, exposure marker-in signal  228  may be any signal suitable to the desired end purpose. In addition, although exposure marker-in signal  228  is preferably generated via CT imaging system  4 , exposure marker-in signal  228  may be generated via any device and/or method suitable to the desired end purpose. 
     The EKG waveform data  200  with the R marker-in signal  226  and the exposure marker-in signal  228  overlay are then communicated to CT imaging system  4  via EKG data transfer device  10  so as to be processed and associated with the corresponding CT imaging data. Processing device  40  does this by processing the CT imaging data and EKG waveform data  200  with the R marker-in signal  226  and the exposure marker-in signal  228  overlay so as to associate the CT image data with EKG waveform data  200 . The CT image data and EKG waveform data  200  with the R marker-in signal  226  and the exposure marker-in signal  228  may then by stored via data storage device  38 . Although this data association is preferably accomplished via a “time stamping” method, this data association may be accomplished via any method, process or device suitable to the desired end purpose. 
     Referring to  FIG. 5 , a method for synchronizing EKG waveform data  200  with CT image data using a data synchronization scheme  300  is shown and discussed. In accordance with an exemplary embodiment, EKG monitoring device  2  is communicated with a patient  14  via EKG input leads  12  and EKG monitoring device  2  is operated so as to generate EKG waveform data  200  responsive to the cardiac function of patient  14 , as shown in step  302 . EKG monitoring device  2  then examines EKG waveform data  200  so as to identify an R peak event  210 . Upon the occurrence of R peak event  210 , EKG monitoring device  2  outputs an event signal which is communicated to EKG monitoring device  2  via EKG sync marker input  8  as R marker-in signal  226 . R marker-in signal  226  is then processed so as to be associated with R peak event  210 , as shown in step  304 . 
     CT imaging system  4  is then operated so as to create CT image data, as shown in step  306 . As CT imaging system  4  begins to operate, CT imaging system  4  generates exposure marker-in signal  228 , which is communicated to EKG monitoring device  2  via EKG sync marker input  8 , as shown in step  308 . Exposure marker-in signal  228  is then processed so as to be associated with the start of a CT scan. Once R marker-in signal  226  and exposure marker-in signal  228  have been associated with EKG waveform data  200 , EKG waveform data  200 , R marker-in signal  226  and exposure marker-in signal  228  are communicated to CT imaging system  4 , as shown in step  310 . Processing device  40  processes the CT image data, EKG waveform data  200 , R marker-in signal  226  and exposure marker-in signal  228 , so as to associate EKG waveform data  200  with the CT image data, as shown in step  312 . This advantageously allows matching of the CT image data with the EKG waveform data  200 . 
     In accordance with an exemplary embodiment, CT imaging system  4  determines the timing of the CT scans based off of the occurrence of an R peak event  210 . This technique advantageously allows for EKG waveform synchronization with view projections for ‘axial’ as well as ‘helical’ types of cardiac scans. Moreover, EKG waveform data  200  and the CT image data are preferably correlated as follows. Once an operator initiates a CT scan, the processing device  40  starts reading EKG waveform data  200  from EKG monitoring device  2  and records this information to a file, such as data storage device  38 . Once the CT scans are complete, processing device  40  examines EKG waveform data  200  for impulse functions within EKG waveform data  200  which signify a marker-in pulse, such as R marker-in signal  226  and exposure marker-in signal  228  (for example a positive impulse indicates an R peak event  210  and a negative impulse indicates the start of a CT scan). Since the rate of data acquisition of EKG waveform data  200  is known and exposure marker-in signal  228  is found, a simple calculation can be used to associate view projections of the CT image data with different parts of EKG waveform data  200 . 
     Data synchronization scheme  300  allows for EKG waveform data to be synchronized with CT image data, thus advantageously allowing for the simultaneous examination of a patient&#39;s physical cardiac condition as well as the patient&#39;s cardiac function. 
     In accordance with an exemplary embodiment, data synchronization scheme  300  may be applied to image data obtained by any imaging system suitable to the desired end purpose, such as Magnetic Resonance Imaging (MRI) and/or Positron Emission Tomography (PET). 
     In accordance with an exemplary embodiment, processing of  FIG. 5  may be implemented through processing device  40  operating in response to a computer program. In order to perform the prescribed functions and desired processing, as well as the computations therefore (e.g., the execution of fourier analysis algorithm(s), the control processes prescribed herein, and the like), the controller may include, but not be limited to, a processor(s), computer(s), memory, storage, register(s), timing, interrupt(s), communication interfaces, and input/output signal interfaces, as well as combinations comprising at least one of the foregoing. For example, the controller may include signal input signal filtering to enable accurate sampling and conversion or acquisitions of such signals from communications interfaces. It is also considered within the scope of the invention that the processing of  FIG. 5  may be implemented by a controller located remotely from processing device  40 . 
     As described above, the present invention can be embodied in the form of computer-implemented processes and apparatuses for practicing those processes. The present invention can also be embodied in the form of computer program code containing instructions embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, or any other computer-readable storage medium, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention. Existing systems having reprogrammable storage (e.g., flash memory) can be updated to implement the invention. The present invention can also be embodied in the form of computer program code, for example, whether stored in a storage medium, loaded into and/or executed by a computer, or transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via electromagnetic radiation, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention. When implemented on a general-purpose microprocessor, the computer program code segments configure the microprocessor to create specific logic circuits. 
     While the invention has been described with reference to an exemplary 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 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. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another.