Abstract:
For diagnosis and treatment of cardiac disease, images of the heart muscle and coronary vessels are captured using different medical imaging modalities; e.g., single photon emission computed tomography (SPECT), positron emission tomography (PET), electron-beam X-ray computed tomography (CT), magnetic resonance imaging (MRI), or ultrasound (US). For visualizing the multi-modal image data, the data is presented using a technique of volume rendering, which allows users to visually analyze both functional and anatomical cardiac data simultaneously. The display is also capable of showing additional information related to the heart muscle, such as coronary vessels. Users can interactively control the viewing angle based on the spatial distribution of the quantified cardiac phenomena or atherosclerotic lesions.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates generally to medical imaging, and more particularly to computer processing of cardiac image data for diagnosis and treatment of cardiac disease.  
         [0003]     2. Description of the Background Art  
         [0004]     Medical imaging is one of the most useful diagnostic tools available in modern medicine. Medical imaging allows medical personnel to non-intrusively look into a living body in order to detect and assess many types of injuries, diseases, conditions, etc. Medical imaging allows doctors and technicians to more easily and correctly make a diagnosis, decide on a treatment, prescribe medication, perform surgery or other treatments, etc. There are medical imaging processes of many types and for many different purposes, situations, or uses. They commonly share the ability to create an image of a bodily region of a patient, and can do so non-invasively. Examples of some common medical imaging types are nuclear medical (NM) imaging such as positron emission tomography (PET) and single photon emission computed tomography (SPECT), electron-beam X-ray computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound (US). Using these or other imaging types and associated machines, an image or series of images may be captured. Other devices may then be used to process the image in some fashion. Finally, a doctor or technician may read the image in order to provide a diagnosis.  
         [0005]     The existing displays for 3D medical imaging data acquired with different types of imaging equipment typically present three orthogonal 2D planes for two different modalities fused together. One of the benefits of presenting fused data is the ability to display anatomical and functional features simultaneously. For instance, fused CT and PET images are used in the oncological and neurological studies. Although proven to be quite useful, this technique does not allow users to view fused volumes in 3D space. They may at best see three cross-sections rather than the region of interest as a whole. Another attempt to display multi-modality fused data has been done for cardiac images acquired with SPECT or PET and computed tomography angiography (CTA). The segmented endo- and epi-cardiac surfaces of the left ventricle (LV) are used to model 3D heart images, and coronaries segmented from the CTA volumes are superimposed on the model images in 3D space. One of the important features of this approach is color-coding of the left ventricle (LV) surfaces indicating level of the cardiac muscle perfusion or viability. Another advantage for this type of display is that the user can simultaneously access LV perfusion or viability defects together with corresponding feeding coronaries. The main disadvantage of this approach is that it operates with the modeled, not actual heart images. This abstracts the heart and takes it out of anatomical context.  
       SUMMARY OF THE INVENTION  
       [0006]     In accordance with a basic aspect, a multi-modality cardiac display provides visualization of cardiac perfusion and viability defects using actual volume rendered images. At the same time the user has the ability to analyze anatomical structure of the heart and coronary vessels also rendered from the actual images and fused together.  
         [0007]     In accordance with one aspect, the invention provides a computer-implemented method including the step of obtaining cardiac image measurements of a patient from different imaging modalities to obtain volume image data of cardiac functional features from one imaging modality and volume image data of cardiac structural features from another imaging modality. The method further includes displaying, to a human user, a fused volume rendered view of the volume image data of the cardiac functional features and the volume image data of the cardiac structural features.  
         [0008]     In accordance with another aspect, the invention provides a system including a digital computer and a display coupled to the digital computer for display of image data processed by the digital computer. The digital computer is programmed for obtaining cardiac image measurements of a patient from different imaging modalities to obtain volume image data of cardiac functional features from one imaging modality and volume image data of cardiac structural features from another imaging modality. The digital computer is further programmed for controlling the display for displaying, to a human user, a fused volume rendered view of the volume image data of the cardiac functional features and the volume image data of the cardiac structural features.  
         [0009]     In accordance with still another aspect, the invention provides a system including a digital computer and a display coupled to the digital computer for display of image data processed by the digital computer. The digital computer is programmed for obtaining cardiac image measurements of a patient from a nuclear medicine (NM) scanner to obtain volume image data of cardiac perfusion and viability and obtaining cardiac image measurements of the patient from at least one of an X-ray computed tomography (CT) scanner or a magnetic resonance imaging (MR) scanner to obtain volume image data of cardiac structural features including coronary arteries. The digital computer is also programmed for automatically analyzing the volume image data of the cardiac structural features to identify the coronary arteries, and for registering the volume image data of cardiac perfusion and viability with the volume image data of the cardiac structural features. The digital computer is further programmed for controlling the display for displaying, to a human user, a fused volume rendered view of the registered volume image data of the cardiac perfusion and viability and the volume image data of the cardiac structural features, and for displaying the coronaries and the volume image data of cardiac perfusion and viability in distinctive colors in the fused volume rendered view.  
         [0010]     The above and other features and advantages of the present invention will be further understood from the following description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a block diagram of a system for medical imaging and computer-implemented diagnosis and treatment of cardiac disease;  
         [0012]      FIG. 2  shows a fused volume rendered view of a patient&#39;s heart;  
         [0013]      FIG. 3  is a flow diagram of the production of a fused volume rendered view from multi-modality image data in the system of  FIG. 1 ; and  
         [0014]      FIG. 4  shows a typical clinical workflow using the dedicated cardiac display for multi-modality data in the system of  FIG. 1 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]      FIG. 1  shows a system for medical imaging and computer-implemented diagnosis and treatment of cardiac disease. The system includes a digital computer  10  and an NMISPECT/PET scanner  11 , a CT scanner  12 , and an MRI scanner  13 . Additional scanners may be used, such as an ultra-sound (US) scanner. The computer  10  is linked to a display  14  and a keyboard  15  to provide an interface to a human user  16 . The computer includes a processor  17  and a memory  18 . The memory  18  stores a database  19  of patient cardiac tomographic data from the scanners  11 ,  12 ,  13 ; a normals database  20  of cardiac measurements of healthy patients, and a database  21  of training datasets including abnormal cardiac measurements from patients having cardiac disease. The memory  18  also stores cardiac defect classifier programs  22  for identifying cardiac defects in a patient from the patient cardiac tomographic data  19 , and a rule-based cardiac disease diagnosis and treatment program  23  for diagnosing and treating cardiac disease based on cardiac defects identified by the cardiac defect classifier programs.  
         [0016]     The cardiac defect classifier programs  22  and the cardiac disease diagnosis and treatment program  23  can be similar to widely accepted commercial software for cardiac studies in nuclear medicine, such as the Emory Cardiac Toolbox (Trademark) brand of cardiac imaging software currently being distributed by ADAC Laboratories, ELGEMS, Marconi, Medimage, Siemens Medical Systems, and Toshiba. The Emory Cardiac Toolbox (Trademark) software, for example, includes programs for quantitative perfusion analysis, gated SPECT quantitative functional analysis, 3-D display of perfusion, expert systems analysis, prognostic evaluation, automatic derivation of visual scores, generic coronary artery fusion, PET/CT actual patient coronary fusion, normal limit generation, nuclear medicine data reporting, PET data reporting, quality control of gated SPECT studies, and display of stress and rest gated studies for two-dimensional slices and three-dimensional images.  
         [0017]     In accordance with a basic aspect of the present invention, the cardiac imaging software in the memory  18  of the computer  10  includes a program  24  for fusion of multi-modal image data for presenting to the user  16  a fused volume rendered view on the display  14 .  
         [0018]     As shown in  FIG. 2 , for example, the fused volume rendered view depicts a patient&#39;s heart  25  on the screen of the display  14 . In general, when the computer  10  operates the display  14  in a dedicated multi-modality cardiac display mode, the user is presented with one to three volumetric objects in a fused volume rendered view. The display accepts three volumes: NM (PET or SPECT), CT or MRI, and segmented coronaries. The segmented coronaries object is a segmented binary mask derived from the anatomical CTA or MRA volume. Segmentation may include the entire coronary tree or its portions; i.e., calcified or volumable plaques inside coronary vessels. The transparency of each volume as well as the color-coding schema is user-adjustable. By modifying fusion ratios, the user can see fused NMICT volumes, NM/Coronaries volumes, CT/Coronaries volumes, or all three (NM/CT/Coronaries) together. Segmented coronaries are shown in a single color, or in three colors including a respective color for each one of the three major vessels (left anterior descending artery, circumflex artery, and right coronary artery). The user also is able to rotate, pan, or zoom in on the fused volumes.  
         [0019]     The input volumes can be registered and displayed in a blended fashion as given. Registration matrices can also be associated with the second or third volumes, in which case the volumes are aligned by applying the associated registration matrices prior to rendering. The registration matrix may be rigid body, affine, or a non-isotropic spatial transformation mapping corresponding voxels from different volumes to each other.  
         [0020]      FIG. 3  shows the flow of data for the production of the fused volume rendered view on the display  14 . The NM (SPECTIPET) volume  31  is comprised of three-dimensional coronary image data collected from the NM scanner  11 , and the CT/MRI volume  32  is comprised of three-dimensional coronary image data collected from the CT scanner  12  or from the MRI scanner  13 . A coronary artery feature extraction program  33  automatically identifies the voxels in the CT/MRI volume that correspond to the locations of the coronary arteries, and also identifies whether each of these voxels corresponds to the location of the right coronary artery  35  or the left anterior descending artery  36  or the circumflex artery  37 . For example, a coronary artery object  34  in the form of a segmented binary bit mask can have two bits for each voxel of the CT/MRI volume  32 , and the bits can be coded as follows: 00 binary indicates a voxel at which no coronary artery is present; 01 indicates a voxel at which the right coronary artery is present, 10 indicates a voxel at which the left anterior descending artery is present, and 11 indicates a voxel at which the circumflex artery is present.  
         [0021]     There is a respective color adjustment (C 1 , C 2 ) and a respective fusion ratio (F 1 , F 2 ) for each of the NM and CT/MRI volumes  31 ,  32 . There is also a respective fusion ratio (F 3 ) for the coronary artery object  34  and a respective color adjustment (C 3 , C 4 , C 5 ) for each of the three main coronary arteries. Default values are provided so that the coronary arteries and other features from the CT/MRI volume and features from the NM volume initially will be visible in the display, but the user may adjust these default values to emphasize or eliminate a particular one of the volumes or the coronary artery object from the fused image. For example, the user provides respective intensity adjustments (I 1 , I 2 , I 3 ). When the intensity adjustment for a particular volume or the coronary artery object exceeds a mid-range value, this will suppress the features from the other volumes or coronary artery object. In other words, the respective fusion ratio for each of the coronary artery object  34  and the volumes  31 ,  32  is determined by the intensity adjustments so that the intensity adjustments may adjust the transparency of the respective coronary artery object or features from the respective NM volume or the respective CT/MRI volume.  
         [0022]     For example, each color adjustment specifies a respective red, green, and blue value. Each intensity adjustment (I 1 , I 2 , I 3 ) scales the corresponding fusion ratio (F 1 , F 2 , F 3 ), and each fusion ratio scales the red, green, and blue values of the corresponding volume or coronary artery object. Moreover, when the user specifies an intensity adjustment for one of the volumes  31 ,  32  or the coronary artery object  34  that exceeds a mid-range value by a certain percentage, the fusion ratios for the other volumes or the coronary artery object are scaled down by this percentage. For example, each of the intensity adjustments (I 1 , I 2 , I 3 ) ranges from 0 to 1 and has a default value of 0.5, and the fusion ratios (F 1 , F 2 , F 3 ) are computed from the intensity adjustments (I 1 , I 2 , I 3 ) as follows: 
    X 1 = 1      X 2 = 1      X 3 = 1      IF (I 1 &gt;0.5) THEN X 1 =2*(1.0−I 1 )     IF (I 2 &gt;0.5) THEN X 2 =2*(1.0−I 2 )     IF (I 3 &gt;0.5) THEN X 3 =2*(1.0−I 3 )     F 1 =I 1 *X 2 *X 3      F 2 =I 2 *X 1 *X 3      F 3 =I 3 *X 1 *X 2     
 
         [0032]     A registration matrix  39  operates upon the NM volume for alignment of the voxels of the NM volume with corresponding voxels of the CT/MRI volume  32 . In the example of  FIG. 3 , the coronary arteries are inherently aligned with the CT/MRI volume  32  by the binary mask so there is no need for a registration matrix to align the coronary arteries with the CT/MRI volume. However, additional volume images could be registered and blended into the fused volume image by providing an additional registration matrix for each additional volume. For instance, segmented coronary trees can be extracted from CT angio volumes different from CT volumes used for heart rendering. In that case two registration matrices will be utilized: CTA to CT and NM to CT. For user-selected rotation, pan, and zoom, a matrix  40  operates upon the combination from the registration matrix  39  with the color and intensity adjusted values from the CT/MRI volume  32  and from the coronary artery object  34 . After adjustment by the matrix  40 , the display  14  presents the fused image data to the user as a volume rendered image.  
         [0033]     The fact that one of the input volumes is a segmented binary mask allows extended interactive features to be supported by the display. The segmented coronaries allow calculating and presenting separately coronary trees as a function of their cross-sections and orientations (e.g., a series of images showing the cross-sectional view of the vessels in the context of the cardiac tissue). A view angle exposing coronaries with most severe atherosclerotic lesions can be selected automatically or interactively. Correspondingly, a cross-section through the all fused volumes can be derived based on the local vessel orientation at the defect location.  
         [0034]     The display also can be used in a dynamic fashion if matching dynamic or gated NM, CT, or MR studies are available. In that case each phase or time bin from each of the studies is used to render a single time point of the beating heart. A series of blended volume rendered images of the heart are sequenced together and displayed with modifiable rate.  
         [0035]      FIG. 4  shows an example of clinical workflow using the dedicated cardiac display for medical multi-modality data. The color-coding scheme (C 1  in  FIG. 3 ) selected for rendering the NM based portion of the image allows the user to identify cardiac perfusion or viability defects. The coronary artery objects can be accessed for degree of stenotic defects using the same image.  
         [0036]     In a first step  101  of  FIG. 4 , for example, the user detects a SPECT left ventricle (LV) cardiac perfusion defect from the rendering of the NM based portion of the image. In step  102 , the coronary artery objects derived from the multi-slice CTA volume are assessed. In step  103 , the user rotates the displayed volume image so as to view specific coronary distributions associated with the perfusion abnormalities. In step  104 , the user scrutinizes the displayed volume image to determine whether the perfusion defect is due to a high degree of coronary stenoses. If not, then in step  105 , the user assesses regional morphological features of the left ventricle using the gated CT data. In step  106 , based on the assessment of these regional morphological features, the user decides whether the perfusion defect is due to myocardial infarction (MI).  
         [0037]     The main advantage of the clinical workflow in  FIG. 4  is the fact that cardiac and cardiac related functional and morphological data is presented simultaneously, which can potentially increase accuracy and efficiency of the human decision making process.  
         [0038]     While the invention has been described in detail above, the invention is not intended to be limited to the specific embodiments as described. It is evident that those skilled in the art may now make numerous uses and modifications of and departures from the specific embodiments described herein without departing from the inventive concepts.