Lee T. Andrews

Quantification of thallium-201 scintigrams in acute myocardial infarction

A method has been developed for measurement of myocardial infarct size from thallium-201 scintigrams that depends on computer measurement of levels of radioactivity in the myocardium. In 16 dogs, thallium-201 scintigrams were obtained in the left lateral and left anterior oblique projections 48 hours after ligation of the left anterior descending coronary artery. Scintigraphic results were obtained by two independent observers and were compared with tissue measurements of infarct volume calculated from thallium autoradiograms and nitro-blue tetrazolium (NBT)-stained tissue slices. Infarct volumes derived from tissue measurements were used to develop criteria for the computer scintigraphic technique. There was no significant difference in the scintigraphic measurements made by the two observers. Scintigraphic infarct size in the left lateral and left anterior oblique projections correlated with tissue infarct size with r values of 0.88 and 0.75, respectively, for thallium autoradiography and 0.71 and 0.70, respectively, for NBT tissue staining. The range of infarct volume was 3.3 to 14.8 percent of the left ventricular mass. Results of this study suggest that scintigraphic quantitation of infarct size is feasible in this dog model.

Real-time analysis of EEG using Walsh transforms.

Abstract Analysis of electroencephalogram (EEG) signals has been an area of considerable interest since the advent of inexpensive minicomputers in the mid to late 1960s. One of the major drawbacks to EEG analysis has been the inability to handle multiple demands in real-time. This paper presents a reasonable alternative to traditional Fourier analysis by proposing the use of the Fast Walsh Transform. Such problems as phase sensitivity and general acceptability of the Walsh power spectrum are discussed.

Acute myocardial ischemia detected in dogs by temporal variation in two-dimensional ultrasound gray level☆

This study tests the hypothesis that acute myocardial ischemia induces a characteristic temporal variation in regional ultrasound amplitudes. Myocardial ischemia was created by circumflex coronary artery occlusion in seven closed-chest mongrel dogs. Ultrasound images were acquired prior to occlusion and post-occlusion on a phased-array two-dimensional system. Unprocessed ultrasound data from end-diastolic images were taken digitally for quantitative gray level analysis. Temporal variation in ultrasonic gray level of a nonischemic control region was compared to the temporal variation in gray level of the ischemic area. In the ischemic area, the average gray level for all seven dogs increased from 39.2 +/- 4.2 prior to occlusion to 42.5 +/- 4.9 at 15 minutes after occlusion, and then to 44.4 +/- 5.9, 45.3 +/- 6.2, and 47.0 +/- 6.0 at 30, 60, and 120 minutes, respectively (p less than 0.05 for control vs 15 minutes and 15 minutes vs 120 minutes). No significant changes in the average gray level of all seven dogs occurred in the nonischemic area from pre-occlusion to 2 hours post-occlusion (38.8 +/- 8.8, 38.4 +/- 8.0, 37.7 +/- 8.4, 37.8 +/- 8.5, and 38.0 +/- 8.2 for control, 15, 30, 60, and 120 minutes, respectively. These data show that regions of acute myocardial ischemia can be characterized by temporal variation in intramyocardial ultrasonic gray level, not only from the time before coronary occlusion to 15 minutes after occlusion, but also between 15 and 120 minutes in the post-occlusion period. Gray level values in nonischemic regions of the left ventricle are remarkably constant over time.

Automatic detection of inter-frame motion in echocardiographic images.

Signal averaging of echocardiographic frames acquired over multiple cardiac cycles has been used to improve image quality. However, misalignment of frames from respiration, transducer or patient movement, and irregular cardiac contraction affects the quality of the resultant averaged image. A motion detection system has been developed using inter-frame subtraction and statistical pattern recognition techniques. Automatic selection of frames exhibiting significant motion in a canine cardiac model compare favorably to manual selection by cardiologists (phi = 0.94) in a test set of 103 images. This method, combined with signal averaging, has resulted in an improvement in image quality.

Fusion of digital image processing and video on the desktop

The use of digital image processing techniques to create compelling multimedia and video using VideoFusion, a Macintosh application for processing QuickTime movies is described. VideoFusion provides a toolbox for video processing, including a wide variety of video editing techniques, compositing, chroma keying, special effects and 3D transforms.<<ETX>>

Functional imaging as an indicator of diagnostic information in cardiac magnetic-resonance images

Magnetic Resonance (MR) images of the human heart provide three dimensional geometric information about the location of cardiac structures throughout the cardiac cycle. Analysis of this four dimensional data set allows detection of abnormal cardiac function related to the presence of coronary artery disease. To assist in this analysis, quantitative measurements of cardiac performance are made from the MR data including ejection fractions, regional wall motion and myocardial wall thickening. Analysis of cardiac performance provided by quantitative analysis of MR data can be aided by computer graphics presentation techniques. Two and three dimensional functional images are computed to indicate regions of abnormality based on the previous methods. The two dimensional images are created using color graphics overlays on the original MR image to represent performance. Polygon surface modeling techniques are used to represent data which is three dimensional, such as blood pool volumes. The surface of these images are color encoded by regional ejection fraction, wall motion or wall thickening. A functional image sequence is constructed at each phase of the cardiac cycle and displayed as a movie loop for review by the physician. Selection of a region on the functional image allows visual interpretation of the original MR images, graphical plots of cardiac function and tabular results. Color encoding is based on absolute measurements and comparison to standard normal templates of cardiac performance.

Three-dimensional graphic renderings of cardiac magnetic resonance images

A method of constructing a three-dimensional computer model of the human heart from respiratory and cardiac gated magnetic resonance images (MRI) is reported. This model can be animated according to motion derived from the MR images. The ability to section the model in any plane and orientation to examine internal structure is also reported. Functional images can be generated for education of medical students. The images allow the student to simulate myocardial infarctions and other disease states with high-resolution computer graphics. Other functional images, such as 3-D volumes, have been rendered to aid clinicians in the interpretation of planar MR scans. Normal and abnormal regions are highlighted with color and referenced to the original MR images.<<ETX>>

A workstation for quantitative analysis of magnetic resonance (MR) cardiac images

A description is given of a workstation developed at the Medical College of Ohio for use in quantitative functional analysis of cardiac magnetic resonance imaging (MRI). The workstation is based on a Macintosh II computer and was developed using the Smalltalk-80 programming environment. The workstation is used clinically by physicians to aid in functional analysis of the heart and early detection of coronary artery disease.<<ETX>>

Left ventricular function from computer processed magnetic resonance images

Cross-sectional magnetic resonance (MR) images of the heart from nine male and ten female normal subjects were computer processed to establish normal templates of left ventricular function. Ventricular volumes at end-diastole and end-systole were significantly greater in males than females but ejection fractions were identical. For analysis of regional endocardial motion, the use of a floating centroid gave more uniform values compared with a fixed centroid method. Endocardial motion values were not significantly different for males and females. The data obtained can be used to define abnormalities of left ventricular function in patients with heart disease. Male/female differences in ventricular volume will require separate templates but it appears that analysis of ejection fraction and regional endocardial motion can be performed from the same templates for males and females.<<ETX>>

An MR workstation for quantitative analysis of cardiac images

A workstation has been developed to analyze magnetic resonance (MR) images of the heart. The system can be used to measure wall thickness, wall motion, and global and regional ejection fractions quantitatively and compare the results to anatomical templates for normal subjects. The application is written in Smalltalk-80 and runs on an Apple Macintosh II. Smalltalk is an object-oriented language and provides a prototyping environment for the development of medical systems. The workstation provides an easy-to-use interface and can display images without the need for additional hardware. The workstation is connected to the campus network, which allows the transfer of MR images to the workstation. This allows physicians to review images and analyze cardiac function from their remotely located offices.<<ETX>>