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Right Ventricular Volume Determination in Children: Value of Digital Subtraction Angiocardiography

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Abstract

We employed image enhancement techniques [1] to determine the extent to which digital subtraction angiocardiography (DSA), after injection of small amounts of contrast medium with reduced flow into the right ventricle (RV), can provide information previously available only after large intraventricular contrast administration.

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Conference Paper
We report on the enhancement of video-angiocardiographic image-series by digital preprocessing methods including a newly developed technique of interframe subtraction recording as well as computerized image subtraction, integration, and nonlinear representation techniques. Background suppression and noise reduction obtained through these processes applied to roentgen images from animal experiments are demonstrated. Image-series handling and storage are simplified by combining a new method of digitally formatted videotape recording with conventional digital storage of selected image data in the periphery of a minicomputer system.
Article
Digital images of the left ventricle obtained at 30 frames/second from continuous fluoroscopy after intravenous injection of contrast medium (digital intravenous ventriculography) were used to estimate left ventricular (LV) volumes and ejection fraction with use of several techniques for identifying the ventriculographic silhouette. The digital technique was compared with direct contrast left ventriculography in 26 patients undergoing diagnostic cardiac catheterization. End-diastolic and end-systolic volumes calculated from digital intravenous and direct left ventriculograms were obtained with use of a standard area-length formula. Both end-diastolic volume (EDV) (r = 0.88, y = 1.06x - 17.1 ml) and end-systolic volume (ESV) (r = 0.89, y = 0.96x + 0.43 ml) determined from digital intravenous ventriculography (mask mode images) correlated closely with those obtained by direct left ventriculography. Combining the EDV and ESV to define the relation between the 2 techniques yielded an even closer correlation (r = 0.96). There was also good correlation between the 2 techniques for measurement of ejection fraction (r = 0.81, standard error of the estimate 6.7%). Measurements from direct left ventriculography were frequently invalidated by ventricular arrhythmias during the time of opacification of the left ventricle; this was rarely the case for digital intravenous ventriculography. It is concluded that area-length estimates of LV volumes and ejection fraction can be accurately obtained from digital processing of fluoroscopic LV images after intravenous injection of contrast medium.
Article
First-pass left ventriculograms were obtained using digital subtraction angiography in 24 patients after intravenous injection of 30 to 40 ml of iodinated contrast material. An image processing computer was used to enhance the iodine signal in the image relative to the background soft tissue by digitizing each new frame of the fluoroscopic exposure and subtracting from it a stored "mask" image. Digital left ventriculograms were obtained in the 30-degree right anterior oblique (RAO) position using high fluoroscopic exposure levels [8 mA and 70 to 90 kVp] and compared to 30-degree RAO cineangiograms obtained at cardiac catheterization. Standard cineanglograms were performed in 33 patients at cardiac catheterization but six (18%) were excluded because of runs of ventricular tachycardia initiated by the standard intraventricular injection of 40 ml of contrast media. Digital subtraction angiography was attempted in the 33 patients and left ventriculograms of clinically useful quality were obtained in 30 (91%). There were close correlations between end-diastolic volumes (r = 0.82), end-systolic volums (r = 0.93), and ejection fractions (r = 0.96). Multiple premature ventricular contractions occurred in a total of 10 of 33 (30%) patients during standard intraventricular cineangiography but did not occur in any patients during the intravenous first-pass technique. Wall motion abnormalities were visualized as well by digital angiography as by the standard method. Digital angiography appears to be an important new addition to diagnostic cardiology because it provides a less invasive outpatient method for obtaining contrast left ventriculograms which have much greater spatial resolution than radionuclide cineangiograms.
Article
Cineventriculography is of considerable value in the dimensional analysis of the left ventricular cavity, but conventional methods necessitate injection of large amounts of contrast medium. In this study, small dose left ventriculography, using only 5 ml of dye, was performed in order to minimize the untoward effects of contrast medium. A computer-aided image processing system was also developed to enhance the contrast of the ventricular image by subtracting the reference image to eliminate irrelevant background. The boundary of the left ventricular cavity was automatically determined to calculate the instantaneous volume change throughout the cardiac cycle. With use of this small dose of dye, the elevation of left ventricular end-diastolic pressure that consistently occurred 1 to 3 minutes after injection of conventional large doses could be avoided. (End-diastolic pressure at 1 minute after dye injection averaged 11.8 +/- 4.9 [mean +/- standard deviation] for small dose and 19.1 +/- 6.1 mm Hg for large dose injection.) Values for end-diastolic volume, end-systolic volume and ejection fraction calculated from the two consecutive small and large dose left ventriculograms in 16 patients were similar. Thus, minimal doses of contrast medium permit accurate measurement of left ventricular dimension and function without significant hemodynamic derangement. The optimal projection for regional wall motion analysis can easily be selected by this method with repeated exposure at various degrees of obliquity. With this technique, even noninvasive measurement of left ventricular volume can be provided by intravenous injection of small doses of contrast agent.