William C. Zarnstorff

Effect of Propranolol on Systemic and Coronary Hemodynamics at Rest and during Simulated Exercise

The systemic and coronary hemodynamic effects of relatively large doses of propranolol have been studied following its infusion into intact anesthetized dogs at rest and during simulated exercise. At rest, the administration of propranolol was associated with decreased cardiac output and ventricular work and increased peripheral, pulmonary, and coronary vascular resistances. Coronary blood flow and coronary sinus oxygen content decreased while myocardial oxygen consumption and the index of cardiac efficiency were unchanged. The usual hemodynamic response to mild exercise was obtained, with increased cardiac output, cardiac work, body oxygen consumption, and a modest but insignificant increase in coronary blood flow. When propranolol was given and the same exercise continued, body oxygen consumption, cardiac output, and left ventricular work significantly decreased. Insignificant decreases occurred in coronary blood flow, left ventricular oxygen usage, and coronary sinus oxygen content. The present observations are consistent with the thesis that beta-adrenergic blockade induced by propranolol decreases cardiac work at rest and reduces the cardiovascular response to exercise.

Computerized Fluoroscopy Techniques For Non-Invasive Cardiovascular Imaging

A number of methods for visualizing the cardiovascular system of dogs and humans in real time have been developed and are grouped under the heading computerized fluoroscopy. Such techniques provide images capable of high contrast sensitivity and moderate spatial resolution (~ 1 mm). A standard image intensifier - television chain used in connection with a Lpecially constructed digital video image processor (V.I.P.) is capable of producing contrast enhanced difference images at rates up to 60/second. Such difference images can isolate small concentrations of iodine which have been administered intravenously through peripheral veins. Such non-invasive techniques have been used to visualize: 1) The carotid arteries and fine structures in dogs and humans at typical rates of 2 per second, and 2) the heart chambers of both dogs and humans at typical display rates of 15-60 per second. For such studies 0.6-1.0 gms (Iodine)/kg (body mass) have provided excellent visualization of the cardiac chamber dynamics.

Intravenous Angiography Using Computerized Fluoroscopy

During the past several years, we have developed dedicated digital algorithms for real time processing of X-ray transmission imaging data obtained from an image intensifier television fluoroscopy system. Three imaging modes called Mask Mode Fluoroscopy, Mask Mode Radiography, and Time Interval Difference (T. I. D.) Imaging have been tested in over 100 patients since installation of this. apparatus at the University of Wisconsin Clinical Science Center. Feasibility studies have been conducted to determine the capability of these techniques for imaging the entire cardiovascular system, including peripheral arteries, using intravenous injections of iodinated contrast material.

A Phase-Shift Ultrasonic Flowmeter

An ultrasonic flowmeter using phase-shift techniques has been developed to measure phasic blood flow in animals. Lead zirconate titanate transducers are located diagonally opposed over the vessel so that 1-Mc ultrasound may be transmitted alternately upstream and downstream. The upstream and downstream transit times are measured by heterodyning the 1-Mc receiver crystal output to 10 kc, and then feeding this signal to an audio phasemeter. The phasemeter output is an ac signal whose magnitude represents flow velocity, and phase (relative to the chopper drive) indicates flow direction. The phasemeter output is amplified and synchronously detected to drive a recorder

Aortic root size in aortic valve disease. Its measurement and significance.

Abstract In 2 subjects who had a very small aortic root the surgical procedure of aortic valve replacement was greatly complicated, and obstruction of the aortic root and coronary arteries led to early death. All aortic valve replacements at the University of Wisconsin Hospital from 1963 through 1969 were reviewed. With use of the known catheter size as a reference, the size of the aortic root was calculated from preoperative cineangiocardiograms and correlated with the measurements made at operation. A significant correlation was found, especially with small aortic roots. It is stressed that the small aortic root should be recognized preoperatively when aortic valve replacement is contemplated.

Quantitation Techniques In Digital Subtraction Videoangiography

Digital subtraction videoangiography has been proven to be suitable for imaging the left ventricle and other cardiac chambers.l,2 The high contrast sensitivity and good cancellation of structural background enable this imaging technique to be used with intra-venous injections, which result in complete mixing of contrast medium with blood in the left ventricle.3 The digital nature of the image processor used in subtraction video-angiography enables convenient data collection and analysis. For these reasons, digital videoangiography is well suited to videodensitometric calculation of physiological quantities such as left ventricular ejection fraction.

Real-Time Digital Video Recording System

Image storage is a necessary consideration in a medical imaging system. Data generated by recently developed digital radiographic techniques may be stored on magnetic tape or disc in either analog or digital form. Video discs have desirable freeze frame and image sequencing properties allowing for flexible image manipulation and display. Whereas digital pre-processing has enabled excellent results to be obtained using analog storage, digital storage is ideal as far as bandwidth and noise properties are concerned. However, serial data rates of digital disc drives are limited to about 10 megabits per second, too slow for recording video information in real-time. Using a standard multi-platter magnetic disc drive we have constructed parallel read/write channels servicing sets of 9 or 10 surfaces simultaneously in order to achieve a data rate of 100 megabits per second. This permits storage of 815 512x512x9 bit images at 30 frames per second. Hardware configurations and applications of the real-time digital disc to subtraction angiography will be discussed.

An improved transmission oximeter using interference filters

Abstract An oximeter using monochromatic light is described, and data are presented which reveal the accuracy of determinations made by the oximeter as compared with the Van Slyke method of analysis. The standard error of this comparison was ±0.2 per cent in the range of hemoglobin concentration from 10 to 17 Gm. per 100 ml. Also, the present cuvette-oximeter allows continuous recording of dye concentration for use in indicator-dilution curves for measurement of blood flow.

Feasibility Of An Optical Beam Attenuator (OBA) For Optical Equalization In Camera-Based X-Ray Imaging Systems

We have investigated the feasibility of an optical beam attenuator (OBA) for image equalization in the optical light path of a camera-based x-ray imaging system. In our OBA design, a liquid crystal device (LCD) operated in transmissive mode is used to equalize low spatial frequencies. In most camera systems, compression of image dynamic range will result in improved performance. The advantages of optical equalization include bit compression for digital applications, video-rate equalization, detective quantum efficiency (DQE) improvement at high dose rates, and high-pass frequency filtration for film-based applications. A prototype OBA system has been constructed and installed in our DSA imaging laboratory. Equalized phantom images have been obtained which demonstrate improved visualization of structures in the darker regions of the image. The effect of the OBA on system limiting spatial resolution and system noise performance has also been investigated.

Adaptive Processing Algorithms For Intravenous Digital Subtraction Coronary Angiography

Digital Subtraction Angiography (DSA) is commonly used in conjunction with intravenous contrast injection for detection of atherosclerotic disease in arteries outside of the heart. Images of coronary arteries obtained with intravenous DSA have been limited in quality by several important factors. Among these is the confusing background provided by superposed pulmonary veins. Because these opacify just before the coronary arteries, conventional remasking results in substantial loss in coronary artery contrast. This paper presents preliminary work on a processing scheme in which the degree of correlation between the contrast pass curves in individual pixels and a reference region can be used to adaptively suppress pulmonary structures.