Current-voltage curves of black lipid membranes at high electric fields.
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Cholesterol↗
Biomedical subjects
R Brennecke
Publications and source records attributed to R Brennecke.
High-resolution two-dimensional echocardiography improves the quantification of left ventricular function.
It is not clear if newer echo technology prevents underestimation of ejection fraction in comparison with cineventriculography (CVG). Before undergoing CVG, 48 patients were studied with state-of-the-art, high-resolution two-dimensional echocardiography with a 3.5 MHz transducer, 96 crystals, and digital storing (slow motion and cine-loop). These data are compared with results published by us in 1983 (37 patients). Volumes were calculated using the biplane method of discs in a single area length. Exclusion criteria in 1990 were poor two-dimensional echocardiography quality (n = 6) and extra-systole during CVG (n = 4). The difference between the mean values of the angiography and echocardiography data in the new study (1990) were 4.7 ml/m2/body surface area (BSA) for the end-diastolic volume, 0.1 ml/m2 for the end-systolic volume, and 1.5% for the ejection fraction (all NS). The mean difference between both methods in the old study (1983) were -39.1 ml/m2/BSA (p less than 0.001) for end-diastolic volume, -17.4 ml/m2 (p less than 0.001) for end-systolic volume, and -7.2% for ejection fraction (p less than 0.001). The regression equation for determination of ejection fraction was y = 0.606x + 13, r = 0.803 for the old study, and y = 0.935x + 2.5; r = 0.935 for the new study. These results indicate that state-of-the-art, high-resolution two-dimensional echocardiography prevents the systematic underestimation of left ventricular volume and ejection fraction, most likely because of better delineation of endocardium in end-systole.
Adult↗
Intravenous angiocardiography using digital image processing. II. Detection of left-to-right shunts in an animal model.
Digital image processing was applied in an experimental model to study the feasibility of intravenous angiocardiography for the detection of cardiac lesions with left-to-right shunting. Methods were designed to produce ventricular and atrial septal defects (VSD, ASD) as well as patent ductus arteriosus (PDA) equivalent in pigs. After intravenous (IV) injection of 0.5-1 ml of Urografin 76% per kg body weight, digitization and computerized processing of roentgen video images recorded at a rate of 50 fields per second was performed. The radiographic images were recorded in the four-chamber view obtained by 30-35 degrees of caudocranial angulation and 50-60 degrees of left anterior oblique positioning of the animal. The processing of images included electrocardiogramgated background subtraction, rescaling, and sometimes histogram equalization. Integration of multiple background and multiple contrast images was performed in order to increase the signal-to-noise ratio. Ventricular septal defects and patent ductus arteriosus could be detected per se, while atrial septal defect only could be indirectly detected. Respiratory motion artifacts could be avoided by cross-correlation respiratory gating or by subtracting left ventricular end systole from end diastole during the same cardiac cycle of left ventricular opacification. The results of the experiments in pigs are the basis for continued clinical use of digitized IV angiocardiography.
Angiocardiography↗
Assessment of left ventricular muscle volume by digital angiocardiography.
By means of digital image processing, the entire myocardial wall of the left ventricle could be visualized by biplanar angiocardiography in animal experiments using 14 pigs (weight, 16-25 kg). The resulting images of the myocardial wall allowed dimensional measurement by videometry. The muscle volume was computed according to Simpson's rule for end diastole and end systole and compared with postmortem measurements. Replication of the procedure resulted in a 95% confidence interval of +/- 11% (+/- 5.6 ml) at maximum. Comparison with postmortem data showed highly significant correlations of r = 0.894 (end diastole) and r = 0.938 (end systole). This study points out that digital image processing allows a reliable assessment of myocardial volume from routine left ventricular angiocardiography. Besides early clinical applications, the method has been successfully used to visualize nonperfused segments of the myocardial wall in artificial infarction.
Angiocardiography↗
Interactions between black lipid membranes and the loosely bound proteins from erythrocyte membranes.
The loosely bound proteins from human erythrocyte membranes induce an up to more than 103-fold increase in the electrical conductivity of black lipid membranes made from oxidized cholesterol. The conductivity increase continues until the membrane breaks. Its magnitude insreases with increasing protein concentration and salt concentration. The results are compared with earlier results obtained with the strongly bound proteins from erythrocyte membranes.
Blood Proteins↗
Intravenous angiocardiography using digital image processing: I. Experience with axial projections in normal pigs.
Computerized digitization and processing of roentgen video images was performed in four-chamber-view intravenous angiocardiography in normal pigs. Significant contrast enhancement was obtained through electrocardiogram-gated background subtraction and rescaling after integration of multiple background and contrast images. Histogram equalization and time parameter extraction or functional imaging was also used. The left and right heart were well visualized after intravenous injection of 0.5-1 ml Urografin-76% per kg of body weight. Image processing of left and right ventricular end diastolic and end systolic frames was performed as well as subtraction of right and left end systolic from end diastolic frames and subtraction of right from left heart frames. If left ventricular end systolic images were subtracted from end diastolic images, the left ventricle was seen without continuity with the left atrium. Through time interval difference processing, left ventricular wall motion per time unit could be studied. The results were the basis for subsequent experiments concerning detection of septal defects in pigs as well as clinical studies.
Angiocardiography↗