Dietrich Onnasch

Dietrich Onnasch
Christian-Albrechts-Universität zu Kiel | CAU · UKSH Klinik für angeborene Herzfehler und Kinderkardiologie

PhD

About

226
Publications
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2,168
Citations

Publications

Publications (226)
Article
Full-text available
European states within the EEC are required to establish and use diagnostic reference levels (DRLs) in X-ray examinations. However, up to now there have been no DRLs for cardiac catheterization in children, nor as a rule is the effective dose estimated. We have evaluated the dose-area products (DAPs) for three different types of angiocardiography s...
Article
Full-text available
The γ‐ray‐induced electric conductivity in fused silica is studied theoretically and experimentally as a function of temperature, electric field strength, sample thickness, and irradiation time. Synthetic glasses containing water show the highest induced conductivity. Caused by an increase of positive centres capturing the excited electrons, the co...
Article
Full-text available
The γ-ray-induced current in synthetic fused silica (containing water) is saturated at field strengths ⪆ 1.4 × 104 V/cm caused by two effects. Besides the schubweg saturation known from photoconductors with blocking contacts, the saturation of the drift velocity of the electrons at the level of the velocity of sound is demonstrated. In some samples...
Article
The objective of the study was to estimate the capacity of pressure volume (PV) loop analysis to assess right ventricular (RV) function after Fallot (TOF) repair. Fifty six patients were examined after TOF repair. PV loops were constructed from RV angiocardiography and simultaneous pressure measurement. Patients were divided in three groups accordi...
Article
Full-text available
According to national and international rules the x-ray exposure of cardiac catheter examinations have to be measured. For a Philips Integris angiographic system used for paediatric heart catheterization we found severe errors in the indicated time of fluoroscopy and total dose area product ( DAP) both for fluoroscopy and radiography. Fluoroscopy t...
Article
Full-text available
In the paediatric cardiac catheterization laboratory the reduction of the radiation dose of diagnostic and interventional procedures is of high priority. Therefore, we performed an experimental study for optimizing the automatic exposure control (AEC) for cardiac angiography. With a Philips Integris BH 5000 system, six AEC programs were configured...
Conference Paper
A computer program is presented, which is suitable for both enddiastolic and endsystolic and semi-automated biplane frame-by-frame volume determination of the right (RV) and left (LV) ventricle. Compared to other programs an important features is presenting the biplane images side by side after optimal pairing. That means the images are rotated in...
Article
Compared to single plane angiographic systems, biplane systems offer the possibility of a merged evaluation of the two x-ray projections. A computer program was developed that allows the assessment of enddiastolic and endsystolic volumes and frame-by-frame analysis of the left and right ventricle based on representing the biplane angiograms as opti...
Conference Paper
Apart from giving more complete information, biplane angiographic systems offer advantages that are not used when the two angiograms are evaluated separately. The combined use of both planes is important for on-line measurements of angiographic distances in the catheterization laboratory and for improving the quality of contour detection for quanti...
Conference Paper
Full-text available
DICOM conformity alone does not guarantee the interoperability of imaging equipment developed by different parties. In a survey, the DICOM data sets of 19 complete angiographic examinations have bean compared. It was found that most data sets are DICOM-compliant and that the image data are encoded in a similar way. On the other hand, the interopera...
Article
In medical image processing original image data on archive servers may absolutely not be modified directly. On the other hand, images from read-only devices like CD-ROM cannot be changed and saved on the same storage medium. In both cases the modified data have to be stored as a second version and large amounts of storage volume are needed. We avoi...
Article
We describe an application of the binary tomography technique to routinely acquired biplane cardiac angiograms. The described model-based reconstruction approach aims to recover the 3D shape of the left or right heart chamber from the density profiles of orthogonal bi-plane ventriculograms. Several geometric and densitometric imaging errors need to...
Article
The use of bolus injections of contrast media containing gadolinium for magnetic resonance imaging and their potential use as x-ray absorbents require the evaluation of possible cardiovascular side effects. The hemodynamic reactions of high doses (0.6 mmol/ kg) of gadopentetate dimeglumine (gadolinium [Gd]-DTPA, Magnevist) were evaluated and compar...
Chapter
Examination of the vascular system requires sharply contrasted images taken as flash exposures in a fast sequence. Since vessels can follow any direction in space, it is of utmost importance to have a high degree of freedom in selecting the appropriate projection. The relevant section of the vessel has to be shown with minimal foreshortening.
Conference Paper
A Web interface for intra-hospital communication was added to our newly-implemented integrated cathlab system to demonstrate the viability of Web technology even for this complex subsystem. Based on this experience, we propose to install similar Web gateways for other subsystems of a cardiological department and to allow patient-oriented acces via...
Conference Paper
Focussing on the goals of integration and ease of use a system for processing hemodynamic signals, logging events, and advanced postprocessing was implemented based on standard PC hardware, a state-of-the-art graphical user interface (GUI), and a Unix operating system. We report on the design, implementation, and successful operation since November...
Article
Full-text available
The aim of this work is the three-dimensional (3-D) reconstruction of the left or right heart chamber from digital biplane angiograms. The approach used, the binary reconstruction, exploits the density information of subtracted ventriculograms from two orthogonal views in addition to the ventricular contours. The ambiguity of the problem is largely...
Conference Paper
This paper describes the design and implementation of a server for acquisition of physiological signals and digital messages from laboratory equipment. Its use in a heart catherization laboratory and the advantages of this distributed approach over a monolithic system are discussed. Modularity, hardware independence, adaptability and real-time capa...
Article
Digital angiographic images contain a significant amount of redundancy as well as some irrelevant information and noise. Therefore, it is possible to reduce the number of bits required to represent an image considerably. The lossy JPEG standard may be used provided that no significant diagnostic information is lost. As implemented in presently avai...
Article
To prove the feasibility of performing percutaneous transcatheter embolectomy using a funnel-shaped catheter tip and balloon embolectomy catheters. A theoretical model is described to assess the influence of the diameter of an introductory device and coaxially introduced embolectomy catheter. A funnel-shaped catheter tip was attached to 7F, 8F, and...
Conference Paper
A system is described that reconstructs the 3-D shape of the left or right ventricle from biplane angiocardiographic image sequences. The ventricle is built up in slices with a model-based binary reconstruction technique. This exploits the density information in addition to the ventricular contours. The ambiguity of the problem is removed by consid...
Conference Paper
The lossy JPEG standard may be used for high performance image compression. As implemented in presently available hard- and software in most cases the so-called luminance quantization table is applied for gray level images, which may be scaled by a quality factor. The questions arise which quality factor is optimal and whether it is possible and wo...
Article
In an experimental study in pigs, the function of monocuspid and bicuspid patches was compared to improve surgical reconstruction of a hypoplastic pulmonary root. Segments from glutaraldehyde-treated porcine aortic roots served as monocuspid and bicuspid patches. Their leaflets and commissures were marked with radiopaque metal clips. Marker movemen...
Chapter
The identification and matching of details in biplane angiocardiograms taken from an oblique view is complicated by rotations, translations and different magnifications of the images. A procedure for pairing images is proposed that is applicable to arbitrary biplane gantry systems and projections.
Conference Paper
The binary reconstruction of the ventricles from clinically acquired biplane angiocardiograms requires the preprocessing of the raw image data. The necessary steps of densitometric and geometric image correction and processing are presented and discussed. By means of an end-diastolic laevocardiogram their effects are demonstrated by comparing the b...
Conference Paper
In the X-ray image intensifier TV system there are geometric image distortions which can be subdivided into pincushion distortions, S-shaped warping, image twisting, and shifting. These errors depend partly on the direction of the geomagnetic field relative to the image intensifier axis and are to be corrected for each view specifically. For caudal...
Article
Conventional biologic and mechanical prostheses have important limitations with regard to their hemodynamic characteristics and long-term durability. We evaluated the hemodynamic function of a stentless porcine aortic prosthesis in 10 patients by invasive pressure measurements and angiography with videodensitometry 8 +/- 4 days after operation, as...
Article
The long-term performance of two different types of flexible aortic prostheses was evaluated in 10 patients who received a stentless porcine prosthetic valve (group A) and in 18 patients who underwent aortic valve replacement with an aortic homograft (group B). In group A early postoperative angiography (5-16 days post surgery) revealed a mean grad...
Article
Full-text available
Videodensitometry allows to obtain both left and right ventricular ejection fraction (EF) and aortic or pulmonary regurgitant fraction (RGF) from the wash-out curve of contrast medium. We developed this technique to digital densitometry and integrated it in the standard digital image acquisition system 'Digitron' using Siemens user's library. Sourc...
Article
The anatomy of valsalva's sinus is such that it decreases the mechanical stress on the leaflets of the aortic valve. Artificial stents impair the hemodynamic performance of an aortic bioprosthesis and lead to unphysiological functional stresses and may also shorten their durability. Therefore a semi-supported xenograft was developed which can be at...
Article
Im Verlauf der zweizeitigen anatomischen Korrektur der Transposition der großen Arterien [6] zeigt das Vektorkardiogramm (VKG) nach Frank [3] typische Veränderungen der Vektorschleife. Mit Hilfe rechnergestützter Vermessung wurden VKG-Parameter gesucht, die auf eine links-ventrikuläre Druckbelastung bei gleichzeitiger dominierender Rechtshypertroph...
Conference Paper
On the basis of 20 years of experience the authors discuss desirable future developments of the facilities and performance of the cardiac hemodynamic-angiographic laboratory. It is proposed that three self-supporting modular subsystems be merged into an integrated system using decentralized interfaces and networks. The subsystems perform (a) hemody...
Article
Between 1978 and 1987, 39 patients aged 1 day to 15 years underwentsurgery for symptomatic left ventricular inflow obstruction. Fourdiagnostic groups were identified: cor triatriatum (6 patients),supravalvar mitral membrane (SVMM) with a normal mitral valve (7 patients),SVMM with an abnormal mitral valve (9 patients) and mitral stenosis (17patients...
Article
To assess the feasibility of quantitative central venous digital angiocardiography, right ventricular spatial orientation, size, and shape were compared with measurements based on conventional angiocardiography, both obtained during routine cardiac catheterization in 21 children with various congenital heart defects. Without systematic error, corre...
Chapter
Commonly employed methods for the relief of the right ventricular outflow tract stenosis in tetralogy of Fallot are not ideal. In particular, pulmonary insufficiency cannot be prevented in most instances. For reconstruction, pulmonary and aortic allografts have been utilised (2, 5, 6, 9, 10, 14, 15, 19, 20), especially since newer methods of preser...
Chapter
Heart valve replacement aims to substitute malfunctioning valves by devices with perfect haemodynamic profiles. Although there is some evidence that promising results in this field may be achieved by allograft transplantation (1,5) follow-up remains mandatory to answer the question “What have you really done?” in the individual patient.
Chapter
The development of digital angiocardiography has provided new diagnostic approaches to quantitatively assess hemodynamic parameters by radio-opaque contrast absorption measurements. Aside from the advent of new image processing capabilities, the technical characteristics of X-ray systems have been substantially improved with the generation of stabi...
Chapter
As a technique, coronary angiography provides an opportunity to evaluate not only morphologic but also functional information of the coronary circulation. Until recently, visual interpretation of the temporal course of vascular contrast flow was the only method to detect regional flow abnormalities. For example, delayed contrast opacification was c...
Chapter
Conventional angiocardiography requires a large amount of contrast medium, which is especially detrimental in infants and children. In addition, a ventricular injection is often associated with catheter-induced ventricular ectopic rhythm [1–5], precluding optimal analysis of ventricular function, necessary in the pre- and postoperative assessment....
Chapter
Digital image processing techniques allow to visualize the coronary microcirculation by enhancing the capillary phase opacification of selective arteriograms. However, the spatial distribution and local extent of the myocardial perfusion is difficult to judge from only one X-ray projection. The planar technique is limited by the fact that angiograp...
Book
According to Schopenhauer problems are usually passing through three stages: - in the first stage they are ignored or just smiled at, - in the second stage they are fought, and in the third stage they are considered to be self-evident, just taken for granted. Whereas digital subtraction angiography (DSA) has obviously reached stage three of that sc...
Article
A 17-year old boy with hypertrophic obstructive cardiomyopathy (HOCM) developed repeated short runs of self terminating ventricular tachycardia 12 hours after starting oral verapamil, which was substituted for propranolol therapy. It is suggested that alterations in sympathetic tone induced by changing from a beta-blocker to a calcium antagonist mi...
Article
To gain information on physiologic postnatal cardiac growth in humans and to characterize the left ventricle (LV) when subjected to various types of overload during that period, angiocardiographic volume parameters in infants, children, and adolescents were analyzed. In normal subjects, the relationships between end-diastolic volume (EDV), end-syst...
Article
In female adolescents with pulmonary embolism such as in the presented 19 year old patient oral contraceptives have to be considered as an etiologic factor. It is important to consider this diagnosis even in that age group. The diagnosis can be verified by intravenous digital subtraction angiography.
Chapter
As a clinical cardiologist I would like to emphasize that the heart is a muscle pump for providing adequate blood flow to the organs and that the understanding of the specific mechanical function of this pump requires knowledge of its dynamic geometry. In particular the SIZE and the SHAPE of the heart chambers and their CHANGES during the cardiac c...
Article
In 16 patients, constituting 100% of children followed for up to 7 years after two-stage anatomic correction of complete transposition of the great arteries, clinical and electrocardiographic data, as well as cardiac catheterization data in 12 patients, were analyzed. None of them has had signs or symptoms of coronary or myocardial insufficiency af...
Article
To assess postoperative arrhythmias and AV-conduction defects associated with anatomic correction of simple transposition of the great arteries, 207 standard 12-lead surface and 43 24-hour electrocardiograms of all 17 patients followed after anatomic correction for up to 6.5 years were reviewed. No dysrhythmias or AV-conduction delays definitely at...
Chapter
Angiocardiographic diagnosis is still mainly based on the visual assessment of radiographic projection images recorded on photographic film. Considerable amounts of contrast material have to be selectively injected into the circulation in order to make the regions of diagnostic relevance visible in the superposition of the shadows of tissue and bon...
Chapter
Digital processing of coronary angiocardiograms provides the capability for visualizing myocardial opacification by applying contrast enhancement techniques. Smith et al. (1978) described roentgen scanning densitometry as a new method for the analysis of the spatial distribution as well as the movement of radiopaque indicators through the coronary...
Chapter
With increasing use of axial angiocardiography [1, 2], especially in patients with congenital heart disease, knowledge of left and right ventricular spatial orientation is of practical value. However, no systematic study exists of ventricular position during normal growth and in patients with typical congenital heart diseases. We therefore develope...
Chapter
The ability to enhance contrast qualities of opacified structures has promoted the use of digital imaging techniques for intravenous (IV) angiography. We have examined the performance of intravenous digital angiography (IVDSA) in 50 children (3 months to 16 years of age) for evaluation of the cardiovascular state immediately (3–6 days) after correc...
Chapter
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.
Chapter
To gain more insight into the natural history [1, 2] and right ventricular (RV) function in children with valvular pulmonary stenosis, we analyzed hemodynamic data of 18 infants and children who had two cardiac catheterizations without surgery and also quantitative angiocardiographic RV data of 38 additional patients.
Chapter
To determine the extent to which digital subtraction angiocardiography (DSA), after injection of small amounts of contrast medium with reduced flow into the left ventricle (LV), can provide information previously available only with large intraventricular contrast administration, we employed image enhancement techniques.
Chapter
The continued development of digital imaging techniques has resulted in advanced diagnostic capabilities for the assessment of coronary artery disease and myocardial ischemia. Enhancement of vascular and tissue opacification, as well as the extraction of perfusion parameters are the basic procedures in digital coronary angiography. In this survey d...
Article
Anatomic correction of transposition of the great arteries always entails circumferential anastomoses of the aorta and coronary arteries. Long-term success of this procedure is predicted on adequate growth of these anastomotic sites. To assess the size of these arteries, we performed one or two cardiac catheterization on 25 children from 1 to 53 mo...
Article
To evaluate the influence of the 2-stage anatomic correction of simple transposition of the great arteries on left ventricular (LV) function, pressure and angiocardiographic volume data were analyzed during resting conditions shortly before banding of the pulmonary trunk (n = 12) and before (n = 17) and after anatomic correction (n = 11), and compa...
Article
New techniques of digital image processing have been experimentally tested for the assessment of renal blood flow. The underlying principle in functional angiography is the extraction of flow parameters. Basically, density-time variations of the contrast medium are analyzed from each picture element of a 256 X 256 matrix. The real-time acquisition...
Article
The purpose of this study was the analysis of natural history and right ventricular function of infants and children with valvular pulmonary stenosis. Available for assessment were the pressures in the right ventricle and pulmonary artery in 5 infants and 13 children obtained at two cardiac catheterizations, performed at intervals of 2 to 12 years...
Article
Since the first comprehensive computerized videometric systems for quantitative assessment of the dynamic morphology and function of the heart have been developed, angiocardiographic image generation and computer aided evaluation have improved considerably. As a second method for morphological imaging echocardiography is also established in cardiol...
Article
The surgical creation of a supravalvular pulmonary stenosis (PS) adequate to prepare the left ventricle (LV) for anatomic correction in cases of simple transposition of the great arteries (TGA) is difficult. To gain more information on the hemodynamic changes immediately following PS of various degrees, pressures (P) in the right atrium (RA), right...
Article
The purpose of this work was to develop a device which allows slow progressive banding of a great artery in infants within 4 to 5 weeks. Employed was the hygroscopic casein ameroid. When brought in contact with fluids, an ameroid cylinder expands characteristically. An early phase of fast expansion proceeds gradually to a phase of slow growth. Size...
Article
The analysis of circulatory dynamics by functional data extraction from radiologic image sequences constitutes the latest development of digital (planar) imaging techniques in angiography. This development is part of the present evolution of other new imaging modalities in the various diagnostic fields in medicine. Angiographic parameter imaging is...