Biomedical subjects
Publications and source records attributed to K Lackner.
MR has replaced CT in cardiology as a tomographic examination method with the exception of the identification and differentiation of cardiac calcifications. MR combines good morphological visualization with function diagnostics and biochemical informations. Both methods are inappropriate for diagnosing diseases of the coronary vessels.
Projection properties of a digital fluorographic system for chest examinations are examined using varying test phantoms. A maximal geometric distortion of +14% between the centre and the periphery of the image intensifier and a maximal spatial resolution of 2.6 LP/mm is found. Contrast detail diagrams are used to show the combination of spatial and contrast resolution of the system. Compared with diagrams for conventional radiographic systems there is a significant loss of resolution.
The accuracy of colour Doppler sonography for measuring various aspects of intravascular flow (volume and velocity), under varying conditions, was studied experimentally. The effect of variable Doppler angles, different flow paths, frequency and vessel diameter on flow profiles was examined. At all levels of measurement (range 14 ml/min to 566 ml/min) there was a very close correlation between the actual and measured values (r greater than 0.99) and high accuracy. In the detection of very slow flow rates, the use of a specific high pass filter technique was able to quantify blood flow velocities of just under 1 cm./second. Multigated colour Doppler sonography is better for measuring flow volumes than a single channel duplex system.
The volumes of the four recti muscles and the orbital fat was measured by CT in 40 normal persons and in 60 patients with clinically confirmed Graves' disease. Compared with normal persons, 42 patients (70%) showed an increase in muscle volume and 28 patients (46.7%) an increase in the amount of fat. In nine patients (15%) muscle volume was normal, but the fat was increased. By using volumetric measurements, the amount of fat in the orbits in patients with Graves' disease could be determined.
Angiography is rarely performed in the intensive-care ward. Indications are: pulmonary embolism, unstable angina pectoris or myocardial infarction, gastrointestinal haemorrhage, acute arterial occlusion, traumatic vascular lesions, aneurysms and if a foreign body has to be extracted. It will always be necessary to weigh the pros and cons, that is to say the risks and danger involved in transporting the patient and in performing an invasive diagnostic procedure on the one hand, and the possible therapeutic gain on the other.
The case of a 36 year old patient with acute pancreatitis is presented whose clinical course was dominated by extensive peripancreatic fluid exsudation and formation of cysts. Risky surgery in the acute phase of the disease could be avoided by ultrasonic guided percutaneous punction and placing of several, partly transhepatic, catheters. The fluid collections could be drained completely and showed no recurrence.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Ungated cardio-CT provides good morphologic information in the case of congenital heart disease, volume or pressure loading, left ventricular aneurysm, tumours, thrombi, cardiac calcifications and pericardial diseases. It allows qualitative assessments of myocardial thickness and perfusion of coronary bypass grafts. ECG-gated cardio-CT allows a quantitative assessment of systolic and diastolic myocardial thickness, volume calculation of cardiac cavities and evaluation of functional parameters. The correlation of the calculated left ventricular ejection fraction comparing laevocardiography and ECG-gated cardio-CT was poor (r = 0.7) mainly due to the comparable poor time resolution on the side of cardio-CT (approximately 0.1s). The quantitative analysis of regional wall motion based on cardio-CT showed for the diagnosis of pathologic wall motion a specificity of 80.5%, sensitivity of 73.9% and accuracy of 75.7%. Side effects must be taken into account following the injection of 200-250 ml hyperosmolar contrast medium during 5-10 minutes which causes intravascular fluid retention and cardiac volume loading. Patients prone to cardiac decompensation should be excluded from cardio-CT examinations.
A linear array colour Doppler sonographic method was used experimentally on a vessel phantom in order to determine flow velocity, and the results were compared with DSA. Both the Doppler and the DSA method showed very good agreement with true velocities (r greater than 0.97). The Doppler method underestimated flow velocity. Early clinical results indicate that colour Doppler sonography is able, at the same time, to demonstrate morphology and function (direction flow and flow velocity) of significant vascular abnormalities by a non-invasive method.
A method for the calculation of flow velocities in vessels is introduced. The method is validated by measurements with an artificial model. Measurements with the carrier fluids sodium chloride solution and human blood using various scattering objects, show good correlation (r greater than +0.9) of the calculated and volumetrically measured velocities. With a menu-oriented computer program, measurement of flow velocities on DSA series can be made following the routine clinical examination.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Contrast performance in MR tomography is influenced by the choice of technical parameters such as pulse repetition time (TR), echo time (TE) and inversion time (TI) in the same manner as by differences in the tissue parameters relaxation time and proton density. To optimise image contrast it is therefore suggested to preselect the imaging sequence. Such presselection is possible on the basis of isosignal visualisations S(T1, T2). In the inversion recovery sequence (IR) the isosignal images obtained with the parameters TE, TI, TR enable determination of relaxation time T1 by graphic representation, from the time of zero passage of the longitudinal tissue magnetisation.
The results of 242 percutaneous nephropyelostomies in 215 patients were analysed retrospectively. No consideration was given to the experience of the individual operators. There was a total complication rate of 36.4% (mild complications 32.2%, serious complications 34.1%, fatality 0.4%). Rapid reduction in serum creatinine could be demonstrated following drainage in patients in whom renal function had been damaged by obstruction.
ECG-triggered cardio-MRT, using T1-weighted SE sequences, provides images of the heart showing very high anatomical resolution. So far, however, it has not been possible to demonstrate the morphology of the valves and coronary vessels. By using multiplanar sections, it is possible to obtain cuts which are perpendicular to the portion of myocardium or valve under consideration. This provides optimal imaging for morphological diagnosis and for evaluating the ventricular myocardium and its function.
By using high field strengths and surface coils, MRT achieves a resolution comparable with CT in the orbita. The advantages of MRT are good contrast resolution and imaging in several planes. Twenty-six patients have been examined by MRT, which has shown high sensitivity and good detail for the demonstration of pathological changes. In spite of this, MRT at present is not a realistic alternative to ultrasound and CT, because it is unable to demonstrate bone and calcification; its specificity is low, but the time and cost of the examination is high. It is indicated only for problems involving the optic nerve and chiasma.