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Biomedical subjects

K Lackner

Publications and source records attributed to K Lackner.

At least 235 records · Page 13Linked to original sources
PubMed1982

[Validity of computed tomography for the demonstration of patent or occluded aortocoronary vein grafts. A multicenter study].

In 328 patients with 611 aortocoronary bypass grafts CT was performed and 96 of them with 199 grafts were additionally studied by angiography. The results showed a sensitivity of 92,6%, a specificity of 78,1% and an overall accuracy of 87,9% for CT, which proved to be a reliable method for non-invasive direct visualization of aortocoronary bypass grafts. It can be performed within few days after surgery and also in out-patients as a follow-up study. Graft occlusion demonstrated in CT should be verified by angiography, whenever it results in a therapeutic consequence. Conversely if CT reveals patency of the graft, an angiographic control study is not necessary.

Adult↗
PubMed1982

Assessment of regional myocardial uptake and metabolism of omega-(p-123I-phenyl) pentadecanoic acid with serial single-photon emission tomography.

The utility of myocardial imaging and assessment of regional myocardial metabolism of omega-(123I-paraphenyl-)pentadecanoic acid (I-PPA) by means of serial single-photon tomography is demonstrated in animal experiments. High quality cross sectional images of dog hearts with clear delineation of left ventricular walls are obtained. Myocardial infarcts are visualized as areas of deficient radioactivity uptake. I-PPA elimination from non-infarcted myocardial regions is significantly (p less than 0.001) prolonged when compared with unaffected controls. Hence, not only localized absence of uptake of free fatty acid by infarcted myocardium can be demonstrated with serial single-photon tomography but also general impairment of cardiac FFA-metabolism.

Animals↗
PubMed1982

[SPECT (201T1) of the myocardium after experimental infarction].

On the basis of an experimental model the extent was studied to which even small intramural myocardial ischemia can be demonstrated by SPECT. For this purpose ligature of the Ramus interventricularis anterior (n = 10) or of the Ramus circumflexus (n = 2) of the left coronary artery was performed in 12 dogs to produce myocardial lesions of the anterior and posterior wall. Transmission computed tomography (TCAT) served as a control method in 10 dogs showing that 6 lesions were transmural and 4 intramural. All infarctions could be detected by SPECT with a rotating gamma camera (TCAT: 9/10). TCAT after contrast media enhancement with its morphological advantages (high resolution) should, however, not be used in the acute phase of myocardial infarction because of its hemodynamic side effects. Thus, SPECT with 201T1 remains the method of choice even for the proof of minor intramural (acute) ischemic lesions.

Animals↗
PubMed1982

[Malpositions of the heart and the great vessels by CT (author's transl)].

The CT-findings of the most important kinds of malpositions of the heart are described. The differentiation between the venous and arterial heart cavities is possible noninvasively using a rapid bolus injection of contrast medium. If there is a malposition of the heart, uncertain findings of the heart configuration in the plain chest film can be explained by CT. Anomalies of the great vessels are detectable.

Dextrocardia↗
PubMed1982

[Measurements in triggered CT imaging of moving objects].

This paper describes results of measurements characterising the image properties of a CT apparatus triggered by an "R-peak simulator". For this purpose, a phantom was constructed in which--as straightforward simulation of a cardiac wall movement--a plate made of plexiglass of 5 mm wall thickness moves to and fro with a frequency nu (1 s-1 less than or equal to nu less than or equal to 2 s-1) and an amplitude of A = 10 mm. The number of scanning cycles during a measurement could be varied between 2 and 9. It was evident that the measured density values as well as the positions of the plate which could be ascertained from the CT images in the various phases of movement, especially at low frequencies and a large number of cycles, agree well with the real values; however, it was also found that both at the measured density values and the positions of the plate as seen from the CT images, systematic deviations occur, especially at high frequencies and a small number of scanning cycles.

Electrocardiography↗
PubMed1981

Tonic catecholaminergic inhibition of the spinal somato-sympathetic reflexes originating in the ventrolateral medulla oblongata.

In chloralose-anesthetized cats activity of the spinal and supraspinal components of the somato-sympathetic reflex were evoked in the white ramus at T3 by stimulation of the corresponding intercostal nerve. A blockade of all spinal pathways by means of a reversible cold blockade of the spinal cord at C2-C3 produced the following effects: (1) mean arterial blood pressure fell to 30-50 mm Hg and the tonic background activity in the white ramus was markedly reduced; (2) the amplitude of the spinal reflex was significantly increased and the supraspinal reflex was completely abolished; (3) localized cold block of the dorsolateral funiculus produced the same effect as cold block of the whole spinal cord; (4) neither baroreceptor denervation nor midcollicular decerebration altered these effects; and (5) the alpha-adrenoceptor agonist clonidine reduced the increased amplitude of the spinal reflex during cold blockade; this effect was reversed by the alpha-adrenoceptor antagonist yohimbine. Bilateral cold blockade of areas on the ventrolateral surface of the brain stem between the rootlets of the hypoglossal nerve and the trapezoid body caused the same effect on background and reflex activity in the white ramus as did spinal cord blockade. A mapping of the catecholaminergic (CA) neurons in the lower brain stem of the cat by means of the fluorescence method showed CA neurons in the ventrolateral medulla at two levels: (1) one group of neurons in the caudal medulla, which lies ventral and dorsal to the lateral reticular nucleus (corresponding to area A1 in the rat); and (2) a second group found more cranially and located ventrally to the facial nucleus (corresponding to area A5 in the rat). CA nerve terminals in the spinal cord mainly innervate the intermediolateral cell column. From these findings it is concluded that in the anesthetized cat the spinal component of the somato-sympathetic reflex is modulated by a descending tonic inhibition. This inhibition is independent of baroreceptor input. The pathways descend in the dorsolateral funiculus of the spinal cord, and it is suggested that they originate either in the cranial part of area A1 and/or area A5.

Animals↗
PubMed1981

[Vinyl chloride-induced angiosarcoma and hepato-cellular carcinoma of the liver (author's transl)].

Three patients with industrial exposure to PVC are described, who developed angio-sarcomas of the liver; in one patient this was combined with a multi-lobular primary hepato-cellular carcinoma. The epidemiology, clinical features and diagnosis are discussed, with particular reference to angiography, sonography and computerized tomography. The non-invasive methods, such as computerized tomography and sonography, are the techniques of choice if an angiosarcoma is suspected after long exposure to PVC.

Angiography↗
PubMed1981

[Computer tomography for tumours of the oesophagus and stomach (author's transl)].

The diagnostic scope of CT has been demonstrated for malignant tumours of the oesophagus (41 patients) and tumours of the stomach (18 patients). Of importance is the demonstration of circumferential spread of tumours of the oesophagus, the early demonstration of mediastinal lymph node metastases and the demonstration of infradiaphragmatic lymph node involvement from tumours of the middle and lower thirds of the oesophagus. In the presence of tumours of the stomach, it is possible to demonstrate infiltration of neighbouring organs (pancreas, spleen, hilum of liver) and haematogenous or lymphatic spread.

Adenocarcinoma↗
PubMed1981

[CT diagnosis of chronic osteomyelitis (author's transl)].

The CT findings in 20 patients with chronic osteomyelitis, mostly of post-traumatic origin, were compared with conventional radiographs and operative findings. CT diagnosed rather more sequestra than the conventional method. An important advantage of CT is the ability to demonstrate lesions in the medulla and infections in the soft tissues, eg. abscesses. CT should be reserved for cases where conventional methods with tomography leave unsolved problems, and in the present of fistulae.

Adult↗
PubMed1981

[Improved radiographic diagnosis of expanding lesions of the thoracic wall by computer tomography (author's transl)].

The findings of conventional radiography were compared with the results of computer tomography in 91 patients with histologically confirmed lesions of the thoracic wall. In 22 (24%) CT gave no additional information. In 67 (74%), CT supplied additional information or narrowed the differential diagnosis. Particularly important on computer tomography was the enhancement brought about by intravenous contrast medium in malignant tumours of the thorax or thoracic wall. CT should be used in preference to conventional tomography in the investigation of lesions of the thoracic wall.

Bronchial Neoplasms↗
PubMed1981

Computed tomography of the heart: ECG-gated and continuous scans.

Cardiac computed tomography (cardiac CT) and echocardiography provide noninvasive diagnosis of cardiac lesions by direct demonstration of the myocardium and the individual cavities of the heart. Myocardial thickness, and the size and shape of heart cavities are easily demonstrated. In patients with coronary heart disease proved by levocardiography, cardiac CT gave a true negative rate of 82.3% (echocardiography 82.9%) and a true positive rate of 90.8% (echocardiography 82.7%). In the assessment of coronary bypass graft patency, cardiac CT was accurate in 89.6% of studies confirmed by angiography.

Cardiomyopathies↗
PubMed1981

[Single-photon emission computed tomography (SPECT) of the liver with a rotating gamma camera system (author's transl)].

In a total of 202 patients conventional scintigraphy as well as emission computed tomography (SPECT) of the liver were performed. In 123 patients focal lesions could be excluded whereas in 30 cases the presence of liver tumors was verified. In 5 of the respective cases correct diagnosis was only possible by SPECT, in 9 further cases SPECT improved the diagnostic accuracy (topography, size and number of defects). In patients with normal findings of the liver, conventional scintigraphy yielded false-positive findings in 9 cases and SPECT in 7 cases. By combination of both methods the false-positive diagnoses could be reduced to 5. 48 patients had cirrhosis of the liver: in all of them conventional camera scintigraphy was superior to SPECT because of reduced activity accumulation in the liver (insufficient statistics).

Diagnosis, Differential↗
PubMed1981

[Effects of beam weakening and beam hardening on the measured CT values].

The present article reports on the effects of weakening and hardening of radiation on CT values in the environment of highly absorptive materials, using phantoms for carrying out these measurements. First of all, it was found with the help of geometrically simple phantoms (discs, circular rings), that the measured CT value of each volume element depends on the density distribution in the environment and that the CT values of homogeneous object layer are not uniform, but clearly dependent on the location at which measurement is effected. The standard deviation of the CT values of a homogeneous part of an object layer was also found to depend on the environment. Finally, using anatomically relevant phantoms, it was found that density value changes from max. +20 HU to -65 HU occur in the region of the cranium, whereas in the environment of the lumbar vertebra the density varies between max. +20 HU and -10 HU; in the pleural region, the maximum density variations are +/- 10 HU.

Humans↗