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Biomedical subjects

K Lackner

Publications and source records attributed to K Lackner.

At least 109 records · Page 6Linked to original sources
PubMed1992

[Interstitial lung diseases. A comparative study between a film-screen combination and a digital storage phosphor technic].

Chest examinations were carried out in 60 individuals using film-screen and digital storage phosphor techniques and identical radiation doses. 29 of these individuals were patients with interstitial pulmonary disease; 31 were normals. Postprocessing of the digital images was carried out with filtering using an unsharp mask and identical parameters for all patients. An ROC analysis using 10 observers showed no significant difference in the evaluation of the interstitial lung disease. Correlation analysis showed a significant positive correlation (p less than 0.001) for the findings in both techniques. Under the present circumstances, film-screen and digital storage phosphor technique are of equal value in the diagnosis of interstitial pulmonary disease.

Adult↗
PubMed1992

[The value of digital subtraction sialography compared to conventional sialography, salivary gland sonography and surgical findings].

In a prospective study DSA sialography, conventional sialography (100mm technique) and sonography of the salivary glands were performed in 124 patients. The results of imaging could be correlated with those of operation and/or histology in 70 patients. Performing sialography in only one projection DSA sialography is superior to the conventional technique. The results of DSA are equivalent to those of conventional sialography in more than one projection. DSA sialography is the method of choice demonstrating salivary calculi, whereas sonography is superior to DSA sialography in the detection of tumors. In the diagnosis of chronic inflammation of the salivary glands DSA is slightly superior to the other imaging modalities.

Adolescent↗
PubMed1992

[Pharmacokinetics of gadolinium-DTPA in chronic renal insufficiency requiring dialysis].

MRT with gadolinium-DTPA (0.1 mmol/kg body weight) was performed in 10 patients with renal insufficiency requiring dialysis and the clearance of gadolinium-DTPA was studied. After 3 dialysis on 3 successive days more than 97% of the initial concentration of gadolinium-DTPA had been eliminated. Average half-life was 1.87 hours. There were no side effects in any of the patients. Close laboratory observation of liver function showed no significant changes during the period of study. No contra-indication for the use of this contrast medium in patients with renal insufficiency requiring dialysis was found during this study.

Adult↗
PubMed1992

[The determination of myocardial mass by cardiac magnetic resonance tomography. The effect of section alignment and section distance].

The effect of section alignment and distance in volumetric determination of myocardial mass by means of cardiac magnetic resonance imaging (MRI) was studied in 19 isolated pig hearts. Double angulated views taken through the short axis of the heart with a slice thickness of 10 mm and slices at a distance of 0 mm, 1 mm, 3 mm and 5 mm produced accurate left ventricular measurements with cardiac MRI. Measurements in the long axis of the heart resulted in a marked underestimation of myocardial mass; depending on slice intervals, there was an error between 13% and 20%. In vivo measurements in 35 subjects confirmed the effect of section alignment. Measurements in the long axis of the heart produced results of 139.9 +/- 31.7 g, significantly less than measurements in the short axis of the heart of 157.8 +/- 32.3 g.

Adult↗
PubMed1992

[The direct measurement of the spin-grid-relaxation times of phosphorus metabolites in the human myocardium].

The T1 relaxation times of the phosphorus metabolites in human heart muscle measurable by 31P-MR spectra were determined in 12 individuals using a 1.5 Tesla system. Several spectra were recorded consecutively with a pulse repetition time of 1.6 s to 24 s. The T1 times of creatine phosphate (CP), of gamma-, alpha-, beta-adenosintriphosphate (ATP), 2,3-diphosphoglycerate (2,3-DPG) together with anorganic phosphate) and phosphodiester (PDE) showed mean measurements of 6.1 +/- 0.5, 5.4 +/- 0.5, 5.0 +/- 0.5, 5.8 +/- 1.0, 7.6 +/- 1.0, and 5.0 +/- 1.0 s (M +/- SE). The accuracy of the ISIS technique was tested with a special phantom. T1 times were also measured in standard solutions (20 mM CP, 10 mM ATP); CP was 8.7 +/- 0.2 s and gamma-ATP was 9.9 +/- 0.7 s. Corrections for partially saturated 31P-MR spectra--at least for CP/ATP ratios--are relatively small.

2,3-Diphosphoglycerate↗
PubMed1992

31P magnetic resonance spectroscopy in dilated cardiomyopathy and coronary artery disease. Altered cardiac high-energy phosphate metabolism in heart failure.

BACKGROUND: The purpose of this work was to further define the value of cardiac 31P magnetic resonance (MR) spectroscopy for patients with coronary artery disease and dilated cardiomyopathy. METHODS AND RESULTS: Blood-corrected and T1-corrected 31P MR spectra of anteroseptal myocardium were obtained at rest using image-selected in vivo spectroscopy localization, a selected volume of 85 +/- 12 cm3, and a field strength of 1.5 T. Nineteen volunteers had a creatine phosphate (CP)/ATP ratio of 1.95 +/- 0.45 (mean +/- SD) and a PDE/ATP ratio of 1.06 +/- 0.53; in four patients with left anterior descending coronary artery (LAD) stenosis, six patients with chronic anterior wall infarction, and four patients with chronic posterior wall infarction, CP/ATP and phosphodiester (PDE)/ATP ratios did not differ from those in volunteers. Twenty-five measurements of 19 patients with dilated cardiomyopathy yielded a CP/ATP of 1.78 +/- 0.51 and a PDE/ATP of 0.98 +/- 0.56 (p = NS versus volunteers). When these patients were grouped according to the severity of heart failure, however, CP/ATP was 1.94 +/- 0.43 in mild (p = NS versus volunteers) and 1.44 +/- 0.52 in severe DCM (p < 0.05), respectively. No correlation was found between CP/ATP and left ventricular ejection fraction or fractional shortening, but correlation of CP/ATP with the New York Heart Association (NYHA) class was significant (r = 0.60, p < 0.005). Six patients with dilated cardiomyopathy were studied repeatedly before and after 12 +/- 6 weeks of drug treatment leading to clinical recompensation with improvement of the NYHA status by 0.8 +/- 0.3 classes. Concomitantly, CP/ATP increased from 1.51 +/- 0.32 to 2.15 +/- 0.27 (p < 0.01), whereas PDE/ATP did not change significantly. CONCLUSIONS: Cardiac high-energy phosphate metabolism at rest is normal in LAD stenosis and chronic myocardial infarction in the absence of heart failure. The CP/ATP ratio has low specificity for the diagnosis of dilated cardiomyopathy. However, CP/ATP correlated with the clinical severity of heart failure and may improve during clinical recompensation.

Adult↗
PubMed1991

[The diagnostic assessment of enlarged lymph nodes by the qualitative and semiquantitative evaluation of lymph node perfusion with color-coded duplex sonography].

Perfusion of enlarged lymph nodes by colour-coded sonography was studied prospectively in 105 benign and 115 malignant lymph nodes. The diagnosis was confirmed histologically in 158 and clinically in 62. Spectral analysis in the benign lymph nodes provided normal values for pulsatility and resistance indices. A pulsatility index greater than = 1.8, or a resistance greater than = 0.9 indicate lymph node metastases with positive prediction of 93% and specificity of 97%. In addition, subjective, semiquantitative classification of lymph node perfusion in relation to the surrounding fat or connective tissue improves the diagnosis of lymph node metastases and of malignant lymphomas.

Axilla↗
PubMed1991

[Vascular diagnosis with color-coded duplex sonography. A cost-benefit analysis].

In a retrospective study over two years, the costs of 2909 CCDS examinations were compared with 1893 digital subtraction angiograms. The cost of each CCDS examination was calculated as 147 DM and each DSA examination with intra-arterial contrast medium, or for shunt angiography was 709 DM. By using CCDS, it was possible to reduce the cost of angiographic examinations by 177,000 DM per year.

Angiography, Digital Subtraction↗
PubMed1991

[Color-coded duplex sonography of the extracranial arteries supplying the brain: diagnostic significance and sources of error in comparison with i.a. DSA].

The findings of color Doppler flow imaging of the extracranial cerebral arteries in 75 patients were compared with i.a. DSA. Carotid stenoses greater than 50% and carotid occlusions were shown by sonography with a sensitivity of 91% and a specificity of 97%. The severity of the stenosis was in agreement in 88% of cases using the two methods. Sonography of the vertebral arteries achieved a sensitivity of only 65% and a specificity of 88%. Sonographic examination of the ophthalmic artery in order to demonstrate carotid stenosis achieved a sensitivity of only 29% and provided no additional information. Retrobulbar kinking of the ophthalmic artery was found in 30/178 vessels and may be a cause of misinterpretation.

Angiography, Digital Subtraction↗
PubMed1991

[In vivo 31P-cardiac magnetic resonance spectroscopy: methods and the first clinical results].

31P-magnetic resonance (MR) spectra of the heart can be obtained from well-defined myocardial regions by combined MR imaging and variable selected volumes for spectroscopy. 31P-spectra of 33 volunteers and of 43 patients with dilated and hypertrophic cardiomyopathy and with coronary artery disease were quantified using a curve-fitting routine. To optimize our technique, we recorded unsaturated and partially saturated spectra in several volunteers. Relative peak areas and signal-to-noise ratios showed significant changes with varying pulse repetition times. Saturation factors were applied to correct spectra from volunteers and patients for the effects of partial saturation. Under resting conditions, peak areas of volunteers and patients from the various groups were statistically indistinct.

Adult↗
PubMed1991

Quantification of vascular stenosis with color Doppler flow imaging: in vitro investigations.

The accuracy of quantifying the degree of vascular stenosis with color Doppler flow imaging (7.5-MHz, linear array system) was determined in an experimental study carried out on six concentric and five eccentric model stenoses (cross-sectional area reduction, 13.4%-93.8%). The measurements were made with use of pulsatile flow at four different flow rates (70.8-339.0 mL/min). The degree of stenosis was calculated from the ratio of prestenotic to intrastenotic flow velocity. The most exact measurement of the degree of stenosis could be achieved with Doppler spectral analysis by determining the maximum peak systolic velocity (r = .994, y = 0.98x - 3.2). With the velocity values derived only from the color-coded image, it was also possible to find the most exact degree of stenosis (r = .995, y = 0.99x - 2.9). For quantification of stenosis, pre- and intrastenotic Doppler spectral analysis is no longer necessary if the stenosis can be imaged sufficiently with color Doppler.

Blood Flow Velocity↗
PubMed1991

[4 years' experience with a balloon-expandable endoprosthesis. Experimental and clinical application].

During a 4-year period of clinical application of the balloon-expandable Palmaz stent, a randomized trial comparing stent implantation and traditional balloon angioplasty of iliac arteries in arterial occlusive disease was started. The first long-term results, recorded after 2 years, indicate statistically significant differences in the complication rate (after stenting 2/62 and after angioplasty 5/69) and patency (greater than or equal to 70% of original lumen size upon stent implantation or balloon inflation: 95% after stenting and 72% after angioplasty). Clinical improvement after 2 years was 89% after stenting and 70% after angioplasty. Parallel to the clinical trials, experimental canine artery stenting was performed to evaluate differences in the long-term patency of stents exposed to restricted flow. Significant differences in neointimal healing were found between normally perfused stents and stents with artificially reduced flow: during the total observation period of 6 months the neointimal height was up to 200% higher in flow-restricted stents, while the histological composition of the neointima was the same as with normally perfused stents.

Angioplasty, Balloon↗
PubMed1991

[A ROC analysis for comparing contrast perception in grey scale reversal of digital images].

Based on ROC (receiver operating characteristic) analysis, contrast perception by eight physicians engaged in x-ray diagnostics for different lengths of time was examined in respect of inversion of grey scale values of digital x-ray film images. The ROC analysis showed a significantly superior contrast perception for imaging by the negative mode (bones white) than by the positive mode (bones black). With r* = + 0.61 a positive correlation was obtained between the period of the physicians' activity in x-ray diagnostics and the difference between the areas below the ROC curves for both imaging modes. Hence, the negative mode is to be preferred for diagnostic work based on digital x-ray film images.

Humans↗
PubMed1991

[Experimental and clinical possibilities of MR spectroscopy of the heart].

MR-spectroscopy of the heart is a relatively new technique for the study of various aspects of cardiac metabolism. The majority of results has so far been obtained with the isolated perfused heart. Here, 31P-MR spectroscopy can be employed to measure high-energy phosphate metabolism and intracellular pH repeatedly and non-invasively. Using a technique called saturation transfer, velocities of enzymatic reactions, such as the creatine kinase reaction, can be measured. Intra- and extracellular Na+ and K+ concentrations can be registered with 23Na- and 39K-MR in conjunction with shift reagent. 13C-MR can be used to tackle carbohydrate metabolism. In-situ-R-spectroscopy allows determination of high-energy phosphates in intact large mammals. Clinical applications of MR-spectroscopy remain to be defined; preliminary results indicate high diagnostic and prognostic potential for patients with coronary artery disease and congestive heart failure.

Animals↗