PubMed Health⌕ Search

Biomedical subjects

K Lackner

Publications and source records attributed to K Lackner.

At least 109 records · Page 6Linked to original sources
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↗
PubMed1990

Collateral pathways in portal hypertension.

In a retrospective study angiographic image material of percutaneous direct portographies carried out in 43 patients was evaluated according to anatomic and radiologic criteria. These examinations were performed for therapeutic purposes (embolisation of vessels supplying varices). All the hepatofugally perfused veins were analyzed according to their localisation and course. Apart from the known portocaval collateral pathways a number of other collaterals not yet described could be documented by means of angiography.

Aged↗
PubMed1990

[Gadolinium-DTPA as an oral contrast medium for MR tomography of the abdomen].

150 MR examinations of the upper abdomen were carried out after the oral administration of 5 ml/kg body weight of a gadolinium DTPA formulation (1.0 mmol/l, 15 g/l mannitol), with reference to the delineation of the pancrease, the liver and intra-abdominal fat. For comparison, 100 MR examinations without oral opacification of the G.I. tract were evaluated. Contrast administration resulted in a signal-intensive demonstration of the G.I. tract for all measurement sequences. The intraluminal contrast improved the distinction between normal and abnormal structures. T1 and T2 sequences and the demonstration of fat on T2-weighted series. T1-weighted series showed the best diagnostic results. In 25% there was meteorism and diarrhoea within 24 hours of the administration of the oral contrast.

Abdomen↗
PubMed1990

[The value of color-coded duplex sonography of a dialysis shunt].

Two hundred and sixty-four shunt segments in 43 patients with 66 dialysis shunts were examined by colour-coded duplex sonography and the results compared with DSA. Sonography demonstrated shunt stenoses with an accuracy of 93.9% (sensitivity 90.6%, specificity 95.8%). Only central venous stenoses were shown better by DSA than by sonography. Sonography showed occlusions with a sensitivity of 83.3% and a specificity of 100%. All aneurysms demonstrated by DSA were correctly identified by sonography. In 18 patients PTA of the shunt was performed. The result of treatment could be quantified by measuring flow by means of sonography. The study confirmed the value of duplex sonography as a noninvasive diagnostic method for investigating insufficient dialysis shunts.

Adult↗
PubMed1990

[Dilatation and balloon-expandable stents for the treatment of central venous stenosis in dialysis patients].

On 10 dialysis patients we performed 12 balloon dilatations, 2 catheter lyses, 6 stent implants (Palmaz stent) and one atherectomy of central venous stenoses or occlusions (v. subclavia, v. brachiocephalica) at the shunt arm of the patient. The primary success rate was, in balloon PTA and lysis, 12/14 interventions, and in stent placement and atherectomy 7/7. The angiographical and clinical primary result after stent implantation was significantly better than after conventional dilatation. After 66% of the balloon dilatations recidivation occurred within the first year; this can be treated by means of repeated PTA. Whether long-term exclusion of recurrence can be achieved by stent implantation, must be established by means of follow-up studies that are at present in progress.

Adult↗
PubMed1990

[Color-coded duplex sonography before and after PTA of the arteries of the lower extremities].

The value of color-coded duplex sonography in the pelvic and lower limb arteries was studied prospectively in 52 patients and the findings were compared with intra-arterial DSA. There was high diagnostic accuracy (sensitivity 91.7%, specificity 98.9%) for the demonstration of vascular abnormalities. In 84.3% of cases a correct diagnosis could be obtained based entirely, or largely, on the color-coded signal. Both before and after PTA color-coded duplex sonography is a non-invasive method that is superior to conventional duplex sonography.

Angiography, Digital Subtraction↗
PubMed1990

[Magnetic resonance tomography (MRT) of the hand in chronic polyarthritis].

Forty hands of 39 patients with rheumatic joint disease were examined by MRT. The method differentiates between inflammatory exudative and proliferative processes in soft tissues and bone. T2-weighted images provided criteria for judging the activity of the disease. MRT provided better demonstration of the soft tissues than just conventional radiography. The methods were of equal value for showing bone lesions. MRT is suitable as a means of diagnosing rheumatoid changes in the hand.

Adult↗
PubMed1990

[Indications for cardio-MRT].

Cardio-MRT provides complex diagnostic information (morphology, function, biochemistry) with little stress for the patient and is therefore used increasingly for clinical diagnosis. There is great need for interdisciplinary studies concerning function, the use of contrast media and spectroscopy.

Animals↗
PubMed1989

[Imaging properties of digital image-intensifier radiography compared to the conventional x-ray technic for chest pictures].

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.

Adolescent↗
PubMed1989

[In vitro measurement of intravascular blood flow with color Doppler sonography].

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.

Blood Flow Velocity↗