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Biomedical subjects

P Fritschy

Publications and source records attributed to P Fritschy.

16 recordsLinked to original sources
PubMed1988

[Intravenous digital subtraction angiography of the lower extremities combined with step translation (2-field DSA)].

We evaluated a bolus-chase technique designed to reduce the volume of contrast material and to shorten examination time during intravenous digital subtraction angiography (IV-DSA) of the lower limbs. With this technique, after a single injection of contrast material, two contiguous fields can be sequentially imaged (two-field DSA) using a step translated x-ray tube. 67 patients with peripheral vascular disease were studied. All examinations provided diagnostic information, so that in no instance additional intra-arterial injections were required. With the two-field DSA only 3.49 injections were needed in the average for five fields examined in each patient, resulting in a 30% reduction of contrast agent used.

Adult↗
PubMed1987

[Intravenous digital subtraction angiography].

Thanks to its high contrast resolution, intravenous digital subtraction angiography (IV-DSA) makes it possible to examine the arteries after injection of contrast media into a peripheral arm vein. IV-DSA is indicated in patients with clinical suspicion of arterial stenosis, occlusion, aneurysm or anomaly (ascending and descending aorta, aortic arch and its great vessels, and the renal, iliac, femoral and popliteal arteries). In many such patients, IV-DSA successfully replaces intraarterial catheter angiography. The advantages of IV-DSA (with a peripheral injection technique) as compared to conventional angiography, include its non-invasive character, a lower complication rate and less discomfort for the patient. The disadvantages of IV-DSA include poorer image quality due to lower concentration of contrast media in the vessels, reduced spatial resolution and the need for larger volumes of contrast media. The indication for conventional angiography is an inconclusive intravenous study due to motion artifacts and/or poor resolution.

Analog-Digital Conversion↗
PubMed1987

[Peripheral venous and peripheral arterial digital subtraction angiography in occlusive diseases of the lower extremity].

The possibility of employing peripheral venous and peripheral arterial digital subtraction angiography was examined in 351 patients of 65 to 95 years of age with arterial occlusive disease of the lower extremity. After peripheral venous contrast medium injection (using a Venflon needle 1.7-2.0 mm, 40 ml nonionic contrast medium, 20-30 ml NaCl, flow 15/s), conclusive assessment of vascular tone is possible in 86% of the cases. Indication for IV DSA is supplied chiefly by stenoses and occlusions situated proximally or bilaterally in the region of the distal aorta abdominalis, the iliacal, femoral and popliteal arteries. The distal adjacent segment is demonstrated well in 81 to 95 per cent of the cases up to the level of the trifurcation. Image quality is poor in 30% of the images of the lower leg, whereas no assessment is possible in 11% of the cases. IA DSA with fine needle (needle 0.8 mm, 3-5 ml contrast medium, 3-7 ml NaCl) is indicated in 8% of the patients to clarify the distal lower leg arteries, especially in preceding extensive proximal vascular occlusions. Conventional angiography can be largely replaced by combining peripheral venous and peripheral arterial DSA with fine needle technique.

Aged↗
PubMed1986

[Results of digital subtraction angiography in children and adolescents].

In 43 children and adolescents, DSA was carried out, in 29 cases by the intravenous and in 17 cases by the intra-arterial route. IV-DSA was usually performed by putting a cannula (14 to 18 G) into the antecubital vein (bolus injection of 5 to 40 ml. of contrast and 5 to 20 ml. saline at 2 to 12 ml./sec.). The indication for IV-DSA is the investigation of congenital cardio-vascular abnormalities (stenosis or atresia of the pulmonary artery, anomalies of the pulmonary veins or the aortic arch and following vascular surgery). In these cases the more invasive heart catheter examinations can be avoided. IA-DSA is performed with a catheter with a fine lumen (4 to 5 F), diluting the contrast with an equal amount of saline. The advantage of IA-DSA is that it is less invasive, uses less contrast and provides better contrast and detail.

Adolescent↗
PubMed1986

[The coding of roentgen diagnostic findings of studies based on morphologic structural changes. A computer assisted archive system for scientific purposes].

For the last three years our Institute has been using a system based on a microcomputer for archiving scientifically interesting findings. This computer processes data obtained via computed tomography, sonography and angiography. Besides the coding of examination findings the system also enables compilation of efficiency statistics data. The system can be extended with comparatively little effort for processing MR data as well. Coding is not effected, as in most of the generally used systems, according to diagnosis, but according to the pathological change that can be detected via x-ray film. This prevents erroneous coding due to erroneous evaluation of the finding in question. The examinations can be stored immediately without waiting for verification. Search for defined findings is effected via screen where a search profile is set up interactively. Due to the hierarchic structure of code allocation it is possible to call for more or less detailed findings from the stored data.

Angiography↗
PubMed1986

Description of flow phenomena in magnetic resonance imaging.

The magnetic resonance (MR) signal from the hydrogen nuclei of blood is not only determined by the MR parameters T1, T2 and proton density, but is strongly dependent on the movement of the protons. Magnetic resonance imaging (MRI) offers therefore the possibility to visualize the distribution of moving spins, especially blood flow, noninvasively and without contrast agents; moreover, the velocity of the moving spins can be quantified. Flow phenomena in MRI are a pretentious field because the complicated hydrodynamics of the living system is coded in the MR signal; therefore, an understanding of the underlying physical principle of the MR signal is required to interpret and extract flow information from the image. However, rather simple theoretical and experimental models of fluid transport in vessels allow to explain the main features of various effects observed in images.

Blood Circulation↗
PubMed1985

Combined use of magnetic resonance imaging (MRI) and spectroscopy (MRS) by whole body magnets in studying skeletal muscle morphology and metabolism.

As a pilot study, 31-P-spectra of the quadriceps femoris muscle (1.5T) and proton images of the right thigh (.5T) were performed in two cyclists (T) and two untrained (UT) subjects. During ischemia, while MRI did not show any change, phosphocreatine (PCr) concentration decreased and inorganic phosphate (Pi) increased. Recovery occurred within 3 minutes. Ergometric bicycle tests were performed outside the magnet. Submaximal workload (UT 150W/T 260W, 3.5 minutes) caused transient minimal changes in phosphorus metabolites. Supramaximal, partially anaerobic exercise (UT 320W/T 350W, 3.5 minutes) induced similar changes in heart rate, oxygen uptake rate, and plasma lactate in both groups. Decrease of the PCr/Pi ratio, however, was more pronounced in UT subjects and clearly lasted longer. If methodical problems can be resolved, combined MRS and MRI in whole body magnets may become a standard noninvasive modality, adding unique information on morphology (organ volume) and local metabolism to classic mechanical and global physiologic data.

Adult↗
PubMed1984

[A new model for the quantitative analysis of left ventricular regional function].

A computer-assisted model for quantitative analysis of left ventricular segmental wall motion is presented. In contrast to standard rectangular and radial chord methods, no coordinate and reference system is used. Normal wall motion of 5 ventricular segments in the RAO projection was evaluated in 20 patients with normal ventriculograms. Segmental wall motion abnormalities after myocardial infarction were then analyzed by the computer-assisted method in 60 patients and the results compared with the visual assessment of an experienced cardiologist as standard reference. 96% of all segments with normal motion, 95% of all hypokinetic segments and 100% of all dyskinetic segments were correctly identified by computer analysis. Akinesia, however, was detected only in 25% of all cases and misinterpreted chiefly as hypokinesia. Further refinement of the software should improve detection of akinesia and classification of hypokinesia.

Adult↗
PubMed1983

Measurement of liver volume by ultrasound and computed tomography.

A morphometric method to calculate liver volumes from transverse sections is evaluated (point-integrating method). In the first part of the study, 10 liver specimens were investigated by computed tomography (CT) and ultrasound (US); the calculated volumes were compared to the volumes obtained by water displacement of the organs. While CT showed an ideal agreement (r = 0.994), volumes calculated from US sections correlated less well (percentage differences from +12.5% to -9%, r = 0.915). In the second part of the study, the livers of 10 randomly selected patients were investigated by CT and US. Liver volumes were calculated using the point-integration method. Compared to the CT examination, US results show a good correlation with a correlation coefficient of r = 0.977. The point-integration method is very valuable to measure organ volumes from transverse sections. The method can be applied "offline" to photographic films, data do not have to be recorded electronically. The time required to calculate the volume of an organ is comparable to other methods.

Humans↗
PubMed1983

[Practical problems of determining liver volume from computed tomographic transverse sections].

The article confronts the traditional methods of volume calculation ("layer method"); addition of partial volumes derived from the thickness of the individual strata and their area) with a new method of including the longitudinal extension of the liver into the calculations ("topographic method"). Using a model of a liver with defined volume as basis (continuous examination every 8 mm.), various constellations of layer sequence to be expected in CT practice, are simulated and the volumes calculated from the changed data by means of both methods. It has been found that calculation of volume according to the topographic method is superior to the layer method if the respiratory position of the patient changes from layer to layer during an examination and/or if the distances between the individual layers are irregular in the course of an examination. Recommendations are given for the procedure to be followed during CT examination carried out for computing the liver volume, and for a liver volume calculation to be based on a CT examination which has already been performed.

Adult↗
PubMed1983

[Computer tomographic densitometry of the normal vertebral body spongiosa].

The absorption values of cancellous bone of the third lumbar vertebral body were measured in 80 patients by CT. It was possible to demonstrate a statistically significant linear correlation between absorption values and patient age. The older the patient, the lower the average absorption values of cancellous bone. The average absorption values in patients between 20 and 30 Jrs. were found to be about 200 HU, between 30 and 50 Jrs. 180, between 60 and 70 Jrs. 120 and between 70 and 80 Jrs. 100 HU. Although correlation between calcium salt content and absorption of bone under CT are well known, there are other factors (mainly fatty involution of bone marrow) who influences the absorption behaviour of cancellous bone.

Absorptiometry, Photon↗
PubMed1981

[A semi-quantitative programme for evaluating radio-ventriculograms by a "first passage" technique (author's transl)].

Evaluation depends mostly on the demonstration of regional function (muscle movement, regional contraction volume, trend scintigram). A special technique permits the demonstration of insufficiency of the A-V valves and its approximate measurement. Comparison with single plane angiography showed good or excellent agreement concerning the ejection fraction (r = 0.86 for patients in sinus rhythm, 0.92 for patients without valvular disease). Inter observer error is very small (r = 0.99). These studies can be evaluated separately for the right and left ventricles (in an RAO 30 degrees projection).

Adult↗