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Biomedical subjects

D Hassler

Publications and source records attributed to D Hassler.

52 records · Page 3Linked to original sources
PubMed1990

Value of in-line and out-of-line ultrasound targeting in extracorporeal shock wave lithotripsy.

Acoustic inhomogeneities of body tissue may deflect diagnostic ultrasound waves as well as therapeutic shock waves. The influence of incorrect ultrasound targeting and shock wave application due to these deflection effects has been examined quantitatively by means of a two-dimensional physical model. The accuracy of in-line and out-of-line targeting has been determined. Calculations on 2 stone patients show that in-line deflection effects remain below 2 mm, while they reach values up to 6 mm for out-of-line systems. These results, confirmed by first clinical observations done by others, indicate that in-line ultrasound targeting is superior to out-of-line targeting.

Acoustics↗
PubMed1987

[Is cardiac involvement found also in European erythema migrans borreliosis?].

During an infection with Borrelia burgdorferi two men (aged 59 and 61 years, respectively) developed long-lasting cardiac arrhythmias which proved difficult to treat (tachycardias; in one patient due to atrial fibrillation, and also nodal arrhythmias). The cardiac signs completely regressed after specific antibiotic treatment, supporting the view that the cardiac involvement was due to borrelia infection, as is known to have occurred with Lyme disease reported from the USA.

Arrhythmias, Cardiac↗
PubMed1987

[Systems theory of the ultrasound pulsed Doppler technic for measuring blood flow. I].

Part 1 presents the signal generation of an ideal pwDoppler system in the time and frequency domain using the means of the one-dimensional system theory. Problems of realisation are ignored, but tissue properties like absorption and scattering are taken into consideration. A comparison is made with pulse echo signals from tissue.

Blood Flow Velocity↗
PubMed1987

[Systems theory of the pulsed Doppler technic for blood flow measurement. II].

Following the discussion of the signal generation of an ideal pw Doppler system in the time and frequency domain using the means of the one-dimensional system theory in part 1 in this part 2 the main system parameters as resolution in space, and unambiguity ranges for space and velocity are explained and mathematical formula are derived for this.

Blood Flow Velocity↗
PubMed1984

[Systems theory of ultrasound pulse echo technic (1)].

The properties of diagnostic pulse echo systems, independent of instrument characteristics (ideal system) are analysed in Part 1 and it is shown in Part 2 how they are modified by "typical" instrument parameters. A simplified block diagram of an ideal system is analysed in the time and frequency domain by means of the one-dimensional system theory. The terms dynamic range, maximum penetration depth and amplitude resolution are explained.

Humans↗
PubMed1984

[Systems theory of ultrasound pulse echo technic (2)].

Part two explains the terms, spatial resolution, range ambiguity and maximum frame rate of diagnostic pulse echo systems. Then the idealised system described in part one is completed by incorporating various band pass filters, which represent the effects of resonant piezoelectric transducers and electric filters of the TGC amplifiers. The influence of such band limiting components on spatial resolution and dynamic range are shown by numerical examples. Mathematical derivations are restricted to the necessary minimum and all formulae are illustrated by means of a substantial number of graphs.

Humans↗
PubMed1982

[Measurement of blood flow velocity, blood volume flow and arterial cross section using the integral Doppler ultrasonic method--comparison and synthesis of two solutions].

Starting with a short comparison of the space resolving, pulsed Doppler method with the integral Doppler techniques for blood flow measurement, the formula is derived, after which the profile independent cross-sectional mean velocity v is to be measured using the integral method. When evaluating the Doppler signal power, moreover, volume flow Q can be measured. Two versions of the integral method for volume flow Q, one with (WAVUD) and the other without (WUVUD), and the need for a separate determination of the angle of incidence are explained and compared. Combination of the two results in a new method for measuring the mean velocity v and cross-sectional area F of blood flow from one single sound direction, without the need for determining the angle of sound incidence into the artery. The main problems of the integral method are addressed and in vitro test results are reported, showing that 20% measurement accuracy should be practical in vivo.

Arteries↗
PubMed1982

[Measuring blood flow velocity, blood volume flow and arterial diameter using integral Doppler ultrasound--comparison and synthesis of 2 solutions].

Starting with a short comparison of the space resolving, pulsed Doppler method with the integral Doppler techniques for blood flow measurement, the formula is derived, after which the profile independent cross-sectional mean velocity v is to be measured using the integral method. When evaluating the Doppler signal power, moreover, volume flow Q can be measured. Two versions of the integral method for volume flow Q, one with (WAVUD) and the other without (WUVUD), and the need for a separate determination of the angle of incidence are explained and compared. Combination of the two results in a new method for measuring the mean velocity v and cross-sectional area F of blood flow from one single sound direction, without the need for determining the angle of sound incidence into the artery. The main problems of the integral method are addressed and in vitro test results are reported, showing that 20% measurement accuracy should be practical in vivo.

Arteries↗
PubMedDate not supplied

Cefotaxime versus penicillin in the late stage of Lyme disease--prospective, randomized therapeutic study.

The low responsiveness of Lyme arthritis to high dose intravenous penicillin G therapy has evoked the demand for new drugs for the treatment of late stage borreliosis. As can be deduced from in vitro susceptibility data, third generation cephalosporins are far more effective on Borrelia burgdorferi spirochetes than penicillin G. The study presented here was designed to compare cefotaxime at a dosage of 2 x 3 g/day with penicillin G at a dosage of 2 x 10 megaunits/day, for ten days in a prospective randomized trial. A total of 135 patients were included in the study. They were diagnosed to suffer from late stage Lyme borreliosis on the basis of defined clinical symptoms compatible with stage three borreliosis manifestations of at least six months' duration and positive antibody titers against B. burgdorferi. Final outcomes were recorded after a 24 month post-treatment observation period with re-examination at three-month-intervals. Cefotaxime proved to be significantly superior to penicillin G with 87.9% versus 61.3% of treatments resulting in full or incomplete remission of symptoms (p = 0.002). Clinical remission was accompanied by declining antibody titers. Herxheimer-like reactions were observed in 20% of the patients of the penicillin group and in 40.5% of the patients of the cefotaxime group and may be interpreted as an indication of a response to therapy.

Adolescent↗
PubMedDate not supplied

Evaluation of the detection of Borrelia burgdorferi DNA in urine samples by polymerase chain reaction.

It is difficult in some cases to identify an infection caused by Borrelia burgdorferi and to monitor the effect of therapy. Seropositivity will persist even after successful treatment and therefore may suggest ongoing infection. For direct detection of B. burgdorferi DNA in human urine samples, the polymerase chain reaction (PCR) was evaluated. A published primer system was selected, which amplifies a 259 bp fragment from the gene encoding the 23S rRNA. The lower detection limit of the primer system was 10 fg of extracted B. burgdorferi DNA. Several methods for the pretreatment of urine samples were tested. Of these, the Geneclean kit (Bio 101, USA) showed the best results. A total of 114 urine samples from 74 patients belonging to three clinical groups was investigated: (i) 51 samples from 26 patients with active Lyme disease, (ii) 36 samples from 27 patients with previous infection but no symptoms at the time the urine was collected, and (iii) 27 samples from 21 seronegative control patients without Lyme disease. B. burgdorferi DNA was detected in 25 urine samples of 17 patients with active disease, whereas 26 samples from this group of patients were negative. Only one asymptomatic case with previous infection showed a positive result, and the urine samples of the patients without Lyme disease were uniformly negative. Two of four patients from whom samples before and directly after onset of therapy were available converted from negative to positive PCR results after initiation of therapy, accompanied by the symptoms of a Jarisch-Herxheimer reaction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗