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Biomedical subjects

R Veit

Publications and source records attributed to R Veit.

11 recordsLinked to original sources
PubMed1997

Effective doses to members of the public from the diagnostic application of ionizing radiation in Germany.

The exposure of the German population to man-made radiation results mainly from diagnostic X-ray and nuclear medical examinations. Data are presented about the annual frequency and the average dose of the various examination types for West Germany in the years 1990-1992. According to these data a yearly average of approximately 1550 diagnostic examinations using ionizing radiation were performed per 1000 inhabitants resulting in an annual per caput effective dose of 1.9 mSv. Despite the frequent use of alternative examination techniques, such as sonography, nuclear magnetic resonance and endoscopy, the frequency of X-ray and nuclear medical examinations is still increasing. If collective risk assessments are done using the per caput effective dose, at least the age distribution of the patients must be considered. This leads to a "risk-modifying factor" of 0.6-0.7 for patients to be applied to the ICRP risk coefficient of 5 % per Sv valid for the general population. However, radiation risk must always be viewed in context with disease- and therapy-related risks and balanced against the benefit of the diagnostic examination, which should always exceed the risk for a well-indicated procedure.

Adolescent↗
PubMed1997

Differential beta- and alpha-adrenergic activation during psychological stress.

The responsivity of several cardiovascular indices to a computerized mental arithmetic stress and a cold pressor stress were investigated in 22 healthy adult subjects. The major findings were that the largely beta-adrenergically driven T-wave amplitude, pre-ejection period, R-wave to pulse interval, and left ventricular ejection time values responded only to mental arithmetic; a significant decrease in cardiac output and increase in peripheral resistance were elicited during the cold pressor test; inter-beat-interval and subjective stress ratings responded significantly to both stresses compared to baseline levels, but more intensely to mental arithmetic than the cold pressor test; blood pressure, stroke volume and the maximum of the first derivative of the raw impedance signal responded unspecifically to both stresses. These findings support the idea that cardiovascular responses to psychological challenge depend on the level of cognitive processing required for the task. In addition, the superfluity of multiple variable measurements to study cardiovascular reactivity in such situations is discussed.

Adult↗
PubMed1997

Somatotosensory evoked potentials during baroreceptor stimulation in chronic low back pain patients and normal controls.

Nineteen chronic low back pain patients (aged 19-63) and 17 controls (aged 20-41) received electrical pain stimuli during manipulation of their carotid baroreceptors. The non-invasive mechanical manipulation of baroreceptors, using the PRES technique (Phase Related External Suction), simulates the end-effects of phasic blood pressure changes. This technique was developed to assess pain responses induced by changes in blood pressure without the typical shortcomings of pharmacological manipulation or lack of a control condition. During maximum baroreceptor activity, there was an unexpected increase in the amplitude of the somatosensory evoked potentials (SEPs) elicited by the electrical pain stimuli condition (N150-P260 peak-to-peak). In most other studies the opposite effect was found, with decreased pain responses during maximum baroreceptor activity. The chronic pain group reported greater pain during highest baroreceptor activation than did the controls. In addition, the chronic pain group showed lower diastolic blood pressure. To determine whether pain and baroreceptor responses observed in the chronic pain group depended on lower blood pressure levels, a second experiment with a non-clinical sample was performed. Results showed that lower tonic blood pressures are associated with greater baroreceptor activity amplifying pain, while higher blood pressure is associated with pain dampening during high baroreceptor activity. Data suggested that the differences in pain responses found in low back pain patients were associated with their lower tonic blood pressure levels. It is proposed that in general, lower blood pressures may be associated with greater pain during baroreceptor activation.

Adolescent↗
PubMed1988

The construction of computer tomographic phantoms and their application in radiology and radiation protection.

In order to assess human organ doses for risk estimates under natural and man made radiation exposure conditions, human phantoms have to be used. As an improvement to the mathematical anthropomorphic phantoms, a new family of phantoms is proposed, constructed from computer tomographic (CT) data. A technique is developed which allows any physical phantom to be converted into computer files to be used for several applications. The new human phantoms present advantages towards the location and shape of the organs, in particular the hard bone and bone marrow. The CT phantoms were used to construct three dimensional images of high resolution; some examples are given and their potential is discussed. The use of CT phantoms is also demonstrated to assess accurately the proportion of bone marrow in the skeleton. Finally, the use of CT phantoms for Monte Carlo (MC) calculations of doses resulting from various photon exposures in radiology and radiation protection is discussed.

Bone Marrow↗
PubMed1986

[Which antibiotics should one choose for prophylaxis in vascular surgery?].

Although the principle and duration of prophylactic antibiotic therapy in prosthetic vascular surgery are fairly widely accepted, the choice of antibiotic is still open to discussion. During two successive periods, identical groups of patients received peri-operative prophylaxis with, during period I (455 cases) oxacillin alone and during period II (537 cases) combined treatment with oxacillin and amikacin. The aim of the study was to evaluate efficacy of the association and to draw general conclusions on choice of antibiotic. The addition of amikacin reduced frequency of infection in elective operations, particularly aorto-ilio-femoral prostheses (0.5% as against 1.24%), but not in operations conducted as emergencies. In addition, frequency of infection due to BGN fell only slightly. Finally, combined therapy with oxacillin-amikacin had 2 disadvantages: impossibility of using these antibiotics for prophylaxis alone as provided for in the protocol, and its high cost. Factors of choice of antibiotic should be: efficacy against germs encountered, which can vary from year to year, rarity of toxic or side effects, good tissue diffusion, the rare need for therapeutic use and a low cost.

Amikacin↗
PubMed1986

[Nonatheromatous degenerative aneurysm of the popliteal artery in a young adult female].

A degenerative non atheromatous popliteal aneurysm was observed in a 32 year old woman. At microscopical examination of the aneurysmal shell, the internal elastic-lamina and the muscular fibers of the media appeared to be replaced by a thick acellular collagen layer. No other arterial abnormality was found on a complete arteriography and the etiological screening failed. Therefore the aneurysm was classified as an arterial dysplasia. As far as we know, only two similar cases were previously reported in the literature. The true nature of these lesions remain unknown.

Adult↗
PubMedDate not supplied

Should all spontaneous popliteal aneurysms be operated on?

Operative treatment of spontaneous popliteal aneurysms (S.P.As) is occasionally disappointing. In order to determine the criteria for operation we analyzed retrospectively the fate of 77 S.P.As in 52 patients (mean age, 66 +/- 10 years). S.P.As were divided into 3 groups according to initial symptoms: group I, asymptomatic or mild symptoms, group II, rest pain or toe gangrene, group III, severe ischemia or foot gangrene. Patency rate of arterial reconstruction in groups I, II, III were respectively 83%, 43%, 36%. The course of S.P.As of group I that were not initially operated was not significantly different compared to those operated on, as long as they were frequently reviewed and operated on expeditionaly in cases of complications. The nature of the arterial substitute was the second contributing factor. Quality of run-off had no influence in groups I and II, but was determinant in group III. A good general condition was essential for survival. Operative indications of S.P.As is considered according to classification into 3 groups. Group I: bypass is mandatory, except when the general condition of the patient is poor or when a bad run-off is associated with an unavailable vein. Group II: bypass should be attempted whenever a distal arterial segment seems suitable. Otherwise lumbar sympathectomy may sometimes save a limb. Group III: bypass should be attempted only when the run-off is sufficient and when the tissue damage seems reversible. In the other cases, primary amputation is safer.

Adult↗