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Biomedical subjects

K Ewen

Publications and source records attributed to K Ewen.

At least 19 recordsLinked to original sources
PubMed1995

[Radiation exposure of radiologists during angiography: dose measurements outside the lead apron].

The aim of this study was to provide practical information to angiographers concerning radiation exposure to body parts not covered by lead aprons. Individual doses to the neck and hands of radiologists measured in micro-Sieverts were obtained during the course of 80 angiographies of various types. The number of diagnostic and interventional procedures, which might lead to exceeding permissible doses, have been calculated. Possibilities of estimating doses during angiography by means of parameters such as screening times were examined statistically. Especially with regard to the hands, estimations of the doses are insufficient (correlation r = 0.21). Radiologists who undertake much angiographic and particularly interventional work may reach exposure levels requiring protective measures in addition to lead aprons.

Angiography↗
PubMed1995

[Effects of the medical products legislation on roentgen services].

On January 1, 1995 the law concerning medical products (Medizinproduktgesetz-MPG) came into force. It essentially regulates the production, circulation, and the putting into service of medical products as well as equipment. Among other things, the so-called active medical products include medical X-ray equipment whose aspects concerning atomic law remain covered by the radiation protection regulation for X-ray sources (RöV). Parallel to the coming into force of the MPG, the RöV was modified (Section 50, MPG), which in future might result in considerable consequences for the manufacturer, the operator, and the authorities.

Equipment Safety↗
PubMed1994

[Minimizing radiation exposure for the patient and staff].

Therapeutic interventional methods in cardiology increase radiation exposure of patients and staff to a much higher extent than any other radiological examination. Reasons for this fact and ways to reduce the exposure are presented.

Angioplasty, Balloon, Coronary↗
PubMed1993

[Are high-intensifying film-screen combinations suitable for the detection of fine interstitial lung changes? The results of a ROC study with an anthropomorphic thorax phantom].

Exposures of an anthropomorphic thorax phantom in posteroanterior projection were made using a focus-film distance of 200 cm and 125 kV with film-screen combinations in class 200 (Curix RP 1L/MR 200) and class 400 (Curix ST-L/Regular). Pathomorphological structures of the lung parenchyma of fine nodular, linear and reticular types were simulated by suitable materials. A ROC analysis including a t-test showed no significant difference in the evaluation of these structural details (p > 0.05). In order to describe image quality for the two film-screen systems, density curves, sigma D-curves and modulation transfer function (MTF) were determined. The only demonstrable difference was reduced MTF of 10-15% for the higher intensification film-screen combination with a resulting poorer resolution of 3.7 l/mm (for the 400 system) compared with 4.3 l/mm for the 200 system.

Evaluation Studies as Topic↗
PubMed1992

[The radiation loading of the crystalline lens and thyroid during high-resolution computed tomography of the teeth].

The radiation dose to the ocular lens and thyroid gland during high resolution CT of the jaw was measured in a head phantom and in 9 patients. The dose for the lens and thyroid gland resulting from 10 cuts was 0.7 and 0.9 mGy, respectively. By shielding the thyroid gland against scatter a reduction of 20% is possible. Radiation exposure is considerably higher than during conventional dental x-ray examinations. Compared with CT examinations of the head and neck region, radiation exposure of both organs is about the same.

Humans↗
PubMed1992

[Digital cineradiography (DCR) of the act of swallowing. The initial clinical experiences].

Twenty-seven patients with different swallowing disorders were studied by employing digital cineradiography (DCR) for rapid imaging of the pharynx with a temporal resolution of up to 50 frames per second and a maximum spatial resolution of .8 per/mm. To facilitate therapy planning, the DCR study can be transferred to the otorhinolaryngologist via videotape. DCR is capable to substitute analog cine or video techniques in the pre- and postoperative examination of patients with swallowing disorders.

Cineradiography↗
PubMed1992

[Quality assurance in radiology from the viewpoint of the specialists and the supervisory authorities].

Quality assurance for diagnostic imaging equipment has been successful so far. In the old Federal Republic of Germany, inspection of the existing equipment in diagnostic radiology in being completed. The estimated number of uninspected units is relatively small. All detected shortcomings have been repaired in the meantime, and very few faults have been detected in newly installed equipment. Of the status obtained following inspection and repair is to be maintained, however, more effective methods must be implemented. There is no doubt that everybody involved in quality assurance programs, including the experts and supervisory authorities, is actively working on improving the results.

Germany↗
PubMed1989

[Determining organ doses in the uterus during dental x-ray examinations].

It was the goal of this study to determine the uterine exposure to radiation during dental x-ray examinations and to assess the inherent radiation hazard to the fetus. The mean organ dose for the most common examination procedures was found to be 0.4 muSv (0.004 mrem) per radiograph. This figure may be reduced by a factor 2 when the patient wears a protective apron that meets the requirements of the German industrial standard DIN 6813. According to these results, dental radiography--of all diagnostic radiography procedures--involves the least radiation risk to the fetus. Based on ICRP's (International Commission on Radiation Protection) considerations on radiation risk and on the assumption of a linear dose-response relationship it may be concluded that there cannot be one case in a million pregnant women exposed to a uterine dose of 0.2 muSv where a fatal event has to be assumed.

Dose-Response Relationship, Radiation↗
PubMed1989

[Equipment and methodologic parameters of radiation exposure in digital subtraction angiography].

The mutual dependence of various parameters--frame rate, radiation dose per frame, size of the image intensifier field, photon energy, frame mode, and patient diameter--is investigated systematically on a modern DSA equipment. The software programme of the DSA machine widely modifies these parameters according to the individual conditions, which may influence both radiation exposure and image quality. IV DSA requires low photon energies to exploit the low iodine signal. Higher frame rates, oblique views and small image intensifier fields should be used restrictively especially in the abdomen, as they tend to lower the radiation doses per frame and to increase photon energies, thus impairing contrast resolution. Full understanding of the physical and technical basics and familiarity with the software programme of own DSA machine are mandatory to allow appropriate selection of the various parameters, according to the individual patient and his/her diagnostic problems. They are the key to optimal imaging quality at a tolerable radiation exposure.

Angiography↗
PubMed1989

[Radioactivity of air in the vicinity of medical linear accelerators].

Some mathematical expressions are given for the calculation of the activity concentration (13N,15O) in the surroundings of medical electron accelerators with a maximum photon energy up to 25 MeV. The author differentiates between prolonged irradiations typical of physical operation or maintenance work and shorter irradiations separated into fractions which are typical of the treatment of patients. In most cases the calculated concentrations are considerably lower than the limit values valid e.g. for persons of category B professionally exposed to radiation, so that the margin of error assumed for this calculation method is of no significance. A measure of the activity concentration which is always time- and cost-consuming would be unnecessary in that case.

Air↗
PubMed1989

CT scanning of the breast in problem cases.

This is a report of the experience with 200 patients who during 1981 to 1984 underwent breast scanning on a conventional body scanner. Pre- and post-contrast scans of the breast were obtained. A postcontrast enhancement of 50 HU and more turned out to be specific for malignant lesions. Radiation dose to the breast was in the same range as with high filtration xeromammography and high resolution film-screen mammography with additional grid. Breast scanning is recommended in cases in which mammography alone is of limited value, including dense fibrocystic breasts in women at high risk, follow-up in breast cancer patients after breast conserving therapy, in patients with silastic implants and in the follow-up of breasts with huge scars due to multiple biopsies.

Adolescent↗
PubMed1988

[Has the new x-ray legislation come into operation too early?].

The new legislation governing the handling of x-rays and radiation has come into effect from 1 January 1988. Many hold the opinion that this was a too early date for its enforcement, because the system of accompanying guidelines and standards is still incomplete. The present article deals with these problems and offers a survey of the present status of guidelines and standards, especially with regard to quality assurance and control.

Germany, West↗
PubMed1988

[Radioactivity in dismantling a betatron].

The authors report on the specific radioactivity of construction components of a 42 MeV betatron measured 28 days after the last run by means of a Ge spectrometer (ultra-pure germanium detector employed in a semiconductor spectroscopic method) recording the gamma spectra of various components of the betatron. This examination served to find out which components would have to be considered as radioactive waste requiring special treatment in accordance with Federal German legislation on radioactive waste disposal (section 47 of the Radiation Protection Ordinance). The examination showed that such special treatment would be required only for the target (main material: platinum) and the Platness-filter (chief constituent: lead) of the decommissioned electron accelerator.

Humans↗
PubMed1987

[Determination of the integral doses in conventional x-ray studies and computed tomography of the skull].

Absorbed energy (integral dose) is a suitable measure of radiation exposure during radiodiagnostic examinations. The integral doses from conventional and CT examinations of the skull were determined, using an Alderson-Rando phantom. The absorbed energy of one exposure using a film-screen combination and for one plane of conventional tomogram is almost identical. Considering the total absorbed energy, lower doses are to be expected for CT than for conventional tomography. A survey view is associated with reduced radiation exposure.

Humans↗
PubMed1987

[Comparison between 2 methods of determining photon-induced air activity around medical accelerators].

The authors compare two different methods to determine the activity of the air induced by the bremsstrahlung of medical accelerators. The activities of the air resulting from maximum photon energies of 16 to 42 MeV are measured with a proportional counter tube ("direct measurement") and by means of activation analyses of imidazole, triazole, malonic acid, and urea specimens ("indirect measurement"). The results are compared.

Activation Analysis↗