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Biomedical subjects

K Ewen

Publications and source records attributed to K Ewen.

At least 55 records · Page 3Linked to original sources
PubMed1986

[Radiation exposure of patients and operators during interventional radiology].

Surface doses received by patients and operators were measured during 30 interventional radiological procedures (ten percutaneous transhepatic biliary drainages, ten percutaneous nephrostomies, ten percutaneous transluminal angioplasties). In addition, organ doses to the patient were determined using an Alderson-Rando phantom. These served as a basis for calculating the so-called somatic dose indices. It was found that the somatic radiation risk to the patient is relatively small despite prolonged periods of fluoroscopy. However, exposure of the hands and lenses of the operator could easily reach the limits thought acceptable while carrying out these procedures with additional angiography.

Adult↗
PubMed1986

Somatic and genetic radiation exposure of the patient in digital subtraction angiography (DSA)

The somatic and genetic radiation exposure of patients undergoing Digital Subtraction Angiography (DSA) and traditional Film Arteriography (FA) of cranial, cervical, thoracic and abdominal vascular territories are compared. The radiation doses absorbed within the critical organs--red bone marrow, lung, thyroid gland and female breast--and in the gonads were measured using an anthropomorphic Alderson phantom. A Somatic Dose Index was calculated in order to estimate the somatic radiation risk. The somatic radiation exposure depends upon the location of the critical organs with respect to the entrance site of the x-ray beam, and can be reduced by an appropriate choice of the angiographic projection. Under this condition, the radiation exposure of the patient during DSA can be lower than during FA. For renal DSA an a.p. projection, the use of an abdominal compression device and careful caudal shielding of the field are advocated.

Cerebrovascular Disorders↗
PubMed1986

[Radiation burden in high-resolution computerized tomography of the petrous bone].

Exposure to irradiation and radiation stress of the eye lens, thyroid and skin in high resolution computed tomography of the petrous bone are demonstrated by means of measurements conducted by the authors, and compared with results published to date. The radiation stress is less than the doses measured during conventional polytomography of the petrous bone. The exposure of the crystalline lens, in particular, depends decisively on the angle of the gantry or on the position at which CT is performed. The coronary plane is the projection of choice in respect of minimum irradiation exposure. The somatic dose index is higher than in conventional x-ray examinations of the skull, but lower than in cranial CT or other CT examinations.

Humans↗
PubMed1986

[Somatic radiation risk to the breast under different radiological research procedures].

This paper deals with radiation risk in terms of somatic dose index from different mammographic techniques (Xeromammography, Screen-film-mammography alone or with additional grid, and industrial film mammography) and from various non-mammographic radiodiagnostic procedures with the breast partially or totally exposed to the x-ray beam, e.g. tomography of the lungs and dorsal spine, fluoroscopy, angiography, and computerised tomography of thoracic organs.

Angiography↗
PubMed1985

[Somatic radiation risk in large-field irradiation].

The somatic dose index was determined for large-field irradiations with the 10 MeV bremsstrahlung of a linear accelerator. Among the possible field shapes, the authors investigated the mantle field, the inverted Y field, the boomerang field, as well as total body irradiation and upper and lower partial body irradiation. The measured data are discussed with respect to clinical aspects.

Humans↗
PubMed1985

[Procedure for the control of tube voltage in roentgen diagnostics].

It is often necessary to check X-ray tube voltage within the framework of quality control requirements which will soon become legally mandatory. Non-invasive methods are most suitable, but their cost and accuracy are subject to variation. The more precise the measurement of tube voltage, the costlier the measuring instrument and method of measurement will be. However, there are also relatively simple systems which will yield quite satisfactory results.

Methods↗
PubMed1984

[Radiation protection in the operation of accelerator and plasma equipment].

Relatively great problems of radioprotection can be caused by accelerator units, above all in the field of science, because all kinds of ionizing radiation and radioactive substances can be produced in all states of aggregation. Furthermore, activities with relatively long half-lives are induced by high particle streams with energies beyond the thresholds of many nuclear reactions, so that the conditions of a control zone, even of a prohibited zone exist at many points after having switched off the accelerator. Not all of these radioprotective problems can be solved by constructive or technical measures. A sufficient skill of the persons responsible for radioprotection is very important in this connection. Efficient radioprotective measures are only possible by a close cooperation between the radiation protection officer, the competent authority, and the expert.

Germany, West↗
PubMed1984

[Practical experiences in the determination of tube voltage using the Ardran-Crooks cassette].

Within the framework of quality control measures in x-ray diagnostics and therapy, it is desirable to employ for the determination of tube voltage (e.g. in diagnostic x-ray equipment) methods which are as economical as possible while saving time and being simple to apply in spite of the fact that they are as as highly accurate as ever possible. The absorber method described here, represented by the Ardran-Crooks cassette, possesses the advantage of low price and easy application. However, if it is operated in such a way that time is saved (assessment by the eye), it is not so accurate, whereas in accurate operation (assessment via luxmeter) it does require a relatively large amount of time. After the film has been exposed, it is necessary to estimate or measure the agreement of blackenings on one and the same film in order to determine the tube voltage. This voltage is then read off by means of a calibration curve. The error in the determination of the tube voltage via the Ardran-Crooks cassette depends on the accuracy of the calibration curve, which, in turn, depends on the number of measurements performed when producing the curve, and on the correct voltage of the standard x-ray equipment used in producing the calibration curve. In addition, assessment by eye adds a total error of 2.3% to 8%, depending on the amount of tube voltage. If the luxmeter is used instead of the eye, this additional error is less than 1% in relation to the magnitude of the tube voltage.(ABSTRACT TRUNCATED AT 250 WORDS)

Calibration↗
PubMed1984

Radiation exposure in high resolution computed tomography of the spine.

From all the available radiodiagnostic procedures for diagnosing spinal disorders (conventional tomography, myelography, CT), high-resolution, thin-slice computer tomography presents the highest radiation exposure as represented by the somatic dose index. It allows, however, the retrospective computer reformatting of axial slices into secondary slices of any projection desired. To obtain this extra information with conventional tomography would require further exposures in the desired projections and/or thinner slices. But there is a great amount of important diagnostic information that plays a decisive role in the choice of the form of therapy and the preoperative planning of surgical which cannot be obtained by conventional radiological procedures.

Bone Marrow↗
PubMed1983

CT imaging in lumbar disc disease. The value of multiplanar reconstructions.

A CT/T 8800 (General Electric) CT scanner was used to study lumbar disc disease in fifty patients. In seven patients so-called computed tomography metrizamide myelography was performed, whereas in the remaining cases no contrast enhancement was used. Multiplanar reconstructions were done. Irradiation exposure was measured during the investigations and compared with data during conventional myelography. We found that lumbar CT scanning is not a screening method in cases of lumbar disease, but the aimed use gives further information about the underlying process and its differential diagnosis. Multidirectional reconstructions reduce the number of diagnostic errors. This procedure does not increase the radiation exposure dose in comparison with conventional myelography.

Adult↗
PubMed1983

[Radiation exposure during digital subtraction angiography (DSA) of the kidney and aortic arch].

The somatic and genetic radiation dose from DSA and conventional film angiography were compared, using an Anderson-Rando phantom. The dose is greatly influenced by the method of examination; for the examination of the aortic arch in a male, DSA reduces it by a factor of 4 as compared with conventional angiography, in a female by a factor of 11. For renal DSA (PA) somatic dose for a man is 25 times greater, and for a woman 18 times greater, than with conventional angiography (AP). Renal DSA should therefore be carried out in an AP projection in order to reduce the bone marrow dose in the lumbar spine.

Angiography↗
PubMed1983

[Radiation exposure during ERCP and pneumocolon].

During the course of 50 ERCPs and 70 pneumo-colons, the surface dose in the field and the scatter was measured by CaF2-thermoluminescence dosimetry. The organ dose for both procedures was calculated by using an Alderson-Rando phantom. The results were used for calculating somatic dose indices in order to evaluate the individual and collective risks. Radiological examination of the colon results in two hundred times the gonadal dose produced by ERCP, but produces less radiation to the thyroid, lung and female breast.

Cholangiopancreatography, Endoscopic Retrograde↗
PubMed1983

[Somatic radiation risk in brain irradiation].

The somatic dose index for irradiation of the brain was determined for the 10 MeV bremsstrahlung of a linear electron accelerator. A small volume rotation technique and the irradiation of the total neurocranium were chosen as extreme conditions for the radiation exposure of the skull. On the basis of a target volume dose of 50 Gy for the total irradiation series, the somatic dose index of the small volume technique is within the scope of coronarography. In case of irradiation of the total neurocranium, however, the somatic dose index largely exceeds the maximum values of X-ray diagnosis.

Brain↗