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Biomedical subjects

K Welker

Publications and source records attributed to K Welker.

At least 19 recordsLinked to original sources
PubMed2004

[Staff requirements in medical radiation physics for diagnostic radiology in Germany: results of a questionnaire].

To get a general idea of the actual staffing situation in medical radiation physics, all active members of the German Society of Medical Physics (DGMP) were surveyed by the task force "staff requirements" ("Personalbedarf") of the DGMP in 1999. Of the 322 forms sent out, 173 could be evaluated. The staff requirements in medical radiation physics were calculated from the major elements of the radiology equipment and from the staff responsibilities as defined in the DGMP Reports 8 and 10, and compared with the actual number of staff members. The data of this spot check were then extrapolated for the entire Federal Republic of Germany. The calculation revealed a deficit of 89% for the entire staff in diagnostic radiology and of 84% for physicists. Considering the age distribution of the DGMP members, a training capacity of about 100 medical physicists per year is needed to eliminate the calculated deficit within the next 10 years.

Germany↗
PubMed1996

[The personnel needs of health physics in radiotherapy].

METHODS AND RESULTS: Using a questionnaire, mean occupation time values for the different medical physics activities were derived in 1992; they formed the basis for recommendations of minimum physics staffing levels in radiotherapy. The recommended staffing levels were compared with the actual staffing levels and to other national and international recommendations.

Germany↗
PubMed1990

[Studies of lung density as a basis for irradiation planning].

The irradiation of tumors in thoracal area presupposes an exact irradiation planning including the lung to prevent therapy limiting dosage errors. With it the exact dimension and the density of the lung have to be known. It was investigated of which factors the lung density depends on and how they affect the dosage precision. Within the lung the density fluctuates considerably; these fluctuations are different from patient to patient and depend on age among other things. This age dependence can be represented by a regression straight line; with this the lung density of patients can be found out from age approximatively. Individual investigation of density from CT-sections can improve precision of dose calculation up to 4%. It has to pay attention to producing CT-sections with normal respiration and in such position as the later irradiation shall be done in.

Adolescent↗
PubMed1989

[Computed tomography in the diagnosis of isolated bone metastases and its influence in therapy planning].

In a collective of 70 patients with bone metastases the importance of CT for detection and extension diagnosis is shown. In 53% CT proved the scintigraphic and/or roentgenologic suspicion. In 30% CT gave more information than scintigraphy and plain radiography, but without any influence in the treatment. In 17% only CT gave such important information, that the planned treatment must be changed. The results led to the conclusion, that CT can be important for the optimization of radiological treatment.

Bone Neoplasms↗
PubMed1986

Fractionated lung irradiation in young pigs with 6.2 MeV neutrons and cobalt-60.

Irradiations of the right lung with 6.2 MeV neutrons (38 test animals) and 60Co photons (34 test animals) were made using young pigs. Twenty animals were used as controls. Five fractions were administered in an overall treatment time of 5 or 35 days. The radiogenic pneumopathy was monitored with clinical, radiological and histological investigations, and by determining the hydroxyproline content in the lung tissue. The pneumopathy in pigs given neutrons developed after a shorter latency period and followed a more rapid and serious course than that in animals given gamma rays. While after photons the extension of the overall treatment time from 5 to 35 days led to a measurable but low increase of the ED50 this was not true for neutrons. The relative biological effectiveness (RBE) for the 6.2 MeV neutrons compared with 60Co photons was 4.0 for an overall treatment time of 5 days and 4.1 for 35 days.

Animals↗
PubMed1983

Preliminary report on "one-time" and high dose irradiation of the upper and lower half-body in patients with small cell lung cancer.

Forty-two patients with histologically confirmed inoperable small (oat) cell lung cancer were treated with local tumor irradiation (approximately 4,000 cGy) combined with "one-time" irradiation of the upper and lower half of the body. Twenty-five patients (Group I) received the irradiation in lateral position first to the upper half-body, and six weeks later to the lower half-body, the midplane dose averaging 880 cGy (not corrected for lung tissue). In 17 patients, lethal pneumonitis occurred. The mean time of survival was 8.2 months for 22 patients having the disease limited to one thorax-side and 4.0 months for three patients having distant metastases, stated by conventional clinical and X ray investigations. Seventeen patients (Group II) received the two half-body irradiation treatments through anterior-posterior fields. The average dose had been reduced to 800 cGy (uncorrected) and was given on one day in two fractions (600 and 200 cGy, separated by an interval of 5 hours). Furthermore, the forearms and the lower legs had been left outside the fields. Only one patient showed pneumonitis. The mean time of survival was 14.3 months for 12 patients having the disease limited to one thorax-side and 6.6 months for five patients having distant metastases. In both groups, serious reactions of the bone marrow were not observed. In Group II, leucocytes and lymphocytes had reached their original values three months after the end of irradiation. For all 42 patients, X ray films showed complete regression of the primary tumor. In 12 out of 35 autopsy specimens, the primary tumor could not be detected histologically, but only five of these were free of metastases. Presently, additional irradiation of the two halves of the body with lower and fractionated doses are being tested in order to achieve the further reduction of tumor cell numbers.

Bone Marrow↗
PubMed1977

[Neutron therapy in the GDR. VIII. The calculation of dose distributions (author's transl)].

The calculation of dose distribution for each patient is a basis for the neutron therapy. A computerprogram was developed for it basing on the matrix-method. We find out several field matrix for each field size. The dose calculation goes by addition of the matrix values on the certain points inside the patient's cross-section. A correction of the dose distribution in consequence of the oblique beam is possible. Dose distributions for several irradiation techniques are discussed.

Computers↗