Postoperative radiotherapy of breast cancer. Investigations about optimal dose distribution in irradiation of the thoracic wall by tangential fields. II (in German)
Experimental investigations are reported for the study of dose distributions on the thoracic wall in irradiation via tangential standing fields. A special water-model with particularly thin walls as well as a Machlett-Alderson- Rando-Man-Phanto m were used for the measurements. The dosimetry was performed by ionometry with a micro-tube-chamber and the Duplex-dosimeter on the water- phantom, by thermoluminescence dosimetry with LiF TLD-100 dosimeters on the Alderson-phantom. The measured values were recorded on punched tapes and processed in a computer. By arithmetic superimposition of the counter-fields the isodoses of the superimposition could be demonstrated. The arithmetic variation of the irradiation parameters (angle of incidence, exposure) made it possible to study various modes of irradiation. The measurements were made for kilovolt technique, the tele-cesium-apparatus, the tele-cobalt apparatus, and the 17MeV- Betatron for ultrahard x-ray radiation. The accuracy of the dose distributions found on the water-model could be tested by comparison with the results obtained on the body-equivalent model. With tele-cesium, tele-cobalt and ultrahard x-rays using tangential counter-fields, an equal perradiation of the thoracic wall was attained, with adequate to satisfactory protection of the lung tissue, whereas the conventional deep x-ray therapy did not guarantee satisfactory dose distributions. An improvement of the dose distribution by different exposure of the fields was not possible. Differences of the dose distribution on the Alderson model are caused by inhomogeneities of the tissues. With the kilovolt- technique, particularly before the superimposition of the standing fields, a marked influence caused by inhomogeneities was observed. Conclusions are drawn for practical radiotherapy and a technique of adjustment to the patient was described which permits reproducible irradiations and the use of the resulting isodoses. (GE)
- Research Organization:
- Univ., Tuebingen, Ger.
- NSA Number:
- NSA-29-025875
- OSTI ID:
- 4333770
- Journal Information:
- Strahlentherapie, v. 146, no. 3, pp. 268-288, Other Information: Orig. Receipt Date: 30-JUN-74; Bib. Info. Source: GE (GE)
- Country of Publication:
- Germany
- Language:
- German
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