The influence of mineralising radionecrosis on the dose distribution in interstitial radiation therapy of brain tumours.
The influences of radionecroses arising during interstitial radiation of brain tumours with 125I, 192Ir or 198Au on dose distribution was investigated using Monte Carlo methods. The necroses have a higher density than normal tissue due to radiation-induced changes in tissue composition as well as mineral deposits. They can have a diameter of up to 1 cm around the single seeds. The higher density and changed chemical composition compared to homogeneous normal tissue leads to increased absorption of radiation around the necroses which results in a lower dose rate in the surrounding tissue. It is shown that the formation of necroses during treatment with higher energy radiation such as 192Ir (340 keV) or 198Au (400 keV) may be neglected during therapy planning as the dose rate is affected by less than 2%. If low energy radiation, e.g. 125I (28 keV) is used, the dose rate can be reduced by more than 30%. In this case the influence of the necroses on dose distribution, at least for permanent 125I implantation, may not be negligible.
Herbold
G
G
German Cancer Research Center, Department of Radiology, Heidelberg.
Hartmann
G H
GH
Lorenz
W J
WJ
D000818:Animals; D001918:Brachytherapy; D001921:Brain / Q000473:pathology / Q000528:radiation effects*; D001932:Brain Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D004285:Dogs; D004307:Dose-Response Relationship, Radiation; D006050:Gold Radioisotopes / Q000627:therapeutic use; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D007496:Iridium Radioisotopes / Q000627:therapeutic use; D009010:Monte Carlo Method; D009336:Necrosis; D011879:Radiotherapy Dosage
D006050:Gold Radioisotopes; D007457:Iodine Radioisotopes; D007496:Iridium Radioisotopes