%0 Generic
%A Niebuhr, Nina Isabelle
%C Heidelberg
%D 2021
%F heidok:27620
%R 10.11588/heidok.00027620
%T Biological Dose Accumulation in Image-guided Radiotherapy
%U https://archiv.ub.uni-heidelberg.de/volltextserver/27620/
%X Dose accumulation (DA), the computation of the total delivered 3D dose distribution Da  of a fractionated radiotherapy treatment using daily patient imaging, is getting established  in clinical practice. Although the aim is to estimate the achieved biological outcome of the  treatment, the principles of biological effect estimation are currently not followed consistently  in the process. In this thesis, the biological effect accumulation approach and total  biological dose (bEQD) were derived as a biologically consistent DA workflow. Clinical  relevance of bEQD and its dependence on individual workflow aspects were investigated  in data from three patient cohorts. It was found that Da systematically underestimates  the obtained biological effect, which can be avoided by the use of bEQD. Results showed  that this is strongest for late-responding organs at risk (OAR) with low �=� values in  dose gradient regions around the target that are prone to organ motion. bEQD to Da  deviations occurred locally, in so-called hotspots, showing individual cases of high difference  magnitude but only small statistical impact. Hotspots of bEQD - Da deviation  around 4 Gy in bladder and rectum were found in patients treated for prostate carcinoma.  Hypofractionation increased these deviations strongly up to 8 Gy and also showed clinically  relevant deviations in dose-volume analysis. Dose-response correlation in standard  fractionation showed only little impact on the DA approaches. Workflow uncertainties are  dominated by those from deformable image registration, which are in the same range as  the difference between bEQD and Da. bEQD should be considered in the application of  treatment adaptation, especially to avoid damage to OARs in individual cases.