Investigation into the radiobiological consequences of pre-treatment verification imaging with megavoltage X-rays in radiotherapy

Objective: The aim of this study was to investigate the effect of pre-treatment verification imaging with mega-voltage X-rays on cancer and normal cell survival in vitro and to compare the findings with theoretically modelled data. Since the dose received from pre-treatment imaging can be significant, the incorporation of this dose at the planning stage of treatment has been suggested. Methods: The impact of imaging dose incorporation on cell survival was investigated by clonogenic assay of irradiated DU-145 prostate cancer, H460 non-small-cell lung cancer and AGO-1522b normal tissue fibroblast cells. Clinically relevant imaging-to-treatment times of 7.5 and 15min were chosen for this study. The theoretical magnitude of the loss of radiobiological efficacy due to sublethal damage repair was investigated using the Lea-Catcheside dose protraction factor model. Results: For the cell lines investigated, the experimental data showed that imaging dose incorporation had no significant impact on cell survival. These findings were in close agreement with theoretical results. Conclusion: For the conditions investigated, the results suggest that allowance for the imaging dose at the planning stage of treatment should not adversely affect treatment efficacy. Advances in knowledge: There is a paucity of data in the literature on imaging effects in radiotherapy. This article presents a systematic study of imaging dose effects on cancer and normal cell survival, providing both theoretical and experimental evidence for clinically relevant imaging doses and imaging-to-treatment times. The data provide a firm foundation for further study into this highly relevant area of research.