Investigation of positioning deviations and irradiation dose for daily head and neck patients image-guided radiotherapy

Abstract

Abstract: Precise positioning during the radiotherapy procedure of the head and neck patients is extremely important due to the highly sensitive organs at risk surrounding the irradiated target. Set-up errors can occur due to various reasons, such as body contour changes of the patient, which may happen on behalf of weight loss or shrinkage of the tumour, or due to the inappropriate use of immobilisation tools, etc. Image-guided radiotherapy enables corrections and monitoring of these positioning deviations. However, along with known benefits, performing kV-CBCT verifications before each treatment inevitably leads to additional exposure doses. It is known that daily imaging of kV-CBCT for the patient could increase the daily exposure dose by ~1.4 mGy. Investigation was done using linear accelerator Halcyon V3.1 (Varian Medical Systems, Palo Alto, CA, USA), which ensures 100 % Image-guided radiotherapy. All the daily data were collected from medical treatment planning system EclipseTM (Offline Review tool) and were processed with statistical computing software “R”. Analysis of the results showed that despite the additional irradiation doses for the patient, the benefits of daily verifications are undeniable, because patient positioning deviations do not have a clear variation tendency and change randomly during each fraction.