Background : Cone beam computed tomography (CBCT) is widely used in image-guided radiotherapy (IGRT) to improve the accuracy of treatment, particularly in the thoracic and pelvic regions. However, repeated CBCT acquisitions raise concerns regarding cumulative radiation exposure, particularly to radiosensitive organs. Purpose : This study aims to provide a comprehensive dosimetric analysis of CBCT imaging protocols, focusing on size-specific dose estimates (SSDE) as a patient-centred metric that incorporates anatomical dimensions, such as anterior–posterior (AP) and lateral (LAT) diameters, to more accurately reflect absorbed doses. Methods : CBCT data were collected retrospectively from clinical procedures using standard thoracic and pelvic protocols. Manual calculations of SSDE were performed and compared across patients with different anatomical sizes. Dose variability was analysed in relation to patient dimensions. Results : Significant inter-patient variability was observed in SSDE values, ranging from 45.2 mGy to 271.46 mGy for thoracic imaging and from 229.31 mGy to 909.11 mGy for pelvic imaging. These corresponded to approximately 0.09–0.44% and 0.76–1.16% of the total prescribed therapeutic dose, respectively. Notably, smaller patients received disproportionately higher SSDE values, primarily due to reduced tissue volume and increased radiation concentration. Conclusion : The findings highlight the limitations of using fixed-dose metrics such as CTDIvol and emphasise the importance of incorporating SSDE into routine clinical practice. Personalised imaging protocols based on patient size are recommended to reduce unnecessary radiation exposure, particularly for paediatric and small-sized patients, while maintaining adequate image quality.
Soukaina et al. (2026) studied this question.