Sigmoid Colon Organ Motion in Radiotherapy

Radiotherapy is used in cancer treatment to eradicate microscopic cancer cells to lower the risk of recurrence. The radiotherapy plan must account for organ movement inside the body to ascertain adequate dose is delivered to the target. Knowledge of the magnitude is crucial to radiotherapy treatment planning. This study aims to quantify the movement of the sigmoid colon between different fractions of radiotherapy treatment (interfraction motion) and within the same fraction (intrafraction motion). This knowledge will help us determine the optimal margin to use in radiotherapy treatment planning.