Patients with cervix cancer having radiotherapy experience side-effects because the radiotherapy fields have to be quite large to account for tumour movement in the pelvis during treatment, this irradiates a lot of normal tissues. This study aims to characterize and model the tumour motion, as well as the motion of surrounding normal tissues, during treatment. By doing this, the investigators can look at ways to minimise tumour motion and spare more normal tissues. By tailoring the radiotherapy dose more accurately, the investigators will reduce the side-effects of treatment and improve local control of the tumour. By doing multiple magnetic resonance imaging (MRI) scans of the patients during treatment, the investigators can identify where the tumour and surrounding normal tissues are at that point in time. Collecting all the information from these scans, will allow the investigators to model the motion of the tumour and these pelvic organs, and investigate the best way to target the tumour while still sparing normal tissues.