Physics of MR image distortion: Impact on breast cancer radiotherapy

Magnetic Resonance Imaging (MRI) has superior soft tissue contrast compared to Computed Tomography (CT). This soft tissue contrast can be utilised to enable improvements in delineation of tumour and organ at risk volumes for radiotherapy treatment planning. CT is the imaging modality currently utilised for radiotherapy treatment planning. It provides accurate geometry of patient anatomy and provides electron density information as required for dose calculations. Currently, MR images are generally fused with CT images to enable the generation of radiotherapy treatment plans. There are continual advances being made to enable use of MR images alone for radiotherapy treatment plan dose calculations, as well as for in-room image guidance.