MRI-Guided Radiotherapy

Abstract

The goal of radiotherapy is to destroy malignant cells using ionizing radiation while sparing the surrounding healthy tissue as much as possible. Intensity-modulated radiation therapy (IMRT) and other recent advances in radiotherapy allow the dose to conform accurately to the shape of the tumor volume. Image guided radiotherapy (IGRT) aims to reduce the exposure of healthy tissue during radiation treatments by increasing the accuracy of target localization during the course of a treatment. The current IGRT modalities available still face problems when it comes to visibility of the tumor itself and/or the inability to provide intra fraction imaging. A radiotherapy modality that integrates a linear accelerator with an MRI scanner would have the unique ability to track the tumor and the surrounding organs at risk using images with a superior soft-tissue con- trast. MR-guided radiotherapy (IMgRT) is therefore able to dramatically decrease the toxicity of a treatment. It has been demonstrated that the presence of a strong magnetic field used for MR image acquisition does not limit the ability of MRgRT to deliver a homogeneous dose distribu- tion to the patient. However, technical issues such as dose measurements, geometrical distortion and adaptive treatment planning still needs to be solved before MRgRT can be implemented into the clinic.