In this short video for our 100 Second Science series, Rob Chuter explains how radiotherapy can be aided by magnetic resonance imaging (MRI). Chuter, a principle clinical scientist at the Christie Hospital in Manchester, explains how these two technologies are combined into a so-called MR Linac device. The resulting technique, which has already been used to treat patients in the Netherlands, is now being clinically deployed at the Christie where it will improve the efficacy of radiotherapy and help with treatment planning.