Magnetic resonance imaging (MRI) and proton beam therapy are two powerful techniques of medical physics. The former gives us real-time images of internal structures of the body, and the latter can deliver a high dose of radiation to a tumour while reducing the damage to surrounding healthy tissue.

In this episode of the Physics World Weekly podcast, the medical physicist Aswin Hoffmann talks about a research initiative in Germany that is combining the two techniques to achieve high-precision radiation therapy. The work is being done at the Center for Innovation in Radiation Oncology (OncoRay) in Dresden and the Helmholtz-Zentrum Dresden-Rossendorf. Hoffmann explains why it is important to develop MRI-guided proton beam therapy and the challenges that his team is overcoming.

Also in this episode, we chat about a new experimental technique that physicists have developed to study how bacteria move about. This research is part of the burgeoning field of active matter and we explore why physicists are interested in bacteria, flocking birds and other living systems.