X-ray images keep track of scanned protons

Description

The Paul Scherrer Institute (PSI) in Switzerland was a pioneer in the development of pencil-beam scanned proton therapy. The site's newest proton gantry – Gantry 2 – is dedicated to fast scanning, offering the ability to perform ultrafast volumetric target repainting and intensity-modulated proton therapy. But while active scanned proton delivery offers many advantages over passively scattered protons, the technique is also particularly sensitive to geometric and temporal variations.