The interest in proton and ion-beam therapy has increased substantially in recent years, leading the Bureau International des Poids et Mesures to recommend that a new quantity be defined to account for the biological effect of treatment modalities used in the radiotherapy. In response, we have begun work on the design of a new microbolometer based on the inductive superconducting transition-edge detector (ISTED) designed at the National Physical Laboratory. Our work aims to expand the use of the ISTED from its current use as an infra-red detector to the measurement of energy deposition of photons, hadrons and ions by incorporating a tissue-equivalent absorber. We present here the work carried out till date, including the detection of single visible photons, with an energy resolution of 0.2 eV and a time response of a few microseconds, using a 15-µm Superconducting QUantum Interference Device operating at 9 K. We also describe thermal computational modelling carried out for a simple ISTED absorber. Finally, we discuss the work currently in progress and that to be carried out before the detector is realised.