This project is concerned with the development and optimisation of proton-electron double-resonance imaging (PEDRI), a technique which combines magnetic resonance imaging (MRI) with electron paramagnetic resonance (EPR) in order to image the distribution of free radicals in biological samples and in living animals. The project will explore the use of advanced radiofrequency EPR techniques in order to improve the sensitivity of PEDRI. In particular, the use of ultra-fast pulsed EPR irradiation will be investigated, since it offers a theoretical two-fold sensitivity advantage over continuous-wave EPR irradiation. Multi-tuned resonators for PEDRI will also be developed in combination with automatic frequency/matching controls to improve efficiency. Detailed comparisons between the different irradiation strategies will be made under a variety of experimental conditions, and optimum parameters for the use of these techniques to study free radicals in vivo will be determined.