Actually a lot of research that
medical physicists do would fall under the umbrella of computational medicine.
About 80% of
medical physicists specialize in radiation oncology physics, with the rest specializing in diagnostic imaging, MRI or nuclear medicine. In most cases
medical physicists hold clinical positions, which means they have clinical duties (QA and calibration of linear accelerators, supervision of the treatment planning process, commissioning new equipment, procedure development, clinical investigations, etc.) in addition to academic ones (teaching and research) and there's quite a spectrum of the degree to which each are weighted with some people being almost entirely clinical and others being primarily academic.
Medical physics research can involve a lot of computational work. Some examples:
- Monte Carlo simulations of radiation transport for treatment planning, or investigations of new procedures, treatment modalities, or imaging scenarios
- modelling of the response of cancers to treatment, cancer progression
- deformable image registration or dose mapping
- optimization problems
- development of computer-assisted diagnostic tools
You could have a look at these journals to get a good idea of research in the field:
Medical Physics
Physics in Medicine and Biology
International Journal of Radiation Oncology Biology Physics (Physics Contributions)
Radiotherapy & Oncology
Journal of Applied Clinical Medical Physics