Dosimetry with alanine for MR-guided radiotherapy

• Applicant: Dr.-Ing. Franziska Renner
• Subject Area: Medical Physics, Biomedical Technology
• Term: from 2015 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 286492401

A new development in the field of magnetic resonance (MR) guided radiotherapy is the combination of both modalities - the irradiation and the MR imaging - in one hybrid device. With respect to dosimetry at such devices the response of dosemeters like ionization chambers which are routinely used for dosimetry in radiotherapy were investigated. The investigations showed a significant change of the dosemeter response in static magnetic fields in comparison to the response in the case without magnetic field. Since a static magnetic field is effective at MR therapy devices all the time the problem arises that dosemeters and methods which are usually used for dosimetry in radiotherapy cannot be used readily at hybrid MR therapy devices. Thus, at the moment, there is no dosimetric method for these devices available which is exact and traceable to a national primary standard. Regarding quality assurance this is a lack of a precondition for the use of such devices in clinical praxis. A possible alternative for dosimetry at MR therapy devices is alanine dosimetry. This method is based on alanine as a detector material and electron spin resonance spectroscopy to evaluate the detector response. Alanine dosimetry has many positive characteristics and can be used as secondary standard measuring system for the traceable and exact dosimetry in traditional radiotherapy. In the course of this project proposal the appropriateness of alanine for the dosimetry at MR therapy devices will be investigated. Thereby, investigations in static magnetic fields as well as in magnetic and electromagnetic fields of a magnetic resonance tomograph will be performed.

• DFG Programme: Research Grants