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Medical Radiation Physics

Medical radiation physics is an interdisciplinary science where the effects of ionising radiation in matter, especially living tissues, are studied. Ionising radiation can be emitted by radioactive decay or technical devices such as x-ray tubes and particle accelerators. The two main fields of study are Diagnostic radiology and Radiation therapy.

The research at our department is performed within both fields, but the main direction of research is Radiation therapy.

Radiation therapy of cancer

Radiation has, for several decades, been used to treat tumors. The treatment has been performed with many different types of radiation (treatment modalities) such as photons, electrons, protons, neutrons, and heavy ions. The clinically most used treatment modalities are photons and electrons. Currently the treatment is planned by a calculation of the resulting dose distribution from a number of given treatment set-up parameters. One aim of the reasearch is to solve the treatment planning problem by inverse methods (i.e. find the set of treatment parameters that gives the desired result). This may appear to be the obvious way to handle the problem. It is, however, a difficult task to develop physical and mathematical models that will solve this problem without large approximations and within reasonable time. We have developed tools for treatment optimization from the basic physical and biological models that describes the treatment outcome.

The new calculation models lead to treatments that are more complex than those used today. The technology necessary to perform these treatments has not been available and we have therefore developed a new type of treatment unit able to deliver significantly more complex treatments with accelerator potentials up to 50MV. A multileaf collimator and a scanning system are located inside the head of the treatment unit, making it possible to modulate the particle fluence in a manner similar to the electron beam in a TV-set.

Diagnostic radiology

In nuclear medicine radioactive nuclides are used for treatment and diagnosis. Radioactive substances are injected in the patient and transported to the area that is to be investigated. The activity distribution is registred with a large detector. At the department a new type of scintillation detector is developed for this purpose. With this new detector system the resolution will be significantly improved. A basic difference between nuclear medicine and traditional x-ray images is that the x-rays result in an anatomical image of the patient. Nuclear medicine imaging, however, results in a physiological image.

There is also a group at the department working with MRI (Magnetic Resonance Imaging). MRI generates images in 3D by placing the patient in a strong magnetic field. The nuclear spin of the atomic nuclei (usually protons) within the patient becomes aligned with the magnetic field. A combined transmitter/reciever transmits radiowaves that are absorbed by the nuclei. The radiosignal is then turned off and the protons retransmit the radiosignal. The signal is registered and processed in a computer to generate a picture. MRI has become an established diagnostic tool and may develop to become the leading diagnostic technique. At the department MRI is developed for new diagnostic fields of application. A new method for the study of flow within the body has been developed.