8. MEDICAL PHYSICS ________________________________________________________________________________________________

The research interests of the Laboratory of Medical Physics have been focused on four main areas: 1) boron neutron capture therapy (BNCT), 2) patient dosimetry in diagnostics and treatments, 3) medical imaging applications and 4) modelling of physiological and biological systems for clinical studies. Research has been done in co-operation with Helsinki University Central Hospital (HUCH), the Technical Research Center of Finland (VTT) and Finnish Centre for Radiation and Nuclear Safety (STUK).

1) The Finnish research reactor (FiR 1) operated by the Technical Research Center of Finland (250 kW TRIGA II pool reactor) will be used as a neutron source in BNCT. In the spring 1997 the reactor hall has been rebuilt for treatment purposes. In the autumn season the characterisation of the beam as well the dosimetry measurements have been carried out. The facility is ready for in vivo experiments.

2) A method for measuring absorbed doses at the patient skin in order to approximate doses of the critical organs has been studied in collaboration with HUCH and STUK. New calculation methods have also been developed to obtain more accurate dose distributions in the patient. A computer pro-gram for calculating patient specific organ doses in diagnostic radiology has been further developed. Methods for cellular level dosimetry have been investigated.

3) New MRI techniques (magnetization transfer and spin lock) for increasing the tissue contrast and characterization have been studied. The study was performed in vitro and in vivo in normal and in tumor brain patients.

4) The main interest has been focused on boronophenylalanine (BPA) and bleomycine kinetics. The models are to be used in BNCT-research.

The Laboratory of Medical Physics has been financed by the Academy of Finland, University of Helsinki, the State Subsidy for University Hospitals, research grant of the Departments of Radiology and Neurology (Helsinki University Central Hospital), TEKES, the Instrumentarium Science Foundation, the Finnish Society of Nuclear Medicine and the Trust of Aarne Koskelo which are gratefully acknowledged.

Juha Lampinen and Sauli Savolainen