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) Boron neutron capture therapy (BNCT) is one of the most complex cancer therapeutic modalities, and its ultimate success is dependent on how adequate concentrations of boron and neutrons can be delivered to the tumour. 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 September 1996 a conical beam collimator was installed to the reactor. This collimator enables to use the epithermal field for animal and human experiments.

2) In radioimmunotherapy the knowledge of patient dosimetry is essential when planning the treatments. 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 has also been developed to obtain more accurate dose distributions in the patient. Both experimental and computational methods have been used to investigate the patient doses in x-ray diagnostics.

3) The calculation methods used in radioimmunotherapy have been further developed to be applied with abdominal fusion images for more precise results. New MRI techniques (magnetization transfer and spin lock) for increasing the tissue contrast and characterization has been studied. The study was performed in vitro and in vivo in normal and in tumor brain patients.

4) Work has been made in the field of modelling platelet kinetics. The main interest has been focused on BPA and bleomycine kinetics. The models are to be used in BNCT-research.

The publications, conference contributions and seminars given by the members of this laboratory (C. Aschan, U. Abo Ramadan and the undersigned) are given on these links, respectively.

The Laboratory of Medical Physics has been financed by the Academy of Finland, University of Helsinki, TEKES, the Finnish Society of Nuclear Medicine and the Trust of Aarne Koskelo which are gratefully acknowledged.

Juha Lampinen and Sauli Savolainen

DETERMINATION OF 10B IN HUMAN BLOOD BY USING PIGE METHOD

Tiina Kupila-Rantala, Martti Kulvik*, Sauli Savolainen and Merja Kallio*

The boron neutron capture therapy (BNCT) is a potential therapy form for patients suffering from glioma. The usefulness of boron phenylene alanine (BPA) as a boron carrier in human blood was investigated by adding BPA diluted in fructose to human whole blood. In order to study the concentration of boron in different blood fractions, red cells and plasma were separated. The boron content of the whole blood and the two fractions were measured both by the proton induced gamma ray emission (PIGE) and the inductively coupled plasma atom emission spectrometry (ICP-AES). Solid samples needed by PIGE were prepared by lyophilizing and pressing pellets from the dry residues. For ICP-AES the samples were further wet ashed. The measurements showed that the boron was concentrated to the plasma fraction, whereas no evidence of boron binding in red cells was found.