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Micro ion beam for radiobiology

At PTB's ion acceleration facility a new micro ion beam apparatus has been developed. The new machine is dedicated for applications in radiobiology. It can irradiate living cells with a defined number of ions at a lateral accuracy in the sub-cellular range. Such micro ion beam experiments serve above all to investigate relevant phenomena in radiobiology, such as tumour formation.

Micro ion beam apparatus with optical microscope

Tumour growth is a complex, multistage process. Initially the genetic material of a normal healthy cell is damaged. This initial damage can occur spontaneously or it can be induced by interactions with various agents, e. g. chemical substances, viruses or ionising radiation. With the new apparatus scientists can expose living cells to ionising radiation in a controlled manner. This makes it possible to investigate the mechanisms responsible for the creation of cancer cells induced by exposure to ionising radiation. In result, improved estimates of the hazards of occupational and natural radiation exposure can be made.

In recent years, a few research institutes have endeavoured to improve their ion beam facilities to such an extent that cells could be irradiated with a defined number of ions at sub-cellular lateral accuracy (< 5 µm) (micro ion beam). Advantages of applying micro ion beams are that the contingencies of conventional irradiation are eliminated and important control parameters such as dose, dose rate and target location can be pre-selected with high accuracy. Effects of low doses can be investigated with higher reliability than was hitherto possible.

The apparatus at PTBÕs ion accelerator facility utilizes magnetic lenses to focus a proton or alpha particle beam on a lateral diameter of about 1 µm. The intensity of the beam is reduced to a few particles per second. Thin scintillation detectors measure the impingement of an ion on the sample with an efficiency of 98 % to 100 %. A substantial advantage over other operating facilities is the wide range of ion energies available at PTB. Significant investigations of the effects induced by the different kinds of radiation found in nature (i. e.: alpha, beta and gamma radiation) can now be carried out.

First cell irradiations have been carried out in co-operation with the Faculty of Medicine of Gšttingen University. Other scientists working in radiobiological research and other fields, for example materials research, intend to use the PTB facility for novel experiments. Cell irradiations in routine operation will be possible from summer 2002.