On the right: MRI picture
of an eye melanoma. On the left:.The
simulations and all other data provided by the ophthalmologists
are introduced into the treatment planning program which builds
an individual model of the eye and the tumor for every patient.
An optimal treatment position is searched for, i.e. a position
allowing to irradiate the tumor completely while sparing as much
as possible the healthy tissue surrounding the tumor, especially
the optic disc and nerve, the macula and the lens.
The therapy consists
of one treatment a day, for four consecutive days. The radiation
itself lasts about 60 seconds. In order to position the eye correctly
the patient fixes a light point on a coordination grid. Before
each radiation the position of the eye is checked with an x-ray
picture. Only when the position deviates less than 0.2 mm from
the correct position is the radiation carried out.
Part of the extension
of the new proton therapy facility at PSI (Project
PROSCAN) is a new OPTIS treatment room (OPTIS2), which started operation in 2010.