OPTIS -- A proton therapy facility for eye tumors
Since 1984 PSI cooperates closely with the Hôpital Opthalmique of the Université de Lausanne in the development and use of the OPTIS equipment for proton radiotherapy of eye melanomas. By end of 2011 more than 5700 patients had been treated with this unique method, in which a proton beam is directed accurately onto the retinal tumor. In more than 98% of cases tumor growth could be stopped or the tumor eradicated. In more than 90% of cases the eye could be saved.
OPTIS is a pioneering therapy facility which has inspired six further installations in Europe. OPTIS can currently treat the following eye tumors (about 200 to 250 patients a year):
• uveal melanomas, including those which have only partly responded to other therapies
• Coroidal hemangiomas, growths in the blood vessels of the eye
• Intraocular metastases in the eye
• Melanomas of the conjunctiva
• age related macular degeneration
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.