RRTI and NKI design a radiation treatment simulator

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The RRTI simulator in the Netherlands Cancer Institute, picture taken in 1973 after the move of the simulator to the new department in Amsterdam-Slotervaart. Radiation therapist: Lia de Vries. Click the picture to enlarge.

Implementation of the conventional simulator.

Irradiations performed with sharply focused high intensity radiation beams from linear accelerators have to be delivered with great precision. The purpose is to cover the tumour completely with sufficient radiation dose and to spare as much as possible healthy tissue, in particular vulnerable organs.  

Around 1971 a treatment simulator is designed in the Rotterdam Radiotherapy Institute (RRTI) as a tool in the design of a radiation treatment plan. A simulator is a device to visualize the geometry of a radiation beam in relation to the anatomy of a patient using X-ray imaging. In this way it is possible to design an accurate treatment plan in a relatively short time. The result is used for the dose calculation. On the skin of the patient orientation points and lines are drawn, used to direct the treatment beams coming from the accelerator.

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Drawing at the simulator of the area to be irradiated, in this case on the plastic fixation mask.

The idea to design a treatment simulator came from Els van Doornum, the chief radiation therapist in Rotterdam. Until that time conventional X-ray equipment was used, but this had set-up alignments that were not the same as those on linear accelerators. In a cooperative project between the RRTI and NKI the specifications are worked out for a simulator which is able to imitate the projections of the radiation beams of the new linear accelerators. The clinical physicist Hans van de Poel was in charge of the design and the manufacture of the simulator. Theo Wilmering, engineer in the NKI, also contributes to the design. The device is built in the workshop of the RRTI by Mr Florisson and his team. In 1972 the simulator is brought into use in the NKI. In Rotterdam two simulators are installed. In 1980 Els van Doornum is awarded the Muntendam price by the national cancer foundation KWF for her work in the field of radiation oncology.       

The design of this RRTI simulator served as a source of inspiration for the first Simulix simulator that was commercially produced by the company "Optische Industrie de Oude Delft", later "Oldelft" and subsequently named "Delft Instruments". The X-ray image intensifier in the simulator is of the type Delcalix made by "de Oude Delft".

This type of conventional simulator is in general use during the preparation phase of a radiotherapy treatment until virtual techniques became available using 3D anatomical information obtained with CT scanning. In this way integration of the geometrical simulation and the dose calculation was obtained. After 2000 the conventional simulator is gradually phased out.