Simulator (radiation therapy)

A simulator or therapy simulator is a special X-ray fluoroscopy and recording device . The therapy simulator is spatially separated from the radiation room, but has the same geometry and the same movement options as a radiation device (gantry, collimator and table can be rotated, the necessary accessories can be added).
In preparation for a radiation with a linear accelerator can to determine or control the exact patient position for irradiation and to review the earlier reference to a computed tomography started treatment plan simulation are performed.
In this context, "simulation" means that the position of the patient and the position of the patient in space are exactly reproduced. All technical parameters of the irradiation plan (field size, angle of gantry, collimator and table) can be reproduced by the therapy simulator and checked and documented both radiologically and optically (using a light localizer). The distance between the patient and the radiation source is checked. X-rays , mostly digital, document the settings.
Blocks that are inserted into the irradiation field to protect healthy tissue can be checked for correct positioning on the simulator. Mostly, multi-leaf collimators are used to protect normal tissue. With modern therapy simulators, these can be digitally displayed on the X-ray image and also projected onto the patient in space.

After the simulation, the isocenter axes as well as the shape and size of the radiation fields are marked on the positioning aids and the patient's skin. The isocenter axes are projected onto the patient in lines by a laser system .

In addition to a digital distance display, modern linear accelerators also have at least one verification system. With the therapy beam (in the MV area) and an opposing detector, verification recordings can be made that enable the patient to be checked and (if necessary) corrected before the daily irradiation. For this purpose, a coronary and a sagittal X-ray image, for example, is made with the lowest possible energy beam from the accelerator and compared with the digitally reconstructed X-ray images (DRR) contained in the radiation plan.
The same task is performed by the X-ray tubes and detector systems that are integrated in more modern linear accelerators and are installed orthogonally to the therapy beam, with which high-quality (digital) X-ray images are generated. With these recording systems, a simulation is also possible directly on the therapy device.

Individual evidence

1. ↑ Simulator ( Memento of the original from February 19, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , German Society for Radiation Oncology e. V. (accessed on February 2, 2014) 
2. ↑ Physical-technical quality assurance in radiation therapy - suggestions for testing the entire treatment system Recommendation of the Radiation Protection Commission, p. 10 (PDF; 829 kB) (accessed on February 2, 2014)

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