Defining the therapy region
In the image data set obtained, the attending physician now marks the area which is to receive the therapeutic radiation dose and which areas and organs must be protected. Many aspects of the tumor disease must be taken into account. For some, it is sufficient to treat the tumor region itself, for others, lymph drainage must also be taken into account, since metastases (metastases) are more frequent in this region. In addition, the radiation exposure of the healthy neighboring organs must be taken into account so that no permanent damage is caused here by the radiation therapy.
Calculating the irradiation plan
According to the physician’s instructions, the radiation plan is now created by the medical physicist.This includes from which and from how many angles the liner accelerator should radiate onto the therapy region, what energy and intensity the X-ray beam should have, etc. The technical aspects are thus determined.
Simulation of the irradiation
Once the plan has been calculated and accepted after checking the quality requirements, an irradiation is now run through, i.e. simulated. For this purpose, the patient is placed back in the position he was in during computed tomography. The alignment is carried out with the help of the skin markings.
When calculating the irradiation plan, images were reconstructed that show what x-rays would look like if they were taken from the angles from which the linear accelerator irradiates. With the help of a special X-ray apparatus, the X-ray simulator, X-rays are now taken from these angles and compared with the calculated ones. If they match from all angles, radiation therapy can be performed in this way.
