High-precision irradiation of brain tumours and brain metastases
For the irradiation of brain tumours and metastases from tumours of other organs that have settled in the brain, high-precision stereotactic radiotherapy has become the standard within the last few years.
With this method, a defined dosage of x-rays is applied to a defined target area with pinpoint accuracy. The radiation exposure to the surrounding healthy tissue can be strictly limited, while the radiation concentration on the tumour is especially high. In this way, the brain tumours can be treated with the necessary high dosage of radiation without damaging other areas of the brain.
The irradiation is so precise that a multiplied dosage – compared with conventional radiotherapy – can be administered. This increases the effectiveness accordingly and thus the chances of the tumour diminishing or receding completely. It is also important that recurring tumours can be treated with this procedure again.
How does stereotactic radiotherapy work?
The success of radiotherapy depends highly on the dosage of radiation that reaches the tumour. The surrounding, healthy tissues should be exposed as little as possible in order to keep damage as low as possible. The more precisely the tumour is hit by the irradiation, the higher the administered dosage can be, while still avoiding serious impact on surrounding tissue. The particular challenge in irradiation of brain tumours and metastases lies in the fact that they are often located near highly sensitive areas (e.g. brain stem, optic nerve). Therefore, the irradiation, which requires a high dosage in order to be effective, must be applied as accurately as possible.
Up to now, radiotherapy in the brain area was only possible through the use of conical projectors (collimators) to form the radiation beam. When irregularly formed tumours or tissues growths were to be irradiated, multiple circular dosages had to be combined with large effort, the result of which was an irregular irradiation with some areas being overly exposed and a higher total dosage of radiation having to be administered. Through stereotactic convergence irradiation, multileaf collimators (MLC) can be used in addition to the conical collimators depending on the form of the tissue growth to be treated. With the help of MLCs, small and irregularly formed tissue growths can be targeted flexibly and from multiple directions, even when located near highly sensitive structures like the brain stem.
Forms of treatment
- There are two basic forms of radiotherapy possible:
A one-time irradiation (Radiosurgery): a high dosage of radiation is administered one time that causes the unhealthy tissue to die (in the middle term). - The fractionated stereotactic precision-irradiation: the total dosage of irradiation is divided among multiple sessions.