[The radiobiological aspects in the blocking of sensitive structures from the irradiation field].

BACKGROUND

In some cases the total dose has to be reduced in a section of an irradiation field by means of a transmission block. This can be performed in 2 different ways: 1. A part of the planned fractions is blocked. 2. The dose of each fraction is reduced using a transmission block (transmission < 100%).

METHOD

For both methods the biological tumor and normal tissue doses were calculated using the linear-quadratic model. A clinical case is discussed.

RESULT AND CONCLUSION

With transmission blocks a therapeutic gain can be obtained.