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.
Carcinoma, Bronchogenic Carcinoma, Squamous Cell