[The role of large portal- and shielding-techniques in radiotherapy (author's transl)].

Since electron linear accelerators with energies up to 20 MeV were introduced to radiotherapy it has become easier to irradiate large portals than was previously possible with 60Co unites or betatrons. The reasons for this are: 1) More favourable depth dose distribution resulting in better field homogeneity 2) Considerably smaller penumbra 3) Higher and more constant dose rates 4) Larger portals. The indications for the following large portal techniques are discussed: 1) Total nodal irradiation 2) Total lung irradiation 3) Abdominal bath 4) Irradiation of larger segments of the extremities 5) Whole body irradiation.