Stereotactic radiotherapy of a single brain metastasis. A: Visualization of the target volumes for the treatment of a single intracerebral metastasis of a carcinoma of the lung (58 y old female, Adeno-Ca, pT2, pN1 (2/8), cM1). A 3D-reconstruction displaying the metastasis (violett) and proximate sensitive structures (bulbus and tractus opticus = green and pink; brown = brain stem). B: Visualization of photon beams for the target volume based on planning CT applying stereotactic frames. Surrounding isodoses account for 90 percent at 20 Gy. Margins can be reduced to a minimum with regard to the possibility of exact patient positioning.