PMC3556160_01
Colorwash dose distributions for prior radiation therapy are shown. Case 1, on the left, received treatment for medulloblastoma, 23.4 Gy (RBE) to the neuroaxis and a boost to the posterior fossa to 55.8 Gy (RBE). The 46 Gy (RBE) isodose line (purple) encroached upon the optic chiasm (purple). Case 2, on the right, received treatment for a grade III posterior fossa meningioma to 70.2 Gy (RBE). The 62 Gy (RBE) isodose line (cyan) abutted the lateral surface of the brainstem (cyan).
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F1
Review of the prior radiation showed the 46 Gy (RBE) isodose line encroaching on the optic chiasm (Figure 1). In the prior radiation plan, the 62 Gy (RBE) isodose line abutted the surface of the brainstem (Figure 1).