Different types of adverse effects from therapeutic radiation of the brain tumors are more frequently recognized. Late injury is the most serious consequence and major dose limiting complication of cerebral irradiation. Depending on anatomical imaging appearances, late injuries can be divided into focal and diffuse lesions. Tumor residue or recurrence and post radiotherapy necrosis produce disruption of the blood brain barrier, which cause their unreliable distinction by either conventional CT or MRI. However this differentiation can be possible using functional radionuclide imaging using 99mTc sestaMIBI SPECT, which is known to have a high sensitivity for detecting viable tumor tissue.