<prompt> Answer this question truthfullyFor what purpose is CT utilized in the diagnosis or treatment of Medulloblastoma?  <response>: <reason> On head CT scan, medulloblastoma is characterized by: A hyperdense mass arising from the cerebellar vermis Effacement of the fourth ventricle and basal cisterns Dilated ventricles due to obstructive hydrocephalus Cysts formation and necrosis are observed among 40-50 of cases Calcification is observed among 10-20 of cases 