Which of the following techniques in the best for differentiating recurrence of brain tumour from radiation therapy induced necrosis?

Ans. is 'c' ie PET scan (Ref: Harrison, 16/e, p2460)."MRI or CT scans are often unable to distinguish radiation necrosis from recurrent tumor, but PET or SPECT scans may demonstrate that glucose metabolism is increased in tumor tissue but decreased in radiation necrosis." - Harrison.