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Post operative MRI 6 months following tumor removal

Differential Diagnosis

Recurrence of GBM

Radiation Necrosis

Abscess

Radiation injury

May be divided into:

Acute –within weeks and transient

Early delayed-within <3 months and transient

Late delayed-months to years, irreversible affecting white matter more than grey matter with vasculitis ,demyelination,coagulative necrosis and hyalinization

70% injuries occur within 2yr post therapy

Treatment

Removal of necrotic irradiated tissue and steroid therapy

This may be curative in select lesions

Radiation Injury

CT: ACUTE-CONFLUENT WHITE MATTER LOW DENSITY EDEMA

DELAYED- FOCAL AND MULTIPLE WHITE MATTER LOW DENSITIES

PET:

Recurrent tumor has increased activity were as radiation necrosis does not . Overall accuracy of 85% however this is controversial.

Radiation Injury

MR Spectroscopy

Marked reduced metabolites (NAA, Choline, Creatinine) with increased lactate and lipid peaks

Differs from abscess due to fact that infection has high metabolites like succinate and amino acids