title: Differentiation of the radiation-induced necrosis and tumor recurrence after gamma knife radiosurgery for brain metastases: importance of multi-voxel proton MRS.
abstract: Comparative analysis of the diagnostic accuracy of FDG PET, single-voxel, and multi-voxel proton MRS for differentiation between radiation-induced necrosis and tumor recurrence was done in 9 patients with brain metastases treated by gamma knife radiosurgery. In all cases enlargement of the lesion and increase of the perilesional edema were demonstrated by MRI on average 10.6+/-2.6 months after initial treatment. Radiation-induced necrosis was identified in 5 patients (histologically in 2, clinically in 3). In one of these a false positive result of FDG PET was observed, whereas data of proton MRS were always correct. The diagnosis of tumor recurrence was established in 4 patients (histologically in 3, clinically in 1). Among these both FDG PET and single-voxel proton MRS showed false negative results (each method twice), whereas multi-voxel proton MRS always permitted us to establish the correct diagnosis. The present study demonstrates the higher diagnostic accuracy of multi-voxel proton MRS, in comparison with single-voxel proton MRS and FDG PET, for the differentiation of the radiation-induced necrosis and tumor recurrence. Its use is especially important in mixed lesions with co-existence of both post-irradiation changes and viable neoplasm. Monitoring of the treatment response by serial multi-voxel proton MRS seems to be reasonable during follow-up of patients with brain metastases after radiosurgery.
authors.affiliation: Department of Neurosurgery, Neurological Institute, Tokyo Women's Medical University, Tokyo, Japan. m_chernov@yahoo.com
authors.forename: M
authors.initials: M
authors.lastname: Chernov
authors.forename: M
authors.initials: M
authors.lastname: Hayashi
authors.forename: M
authors.initials: M
authors.lastname: Izawa
authors.forename: T
authors.initials: T
authors.lastname: Ochiai
authors.forename: M
authors.initials: M
authors.lastname: Usukura
authors.forename: K
authors.initials: K
authors.lastname: Abe
authors.forename: Y
authors.initials: Y
authors.lastname: Ono
authors.forename: Y
authors.initials: Y
authors.lastname: Muragaki
authors.forename: O
authors.initials: O
authors.lastname: Kubo
authors.forename: T
authors.initials: T
authors.lastname: Hori
authors.forename: K
authors.initials: K
authors.lastname: Takakura
mesh_terms: D000016:Abnormalities, Radiation-Induced / Q000175:diagnosis*; D000230:Adenocarcinoma / Q000473:pathology / Q000532:radiotherapy* / Q000556:secondary*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001932:Brain Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000556:secondary*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D009336:Necrosis; D009364:Neoplasm Recurrence, Local; D016634:Radiosurgery / Q000295:instrumentation*; D011878:Radiotherapy / Q000009:adverse effects*