title: Early metabolic changes in metastatic brain tumors after Gamma Knife radiosurgery: 1H-MRS study.
abstract: Evaluation of early metabolic changes in metastatic brain tumors after Gamma Knife radiosurgery was performed by long-echo (TR, 2000ms; TE, 136ms; 128-236 acquisitions) volume-selected single-voxel proton magnetic resonance spectroscopy (MRS). Eighty-five brain metastases in 81 patients were investigated before treatment and 16-18h thereafter. Standard metabolic ratios, namely N-acetylaspartate (NAA)/creatine (Cr), phosphorylcholine/glycerophosphorylcholine (Cho)/Cr, NAA/Cho, lactate (Lac)/Cr, and mobile lipids (Lip)/Cr, were calculated, and comparison of their values before and after irradiation was done. No volumetric changes of any neoplasm were found in any case on the next day after treatment. At the same time, significant reduction of Cho/Cr (P < 0.001) and NAA/Cr (P < 0.01) ratios on the proton MRS of the tumor was disclosed. Reduction of Cho/Cr ratio was significantly more prominent in neoplasms with higher pretreatment Cho/Cr ratios (P < 0.001) and heterogeneous contrast enhancement (P < 0.01). Reduction of NAA/Cr ratio was predominantly determined by its pretreatment value (P < 0.001). The observed decrease of Cho/Cr ratio probably reflects inhibition of proliferative activity and early apoptotic cell loss, whereas reduction of NAA/Cr may result from radiation-induced modulation of neuronal activity in the peritumoral brain tissue. Serial proton MRS represents a valuable diagnostic tool for evaluation of metabolic changes in intracranial neoplasms after radiosurgical treatment.
authors.affiliation: Department of Neurosurgery, Neurological Institute, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan. m_chernov@yahoo.com
authors.forename: Mikhail F
authors.initials: MF
authors.lastname: Chernov
authors.forename: Motohiro
authors.initials: M
authors.lastname: Hayashi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Izawa
authors.forename: Kayoko
authors.initials: K
authors.lastname: Abe
authors.forename: Masao
authors.initials: M
authors.lastname: Usukura
authors.forename: Yuko
authors.initials: Y
authors.lastname: Ono
authors.forename: Osami
authors.initials: O
authors.lastname: Kubo
authors.forename: Tomokatsu
authors.initials: T
authors.lastname: Hori
mesh_terms: D000368:Aged; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D001932:Brain Neoplasms / Q000175:diagnosis* / Q000378:metabolism* / Q000601:surgery*; D003401:Creatine / Q000378:metabolism; D005260:Female; D005997:Glycerylphosphorylcholine / Q000378:metabolism; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D010767:Phosphorylcholine / Q000378:metabolism; D016634:Radiosurgery
chemical_list: D010767:Phosphorylcholine; D001224:Aspartic Acid; D019344:Lactic Acid; D005997:Glycerylphosphorylcholine; C000179:N-acetylaspartate; D003401:Creatine