title: Temporal lobe changes following radiation therapy: imaging and proton MR spectroscopic findings.
abstract: Radiation therapy for nasopharyngeal carcinoma affects the temporal lobes. This paper characterizes proton MR spectroscopic findings of the temporal lobes and correlates them with imaging changes. Single-voxel proton MR spectroscopic examinations were acquired from 13 healthy adult volunteers (25 spectra) and 18 patients (28 spectra). All patients had biopsy-confirmed nasopharyngeal carcinoma and were previously treated with radiation therapy. Six patients (33%) had a single treatment and 12 (67%) patients had two treatments. Point resolved spectroscopy (PRESS) method was used (TR = 3,000 ms, TE = 135 ms) and data processed automatically using the LCModel software package for metabolite quantification. Voxel size and geometry were adapted to the lesion to reduce skull-base lipid contamination. The metabolites were quantitated relative to water signal. For each location, an additional non-water-suppressed reference scan in fully relaxed conditions was performed. The imaging findings were divided into four categories: I, normal; II, edema only; III, contrast-enhancing lesions; and IV, cystic encephalomalacia. The N-acetyl-aspartate levels were reduced in 27 (96%) spectra. Choline was increased in 3 (11%), normal in 4 (14%), and reduced in 21 (75%) spectra. The creatine level was normal in 8 (29%) spectra and reduced in 20 (71%) spectra. Imaging showed 4 (14%) spectra with category-I imaging findings; 5 (18%) spectra with category-II findings; 15 (54%) spectra with category-III findings; and 4 (14%) spectra with category-IV findings. Magnetic resonance spectroscopy showed reduced N-acetyl-aspartate in radiation-induced temporal lobe changes. Creatine levels were relatively more stable. Choline levels may be increased, normal, or reduced. Imaging findings ranged from normal to contrast-enhancing lesions and cystic encephalomalacia.
authors.affiliation: Department of Diagnostic Radiology, Singapore General Hospital, Republic of Singapore.
authors.forename: V F
authors.initials: VF
authors.lastname: Chong
authors.forename: H
authors.initials: H
authors.lastname: Rumpel
authors.forename: Y F
authors.initials: YF
authors.lastname: Fan
authors.forename: S K
authors.initials: SK
authors.lastname: Mukherji
mesh_terms: D000328:Adult; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000032:analysis; D002277:Carcinoma / Q000532:radiotherapy*; D002713:Chlorine / Q000032:analysis; D003404:Creatinine / Q000032:analysis; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D009303:Nasopharyngeal Neoplasms / Q000532:radiotherapy*; D009336:Necrosis; D011832:Radiation Injuries / Q000175:diagnosis / Q000209:etiology / Q000378:metabolism*; D013702:Temporal Lobe / Q000737:chemistry* / Q000473:pathology
chemical_list: D001224:Aspartic Acid; D002713:Chlorine; C000179:N-acetylaspartate; D003404:Creatinine