Introduction The most common form of malignancy in the nasophar- ynx is undifferentiated carcinoma, which accounts for up to 98% of all nasopharyngeal malignancies in East- ern countries [1]. The natural history of tumor spread is well documented in the literature [2, 3, 4, 5, 6]. The mainstay of treatment for nasopharyngeal carcinoma NPC) is radiation therapy. The high frequency of skull- base erosion and intracranial extension requires ade- quate radiation treatment coverage of the middle cra- nial fossa. Eur. Radiol. 2001) 11: 317±324 Ó Springer-Verlag2001 NEURO V.F.-H.Chong H.Rumpel Y.-F.Fan S.K.Mukherji Temporal lobe changes following radiation therapy: imaging and proton MR spectroscopic findings Received: 1 October 1999 Revised: 25 February 2000 Accepted: 23 May 2000 V.F.-H.Chong ) ´ H.Rumpel ´ Y.-F.Fan Department of Diagnostic Radiology, Singapore General Hospital, Outram Road, Singapore 169608, Republic of Singapore S.K.Mukherji Department of Radiology, University of North Carolina, Chapel Hill, NC 27599-7510, USA Abstract Radiation therapy for na- sopharyngeal carcinoma affects the temporal lobes. This paper charac- terizes proton MR spectroscopic findings of the temporal lobes and correlates them with imaging chan- ges. Single-voxel proton MR spec- troscopic examinations were ac- quired from 13 healthy adult volun- teers 25 spectra) and 18 patients 28 spectra). All patients had biopsy- confirmed nasopharyngeal carcino- ma and were previously treated with radiation therapy. Six patients 33%) had a single treatment and12 67%) patients had two treatments. Point resolved spectroscopy PRESS) method was used TR = 3000 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 addi- tional non-water-suppressed refer- ence scan in fully relaxed conditions was performed. The imaging find- ings were divided into four catego- ries: 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 nor- mal in 8 29%) spectra and reduced in 20 71%) spectra. Imaging showed 4 14%) spectra with cate- gory-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 res- onance spectroscopy showed re- duced N-acetyl-aspartate in radia- tion-induced temporal lobe changes. Creatine levels were relatively more stable. Choline levels may be in- creased, normal, or reduced. Imag- ing findings ranged from normal to contrast-enhancing lesions and cys- tic encephalomalacia. Keywords MR spectroscopy ´ MR imaging ´ Nasopharyngeal carcinoma ´ Radiation therapy ´ Temporal lobe necrosis