Proton magnetic resonance spectroscopy of cerebral glioma after irradiation.
BACKGROUND
Conventional magnetic resonance imaging (MRI) is commonly employed to assess cerebral gliomas after radiotherapy, but it cannot always differentiate tumor regrowth from post-irradiation changes. In this study, we utilized magnetic resonance spectroscopy (MRS) to evaluate changes in cerebral metabolites in patients with a cerebral glioma after irradiation.


METHODS
Over a period of 3 years, we performed MRS after MRI whenever soft tissue masses were found on magnetic resonance (MR) images. A total of 122 MR spectra of 58 patients was used for analysis. Spectral interpretations were based on integral values of the N-acetylaspartate (NAA) and choline (Cho) compounds relative to phosphocreatine/creatine (Cr).


RESULTS
Our MRS study showed that higher Cho/Cr ratios occurred in regrowing gliomas than for stable diseases (range, 0.9 to 9.5 vs. 0.4 to 2.1; mean, 3.0 vs. 1.2). A greater increment in the Cho/Cr ratio between successive studies was also noted in regrowing gliomas than for stable disease (range, 41% to 87% vs. < 32%). No significant differences in NAA/Cr ratios or lactate were found between these 2 groups. None of our patients exhibited abnormal MR spectra in the mirror area of the contralateral brain.


CONCLUSIONS
MRS provides valuable information about the metabolism of irradiated gliomas and can be used to exclude radiation encephalopathy of the contralateral brain. Cho is the most reliable indicator of a regrowing glioma. A high Cho/Cr ratio or substantial elevation in the Cho/Cr ratio between serial studies increases the likelihood of tumor regrowth. However, lower Cho/Cr ratios were inconclusive for determining if tumor regrowth or a stable process was occurring.
Ng
S H
SH
Department of Diagnostic Radiology, Chang Gung Memorial Hospital, Taipei, ROC. shng6@ms25.hinet.net
Ko
S F
SF
Chen
W C
WC
Tang
L M
LM
Chang
C N
CN
Wai
Y Y
YY
Wan
Y L
YL
D001921:Brain / Q000378:metabolism*; D001932:Brain Neoplasms / Q000378:metabolism* / Q000532:radiotherapy*; D002794:Choline / Q000378:metabolism; D003401:Creatine / Q000378:metabolism; D005910:Glioma / Q000378:metabolism* / Q000532:radiotherapy*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy
D003401:Creatine; D002794:Choline