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The Comparison of 13N-Ammonia and 18F-FDG in the Evaluation of Untreated Gliomas

Shi, Xinchong MD; Liu, Yubo MD; Zhang, Xiangsong PhD; Yi, Chang MD; Wang, Xiaoyan MD; Chen, Zhifeng MD; Zhang, Bing MD

doi: 10.1097/RLU.0b013e318295298d
Original Articles

Objective Noninvasive evaluation of glioma is of great help for clinical practice. In this study, we investigated the utility of 13N-ammonia in the evaluation of untreated gliomas and compared the results with that of 18F-FDG.

Methods Forty-five consecutive patients with final diagnosis of glioma were included in this study. PET/CT imaging was performed for all of them with both 18F-FDG and 13N-ammonia as tracers. Imaging results were analyzed by tumor-to-gray matter (T/G) ratios. Receiver operating characteristic curve analysis was conducted to determine the optimal T/G cutoff values of each tracer between low-grade and high-grade gliomas.

Results Forty-eight separate lesions were identified in all (grade II, n = 16; grade III, n = 12; and grade IV, n = 20). Twenty-nine out of 32 high-grade lesions (91%) showed higher uptakes than normal gray matter with 13N-ammonia in comparison with the result of 21 lesions (66%) with 18F-FDG. The optimal T/G cutoff values for 18F-FDG and 13N-ammonia were 0.64 and 0.86 separately with the area under each curve 0.910 and 0.943. The sensitivity and specificity of predicting high-grade gliomas with optimal cutoff values were 83% and 93% for 18F-FDG and 94% and 94% for 13N-ammonia, respectively.

Conclusion 13N-Ammonia is superior to 18F-FDG not only in separating low-grade gliomas from high-grade ones but also in the detection of high-grade gliomas for better tumor to normal gray matter contrast.

From the Department of Nuclear Medicine, the First Affiliated Hospital of Sun Yat-Sen University, Guangzhou, China.

Received for publication December 10, 2012; and revision accepted March 23, 2013.

Conflicts of interest and sources of funding: none declared.

X.S. and Y.L. had equal contribution to this research and were responsible for initial writing.

Reprints: Xiangsong Zhang, MD, Department of Nuclear Medicine, the First Affiliated Hospital of Sun Yat-Sen University, #58 Zhongshan Er Road, Guangzhou 510080, China. E-mail: bdolphin@sina.cn.

© 2013 by Lippincott Williams & Wilkins