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Proton MR spectroscopic characteristics of pediatric pilocytic astrocytomas
J H Hwang1, G F Egnaczyk, E Ballard
1Imaging Research Center, Department of Radiology, Children's Hospital Medical Center, Cincinnati, OH 45229, USA.
Purpose:
We report the common characteristics of juvenile pilocytic astrocytomas revealed by proton MR spectroscopy.
Methods:
Eight children with pilocytic astrocytomas were studied with proton MR spectroscopy. The selected sampling volume was approximately 4 cm3, obtained from solid tumor. To localize the sampling volume, we used point-resolved spectroscopy (PRESS) and stimulated-echo acquisition mode (STEAM) techniques to acquire long- and short-TE spectra, respectively. Spectra from PRESS and STEAM sequences were processed using Lorentzian-to-Gaussian transformation and exponential apodization, respectively. For PRESS (2000/270) spectra, peaks of creatine, choline, N-acetylaspartate (NAA), and lactate resonances were integrated; for STEAM (2000/20) spectra, we measured the amplitude of the peaks at 3.2, 2.0, 1.3 and 0.9 ppm.
Results:
An elevated lactate doublet was observed in the PRESS spectra. The choline/NAA ratio was 3.40. The amplitude ratios of the lipid pattern (0.9, 1.3 and 2.0 ppm) to choline were all below one.
Conclusion:
Despite the benign histology of the tumor, which generally lacks necrosis, a lactate signal was detected in all eight patients studied. A dominant lipid pattern was not observed.