Assessment of Malignancy in Brain Tumors by 3T MR Spectroscopy

To assess clinical proton MRS as a noninvasive method for evaluating brain tumor malignancy at 3T high field system. Using 3T MRI/MRS system, localized water-suppressed single-voxel technique was employed to evaluate spectra with peaks of NAA, choline (Cho), creatine (Cr) and lactate. NAA/Cr ratio of all tumor tissues was significantly lower than that of the normal tissues (p=0.005), but Cho/Cr ratio of all tumor tissue was significantly higher (p=0.001). Cho/Cr ratio of high-grade gliomas was significantly higher than that of low-grade gliomas (p=0.001). Higher grade of brain tumors was correlated with higher Cho/Cr ratio, indicating a significant dependence of Cho levels on malignancy of gliomas. Our results suggest that clinical proton MRS could be useful to predict tumor malignancy. Introduction The aim of this study was to test the usefulness of single-voxel proton MRS as a noninvasive method to evaluate the malignancy of brain tumors and correlation with results of surgical specimens. Our study was designed to differentiate brain tumors by using a combination of single-voxel spectroscopy, histophathological grades of malignancy in gliomas. In the present study, we used the quantitative approach for spectral analysis by using Cr. Materials and Methods Ten normal volunteers (5 males and 5 females) aged 19-41 years (median, 33.5 years) and 15 patients (6 males and 9 females) aged 11-73 years (median, 47.8 years) with brain tumors (12 gliomas and 3 others) were examined by localized in vivo 1H MR spectroscopy before any treatment. Tumor types are listed in Table 1. Result The variation of metabolites measurements of the designated region in 10 normal volunteers was less than 10%. Normal ranges of NAA/Cr and Cho/Cr were 1.67±0.15, respectively. In Table 1, twelve gliomas included 1 grade I tumor (pilocytic astrocytoma), 2 grade II tumors (astrocytomas), 4 grade III tumors (2 anaplastic astrocytomas, 1 anaplastic oligodendroglioma and 1 anplastic mixed glioma), and 5 grade IVtumors (5 glioblastomas), 1 medulloblastoma, 1 neurocytoma and 1 lymphoma. The representative case of grade IV, glioblastoma multiformeis presented in Figure 1. High-grade gliomas showed elevated Cho/Cr ratio, while low-grade gliomas had Cho/Cr values within the normalranges (Table 1). All tumor cases showed the decreased NAA/Cr ratio. The decrease in the NAA peak was the actual cause of the low NAA/Crratio. However, NAA/Cr ratio was not correlated with malignancy. Statistically significant differences between low-grade gliomas (grades I andII) and high-grade gliomas (grade III and IV) were shown in the levels of Cho/Cr and NAA/Cr (p=0.001). Lactate was more or less present in allthe gliomas. Although high-grade gliomas tended to have higher lactate values than did low-grade gliomas, no statistically significantdifference between malignancies was detected.DiscussionSignificant differences between tumor and normal tissue was observed in the spectral pattern of image-guided water suppressed in vivo 1HMRS at 3 Tesla system. Proton MR spectroscopy at 3T MRI system was tested for its validity and limitations in the evaluation of malignancy ofgliomas. Histologic grading of glioma was, to a great extent, predictable by Cho/Cr value. In our 3T MRI/MRS facility, the spectral differencesin various tumor types and keeping in data bank for further detail analysis and interpretation, eventually for the accurate and sensitivediagnosis. A method that could precisely assign observed lesions to specific diagnostic grading could reduce the need for surgical biopsy andthus reduce patient morbidity and mortality. The present results indicate the usefulness of proton MR spectroscopy in the evaluation of tumormalignancy noninvasively. Therefore, we suggest that in vivo 1H MRS can improve the high quality of diagnostic level in terms of biochemicaland metabolic process in neoplastic tissue.References1. Arnold DL, Shoubridge EA, Villemure JG, Feindel W. Proton and phosphorous magnetic resonance spectroscopy of human astrocytomas invivo: Preliminary observations on tumor grading. NMR Biomed 1990;3:184-1892. Bruhn H, Frahm J, Gyngell ML, et al. Noninvasive differentiation of tumors with use of localized 1H MR spectroscopy in vivo: Initialexperience in patients with cerebral tumors. Radiology 1989;172:541-5483. Langkowski JH, Wieland J, Bomsdorf H, et al. Preoperative localized in vivo proton spectroscopy in cerebral tumors at 4.0 Tesla: firstresults. Magn Reson Imaging 1989;7:547-5554. Herholz K, Heindel W, Luyten PR, et al. In vivo imaging of glucose consumption and lactate concentration in human gliomas. Ann Neurol1992;31:319-3275. Demaerel P, Johannik K, van Hecke P, et al. Localized 1H NMR spectroscopy in fifty cases of newly diagnosed intracranial tumors. JComput Assist Tomogr 1991;15:67-76 1292Proc. Intl. Soc. Mag. Reson. Med. 11 (2003)