Diagnostic potential of short echo time MR spectroscopy of gliomas with single-voxel and point-resolved spatially localised proton spectroscopy of brain

Accurate neuroimaging grading of gliomas is useful for management, but tech niques such as MRI and CT are not sufficiently reliable. Necrosis is a cons istent, decisive prognostic factor and the key diagnostic criterion for gli oblastoma multiforme. MR spectroscopy (MRS) allows noninvasive measurement of metabolites in brain tumours and mobile lipids reflect necrosis. However , short echo-time (TE) spectroscopy has been required for reliable assessme nt of lipids, since their relaxation times are very short. Recent advances have made it possible to perform short-TE MRS. We attempted to evaluate the significance of short TE spectroscopy as part of routine imaging for diagn osis and grading of gliomas. We performed TE 30 ms MRS in 25 patients with gliomas (grade II six; grade III three; grade IV, 16) and in 19 areas of he althy white matter using proton brain examination/single voxel (PROBE/ SV) and point-resolved spatially localised spectroscopy (PRESS). With short-TE spectroscopy, lipid signals were detected in all 16 tumours of grade IV, on e grade II (P = 0.0002) and none of grade III (P = 0.001). TE 136 ms MRS, c arried out in 20 of these cases, showed lipid signals in only four of 14 gr ade IV tumours and in none of the other six. N-acetylaspartate/choline (NAA /Cho) ratios were always more than 1.0 in healthy tissues and less than 1.0 in all but one of the gliomas. The mean creatine (Cr)/Cho ratio in each tu mour grade was significantly lower than in the healthy tissues. The mean Cr /Cho ratio was also significantly lower in grade TV than in grade II tumour s (P <.0005). Considerable overlap in Cr/Cho ratio was observed between gra de II and grades III and IV gliomas at long but less so at short-TE MRS. We conclude that short-TE MRS with PROBE/SV and PRESS is of value in grading gliomas.