| [Objective According to WHO classification of tumors of the Nervous System, diffuse astrocytomas, oligodendrogliomas and oligoastrocytomas all belong to grade II. We define them as three subtypes of low grade gliomas (WHO Grade II). Differential diagnosis of low grade glioma subtypes and gliomatosis cerebri from low grade gliomas based on conventional MR imaging alone are still challenging problems. Proton magnetic resonance spectroscopy (1HMRS) gives completely different information related to cell membrane proliferation, neuronal damage, energy metabolism and necrotic transformation of brain or tumor tissues. Furthermore, it has been common practice to use metabolite ratios such as NAA/Cr and Cho/Cr for quantification, instead of absolute concentrations, but it is limited. Our purpose was to evaluate if utility of changes in NAA, Cho and Cr of 'HMRS could enhance our ability to differentiate between these entities.[Materials and Methods] Twenty-eight patients with histopathologically verified low grade gliomas (WHO grade II ) (including twelve, diffuse astrocytomas; eight, oligodendrogliomas and eight, oligoastrocytomas) and eight patients with histopathologically verified gliomatosis cerebri were performed with4routine precontrast, postcontrast MRI examinations and single-voxel MR spectroscopy (PROBE/SV)(TE=270ms). Eight patients of diffuse astrocytomas, six patients of oligodendrogliomas, four patients of oligoastrocytomas and four patients of gliomatosis cerebri also underwent multivoxel proton MR spectroscopy imaging (PROBE/SI). Metabolite ratio analyses such as NAA/Cr, Cho/Cr and Cho/NAA were studied, and the metabolite signals of NAA, Cho and Cr in the lesions were compared with those in the contralateral centrum semiovale and in the corresponding brain sites in twenty-eight control subjects to separately obtain the changes in NAA, Cho and Cr. Moreover, coefficients of variation (CVs) of the ratios and the metabolite changes in each type of tumors were calculated. Student / test and rank sum test (Kruskal- Wallis H method and Mann- Whitney U method) were used for statistical comparisons. P value less than 0.05 was considered significant.[Results] MRS could differentiate low grade gliomas from contralateral normal brain tissues. Concentration of NAA (7.52?.84, 16.35?.94) (mean盨D) and Cho (11.51?.77, 7.19?.69) as well as the ratios of NAA/Cr (1.17?.38, 1.98?.33) and Cho/Cr (1.79?.63, 1.06?.25) were all statistically significantThe ratios of NAA/Cr (1.21?.45, 1.03?.25, and 1.13?.21) and Cho/Cr (1.85?.67, 1.69?.54, and 1.75?.61) were not statistically significant among diffuse astrocytomas, oligodendrogliomas and oligoastrocytomas (P = 0.426, P=0.568) . However, Cho% and Cr% have significant differences between diffuse astrocytomas (69.6%?7.8, -43.4%?1.9) and oligodendrogliomas(140.4%?9.5, 16.5%?.2) as well as diffuse astrocytomas and oligoastrocytomas (157.1%?2.3, 12.8%?.2) (PO.01). No significant differences between oligodendrogliomas and oligoastrocytomas were found.NAA/Cr, Cho/Cr and Cho/NAA have significant differences (P<0.05) between GC (1.08?.29, 1.54?.37 and 1.38?.31) and the control group (1.86?.23, 1.03?.36 and 0.65?.17), but no significant differences between GC and low grade gliomas (1.17?.38, 1.79?.48 and 1.46?.41) (P>0.05).The degree of reduced NAA in GC was -48.76%?8.72, the degrees of elevated Cho and Cr were 63.54%?4.04 and 41.52%?8.93. Compared with low grade gliomas (-67.25%fcll.68, 114.82%?3.31 and -7.27%?1.73), changes of Cho and Cr were statistically significant (P=0.019, P = 0.023) and changes of NAA was not statistically significant between them (P=0.248).The median CVs of the NAA/Cr and Cho/Cr ratios were larger than the median CVs of the individual changes of metabolite NAA, Cho and Cr levels. Student / test showed significant differences (P<0.05) between them in low grade glioma subtypes and GC apart from the CV between the change of NAA level and NAA/Cr in oligoastrocytomas. [ Conclusions ]1. MR spectra of low grade gliomas can...
|
PDF Full Text Request