11/9/2022 0 Comments Shift all peaks inmr![]() ![]() A P-value of <0.05 was considered as statistically significant. The sensitivity, specificity, positive-predictive value (PPV), negative-predictive value (NPV), and diagnostic accuracy with each metabolite were assessed using the cutoff value obtained with minimum C1 error from the ROC analysis. The area under the ROC curve was calculated to summarize the performance of each metabolite in differentiating the two grades of glioma. Receiver-operating characteristic (ROC) curve analysis was done to evaluate the performance of the metabolite ratios in differentiating high-grade and low-grade gliomas. Comparisons of the categorical variables between the two groups were performed using the chi-squared test. The metabolite ratios between the low-grade and high-grade gliomas were compared using Mann–Whitney U-test. The metabolite ratios of Cho/Cr, Cho/NAA, NAA/Cr, and lactate/Cr were calculated. Descriptive data were presented in the form of frequency, percentage, mean, median, standard deviation, and quartiles. The data collected were entered into a Microsoft excel spreadsheet and analyzed using IBM SPSS Statistics, Version 22 (Armonk, NY: IBM Corp). Lactate/Cr was used instead of lipid-lactate/Cr used by other studies in literature because lipid peak was not consistently seen in most of the cases at intermediate TE. Maximal Cho/Cr, Cho/NAA and lactate/Cr and minimum NAA/Cr ratios were obtained from spectral maps. The metabolite peaks were assigned as follows: Cho, 3.22 ppm Cr, 3.02 ppm NAA, 2.02 ppm lactate was identified at 1.33 ppm by its characteristic doublet and inversion at intermediate TE. Lipid peak was demonstrated at 0.9–1.3 ppm without inversion at intermediate TE. Metabolite ratios were obtained for Cho/Cr, Cho/NAA, NAA/Cr, and lactate/Cr. The time taken to acquire spectra was around 8 min. A 16 × 16 phase-encoding matrix was used to obtain 8 × 8 arrays of spectra in the VOI, with an in-plane resolution of 1 × 1 cm and a voxel size of 1 × 1 × 1.5 cm 3. In our institution, we used Multivoxel MR spectroscopy technique (chemical shift method) at intermediate TE of −135 ms.Ī typical VOI consisted of an 8 × 8 cm region placed within a 16 × 16 cm field of view on a 1.5-cm transverse section. Our prospective study aimed to analyze the usefulness of proton MR spectroscopy in grading of glioma and to correlate various metabolite ratios like choline/creatine, choline/N-acetylaspartate, N-acetylaspartate/creatine, and lactate/creatine with the histopathological grades of glioma.Īfter the conventional MRI volume of interest from the lesion (VOI) was selected from T1 post-contrast images, VOI was selected from the solid part of lesion with edges of the voxel well within the mass and in most of the cases perilesional edema was included within the VOI. VOI was carefully selected so that it will not include areas of hemorrhage or calcification and unintended areas like ventricles, calvarium, and so on. Biochemical changes in the metabolism of tumor cells related to malignant transformation are reflected in changes of particular metabolite concentration in the tumor tissue. MRS also has many diagnostic applications in neurosciences to support the diagnosis in conditions like demyelination, infections, and dementia and in postradiotherapy cases. Because glial tumors have some specific metabolic characteristics that differ according to the grade of tumor, there is a potential for MR spectroscopy to increase the sensitivity of routinely used diagnostic imaging. Results are usually expressed as metabolite ratios rather than absolute metabolite concentrations. Magnetic resonance spectroscopy (MRS) provides useful information regarding metabolic composition in the tissues, and advanced spectroscopic methods are used to quantify markers of tumor membrane turnover and proliferation (e.g., choline (Cho)), energy homoeostasis (e.g., creatine (Cr)), intact glioneuronal structures (e.g., N-acetylaspartate (NAA)), and necrosis (e.g., lactate (Lac) or lipids). ![]()
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