| Objective:To prospectively investigate the characterization of proton(~1H) magnetic resonance(MR) spectroscopy at 3.0 T in adrenal masses,and also initially evaluated the value of ~1H MRS and chemical shift imaging(CSI) in distinguishing adrenal adenomas from nonadenomas.Subjects and Methods:Thirty-eight patients with unilateral adrenal masses which were proved by histopathology or clinic entered the study and were examined with a 3.0 T single voxel ~1H MRS and CSI.Twenty-two patients had adenomas,16 nonadenomas consisted of 11 metastases,two myelolipoma,two pheochromocytomas and one schwannomas.Metabolite peaks in MRS between adenomas and nonadenomas were analyzed.The ratios of peak area(P) of all peaks at lipids(0.9-5.4 ppm) to lipids (0.9-5.4 ppm) and water(P lipid/P[lipid + water]) and ASR were compared and evaluated with Mann-Whitney U test.A threshold of more than 20%MR signal intensity drop and lipid resonances in ~1H MRS for the diagnostic standard of adenomas,descriptive statistical data including sensitivity,specificity,accuracy, positive predictive value(PPV) and negative predictive value(NPV) were determined. We used choline resonances as a diagnosis standard to diagnose adrenal masses as malignancy tumor,descriptive statistical data including sensitivity,specificity, accuracy,positive predictive value(PPV) and negative predictive value(NPV) were measured for ~1H MRS.A P value of less than.05 indicated significance for all tests.Results:1.Characterization of adenomas with single voxel ~1H MRSAll twenty-two adenomas(including 3 lipid-poor adenomas in chemical shift imaging) had a unique MR spectral signature,showing the lipid resonances at 0.9 ppm,1.3 ppm,1.9-2.1 ppm,2.7-2.9 ppm and 5.3-5.4 ppm,a residual water resonance was displayed at 4.7ppm.The adenomas did not have choline resonance.2.Characterization of nonadenomas with single voxel ~1H MRS(1) Characterization of nonadenomas(not including myelolipoma) with single voxel ~1H MRS The 14 nonadenomas displayed choline resonance at 3.2 ppm,lipid resonance at 1.3ppm and residual water resonance at 4.7 ppm,but 2 metastatic tumors did not present choline resonance. (2) Characterization of myelolipoma with single voxel ~1H MRSSpectra from the two myelolipoma had only the most prominent lipid resonance in the range of 1.3-1.5 ppm,residual water resonance at 4.7 ppm,have neither other lipid nor choline peak.3.Comparison of the Metabolite ratios between adenomas and nonadenomasThe ratios of peak area(P) of all peaks at lipid(0.9-5.4ppm) to lipid(0.9-5.4ppm) and water(P lipid/ P[lipid + water]) for adenomas and nonadenomas were 36.91%±16.72%and 4.21%±2.86%,respectively.The ratios were significantly different between adenomas and nonadenomas(p＜0.0001).4.Comparison of the efficacy to adenomas with ~1H MRS and ASRSensitivity,specificity,accuracy,PPV and NPV for ~1H MRS and ASR in detecting adenomas were 100%,100%,100%,100%,100%and 86.36%,92.86%, 88.89%,100%,81.25%,respectively.5.Comparison of the efficacy to malignancy adrenal tumor with ~1H MRSSensitivity,specificity,accuracy,PPV and NPV for ~1H MRS in detecting adrenal malignancy tumor were 83.3%,91.7%,88.9%,83.3%and 91.7%,respectively.Conclusion:1.Adenomas had relatively characteristic spectra.A standard of the common lipid resonances for the diagnosis of adenoma provided a great sensitivity,specificity and accuracy.Lipid resonances could ascertain the lipid composition of adenomas.2.Myelolipoma also had relatively characteristic spectra.It had only the most prominent lipid resonance in the range of 1.3-1.5ppm,residual water resonance at 4.7ppm,neither other lipid nor choline peak.3.Single voxel proton MR spectroscopy had more Sensitivity,specificity and accuracy for adenomas than CSI.4.Single voxel proton MR spectroscopy also had great Sensitivity,specificity and accuracy for adrenal malignancy tumor,while not discriminate other types of nonadenomas. |
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