Imaging Studies To Identify Adrenal Adipose Adenomas And Pheochromocytoma

Part 1 Added value of Spectral CT imaging in differential diagnosis of Lipid-poor Adrenal Adenomas and PheochromocytomasObjective To investigate spectral CT imaging features of lipid-poor adrenal adenoma and pheochromocytoma and to assess the value of spectral CT for differentiating them.Methods This was a retrospective study with images from a radiology database. 18 pathologically proven pheochromocytomas were compared with 30 lipid-poor adrenal adenomas(13 cases were proved by pathologically, 17 cases were proved by CT), these 17 cases should meet the demands as follows:(1) unenhanced attenuation >10HU,(2)absolute washout >60% or relative washout >40% and absence of clinical indicators of pheochromocytoma). Patients underwent arterial phase(AP) and portal venous phase(PP) scans with dual energy spectral CT(DEs CT) mode. Both the material-decomposition images, and monochromatic image sets with photon energies from 40 to 140 ke V were reconstructed. Quantitative parameters [CT number as function of photon energies and normalized iodine concentration(NIC) for the two lesion types] were calculated and compared using two-sample t test. Two readers blinded to the pathologic results qualitatively assessed lesion types using the conventional CT characteristics. Sensitivity and specificity were compared between the qualitative and quantitative studies.Results Mean tumor size of lipid-poor adrenal adenomas and pheochromocytomas was 2.3cm and 3.2cm, respectively. Pheochromocytomas had higher CT number than lipidpoor adrenal adenomas at every energy levels in both AP and PP(p<0.05), with greater differences at lower energies. NIC values were lower in lipid-poor adrenal adenomas than in pheochromocytomas: 0.16±0.08 vs. 0.32±0.14 in AP, p<0.001 and 0.45±0.16 vs. 0.62±0.23 in PP, p=0.012. The quantitative NIC measurements provided higher sensitivity(82.4%) and specificity(85.2%) for differentiating lipid-poor adrenal adenoma from pheochromocytoma compared with those(72.2% and 60.0%, respectively) of conventional qualitative CT image analysis.Conclusion The lipid-poor adrenal adenoma and pheochromocytoma had distinctively different characteristics on CT spectral imaging.NIC obtained in spectral CT imaging provided the highest sensitivity and specificity for the differential diagnosis between lipidpoor adrenal adenoma and pheochromocytoma.Part2 Application of MR functional imaging in evaluation of lipid-poor adrenal adenomas and pheochromocytomasObjective To investigate 1.5T MR imaging features of lipid-poor adrenal adenoma and pheochromocytoma and to assess the value of SII(Signal intensity index), ASR(adrenalto-spleen ratio),FF(fat fraction) and ADC(apparent diffusion coefficient)for differentiating them.Methods To retrospectively svaluated 23 cases of lipid-poor adrenal adenoma and pheochromocytoma in 23 patients. 10 pathologically proven pheochromocytomas were compared with 13 lipid-poor adrenal adenomas(6 cases were proved by pathologically, 7 cases were proved by CT), these 7 cases should meet the demands as follows:(1) unenhanced attenuation >10HU,(2)absolute washout >60% or relative washout >40% and absence of clinical indicators of pheochromocytoma). Signal intensity index(SII), adrenal-to-spleen ratio(ASR), fat fraction(FF) and apparent diffusion coefficient(ADC) on chemical shift imaging and diffusion-weighted imaging were measured. A standard non-parametric test of two independent samples(Mann-Whitney U test) were used to analysis. Receiver operating characteristic(ROC) analysis was used to determine the optimal diagnosis threshold point, the sensitivity,specificity and area under the cover(AUC) were recorder or calculated.Results The mean SII, ASR,FF and ADC value of leisions were listed below : lipid-poor adrenal adenomas(n=13): 19.88 %, 0.79, 14.07% and 1.11×10-3mm2/s; pheochromocytomas(n=10): 5.37%,0.92,8.36% and 1.17×10-3mm2/s. There were significant differences between lipid-poor adrenal adenomas and pheochromocytomas for SII ?ASR and FF. The optimal diagnosis threshold point of SII ?ASR and FF for lipidpoor adrenal adenoma were 13.9%?0.88 and 12.0% by ROC curve analysis, respectively, and the sensitivity were 76.9%?69.2% and 58.3%,specificity were 100%?90% and 100%, respectively. There was no significant difference for ADC values between ipidpoor adrenal adenomas and pheochromocytomas.Conclusions CSI is valuable for diagnosis and differentiation between lipid-poor adrenal adenoma and pheochromocytoma.