The Application Values Of Using Dual-Energy Scan In Diagnosis Of The Adrenal Adenoma With Dual-Source CT

Part One Clinical value of dual-energy virtual non-contrast of dual-source CT for adrenal adenomaObjective:To explore the feasibility of using virtual non-contrast(VNC) images in diagnosis of adrenal adenoma in dual-energy scans, and evaluate the sensitivity, specificity, and accuracy of VNC images for the lipid-rich adenoma and lipid-poor adenoma.Materials and methods:The clinical manifestations and CT images for 30 patients with 31 lesions confirmed by pathological results from surgery were reviewed retrospectively. All of the patients were examined by a pre-contrast scan(true non contrast; TNC) and then arterial and venous phase enhanced scan. Then enhanced examinations were performed with dual-energy scan mode(SOMATOM Flash, Siemens Healthcare, Forchheim, Germany). The dedicated post processing application “Liver VNC” was used to get VNC images at the arterial and venous phase respectively. ①Mean CT values, signal-to-noise ratio, subjective image quality, and radiation dose were compared between routine TNC and VNC. ②The correlation between TNC and VNC images of the adrenal adenoma was evaluated. Sensitivity, specificity and accuracy of VNC images for the characterization of lipid-rich adenoma and lipid-poor adenoma were calculated from chi-square tables of contingency.Results:①No significant differences were seen for mean CT values in normal adrenal tissue, adrenal adenoma and the muscles of posterior spine between TNC and VNC images(p>0.05),except the abdominal aortic and spleen which the mean CT values in VNC images was higher than TNC image and the differences were statistically significant(p<0.05).②SNR of all tissues in VNC images were higher than that in TNC image, and the differences were statistically significant(p<0.05) expect the abdominal aortic(p >0.05).③The subjective score of VNC images was lower than that of TNC image, but the difference was no statistically significant(p >0.05)and all images received score of more than 3. ④The radiation dose of VNC images was lower than that of TNC(p<0.05).⑤A positive correlation was found for CT values of adrenal adenoma between TNC and VNC images. ⑥Sensitivity, specificity, and accuracy from VNC images of arterial phase for the characterization of lipid-rich adenoma and lipid-poor adenoma were 86.9%、100%、90.3%,100%、86.9%、90.3% respectively and from venous phase were 60.9%、87.5%、67.7%,87.5%、60.9%、67.7% respectively.Conclusions:The VNC image calculated from contrast-enhanced dual-energy CT showed a good correlation with TNC image. Image quality of VNC is good enough to evaluate the adrenal adenoma. VNC image of arterial phase had a better sensitivity, specificity, and accuracy to diagnosis the lipid-rich adenoma and lipid-poor adenoma than the venous phase. VNC images have a potential to replace the TNC images to diagnose the adrenal adenoma and thus reduce the patient’s radiation dose.Part two The clinical value of dual-energy scans in differentiating adrenal adenoma from metastasisObjective:This study is to explore the feasibility of using dual-energy scans to differentiate adrenal adenoma from metastasis, and evaluate the clinical value of dual energy parameters and curves in identifying adrenal adenoma from metastases.Materials and methods:The clinical manifestations and CT images of 40 patients with 45 adrenal lesions were reviewed retrospectively, including 31 adenomas and 14 metastases. All patients underwent dual-energy scans with dual-source CT scanner.①Used dual energy post processing application“Liver VNC” to obtain iodine map from two enhanced phases(arterial phase and venous phase respectively), the dual energy parameters including iodine concentration(IC), iodine concentration difference(ICD=ICVP-ICAP) and normalized iodine concentration(NIC) were calculated and compared between two groups.②Used another dual energy post processing application“Monoenergetic”to obtain a series mono-energetic imaging of 40~190Ke V, measure the CT values of lesions on different energy level in these two groups.Analyzed the difference of monoenergetic curve between adrenal adenomas and metastases.③Used ROC curve to evaluate iodine concentration, normalized iodine concentration in differentiating adrenal adenomas and metastases.Results:①The iodine concentration and normalized iodine concentration of metastases were significantly higher than those of adrenal adenomas in arterial and venous phase(p <0.05). No significant difference was found for the average iodine concentration difference(ICD) in arterial and venous phase between two groups of lesions(p>0.05). ROC curve in analyzing the ICs and NICs showed that the parameters of venous phase had higher sensitivity and spectificity than that of arterial phase and the threshold was 1.95 mg/ml(IC) and 0.465(NIC) respectively.②CT values on different energy level of metastases were higher than those of adrenal adenomas, except on 40 Ke V and 50 Ke V from arterial phase other differences are statistically significant(p<0.05).③Both of the adrenal adenomas and metastases monoenergetic curve were declining from 40 ke V to 190 ke V and the metastases curve were above the adrenal adenomas curve both in arterial and venous phase on all energy levels.Conclusions:Iodine concentration and spectrum curve from dual-source dual energy scans can help differentiate adrenal adenomas from metastases, and provide a new insight in diagnosis.