Purpose or Case Report: Mediastinal tumors comprise a range of congenital, neoplastic and inflammatory tumors. While many benign and malignant lesions can be differentiated by CT appearance and attenuation values, many cannot be reliably separated. The purpose of this paper is to evaluate the feasibility of dual-energy computed tomography (DECT) in differentiating a spectrum of mediastinal tumors in children
Methods & Materials: We retrospectively evaluated 19 patients with 20 mediastinal tumors (9 males, 11 females) with mean age of 14.6 years (1-22 years). All patients underwent a single-phase DECT using Siemens Somatom dual source scanner. CT scans were performed with dose reduction technologies. The analyses included longest tumor diameter and quantitative analyses of CT attenuation values in Hounsfield units (HU) and the iodine concentrations (mg/ml). The 80 kVp image was used to measure HUs, and the iodine map was used to measure iodine concentrations. For the quantitative analyses, a region of interest (ROI) was drawn to be as large as possible in two different areas of the tumors and the values averaged. Pathologic results were used for final diagnosis in untreated tumors and functional imaging studies including PET (n= 9) and MIBG (n= 2) scans were used in treated tumors. We used Fisher exact test for statistical analysis.
Results: five patients had benign tumors:2 neurogenic and 3 inflammatory myoblastic tumors. Nine had untreated malignant tumors: 6 lymphomas, 2 neuroblastomas, 1 germ cell tumor. Six had treated lymphomas. The mean diameters for benign, untreated and treated tumors were 5.3 cm, 5.1cm, 4.1cm. The mean attenuation values were 47.14, 81.09 and 49.9 respectively (p =0.05). The mean iodine concentration measurements in benign, untreated malignancy and treated tumors were 0.42 mg/ml, 2.06 and 0.23 respectively (p < 0.01). The best cut-off threshold iodine concentration for differentiating benign and treated tumors from malignant tumors was 1.1 mg/ml.
Conclusions: Results of this study show that dual-energy CT using a quantitative analytic methodology can differentiate benign, including treated tumors, from malignant tumors in children. We believe that dual-energy CT can be a helpful complimentary tool for diagnosis in cases where standard contrast CT is inconclusive. It also has the potential to be a valuable modality to assess response to treatment.