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Iodine concentration of healthy lymph nodes of neck, axilla, and groin in dual-energy computed tomography

Background Lymph nodes (LN) are examined in every computed tomography (CT) scan. Until now, an evaluation is only possible based on morphological criteria. With dual-energy CT (DECT) systems, iodine concentration (IC) can be measured which could conduct in an improved diagnostic evaluation of LNs. Purpose To define standard values for IC of cervical, axillary, and inguinal LNs in DECT. Material and Methods Imaging data of 297 patients who received a DECT scan of the neck, thorax, abdomen–pelvis, or a combination of those in a portal-venous phase were retrospectively collected from the institutional PACS. No present history of malignancy, inflammation, or trauma in the examined region was present. For each examined region, the data of 99 patients were used. The IC of the three largest LNs, the main artery, the main vein, and a local muscle of the examined area was measured, respectively. Results Normalization of the IC of LNs to the artery, vein, muscle, or a combination of those did not lead to a decreased value-range. The smallest range and confidence interval (CI) of IC was found when using absolute values of IC for each region. Hereby, mean values (95% CI) for IC of LN were found: 2.09 mg/mL (2.00–2.18 mg/mL) for neck, 1.24 mg/mL (1.16–1.33 mg/mL) for axilla, and 1.11 mg/mL (1.04–1.17 mg/mL) for groin. Conclusion The present study suggests standard values for IC of LNs in dual-layer CT could be used to differentiate between healthy and pathological lymph nodes, considering the used contrast injection protocol.