Thoracic lymph node delineation at dose-reduced (1 mSv) dose-modulated contrast enhanced MDCT: a retrospective pilot study.

PURPOSE: To compare contrast-enhanced low-dose multidetector-row computed tomography (CE-LDCT) of the chest with unenhanced (UN-) LDCT and contrast-enhanced standard-dose CT (CE-SDCT) in regard to the delineation of intrathoracic lymph nodes. MATERIALS AND METHODS: Based on the international association for the study of lung cancer (IASLC) grouping of thoracic lymph nodes, two independent radiologists retrospectively assessed lymph node delineation in 9 CE-LDCTs (64 rows, 120 KV, p < 30 mAs/slice) and in 2 control groups of 36 UN-LDCTs and 36 CE-SDCTs, each matched for gender, age, chest/lung diameters, and clinical history. At a significance level of p < 0.025 (Bonferroni-correction for two control groups), two-tailed Chi-square and Fisher's exact tests were applied. For the evaluation of the inter-observer agreement, Cohen's kappa statistics were used. RESULTS: CE-LDCT delineated lymph node groups significantly more often than UN-LDCT, in general (p < 0.001) and individually in the subcarinal (p < 0.025), the hilar (p < 0.001), and the peripheral lung (p < 0.001) zones. There were no significant differences in lymph node delineation between CE-LDCT and CE-SDCT. Inter-observer agreement was substantial to perfect for all lymph node zones (κ 0.64-1.0). Measurable lymph nodes did not significantly differ in size between cases and controls. CONCLUSION: At CE-LDCT of the chest, delineation of mediastinal and hilar lymph node groups was superior to UN-LDCT and similar to CE-SDCT. CE-LDCT may be a promising alternative for patients with non-malignant lung disease, unclear chest X-ray findings, or the need for follow-up.