We wanted to evaluate the potential role of dynamic incremental computed tomography (CT) for making the diagnosis of malignant solitary pulmonary nodule (SPN) by investigating the dynamic enhancement patterns.

Forty patients with presumed malignant SPN (diameter < 30 mm) were selected for dynamic incremental chest CT scanning. Histopathologic diagnoses of the malignant SPNs were obtained by surgical excision (n=8) and transthoracic needle biopsy (n=32), and they were squamous cell carcinoma (n=16), adenocarcinoma (n=14), small cell carcinoma (n=5), bronchioloalveolar carcinoma (n=3), and large cell carcinoma (n=2). CT scans were performed at the region of interest (ROI) of the lung nodule before and after contrast enhancement. The dynamic incremental CT scans after contrast enhancement were performed at 15 seconds, 30 seconds, 45 seconds, 60 seconds, 90 seconds, 2 minutes, 3 minutes and 4 minutes. The degree of contrast enhancement according to the time course and the time of maximum enhancement of the malignant nodules were recorded by measuring the Hounsfield Unit (HU) of the nodules at the ROI. We assessed the differences of the contrast enhancement patterns among the histopathologic subtypes of malignant SPN.

In malignant SPN, the average time of maximum contrast enhancement was 62.2±16.2 seconds, and the average degree of maximum contrast enhancement was 66.4±22.17 HU. Most primary lung cancer showed rapid contrast enhancement with slow washout. The differences of the enhancement patterns among the histopathologic subtypes were not statistically significant (p > 0.05).

Dynamic incremental chest CT was useful for making the diagnosis of malignant SPN that showed an established dynamic contrast enhancement pattern regardless of the histopatholgic subtypes.