Improved sensitivity of dynamic CT with a new visualization method for radial distribution of lung nodule enhancement

摘要

For differential diagnosis of pulmonary nodules, assessment of contrast enhancement at chest CT scans after administration of contrast agent has been suggested. Likelihood of malignancy is considered very low if the contrast enhancement is lower than a certain threshold (10–20 HU). Automated average density measurement methods have been developed for that purpose. However, a certain fraction of malignant nodules does not exhibit significant enhancement when averaged over the whole nodule volume. The purpose of this paper is to test a new method for reduction of false negative results. We have investigated a method of showing not only a single averaged contrast enhancement number, but a more detailed enhancement curve for each nodule, showing the enhancement as a function of distance to boundary. A test set consisting of 11 malignant and 11 benign pulmonary lesions was used for validation, with diagnoses known from biopsy or follow-up for more than 24 months. For each nodule dynamic CT scans were available: the unenhanced native scan and scans after 60, 120, 180 and 240 seconds after onset of contrast injection (1 – 4 mm reconstructed slice thickness). The suggested method for measurement and visualization of contrast enhancement as radially resolved curves has reduced false negative results (apparently unenhancing but truly malignant nodules), and thus improved sensitivity. It proved to be a valuable tool for differential diagnosis between malignant and benign lesions using dynamic CT.