Pulmonary Nodules: Contrast-Enhanced Volumetric Variation at Different CT Scan Delays

OBJECTIVE. The purpose of this study was to assess the effects of IV contrast medium and different CT scan delays on volumetric measurements of pulmonary nodule. MATERIALS AND METHODS. Automated volumes of 35 pulmonary nodules were calculated with two dedicated software packages (designated as software A and software B) for each unenhanced and contrast-enhanced CT scan at 30-, 60-, 120-, 180-, and 300-second delays (injection protocol, 2 mL/s and 2 mL/kg). Nodule attenuation was also determined. Differences between unenhanced and contrast-enhanced volumes were analyzed by Wilcoxon's signed rank test. Contrast-enhanced volume ratio was calculated as the ratio between contrast-enhanced and unenhanced nodule volume. RESULTS. Contrast-enhanced volumes were significantly larger than unenhanced volumes (p < 0.05) for all the timing delays except at 30 seconds for software A, and no significant differences were found among volumes measured with both software programs at different contrast-enhanced delays. Median volume ratios between contrast-enhanced and unenhanced volumes were 1.04-1.07 for software A and 1.04-1.06 for software B, and median volume ratios within different contrast-enhanced delays were 0.99-1.03 for software A and 0.99-1.04 for software B. We did not find any significant association between contrast-enhanced volume ratio and nodule diameter, site, shape, unenhanced density, or contrast-enhanced density ratio (p > 0.05). CONCLUSION. We recommend comparing volume of pulmonary nodules obtained from CT examinations only if they are all performed with or without contrast material, whereas nodule volumes obtained by use of enhanced CT performed with different scan delays are comparable.