Fluctuation in measurements of pulmonary nodule under tidal volume ventilation on four-dimensional computed tomography: preliminary results.

The present study aimed to assess the feasibility of four-dimensional (4D) chest computed tomography (CT) under tidal volume ventilation and the impact of respiratory motion on quantitative analysis of CT measurements. Forty-four pulmonary nodules in patients with metastatic disease were evaluated. CT examinations were performed using a 256 multidetector-row CT (MDCT) unit. Volume data were obtained from the lower lung fields (128 mm) above the diaphragm during dynamic CT acquisition. The CT parameters used were 120 kV, 100 or 150 mA, 0.5 s(-1), and 0.5 mm collimation. Image data were reconstructed every 0.1 s during one respiratory cycle by a 180 degrees reconstruction algorithm for four independent fractions of the respiratory cycle. Pulmonary nodules were measured along their longest and shortest axes using electronic calipers. Automated volumetry was assessed using commercially available software. The diameters of long and short axes in each frame were 9.0-9.6 mm and 7.1-7.5 mm, respectively. There was fluctuation of the long axis diameters in the third fraction. The mean volume in each fraction ranged from 365 to 394 mm(3). Statistically significant fluctuation was also found in the third fraction. 4D-CT under tidal volume ventilation is feasible to determine diameter or volume of the pulmonary nodule.