Detection of Pulmonary Nodules Using Helical CT

Abstract

We compared conventional CT (C-CT) and helical CT (H-CT) with regard to their capabilities in the detection of lesions in the lung fields.The subjects were 15 patients with metastatic lung tumors in whom nodules were detected by chest radiography. To scan the entire lung, we first employed C-CT (10-mm slice thickness, 10-mm slide), and then used H-CT with table speeds of 20mm/sec and 25mm/sec. We assessed each type of image to compare detection capabilities in the lung. In terms of the number of lesions detected by C-CT which could also be visualized on H-CT images reconstructed at 25mm, 20mm, 12.5mm, and 10-mm intervals, and also in terms of the number of lesions detected by C-CT which could also be visualized on H-CT images reconstructed at 20mm and 10-mm intervals using the 180-degree or 360-degree algorithm.
On images at intervals of 10-mm (10-mm images), 147 of the 152 lesions were detected. Lesions were detected nearly as well as by C-CT. On 10-mm images, no difference was seen in the detection capability between 360-degree and 180-degree reconstruction.However, images acquired using the 180-degree algorithm depicted lesions with greater sharpness than those acquired using the 360-degree algorithm. In conclusion, H-CT may be useful in detecting pulmonary nodules, and the optimal conditions for maximizing detectability of nodules are as follows: table speed, 20mm/sec;and image reconstruction, 10mm for the 180-degree algorithm.