Paddle-Wheel CT Display of Pulmonary Arteries and Other Lung Structures

195 ultidetector helical CT technology permits high-speed and high-resolution imaging data of the entire thorax to be acquired during a single breath-hold [1–3]. The lungs can be scanned in 12 sec with four detectors, each with collimation of 2.5 mm, or in 24 sec if 1.25-mm collimation is used [1–3]. Even faster systems are being developed [4]. State-ofthe-art equipment already provides an almost cuboidal voxel size of about 1 × 1 × 1.25 mm. Thus, reconstructed nonaxial images have a resolution comparable with that of the best axial images [1–3]. The diagnostic value of high-speed CT can be enhanced by using the original axial helical CT data set to construct a new set of planar reconstructions arranged in a “paddle-wheel” pattern, in which all planes pass through a central horizontal axis between the two lungs and hilum. In this article, we introduce the paddle-wheel CT imaging method. Paddle-Wheel Method This reconstruction method uses a paddlewheel arrangement, in which planar slabs pivot around a central horizontal axis between the lung hilum (Fig. 1A). Each slab is 15to 20-mm thick, depending on the size of the patient. Both lungs can be covered completely using 20 reconstruction image slabs, with 9° rotations between successive slabs for a total of 180° (Fig. 1B). Because all planes pass through the central axis, the large central hilar Paddle-Wheel CT Display of Pulmonary Arteries and Other Lung Structures: A New Imaging Approach