Helical CT : Principles and Technical Considerations 1
نویسندگان
چکیده
. INTRODUCTION Helical computed tomography (CT) offers several technical advantages that have revolutionized body CT. Use of helical technology has improved established CT applications by the minimization of motion artifacts, the elimination of respiratory misregistration artifacts (1,2), and the production of overlapping images without additional x-ray exposure (3-5). New applications involving multidimensional imaging have been made possible by these advancements, of which CT angiography is but one example (6-8). High-quality threedimensional images can be generated from multipie overlapping transaxial images acquired in a single breath hold. Helical CT involves simultaneous translatory movement of the patient through the gantry while the x-ray source rotates such that continuous data acquisition is achieved throughout the volume of interest (1 ,2). The x ray traces a helix on the patient’s surface, resulting in a helix of raw projection data from which planar images must be generated (Fig 1). Each rotation ofthe xray tube can be thought of as generating data specifIc to an angled plane of section (9). To achieve a true transaxial image, data points above and below the desired plane of section must be interpolated to estimate the data value in the transaxial plane (Fig 2). As a benefit, the interval between reconstructed transaxial images can be chosen arbitrarily and retrospectively.
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تاریخ انتشار 2005