Dual-energy CT revisited by multidetector ct: review of principles and clinical applications

Abstract

A lthough dual-energy CT (DECT) was first conceived in 1976, it has not been used widely for clinical indications (1-11). Recently, the simultaneous acquisition of dual-energy data has been introduced using multidetector CT (MDCT) with two X-ray tubes and rapid peak kilovoltage (kVp) switching (gemstone spectral imaging, GSI) (12-16). Two major advantages of DECT are material decomposition by the almost simultaneous acquisition of two image series with different kVp (80 and 140 kVp) and the elimination of misregistration artifacts. In general, noncontrast (unenhanced) images can be avoided by using the dual-energy mode for body and neurological applications; iodine can be removed from the image, and a virtual non-contrast (water) image can be acquired. The major advantage of 80-kVp compared to 140-kVp images is a higher image contrast (Fig. 1). Hounsfield unit measurements on DECT are not absolute and can change depending on the kVp used for the acquisition (at different keV). Typically, a combination of 80/140 kVp is used for DECT, but for some applications, 100/140 kVp is preferred. In this study, we summarized the clinical applications of DECT in the brain, chest and abdomen and in the cardiovascular and musculoskeletal systems (Table 1). Technique and principlesThe basic principle of dual-energy is the acquisition of 2 datasets from the same anatomic location with different kVp (usually 80 and 140 kVp) (1,2,17,18). In the early days of CT, consecutive single-slice acquisitions with different kVp were performed as a dual-energy technique, but this method suffered from breathing and partial volume artifacts (1, 2). At present, an entire body can be scanned within seconds using the DECT technique, and thus, misregistration artifacts due to breathing are eliminated.Currently, three systems are capable of the nearly simultaneous acquisition of dual-energy data during a single breath hold (12, 14, 15): 64-slice dual-source CT (Definition, Siemens Medical Systems; Erlangen, Germany), 128-slice dual-source CT (Definition Flash, Siemens Medical Systems) and high-definition 64-MDCT (Discovery 750 HD, GE Healthcare; Milwaukee, Wisconsin, USA). In the two systems available from Siemens, the two tubes (tubes A and B) use different kVp (80 and 140 kVp), and in 64-MDCT, the kVp switches from 80 to 140 kVp in less than 0.5 ms. In dual systems, there is concern regarding the susceptibility of the system to cardiac motion due to the time difference (75 or 83 ms) between the tube A and tube B acquisitions of the dual-energy data, but the dual-source CT and 64-MDCT have not been compared to evaluate this issue. The technical specifications of the DECT systems are summarized in Table 2.The images presented in this article were acquired using a 64-slice dual source CT (Definition, Siemens Medical Systems) and a 64-MDCT (Discovery 750HD, GE Healthcare). The DECT data acquired by both systems can be evaluated with a dedicated workstation using dual-energy software that ABSTRACT Although dual-energy CT (DECT) was first conceived in ...

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