Material differentiation by dual energy CT: initial experience

Abstract

The aim of this study was to assess the feasibility of a differentiation of iodine from other materials and of different body tissues using dual energy CT. Ten patients were scanned on a SOMATOM Definition Dual Source CT (DSCT; Siemens, Forchheim, Germany) system in dual energy mode at tube voltages of 140 and 80 kVp and a ratio of 1:3 between tube currents. Weighted CT Dose Index ranged between 7 and 8 mGy, remaining markedly below reference dose values for the respective body regions. Image post-processing with three-material decomposition was applied to differentiate iodine or collagen from other tissue. The results showed that a differentiation and depiction of contrast material distribution is possible in the brain, the lung, the liver and the kidneys with or without the underlying tissue of the organ. In angiographies, bone structures can be removed from the dataset to ease the evaluation of the vessels. The differentiation of collagen makes it possible to depict tendons and ligaments. Dual energy CT offers a more specific tissue characterization in CT and can improve the assessment of vascular disease. Further studies are required to draw conclusions on the diagnostic value of the individual applications.

Diagnosis of Pulmonary Artery Embolism: Comparison of Single-Source CT and 3rd Generation Dual-Source CT using a Dual-Energy Protocol Regarding Image Quality and Radiation Dose

“…However, we observed an increase in background noise in the DECT group, when compared to singleenergy DSCT. This effect of DECT was reported earlier by Kerl et al and Johnson et al and is due to cross-scatter radiation [10,34].…”

“…The use of two different tube energies (kV) allows for visualization of absorption characteristics of different materials, especially of those with high atomic numbers, such as iodine and calcium [10]. The dedicated advantages and possibilities of dual-energy imaging in patients with suspected pulmonary embolism have been discussed extensively in literature [11 -15].…”

“…However, the potential of the latest (third) generation scanners to further decrease radiation dose while maintaining image quality has scarcely been assessed so far [18]. Concerning first and second generation DSCT scanners, DECT was reported to carry a radiation dose similar to that of conventional single-source CT (SSCT) [10,11,19,20].…”

Brown Adipose Tissue in Humans

“…However, the tube current could not be increased quickly enough for the low tube potential setting to achieve comparable noise levels in both the low and high kV datasets. Recently, the simultaneous acquisition of dual--energy data has been introduced using multi detector CT with two X--ray tubes and rapid peak kilovoltage (kVp) switching (gemstone spectral imaging, GSI) (Flohr et al 2006;Johnson et al 2007;Petersilka et al 2008;Marin et al 2009;Ho et al 2009). Two major advantages of DECT are material decomposition and the elimination of misregistration artifacts.…”

“…The low tube potential images (typically 80 kV) are multiplied by a weighting factor and subtracted from the high voltage images (140 kV) to suppress or enhance a specific material (Kalender, Klotz and Kostaridou 1988). Reconstructed CT images acquired using the two different tube potentials can be processed with a three--material decomposition algorithm (Johnson et al 2007). The principle behind this technique is illustrated in Figure 5, where the typical HU of three materials of known densities are plotted on a graph where the y--axis is the HU at 140 kV and the x--axis is the HU at 80 kV.…”