The application research of spectral CT for reducing beam-hardening artifacts around axillary vein and subclavian vein due to the utility of contrast agent in the chest enhanced CT scan

Objective To assess the value of monochromatic images of gemstone spectral CT for reducing beam-hardening artifacts (BHA) around axillary vein and subclavian vein due to the utility of contrast agent in the chest enhanced CT scan. Methods Images of the arterial phase were acquired using gemstone spectral imaging (GSI) mode in 49 adult patients who underwent chest enhanced CT scan. All data were transferred to AW4.6 workstation to generate 1 set of 140 kVp conventional polychromatic images and 11 sets of monochromatic images in 40—140 keV. The measurement and comparison of image noise, contrast to noise ratio (CNR), average BHA and the CT value difference were performed between polychromatic image and each monochromatic image with one-way ANOVA. Results Compared with the 140 kVp conventional polychromatic images and 11 sets of monochromatic images, the soft tissue contrast of 70 keV images was closer to the traditional imaging method, with the highest CNR (7.2±1.8, F=11.5, P< 0.01). But at the same time, the BHA and CT value difference of 70 keV images were obviously increased [(47.1±19.0) and (71.7±60.9)HU, respectively] and the image quality was influenced greatly by the artifacts. At 110 keV, the BHA could be minimized(P<0.05) and the CT value difference was the lowest [(20.9±6.5) and (10.0±7.7)HU, respectively]. Even though the CNR of 110 keV images was lower than that of 70 keV, but there was no significant difference between these two group (P=0.099). Conclusions The monochromatic images of Gemstone spectral CT can effectively reduce beam-hardening artifacts of iodine contrast agent and improve the image quality. In clinical application, it can be combined with 110 keV and 70 keV images to make the diagnosis. Key words: Tomography, X-ray computed; Contrast agent; Axillary vein; Subclavian vein