【摘要】 目的探讨甲状腺CT平扫能谱成像时能最大限度减少图像噪声和肩部线束硬化伪影(BHAs)的最佳单能量水平。方法选择67例接受甲状腺宝石能谱CT扫描的患者,重建9组CT图像数据,即1组140 kVp混合能量图像和8组单能量图像(50、55、60、65、70、75、80和90 keV),测量并比较混合能量与单能量图像在甲状腺的背景噪声(甲状腺上极)及3个不同解剖部位(甲状腺左叶下极、右叶下极、峡部)的线束硬化伪影值。结果 70 keV、75 keV、80 keV的单能量图像的背景噪声低于140 kVp图像的背景噪声(P<0.001);50 keV、55 keV、60 keV、65 keV和90 keV的单能量图像的背景噪声高于140 kVp图像的背景噪声(P<0.001);70 keV、75 keV和80 keV图像各解剖部位的BHAs均低于140 kVp图像的BHAs(P<0.05)。上述单能量图像在甲状腺3个感兴趣区内的BHAs分别降低11.29%、11.30%、13.34%及14.92%、13.07%、14.57%和19.89%、14.59%、16.40%。70 keV、75 keV和70 keV、80 keV组间背景噪声差异均有统计学意义(P=0.017,P=0.009),75 keV和80 keV均能更低地降低噪声。75 keV和80 keV组间背景噪声差异无统计学意义(P=0.098),但80 keV组所有解剖区域的BHAs值均低于70keV和75 keV组(P<0.05)。结论甲状腺CT平扫能谱成像能有效地减低图像噪声和肩部BHAs,改善甲状腺图像质量,最佳单能量水平为80 keV。更多还原

【Abstract】 Objective To investigate the optimal monochromatic energy level for plain CT spectral imaging of thyroid in order to reduce image noise and beam hardening artifacts(BHAs) at shoulder region to the greatest possible advantage.Methods Non-enhanced gemstone spectral imaging(GSI) scanning was performed in 67 patients.Nine sets of CT image data were reconstructed,including one set of 140 kVp polychromatic images and 8 sets of monochromatic images(using 50 keV,55 keV,60 keV,65 keV,70 keV,75 keV,80 keV and 90 keV respectively).The background noise at upper pole of thyroid and BHAs at 3 anatomic regions(anus perineum of left lobe of thyroid gland,anus perineum of right lobe of thyroid gland and isthmic portion of thyroid) were measured,and the results were compared between polychromatic images and monochromatic images.BHA was defined as the square root of the noise difference between the region of interest(ROI) and background.Results The background noise of monochromatic images using 70 keV,75 keV and 80 keV was significantly lower than that of images using 140 keV(P < 0.001),while the background noise of monochromatic images using 50 keV,55 keV,60 keV,65 keV and 90 keV was significantly higher than that of monochromatic images using 140 keV(P < 0.001).BHAs at each designed anatomic sites on monochromatic images using 70 keV,75 keV and 80 keV were lower than those of images using 140 keV(P < 0.05).The reductions of BHAs of 70 keV,75 keV and 80 keV image sets at the 3 anatomic regions were 11.29%,11.30%,13.34% and 14.92%,13.07%,14.57% and 19.89%,14.59%,16.40% respectively.The differences in reducing background noise existed between 70 keV,75 keV and 70 keV,80 keV(P = 0.017,P = 0.009),while no significant difference in background noise existed between 70 keV group and 75 keV group(P =0.098),although the BHAs of 80 keV image set at all anatomic sites were lower than those of 70 keV and 75 keV images(P < 0.05).Conclusion High definition gemstone spectral CT imaging of the thyroid can effectively reduce the BHAs of shoulder as well as the image noise.For spectral CT scanning of the thyroid,the optimal monochromatic energy level is 80 keV.更多还原