正常颅脑能谱CT成像各单能量图像质量的分析研究

Spectral CT imaging of normal brain: a study on quality of optimal monochromatic image

目的:研究能谱CT成像在显示正常颅脑结构时的最佳单能量图,从而提高图像质量。方法:对60例经宝石能谱CT扫描的患者图像进行回顾性分析,将所得原始图像在40、45、50、55、60、65、70、75、80、85、90、95、100、105、110、115、120、130、140 ke V下重建19组CT图像。选取半卵圆中心、基底节区、小脑最大层面,分别测量每一组图像各感兴趣区的CT值及噪声,以计算不同ke V下的对比噪声比(contrast to noise ratio,CNR)、信噪比(signal noise ratio,SNR)。结果:小脑皮质、髓质的最佳SNR均为70 ke V,最大CNR为40 ke V;半卵圆中心层面的皮质、髓质在70 ke V具有最佳SNR,在40 ke V具有最大CNR;在基底节区层面中,内囊在70 ke V具有最佳SNR,苍白球在65 ke V具有最佳SNR,该层面在50 ke V具有最大CNR。除小脑的最大CNR比70 ke V的CNR大(P=0.000)外,基底节区层面及半卵圆中心层面的最大CNR与70 ke V的CNR没有统计学差异(P分别为0.066、0.249)。结论:进行颅脑CT能谱成像时,70 ke V是最佳单能量水平,能够清晰地显示颅脑的结构。

Objective To study the quality of the optimal monochromatic image of normal brain by spectral CT. Methods Totally 60 cases were detected with spectral CT scanner, whose images were analyzed retrospectively, and 19 sets of monochromatic images were obtained from a single GSI acquisition： 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105,110, 115, 120, 130, 140 ke V respectively, in which sets the centrum ovale, basal ganglia region, cerebellum levels were selected and measured, including CT value, noise on each set of images, and the contrast to noise ratios and signal to noise ratios were calculated. Results The best signal to noise ratios of cerebellar cortex and medulla were 70 ke V, the maximum contrast to noise and signal of cerebel was 40 ke V; The best signal to noise ratios of centrum semiovale cortex and medulla were 70 ke V, the maximum contrast to noise and signal of centrum semiovale was 40 ke V; In the level of the basal ganglia capsule,the best signal to noise ratios of capsula interna and globus pallidus were 70 and 65 ke V respectively, the maximum contrast to noise and signal of centrum semiovale was 50 ke V. There was statistically significant difference between the value of the maximum contrast to noise and signal of the cerebel and that of 70 ke V（P =0.000）, which had no statistically significant difference in centrum semiovale and basal ganglia capsule（P =0.066 and 0.249 respectively）. Conclusion The optimal monochromatic energy level of normal brain is 70 ke V on spectral CT image, which can display anatomic structure of brain clearly.