探讨宝石CT能谱成像技术减除脊柱金属植入物伪影的最佳单能量

目的 评价宝石CT能谱成像技术(GSI)单能量成像在减除脊柱金属植入物伪影方面的应用价值,寻求图像质量最佳的单能量成像点。 方法 对19例带有脊柱金属植入物的患者行宝石能谱CT GSI扫描。获得能谱扫描数据后,利用能谱技术,每隔10 keV重建40~140 keV共11组单能量图像,于每组图像中分别选取伪影最重层面(A)和无或少伪影层面(B)的两幅图像行ROICT值和SD值测定,分别记录为CT1、CT2和SD1、SD2,计算伪影指数(AI)。采用配对t检验比较CT值,LSD-t检验比较AI值。 结果 40~140 keV 11组单能量图像中,120 keV单能量图像组,A、B两层面CT值分别为(41.41±9.48)HU和(41.91±7.97)HU(t=－0.21,P>0.05);其他10组两两比较差异均有统计学意义(P均<0.05)。70~140 keV时,两两比较,AI值差异均无统计学意义(P均>0.05);40~60 keV时,与其他能量组两两比较,AI值差异均有统计学意义(P均<0.05)。 结论 能谱CT利用能谱成像技术可有效减除金属植入物的伪影,120 keV为图像质量最佳的单能量成像点,70 keV为伪影减除的分界点。

The best monochromatic imaging for reducing spinal metal artifacts with gemstone spectral imaging

Objective To observe the application value of monochromatic imaging in reducing the metal artifacts of spine with gemstone spectral imaging (GSI), and to find the best monochromatic imaging of image quality. Methods Nineteen patients with metal implants of spine received GSI examination. The spectrum analysis was used to obtain the monochromatic images by special gemstone spectral imaging (GSI) viewer. Eleven groups of monochromatic images were obtained from 40 to 140 keV. For each patient, images with heaviest artifacts level (A) and no or less artifacts level (B)were selected in every group. CT value and SD value of ROI were measured and analyzed (named CT1, CT2 and SD1, SD2), and the artifact index (AI) was calculated. Paired t-test was applied to determine the CT value, and the AI value was compared using LSD-t test. Results In the monochromatic images at 120 keV, CT value of A and B levels were (HU) and (HU). There was no significant difference (t=-0.21, P>0.05). CT value of A and B levels in the other 10 groups were significantly different (all P<0.05). There was no significant difference among CT value of A and B levels in 70 to 140 keV (all P>0.05). For 40 to 60 keV, AI value were significantly different with that of the other groups (all P<0.05). Conclusion HDCT can effectively reduce artifacts of spine metal implants using spectral imaging acquisition technique. When 120 keV was the best point for quality of monochromatic imaging, 70 keV was the boundary for reducing metal artifacts.