能谱CT结合MARs技术对不同材质义齿伪影去除的临床价值

Clinical value of energy spectrum CT combined with MARs technique for artifact removal of dentures of different materials

目的研究能谱CT单能量成像及单能量+多伪影去除系统(MARs)去除义齿周围伪影的临床价值,并比较不同材质义齿对影像质量的影响。方法纳入100例有义齿植入的患者,义齿种类包括镍铬合金(30例)、烤瓷(30例)、胶托+不锈钢托(40例)。在相同CT扫描参数条件下进行能谱成像技术(GSI)扫描,获得混合能量(QC)影像、70~140 keV的单能量影像及单能量+MARs影像。在每例患者义齿伪影最严重层面和邻近无伪影的软组织区域划定2个感兴趣区(ROI):ROI1选取在同层无伪影的头夹肌处;ROI2选取在口腔中部舌部软组织明暗相间伪影区,ROI面积150~200 mm^(2),分别测量噪声(SD)、CT平均值,并计算伪影指数(AI),以SD和AI作为客观评价参数。由2名高年资放射科医师对各组影像质量进行主观评分。结果镍铬合金、烤瓷、胶托+不锈钢托3种材质义齿邻近组织的SD、AI随着管电压的增加而降低,在90 keV及以上时明显低于QC影像;单能量+MARs影像的SD和AI均明显低于同参数单能量影像;随着管电压的增加,口腔软组织的对比度明显降低,在110 keV+MARs时对比度最佳,主观评分最高。镍铬合金、烤瓷、胶托+不锈钢托3种材质义齿最佳成像参数比较,烤瓷的SD和AI最小。结论能谱扫描联合MARs技术能有效减少镍铬合金、烤瓷、胶托+不锈钢托的金属伪影,可作为去除口腔修复体伪影的有效方法。

Objective To investigate the clinical value of energy spectrum CT single energy imaging and single energy+multi artifact reduction system(MARs)in removing artifacts around denture,and compare effects of different denture materials on image quality.Methods One hundred patients with denture implantation were scanned,including 30 cases of nichcr alloy,30 cases of porcelain and 40 cases of glue bracket+stainless steel bracket.Under the same CT scanning parameters,energy spectrum imaging(GSI)was used to obtain mixed energy images(QC),single energy images of 70-140 keV and single energy+MARs images.At the level of the most serious denture artifact in each patient,two areas of interest(ROI)were defined:ROI1 selected at the head muscle without artifact in the same level and ROI2 selected the light-dark artifact area of soft tissue of tongue in the middle of the mouth with ROI of about 150-200 mm^(2).The average noise(SD)and CT were measured respectively,and the artifact index(AI)was calculated.SD and AI were used as objective evaluation parameters.The image quality of mixed energy image,single energy image and single energy+MARs image were subjectively scored by two senior attending radiologists.Results The noise and artifact index of adjacent tissues of three materials,namely,nickel-chromium alloy,porcelain,glue holder+stainless steel holder,decreased with the increase of tube voltage,and it was significantly lower than QC above 90 keV,which was significantly lower than that of QC mixed energy image.The SD and AI of single energy+MARs images were significantly lower than those of single energy images with same parameters.The contrast of oral soft tissue decreased significantly with the increase of tube voltage.The contrast of oral soft tissue was the best at 110 keV+MARs,and the subjective score was the highest.Comparing the best imaging parameters of three kinds of dentures,namely,nichcr alloy,porcelain plate,glue plate+stainless steel plate,SD and AI of porcelain base were the smallest.Conclusion Energy spectrum scanning combined with MARs technology can effectively reduce metal artifacts of nichcr alloy,adhesive bracket+stainless steel bracket and porcelain,and can be used as an effective method to remove artifacts of dental prosthesis.