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能谱CT单能量成像技术消除椎弓根钉固定术后金属伪影的研究

发布时间:2018-09-14 20:54  文章来源:笔耕文化传播
【摘要】:目的:研究能谱CT单能量成像(单keV)技术在去除脊柱金属植入物术后金属伪影方面的临床价值,并评价金属邻近区域的组织在去除伪影后的诊断可信度。 材料与方法:收集本院35例腰椎椎弓根钉内固定术后患者,行能谱CT能谱扫描(Gemstone Spectral Imaging, GSI),用GSI viewer重建出5mm140kVp图像,并以10keV的间隔重建40~140keV范围的11组单能量图像。客观评价:(1)选择椎弓根钉最完整层面图像,在金属邻近区域选择12个感兴趣区(region ofinterest,ROI)并选择1个背景ROI,测量每个ROI的CT值、噪声即SD值(StandardDeviation,SD),分别计算金属周围12个ROI的伪影指数(artifacts index,AI);(2)选择椎弓根钉层面和邻近无椎弓根钉的椎弓根层面图像,分别于椎管、腰大肌处选择ROI,测量其CT值、SD值。主观评价:2位具有中级职称的放射科医师对140kVp图像、40~140keV单能量图像行双盲法主观评分。评分方法:根据伪影对图像质量的影响程度予以记3、2、1、0分。3分为图像质量好,基本无伪影,金属钉及椎弓根皮质显示清晰,软组织对比良好;2分为图像质量较好,有部分伪影,金属钉及椎弓根皮质显示尚清晰,软组织基本显示清楚;1分为伪影较重,图像尚能观察,金属钉及椎弓根皮质显示欠清晰;0分为伪影很重,图像无法观察。统计学方法:所有统计学分析均使用SPSS19.0软件,以p0.05为差异具有统计学意义。对金属钉周围12个ROI的AI值取对数后进行单因素方差分析,并用LSD检验进行多重对比;对椎管、腰大肌CT值、SD值在椎弓根钉层面和无椎弓根钉的椎弓根层面图像之间分别进行配对样本t检验;对主观评分行单因素方差分析,并应用LSD检验进行多重对比。 结果: 1、客观评价:(1)随着keV增加,AI均值逐渐降低;双侧椎弓根旁90~140keV组间的AI值差异无统计学意义,,余感兴趣区100~140keV组间的AI值差异无统计学意义(p0.05)。与140kVp组比较,右侧椎弓根外、椎体前方、椎体、棘突后方70keV、80keV水平AI值差异无统计学意义(p0.05),余感兴趣区在70keV水平AI差异无统计学意义(p0.05),其余keV水平AI值差异均有统计学意义,其中40~60keV组的AI均值大于140kVp图像AI均值,90~140keV水平其AI均值小于140kVp图像的AI均值。(2)椎弓根钉层面和无椎弓根钉层面腰大肌、椎管CT值分别于100~120keV、120~140keV水平差异无统计学意义(p0.05);椎弓根钉层面和无椎弓根钉层面腰大肌SD值、椎管SD值在140kVp图像、40~140keV单能量图像上差异均有统计学意义(p0.05),随着keV增加差值的绝对值变小,其中100~140keV差值相近。 2、主观评价:随着keV增加,图像伪影减少,椎弓根钉及椎弓根皮质显示更清晰,但周围组织对比度降低,椎弓根钉直径变细。120~140keV水平图像主观评分差异无统计学意义(p0.05);80keV图像与140kVp图像评分差异无统计学意义(p=0.607),余keV水平单能量图像与140kVp图像主观评分差异均有统计学意义(p0.05)。 结论: 1、能谱CT单能量成像技术可有效降低腰椎椎弓根钉内固定术后的金属伪影,其中高能量水平(100~140keV)去除脊柱金属植入物伪影效果更佳。不同位置理想的重建单能量水平具有良好的一致性,100keV为理想重建能量水平。 2、120keV单能量图像椎弓根钉周围组织CT值比较真实,提示临床上测量CT值的理想图像应以该能量水平重建。单能量成像技术可在一定程度上校正伪影,但不能完全消除伪影。 3、降低伪影与图像质量是相互制约关系:即随着keV增高,伪影减少,但图像对比度降低;因此在重建图像选择能量水平时,应合理平衡图像质量与伪影的关系,而并非keV值越高越好。
[Abstract]:Objective: To evaluate the clinical value of single-energy computed tomography (single keV) in removing metal artifacts after spinal metal implantation and to evaluate the diagnostic reliability of adjacent tissues after removing the artifacts.
Materials and Methods: 35 cases of lumbar pedicle screw internal fixation in our hospital were collected. The images of 5 m 140 kVp were reconstructed by energy spectrum CT imaging (GSI) and 11 groups of single energy images were reconstructed by 10 keV interval from 40 keV to 140 keV. Twelve regions of interest (ROI) were selected in the adjacent region and one background ROI was selected to measure the CT value of each ROI, and the artifacts index (AI) of 12 ROIs around the metal was calculated. 2) The images of pedicle screw level and pedicle level of adjacent non-pedicle screw level were selected. Subjective evaluation: Two radiologists with intermediate professional titles scored 140 kVp images and 40-140 keV single-energy images by double-blind method. Scoring method: 3,2,1,0 points were scored according to the influence of artifacts on image quality. Pedicle cortex showed clearly, soft tissue contrast was good; 2 was divided into good image quality, some artifacts, metal nails and pedicle cortex showed clearly, soft tissue showed clearly; 1 was heavier artifacts, image still can be observed, metal nails and pedicle cortex showed less clearly; 0 was very heavy artifacts, image could not be observed. SPSS19.0 software was used for all statistical analysis, and P0.05 was used for statistical significance. The AI values of 12 ROIs around the screw were logarithmically analyzed by one-way ANOVA, and LSD was used for multiple comparisons. CT values of vertebral canal, psoas major muscle, and SD values were divided between pedicle screw level and pedicle level images without pedicle screw. Paired sample t test was used, subjective score was analyzed by one-way ANOVA, and LSD test was used for multiple comparisons.
Result:
1. Objective evaluation: (1) With the increase of keV, AI values gradually decreased; there was no significant difference in AI values between 90-140 keV groups near the bilateral pedicles, and no significant difference in AI values between 100-140 keV groups in the remaining regions of interest (p0.05). Compared with 140 kVp group, there was no significant difference in AI values of 70 keV and 80 keV levels outside the right pedicle, in the front of the vertebral body, in the vertebral body and behind the spinous process. There was no significant difference in AI at 70 keV level among the remaining regions of interest (p0.05). There were significant differences in AI values at other keV levels. The AI mean of 40-60 keV group was higher than that of 140 kVp group. The AI mean of 90-140 keV group was less than that of 140 kVp group. (2) The AI mean of psoas major muscle at pedicle screw level and non-pedicle screw level was higher than that of 140 kVp group. There was no significant difference in CT values between 100 and 120 keV, 120 and 140 keV (p0.05); SD values of psoas major muscle at pedicle screw level and non-pedicle screw level, SD values of spinal canal in 140 kVp images and 40 to 140 keV single energy images were statistically significant (p0.05). The absolute value of the difference decreased with the increase of keV, and the difference between 100 and 140 keV was similar.
2. Subjective evaluation: With the increase of keV, the artifacts decreased, the cortex of pedicle screw and pedicle screw showed clearer, but the contrast of surrounding tissues decreased, and the diameter of pedicle screw became thinner. There was no significant difference in subjective score between 120 and 140 keV images (p0.05); there was no significant difference in subjective score between 80 keV images and 140 kVp images (p = 0.607). There was a statistically significant difference in the subjective scores of flat single energy and 140kVp images (P0.05).
Conclusion:
1. Spectral CT single-energy imaging can effectively reduce the metal artifacts after lumbar pedicle screw fixation, and high-energy level (100-140 keV) is more effective in removing the metal implant artifacts.
2,120 keV single-energy image of the tissue around the pedicle screw is more realistic, suggesting that the ideal image for clinical measurement of CT value should be reconstructed at this energy level. Single-energy imaging technology can correct artifacts to a certain extent, but can not completely eliminate artifacts.
3. The relationship between artifacts and image quality is interdependent: artifacts decrease with the increase of keV, but image contrast decreases; therefore, the relationship between image quality and artifacts should be reasonably balanced in reconstructing image selective energy level, not the higher keV, the better.
【学位授予单位】:大连医科大学
【学位级别】:硕士
【学位授予年份】:2013
【分类号】:R816.8

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