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目的 :比较原始数据迭代重建算法(sinogram affirmed iterative reconstruction algorithm,SAFIRE)与传统滤波反投影(filtered back projection,FBP)重建算法在胃癌术前CT分期中的图像质量。方法:选取40例经手术病理证实为进展期胃癌的患者,所有患者术前均行128层双源炫速CT扫描并分期。将原始数据通过SAFIRE的1~5级及FBP算法分别进行重建,获得5 mm层厚的CT图像。测量并比较所得图像的胃壁病灶、肝脏、右侧竖脊肌、皮下脂肪及腹主动脉的噪声和CT值、病灶的对比噪声比(contrast-to-noise ratio,CNR)和信噪比(signal-to-noise ratio,SNR)及腹主动脉SNR,并对胃癌术前分期的图像质量进行主观评分。结果:FBP重建算法与SAFIRE(1~5级)间各部位所测得的平均CT值差异无统计学意义(P>0.05)。FBP重建图像中病灶的平均噪声最高,而在SAFIRE图像中,随着1~5等级的增高,噪声逐渐降低,CNR及SNR也随之降低。主观评分中,FBP重建图像的评分最高,而SAFIRE图像随等级的升高,评分逐渐降低;其中,FBP重建算法与SAFIRE S1、SAFIRE S2与S3的主观评分结果间差异均无统计学意义(P>0.05)。结论:SAFIRE技术应用于胃癌术前分期检查中,虽能降低图像噪声,提高图像的CNR、SNR,但相比常规FBP重建算法并不能提高进展期胃癌术前分期的准确率。在相同扫描条件下,更推荐应用FBP重建算法或SAFIRE的S1图像来对进展期胃癌进行分期诊断。
Objective: To compare the image quality of SAFIRE and filtered back projection (FBP) reconstruction in the preoperative CT staging of gastric cancer. Methods: Forty patients with advanced gastric cancer confirmed by surgery and pathology were selected. All patients underwent preoperative double-source CT scan with 128-slice double-source and staged. The original data were reconstructed by SAFIRE 1 ~ 5 and FBP respectively to obtain CT images with a thickness of 5 mm. The noise and CT values of gastric wall, liver, right ependyma, subcutaneous fat and abdominal aorta were measured and compared. The contrast-to-noise ratio (CNR) and signal-to-noise -to-noise ratio (SNR) and abdominal aorta SNR, and subjectively evaluate the image quality of preoperative staging of gastric cancer. Results: There was no significant difference in average CT values between FBP reconstruction and SAFIRE (grades 1-5) (P> 0.05). The mean noises of lesions in FBP reconstructed images were the highest, while in SAFIRE images, the noise decreased gradually and the CNR and SNR decreased with the increase of 1 ~ 5 levels. Among the subjective scores, the FBP reconstructed images had the highest scores, while the SAFIRE images gradually decreased with the grades increasing. There was no significant difference between the FBP reconstruction algorithm and subjective scores of SAFIRE S1, SAFIRE S2 and S3 (P > 0.05). Conclusion: The SAFIRE technique applied to preoperative staging of gastric cancer can reduce the image noise and improve the CNR and SNR of the image, but it can not improve the accuracy of preoperative staging of advanced gastric cancer compared with conventional FBP reconstruction. In the same scanning conditions, it is more recommended to use FBP reconstruction algorithm or SAFIRE S1 images to advanced gastric cancer staging diagnosis.