目的：探讨双能CT迭代重建技术（SAFIRE）联合虚拟平扫（VNE）对评价胃壁图像质量及辐射剂量的影响。方法：50例患者行腹部双能CT扫描，用SAFIRE技术重建动脉期、门脉期图像，后处理得到SAFIRE动脉期、门脉期VNE图像（VNEaS、VNEpS），对真实平扫（TNE）、VNEaS、VNEpS三组图像行主观评价（图像质量评分）及客观评价[CT值、信噪比（SNR）、背景噪声、对比噪声比（CNR）]，记录辐射剂量[容积CT剂量指数（CTDIvol）、有效辐射剂量（ED）]。三组计量资料采用随机区组方差分析，计数资料用Friedman秩和检验，组间两两比较使用Wilcoxon秩和检验；两组计量资料采用配对t检验。结果：三组图像中胃壁、竖脊肌CT值及图像背景噪声差异无统计学意义；肝脏、腹主动脉CT值差异有统计学意义（F值分别为38.40、8.59，P＜0.05），VNEaS、VNEpS高于TNE。胃壁、肝脏、腹主动脉、竖脊肌SNR差异有统计学意义（F值分别为3.70、11.26、42.73、9.05，P＜0.05），TNE高于VNEaS、VNEpS。胃壁-竖脊肌CNR差异有统计学意义（F值为5.03，P＜0.05），TNE、VNEaS高于VNEpS。三组图像质量评分差异有统计学意义（χ2=20.65，P＜0.05），TNE高于VNEaS、VNEpS。TNE、VNE两组CTDIvol、ED差异均有统计学意义（t值分别为-8.03、-6.11，P＜0.05）。常规平扫加增强扫描、双能双期扫描ED分别为（23.79±6.00）、（17.51±4.72）mSv，差异有统计学意义（t值分别为-8.03、17.72，P＜0.05），双能双期扫描ED降低6.28mSv（26.39%）。结论：胃壁动脉期及门脉期SAFIRE技术联合虚拟平扫可替代真实平扫并能降低辐射剂量，且动脉期图像质量优于门脉期。
Abstract
Objective: To investigate the influence of iterative reconstruction(SAFIRE) combined with virtual non-enhanced(VNE) scan on image quality of gastric wall and radiation dose of dual-energy CT(DECT). Methods: 50 patients underwent abdominal DECT scan. The SAFIRE images in arterial phase and portal phase were reconstructed. The VNE images(VNEaS, VNEpS) in arterial phase and portal phase were obtained from SAFIRE image post-processing. Subjective evaluation(Image quality score), objective evaluation[CT value, signal to noise ratio (SNR), background noise, contrast noise ratio (CNR)] and radiation dose[volume CT dose index(CTDIvol), effective radiation dose(ED)] of true nonenhanced(TNE), VNEaS and VNEpS images were compared. Statistical analyses were performed using the random block analysis, the Friedman test, the Wilcoxon test and the paired t-test. Results: There were no significant differences in mean CT values and background noise of gastric wall and erector spinae among three groups of images(all P>0.05). The CT values of liver and abdominal aorta in VNEaS and VNEpS images were higher than that in TNE images(all P<0.05). The SNR of gastric wall, liver, abdominal aorta, and erector spinae in TNE images were higher than that in VNEaS and VNEpS images(all P<0.05). The CNR of gastric wall and erector spinae in TNE, VNEaS images were higher than that in VNEpS images(all P<0.05). However, the image quality of VNEaS images was lower than that of TNE images, and was higher than that of VNEpS images. The effective dose for triple-phase was (23.79±6.00)mSv, and that for dual-phase was(17.51±4.72)mSv. The dose saved by removing the TNE was 6.28 mSv (26.39%). Conclussion: The SAFIRE combined with VNE can provide comparable image quality to TNE images in gastric wall scanning, which could reduce patients’ radiation dose as well. The image quality of arterial phase is superior to that of the portal phase.
关键词
胃；体层摄影术 /
螺旋计算机；辐射剂量
Key words
Stomach /
Tomography, spiral computed /
Radiation dosage
{{custom_sec.title}}
{{custom_sec.title}}
{{custom_sec.content}}
参考文献
[1]Albert JM. Radiation risk from CT: implications for cancer screening[J]. AJR, 2013, 201(1): W81-W87.
[2]Brenner DJ, Elliston CD. Estimated radiation risks potentially associated with full-body CT screening[J]. Radiology, 2004, 232(3): 735-738.
[3]石磊，张欢，潘自来，等. 双能量CT在胃癌虚拟平扫应用的初步探讨[J]. 中国医学计算机成像杂志，2013，19（1）：33-37.
[4]杨亮，罗德红，赵燕风，等. 头颈部肿瘤检查中能谱CT虚拟平扫替代常规平扫的可行性研究[J]. 中华放射学杂志，2015，49（8）：572-576.
[5]Behrendt F, Schmidt BC, Keil S, et al. Image fusion in dual energy computed tomography: effect on contrast enhancement, signal-to-noise ratio and image quality in computed tomography angiography[J]. Investig Radiol, 2009, 44(10): 1-6.
[6]Nakayama Y, Awai K, Funama Y, et al. Lower tube voltage reduces contrast material and radiation doses on 16-MDCT aortography[J]. AJR, 2006, 187(5): W490-W497.
[7]Bongartz G, Golding SJ, Jurik AG, et al. European guidelines on quality criteria for computed tomography[M]. Luxembourg: European Commission, 2000.
[8]Sahni VA, Shinagare AB, Silverman SG. Virtual unenhanced CT images acquired from dual-energy CT urography: Accuracy of attenuation values and variation with contrast material phase[J]. Clin Radiol, 2013, 68(3): 264-271.
[9]Barrett T, Bowden DJ, Shaida N, et al. Virtual unenhanced second generation dual-source CT of the liver: Is it time to discard the conventional unenhanced phase?[J]. Eur J Radiol, 2012, 81(7): 1438-1445.
[10]Solomon J, Samei E. Quantum noise properties of CT images with anatomical textured backgrounds across reconstruction algorithms: FBP and SAFIRE[J]. Med Phys, 2014, 41(9): 919-928.
[11]侯阳，于兵，郭启勇，等. 迭代重建对前置门控冠状动脉CT图像质量及辐射剂量的影响[J]. 中华放射学杂志，2013，47（4）：305-309.
[12]王素雅，高剑波，刘杰，等. 迭代模型重建技术在肺动脉“双低”成像中的应用研究[J]. 实用放射学杂志， 2016，32（12）：1940-1944.
[13]付雨菲，何波，韩丹. 头颅CT平扫100kV结合SAFIRE技术的临床应用[J]. 临床放射学杂志，2014，33（1）：125-129.
[14]Schaafs LA, Lenk J, Hamm B, et al. Reducing the dose of CT of the paranasal sinuses: potential of an iterative reconstruction algorithm[J]. Dentomaxillofac Radiol, 2016, 45(7): 16-22.
[15]Li Y, Li Y, Jackson A, et al. Comparison of virtual unenhanced CT images of the abdomen under different iodine flow rates[J]. Abdom Imaging, 2017, 42(1): 312-321.
[16]Chai Y, Xing J, Gao J, et al. Feasibility of virtual nonenhanced images derived from single-source fast kVp-switching dual-energy CT in evaluating gastric tumors[J]. Eur J Radiol, 2016, 85(2): 366-372.
[17]Pinho DF, Kulkarni NM, Krishnaraj A, et al. Initial experience with single-source dual-energy CT abdominal angiography and comparison with single-energy CT angiography: image quality, enhancement, diagnosis and radiation dose[J]. Eur Radiol, 2013, 23(2): 351-359.
[18]Wang W, Liu L, Zeng H, et al. Utility of virtual unenhanced images and split-bolus injection using spectral multidetector CT for the assessment of renal cell carcinoma conspicuity and radiation dose[J]. Intern J Clin Prac, 2016, 70(9): B56-B63.
