256CT低管电压联合迭代重组技术在头颈部CT血管成像中的应用

Application of Low-Tube-Voltage Technique with Iterative Reconstruction Algorithm in Performing CT Angiography of Craniocervical Arteries

目的探讨低管电压(80 k V)联合迭代重组技术在头颈部CT血管成像(CTA)扫描中对图像质量、辐射剂量的影响。方法将75例临床需要行头颈部CTA检查的患者随机编入A、B、C三组,每组25例。A组为常规剂量扫描,参数为120 k V、300 m As,经滤波反投影(FBP)重组;B、C组为低剂量扫描,管电流和管电压分别为120k V、180 m As,80 k V、180 m As,采用i Dose4迭代重组。对比分析CT图像质量,包括动脉强化值、对比噪声比(CNR)、图像质量评分及辐射剂量。计量资料采用配对t检验两两比较,图像质量评分采用非参数χ2检验进行统计分析。结果 (1)图像质量主观评分:A组3分1例,4分24例;B组3分2例,4分23例;C组3分5例,4分20例;统计学分析无差异(P﹥0.05)。(2)A、B两组主动脉弓、颈总动脉、颈内动脉及大脑中动脉的动脉强化CT值统计无明显差异(P﹥0.05);C组的CT动脉强化值高于A组(P<0.05)。(3)C组的背景噪声[(12.5±1.9)HU]高于A组[(9.0±1.6)HU](P<0.05);两组的CNR分别为(49.2±9.4)、(43.0±12.6),无统计学差异(P﹥0.05)。(4)A、B、C组的剂量长度乘积(DLP)分别为(925.1±48.5)、(571.4±24.2)、(164.1±7.0)m Gy·cm;辐射有效剂量(ED)分别为(2.87±0.15)、(1.77±0.08)、(0.51±0.02)m Sv,均有统计学意义(P<0.05),C组较A组辐射剂量明显降低,约82.3%。结论 256 CT头颈部CTA采用低管电压(80 k V)联合迭代重组技术能提供满足临床诊断要求的图像,同时明显降低辐射剂量。

Objective To discuss the effect of low-tube-voltage technique （80 kV） with iterative reconstruction algo- rithm on the image quality and radiation dosage in performing CT angiography of craniocervical arteries. Methods A total of 75 patients, who were scheduled to receive CT angiography of craniocervical arteries, were randomly and equally divided into three groups with 25 patients in each group. Group A： 120 kV, 300 mAs and filtered back projection reconstruction were used; group B： 120 kV, 180 mAs and iterative reconstruction algorithm were employed; and group C： 80 kV, 180 mAs and iterative reconstruction algorithm were adopted. CT image quality, including enhanced CT value of eranioeervica[ arteries, contrast-to-noise ratio （CNR）, image quality score and radiation dosage （DLP and ED） were calculated and the results were compared among three groups. Using paired t-test the measurement data were two-two compared, and the image quality scores were statistically analyzed with nonparametric X2 test. Results （1） The overall image quality scores were as follows ： group A ： 3 points in one patient and 4 points in 24 patients ; group B ： 3 points in 2 patients and 4 points in 23 patients; and group C： 3 points in 5 patients and 4 points in 20 patients. No statistically significant difference in image quality scores existed between each other among the three groups （ P 〉 0.05 ）. （2） No statistically significant difference in CT values of craniocervical arteries, including aortic arch, common carotid artery, internal carotid artery and middle cere- bral artery, existed between group A and group B （ P 〉 0.05 ）, although CT value of eraniocervieal artery in group C was significantly higher than that in group A （ P 〈 0.05 ）. （3） The image background noise of C group was （ 12.5 ± 1.9） HU,which was significantly higher than that of group A （9.0 ± 1.6 HU, P 〈 0.05 ）. The difference in CNR between group C and group A was not significant （49.2 ± 9.4 vs 43.0 ± 12.6, P 〉 0.05 ）. （4） The DLP and ED of group A, B and C were （925.1±48.5） mGy. cm, （2.87±0.1） mSv, （571.4.1±24.2.5） mGy. cm, and （1.77±0.08） mSv, （164.1 ± 7.0） mGy cm, （0.51 ±0.02） mSv respectively. The differences between each other among the three groups were statistically significant （P 〈 0.05）. Compared with group A, the radiation dosage of group C was reduced by 82.3%. Conclusion CT angiography of craniocervical arteries using 256-slice CT low-tube-voltage technique （80 kV） with iterative reconstruction algorithm can obtain satisfactory image quality that can meet the diagnostic requirements, while the radiation dose can be significantly reduced.