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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 investigate the effect of low voltage (80 kV) combined with iterative reconstruction technique on image quality and radiation dose in CT angiography (CTA) of head and neck. Methods Seventy-five patients with clinical need of head-and-neck CTA were randomly assigned to A, B and C groups, 25 in each. Group A was a conventional dose scanning with the parameters of 120 kV and 300 mAs, and was filtered and backprojected (FBP). Group B and C were low-dose scanning. The tube current and tube voltage were 120k V, 180 mAs, 80 k V, 180 m As, using i Dose4 iterative recombination. CT images were compared and analyzed, including arterial enhancement, contrast-to-noise ratio (CNR), image quality score, and radiation dose. Measurement data using paired t-test comparison, the image quality score using non-parametric χ2 test for statistical analysis. Results (1) Subjective score of image quality: 3 cases in group A and 4 cases in 24 cases; group B in 3 cases and 2 cases in 4 cases and 23 cases in group C, 3 cases in 5 cases and 4 cases in 20 cases; there was no statistical difference (P> 0.05). (2) There was no significant difference in arterial CT value between aorta, common carotid artery, internal carotid artery and middle cerebral artery in group A and group B (P> 0.05); CT arteries in group C were higher than those in group A (P < 0.05). (3) The background noise of group C was (12.5 ± 1.9) HU higher than that of group A (9.0 ± 1.6) HU] (P <0.05). The CNR of group C were (49.2 ± 9.4), (43.0 ± 12.6) ), No statistical difference (P> 0.05). (4) The DLP of group A, B and C were (925.1 ± 48.5), (571.4 ± 24.2) and (164.1 ± 7.0) m Gy · cm respectively. The effective radiation dose (ED) ± 0.15), (1.77 ± 0.08) and (0.51 ± 0.02) m Sv, respectively (all P <0.05). The radiation dose of group C was significantly lower than that of group A (about 82.3%). Conclusion The low-voltage (80 kV) combined with iterative recombination technique in CTA of 256 CT head and neck can provide images meeting clinical diagnostic requirements and significantly reduce the radiation dose.