ASIR技术结合自动管电流技术在降低下肢CTA辐射剂量中的应用

目的：探讨宝石CT应用自适应统计迭代重建技术（ASIR），并结合自动管电流技术，降低下肢动脉CTA辐射剂量的可行性。方法对行下肢CTA检查患者60例，随机分为A、B两组，各30例，A组使用固定管电流200mA扫描，滤过反投影（FBP）重建；B组使用自动管电流扫描，噪声指数（NI）设为12HU，ASIR重建，ASIR权重为40%。记录两组受检者CT剂量指数（CTDI）、剂量长度乘积（DLP），并由三位放射医师采用盲法对图像质量进行评分，并对两组患者的CTDI、DLP和图像质量评分进行2个独立样本的t检验。结果 A、B两组CTDI分别为（13.52±2.53）mSv和（4.18±1.10）mSv，DLP分别为（1954.39±128.41）mGy.cm和（613.25±39.93）mGy.cm，差异均有统计学意义（P〈0.01）。A、B两组图像质量评分分别为（3.65±0.75）分和（3.52±0.62）分，差异无统计学意义（P=0.39），均满足诊断要求。结论在宝石CT下肢动脉CTA检查中，应用ASIR技术，同时结合自动管电流技术，能够在保证图像质量的前提下有效降低对患者的辐射剂量。

Objective To evaluate the feasibility of Adaptive Statistical Iterative Reconstruction（ASIR）algorithm combined with automatic tube current modulation technique in reducing Lower extremity CTA radiation dosage. Methods 60 patients underwent lower extremity CTA scan on Gemstone CT were randomly divided into two groups（A and B,each containing 30 patients）. Patients of group A were scanned by fixed 200mA,and image was reconstructed by filtered back projection algorithm. In group B,patients were scanned by Automatic tube current modulation technique with noise index 12 HU,and image was reconstructed by ASIR algorithm with 40%weighting. CT dose index（CTDI）,dose length product（DLP）were recorded. The imaging quality was evalued by three radiologists blindly and independently. CTDI、DLP and image quality score of the two groups were compared with 2 independent samples t test. Results CTDI in group B[（4.18±1.10）mSv] was lower than group A [（13.52±2.53））mSv],and DLP in group B[（613.25±39.93） mGy·cm] was also lower than group A[（1954.39±128.41）mGy﹒cm]（both P〈0.01）. Image quality in both groups met the diagnostic requirements,there was no significant statistically difference of image quality（P=0.39）. Conclusion In lower extremity CTA examination with Gemstone CT,the radiation dose can be significantly decreased and image quality maintained by using ASIR algorithm combined with automatic tube current modulation technique .