Revolution CT低剂量联合ASIR-V在胸部扫描相关性研究

Correlation study of low-dose and ASIR-V Revolution chest CT

目的探讨在胸部低剂量CT扫描下联合不同权重ASIR-V提高图像质量的可行性。方法本研究收集进行Revolution胸部CT平扫的患者60例,随机分为A、B两组,每组30例。固定管电压120 kV,用自动管电流调整辐射剂量。A组为噪声指数(NI)=10,用滤波反投影法(FBP)重组图像;B组为噪声指数NI=18,进行(0%～100%)后置ASIR-V重组,重组间隔为10%;重组层厚均为0.625 mm。测量胸廓入口、气管隆突下、上腹部肝门层面背部肌肉、皮下脂肪、肝脏及脾脏相同部位ROI的CT值、噪声(SD),计算信噪比(SNR),并对两组图像进行客观评价,采用单因素方差来分析比较噪声(SD)、信噪比(SNR)。主观评分由2名工作经验5年以上放射科主治医师用双盲法进行主观评分,采用符号等级检验来比较。结果随着后置ASIR-V迭代强度的增加,图像噪声逐渐降低,SNR升高(P<0.05)。B组噪声指数(NI)=18时,后置ASIR-V70%时图像客观指标优于常规剂量A组(6.47±2.21)mSv,且辐射剂量(2.73±1.01)mSv降低了57.80%。两名医师的主观评分一致性良好,图像质量随着迭代强度的加大在主观噪声及图像细节的显示方面最佳,优于后置ASIR-V80%-100%,且后置ASIR-V70%优于常规剂量FBP(P<0.05)。结论 Revolution CT在NI为18时,使用后置ASIR-V70%重组图像质量可以达到NI为10时的图像质量要求,并降低了57.80%的辐射剂量。

Objective To investigate the image quality of chest CT using low-dose combined with different weights of adaptive statistical iterative reconstruction (ASIR-V). Methods 60 patients undergoing Revolution chest CT were randomly divided into A and B groups. At fixed tube voltage 120kV, the radiation dose was adjusted with the automatic tube current. In group A (30 patients), the noise index (NI) was 10, and the image was reconstructed by filtered back projection (FBP). In group B (30), NI was18, and posterior-ASIR-V reconstruction was performed (0%-100%) with 10% reconstruction interval and 0.625 mm layer thickness. The CT values and noise (SD) of regions of interest at the thoracic inlet, submandibular trachea, hepatic hilar plane of the abdomen, subcutaneous fat, liver, and spleen were measured. The signal to noise ratio (SNR) was calculated and single-factor variance was used to compare SD and SNR in the 2 groups. Image quality was scored by 2 radiologists with more than 5 years of experience and the scores were compared using a symbolic grade test. Results With increasing posterior-ASIR-V iterative intensity, the SD gradually decreased and the SNR increased (P<0.05). The image quality of posterior ASIR-V 70% was better in group B than the conventional dose A group (P<0.05), and the radiation dose was reduced by 57.80% from 6.47±2.21 mSv in group A to 2.73±1.01 mSv in group B. The image quality scores of the 2 observers were in good agreement with higher scores as the iterative intensity increased. Image quality was better with post-ASIR-V70% than post-ASIR-V80%-100% and conventional dose FBP (P<0.05). Conclusion The radiation dose is reduced by 57.80% with NI of 18 and post-ASIR-V70% reconstruction method while maintaining image quality.