关键词: 管电流, 特征参数模型, 肺结节, 定量分析

Abstract: Objective The quantitative significance of differential diagnosis of pulmonary nodules under different CT scanning conditions was analyzed by establishing characteristic parameter curve model. Methods CT plain chest scan images of patients with pulmonary nodules treated in our hospital from September 2018 to October 2019 were analyzed retrospectively. The inclusion criteria were nodule diameter ≥3 mm and no other medical history. Of the 96 selected samples, 68 met the criteria (39 males and 29 females).According to the different scanning dose, the subjects were divided into low dose observation group (tube voltage 120 kV, tube current 20 mA) and conventional dose group (tube voltage 120 kV, tube current 150 mA).There were 34 cases in each group, and the correlation between different tube current and effective radiation dose and image quality were observed by measuring and calculating the relevant parameters of scanning length, effective dose, sample shape and signal-to-noise ratio. PACS artificial intelligence software and artificial synthesis were used to extract the characteristic information (diameter, volume, density texture, edge details, internal structure) of pulmonary nodules and record the data. Furthermore, the mass of pulmonary nodules was calculated by formula, the differences of parameters under different tube currents were compared by U test, the volume and mass of important parameters determined by unit logic were incorporated into multivariate logic analysis. The curve model of characteristic parameters was established, the area under the curve was measured and ROC was sketched. Chi-square analysis was used to evaluate the difference of characteristic parameter curve model for quantitative diagnosis of pulmonary nodules under different tube currents, and to compare the image quality under different tube currents at the same time. Results In the study, it is found that the effective radiation dose received by the sample increases linearly with the increase of tube current under the condition of constant tube voltage. The CT images of obese patients (BMI≥23.9) showed obvious noise when using low dose scan, which affected the inter-tissue observation. However, in the CT images of the samples with BMI standard (18.5 ≤ BMI ≤ 23.9), there was no obvious trend threshold between the signal-to-noise ratio and tube current of pulmonary nodules, and the difference was not statistically significant (P<0.05).The characteristic parameter curve model showed that the volume and mass homogeneity curve of pulmonary nodules showed the change trend was correlated with the change of tube current, and the stability and consistency were good, so the two elements were the main analytical components of the model. The ROC curve of the observation group showed that the area under the curve was 0.826, which was higher than that of the conventional group, the area under the curve of the ROC curve was 0.747. Conclusion Compared with conventional dose, the establishment of characteristic parameter curve model under low dose CT scan mode is more quantifiable for differential diagnosis of pulmonary nodules.

Key words: Tube current, Characteristic parameter model, Pulmonary nodule, Quantitative analysis