Abstract: Objective:Morphological features of solitary pulmonary nodules is an important basis to judge the malignant and benign,high resolution CT imaging is a key factor to improve the detection rate of SPN subtle morphological characteristics.The objective of this study is to comparatively analyze the difference of pulmonary nodules diameter less than 2 cm imaging features between high resolution thin slice CT(512×512 matrix,HRCT) and ultra- high resolution thin slice CT(1 024×1 024 matrix,ultra-HRCT),and to analyze the advantages and disadvantages of ultra-HRCT in showing the fine structure of SPN and the image quality.Method:72 SPN in living body were scanned by ultra-HRCT and HRCT.The occurrence rate of various features of SPN was calculated,the features of SPN include:edge:lobulated sign(deep,shallow),halo sign(clear,fuzzy),burr sign(thin and short burr,thin and long burr,spine sign),internal structure(bubble sign/air bronchogram/cavity),nodules density(calcification,ground glass density).Meanwhile the image quality of ultra-HRCT and HRCT was observed,and their statistical difference was analyzed.Results:The occurrence rate of various features of SPN prompts that ultra-HRCT is better than HRCT,but P>0.05,which showed no significant statistically difference.The image quality of ultra-HRCT is better than that of HRCT,but P>0.05,which showed no significant statistically difference.Conclusions:The occurrence rate of various features of SPN on ultra-HRCT is less than that on HRCT,ultra-HRCT on the lobulated sign,burr sign,halo sign,bubble sign,air bronchogram,the detection rate of GGO is higher than that of HRCT,suggesting that ultra-HRCT in displaying the lobulated sign,burr sign,halo sign,bubble sign,air bronchogram,GGO and other fine is better than HRCT in terms of structure,but the two has no significant statistical difference.Subjective image quality score of HRCT was higher than Ultra-HRCT,ultra-HRCT image display quality is better than that of the edge of the lesion and vascular structure of HRCT,but the motion artifacts and noise occurrence rate is higher,the difference was not statistically significant.X-ray radiation dose of the two are in a safe range.