INTRODUCTION
According to the latest guidelines for diagnosis and treatment of COVID-19(Novel coronavirus pneumonia) by the General Office of the National Health Commission of China, the use of fluorescent RT-PCR(reverse transcriptase polymerase chain reaction) to detect nucleic acids of the coronavirus is the gold standard for molecular diagnosis of COVID-19(1,2), but nucleic acid detection has several limitations, including the need for high specificity of primer sets, low sensitivity, and the length of testing period. In comparison, CT(Computed tomography) imaging offers a simple, fast, and highly sensitive means to elucidate the extent and nature of lung tissue in COVID-19. After analyzing the CT images of confirmed COVID-19, we noticed that the signs of secondary pulmonary lobular structures were commonly associated with all stages of COVID-19. Recognizing the underlying secondary pulmonary lobular structural image signs can enable us to understand the typical or atypical CT characteristics of COVID-19, so as to provide reliable imaging diagnosis and differential diagnosis for clinical early diagnosis and prognosis judgment(3).