| Background:The outbreak of COVID-19 has caused widespread concern among people around the world.The epidemic has officially named COVID-19 by WHO.COVID-19 mainly causes lesions in both lungs,and most patients often seek medical treatment in the early stage because of respiratory discomfort.Therefore,Chest CT scan has become one of the necessary auxiliary examination methods for COVID-19.Chest CT scan is not only indispensable for the screening and diagnosis of COVID-19,but also can classify the clinical types of confirmed patients,understand the development stage of the disease and evaluate the clinical treatment effect,which has important guiding significance for the clinical treatment direction.However,the disadvantage of CT is that the dose of ionizing radiation of conventional scanning is high,which may cause certain damage to the patients.The concept of "as low as reasonably achievable radiation dose"（ALARA）was developed and widely accepted as early as 2001.Subsequently,the research on low-dose computed tomography is becoming more and more mature.However,the reduction of radiation dose in the scanning process will inevitably lead to the decline of image quality.Therefore,the reduction of radiation dose under the premise that the image quality can meet the requirements of clinical diagnosis has become the focus and focus of research.At present,low-dose CT scanning technology is widely used in the screening and diagnosis of chest diseases,we can consider its application in the screening,diagnosis,review and treatment of COVID-19 patients,so as to reduce the harm of radiation dose to COVID-19 patients as much as possible without affecting the diagnosis of the disease.Objective:To explore the feasibility of low-dose scanning for COVID-19 patients by using the method of high-pitch combined with ASIR,and compare the radiation dose and image quality.Methods:Clinical data of patients who were diagnosed with COVID-19 in our hospital were collected,divided into group A（41 cases）and group B（50 cases）according to presence or absence of the imaging manifestations of COVID-19.Meanwhile,50 cases of undiagnosed COVID-19 patients who were screened for COVID-19 in our hospital during the same period were selected as the control group.Low-dose group A and B have been reconstructed by ASIR and used high-pitch to scan,the value of pitch is1.75,while conventional dose group has been reconstructed by FBP and used common pitch to scan,the value of pitch is 1.375.The radiation dose of each group have been recorded,the subjective and objective evaluation of image quality in the three groups have been finished,and difference of the image quality and radiation dose of each group have been compared.Results:There was no statistical difference between low dose A group and B group（CTDIvol:H=0.896,P=0.370;DLP:H=-0.138,P=0.890;ED:H=-0.164,P=0.870）,there was statistical differences between low dose A group and conventional dose group（CTDIvol:H=6.640,P<0.01;DLP:H=7.670,P<0.01;ED:H=7.698,P<0.01）,there was statistical differences between low dose B group and conventional dose group（CTDIvol:H=7.938,P<0.01;DLP:H=7.935,P<0.01;ED:H=7.937,P<0.01）,and the radiation dose of the low-dose A group and B group was all significantly lower than that of the conventional dose group（the ED was all reduced by about 51%）.There was no statistical difference in the image quality scores of three groups（H=0.728,P>0.05）;There was no statistical difference in the objective evaluation of the three groups images.（CNR:F=2.207,P>0.05;SNR:F=1.284,P>0.05）.Conclusion:Low dose scanning with large pitch combined with ASIR for COVID-19 patients can evidently reduce the radiation dose without any significant decrease in image quality. |
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