Imaging, in particular chest X-ray and computed tomography (CT), is important in the detection of lung lesions, assessment of lesion size, density, and evolution. Chest X-ray examination is convenient and fast, and has been proven effective in diagnosing other coronaviruses, such as severe acute respiratory syndrome(SARS) and Middle East respiratory syndrome (MERS).
The radiology department should prepare the requirements of COVID-19 imaging examination workflows, including but not limited to:
set up a special waiting area and examination room for COVID-19 patients
require all radiologist, technologists and nurses to master skills of prevention of COVID-19 infection
formulate emergency CT examination specifications, procedures and disinfection measures for patients with suspected COVID-19
require self-protection measures for all radiologists, technologists and nurses
regulate disposal of waste protective equipment
It should emphasized that in order to prevent cross-infection, hospitals should clearly divide the polluted area, semi-polluted area, and clean area according to the requirements of nosocomial infection control, and set up independent inspection area.
Infection prevention and control is a new task and serious challenge facing the radiology department in China. All members must fully understand the epidemic situation and fully grasp the knowledge of infection control. The work process and working mode must be changed in accordance with the requirements.
Preparedness for the radiology department in the prevention and control of COVID-19
In western countries, CT is not considered a screening examination for COVID-19. Due to various factors such as specimen collection technology, kit quality, and the diversity of disease evolution, the false-negative rate of nucleic acid detection is relatively high in China. In the situation of suspected crowds and limited medical resources, nucleic acid test negative but CT positive (highly suggestive of viral pneunomia) are also listed as medical isolation treatment criteria in China, which is more in line with the actual situation in Wuhan.
Some critically patients may have elevation of troponin level, and an increase of C-reactive protein can be seen. Critically ill patients may develop acute respiratory distress syndrome, septic shock with metabolic acidosis and coagulation dysfunction that are difficult to correct. For the clinical criteria, the first step is to ascertain the epidemiology history of suspected cases. Confirmed cases must be tested positive by RT-CPR assay or by NGS. SARS-CoV-2 nucleic acids can be detected in nasopharingeal swabs, sputum, or other lower respiratory tract secretions, blood, and stools.
The incubation period is 1-4 days, mostly 3-7 days, based on the current epidemiological evidence. Fatigue, and dry cough are the most common clinical onset symptoms. Nasal congestion, sore throat, and diarrhea are atypical clinical presentations. Patients with mild or moderate type only demonstrate a low fever and mild fatigue without pneumonia in the early stage of disease. Most patients have a good prognosis, with few patients becoming critically ill. Prognosis is poor for the elderly and those with chronic underlying diseases, and the symptoms of children tend to be relatively mild.
Focal hemorrhage and necrosis of the lung tissue may occur with hemorragic infarction. Intra-alveolar fibrosis, resulting from organization of inflammatory exudates also can be found. The epithelium of the bronchial mucosa in lungs discards, and there is formation of mucus and mucus plugs in the cavity. The coronavirus particles can be seen in the bronchial mucosal epithelium and type 2 alveolar epithelial cells under an electrone microscope.
In post-mortem, the lungs show consolidation in different degrees. Serum, fibrinous exudate, and transparent membrane formation are seen in the alveolar cavity; exudation cells are mainly monocytes and macrophages, and multinucleated giant cells are easily seen. Type 2 alveolar epithelial cells are proliferated significantly, and some of the cells shed. Inclusion bodies can be seen in type 2 alveolar epithelial cells and macrophages. Alveolar septal vascular congestion and edema, monocyte and lymphocyte infiltration, and intravascular thrombosis can be seen.
A series of cases of pneunomia of unknown cause was reported in Wuhan, in late December 2019. Epidemiological data demonstrated person-to-person spread is the main mode of transmission, which resulted in a worldwide outbreak. World Health Organization (WHO) designated COVID-19 as the official name. The pathogen was confirmed to be severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a betacoronavirus. Standard technique to confirm COVID-19 is nucleic acid testing with reverse transcription polymerase chain reaction (RT-PCR) and/or next-gen sequencing (NGS) methods. Imaging features differ in different individuals and stages of the COVID-19 penumonia, and they are also different from other infectious pulmonary diseases.