Pulmonary CT signs in patients with COVID-19 infection

Background: The aim of the study is to investigate the pulmonary CT signs in patients with conrmed COVID-19 infection. This study included 100 patients, 54 male and 46 female their ages ranged from 6 to 85 years. All Patients tested positive for COVID-19 infection by RT-PCR test included in this study. All the patients performed pulmonary CT scan and the CT ndings were evaluated. Results: 90 patients (90%) had abnormal pulmonary CT. Two lungs affected in 79 patients (79%). Lesions involved 1 lobe (11%), 2-3 lobes (35%) and 4-5 lobes (44%). The most involved pulmonary lobes were right lower lobe (77 patients, 77%), followed by left lower lobe (71 patients, 71%), the most involved pulmonary segments were posterior segments (69 patients, 69%),peripheral sub-pleural lesions were the commonest lesions location (64 patients, 64%). The most common lesions pattern were ground glass pattern (44 patients, 44%), followed by mixed ground glass and consolidation patterns (33 patients, 33%). The commonest lesion shape was patchy opacities (40 patients, 40%). Reversed halo sign (28 patients, 28%), air bronchogram sign (39 patients, 39%), crazy paving pattern (77 patients, 77%), vascular thickening (66 patients, 66%), and pleural thickening (7 patients, 7%) CONCLUSION: The main pulmonary CT signs in patients with COVID-19 infection are bilateral, peripheral, multi-lobar patchy and nodular Ground glass opacication with or without consolidation. Other signs may also present include crazy paving pattern, reversed halo sign vascular thickening, and air bronchogram sign with no extra-pulmonary signs except for few pleural thickening.


Introduction
Coronavirus disease or (COVID -19) is highly infectious disease transmitted by droplets infection. It also known as severe acute respiratory syndrome coronavirus 2 or (SARS-CoV-2) [1]. COVID-19 epidemic started in Wuhan, Hubei, China at the end of December 2019 [2]. COVID-19 incubation period ranges from one to fourteen days, most symptoms appear in the period between three to seven days after infection [3]. The severity of COVID-19 symptoms is greatly varying, from totally asymptomatic to severe acute symptoms that may lead to death [1,2]. According to symptoms patients with Covid-19 infection classi ed into ve stages; (stage I) asymptomatic infection, (stage II) acute upper respiratory tract infection, (stage III) mild pneumonia, (stage IV) severe pneumonia, and (stage V) critical cases [3]. Early diagnosis of COVID-19 provides an important method for early isolation, prevention, and treatment of the disease [1]. Diagnosis of COVID-19 depends mainly on the nucleic acid testing by using real time PCR test that has high speci city, and low sensitivity for COVID-19 diagnosis [4]. CT chest together with clinical manifestation and laboratory investigations are important diagnostic modalities used for diagnosis of COVID-19 [5]. Many researchers concluded that pulmonary CT has high sensitivity reaching up to 97%-98% in diagnosis of COVID-19 pneumonia [6]. It is noted that about 25% of patients show normal pulmonary CT in a very early stage of COVID-19 infection [7]. Pulmonary CT imaging signs detected in patients of COVID-19 infection were reported as single or multi-lobar, unilateral or bilateral, peripheral or diffuse patchy, pulmonary ground glass opacities with or without consolidation opacities [5].
The aim of the study is to investigate the pulmonary CT signs in patients with con rmed COVID-19

CT Analysis
Two radiologists with more than 10 years' experience in chest imaging reported all CT images independently and all CT features were assessed.
The assessed pulmonary CT features were as follow: unilateral or bilateral pulmonary affection, the number of pulmonary lobes affected (one lobe, two or three lobes, four or ve lobes affection), site of pulmonary lobe affected, site of pulmonary segment affected, the distribution of lesions in the lungs (peripheral, central, or mixed distribution), the shape of the pulmonary lesions either patchy or nodular shape, the appearance of pulmonary lesions (ground glass opacity, consolidation, or both ground glass opacity and consolidation patterns), any other associated pulmonary features like crazy paving pattern, pulmonary vascular thickening, air bronchogram sign, reversed halo sign, and signs of brosis), also extra-pulmonary manifestations like mediastinal or hilar lymphadenopathy, pleural effusion or thickening were assessed.

Discussion
By the end of May 2020 the pandemic of COVID-19 infected more than 6 million persons and killed more than 300.000 persons all over the world according to World Health Organizations (WHO) reports [8].
Early diagnosis of COVID-19 pneumonia is important to decrease the spread of COVID-19 pandemic.
Early diagnosis helps in early isolation and treatment of the patients and so decreases the spread, morbidity and mortality of the disease. RT-PCR test has low sensitivity and high false negative results in diagnosis of COVID-19. Many recent studies showed that the use of high-resolution pulmonary CT helped in early detection of pulmonary lesions in COVID-19 infection [1,9].
This study included 100 patients tested positive for COVID-19 by RT-PCR.
Our study showed that COVID-19 pneumonia affected male (54%) more than female (46%), we also reported that adult are more affected with COVID-19 pneumonia than children with mean age of infection was about 45 years.
According to CT results in our study 10% of patients showed normal pulmonary CT and 90% showed abnormal pulmonary CT ndings this is matched with Bernheim, et.al. 2020 they concluded that 9% of positive COVID-19 patients showed normal pulmonary CT in the early and asymptomatic stage of the disease [10].
In our study most of abnormal pulmonary CT showed bilateral pulmonary affection 79% of the patients and only 11% showed unilateral pulmonary affection. In our study numbers of patients with multiple pulmonary lobar affection were dramatically higher (79%) than the numbers of patients with single lobar affection (11%) this matched with Han et.al. 2020 they concluded that 65% of patients showed more than one pulmonary lobe affection [1].
In our study we reported that the lower pulmonary lobes were more affected by COVID-19 pneumonia than the upper pulmonary lobes, the right lower lobe affected in 77% of patients and left lower lobe affected in 71% of patients this was in agreement with Bernheim, et.al. 2020 who concluded that the lower lobes were more affected than upper lobes [10]. This may be due to the thicker and shorter anatomy of the right lower bronchus that accelerates its invasion by the virus [1].
In our study we reported that the posterior pulmonary segments were much more affected (69%) by COVID-19 pneumonia lesions than anterior pulmonary segments (44%). This was in agreement with Yang pattern of COVID-19 pneumonia in pulmonary CT scan was presence of ground glass opacities with or without consolidation opacities [1,10,12]. This was in match with our study we concluded that the most common pattern of COVID-19 pneumonia in pulmonary CT scan was ground glass pattern (44%) followed by mixed pattern of both ground glass and consolidation opacities (33%) and the least pulmonary CT pattern was consolidation opacity alone (13%).
Huang et.al. 2020 reported that the pathophysiologic mechanism of coronavirus infections may be the same as SARS-CoV and MERS-CoV infections that cause diffuse alveolar damage due to in ammatory cytokine storm and this explained the ground glass opacities in early pulmonary CT [13].
In our study we reported that the most common shape of COVID-19 pneumonia opacities were ill de ned patchy opacities (76%) either alone or mixed with nodular pattern and this matched with Han et.al. 2020 that concluded that 86% of the lesions showed patchy shape [1].
In our study we reported many characteristic pulmonary CT signs for COVID -19 pneumonia as reversed halo sign (28%) , air bronchogram sign (39%), crazy paving pattern (77%), and vascular thickening (66%) and all these signs were reported in many researches [1,10,12]. not detected in pulmonary CT scan of early COVID-19 pneumonia and they explained that as these ndings may appear in the later and severe stage of the disease [1,10,12]. This was matched with our study as we didn't detect signs of pulmonary brosis or extra-pulmonary manifestations in our study for few pleural thickening (7%).
In our study we concluded that the main pulmonary CT signs in COVID-19 infection are bilateral, peripheral, sub-pleural multi-lobar ground glass opaci cation with or without consolidation in patchy distribution with or without nodular pattern more on posterior and basal pulmonary segments. Other pulmonary signs may also present include crazy paving pattern, reversed halo sign vascular thickening, and air bronchogram sign with no extra-pulmonary signs except for few pleural thickening and these were in agreement with Many researchers [1,10,12].
In our study we had a limitation as there was no follow-up CT to evaluate the treatment effect and the prognosis of the disease as all positive RT-PCR patients were transferred to quarantine hospitals and isolation centers.

Conclusion
The main pulmonary CT signs in patients with COVID-19 infection are bilateral, peripheral, sub-pleural, multi-lobar Ground glass opaci cation with or without consolidation in patchy distribution with or without nodular pattern more frequent in posterior and basal lung segments. Other pulmonary signs may also present include crazy paving pattern, reversed halo sign vascular thickening, and air bronchogram sign with no extra-pulmonary signs except for few pleural thickening.

Declarations
This study involved human subjects.
The author con rmed that all appropriate ethical guidelines for the use of human subjects have been followed, any necessary IRB and/or ethics committee review has been obtained, and information about the IRB/ethics committee is included in the manuscript.
The author has con rmed that all necessary patient/participant consent or assent has been obtained and the appropriate institutional forms have been archived. If the IRB/ethics committee waived the requirement for patient/participant consent or assent, an explanation for the waiver is included in the text.
The author has con rmed that a statement listing potential con icts of interest or lack thereof is included in the text.