key: cord-0861261-gk8b9kmd
authors: Jafari, Ramezan; Maghsoudi, Houshyar; Saburi, Amin
title: A unique feature of COVID-19 infection in Chest CT; “Pulmonary Target” appearance
date: 2020-11-21
journal: Acad Radiol
DOI: 10.1016/j.acra.2020.11.004
sha: 806e2b20991393ea1cb89bb31ddc4b98171987ce
doc_id: 861261
cord_uid: gk8b9kmd

nan

The novel Corona virus, COVID-19, which began in Wuhan, China in December 2019, briefly called COVID-19, has become a pandemic disease. Although pulmonary manifestations predominate, other organs may be involved. The diagnosis is suspected on the clinical & radiologic findings and confirmed with RT-PCR tests. Findings of covid-19 on chest CT are bilateral peripheral multifocal ground-glass opacities (GGO) and patchy consolidations, linear opacities, reversed halo, and Crazy-paving. (1) Although these findings are highly suggestive for COVID-19 in clinically suspected cases, they are not specific and as some of the other viral pneumonias like influenza, SARS and MERS may show similar imaging features.(2) Some unusual findings such as parallel pleura sign, paving stone sign (3) & double rings of Saturn(4) and chest target sign (5) have also been reported in CT scans of these patients.

We present a unique imaging feature of pulmonary involvement in four RT-PCR proven COVID-19 cases. A circular appearance of non-involved pulmonary parenchyma with a central hyperdense dot surrounded by ground glass or alveolar opacities was found in each of them. Chest CT of 4 following cases showed bilateral multifocal patchy consolidative opacities, which were non-specific common suggestive findings for covid-19 infection. The RT-PCT test proved COVID-19 in all cases. (Figure 1 , 2) Interestingly, it revealed some circular appearances of noninvolved pulmonary parenchyma with a central hyperdense dot, which is surrounded by alveolar opacities and caused "Pulmonary target appearance". This is a unique and specific appearance that has not been previously reported in other diseases. Firstly, Jafari et al reported similar this feature named "Ring of Saturn" at July 2020 and then Muller et al at Aug 2020 also reported alike pattern as chest target sign.(4, 5) "Pulmonary target appearance" seems to be unique & specific for COVID-19 pneumonia. The pulmonary target appearance, is important from two perspectives: First, this sign has not been reported in other lung diseases as far as we know, and it maybe specific to this disease. Secondly, this appearance is consistent with the pathological findings and possible mechanisms proposed for patients with organizing pneumonia (OP) and localized involvement of small vessels.(6) It has previously been suggested that viral involvement of a pulmonary lobule can be mediated by the central bronchiole and adjacent vessels through lymphatic and venous drainage.(7) Moreover, this feature seems to be a variant of the "halo sign" of OP. We believe this "pulmonary target sign" is a specific finding which can distinguish covid-19 pneumonia from other similar viral pneumonias. 

Coronavirus Disease (COVID-19): Spectrum of CT Findings and Temporal Progression of the Disease

Severe acute respiratory syndrome: temporal lung changes at thin-section CT in 30 patients

Interpretation of CT signs of 2019 novel coronavirus (COVID-19) pneumonia

Rings of Saturn" appearance: a unique finding in a case of COVID-19 pneumonitis

Chest CT target sign in a couple with COVID-19 pneumonia

Imaging Features of Coronavirus disease 2019 (COVID-19): Evaluation on Thin-Section CT

CT distribution and sign features