J Korean Soc Radiol. 2021 Nov;82(6):1505-1523. English.
Published online Nov 04, 2021.
Copyrights © 2021 The Korean Society of Radiology
Original Article
COVID-19 진단을 위한 CT 검사: 프로토콜, 방사선량에 대한 체계적 문헌고찰 및 진단을 위한 CT 검사량
이종혁,1 홍현숙,2 김형진,1 이창현,1 구진모,1 윤순호1,3
CT Examinations for COVID-19: A Systematic Review of Protocols, Radiation Dose, and Numbers Needed to Diagnose and Predict
Jong Hyuk Lee, MD,1 Hyunsook Hong, PhD,2 Hyungjin Kim, MD,1 Chang Hyun Lee, MD,1 Jin Mo Goo, MD,1 and Soon Ho Yoon, MD1,3
    • 1서울대학교 의과대학 서울대학교병원 영상의학과
    • 2서울대학교병원 의학연구협력센터
    • 3Department of Radiology, UMass Memorial Medical Center
    • 1Department of Radiology, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.
    • 2Medical Research Collaborating Center, Seoul National University Hospital, Seoul, Korea.
    • 3Department of Radiology, UMass Memorial Medical Center, Worcester, MA, USA.
Received May 21, 2021; Revised July 25, 2021; Accepted July 28, 2021.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (https://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

초록

Purpose

Although chest CT has been discussed as a first-line test for coronavirus disease 2019 (COVID-19), little research has explored the implications of CT exposure in the population. To review chest CT protocols and radiation doses in COVID-19 publications and explore the number needed to diagnose (NND) and the number needed to predict (NNP) if CT is used as a first-line test.

Materials and Methods

We searched nine highly cited radiology journals to identify studies discussing the CT-based diagnosis of COVID-19 pneumonia. Study-level information on the CT protocol and radiation dose was collected, and the doses were compared with each national diagnostic reference level (DRL). The NND and NNP, which depends on the test positive rate (TPR), were calculated, given a CT sensitivity of 94% (95% confidence interval [CI]: 91%–96%) and specificity of 37% (95% CI: 26%–50%), and applied to the early outbreak in Wuhan, New York, and Italy.

Results

From 86 studies, the CT protocol and radiation dose were reported in 81 (94.2%) and 17 studies (19.8%), respectively. Low-dose chest CT was used more than twice as often as standard-dose chest CT (39.5% vs.18.6%), while the remaining studies (44.2%) did not provide relevant information. The radiation doses were lower than the national DRLs in 15 of the 17 studies (88.2%) that reported doses. The NND was 3.2 scans (95% CI: 2.2–6.0). The NNPs at TPRs of 50%, 25%, 10%, and 5% were 2.2, 3.6, 8.0, 15.5 scans, respectively. In Wuhan, 35418 (TPR, 58%; 95% CI: 27710–56755) to 44840 (TPR, 38%; 95% CI: 35161–68164) individuals were estimated to have undergone CT examinations to diagnose 17365 patients. During the early surge in New York and Italy, daily NNDs changed up to 5.4 and 10.9 times, respectively, within 10 weeks.

Conclusion

Low-dose CT protocols were described in less than half of COVID-19 publications, and radiation doses were frequently lacking. The number of populations involved in a first-line diagnostic CT test could vary dynamically according to daily TPR; therefore, caution is required in future planning.

초록

목적

Coronavirus disease 2019 (이하 COVID-19) 폐렴에서 CT를 일차 진단 검사로 사용하고자 하는 논의가 있지만, 대규모 인구에게 CT 검사를 적용했을 때의 상황을 고찰한 연구는 없었다. 본 연구에서는 COVID-19 폐렴을 다룬 연구들에서 CT 프로토콜과 방사선량을 분석하고, CT 검사가 일차 진단 검사법으로 사용될 때 필요한 CT 검사량에 대해 알아보고자 한다.

대상과 방법

본 연구는 9개의 인용도가 높은 영상의학과 저널에서 COVID-19 폐렴의 CT 기반 진단을 다룬 문헌들을 검색하였다. 먼저, 연구에서 제시된 CT 프로토콜, 방사선량을 조사하여, 이를 해당 국가의 diagnostic reference level과 비교하였다. 추가로, COVID-19에 대한 CT 민감도 94%, 특이도 37%를 적용하여, 우한시와 뉴욕, 이탈리아의 초기 COVID-19 outbreak에서 polymerase chain reaction (이하 PCR) 검사 양성률에 기반한 number needed to diagnose (이하 NND)와 number needed to predict (이하 NNP)를 계산하였다.

결과

총 86개의 연구가 검색되었고, 그중 CT 프로토콜은 81개의 연구에서(94.2%), 방사선량은 17개의 연구에서(19.8%) 보고되었다. 저선량 흉부 CT는 표준선량 흉부 CT보다 2배 많은 연구에서 활용되었다(39.5% vs. 18.6%). 방사선량을 보고한 17개의 연구들 중, 15개의 연구에서 방사선량은 해당 국가의 diagnostic reference level 수치보다 낮았다(88.2%). COVID-19에 대한 CT 민감도 94%, 특이도 37%를 적용하였을 때, NND는 3.2회 CT scans으로 나타났다. 한편, PCR 검사 양성률 50%, 25%, 10%, 5%에서의 한 명의 COVID-19 환자를 진단 위한 CT 검사량을 나타내는 NNP는 각각 2.2, 3.6, 8.0, 15.5회의 CT scans로 나타났다. 우한시에서는 최종 17365명의 COVID-19 환자를 진단하기 위하여 약 35418명에서(PCR 검사 양성률 58%) 44840명(PCR 검사 양성률 38%)의 사람들이 CT 검사를 받은 것으로 나타났다. 뉴욕시와 이탈리아의 초기 COVID-19 유행 10주간, PCR 검사 양성률에 따라 일 CT 검사량이 최대 5.4, 10.9배까지 변화하였다.

결론

CT를 COVID-19에 대한 일차적인 진단검사로 사용할 경우, PCR 검사 양성률에 따라 CT 검사량은 변동량이 크고, 이는 추후 판데믹 상황에서 고려되어야 할 것이다.

Keywords
Coronavirus; Tomography, X-Ray Computed; Radiation Dosage; Mass Screening; Clinical Protocols

INTRODUCTION

The coronavirus disease 2019 (COVID-19) pandemic has spread rapidly and swept the world, resulting in at least 165 million confirmed cases and 3.4 million global deaths as of May 21, 2021 (1). For the diagnosis of COVID-19, reverse transcription-polymerase chain reaction (RT-PCR) is the standard test (2, 3). Several guidelines, including those of the World Health Organization, the Center for Disease Control and Prevention, the American College of Radiology, and the Fleischner Society, do not recommend the use of CT examinations as a first-line test for COVID-19 because of potential false-negativity and overlapping CT features with other types of pulmonary diseases (4, 5, 6, 7). However, RT-PCR may also yield false-negative results, and there may be limited access or availability of RT-PCR testing in resource-constrained environments, especially during the early stages of an outbreak (8, 9).

CT examinations have been discussed as a first-line test because of their high sensitivity for COVID-19 (8, 9, 10, 11, 12). Indeed, CT scans were performed in 88.7% of confirmed COVID-19 patients in the early outbreak in China and were temporarily introduced as the first diagnostic tool in Hubei (10). In addition, a screening strategy with both CT and RT-PCR was also suggested to maximize early diagnosis because early detection, isolation, and quarantine of patients with COVID-19 are required to block its transmission and reduce mortality (12, 13, 14, 15, 16, 17, 18). Prior discussions have mainly focused on the diagnostic accuracy of CT, but the impact of CT exposure on large populations has remained under-discussed. One of the major concerns is that the first-line diagnostic use of chest CT scans for COVID-19 would be accompanied by mass population exposure to ionizing radiation. Medical imaging involves a relatively small amount of radiation, but even this minimal degree of radiation may be harmful, especially for pediatric patients given their longer life expectancy and high susceptibility to radiation (19, 20, 21, 22). This study aimed to review the chest CT protocols and radiation doses described in COVID-19 publications and to explore the number needed to diagnose (NND) and the number needed to predict (NNP) if CT scans are used as first-line tests.

MATERIALS AND METHODS

This systematic review article was performed and reported in compliance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. This study was conducted with COVID-19 publications, therefore was deemed exempt by the Seoul National University Hospital Institutional Review Board, and informed consent was not necessary.

SEARCH STRATEGY

We searched COVID-19 publications between January 2020 and January 2021 from the following top seven highly cited radiology journals according to the impact factor of Journal Citation Reports 2020: Radiology; Investigative Radiology; Journal of the American College of Radiology; European Radiology; Korean Journal of Radiology; American Journal of Roentgenology; and European Journal of Radiology. We also added Radiology: Cardiothoracic Imaging and Pediatric Radiology to the literature search. The search was conducted on January 10, 2021, with the following search terms: (CT OR computed tomography) AND (coronavirus OR COVID-19 OR 2019-nCoV OR SARS-COV-2) on the journal websites.

ELIGIBILITY CRITERIA FOR STUDY SELECTION

We reviewed all the searched publications regardless of the study type. The inclusion criteria were as follows: studies 1) including patients confirmed or suspected of COVID-19, and 2) discussing the CT features of COVID-19 pneumonia. We applied the following exclusion criteria: studies dealing with 1) CT features of COVID-19 other than pneumonia (e.g., pulmonary thromboembolism) or 2) state-of-the-art radiologic techniques (e.g., studies with artificial intelligence, radiomics-based studies).

We included prospective or retrospective cohort studies and case-control studies, but not case reports, case series, letters, editorial comments, abstracts, review articles, guidelines, or consensus statements. As an exception, case reports and series in pediatric patients were included given these patients’ susceptibility to radiation. The full-text articles were assessed for eligibility independently by two authors (J.H.L. and S.H.Y. with 8 and 15 years of experience in thoracic radiology, respectively). Any discrepancy was resolved by consensus.

DATA EXTRACTION

The following items were extracted from the eligible articles using a standardized spreadsheet in Microsoft Excel 2016 (Microsoft Corp., Redmond, WA, USA): study characteristics (publication year, authors, title, abstract, number of patients with CT scans), study population characteristics (age, nationality, whether pediatric patients were included, CT indications, studies with only baseline or both baseline and follow-up CT, and number of CT scans per patient), CT examination information (multichannel CT machine, tube voltage, tube current, reconstructed slice thickness, pitch, and use of contrast media), and radiation dose information (low-dose or standard-dose chest CT, volume CT dose index [CTDIvol], dose-length product [DLP], and effective dose).

DATA SYNTHESIS AND STATISTICAL ANALYSIS

The study-level CT protocol and radiation dose from individual studies were collected and numerically described, and the doses were compared with each national diagnostic reference level (DRL).

CT scans satisfying at least one of the following criteria were designated as low-dose chest CT: 1) a low-dose protocol was clearly mentioned in the manuscript, 2) a tube voltage ≤ 100 kVp was applied, or 3) a tube current lower than 150 mAs with a tube voltage of 120 kVp was used (23, 24). In contrast, chest CT protocols meeting the following criteria were regarded as standard-dose chest CT: 1) a standard dose protocol was clearly mentioned in the manuscript, or 2) the above conditions of the low-dose chest CT were not met.

To explore the magnitude of mass population CT exposure in the COVID-19 pandemic, the NND and NNP were calculated depending on test positive rate (TPR) using the following equation (25):

NND = 1/(sensitivity + specificity − 1)

NNP = 1/(positive predictive value + negative predictive value − 1) = 1/{(sensitivity × TPR)/(sensitivity × TPR + [1 − specificity] × [1 − TPR]) + (specificity × [1 − TPR])/(specificity × [1 − TPR] + [1 − sensitivity] × TPR) − 1}

The TPR was defined as the proportion of confirmed patients among those tested using RT-PCR. We utilized the CT sensitivity of 94% (95% confidence interval [CI]: 91%–96%) and the specificity of 37% (95% CI: 26%–50%) from a meta-analysis (26). The calculated NNPs were plotted according to TPRs of 0%–100%, and we specified NNPs at TPRs of 50%, 25%, 10%, and 5%, respectively.

We applied the equation of NNP to estimate the number of total CT examinations during the early outbreak in Wuhan, Hubei Province, China, where chest CT scans were temporarily used as the first-line diagnostic tool with clinic-epidemiological information according to the fifth edition of the Chinese National Health Commission published on February 4, 2020 (27). The number of confirmed patients based on RT-PCR tests and clinically diagnosed patients based on CT scans was obtained from the published article’s supplemental material (28). These materials specified the number of those in the age groups of under 20, 20–39, 40–59, and 60 or older until March 8, 2020. We referred to the RT-PCR positivity rate of 38% in Wuhan from the literature (29). NNP was analyzed in the following two scenarios: test positivity using RT-PCR only, 38%; test positivity using RT-PCR or clinical diagnosis, 58% (38% + 20%; the latter rate was calculated from the supplemental material) (28). Since clinically diagnosed cases were defined as patients with pneumonia showing the typical imaging findings of COVID-19, preferentially CT scans, in the guidelines (27, 30, 31), we assumed that all of these patients had CT scans (28). In addition, we analyzed the change of NNPs according to daily TPRs in the early COVID-19 outbreak in New York State (from March 8 to May 17, 2020) and Italy (from March 2 to May 11, 2020) (32, 33), because of their resource-constrained environments and high community disease burden (7).

The NNDs and NNPs were calculated and the extent of mass population CT exposure was estimated using R version 4.0.0 (R Foundation for Statistical Computing, Vienna, Austria).

RESULTS

LITERATURE SEARCH

From the initial literature search identifying 476 publications, 86 studies were finally included in the qualitative analysis (Fig. 1) (11, 12, 13, 14, 15, 16, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113).

Fig. 1
Flow diagram of the literature search.

BASELINE STUDY CHARACTERISTICS

The baseline information of the 86 studies included in this study is presented in Table 1. The median number of patients was 85.5 (range, 4–4824) with an age range of 3 hours to 101 years. In 11 studies (12.8%; 11 of 86), a total of 332 pediatric patients were included (median number, 8; range, 2–201) (13, 41, 47, 64, 68, 85, 90, 91, 92, 96, 100). Of the 11 studies, six studies included only pediatric patients (41, 85, 90, 91, 92, 96).

Table 1
Baseline Information, Reported CT Protocols, and Radiation Doses of the 86 Studies on COVID-19

The studies were most commonly reported from China (66.3%; 57 of 86), and other countries included Italy (7.0%; 6 of 86), France (4.7%; 4 of 86), Iran (3.5%; 3 of 86), the United States (2.3%; 2 of 86), Germany (2.3%; 2 of 86), Belgium (2.3%; 2 of 86), Republic of Korea (1.2%; 1 of 86), Switzerland (1.2%; 1 of 86), Japan (1.2%; 1 of 86), India (1.2%; 1 of 86). Six studies included two or more countries (7.0%; 6 of 86).

Chest CT scans were performed routinely for COVID-19 patients confirmed with RT-PCR (69.8%; 60 of 86). In 20 studies, CT was performed to screen patients with clinically suspected COVID-19 (23.3%; 20 of 86), and six studies (7.0%; 6 of 86) had specific indications for chest CT imaging (evaluation for comorbidities or complications associated with COVID-19, n = 5; chest radiographs that provided negative or uncertain findings, n = 1).

The baseline CT results were preferentially analyzed in the included studies (65.1%; 56 of 86), and both baseline and follow-up CT results were included in the remainder (34.9%; 30 of 86). Regarding the number of CT scans, 14858 patients, 267 patients, and 447 patients had one, two, and three or more CT examinations, respectively.

REPORTED CT PROTOCOLS AND RADIATION DOSES

Eighty-one studies described the specific CT protocols used in their studies (94.2%; 81 of 86) (Table 1). For these 81 studies, a multichannel ≥ 16-channel CT machine (91.4%; 74 of 81), tube voltage of 120 kVp or higher (65.4%; 53 of 81), automatic tube current modulation (43.2%; 35 of 81), and pitch > 1 (14.8%; 12 of 81) were preferentially used. Images were frequently reconstructed and reviewed with a slice-thickness of 3 mm or thinner (82.7%; 67 of 81). In the majority of studies, CT examinations were performed without intravenous contrast media (58%; 47 of 81). Although eight studies reported CT examinations with intravenous contrast media (9.9%; 8 of 81), information on how many CT phases were obtained could not be identified.

Of 86 studies, low-dose and standard-dose chest CT examinations were performed in 34 studies (39.5%; 34 of 86) and 16 studies (18.6%; 16 of 86), respectively. Both low-dose and standard-dose CT scans were used in two studies. However, the type of CT examinations could not be determined in 38 studies (44.2%; 38 of 86).

Only 17 studies (19.8%; 17 of 86) reported radiation doses in terms of CTDIvol (n = 11), DLP (n = 10), or effective dose (n = 6) (15, 40, 46, 50, 52, 58, 70, 75, 94, 97, 98, 100, 102, 105, 106, 109, 110). None of the studies contained size-specific dose estimates. The corresponding information is tabulated in Table 2. In 15 of these 17 studies, the mean radiation dose was lower than the national DRL (88.2%; 15 of 17). One study reported a similar radiation dose to the national DRL (5.9%; 1 of 17) (50), and the remaining study reported a radiation dose larger than their DRL (5.9%; 1 of 17) (94). Of the 11 studies handling pediatric patients, the radiation dose was reported in only one study, with an effective dose of 0.8 to 1.2 mSv (100).

Table 2
Reported Radiation Doses in 17 Studies on COVID-19

NND, NNP, AND THE ESTIMATED AMOUNT OF CT EXPOSURE

Plots of NND and NNP depending on TPR is shown in Fig. 2. Since the sensitivity and specificity of CT examinations for COVID-19 are fixed as 94% and 37%, respectively, the NND was 3.2 scans as a fixed value. When 95% CIs of CT sensitivity and specificity for COVID-19 were taken into account, the NND was demonstrated to change from 2.2 to 6.0. On the other hand, the NNPs at TPRs of 50%, 25%, 10%, and 5% were 2.2 (95% CI: 1.7–3.4), 3.6 (95% CI: 1.7–5.3), 8.0 (95% CI: 6.0–12.0), 15.5 (95% CI: 11.4–23.3) scans, respectively.

Fig. 2
Plots demonstrate (A) the NND according to the CT sensitivity and specificity, and (B) the NNP according to the CT sensitivity, specificity, and test positive rate of RT-PCR. Dotted lines represent 95% confidence intervals.
COVID-19 = coronavirus disease 2019, NND = number needed to diagnose, NNP = number needed to predict, RT-PCR = reverse transcription-polymerase chain reaction

In the early outbreak in Wuhan, 35418 (TPR, 58%; 95% CI: 27710–56755) to 44840 (TPR, 38%; 95% CI: 35161–68164) individuals were estimated to have undergone CT examinations to clinically diagnose 17365 patients. By age distribution, 702 (95% CI: 549–1124) to 888 (95% CI: 697–1350) individuals under 20 years of age, 7547 (95% CI: 5904–12093) to 9554 (95% CI: 7492–14524) individuals in their 20–30s, 14112 (95% CI: 11041–22614) to 17866 (95% CI: 14010–27160) individuals in their 40–50s, and 13058 (95% CI: 10216–20924) to 16531 (95% CI: 12963–25130) individuals in their 60s or older were estimated to have CT scans at TPRs of 58% and 38%, respectively (Table 3).

Table 3
Number of CT Scans Needed to Clinically Diagnose COVID-19 according to the Age Distribution in Wuhan, China

NNP changes according to daily TPR in New York State and Italy are shown in Fig. 3, and weekly NNPs are specified in Table 4. TPRs in New York State and Italy peaked to be 44.6% and 25.8% after 4 and 3 weeks since the initial surge, with corresponding NNPs of 2.3 and 3.5 scans, respectively. The lowest TPR in those areas were 5.4% and 2%, resulting in NNPs of 14.4 and 38.1, respectively. Therefore, daily NNPs changed up to 5.4 and 10.9 times within 10 weeks, respectively.

Fig. 3
NNP according to the daily TPR of COVID-19 in (A) New York State from March 8 to May 17, 2020, and (B) Italy from March 2 to May 11, 2020. The left and right Y-axes represent daily TPR and NNP, respectively. The dark-blue line with triangular symbols represents changes in the daily TPR, and the solid line with circular symbols represents changes in the NNP. The daily TPR of COVID-19 in New York State and Italy were accessed from the webpage of “New York Forward”(32) and “Our World in Data”(33).
COVID-19 = coronavirus disease 2019, NNP = number needed to predict, TPR = test positive rate

Table 4
Estimates of the NNP for COVID-19 according to the Daily TPR of COVID-19 in New York State and Italy

DISCUSSION

To date, relevant guidelines have rarely contained information about the specific protocols and radiation dose of chest CT for COVID-19, although low-dose nonenhanced CT is preferably recommended (114). Indeed, a recent study reported that chest CT indications, protocols, and radiation doses for COVID-19 widely varied across different countries and healthcare sites by surveying a limited number of cases (9, 115). Concordant with this, our study also revealed similar results for COVID-19 publications. Considering the stochastic effect of ionizing radiation (19, 20, 22, 116) and the as low as reasonably achievable (ALARA) principle (117), CT examinations should be used judiciously with surveillance of protocols and radiation doses, as well as compliance with the DRL (19, 116, 118).

In this study, most COVID-19 publications in radiology journals included CT protocols, but low-dose nonenhanced CT protocols were identified in fewer than half of articles, whereas over 90% of studies used 16-channel or higher CT machines capable of performing low-dose lung cancer CT screening (119). Information on the radiation dose was frequently lacking, although the CT doses were mostly lower than corresponding DRLs when reported. A low-dose nonenhanced chest CT protocol is mostly sufficient to assess community-acquired pneumonia (120, 121), although a standard-dose CT scan with contrast medium can evaluate pulmonary embolism or necrosis within a parenchymal lesion. If chest CT is considered as the first-line diagnostic tool in the future pandemic, low-dose CT scanning and managing the radiation dose must be further addressed in relevant radiology research.

We estimated the number of people undergoing CT examinations in Wuhan, but deliberately avoided estimating the effective dose or the impact on cancer risk. The estimated number of CT examinations during 2 months (Jan-Mar 8th, 2020) approaches the number of enrolled patients in the National Lung Screening Trial over 2 years (122). This number itself can be an alarming message regarding the first-line diagnostic usage of CT scans, underscoring the need for details about managing and monitoring CT radiation exposure under the ALARA principle (117). Estimating the effective dose and cancer risk in large populations involves several assumptions, is prone to deviations in the analysis, and is affected by substantial variability in doses across sites and countries. Nevertheless, a linear-no-threshold model between radiation dose and malignancy seems applicable to the population under 20 years of age (21, 22, 116). Even in adults in their 20s or older, concerns exist about the association of thyroid, breast cancer, or hematologic malignancies with medical CT exposures (19, 123). Another point to consider is the usage of follow-up CT scans during the course of COVID-19 (42, 52, 64, 69, 80, 84, 98, 99). Indeed, 35% of studies in our study performed both baseline and follow-up CT, further increasing the radiation dose. This mass radiation dose issue should be addressed when CT is considered as a first-line diagnostic tool in the future pandemic.

The difference in NNP depending upon TPR also has implications for the use of CT scans in the future pandemic. The timely diagnosis of respiratory infections will be problematic in the earliest stages of any future pandemic as a molecular diagnostic tool requires nucleic acid sequencing of a new pathogen and may be affected by shortage or quality issues, as in Wuhan (13, 124). In the early COVID-19 outbreak in New York State and Italy, TPR rapidly rose in the earliest stage of the pandemic, as shown by the lower NNPs (Fig. 3). This is followed by a peak and then decreased TPR, accompanied by an increase in the NNP (32, 33). Thus, the early period of an outbreak is the best time window for the first-line diagnostic usage of CT scans if chest CT scans render a specific finding for a new pathogen. Subsequently, such usage of CT scans should be stopped considering the rapid increase in the NNP when TPR decreases and molecular diagnostics are widely available. Besides, efforts for increasing pretest probability before CT scanning should be considered together by triaging suspects of new infection to increase TPR (125).

This study has several limitations. First, we searched relevant publications from specific radiology journals, not using databases such as the Embase and OVID-MEDLINE, giving rise to potential selection bias. Nevertheless, these journals are regarded as having high-quality academic reporting, and the searched publications may represent high-quality studies in radiology. Second, although the purpose of this study was to investigate CT protocols and radiation doses in COVID-19 publications, data extraction was performed solely based on descriptions in individual studies, without contacting the authors to obtain any missing or unreported data. Third, although TPR is not an equal term with disease prevalence in the strict sense, we used TPR as a proxy measure of disease prevalence. Fourth, the diagnostic accuracy of CT scans for COVID-19 for the assumption was obtained from a meta-analysis at the early pandemic (26). The accuracy of CT scans, particularly for specificity, can be improved as radiologists get experienced in interpreting infectious diseases (97). Nevertheless, considering that a molecular diagnostic tool for emerging infectious diseases is usually limited and the diagnostic use of CT can be pursued in the early pandemic as COVID-19, CT accuracy from the early pandemic result would be appropriate in the analysis. Finally, TPR, CT sensitivity and specificity for COVID-19, and the numbers of COVID-19 patients for estimating the number of CT examinations in Wuhan were derived from different studies. In addition, some of the clinically diagnosed patients in Wuhan may have been diagnosed with COVID-19 based on chest radiographs, although the imaging findings of COVID-19 are nonspecific on radiographs.

In conclusion, low-dose CT protocols for COVID-19 could be identified in fewer than half of the publications, and information on the radiation dose was frequently lacking. The first-line diagnostic use of CT scans for COVID-19 would involve a substantial amount of CT exposure for large populations, particularly at a low test positive rate. The first-line diagnostic use of chest CT in the future of the COVID-19 pandemic—and, conceivably, for future pandemics—must be discussed based on not only the diagnostic accuracy of chest CT but also ALARA principle and NNP.

Notes

Author Contributions:

  • Conceptualization, L.J.H., Y.S.H.

  • data curation, L.J.H., Y.S.H.

  • formal analysis, L.J.H., H.H., Y.S.H.

  • investigation, L.J.H., H.H., Y.S.H.

  • methodology, L.J.H., Y.S.H.

  • project administration, L.J.H., Y.S.H.

  • resources, L.J.H., Y.S.H.

  • software, L.J.H., H.H.

  • supervision, Y.S.H.

  • validation, L.J.H., H.H., Y.S.H.

  • visualization, L.J.H., H.H.

  • writing—original draft, L.J.H., Y.S.H.

  • writing—review & editing, all authors.

Conflicts of Interest:Dr. Soon Ho Yoon works in MEDICALIP Co. Ltd. as a chief medical officer outside this work. Dr. Hyungjin Kim received a research grant from Lunit Co. and holds stock in MEDICALIP Co. outside this work. Dr. Jin Mo Goo received grants from Infinitt Healthcare, Dongkook Lifescience, and LG Eletronics, outside this study. Other authors have no conflicts of interest to declare for this article.

Funding:None

Acknowledgments

The authors would like to acknowledge Andrew Dombrowski, PhD (Compecs, Inc.) for his assistance in improving the use of English in this manuscript.

References

    1. Johns Hopkins University & Medicine. COVID-19 dashboard by the center for system science and engineering. 2020 Jan 01; [Accessed May 21, 2021].
    1. U.S. Food and Drug Administration. Emergency use authorization (EUA) summary COVID-19 RT-PCR test (laboratory coporation of America). 2020 Dec 09; [Accessed Mar 5, 2021].
    1. Corman VM, Landt O, Kaiser M, Molenkamp R, Meijer A, Chu DK, et al. Detection of 2019 novel coronavirus (2019-nCoV) by real-time RT-PCR. Euro Surveill 2020;25:2000045
    1. Centers for Disease Control and Prevention. Interim clinical guidance for management of patients with confirmed coronavirus disease (COVID-19). 2020 Jun 30; [Accessed Mar 5, 2021].
    1. American College of Radiology. ACR recommendations for the use of chest radiography and computed tomography (CT) for suspected COVID-19 infection. 2020 Mar 11; [Accessed Mar 5, 2021].
    1. Whold Health Organization. Country & technical guidance - coronavirus disease (COVID-19). 2020 Jan 21; [Accessed Mar 5, 2021].
    1. Rubin GD, Ryerson CJ, Haramati LB, Sverzellati N, Kanne JP, Raoof S, et al. The role of chest imaging in patient management during the COVID-19 pandemic: a multinational consensus statement from the Fleischner Society. Chest 2020;158:106–116.
    1. Kalra MK, Homayounieh F, Arru C, Holmberg O, Vassileva J. Chest CT practice and protocols for COVID-19 from radiation dose management perspective. Eur Radiol 2020;30:6554–6560.
    1. Homayounieh F, Holmberg O, Umairi RA, Aly S, Basevičius A, Costa PR, et al. Variations in CT utilization, protocols, and radiation doses in COVID-19 pneumonia: results from 28 countries in the IAEA Study. Radiology 2021;298:E141–E151.
    1. Guan WJ, Ni ZY, Hu Y, Liang WH, Ou CQ, He JX, et al. Clinical characteristics of coronavirus disease 2019 in China. N Engl J Med 2020;382:1708–1720.
    1. Li K, Wu J, Wu F, Guo D, Chen L, Fang Z, et al. The clinical and chest CT features associated with severe and critical COVID-19 pneumonia. Invest Radiol 2020;55:327–331.
    1. Bernheim A, Mei X, Huang M, Yang Y, Fayad ZA, Zhang N, et al. Chest CT findings in coronavirus disease-19 (COVID-19): relationship to duration of infection. Radiology 2020;295:200463
    1. Ai T, Yang Z, Hou H, Zhan C, Chen C, Lv W, et al. Correlation of chest CT and RT-PCR testing for coronavirus disease 2019 (COVID-19) in China: a report of 1014 cases. Radiology 2020;296:E32–E40.
    1. Caruso D, Zerunian M, Polici M, Pucciarelli F, Polidori T, Rucci C, et al. Chest CT features of COVID-19 in Rome, Italy. Radiology 2020;296:E79–E85.
    1. Schalekamp S, Bleeker-Rovers CP, Beenen LFM, Quarles van Ufford HME, Gietema HA, Stöger JL, et al. Chest CT in the emergency department for diagnosis of COVID-19 pneumonia: dutch experience. Radiology 2021;298:E98–E106.
    1. Xie X, Zhong Z, Zhao W, Zheng C, Wang F, Liu J. Chest CT for typical coronavirus disease 2019 (COVID-19) pneumonia: relationship to negative RT-PCR testing. Radiology 2020;296:E41–E45.
    1. Gostic K, Gomez AC, Mummah RO, Kucharski AJ, Lloyd-Smith JO. Estimated effectiveness of symptom and risk screening to prevent the spread of COVID-19. Elife 2020;9:e55570
    1. Wilder-Smith A, Freedman DO. Isolation, quarantine, social distancing and community containment: pivotal role for old-style public health measures in the novel coronavirus (2019-nCoV) outbreak. J Travel Med 2020;27:taaa020
    1. Shao YH, Tsai K, Kim S, Wu YJ, Demissie K. Exposure to tomographic scans and cancer risks. JNCI Cancer Spectr 2019;4:pkz072
    1. Strauss KJ, Goske MJ, Towbin AJ, Sengupta D, Callahan MJ, Darge K, et al. Pediatric chest CT diagnostic reference ranges: development and application. Radiology 2017;284:219–227.
    1. Pearce MS, Salotti JA, Little MP, McHugh K, Lee C, Kim KP, et al. Radiation exposure from CT scans in childhood and subsequent risk of leukaemia and brain tumours: a retrospective cohort study. Lancet 2012;380:499–505.
    1. Mathews JD, Forsythe AV, Brady Z, Butler MW, Goergen SK, Byrnes GB, et al. Cancer risk in 680,000 people exposed to computed tomography scans in childhood or adolescence: data linkage study of 11 million Australians. BMJ 2013;346:f2360
    1. Tofighi S, Najafi S, Johnston SK, Gholamrezanezhad A. Low-dose CT in COVID-19 outbreak: radiation safety, image wisely, and image gently pledge. Emerg Radiol 2020;27:601–605.
    1. Kang Z, Li X, Zhou S. Recommendation of low-dose CT in the detection and management of COVID-2019. Eur Radiol 2020;30:4356–4357.
    1. Linn S, Grunau PD. New patient-oriented summary measure of net total gain in certainty for dichotomous diagnostic tests. Epidemiol Perspect Innov 2006;3:11
    1. Kim H, Hong H, Yoon SH. Diagnostic performance of CT and reverse transcriptase polymerase chain reaction for coronavirus disease 2019: a meta-analysis. Radiology 2020;296:E145–E155.
    1. National Health Commission & National Administration of Traditional Chinese Medicine. Diagnosis and treatment protocols of COVID-19 infection (trial version 5). 2020 Feb 04; [Accessed Mar 5, 2021].
    1. Yang J, Chen X, Deng X, Chen Z, Gong H, Yan H, et al. Disease burden and clinical severity of the first pandemic wave of COVID-19 in Wuhan, China. Nat Commun 2020;11:5411
    1. Liu R, Han H, Liu F, Lv Z, Wu K, Liu Y, et al. Positive rate of RT-PCR detection of SARS-CoV-2 infection in 4880 cases from one hospital in Wuhan, China, from Jan to Feb 2020. Clin Chim Acta 2020;505:172–175.
    1. Xue H, Jin Z. The appropriate position of radiology in COVID-19 diagnosis and treatment-current status and opinion from China. Chin J Acad Radiol. 2020 Mar; [doi: 10.1007/s42058-020-00030-6]
      [Epub].
    1. Li R, Liu G, Zhang X, Li H. Letter to the editor: chest CT and RT-PCR: radiologists’ experience in the diagnosis of COVID-19 in China. 2020 Mar 30; [Assessed Mar 5, 2021].
    1. New York State. Percentage positive results by county dashboard. 2020 Mar 08; [Accessed Mar 5, 2021].
    1. Our World in Data. The share of COVID-19 tests that are positive. 2020 Jan 06; [Accessed Mar 9, 2021].
    1. Chen D, Jiang X, Hong Y, Wen Z, Wei S, Peng G, et al. Can chest CT features distinguish patients with negative from those with positive initial RT-PCR results for coronavirus disease (COVID-19)? AJR Am J Roentgenol 2021;216:66–70.
    1. Cheng Z, Lu Y, Cao Q, Qin L, Pan Z, Yan F, et al. Clinical features and chest CT manifestations of coronavirus disease 2019 (COVID-19) in a single-center study in Shanghai, China. AJR Am J Roentgenol 2020;215:121–126.
    1. Han R, Huang L, Jiang H, Dong J, Peng H, Zhang D. Early clinical and CT manifestations of coronavirus disease 2019 (COVID-19) pneumonia. AJR Am J Roentgenol 2020;215:338–343.
    1. Huang G, Gong T, Wang G, Wang J, Guo X, Cai E, et al. Timely diagnosis and treatment shortens the time to resolution of coronavirus disease (COVID-19) pneumonia and lowers the highest and last CT scores from sequential chest CT. AJR Am J Roentgenol 2020;215:367–373.
    1. Li Y, Xia L. Coronavirus disease 2019 (COVID-19): role of chest CT in diagnosis and management. AJR Am J Roentgenol 2020;214:1280–1286.
    1. Lin L, Fu G, Chen S, Tao J, Qian A, Yang Y, et al. CT manifestations of coronavirus disease (COVID-19) pneumonia and influenza virus pneumonia: a comparative study. AJR Am J Roentgenol 2021;216:71–79.
    1. Liu D, Li L, Wu X, Zheng D, Wang J, Yang L, et al. Pregnancy and perinatal outcomes of women with coronavirus disease (COVID-19) pneumonia: a preliminary analysis. AJR Am J Roentgenol 2020;215:127–132.
    1. Steinberger S, Lin B, Bernheim A, Chung M, Gao Y, Xie Z, et al. CT features of coronavirus disease (COVID-19) in 30 pediatric patients. AJR Am J Roentgenol 2020;215:1303–1311.
    1. Wang X, Hu X, Tan W, Mazzone P, Mireles-Cabodevila E, Han X, et al. Multicenter study of temporal changes and prognostic value of a CT visual severity score in hospitalized patients with coronavirus disease (COVID-19). AJR Am J Roentgenol 2021;217:83–92.
    1. Yin Z, Kang Z, Yang D, Ding S, Luo H, Xiao E. A comparison of clinical and chest CT findings in patients with influenza A (H1N1) virus infection and coronavirus disease (COVID-19). AJR Am J Roentgenol 2020;215:1065–1071.
    1. Zhao W, Zhong Z, Xie X, Yu Q, Liu J. Relation between chest CT findings and clinical conditions of coronavirus disease (COVID-19) pneumonia: a multicenter study. AJR Am J Roentgenol 2020;214:1072–1077.
    1. Zhou S, Wang Y, Zhu T, Xia L. CT features of coronavirus disease 2019 (COVID-19) pneumonia in 62 patients in Wuhan, China. AJR Am J Roentgenol 2020;214:1287–1294.
    1. Booz C, Vogl TJ, Joseph Schoepf U, Caruso D, Inserra MC, Yel I, et al. Value of minimum intensity projections for chest CT in COVID-19 patients. Eur J Radiol 2021;135:109478
    1. Chen Z, Fan H, Cai J, Li Y, Wu B, Hou Y, et al. High-resolution computed tomography manifestations of COVID-19 infections in patients of different ages. Eur J Radiol 2020;126:108972
    1. Colombi D, Petrini M, Maffi G, Villani GD, Bodini FC, Morelli N, et al. Comparison of admission chest computed tomography and lung ultrasound performance for diagnosis of COVID-19 pneumonia in populations with different disease prevalence. Eur J Radiol 2020;133:109344
    1. Ding X, Xu J, Zhou J, Long Q. Chest CT findings of COVID-19 pneumonia by duration of symptoms. Eur J Radiol 2020;127:109009
    1. Falaschi Z, Danna PSC, Arioli R, Pasché A, Zagaria D, Percivale I, et al. Chest CT accuracy in diagnosing COVID-19 during the peak of the Italian epidemic: a retrospective correlation with RT-PCR testing and analysis of discordant cases. Eur J Radiol 2020;130:109192
    1. Guillo E, Bedmar Gomez I, Dangeard S, Bennani S, Saab I, Tordjman M, et al. COVID-19 pneumonia: diagnostic and prognostic role of CT based on a retrospective analysis of 214 consecutive patients from Paris, France. Eur J Radiol 2020;131:109209
    1. Hu Q, Guan H, Sun Z, Huang L, Chen C, Ai T, et al. Early CT features and temporal lung changes in COVID-19 pneumonia in Wuhan, China. Eur J Radiol 2020;128:109017
    1. Liu KC, Xu P, Lv WF, Qiu XH, Yao JL, Gu JF, et al. CT manifestations of coronavirus disease-2019: a retrospective analysis of 73 cases by disease severity. Eur J Radiol 2020;126:108941
    1. Long C, Xu H, Shen Q, Zhang X, Fan B, Wang C, et al. Diagnosis of the coronavirus disease (COVID-19): rRT-PCR or CT? Eur J Radiol 2020;126:108961
    1. Meiler S, Schaible J, Poschenrieder F, Scharf G, Zeman F, Rennert J, et al. Can CT performed in the early disease phase predict outcome of patients with COVID 19 pneumonia? Analysis of a cohort of 64 patients from Germany. Eur J Radiol 2020;131:109256
    1. Ohana M, Muller J, Severac F, Bilbault P, Behr M, Oberlin M, et al. Temporal variations in the diagnostic performance of chest CT for Covid-19 depending on disease prevalence: experience from North-Eastern France. Eur J Radiol 2021;134:109425
    1. Parry AH, Wani AH, Yaseen M, Dar KA, Choh NA, Khan NA, et al. Spectrum of chest computed tomographic (CT) findings in coronavirus disease-19 (COVID-19) patients in India. Eur J Radiol 2020;129:109147
    1. Tabatabaei SMH, Rahimi H, Moghaddas F, Rajebi H. Predictive value of CT in the short-term mortality of coronavirus disease 2019 (COVID-19) pneumonia in nonelderly patients: a case-control study. Eur J Radiol 2020;132:109298
    1. Besutti G, Giorgi Rossi P, Iotti V, Spaggiari L, Bonacini R, Nitrosi A, et al. Accuracy of CT in a cohort of symptomatic patients with suspected COVID-19 pneumonia during the outbreak peak in Italy. Eur Radiol 2020;30:6818–6827.
    1. Brun AL, Gence-Breney A, Trichereau J, Ballester MC, Vasse M, Chabi ML, et al. COVID-19 pneumonia: high diagnostic accuracy of chest CT in patients with intermediate clinical probability. Eur Radiol 2021;31:1969–1977.
    1. Chen HJ, Qiu J, Wu B, Huang T, Gao Y, Wang ZP, et al. Early chest CT features of patients with 2019 novel coronavirus (COVID-19) pneumonia: relationship to diagnosis and prognosis. Eur Radiol 2020;30:6178–6185.
    1. Francone M, Iafrate F, Masci GM, Coco S, Cilia F, Manganaro L, et al. Chest CT score in COVID-19 patients: correlation with disease severity and short-term prognosis. Eur Radiol 2020;30:6808–6817.
    1. Fu F, Lou J, Xi D, Bai Y, Ma G, Zhao B, et al. Chest computed tomography findings of coronavirus disease 2019 (COVID-19) pneumonia. Eur Radiol 2020;30:5489–5498.
    1. Gu J, Yang L, Li T, Liu Y, Zhang J, Ning K, et al. Temporal relationship between serial RT-PCR results and serial chest CT imaging, and serial CT changes in coronavirus 2019 (COVID-19) pneumonia: a descriptive study of 155 cases in China. Eur Radiol 2021;31:1175–1184.
    1. Li K, Fang Y, Li W, Pan C, Qin P, Zhong Y, et al. CT image visual quantitative evaluation and clinical classification of coronavirus disease (COVID-19). Eur Radiol 2020;30:4407–4416.
    1. Li X, Fang X, Bian Y, Lu J. Comparison of chest CT findings between COVID-19 pneumonia and other types of viral pneumonia: a two-center retrospective study. Eur Radiol 2020;30:5470–5478.
    1. Li Y, Yang Z, Ai T, Wu S, Xia L. Association of “initial CT” findings with mortality in older patients with coronavirus disease 2019 (COVID-19). Eur Radiol 2020;30:6186–6193.
    1. Liang T, Liu Z, Wu CC, Jin C, Zhao H, Wang Y, et al. Evolution of CT findings in patients with mild COVID-19 pneumonia. Eur Radiol 2020;30:4865–4873.
    1. Liu J, Chen T, Yang H, Cai Y, Yu Q, Chen J, et al. Clinical and radiological changes of hospitalised patients with COVID-19 pneumonia from disease onset to acute exacerbation: a multicentre paired cohort study. Eur Radiol 2020;30:5702–5708.
    1. Liu M, Zeng W, Wen Y, Zheng Y, Lv F, Xiao K. COVID-19 pneumonia: CT findings of 122 patients and differentiation from influenza pneumonia. Eur Radiol 2020;30:5463–5469.
    1. Qin L, Yang Y, Cao Q, Cheng Z, Wang X, Sun Q, et al. A predictive model and scoring system combining clinical and CT characteristics for the diagnosis of COVID-19. Eur Radiol 2020;30:6797–6807.
    1. Varble N, Blain M, Kassin M, Xu S, Turkbey EB, Amalou A, et al. CT and clinical assessment in asymptomatic and pre-symptomatic patients with early SARS-CoV-2 in outbreak settings. Eur Radiol 2021;31:3165–3176.
    1. Wang H, Wei R, Rao G, Zhu J, Song B. Characteristic CT findings distinguishing 2019 novel coronavirus disease (COVID-19) from influenza pneumonia. Eur Radiol 2020;30:4910–4917.
    1. Wang YC, Luo H, Liu S, Huang S, Zhou Z, Yu Q, et al. Dynamic evolution of COVID-19 on chest computed tomography: experience from Jiangsu Province of China. Eur Radiol 2020;30:6194–6203.
    1. Wu J, Pan J, Teng D, Xu X, Feng J, Chen YC. Interpretation of CT signs of 2019 novel coronavirus (COVID-19) pneumonia. Eur Radiol 2020;30:5455–5462.
    1. Zhan J, Li H, Yu H, Liu X, Zeng X, Peng D, et al. 2019 novel coronavirus (COVID-19) pneumonia: CT manifestations and pattern of evolution in 110 patients in Jiangxi, China. Eur Radiol 2021;31:1059–1068.
    1. Zhang N, Xu X, Zhou LY, Chen G, Li Y, Yin H, et al. Clinical characteristics and chest CT imaging features of critically ill COVID-19 patients. Eur Radiol 2020;30:6151–6160.
    1. Zhang R, Ouyang H, Fu L, Wang S, Han J, Huang K, et al. CT features of SARS-CoV-2 pneumonia according to clinical presentation: a retrospective analysis of 120 consecutive patients from Wuhan city. Eur Radiol 2020;30:4417–4426.
    1. Zhou S, Zhu T, Wang Y, Xia L. Imaging features and evolution on CT in 100 COVID-19 pneumonia patients in Wuhan, China. Eur Radiol 2020;30:5446–5454.
    1. Zhou Y, Zheng Y, Yang Q, Hu L, Liao J, Li X. Cohort study of chest CT and clinical changes in 29 patients with coronavirus disease 2019 (COVID-19). Eur Radiol 2020;30:6213–6220.
    1. Zhou Z, Guo D, Li C, Fang Z, Chen L, Yang R, et al. Coronavirus disease 2019: initial chest CT findings. Eur Radiol 2020;30:4398–4406.
    1. Lyu P, Liu X, Zhang R, Shi L, Gao J. The performance of chest CT in evaluating the clinical severity of COVID-19 pneumonia: identifying critical cases based on CT characteristics. Invest Radiol 2020;55:412–421.
    1. Wu J, Wu X, Zeng W, Guo D, Fang Z, Chen L, et al. Chest CT findings in patients with coronavirus disease 2019 and its relationship with clinical features. Invest Radiol 2020;55:257–261.
    1. Xiong Y, Sun D, Liu Y, Fan Y, Zhao L, Li X, et al. Clinical and high-resolution CT features of the COVID-19 infection: comparison of the initial and follow-up changes. Invest Radiol 2020;55:332–339.
    1. Lan L, Xu D, Xia C, Wang S, Yu M, Xu H. Early CT findings of coronavirus disease 2019 (COVID-19) in asymptomatic children: a single-center experience. Korean J Radiol 2020;21:919–924.
    1. Liu Z, Jin C, Wu CC, Liang T, Zhao H, Wang Y, et al. Association between initial chest CT or clinical features and clinical course in patients with coronavirus disease 2019 pneumonia. Korean J Radiol 2020;21:736–745.
    1. Yoon SH, Lee KH, Kim JY, Lee YK, Ko H, Kim KH, et al. Chest radiographic and CT findings of the 2019 novel coronavirus disease (COVID-19): analysis of nine patients treated in Korea. Korean J Radiol 2020;21:494–500.
    1. Yu M, Liu Y, Xu D, Zhang R, Lan L, Xu H. Prediction of the development of pulmonary fibrosis using serial thin-section CT and clinical features in patients discharged after treatment for COVID-19 pneumonia. Korean J Radiol 2020;21:746–755.
    1. Shi H, Han X, Jiang N, Cao Y, Alwalid O, Gu J, et al. Radiological findings from 81 patients with COVID-19 pneumonia in Wuhan, China: a descriptive study. Lancet Infect Dis 2020;20:425–434.
    1. Caro-Dominguez P, Shelmerdine SC, Toso S, Secinaro A, Toma P, Damasio MB, et al. Thoracic imaging of coronavirus disease 2019 (COVID-19) in children: a series of 91 cases. Pediatr Radiol 2020;50:1354–1368.
    1. Li W, Cui H, Li K, Fang Y, Li S. Chest computed tomography in children with COVID-19 respiratory infection. Pediatr Radiol 2020;50:796–799.
    1. Peng X, Guo Y, Xiao H, Xia W, Zhai A, Zhu B, et al. Overview of chest involvement at computed tomography in children with coronavirus disease 2019 (COVID-19). Pediatr Radiol 2021;51:222–230.
    1. Chung M, Bernheim A, Mei X, Zhang N, Huang M, Zeng X, et al. CT imaging features of 2019 novel coronavirus (2019-nCoV). Radiology 2020;295:202–207.
    1. De Smet K, De Smet D, Ryckaert T, Laridon E, Heremans B, Vandenbulcke R, et al. Diagnostic performance of chest CT for SARS-CoV-2 infection in individuals with or without COVID-19 symptoms. Radiology 2021;298:E30–E37.
    1. Fang Y, Zhang H, Xie J, Lin M, Ying L, Pang P, et al. Sensitivity of chest CT for COVID-19: comparison to RT-PCR. Radiology 2020;296:E115–E117.
    1. Hameed S, Elbaaly H, Reid CEL, Santos RMF, Shivamurthy V, Wong J, et al. Spectrum of imaging findings at chest radiography, US, CT, and MRI in multisystem inflammatory syndrome in children associated with COVID-19. Radiology 2021;298:E1–E10.
    1. Herpe G, Lederlin M, Naudin M, Ohana M, Chaumoitre K, Gregory J, et al. Efficacy of chest CT for COVID-19 pneumonia diagnosis in France. Radiology 2021;298:E81–E87.
    1. Pan F, Ye T, Sun P, Gui S, Liang B, Li L, et al. Time course of lung changes on chest CT during recovery from 2019 novel coronavirus (COVID-19) pneumonia. Radiology 2020;295:715–721.
    1. Wang Y, Dong C, Hu Y, Li C, Ren Q, Zhang X, et al. Temporal changes of CT findings in 90 patients with COVID-19 pneumonia: a longitudinal study. Radiology 2020;296:E55–E64.
    1. Chen A, Huang JX, Liao Y, Liu Z, Chen D, Yang C, et al. Differences in clinical and imaging presentation of pediatric patients with COVID-19 in comparison with adults. Radiol Cardiothorac Imaging 2020;2:e200117
    1. Choi H, Qi X, Yoon SH, Park SJ, Lee KH, Kim JY, et al. Extension of coronavirus disease 2019 on chest CT and implications for chest radiographic interpretation. Radiol Cardiothorac Imaging 2020;2:e200107
    1. Dangis A, Gieraerts C, De Bruecker Y, Janssen L, Valgaeren H, Obbels D, et al. Accuracy and reproducibility of low-dose submillisievert chest CT for the diagnosis of COVID-19. Radiol Cardiothorac Imaging 2020;2:e200196
    1. Grodecki K, Lin A, Cadet S, McElhinney PA, Razipour A, Chan C, et al. Quantitative burden of COVID-19 pneumonia on chest CT predicts adverse outcomes: a post-hoc analysis of a prospective international registry. Radiol Cardiothorac Imaging 2020;2:e200389
    1. Henkel M, Weikert T, Marston K, Schwab N, Sommer G, Haslbauer J, et al. Lethal COVID-19: radiologic-pathologic correlation of the lungs. Radiol Cardiothorac Imaging 2020;2:e200406
    1. Inui S, Fujikawa A, Jitsu M, Kunishima N, Watanabe S, Suzuki Y, et al. Chest CT findings in cases from the cruise ship diamond princess with coronavirus disease (COVID-19). Radiol Cardiothorac Imaging 2020;2:e200110
    1. Moradi B, Ghanaati H, Kazemi MA, Gity M, Hashemi H, Davari-Tanha F, et al. Implications of sex difference in CT scan findings and outcome of patients with COVID-19 pneumonia. Radiol Cardiothorac Imaging 2020;2:e200248
    1. Ng MY, Lee EYP, Yang J, Yang F, Li X, Wang H, et al. Imaging profile of the COVID-19 infection: radiologic findings and literature review. Radiol Cardiothorac Imaging 2020;2:e200034
    1. Som A, Lang M, Yeung T, Carey D, Garrana S, Mendoza DP, et al. Implementation of the Radiological Society of North America expert consensus guidelines on reporting chest CT findings related to COVID-19: a multireader performance study. Radiol Cardiothorac Imaging 2020;2:e200276
    1. Tabatabaei SMH, Talari H, Moghaddas F, Rajebi H. CT features and short-term prognosis of COVID-19 pneumonia: a single-center study from Kashan, Iran. Radiol Cardiothorac Imaging 2020;2:e200130
    1. Wen Z, Chi Y, Zhang L, Liu H, Du K, Li Z, et al. Coronavirus disease 2019: initial detection on chest CT in a retrospective multicenter study of 103 Chinese patients. Radiol Cardiothorac Imaging 2020;2:e200092
    1. Yang R, Li X, Liu H, Zhen Y, Zhang X, Xiong Q, et al. Chest CT severity score: an imaging tool for assessing severe COVID-19. Radiol Cardiothorac Imaging 2020;2:e200047
    1. Yu M, Xu D, Lan L, Tu M, Liao R, Cai S, et al. Thin-section chest CT imaging of COVID-19 pneumonia: a comparison between patients with mild and severe disease. Radiol Cardiothorac Imaging 2020;2:e200126
    1. Ciccarese F, Coppola F, Spinelli D, Galletta GL, Lucidi V, Paccapelo A, et al. Diagnostic accuracy of north america expert consensus statement on reporting CT findings in patients suspected of having COVID-19 infection: an italian single-center experience. Radiol Cardiothorac Imaging 2020;2:e200312
    1. Kwee TC, Kwee RM. Chest CT in COVID-19: what the radiologist needs to know. Radiographics 2020;40:1848–1865.
    1. Lee C. Managing radiation dose from chest CT in patients with COVID-19. Radiology 2020;298:E158–E159.
    1. Miglioretti DL, Johnson E, Williams A, Greenlee RT, Weinmann S, Solberg LI, et al. The use of computed tomography in pediatrics and the associated radiation exposure and estimated cancer risk. JAMA Pediatr 2013;167:700–707.
    1. Centers for Disese Control and Prevention. ALARA - as low as reasonably achievable. 2015 Dec 07; [Accessed Mar 5, 2021].
    1. Ebdon-Jackson S, Frija G. European Society of Radiology. Improving justification of medical exposures using ionising radiation: considerations and approaches from the European Society of Radiology. Insights Imaging 2021;12:2
    1. Mazzone PJ, Silvestri GA, Patel S, Kanne JP, Kinsinger LS, Wiener RS, et al. Screening for lung cancer: CHEST guideline and expert panel report. Chest 2018;153:954–985.
    1. Claessens YE, Debray MP, Tubach F, Brun AL, Rammaert B, Hausfater P, et al. Early chest computed tomography scan to assist diagnosis and guide treatment decision for suspected community-acquired pneumonia. Am J Respir Crit Care Med 2015;192:974–982.
    1. Prendki V, Scheffler M, Huttner B, Garin N, Herrmann F, Janssens JP, et al. Low-dose computed tomography for the diagnosis of pneumonia in elderly patients: a prospective, interventional cohort study. Eur Respir J 2018;51:1702375
    1. National Lung Screening Trial Research Team. Aberle DR, Adams AM, Berg CD, Black WC, Clapp JD, et al. Reduced lung-cancer mortality with low-dose computed tomographic screening. N Engl J Med 2011;365:395–409.
    1. Lee KH, Lee S, Park JH, Lee SS, Kim HY, Lee WJ, et al. Risk of hematologic malignant neoplasms from abdominopelvic computed tomographic radiation in patients who underwent appendectomy. JAMA Surg 2021;156:343–351.
    1. Wang X, Yao H, Xu X, Zhang P, Zhang M, Shao J, et al. Limits of detection of 6 approved RT-PCR kits for the novel SARS-coronavirus-2 (SARS-CoV-2). Clin Chem 2020;66:977–979.
    1. Tordjman M, Mekki A, Mali RD, Saab I, Chassagnon G, Guillo E, et al. Pre-test probability for SARS-Cov-2-related infection score: the PARIS score. PLoS One 2020;15:e0243342

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