CT Examinations for COVID-19: A Systematic Review of Protocols, Radiation Dose, and Numbers Needed to Diagnose and Predict

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

Technological Progress in Generation of Induced Pluripotent Stem Cells for Clinical Applications

Reprogramming of somatic cells into induced pluripotent stem cells (iPSCs) is achieved by viral-mediated transduction of defined transcription factors. Generation of iPSCs is of great medical interest as they have the potential to be a source of patient-specific cells. For the eventual goal of clinical application, it is necessary to overcome the limitations of low reprogramming efficiency and chromosomal abnormalities due to viral DNA integration. In this paper, we summarize the current state of reprogramming technology for generation of iPSCs and also discuss potential approaches to the development of safe iPSCs for personalized cell-based replacement therapy

Sequential morphological changes in follow-up CT of pulmonary mucormycosis

PURPOSEWe aimed to describe the computed tomography (CT) features of pulmonary mucormycosis including sequential changes between follow-ups. MATERIALS AND METHODSBetween June 2001 and May 2011, five patients (three males and two females; median age, 43 years; age range, 13–73 years) who had been pathologically diagnosed with pulmonary mucormycosis constituted our study population. Their clinical and CT features including sequential changes over follow-ups were evaluated retrospectively. RESULTSAll patients were immunocompromised due to either hematologic diseases (n=3), diabetes mellitus (n=1), or steroid administration for autoimmune hepatitis (n=1). All patients had symptoms such as fever (n=5), tachycardia (n=1), or pleuritic chest pain (n=1) on admission. Regarding the clinical outcome after treatment, one patient died, and the remaining four recovered from the disease. In terms of initial CT features, the morphologies of pulmonary mucormycosis included a single mass (n=3), consolidation (n=1), or multiple masses (n=1). There were seven pulmonary lesions in total, 3–7 cm in size, which showed a CT halo sign (n=3), reversed-halo sign (n=2), or air-fluid levels (n=2). On follow-up CTs, the lesions of all patients contained necrosis. All three patients with a mass or masses with a CT halo sign on initial CT had a decreased surrounding halo followed by central necrosis, and the lesions gradually decreased in size on recovery. CONCLUSIONPulmonary mucormycosis usually manifests as a mass or masses with a halo or reversed-halo sign on the initial CT scan followed by a decreased extent of surrounding ground-glass opacities with the development of internal necrosis during follow-up

Unidirectional emission from a cardioid-shaped microcavity laser

We find unidirectional emission in a cardioid-shaped microcavity laser. When a deformation parameter is well adjusted, rays starting around a period-5 unstable periodic orbit emit unidirectionally. To confirm the emission direction, we fabricate a laser by using an InGaAsP semiconductor and investigate emission characteristics. When the laser is excited by current injection with a dc current, resonances localized on the period-5 unstable periodic orbit emit unidirectionally. © 2016 Optical Society of America.1

Chirality of a resonance in the absence of backscatterings

Chirality of a resonance localized on an islands chain is studied in a deformed Reuleaux triangular-shaped microcavity, where clockwise and counter clockwise traveling rays are classically separated. A resonance localized on a period-5 islands chain exhibits chiral emission due to the asymmetric cavity shape. Chirality is experimentally proved in a InGaAsP multiquantum-well semiconductor laser by showing that the experimental emission characteristics well coincide with the wave dynamical ones. (C) 2017 Optical Society of America1

THE ANTERIOR CRUCIATE LIGAMENT INURY PREVENTION PROGRAM: A META-ANALYSIS

The purpose of this study was to evaluate the effect of a neuromuscular protocol on the prevention of anterior cruciate ligament (ACL) injury by performing meta-analysis. An extensive literature review was conducted to identify relevant studies, and eventually, only seven randomized controlled trials or prospective cohort studies were included in the analysis. Subgroup analysis revealed that an age under 18, soccer rather than handball, pre- and in-season training rather than either pre or in-season training, and the plyometrics and strengthening components rather than balancing were significant. Metaanalysis showed that pre- and in-season neuromuscular training with an emphasis on plyometrics and strengthening exercises was effective at preventing ACL injury in female athletes, especially in those under 18 years of age

Impact of radiation dose and iterative reconstruction on pulmonary nodule measurements at chest CT: a phantom study

PURPOSEWe aimed to identify the impact of radiation dose and iterative reconstruction (IR) on measurement of pulmonary nodules by chest computed tomography (CT).METHODSCT scans were performed on a chest phantom containing various nodules (diameters of 3, 5, 8, 10, and 12 mm; +100, -630 and -800 HU for each diameter) at 80, 100, 120 kVp and 10, 20, 50, 100 mAs (a total of 12 radiation dose settings). Each CT was reconstructed using filtered back projection, iDose4, and iterative model reconstruction (IMR). Thereafter, two radiologists measured the diameter and attenuation of the nodules. Noise, contrast-to-noise ratio and signal-to-noise ratio of CT images were also obtained. Influence of radiation dose and reconstruction algorithm on measurement error and objective image quality metrics was analyzed using generalized estimating equations.RESULTSThe 80 kVp, 10 mAs CT scan was not feasible for the measurement of 3 mm sized simulated ground-glass nodule (GGN); otherwise, diameter measurement error was not significantly influenced by radiation dose (P > 0.05). IR did not have a significant impact on diameter measurement error for simulated solid nodules (P > 0.05). However, for simulated GGNs, IMR was associated with significantly decreased relative diameter measurement error (P 0.05). Objective image quality was significantly better with IMR (P < 0.05).CONCLUSIONNodule measurements were not affected by radiation dose except for 3 mm simulated GGN on 80 kVp, 10 mAs dose setting. However, for GGNs, IMR may help reduce diameter measurement error while improving image quality

Pulmonary subsolid nodules: what radiologists need to know about the imaging features and management strategy

Pulmonary subsolid nodules (SSNs) refer to pulmonary nodules with pure ground-glass nodules and part-solid ground-glass nodules. SSNs are frequently encountered in the clinical setting, such as screening chest computed tomography (CT). The main concern regarding pulmonary SSNs, particularly when they are persistent, has been lung adenocarcinoma and its precursors. The CT manifestations of SSNs help radiologists and clinicians manage these lesions. However, the management plan for SSNs has not previously been standardized. Recently, the Fleischner Society published recommendations for the management of incidentally detected SSNs. The guidelines reflect the new lung adenocarcinoma classification system proposed by the International Association for the Study of Lung Cancer, American Thoracic Society, and European Respiratory Society (IASLC/ATS/ERS) and include six specific recommendations according to the nodule size, solid portion and multiplicity. This review aims to increase the understanding of SSNs and the imaging features of SSNs according to their histology, natural course, possible radiologic interventions, such as biopsy, localization prior to surgery, and current management