Incidental diagnosis of Covid-19 pneumonia on chest computed tomography.

PURPOSE: The purpose of this study was to determine the prevalence and imaging characteristics of incidentally diagnosed COVID-19 pneumonia on computed tomography (CT). MATERIALS AND METHODS: This retrospective study was conducted between March 20th and March 31st, 2020 at Cochin hospital, Paris France. Thoracic CT examinations of all patients referred for another reason than a suspicion of SARS-CoV-2 infection were reviewed. CT images were analyzed by a chest radiologist to confirm the presence of findings consistent with COVID-19 pneumonia and quantify disease extent. Clinical and biological data (C-reactive protein serum level [CRP] and white blood cell count) of patients with CT findings suggestive for COVID-19 pneumonia were retrieved from the electronic medical chart. RESULTS: During the study period, among 205 diagnostic CT examinations, six examinations (6/205, 3%) in 6 different patients (4 men, 2 women; median age, 57 years) revealed images highly suggestive of COVID-19 pneumonia. The final diagnosis was confirmed by RT-PCR. Three inpatients were suspected of extra thoracic infection whereas three outpatients were either fully asymptomatic or presented with fatigue only. All had increased CRP serum level and lymphopenia. Disease extent on CT was mild to moderate in 5/6 patients (83%) and severe in 1/6 patient (17%). CONCLUSION: Cumulative incidence of fortuitous diagnosis if COVID-19 pneumonia did not exceed 3% during the highest pandemic phase and was predominantly associated with limited lung involvement.

COVID-19 pneumonia: A review of typical CT findings and differential diagnosis.

The standard of reference for confirming COVID-19 relies on microbiological tests such as real-time polymerase chain reaction (RT-PCR) or sequencing. However, these tests might not be available in an emergency setting. Computed tomography (CT) can be used as an important complement for the diagnosis of COVID-19 pneumonia in the current epidemic context. In this review, we present the typical CT features of COVID-19 pneumonia and discuss the main differential diagnosis.

Optimization of acquisition parameters for reduced-dose thoracic CT: A phantom study.

PURPOSE: The purpose of this study was to analyze the impact of different options for reduced-dose computed tomography (CT) on image noise and visibility of pulmonary structures in order to define the best choice of parameters when performing ultra-low dose acquisitions of the chest in clinical routine. MATERIALS AND METHODS: Using an anthropomorphic chest phantom, CT images were acquired at four defined low dose levels (computed tomography dose index [CTDIvol]=0.15, 0.20, 0.30 and 0.40mGy), by changing tube voltage, pitch factor, or rotation time and adapting tube current to reach the predefined CTDIvol-values. Images were reconstructed using two different levels of iteration (adaptive statistical iterative reconstruction [ASIR®]-v70% and ASIR®-v100%). Signal-to-noise ratio (SNR) as well as contrast-to-noise ratio (CNR) was calculated. Visibility of pulmonary structures (bronchi/vessels) were assessed by two readers on a 5-point-Likert scale. RESULTS: Best visual image assessments and CNR/SNR were obtained with high tube voltage, while lowest scores were reached with lower pitch factor followed by high tube current. Protocols favoring lower pitch factor resulted in decreased visibility of bronchi/vessels, especially in the periphery. Decreasing radiation dose from 0.40 to 0.30mGy was not associated with a significant decrease in visual scores (P<0.05), however decreasing radiation dose from 0.30mGy to 0.15mGy was associated with a lower visibility of most of the evaluated structures (P<0.001). While image noise could be significantly reduced when ASIR®-v100% instead of ASIR®-v70% was used, the visibility-scores of pulmonary structures did not change significantly. CONCLUSION: Favoring high tube voltage is the best option for reduced-dose protocols. A decrease of SNR and CNR does not necessarily go along with reduced visibility of pulmonary structures.

[Modern imaging in cerebral vein angioma]. / L'imagerie moderne dans les angiomes veineux cérébraux.

Cerebral venous angiomas are vascular malformations of the brain which, before the advent of modern imaging, and in particular MRI, were thought to be rare. They have a specific angiographic aspect called "caput Meduse" as it corresponds to the description of a large draining vein to which converge numerous radial veins located in the white matter. These true vascular malformations have characteristic histological features making it possible to differentiate them from other vascular malformations, notably cavernomas. These lesions are less scanty than classically believed, being the most frequent malformations encountered in post-mortem examination series. The circumstances in which cerebral venous angiomas are discovered vary considerably, and haemorrhage can be the revealing sign. Some authors regard these malformations as "abnormalities" of white matter veins and not as pathological entities, since they derive from a change in development during embryogenesis, but this theory is not supported by any anatomical evidence. The same authors attribute the bleeding to an associated cavernoma. Whereas CT enables venous angiomas and possible associated cavernomas to be detected, only repeated MRI explorations performed after the finding of venous angioma and hemorrhage can permit, by analysis of signal changes, to confirm or invalidate the non-pathological theory of the venous malformation and its tendency to bleed. Apart from hemorrhages, since gadolinium is used MRI is the most reliable and least invasive means to diagnose angiomas and to detect associated occult angiographic malformations. For this reason, nowadays only hemorrhages require an angiography in search of an arteriovenous malformation demanding prompt treatment. Moreover, MRI makes it possible to detect angiographically occult malformations.