Quantitative Assessment of Lung Volumes and Enhancement in Patients with COVID-19: Role of Dual-Energy CT.

Dual-energy computed tomography (DECT) has been used for detecting pulmonary embolism, but the role of lung perfusion DECT as a predictor of prognosis of coronavirus disease 2019 (COVID-19) has not been defined yet. The aim of our study was to explore whether the enhancement pattern in COVID-19+ patients relates to the disease outcome. A secondary aim was to compare the lung volumes in two subgroups of patients. In this observational study, we considered all consecutive COVID-19+ patients who presented to the emergency room between January 2021 and December 2021 with respiratory symptoms (with mild to absent lung consolidation) and were studied by chest contrast-enhanced DECT to be eligible. Two experienced radiologists post-processed the images using the "lung-analysis" software (SyngoVia). Absolute and relative enhancement lung volumes were assessed. Patients were stratified in two subgroups depending on clinical outcome at 30 days: (i) good outcome (i.e., discharge, absence of clinical or imaging signs of disease); (ii) bad outcome (i.e., hospitalization, death). Patient sub-groups were compared using chi-square test or Fisher test for qualitative parameters, chi-square test or Spearman's Rho test for quantitative parameters, Students' t-test for parametric variables and Wilcoxon test for non-parametric variables. We enrolled 78 patients (45M), of whom, 16.7% had good outcomes. We did not observe any significant differences between the two groups, both in terms of the total enhancement evaluation (p = 0.679) and of the relative enhancement (p = 0.918). In contrast, the average lung volume of good outcome patients (mean value of 4262 mL) was significantly larger than that of bad outcome patients (mean value of 3577.8 mL), p = 0.0116. All COVID-19+ patients, with either good or bad outcomes, presented similar enhancement parameters and relative enhancements, underlining no differences in lung perfusion. Conversely, a significant drop in lung volume was identified in the bad outcome subgroup eligible compared to the good outcome subgroup.

Chest dual-energy CT to assess the effects of steroids on lung function in severe COVID-19 patients.

BACKGROUND: Steroids have been shown to reduce inflammation, hypoxic pulmonary vasoconstriction (HPV) and lung edema. Based on evidence from clinical trials, steroids are widely used in severe COVID-19. However, the effects of steroids on pulmonary gas volume and blood volume in this group of patients are unexplored. OBJECTIVE: Profiting by dual-energy computed tomography (DECT), we investigated the relationship between the use of steroids in COVID-19 and distribution of blood volume as an index of impaired HPV. We also investigated whether the use of steroids influences lung weight, as index of lung edema, and how it affects gas distribution. METHODS: Severe COVID-19 patients included in a single-center prospective observational study at the intensive care unit at Uppsala University Hospital who had undergone DECT were enrolled in the current study. Patients' cohort was divided into two groups depending on the administration of steroids. From each patient's DECT, 20 gas volume maps and the corresponding 20 blood volume maps, evenly distributed along the cranial-caudal axis, were analyzed. As a proxy for HPV, pulmonary blood volume distribution was analyzed in both the whole lung and the hypoinflated areas. Total lung weight, index of lung edema, was estimated. RESULTS: Sixty patients were analyzed, whereof 43 received steroids. Patients not exposed to steroids showed a more extensive non-perfused area (19% vs 13%, p < 0.01) and less homogeneous pulmonary blood volume of hypoinflated areas (kurtosis: 1.91 vs 2.69, p < 0.01), suggesting a preserved HPV compared to patients treated with steroids. Moreover, patients exposed to steroids showed a significantly lower lung weight (953 gr vs 1140 gr, p = 0.01). A reduction in alveolar-arterial difference of oxygen followed the treatment with steroids (322 ± 106 mmHg at admission vs 267 ± 99 mmHg at DECT, p = 0.04). CONCLUSIONS: The use of steroids might cause impaired HPV and might reduce lung edema in severe COVID-19. This is consistent with previous findings in other diseases. Moreover, a reduced lung weight, as index of decreased lung edema, and a more homogeneous distribution of gas within the lung were shown in patients treated with steroids. TRIAL REGISTRATION: Clinical Trials ID: NCT04316884, Registered March 13, 2020.

Persistent respiratory failure after SARS-CoV-2 infection: The role of dual energy computed tomography. A case report.

Background: COVID-19 disease is often complicated by respiratory failure, developing through multiple pathophysiological mechanisms, with pulmonary embolism (PE) and microvascular thrombosis as key and frequent components. Newer imaging modalities such as dual-energy computed tomography (DECT) can represent a turning point in the diagnosis and follow-up of suspected PE during COVID-19. Case presentation: A 78-year-old female presented to our internal medicine 3 weeks after initial hospitalization for COVID-19 disease, for recrudescent respiratory failure needing oxygen therapy. A computed tomography (CT) lungs scan showed a typical SARSCoV-2 pneumonia. Over the following 15 days, respiratory function gradually improved. Unexpectedly, after 21 days from symptom onset, the patient started complaining of breath shortening with remarkable desaturation requiring high-flow oxygen ventilation. CT pulmonary angiography and transthoracic echocardiography were negative for signs of PE. Thereby, Dual-energy CT angiography of the lungs (DECT) was performed and detected diffuse peripheral microembolism. After 2 weeks, a second DECT was performed, showing a good response to the anticoagulation regimen, with reduced extent of microembolism and some of the remaining emboli partially recanalized. Discussion: DECT is an emerging diagnostic technique providing both functional and anatomical information. DECT has been reported to produce a much sharper delineation of perfusion defects than pulmonary scintigraphy, using a significantly lower equivalent dose of mSv. We highlight that DECT is particularly useful in SARS-Cov-2 infection, in order to determine the predominant underlying pathophysiology, particularly when respiratory failure prolongs despite improved lung parenchymal radiological findings.

A Health System's Response to the Ongoing Global Shortage of Iodinated Contrast Media.

A production facility shutdown related to containment measures during the COVID-19 pandemic has resulted in a global shortage of iodinated contrast media. This article describes the strategies implemented at one large U.S. health system to maintain care continuity during the ongoing shortage. The strategies have included attempts to procure additional stock, repackage existing stock for use in larger numbers of patients, use noncontrast CT or alternative imaging modalities in place of contrast-enhanced CT, and collaborate with specialties outside of radiology to participate in conservation efforts. In addition, individual CT protocols underwent tailored modifications to use dual-energy technique and/or lower tube voltages, to allow lower contrast media doses with maintained visualization of tissue enhancement. The experiences during this period provide insights to facilitate long-term reductions in contrast media doses and ongoing CT protocol optimization after supplies return to normal levels. Critical throughout the efforts to mitigate the impact of the shortage have been system-level action, operational flexibility, and close communication by the health system's radiologists, technologists, physicists, pharmacists, and ordering providers.

The Role of Dual-Energy Computed Tomography in Locating Gastrointestinal Tract Perforations.

Objective With each passing day, dual-energy computed tomography (DECT) is being used more frequently in the evaluation of abdominal pathologies. In this article, we aimed to assess the role of dual-energy CT in locating gastrointestinal perforations, which are among the causes of acute abdomen. Materials and methods All patients who underwent DECT due to acute abdomen in a COVID-19 designated hospital between June 1st, 2020 and December 31st, 2020, who were found to have gastrointestinal tract (GIT) perforation and underwent surgery were included in the study. DECT results and intraoperative findings of the patients were compared. Results Thirteen patients (nine males and four females) who underwent DECT for acute abdomen and were diagnosed with perforation in the gastrointestinal system were included in the study. The mean age of the patients was 57.6 years (range: 11-85 years). Two patients had gastric perforation, three had duodenal perforations, and one patient had a perforation in the gallbladder wall. Two patients were diagnosed with jejunal perforations, one patient with Meckel's diverticulum, and three patients with colorectal perforation. Although free air was detected in the abdomen of one patient, perforation could not be located. In patients with GIT perforation who were operated on following DECT imaging, the perforation location shown on DECT correlated 100% with the perforation locations detected during surgery. Conclusion DECT is significantly effective in planning surgical treatment and determining the foci of perforation in GIT perforations.

Assessment of pulmonary arterial circulation 3 months after hospitalization for SARS-CoV-2 pneumonia: Dual-energy CT (DECT) angiographic study in 55 patients.

BACKGROUND: During COVID-19, the main manifestations of the disease are not only pneumonia but also coagulation disorders. The purpose of this study was to evaluate pulmonary vascular abnormalities 3 months after hospitalization for SARS-CoV-2 pneumonia in patients with persistent respiratory symptoms. METHODS: Among the 320 patients who participated in a systematic follow-up 3 months after hospitalization, 76 patients had residual symptoms justifying a specialized follow-up in the department of pulmonology. Among them, dual-energy CT angiography (DECTA) was obtained in 55 patients. FINDINGS: The 55 patients had partial (n = 40; 72.7%) or complete (n = 15; 27.3%) resolution of COVID-19 lung infiltration. DECTA was normal in 52 patients (52/55; 94.6%) and showed endoluminal filling defects in 3 patients (3/55; 5.4%) at the level of one (n = 1) and two (n = 1) segmental arteries of a single lobe and within central and peripheral arteries (n = 1). DECT lung perfusion was rated as non-interpretable (n = 2;3.6%), normal (n = 17; 30.9%) and abnormal (n = 36; 65.5%), the latter group comprising 32 patients with residual COVID-19 opacities (32/36; 89%) and 4 patients with normal lung parenchyma (4/36; 11%). Perfusion abnormalities consisted of (a) patchy defects (30/36; 83%), (b) PE-type defects (6/36; 16.6%) with (n = 1) or without proximal thrombosis (n = 5); and (c) focal areas of hypoperfusion (2/36; 5.5%). Increased perfusion was seen in 15 patients, always matching GGOs, bands and/or vascular tree-in- bud patterns. INTERPRETATION: DECT depicted proximal arterial thrombosis in 5.4% of patients and perfusion abnormalities suggestive of widespread microangiopathy in 65.5% of patients. Lung microcirculation was abnormal in 4 patients with normal lung parenchyma.

Spectrum of lung perfusion changes on dual-energy CT in COVID-19: incremental benefit to conventional CT.

The purpose of this case report is to demonstrate lung perfusion changes on dual-energy CT (DECT) in patients with Coronavirus disease 2019 (COVID-19). Since the first case of COVID-19 was reported in Wuhan, Hubei province in China, the spectrum of lung parenchymal findings has been well described but the underlying pathophysiology is less well understood. DECT imaging contributes to the growing evidence that vascular dysregulation has an important role in the underlying pathophysiology of the disease. Three patients with reverse transcriptase polymerase chain reaction (RT-PCR)-confirmed COVID-19 underwent DECT scans. One patient had a DECT for persistent spikes in temperature while the other two patients underwent dual-energy CT pulmonary angiograms (CTPA) for worsening shortness of breath, elevated D dimers and suspected pulmonary embolism. The perfusion abnormalities include focal areas of both hyperperfusion, hypoperfusion, and areas of hypoperfusion surrounded by hyperemia. In addition, dilatation of segmental and subsegmental pulmonary arteries was seen in relation to the lung parenchymal change. DECT has proven useful in supporting the hypothesis that vascular dysregulation plays a significant role in the pulmonary pathophysiology of COVID-19. Early identification and a high index of suspicion  is required in the emergency department setting to identify and isolate cases even prior to the results of RT-PCR test being available. Vascular changes on DECT may be an additional radiological feature in detecting the presence of and predicting the severity of disease in the emergency department or acute care setting.

SARS-CoV-2: what it is, how it acts, and how it manifests in imaging studies. / SARS-CoV-2: cómo es, cómo actúa y cómo se expresa en la imagen.

COVID-19 is a disease with many clinical, biochemical, and radiological signs that has a predilection for the lungs, probably because of the high number of ACE-2 receptors in this organ. The infection of cells activates proinflammatory substances, causing diffuse alveolar damage, which is the histopathological basis of ARDS. The exudative phase would manifest as ground-glass opacities and consolidation, and the proliferative phase would manifest as a tendency toward a more linear morphology. Both CT and PET/CT findings support the inflammatory character of the lung lesions in the initial phase of the disease and in patients with mild-moderate disease. Severe cases have pulmonary hypoperfusion that is likely due to abnormal alveolar ventilation and perfusion. On the other hand, a prothrombotic state increases the risk of thromboembolic disease through the activation of coagulation and platelet pathways with the production of fibrin degradation products (D-dimer) and consumption of platelets.