COVID-19 pneumonia imaging follow-up: when and how? A proposition from ESTI and ESR.

This document from the European Society of Thoracic Imaging (ESTI) and the European Society of Radiology (ESR) discusses the role of imaging in the long-term follow-up of COVID-19 patients, to define which patients may benefit from imaging, and what imaging modalities and protocols should be used. Insights into imaging features encountered on computed tomography (CT) scans and potential pitfalls are discussed and possible areas for future review and research are also included. KEY POINTS: • Post-COVID-19 pneumonia changes are mainly consistent with prior organizing pneumonia and are likely to disappear within 12 months of recovery from the acute infection in the majority of patients. • At present, with the longest series of follow-up examinations reported not exceeding 12 months, the development of persistent or progressive fibrosis in at least some individuals cannot yet be excluded. • Residual ground glass opacification may be associated with persisting bronchial dilatation and distortion, and might be termed "fibrotic-like changes" probably consistent with prior organizing pneumonia.

Structured reporting of chest CT in COVID-19 pneumonia: a consensus proposal.

OBJECTIVES: The need of a standardized reporting scheme and language, in imaging of COVID-19 pneumonia, has been welcomed by major scientific societies. The aim of the study was to build the reporting scheme of chest CT in COVID-19 pneumonia. METHODS: A team of experts, of the Italian Society of Medical and Interventional Radiology (SIRM), has been recruited to compose a consensus panel. They used a modified Delphi process to build a reporting scheme and expressed a level of agreement for each section of the report. To measure the internal consistency of the panelist ratings for each section of the report, a quality analysis based on the average inter-item correlation was performed with Cronbach's alpha (Cα) correlation coefficient. RESULTS: The overall mean score of the experts and the sum of score were 3.1 (std.dev. ± 0.11) and 122 in the second round, and improved to 3.75 (std.dev. ± 0.40) and 154 in the third round. The Cronbach's alpha (Cα) correlation coefficient was 0.741 (acceptable) in the second round and improved to 0.789 in the third round. The final report was built in the management of radiology report template (MRRT) and includes n = 4 items in the procedure information, n = 5 items in the clinical information, n = 16 in the findings, and n = 3 in the impression, with overall 28 items. CONCLUSIONS: The proposed structured report could be of help both for expert radiologists and for the less experienced who are faced with the management of these patients. The structured report is conceived as a guideline, to recommend the key items/findings of chest CT in COVID-19 pneumonia.

How to perform lung ultrasound in pregnant women with suspected COVID-19.

Under certain circumstances, such as during the current COVID-19 outbreak, pregnant women can be a target for respiratory infection, and lung examination may be required as part of their clinical evaluation, ideally while avoiding exposure to radiation. We propose a practical approach for obstetricians/gynecologists to perform lung ultrasound examination, discussing potential applications, semiology and practical aspects, which could be of particular importance in emergency situations, such as the current pandemic infection of COVID-19. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.

Percutaneous radiofrequency ablation using internally cooled wet electrodes for the treatment of patients with lung tumors.

OBJECTIVE: To assess the safety and feasibility of computed tomography-guided radiofrequency ablation (CT-guided RFA) in unresectable lung neoplasms, using a new 15G monopolar internally cooled wet electrode. PATIENTS AND METHODS: 15 consecutive patients with lung neoplasms (< 4 cm), both primary and secondary, unsuitable for or refusing surgery, underwent percutaneous CT-guided RFA using a 15G electrode with a 3-cm exposed tip. The prevalence and grade of adverse events and technical success were evaluated, as well as the extension of the ablation zone, the complete response rates, and the time to progression, determined at CT examination performed 1, 6, and 12 months after the procedure. RESULTS: A total of 22 lung neoplasms were treated (mean diameter: 28 mm; range: 20-39 mm). Technical success was obtained in all patients, without major complications or intraprocedural deaths. Mild or moderate pneumothorax was registered in 46.7% of patients, while a perilesional hemorrhage was observed in 5/15 cases. During the follow-up period, a complete response was obtained in 19 out of 22 lesions (86.4%) with three partial response, two of them successfully retreated with the same technique. CONCLUSIONS: Percutaneous RFA using a 15G internally cooled wet electrode is a safe and feasible treatment for unresectable lung neoplasms, with high complete response rates.

Multicenter external validation of two malignancy risk prediction models in patients undergoing 18F-FDG-PET for solitary pulmonary nodule evaluation.

OBJECTIVES: To achieve multicentre external validation of the Herder and Bayesian Inference Malignancy Calculator (BIMC) models. METHODS: Two hundred and fifty-nine solitary pulmonary nodules (SPNs) collected from four major hospitals which underwent 18-FDG-PET characterization were included in this multicentre retrospective study. The Herder model was tested on all available lesions (group A). A subgroup of 180 SPNs (group B) was used to provide unbiased comparison between the Herder and BIMC models. Receiver operating characteristic (ROC) area under the curve (AUC) analysis was performed to assess diagnostic accuracy. Decision analysis was performed by adopting the risk threshold stated in British Thoracic Society (BTS) guidelines. RESULTS: Unbiased comparison performed In Group B showed a ROC AUC for the Herder model of 0.807 (95 % CI 0.742-0.862) and for the BIMC model of 0.822 (95 % CI 0.758-0.875). CONCLUSIONS: Both the Herder and the BIMC models were proven to accurately predict the risk of malignancy when tested on a large multicentre external case series. The BIMC model seems advantageous on the basis of a more favourable decision analysis. KEY POINTS: • The Herder model showed a ROC AUC of 0.807 on 180 SPNs. • The BIMC model showed a ROC AUC of 0.822 on 180 SPNs. • Decision analysis is more favourable to the BIMC model.

Detection of noncalcified pulmonary nodules on low-dose MDCT: comparison of the sensitivity of two CAD systems by using a double reference standard.

PURPOSE: This study compared the sensitivity of two commercial computer-aided detection (CAD) systems in identifying noncalcified pulmonary nodules on low-dose multidetector computed tomography (MDCT) scans by using a double reference standard. MATERIALS AND METHODS: Three chest low-dose MDCT scans of patients who had undergone lung cancer screening were retrospectively analysed using two distinct commercial CAD systems: LungCAD VC10A, Siemens Medical Solutions (CAD1) and LungVCAR, GE Healthcare (CAD2). The exact location of each finding suggested by each system was recorded by an independent reader according to spatial coordinates (x, y, z). Two panels of experienced thoracic radiologists from two different institutions independently established two reference standards (RS1, RS2) by identifying the true positive findings with spatial coordinates without using CAD. Sensitivity of the two CAD systems, defined by lesionlevel analysis, was tested and sensitivities compared. RESULTS: RS1 identified 34 noncalcified pulmonary nodules, whereas RS2 identified 54. The total number of findings detected by the two CAD systems was 684. CAD1 correctly identified 13/34 nodules (sensitivity 38%) for RS1 and 17/54 (sensitivity 30%) for RS2, whereas CAD2 correctly identified 11/34 nodules (sensitivity 35%) for RS1 and 13/54 (sensitivity 23%) for RS2. Comparison between the two CAD systems did not show a statistically significant difference in terms of sensitivity (p<0.05) for both RS1 (p=0.42) and RS2 (p=0.33). CONCLUSIONS: The two commercial CAD systems had similar sensitivity in detecting noncalcified pulmonary nodules on low-dose MDCT of the chest.

Automated volumetry of pulmonary nodules on multidetector CT: influence of slice thickness, reconstruction algorithm and tube current. Preliminary results.

PURPOSE: To evaluate the influence of slice thickness, reconstruction algorithm and tube current (mA) on the performance of a software package in determining the volume of solid pulmonary nodules on multidetector-row computed tomography (MDCT). MATERIALS AND METHODS: A chest phantom containing artificial solid nodules with known volume was imaged with two MDCT scans at 100 and 40 mAs (200 mA and 80 mA, 0.5-s rotation time), respectively. Data were reconstructed with slice thicknesses of 1.25 and 2.5 mm and five different algorithms. The volumes of three nodules (juxtavascular, intraparenchymal, juxtapleural) were calculated using three-dimensional (3D) volumetric software. Differences between estimated and real volume were reported for each nodule and reconstruction set. RESULTS: The software segmented all nodules on 1.25-mm-thick reconstructions, independently from the mAs. It did not segment the juxtapleural nodule on 2.5-mm-thick reconstructions at 40 mAs. Mean values of the differences, which better approximated the real volume of the nodules, were obtained with high-spatial-resolution algorithms on both 100 and 40 mAs images at 1.25-mm slice thickness. CONCLUSIONS: Slice thickness, reconstruction algorithm and tube current can affect the 3D volume measurement of solid nodules. The best performance of the software, on both 100 and 40 mAs images, was observed with a slice thickness of 1.25 mm and high-spatial-resolution algorithms.

Visual score and quantitative CT indices in pulmonary fibrosis: Relationship with physiologic impairment.

PURPOSE: The aim of this study was to assess the accuracy of some computed tomography (CT) quantitative indices (histogram features, ranges of density and one novel volumetric index) in the discrimination between normals and patients affected by lung fibrosis, and to compare their morphologic-functional relationship with the visual score one. MATERIALS AND METHODS: We analysed thin-section CTs and pulmonary function tests (PFTs) of six healthy subjects and 31 patients affected by lung fibrosis, including 17 with a usual interstitial pneumonia pattern (UIP group), and 14 with a predominant pattern of ground-glass opacities without honeycombing (non-UIP group). Presence and extent of various CT findings were assessed by the visual score as well as by CT computer indices. RESULTS: Together with the histogram features, fibrosis ratio (defined as the ratio of nonfibrotic CT lung volume divided by total CT lung volume) contributed to objectively differentiate fibrotic lungs from normal lungs. The range of density 700 to 400 HU showed the greatest degree of correlation with physiologic abnormality in the non-UIP group. In the UIP group, the lone visual score provided prediction of functional impairment. CONCLUSIONS: The visual score is still the main radiological method of quantifying the extent of abnormalities in patients with UIP, whilst the range of density 700 to 400 HU can be helpfully applied in a predominant pattern of ground-glass and reticular opacities without honeycombing.

[Optimization and diagnostic accuracy of computerized tomography with tridimensional spiral technique in the study of craniostenosis]. / Ottimizzazione e accuratezza diagnostica della Tomografia Computerizzata con tecnica spirale tridimensionale nello studio della craniostenosi.

INTRODUCTION: Conventional Computed Tomography (CT) with three-dimensional (3D) reconstructions is considered the most complete and accurate imaging modality to diagnose craniosynostosis. However, the introduction of Spiral CT (SCT) opened new possibilities for 3D studies of the skull in pediatric patients with craniosynostosis. The purpose of our study is two fold: first, to optimize the scanning and imaging parameters to obtain diagnostic images in a single spiral scan; second, to assess the diagnostic accuracy of such images in the identification of normal and abnormal cranial vault sutures. MATERIAL AND METHODS: Seventy-eight pediatric patients (age range: 1-35 months; mean: 11.8 months) with craniosynostosis were submitted to SCT of the head. The images were acquired with the following parameters: 3- and 5-mm nominal slice thickness, 5-6 mm/s table feed (pitch 1-2), 165 mAs and 120 kV. Two different algorithms and increases were used for image reconstructions. A first set of images was reconstructed with 2-mm increases and a soft tissue algorithm: these images were used for brain studies and for 3D reconstructions. A second set of slices was reconstructed with 5-mm increases and a bone algorithm to visualize the sutures of the axial plane. The 3D images were processed with the Shaded Surface Display software with threshold values ranging 120-150 HU. All images were acquired with a single spiral scan lasting less than 30 seconds. Two blinded radiologists analyzed the 3D and the planar images independently to evaluate the course and depth of each cranial suture. The sensitivity, specificity and diagnostic accuracy of both 3D and planar SCT images were evaluated. The frequency of artifacts (the Lego effect, boiled egg, pseudoforamina, movement, and chainsaw artifacts) and their influence on the final diagnosis were studied on 3D SCT images. RESULTS: The diagnostic accuracy rates of 3D SCT images, by suture, were: sagittal 90.7%, metopic 100%, left lamboid 90.9%, right lamboid 93.9%, left coronal 85.7%, right coronal 91.1%. The diagnostic accuracy rates of the axial images, by suture, were: sagittal 90.7%, metopic 95.5%, left lamboid 86.4%, right lamboid 90.9%, left coronal 83.7%, right coronal 91.1%. The interobserver agreement on 3D images was: sagittal 91.1%, metopic 100%, left lamboid 88.9%, right lamboid 91.1%, left coronal 88.9%, right coronal 84.4%. The Lego effect artifact was the most frequent one (82%) and affected image evaluation in 6.3% of cases. CONCLUSIONS: Our results prove that 3D SCT is a very accurate technique for identifying normal and abnormal sutures and presents many advantages over conventional 3D CT in the examination of pediatric patients with craniosynostosis. The quality of 3D SCT images was adequate and the artifacts did not affect the final diagnostic yield significantly.