Pulmonary Embolism and Deep Vein Thrombosis in COVID-19: A Systematic Review and Meta-Analysis.

Background The association of pulmonary embolism (PE) with deep vein thrombosis (DVT) in patients with coronavirus disease 2019 (COVID-19) remains unclear, and the diagnostic accuracy of D-dimer tests for PE is unknown. Purpose To conduct meta-analysis of the study-level incidence of PE and DVT and to evaluate the diagnostic accuracy of D-dimer tests for PE from multicenter individual patient data. Materials and Methods A systematic literature search identified studies evaluating the incidence of PE or DVT in patients with COVID-19 from January 1, 2020, to June 15, 2020. These outcomes were pooled using a random-effects model and were further evaluated using metaregression analysis. The diagnostic accuracy of D-dimer tests for PE was estimated on the basis of individual patient data using the summary receiver operating characteristic curve. Results Twenty-seven studies with 3342 patients with COVID-19 were included in the analysis. The pooled incidence rates of PE and DVT were 16.5% (95% CI: 11.6, 22.9; I2 = 0.93) and 14.8% (95% CI: 8.5, 24.5; I2 = 0.94), respectively. PE was more frequently found in patients who were admitted to the intensive care unit (ICU) (24.7% [95% CI: 18.6, 32.1] vs 10.5% [95% CI: 5.1, 20.2] in those not admitted to the ICU) and in studies with universal screening using CT pulmonary angiography. DVT was present in 42.4% of patients with PE. D-dimer tests had an area under the receiver operating characteristic curve of 0.737 for PE, and D-dimer levels of 500 and 1000 µg/L showed high sensitivity (96% and 91%, respectively) but low specificity (10% and 24%, respectively). Conclusion Pulmonary embolism (PE) and deep vein thrombosis (DVT) occurred in 16.5% and 14.8% of patients with coronavirus disease 2019 (COVID-19), respectively, and more than half of patients with PE lacked DVT. The cutoffs of D-dimer levels used to exclude PE in preexisting guidelines seem applicable to patients with COVID-19. © RSNA, 2020 Supplemental material is available for this article. See also the editorial by Woodard in this issue.

Efficacy of Chest CT for COVID-19 Pneumonia Diagnosis in France.

Background The role and performance of chest CT in the diagnosis of the coronavirus disease 2019 (COVID-19) pandemic remains under active investigation. Purpose To evaluate the French national experience using chest CT for COVID-19, results of chest CT and reverse transcription polymerase chain reaction (RT-PCR) assays were compared together and with the final discharge diagnosis used as the reference standard. Materials and Methods A structured CT scan survey (NCT04339686) was sent to 26 hospital radiology departments in France between March 2, 2020, and April 24, 2020. These dates correspond to the peak of the national COVID-19 epidemic. Radiology departments were selected to reflect the estimated geographic prevalence heterogeneities of the epidemic. All symptomatic patients suspected of having COVID-19 pneumonia who underwent both initial chest CT and at least one RT-PCR test within 48 hours were included. The final discharge diagnosis, based on multiparametric items, was recorded. Data for each center were prospectively collected and gathered each week. Test efficacy was determined by using the Mann-Whitney test, Student t test, χ2 test, and Pearson correlation coefficient. P < .05 indicated a significant difference. Results Twenty-six of 26 hospital radiology departments responded to the survey, with 7500 patients entered; 2652 did not have RT-PCR test results or had unknown or excess delay between the RT-PCR test and CT. After exclusions, 4824 patients (mean age, 64 years ± 19 [standard deviation], 2669 male) were included. With final diagnosis as the reference, 2564 of the 4824 patients had COVID-19 (53%). Sensitivity, specificity, negative predictive value, and positive predictive value of chest CT in the diagnosis of COVID-19 were 2319 of 2564 (90%; 95% CI: 89, 91), 2056 of 2260 (91%; 95% CI: 91, 92), 2056 of 2300 (89%; 95% CI: 87, 90), and 2319 of 2524 (92%; 95% CI: 91, 93), respectively. There was no significant difference for chest CT efficacy among the 26 geographically separate sites, each with varying amounts of disease prevalence. Conclusion Use of chest CT for the initial diagnosis and triage of patients suspected of having coronavirus disease 2019 was successful. © RSNA, 2021 Online supplemental material is available for this article.

Acute pulmonary embolism in non-hospitalized COVID-19 patients referred to CTPA by emergency department.

OBJECTIVES: To evaluate the prevalence of acute pulmonary embolism (APE) in non-hospitalized COVID-19 patients referred to CT pulmonary angiography (CTPA) by the emergency department. METHODS: From March 14 to April 6, 2020, 72 non-hospitalized patients referred by the emergency department to CTPA for COVID-19 pneumonia were retrospectively identified. Relevant clinical and laboratory data and CT scan findings were collected for each patient. CTPA scans were reviewed by two radiologists to determinate the presence or absence of APE. Clinical classification, lung involvement of COVID-19 pneumonia, and CT total severity score were compared between APE group and non-APE group. RESULTS: APE was identified in 13 (18%) CTPA scans. The mean age and D-dimer of patients from the APE group were higher in comparison with those from the non-APE group (74.4 vs. 59.6 years, p = 0.008, and 7.29 vs. 3.29 µg/ml, p = 0.011). There was no significant difference between APE and non-APE groups concerning clinical type, COVID-19 pneumonia lung lesions (ground-glass opacity: 85% vs. 97%; consolidation: 69% vs. 68%; crazy paving: 38% vs. 37%; linear reticulation: 69% vs. 78%), CT severity score (6.3 vs. 7.1, p = 0.365), quality of CTPA (1.8 vs. 2.0, p = 0.518), and pleural effusion (38% vs. 19%, p = 0.146). CONCLUSIONS: Non-hospitalized patients with COVID-19 pneumonia referred to CT scan by the emergency departments are at risk of APE. The presence of APE was not limited to severe or critical clinical type of COVID-19 pneumonia. KEY POINTS: • Acute pulmonary embolism was found in 18% of non-hospitalized COVID-19 patients referred by the emergency department to CTPA. Two (15%) patients had main, four (30%) lobar, and seven (55%) segmental acute pulmonary embolism. • Five of 13 (38%) patients with acute pulmonary embolism had a moderate clinical type. • Severity and radiological features of COVID-19 pneumonia showed no significant difference between patients with or without acute pulmonary embolism.

The Impact of Dose Reduction in Quantitative Kinematic CT of Ankle Joints Using a Full Model-Based Iterative Reconstruction Algorithm: A Cadaveric Study.

OBJECTIVE: The objective of our study was to evaluate the quality and reproducibility of semiautomatic measurements of the ankle in low-dose kinematic CT studies using a full model-based iterative reconstruction (MBIR). MATERIALS AND METHODS: Kinematic CT was performed in five cadaveric ankles at three acquisition dose levels: standard dose (1020 mGy × cm), low dose (10% of the standard dose), and ultra-low-dose (1.5% of the standard dose). All images were reconstructed using a full MBIR algorithm. Two semiautomatic measurements (one distance and one angle) were performed by two readers. Registration error was evaluated. The bone aspect on CT and presence of metallic implants were considered in the analysis. The influence of dose on the measurements obtained, reproducibility, and image quality was assessed. RESULTS: With the standard- and low-dose protocols, registration quality was good (registration error, 0.65-4.72%), measurements were similar (p = 0.9), and reproducibility was excellent (intraclass correlation coefficient [ICC] = 0.881). With the ultra-low-dose protocol, the registration quality was poor, yielding measurements significantly different from the other protocols (p < 0.001) and poor reproducibility (ICC = 0.39). In a specimen with normal bone and no metal implant, the registration error was low (0.61-1.01%), measurements were similar (p > 0.5), and reproducibility was excellent (ICC, 0.885-0.996) for the three dose levels tested. CONCLUSION: Full MBIR allows reliable and reproducible measurements in ankle kinematic CT with a low-dose protocol, but an ultra-low-dose protocol may lead to unreliable results.

Evidence-based recommendations for musculoskeletal kinematic 4D-CT studies using wide area-detector scanners: a phantom study with cadaveric correlation.

PROPOSE: To establish evidence-based recommendations for musculoskeletal kinematic 4D-CT on wide area-detector CT. MATERIALS AND METHODS: In order to assess factors influencing image quality in kinematic CT studies, a phantom consisting of a polymethylmethacrylate rotating disk with round wells of different sizes was imaged with various acquisition protocols. Cadaveric acquisitions were performed on the ankle joint during motion in two different axes and at different speeds to allow validation of phantom data. Images were acquired with a 320 detector-row CT scanner and were evaluated by two readers. RESULTS: Motion artefacts were significantly correlated with various parameters (movement axis, distance to centre, rotation speed and volume acquisition speed) (p < 0.0001). The relation between motion artefacts and distance to motion fulcrum was exponential (R2 0.99). Half reconstruction led to a 23 % increase in image noise and a 40 % decrease in motion artefacts. Cadaveric acquisitions confirmed phantom data. Based on these findings, high tube rotation speed and half reconstruction are recommended for kinematic CT. The axis of motion significantly influences image artefacts and should be considered in patient training and evaluation of acquisition protocol suitability. CONCLUSION: This study provides evidence-based recommendations for musculoskeletal kinematic 4D-CT. KEY POINTS: • Motion artefacts can hamper the quality and interpretation of dynamic joint studies • The recommendations presented here help increase image quality • Patient training and preparation can be improved • The artefact-free distance concept helps protocol adaptation and comparison.

Gastric Wall Fatty Infiltration in Patients Without Overt Gastrointestinal Disease.

OBJECTIVE: The purpose of this study was to evaluate the frequency of gastric wall fatty infiltration in patients without overt gastrointestinal disease. MATERIALS AND METHODS: A retrospective study included patients who underwent unenhanced MDCT for renal colic. Two radiologists reviewed all of the images and evaluated for the presence of gastric wall fatty infiltration. The following patient characteristics were also recorded: sex, age, body mass index, total and visceral fat area, and presence of colic or ileal fat halo sign, or hepatic steatosis. A t test and Fisher test were used to compare the results between patients with and patients without gastric wall fatty infiltration. RESULTS: Gastric wall fatty infiltration was present in 25 of 120 (21%) patients in the study. Mean age, weight, body mass index, visceral and total fat areas, proportion of hepatic steatosis, number of men, and frequency of the presence of colic and ileal fat halo signs were significantly higher among patients with gastric wall fatty infiltration than in those without infiltration. CONCLUSION: Gastric wall fatty infiltration was significantly more frequent in men older than 45 years and patients with a body mass index greater than 25. It may represent a normal finding, but its relation to other pathologic conditions related to obesity remains to be explored.

Musculoskeletal Wide-Detector CT Kinematic Evaluation: From Motion to Image.

Kinematic computed tomography (CT) allows identification of fine positional anomalies of bones during motion and under stress and has a potential role in the evaluation of dynamic joint diseases. The increasing width of CT detector systems has made kinematic CT clinically available. Information on acquisition protocol, patient preparation, and the influence of motion on image quality is scarce in the literature despite the obvious importance for the clinical application of this technique. In this article we review the current knowledge on the relation between motion and artifacts, recommendations for the acquisition protocol, as well as current indications for kinematic CT.

Low-dose CT with automatic tube current modulation, adaptive statistical iterative reconstruction, and low tube voltage for the diagnosis of renal colic: impact of body mass index.

OBJECTIVE: The objective of our study was to evaluate the impact of body mass index (BMI) on dose, diagnostic performance, and image quality of a low-dose CT examination for renal colic. MATERIALS AND METHODS: This retrospective study included all patients who underwent a low-dose CT examination for renal colic performed during the year 2012 with automatic tube current modulation, adaptive statistical iterative reconstruction, and a low tube voltage (kV). Three readers independently reviewed all images for the presence of renal colic and evaluated diagnostic confidence and image quality. The results and doses were compared among patients grouped by body mass index (BMI) and between patients with a BMI<25 and those with a BMI≥25. RESULTS: Eighty-six patients were included in the study: 39 patients had a BMI<25 and 47 had a BMI≥25. No statistically significant difference was found between the accuracy rates for the diagnosis of renal colic when the rates of the three independent readers were averaged for both BMI groups (95.7% vs 96.4%, respectively; p=0.83). Image quality and diagnostic confidence scores were significantly better for patients with a BMI≥25 than for patients with a BMI<25 (mean image quality score, 3.7 vs 3.4, p<0.001; mean diagnostic confidence score, 2.8 vs 2.5, p<0.001). The mean radiation dose for patients with a BMI<25 was 2.4 mGy compared with 3.7 mGy for patients with a BMI≥25 (p<0.001). CONCLUSION: The diagnostic performance of our low-dose CT protocol for renal colic was excellent for all patients, and image quality and diagnostic confidence were significantly better for patients with a BMI≥25. However, our protocol also required exposure to a greater dose of radiation for these overweight and obese patients.

CT image quality improvement using Adaptive Iterative Dose Reduction with wide-volume acquisition on 320-detector CT.

OBJECTIVES: To evaluate the impact of Adaptive Iterative Dose Reduction (AIDR) on image quality and radiation dose in phantom and patient studies. METHODS: A phantom was examined in volumetric mode on a 320-detector CT at different tube currents from 25 to 550 mAs. CT images were reconstructed with AIDR and with Filtered Back Projection (FBP) reconstruction algorithm. Image noise, Contrast-to-Noise Ratio (CNR), Signal-to-Noise Ratio (SNR) and spatial resolution were compared between FBP and AIDR images. AIDR was then tested on 15 CT examinations of the lumbar spine in a prospective study. Again, FBP and AIDR images were compared. Image noise and SNR were analysed using a Wilcoxon signed-rank test. RESULTS: In the phantom, spatial resolution assessment showed no significant difference between FBP and AIDR reconstructions. Image noise was lower with AIDR than with FBP images with a mean reduction of 40%. CNR and SNR were also improved with AIDR. In patients, quantitative and subjective evaluation showed that image noise was significantly lower with AIDR than with FBP. SNR was also greater with AIDR than with FBP. CONCLUSION: Compared to traditional FBP reconstruction techniques, AIDR significantly improves image quality and has the potential to decrease radiation dose. KEY POINTS: This study showed that Adaptive Iterative Dose Reduction (AIDR) reduces image noise. In a phantom image noise was reduced without altering spatial resolution. In patients AIDR reduced the image noise in lumbar spine CT. AIDR can potentially reduce the dose for lumbar spine CT by 52%.

Optimizing z-axis coverage of abdominal CT scans of the urinary tract: a proposed alternative proximal landmark for acquisition planning.

OBJECTIVE: To evaluate an alternative method to reduce the acquisition coverage of urinary tract CT. METHODS: This retrospective study included 365 abdominopelvic CT studies. Three radiographers simulated shortened acquisition coverages using three methods to determine the upper limit of the acquisition: Method 1 used the renal contours; Method 2 used the inferior margin of the 10th thoracic vertebra; and Method 3 used the point of intersection of the left diaphragmatic dome and the anterior margin of the vertebral bodies. Reductions in acquisition coverage and number of CT scans with a portion of the kidney excluded from the simulated reduced acquisition were compared between the three methods. RESULTS: The mean ± standard deviation reduction of acquisition coverage for the three readers with Methods 1, 2 and 3 were 20.5 ± 4.8, 15.1 ± 6.5 and 18.2 ± 5.3%, respectively. Compared with Method 2, Method 3 allowed a mean scan length reduction of 3.6%. The proportions of CT scans with a portion of the kidney excluded from the simulated reduced acquisition with Methods 1, 2 and 3 and averaged over the three readers were 6.7, 0.7 and 1.4%, respectively, with no significant difference between Methods 2 and 3. Interreader and intrareader agreements were excellent with all methods, but interclass correlation coefficients were higher with Method 3. CONCLUSION: The method using the renal contours should not be used owing to its high proportion of kidneys with a portion excluded from the acquisition. Using the intersection of the left diaphragmatic dome and the anterior margin of the vertebral bodies for proximal landmark for urinary tract CT represents a new alternative method with a better reduction of scan length compared with the method using the inferior margin of T10 and with no significant increase in the number of kidneys with a portion excluded from the reduced acquisition. Advances in knowledge: A new method using the point of intersection of the left diaphragmatic dome and the anterior border of the vertebral bodies on the lateral scout radiograph is introduced to reduce the z-axis coverage of urinary tract CT scans.

Musculoskeletal wide detector CT: principles, techniques and applications in clinical practice and research.

A progressive increase in the detector width in CT scanners has meant that advanced techniques such as dynamic, perfusion and dual-energy CT are now at the radiologist's disposal. Although these techniques may be important for the diagnosis of various musculoskeletal diseases, data acquisition and interpretation can be challenging. This article offers a practical guide for the use of these tools including acquisition protocol, post-processing options and data interpretation based on 7 years of clinical experience in a tertiary university hospital.