CT angiography of pulmonary embolism: diagnostic criteria and causes of misdiagnosis

IL-33/sST2 signaling pathway in pulmonary thromboembolism: A clinical observational study

BACKGROUND

Pulmonary thromboembolism (PTE) is a cardiovascular emergency that can result in mortality. In the interleukin-33 (IL-33) /soluble suppression of tumorigenicity 2 (sST2) signaling pathway, increased sST2 is a cardiovascular risk factor. This study aimed to investigate the effectiveness of biomarkers in the IL-33/sST2 signaling pathway in determining PTE diagnosis, clinical severity, and mortality.

METHOD

This study was conducted as a single-center, prospective, observational study. Patients admitted to the emergency department and diagnosed with PTE constituted the patient group (n = 112), and healthy volunteers with similar sociodemographic characteristics constituted the control group (n = 62). Biomarkers in the IL-33/sST2 signaling pathway were evaluated for diagnosis, clinical severity, and prognosis.

RESULTS

IL-33 was lower in the patient group than in the control group (275.89 versus 403.35 pg/mL), while sST2 levels were higher in the patient group than in the control group (53.16 versus 11.78 ng/mL) (p < 0.001 and p = 0.001; respectively). The AUC of IL-33 to diagnose PTE was 0.656 (95 % CI: 0.580-0.726). The optimal IL-33 cut-off point to diagnose PTE was ≤304.11 pg/mL (56.2 % sensitivity, 79 % specificity). The AUC of sST2 to diagnose PTE was 0.818 (95 % CI: 0.752-0.872). The optimal sST2 cut-off point to diagnose PTE was >14.48 ng/mL (83 % sensitivity, 71 % specificity). IL-33 levels were lower in patients with mortality (169.85 versus 332.04 pg/mL) compared to patients without mortality, whereas sST2 levels were higher in patients with mortality (118.32 versus 28.07 ng/mL) compared to patients without mortality (p > 0.001 for both). The AUC of IL-33 to predict the mortality of PTE was 0.801 (95 % CI: 0.715-0.870). The optimal IL-33 cut-off point to predict the mortality of PTE was ≤212.05 pg/mL (75 % sensitivity, 79.5 % specificity). The AUC of sST2 to predict the mortality of PTE was 0.824 (95 % CI: 0.740-0.889). The optimal sST2 cut-off point to predict the mortality of PTE was >81 ng/mL (95.8 % sensitivity, 78.4 % specificity).

CONCLUSION

In the IL-33/ST2 signaling pathway, decreased IL-33 and increased sST2 are valuable biomarkers for diagnosis and prediction of mortality in patients with PTE.

Performance and clinical utility of an artificial intelligence-enabled tool for pulmonary embolism detection

PURPOSE

Diagnosing pulmonary embolism (PE) is still challenging due to other conditions that can mimic its appearance, leading to incomplete or delayed management and several inter-observer variabilities. This study evaluated the performance and clinical utility of an artificial intelligence (AI)-based application designed to assist clinicians in the detection of PE on CT pulmonary angiography (CTPA).

PATIENTS AND METHODS

CTPAs from 230 US cities acquired on 57 scanner models from 6 different vendors were retrospectively collected. Three US board certified expert radiologists defined the ground truth by majority agreement. The same cases were analyzed by CINA-PE, an AI-driven algorithm capable of detecting and highlighting suspected PE locations. The algorithm's performance at a per-case and per-finding level was evaluated. Furthermore, cases with PE not mentioned in the clinical report but correctly detected by the algorithm were analyzed.

RESULTS

A total of 1204 CTPAs (mean age 62.1 years ± 16.6[SD], 44.4 % female, 14.9 % positive) were included in the study. Per-case sensitivity and specificity were 93.9 % (95%CI: 89.3 %-96.9 %) and 94.8 % (95%CI: 93.3 %-96.1 %), respectively. Per-finding positive predictive value was 89.5 % (95%CI: 86.7 %-91.9 %). Among the 196 positive cases, 29 (15.6 %) were not mentioned in the clinical report. The algorithm detected 22/29 (76 %) of these cases, leading to a reduction in the miss rate from 15.6 % to 3.8 % (7/186).

CONCLUSIONS

The AI-based application may improve diagnostic accuracy in detecting PE and enhance patient outcomes through timely intervention. Integrating AI tools in clinical workflows can reduce missed or delayed diagnoses, and positively impact healthcare delivery and patient care.

A primary pulmonary artery sarcoma masquerading pulmonary embolism: a case report and literature review

BACKGROUND

Primary pulmonary artery sarcoma (PAS) is an extremely rare malignant tumor with a poor prognosis. The clinical manifestations of PAS are diverse, including dyspnea, chest pain, cough, and hemoptysis. The poor prognosis is often due to delayed diagnosis caused by similarity in imaging findings with pulmonary thromboembolism (PTE). These cues of diagnosis include the "wall eclipsing sign", lobulated bulging margins, gadolinium enhancement during MRI imaging, and FDG uptake during PET/CT imaging. However, there are still many misdiagnoses.

CASE PRESENTATION

This article reports a woman of reproductive age presenting with a pulmonary artery mass. The computed tomographic pulmonary angiography and positron emission tomography/computed tomography did not show obvious signs of pulmonary artery sarcoma, however, contrast-enhanced echocardiography showed moderate perfusion, which helped differentiate between pulmonary artery sarcoma and pulmonary artery thrombosis, leading to timely surgical treatment.

CONCLUSIONS

PAS is a rare form of cancer that can occasionally be visually similar to PTE on radiographic images. Early diagnosis of PAS is of vital importance to the prognosis of the patients. There are several visual cues that can help differentiate between the two conditions. Additionally, contrast-enhanced echocardiography provides additional information on tumor perfusion, offering another effective approach for a prompt and accurate diagnosis.

Pixel-level annotated dataset of computed tomography angiography images of acute pulmonary embolism

Pulmonary embolism has a high incidence and mortality, especially if undiagnosed. The examination of choice for diagnosing the disease is computed tomography pulmonary angiography. As many factors can lead to misinterpretations and diagnostic errors, different groups are utilizing deep learning methods to help improve this process. The diagnostic accuracy of these methods tends to increase by augmenting the training dataset. Deep learning methods can potentially benefit from the use of images acquired with devices from different vendors. To the best of our knowledge, we have developed the first public dataset annotated at the pixel and image levels and the first pixel-level annotated dataset to contain examinations performed with equipment from Toshiba and GE. This dataset includes 40 examinations, half performed with each piece of equipment, representing samples from two medical services. We also included measurements related to the cardiac and circulatory consequences of pulmonary embolism. We encourage the use of this dataset to develop, evaluate and compare the performance of new AI algorithms designed to diagnose PE.

Advances for Pulmonary Functional Imaging: Dual-Energy Computed Tomography for Pulmonary Functional Imaging

Dual-energy computed tomography (DECT) can improve the differentiation of material by using two different X-ray energy spectra, and may provide new imaging techniques to diagnostic radiology to overcome the limitations of conventional CT in characterizing tissue. Some techniques have used dual-energy imaging, which mainly includes dual-sourced, rapid kVp switching, dual-layer detectors, and split-filter imaging. In iodine images, images of the lung's perfused blood volume (PBV) based on DECT have been applied in patients with pulmonary embolism to obtain both images of the PE occluding the pulmonary artery and the consequent perfusion defects in the lung's parenchyma. PBV images of the lung also have the potential to indicate the severity of PE, including chronic thromboembolic pulmonary hypertension. Virtual monochromatic imaging can improve the accuracy of diagnosing pulmonary vascular diseases by optimizing kiloelectronvolt settings for various purposes. Iodine images also could provide a new approach in the area of thoracic oncology, for example, for the characterization of pulmonary nodules and mediastinal lymph nodes. DECT-based lung ventilation imaging is also available with noble gases with high atomic numbers, such as xenon, which is similar to iodine. A ventilation map of the lung can be used to image various pulmonary diseases such as chronic obstructive pulmonary disease.

[Expert Opinion Questionnaire About Chest CT Scan Using A Negative Pressure Isolation Strecher in COVID-19 Patients: Image Quality and Infection Risk]

PURPOSE

To survey perceptions of certified physicians on the protocol of chest CT in patients with coronavirus (COVID-19) using a negative pressure isolation stretcher (NPIS).

MATERIALS AND METHODS

This study collected questionnaire responses from a total of 27 certified physicians who had previously performed chest CT with NPIS in COVID-19 isolation hospitals.

RESULTS

The nine surveyed hospitals performed an average of 116 chest CT examinations with NPIS each year. Of these, an average of 24 cases (21%) were contrast chest CT. Of the 9 pulmonologists we surveyed, 5 (56%) agreed that patients who showed abnormalities in serum D-dimer required contrast chest CT. All 9 surveyed radiologists agreed that the image quality of the chest CT with NPIS was sufficient for CT image interpretation regarding pneumonia or pulmonary embolism. Furthermore, in our 9 surveyed infectionologists, 5 (56%) agreed that a risk of secondary infection in the CT room after temporary opening of NPIS could be prevented through a process of disinfection.

CONCLUSION

Experienced physicians considered that the effects of NIPS on chest CT image quality was minimal in patients with COVID-19, and the risk of CT room contamination was easily controlled.

Evaluation of CT angiography obstruction score and pulmonary perfusion defect score using the third-generation dual-source CT for pulmonary embolism

AIM

To investigate the application value of computed tomography (CT) angiography (CTA) obstruction score and pulmonary perfusion defect score on the third-generation dual-source CT for pulmonary embolism and the changes of the right ventricular function.

MATERIALS AND METHODS

The clinical data of 52 patients with pulmonary embolism (PE) confirmed using the third-generation dual-source dual-energy CTPA were analysed retrospectively. These patients were divided into the severe group and non-severe group according to their clinical manifestations. The results of CTPA and dual-energy pulmonary perfusion imaging (DEPI) were recorded by two radiologists for index computation. The ratio of the maximum short-axis diameter of the right ventricle (RV) to that of the left ventricle (LV) was also recorded. The correlation analysis between RV/LV and the mean values of CTA obstruction score and perfusion defect score was performed. Correlation analysis and agreement analysis were performed on the data measured by two radiologists, CTA obstruction score, and pulmonary perfusion defect score.

RESULTS

CTA obstruction score and perfusion defect score measured by the two radiologists had good correlation and agreement. CTA obstruction score, perfusion defect score, and RV/LV were significantly lower in the non-severe group than in the severe PE group. RV/LV had a significant positive correlation with CTA obstruction score and perfusion defect score (p<0.05).

CONCLUSION

The third-generation dual-source dual-energy CT plays a positive role in assessing PE severity and RV function and can provide additional information for the clinical management and treatment of PE patients.

Does the clot burden as assessed by the Mean Bilateral Proximal Extension of the Clot score reflect mortality and adverse outcome after pulmonary embolism?

Background

Rapid diagnosis and risk stratification are important to reduce the risk of adverse clinical events and mortality in acute pulmonary embolism (PE). Although clot burden has not been consistently shown to correlate with disease outcomes, proximally located PE is generally perceived as more severe.

Purpose

To explore the ability of the Mean Bilateral Proximal Extension of the Clot (MBPEC) score to predict mortality and adverse outcome.

Methods

This was a single center retrospective cohort study. 1743 patients with computed tomography pulmonary arteriography (CTPA) verified PE diagnosed between 2005 and 2020 were included. Patients with active malignancy were excluded. The PE clot burden was assessed with MBPEC score: The most proximal extension of PE was scored in each lung from 1 = sub-segmental to 4 = central. The MBPEC score is the score from each lung divided by two and rounded up to nearest integer.

Results

We found inconsistent associations between higher and lower MBPEC scores versus mortality. The all-cause 30-day mortality of 3.9% (95% CI: 3.0-4.9). The PE-related mortality was 2.4% (95% CI: 1.7-3.3). Patients with MBPEC score 1 had higher all-cause mortality compared to patients with MBPEC score 4: Crude Hazard Ratio (cHR) was 2.02 (95% CI: 1.09-3.72). PE-related mortality was lower in patients with MBPEC score 3 compared to score 4: cHR 0.22 (95% CI: 0.05-0.93). Patients with MBPEC score 4 did more often receive systemic thrombolysis compared to patients with MBPEC score 1-3: 3.2% vs. 0.6% (p < .001). Patients with MBPEC score 4 where more often admitted to the intensive care unit: 13% vs. 4.7% (p < .001).

Conclusion

We found no consistent association between the MBPEC score and mortality. Our results therefore indicate that peripheral PE does not necessarily entail a lower morality risk than proximal PE.

Pulmonary CT angiography in the first wave of the COVID-19 pandemic: Comparison between patients with and without infection and with a pre-pandemic series

BACKGROUND AND AIMS

To analyze the diagnostic performance of pulmonary CT angiography and to compare different D-dimer cutoffs for the diagnosis of acute pulmonary embolism in patients with and without SARS-CoV-2 infections.

MATERIALS AND METHODS

We retrospectively analysed all consecutive pulmonary CT angiography studies done for suspected pulmonary embolism in a tertiary hospital during two time periods: the first December 2020 through February 2021 and the second December 2017 through February 2018. D-dimer levels were obtained less than 24 h before the pulmonary CT angiography studies. We analysed the sensitivity, specificity, positive and negative predictive values, area under the receiver operating curve (AUC), and pattern of pulmonary embolism for six different values of D-dimer and the extent of the embolism. During the pandemic period, we also analysed whether the patients had COVID-19.

RESULTS

After excluding 29 poor-quality studies, 492 studies were analysed; 352 of these were done during the pandemic, 180 in patients with COVID-19 and 172 in patients without COVID-19. The absolute frequency of pulmonary embolism diagnosed was higher during the pandemic period (34 cases during the prior period and 85 during the pandemic; 47 of these patients had COVID-19). No significant differences were found in comparing the AUCs for the D-dimer values. The optimum values calculated for the receiver operating characteristic curves differed between patients with COVID-19 (2200 mcg/l), without COVID-19 (4800 mcg/l), and diagnosed in the prepandemic period (3200 mcg/l). Peripheral distribution of the emboli was more common in patients with COVID-19 (72%) than in those without COVID-19 and than in those diagnosed before the pandemic [OR 6.6, 95% CI: 1.5-24.6, p < 0.05 when compared to central distribution].

CONCLUSIONS

The number of CT angiography studies and the number of pulmonary embolisms diagnosed during the pandemic increased due to SARS-CoV-2 infection. The optimal d-dimer cutoffs and the distribution of the pulmonary embolisms differed between the groups of patients with and without COVID-19.

A systemic arterial-pulmonary arterial shunt mimicking a pulmonary embolism on CT pulmonary angiogram

We report the case of a middle-aged woman on a background of severe respiratory disease who presented with hemoptysis. Investigations with CT pulmonary angiogram showed evidence of a large pulmonary arterial filling defect which was initially treated as a pulmonary embolism. However, despite being anticoagulated, she experienced ongoing hemoptysis. Further imaging several days later using aortic phase CT confirmed that the filling defect was a false positive; the artifact was due to retrograde filling from a systemic arterial-pulmonary arterial shunt and anticoagulation was stopped. Although PE is the most common cause of filling defects, this case suggests that in the setting of patients with chronic inflammatory parenchymal pulmonary disease, clinicians should consider alternative causes such as systemic arterial-pulmonary arterial shunts.

Deep Learning-Based Algorithm for Automatic Detection of Pulmonary Embolism in Chest CT Angiograms

Purpose: Since the prompt recognition of acute pulmonary embolism (PE) and the immediate initiation of treatment can significantly reduce the risk of death, we developed a deep learning (DL)-based application aimed to automatically detect PEs on chest computed tomography angiograms (CTAs) and alert radiologists for an urgent interpretation. Convolutional neural networks (CNNs) were used to design the application. The associated algorithm used a hybrid 3D/2D UNet topology. The training phase was performed on datasets adequately distributed in terms of vendors, patient age, slice thickness, and kVp. The objective of this study was to validate the performance of the algorithm in detecting suspected PEs on CTAs. Methods: The validation dataset included 387 anonymized real-world chest CTAs from multiple clinical sites (228 U.S. cities). The data were acquired on 41 different scanner models from five different scanner makers. The ground truth (presence or absence of PE on CTA images) was established by three independent U.S. board-certified radiologists. Results: The algorithm correctly identified 170 of 186 exams positive for PE (sensitivity 91.4% [95% CI: 86.4–95.0%]) and 184 of 201 exams negative for PE (specificity 91.5% [95% CI: 86.8–95.0%]), leading to an accuracy of 91.5%. False negative cases were either chronic PEs or PEs at the limit of subsegmental arteries and close to partial volume effect artifacts. Most of the false positive findings were due to contrast agent-related fluid artifacts, pulmonary veins, and lymph nodes. Conclusions: The DL-based algorithm has a high degree of diagnostic accuracy with balanced sensitivity and specificity for the detection of PE on CTAs.

Auto-Detection of Motion Artifacts on CT Pulmonary Angiograms with a Physician-Trained AI Algorithm

Purpose: Motion-impaired CT images can result in limited or suboptimal diagnostic interpretation (with missed or miscalled lesions) and patient recall. We trained and tested an artificial intelligence (AI) model for identifying substantial motion artifacts on CT pulmonary angiography (CTPA) that have a negative impact on diagnostic interpretation. Methods: With IRB approval and HIPAA compliance, we queried our multicenter radiology report database (mPower, Nuance) for CTPA reports between July 2015 and March 2022 for the following terms: "motion artifacts", "respiratory motion", "technically inadequate", and "suboptimal" or "limited exam". All CTPA reports were from two quaternary (Site A, n = 335; B, n = 259) and a community (C, n = 199) healthcare sites. A thoracic radiologist reviewed CT images of all positive hits for motion artifacts (present or absent) and their severity (no diagnostic effect or major diagnostic impairment). Coronal multiplanar images from 793 CTPA exams were de-identified and exported offline into an AI model building prototype (Cognex Vision Pro, Cognex Corporation) to train an AI model to perform two-class classification ("motion" or "no motion") with data from the three sites (70% training dataset, n = 554; 30% validation dataset, n = 239). Separately, data from Site A and Site C were used for training and validating; testing was performed on the Site B CTPA exams. A five-fold repeated cross-validation was performed to evaluate the model performance with accuracy and receiver operating characteristics analysis (ROC). Results: Among the CTPA images from 793 patients (mean age 63 ± 17 years; 391 males, 402 females), 372 had no motion artifacts, and 421 had substantial motion artifacts. The statistics for the average performance of the AI model after five-fold repeated cross-validation for the two-class classification included 94% sensitivity, 91% specificity, 93% accuracy, and 0.93 area under the ROC curve (AUC: 95% CI 0.89-0.97). Conclusion: The AI model used in this study can successfully identify CTPA exams with diagnostic interpretation limiting motion artifacts in multicenter training and test datasets. Clinical relevance: The AI model used in the study can help alert technologists about the presence of substantial motion artifacts on CTPA, where a repeat image acquisition can help salvage diagnostic information.

Diagnostic pitfalls in computed tomography of the chest

Anatomical variants and imaging artifacts on thoracic computed tomography (CT), when unrecognized as such, can lead to radiological misinterpretation and erroneous diagnosis. This is a concise review of 15 common CT diagnostic pitfalls due to anatomical variants and imaging artifacts which have potential to be misinterpreted as significant pathology, such as neoplasia, infection, traumatic injury, interstitial lung disease, pleural disease, or vascular lesions.

A deep learning approach for automated diagnosis of pulmonary embolism on computed tomographic pulmonary angiography

BACKGROUND

Computed tomographic pulmonary angiography (CTPA) is the diagnostic standard for confirming pulmonary embolism (PE). Since PE is a life-threatening condition, early diagnosis and treatment are critical to avoid PE-associated morbidity and mortality. However, PE remains subject to misdiagnosis.

METHODS

We retrospectively identified 251 CTPAs performed at a tertiary care hospital between January 2018 to January 2021. The scans were classified as positive (n = 55) and negative (n = 196) for PE based on the annotations made by board-certified radiologists. A fully anonymized CT slice served as input for the detection of PE by the 2D segmentation model comprising U-Net architecture with Xception encoder. The diagnostic performance of the model was calculated at both the scan and the slice levels.

RESULTS

The model correctly identified 44 out of 55 scans as positive for PE and 146 out of 196 scans as negative for PE with a sensitivity of 0.80 [95% CI 0.68, 0.89], a specificity of 0.74 [95% CI 0.68, 0.80], and an accuracy of 0.76 [95% CI 0.70, 0.81]. On slice level, 4817 out of 5183 slices were marked as positive for the presence of emboli with a specificity of 0.89 [95% CI 0.88, 0.89], a sensitivity of 0.93 [95% CI 0.92, 0.94], and an accuracy of 0.89 [95% CI 0.887, 0.890]. The model also achieved an AUROC of 0.85 [0.78, 0.90] and 0.94 [0.936, 0.941] at scan level and slice level, respectively for the detection of PE.

CONCLUSION

The development of an AI model and its use for the identification of pulmonary embolism will support healthcare workers by reducing the rate of missed findings and minimizing the time required to screen the scans.

A 52-Year-Old Man With Chest Pain and Dyspnea

CASE PRESENTATION

A 52-year-old man came to the cardiac surgery clinic for pulmonary thromboendarterectomy (PTE) evaluation. He had initially appeared at an outside hospital 1 year earlier, with chest pain and shortness of breath. He had no known chronic conditions. A CT pulmonary angiogram (CTPA) at that time showed a filling defect at the bifurcation of the main pulmonary artery. A transthoracic echocardiogram revealed mild mitral valve regurgitation, but otherwise the results were normal. As he was hemodynamically stable and not hypoxemic, he was treated solely by anticoagulation. Despite adhering to prescribed apixaban, he developed progressive dyspnea and reduced exercise tolerance over the subsequent year. A repeat CTPA performed 12 months after the initial presentation showed a persistent filling defect at the level of the pulmonary artery bifurcation, with a new extension now completely occluding the right main pulmonary artery. A pulmonary angiogram confirmed this complete occlusion, and right heart catheterization revealed precapillary pulmonary hypertension, with a mean pulmonary artery pressure of 50 mm Hg. His anticoagulation was transitioned to enoxaparin for presumed apixaban treatment failure, and an investigation for hypercoagulable conditions was initiated. His lupus anticoagulant test result was positive, but he did not meet the criteria for antiphospholipid syndrome because he was negative for anticardiolipin and β2-glycoprotein antibodies. Assays for antithrombin III, protein C, prothrombin gene, and factor V Leiden mutations produced normal results.

Pulmonary embolism following urological non-oncological surgery: The clinical features, management, and long-term follow-up outcome from a tertiary hospital of China

Objective

To evaluate the clinical features, treatment, and outcomes of pulmonary embolism (PE) after urological non-oncological surgery in a tertiary hospital of China.

Methods

A total of eight patients who suffered from PE after urological non-oncological surgery from 2016 to 2019 were recruited to the study. Clinical data such as symptoms, vital signs, electrocardiogram, echocardiography, and computed tomographic pulmonary arteriography (CTPA) were reviewed. In addition, the management and long-term follow-up outcome of PE were reported. Pulmonary Embolism Quality of Life (PEmb-QoL) questionnaire was applied for five patients to evaluate health-related quality of life after PE.

Results

All patients survived during their hospitalization, and five patients were contacted during follow-up. Five of the eight patients were anticoagulated regularly until the re-examination results of CTPA and lower extremities ultrasound were normal. The period of anticoagulant sustained at least one month for each patient. The long-term follow-up outcomes showed that PE had little impact on the patients' quality of life.

Conclusions

The study demonstrated that the prognosis of PE patients was not as terrible as feared when treated immediately in the ward. Early diagnosis and treatment of PE is vital for prognosis. However, further verifications based on the results of large studies are still needed.

A multitask deep learning approach for pulmonary embolism detection and identification

Pulmonary embolism (PE) is a blood clot traveling to the lungs and is associated with substantial morbidity and mortality. Therefore, rapid diagnoses and treatments are essential. Chest computed tomographic pulmonary angiogram (CTPA) is the gold standard for PE diagnoses. Deep learning can enhance the radiologists’workflow by identifying PE using CTPA, which helps to prioritize important cases and hasten the diagnoses for at-risk patients. In this study, we propose a two-phase multitask learning method that can recognize the presence of PE and its properties such as the position, whether acute or chronic, and the corresponding right-to-left ventricle diameter (RV/LV) ratio, thereby reducing false-negative diagnoses. Trained on the RSNA-STR Pulmonary Embolism CT Dataset, our model demonstrates promising PE detection performances on the hold-out test set with the window-level AUROC achieving 0.93 and the sensitivity being 0.86 with a specificity of 0.85, which is competitive with the radiologists’sensitivities ranging from 0.67 to 0.87 with specificities of 0.89–0.99. In addition, our model provides interpretability through attention weight heatmaps and gradient-weighted class activation mapping (Grad-CAM). Our proposed deep learning model could predict PE existence and other properties of existing cases, which could be applied to practical assistance for PE diagnosis.

Investigation of the need for computed tomography pulmonary angiography in the decision to discontinue treatment for pulmonary thromboembolism

BACKGROUND

Acute pulmonary thromboembolism (PTE) is an important cause of morbidity and mortality that can reduce quality of life due to long-term complications during and after treatment discontinuation.

OBJECTIVES

The aim of this study was to evaluate patients for these complications before discontinuing treatment and determine the necessity of computed tomography pulmonary angiography (CTPA) imaging.

METHODS

This retrospective study included 116 patients over the age of 18 who received anticoagulant treatment for at least 3 months and presented for treatment discontinuation to the Atatürk University Research Hospital Chest Diseases Outpatient Clinic between January 2015 and September 2019.

RESULTS

CTPA performed at treatment discontinuation showed complete thrombus resolution with treatment in 73 patients (62.9%). High pulmonary artery obstruction index (PAOI) at diagnosis was statistically associated with findings of residual or chronic thrombus on CTPA at treatment discontinuation (p = 0.001). In the differentiation of patients with residual/chronic thrombus and those with thrombus resolution, D-dimer at a cut-off value of 474 µg/L had 60% sensitivity and 70% specificity. At a cut-off value of 35.5 mmHg, mean pulmonary artery pressure on echocardiography had sensitivity and specificity of 72% and 77%, respectively. At a cut-off of 23.75, PAOI had sensitivity and specificity of 93% and 69%, respectively.

CONCLUSION

In addition to physical examination findings, D-dimer and echocardiography were guiding parameters in the evaluation of treatment discontinuation and thrombus resolution in patients presenting to the outpatient clinic for discontinuation of treatment for acute PTE. PAOI at diagnosis may be another important guiding parameter in addition to these examinations.

Decreased Pulmonary Artery Bifurcation Angle: A Novel Imaging Criterion for the Diagnosis of Chronic Pulmonary Thromboembolism

Background

Chronic pulmonary thromboembolism (CTEPH) is an unusual complication of acute pulmonary embolism (PE), which is now considered to be treatable. In modern multi-detector scanners, a detailed evaluation of pulmonary artery geometry is currently possible. This study aimed to evaluate the changes in pulmonary artery bifurcation angle (PABA) in the follow-up computed tomography angiography (CTA) of patients with acute PE.

Methods

In this cross-sectional study, the records of two tertiary-level academic hospitals were gathered from 2012 to 2019. Pulmonary artery (PA) bifurcation angle and diameter were measured. Chi square test, independent samples t test, Mann-Whitney, and Pearson's tests were employed to compare data. To evaluate the cut-off point, we utilized receiver operating characteristic (ROC) curve analysis. The accuracy, sensitivity, and specificity of pulmonary artery bifurcation angle changes were calculated. A P value <0.05 was considered to be significant.

Results

Forty-six patients were included in the study. No significant differences were found between patients with and without CTEPH, and PABA in the dimeters of PA trunk, right PA, and left PA in the first CTA images (P values of 0.151, 0.142, 0.891, and 0.483, respectively), while in the secondary CTA, the mean PABA was significantly smaller in patients with CTEPH (P=0.011). In the receiver operating characteristic (ROC) analysis, delta angle revealed an area under the curve of 0.745 and an optimal cutoff of 0, leading to a sensitivity of 64%, specificity of 87%, and accuracy of 76% for diagnosing CTEPH.

Conclusion

We showed a significant decrease in PABA in patients developing CTEPH. This parameter can be easily measured in lung CTA.

Pitfalls in the imaging of pulmonary embolism

Pulmonary embolism (PE) can present with a wide spectrum of clinical symptoms that can overlap considerably with other cardiovascular diseases. To avoid PE related morbidity and mortality, it is vital to identify this disease accurately and in a timely fashion. Several clinical criteria have been developed to standardize the diagnostic approach for patients with suspected PE. Computed tomographic pulmonary angiogram has significantly improved the detection of pulmonary embolism and is considered the imaging modality of choice to diagnose this disease. However, there are several potential pitfalls associated with this modality which can make diagnosis of PE challenging. In this review, we will discuss various pitfalls routinely encountered in the diagnostic work up of patients with suspected PE, approaches to mitigate these pitfalls and incidental pulmonary embolism.

Salvaging low contrast abdominal CT studies using noise-optimised virtual monoenergetic image reconstruction

Objectives

To assess the impact of noise-optimised virtual monoenergetic imaging (VMI+) on image quality and diagnostic evaluation in abdominal dual-energy CT scans with impaired portal-venous contrast.

Methods

We screened 11,746 patients who underwent portal-venous abdominal dual-energy CT for cancer staging between 08/2014 and 11/2019 and identified those with poor portal-venous contrast.Standard linearly-blended image series and VMI+ image series at 40, 50, and 60 keV were reconstructed. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of abdominal organs and vascular structures were calculated. Image noise, image contrast and overall image quality were rated by three radiologists using 5-point Likert scale.

Results

452 of 11,746 (4%) exams were poorly opacified. We excluded 190 cases due to incomplete datasets or multiple exams of the same patient with a final study group of 262. Highest CNR values in all abdominal organs (liver, 6.4 ± 3.0; kidney, 17.4 ± 7.5; spleen, 8.0 ± 3.5) and vascular structures (aorta, 16.0 ± 7.3; intrahepatic vein, 11.3 ± 4.7; portal vein, 15.5 ± 6.7) were measured at 40 keV VMI+ with significantly superior values compared to all other series. In subjective analysis, highest image contrast was seen at 40 keV VMI+ (4.8 ± 0.4), whereas overall image quality peaked at 50 keV VMI+ (4.2 ± 0.5) with significantly superior results compared to all other series (p < 0.001).

Conclusions

Image reconstruction using VMI+ algorithm at 50 keV significantly improves image contrast and image quality of originally poorly opacified abdominal CT scans and reduces the number of non-diagnostic scans.

Advances in knowledge

We validated the impact of VMI+ reconstructions in poorly attenuated DECT studies of the abdomen in a big data cohort.

Pulmoner Tromboemboli Vakalarında Akılda Bulundurulması Gereken Bir Uygulama: Positive Airway Pressure System

Masif pulmoner emboli hayati öneme sahip acil bir pulmoner patolojidir. Erken tanı ve tedavi yaklaşımı mortaliteyi azaltmaktadır. Tedavide trombolitik uygulamalar önemli bir yer almaktadır. Ancak trombolitik tedavi komplikasyonları hekimleri ciddi anlamda zorlamaktadır. Bu olgu serisinde trombolitik tedavi verdiğimiz iki genç masif emboli hastasında gelişen karbondioksit retansiyonunu EzPAP cihazı ile yönetimimizi sunmayı amaçladık. 26 ve 36 yaşında erkek hastalarımız sırasıyla yan ağrısı ve senkop şikayeti ile acilimize başvurdu. Hastalarımızda hipoksi ve taşikardi olması üzerine çekilen PBTA’larında masif PTE tespit edildi. Trombolitik tedavi verilmesine karar verilen hastalarda karbondioksit retansiyonu gelişmesi üzerine non-invazif mekanik ventilasyonun oluşturabileceği barotravmadan çekinildi. Ve bu hastalara EzPAP uygulanmasına karar verildi. Her iki hastada da kısa sürede hipoksi ve karbondioksit retansiyonuna komplikasyonsuz müdahale edildi. Hastaların etyolojik araştırmaları devam etmekte olup nekahatle taburcu edildiler. Sonuç olarak; trombolitik tedavi hızlı ve olumlu sonuçlar sağlarken aynı zamanda kanama gibi ciddi hayatı tehdit edebilen yan etkiler içermektedir. Non- invazif mekanik ventilasyonun barotravmasına bağlı yüz ve solunum yollarında gelişebilecek trombolitiğe bağlı kanamalara karşı alternatif tedavi yöntemi olarak EzPAP kullanılabilir.

CT Angiography for the Detection of Pulmonary Embolism: Role of Tube Voltage and Contrast Injection Rate on Diagnostic Confidence

RATIONALE AND OBJECTIVES

Pulmonary CTA is the current standard method to assess for suspected pulmonary embolism. In some instances, the test results in low confidence interpretations. Our purpose was to compare the diagnostic confidence for three different scan protocols.

MATERIALS AND METHODS

Pulmonary CTA images from 401 patients were retrospectively analyzed. 202 studies used a tube voltage of 120 kVp and a contrast injection rate of 4 cc/s, 99 studies 120 kVp and 5 cc/s, and 100 studies 100 kVp and 4 cc/s. The level of diagnostic confidence was extracted from the final clinical reports. For each study, attenuation of the pulmonary artery, image noise, signal-to-noise ratio (SNR), and radiation dose were compared.

RESULTS

The 120 kVp, 5 cc/s protocol resulted in high diagnostic confidence in 84% of cases, more than with the 120 kVp, 4cc/s (65%) and the 100 kVp protocol (65%, p < 0.004). The 100 kVp protocol had a lower radiation dose, higher image noise, lower SNR, but equal and higher attenuation values of the pulmonary artery.

CONCLUSION

The reduction of tube voltage to 100 kVp at 4 cc/s maintains diagnostic confidence with lower radiation exposure, but does not equal the higher confidence achieved with 120 kVp at 5cc/s.

Diagnosing pulmonary thromboembolism: Concerns and controversies

Pulmonary thromboembolism (PTE) is an important cause of mortality/morbidity even today despite advancement in clinical understanding as well as diagnostic facilities. Clinical diagnosis of PTE is often challenging because of nonspecific sign/symptoms. Adherence to clinical decision-making protocols and appropriate use of diagnostic modalities like computed tomography pulmonary angiography can resolve the diagnostic dilemma in most cases and help in the overall management of PTE. This article deals with various concerns as well as controversies surrounding accurate diagnosis of PTE as on date.

Incidence of pulmonary embolism and impact on mortality in patients with malignant melanoma

PURPOSE

Pulmonary embolism (PE) occurs frequently in patients with malignant melanoma (MM). The aim of this study is to determine the incidence of PE in patients with MM and to assess the clinical characteristics and mortality of MM patients with PE.

MATERIAL AND METHODS

Medical records from 381 MM patients who underwent contrast-enhanced computed tomography were evaluated. Imaging parameters including location of PE and measurements of right heart dysfunction and clinical parameters including D-Dimer levels, local and distant tumor stage and time of death were analyzed.

RESULTS

PE was found in 23/381 (6%) MM patients, whereby 17/23 (74%) were detected incidentally and only 6/23 (26%) were symptomatic. The presence of PE significantly correlated with elevated D-Dimers (p < 0.001), right ventricular dysfunction (p = 0.04), higher local tumor stage (≥T3) (p = 0.05), presence of visceral (p = 0.02) or cerebral metastases (p = 0.03) and increased mortality (p = 0.05). Further, patients with central PE showed an increased mortality compared to peripheral PE (p = 0.03), but no correlation was found between the localization of PE and the occurrence of clinical symptoms (p = 0.36).

CONCLUSION

PE in patients with MM often occurs without clinical symptoms and is indicative for advanced disease and a poorer prognosis.

Quantitative lung perfusion blood volume using dual energy CT-based effective atomic number (Zeff ) imaging

BACKGROUND

Iodine material images (aka iodine basis images) generated from dual energy computed tomography (DECT) have been used to assess potential perfusion defects in the pulmonary parenchyma. However, iodine material images do not provide the needed absolute quantification of the pulmonary blood pool, as materials with effective atomic numbers (Zeff ) different from those of basis materials may also contribute to iodine material images, thus confounding the quantification of perfusion defects.

PURPOSE

(i) To demonstrate the limitations of iodine material images in pulmonary perfusion defect quantification and (ii) to develop and validate a new quantitative biomarker using effective atomic numbers derived from DECT images.

METHODS

The quantitative relationship between the perfusion blood volume (PBV) in pulmonary parenchyma and the effective atomic number (Zeff ) spatial distribution was studied to show that the desired quantitative PBV maps are determined by the spatial maps of Zeff as PB V Z eff ( x ) = a Z eff β ( x ) + b , where a, b, and β are three constants. Namely, quantitative PB V Z eff is determined by Zeff images instead of the iodine basis images. Perfusion maps were generated for four human subjects to demonstrate the differences between conventional iodine material image-based PBV (PBViodine ) derived from two-material decompositions and the proposed PB V Z eff method.

RESULTS

Among patients with pulmonary emboli, the proposed PB V Z eff maps clearly show the perfusion defects while the PBViodine maps do not. Additionally, when there are no perfusion defects present in the derived PBV maps, no pulmonary emboli were diagnosed by an experienced thoracic radiologist.

CONCLUSION

Effective atomic number-based quantitative PBV maps provide the needed sensitive and specific biomarker to quantify pulmonary perfusion defects.

Deep Learning for Pulmonary Embolism Detection: Tackling the RSNA 2020 AI Challenge

In 2020, the Radiological Society of North America and Society of Thoracic Radiology sponsored a machine learning competition to detect and classify pulmonary embolism (PE). This challenge was one of the largest of its kind, with more than 9000 CT pulmonary angiography examinations comprising almost 1.8 million expertly annotated images. More than 700 international teams competed to predict the presence of PE on individual axial images, the overall presence of PE in the CT examination (with chronicity and laterality), and the ratio of right ventricular size to left ventricular size. This article presents a detailed overview of the second-place solution. Source code and models are available at https://github.com/i-pan/kaggle-rsna-pe. Keywords: CT, Neural Networks, Thorax, Pulmonary Arteries, Embolism/Thrombosis, Supervised Learning, Convolutional Neural Networks (CNN), Machine Learning Algorithms © RSNA, 2021.

Radiological features of pulmonary fat embolism in trauma patients: a case series

PURPOSE

Fat embolism syndrome (FES) is a rare complication in trauma patients (usually with long bone fractures) in which migrating medullary fat precipitates multiorgan dysfunction, classically presenting with dyspnoea, petechiae and neurocognitive dysfunction. Although this triad of symptoms is rare, it nonetheless aids diagnosis of pulmonary fat embolism (PuFE). Typical imaging features of PuFE are not established, although increasing use of CT pulmonary angiography (CTPA) in this cohort may provide important diagnostic information. We therefore conducted a case series of FES patients with CTPA imaging at a Level 1 Trauma Centre in Melbourne, Australia.

METHODS

Medical records and various radiological investigations including CTPA of consecutive patients diagnosed clinically with FES between 2006 and 2018, including demographics, injury and their progress during their admission, were reviewed.

RESULTS

Fifteen FES patients with retrievable CTPAs were included (mean age 31.2 years, range 17-69; 12 males [80%]). 93.3% had long bone fractures. CTPA was performed 2.00 ± 1.41 days post-admission. Review of these images showed pulmonary opacity in 14 (93.3%; ground-glass opacities in 9 [64.3%], alveolar opacities in 6 [42.9%]), interlobular septal thickening in 10 (66.7%), and pleural effusions in 7 (46.7%). Filling defects were identified in three (20%) CTPAs, with density measuring - 20HU to + 63HU. Ten patients (66.7%) had neuroimaging performed, with two patients demonstrating imaging findings consistent with cerebral fat emboli.

CONCLUSION

CTPA features of PuFE are variable, with ground-glass parenchymal changes and septal thickening most commonly seen. Filling defects were uncommon.

Deep learning for pulmonary embolism detection on computed tomography pulmonary angiogram: a systematic review and meta-analysis

Computed tomographic pulmonary angiography (CTPA) is the gold standard for pulmonary embolism (PE) diagnosis. However, this diagnosis is susceptible to misdiagnosis. In this study, we aimed to perform a systematic review of current literature applying deep learning for the diagnosis of PE on CTPA. MEDLINE/PUBMED were searched for studies that reported on the accuracy of deep learning algorithms for PE on CTPA. The risk of bias was evaluated using the QUADAS-2 tool. Pooled sensitivity and specificity were calculated. Summary receiver operating characteristic curves were plotted. Seven studies met our inclusion criteria. A total of 36,847 CTPA studies were analyzed. All studies were retrospective. Five studies provided enough data to calculate summary estimates. The pooled sensitivity and specificity for PE detection were 0.88 (95% CI 0.803-0.927) and 0.86 (95% CI 0.756-0.924), respectively. Most studies had a high risk of bias. Our study suggests that deep learning models can detect PE on CTPA with satisfactory sensitivity and an acceptable number of false positive cases. Yet, these are only preliminary retrospective works, indicating the need for future research to determine the clinical impact of automated PE detection on patient care. Deep learning models are gradually being implemented in hospital systems, and it is important to understand the strengths and limitations of these algorithms.

Apixaban or enoxaparin: Which is better for thromboprophylaxis after total hip and total knee arthroplasty in Indian patients?

Both apixaban and enoxaparin are Food and Drug Administration-approved standard therapy for prophylaxis of deep-vein thrombosis; however, the superiority of one over the other is still controversial. With an objective to observe efficacy and safety outcomes of apixaban and enoxaparin in patients undergoing total hip (THA) and knee (TKA) arthroplasty, 96 patients undergoing THA/TKA (October 2018 to August 2019) were randomly allocated into 2 groups; (n = 48) apixaban; and (n = 48) enoxaparin. Efficacy outcomes and safety outcomes were recorded at 2 and 5 weeks post-TKA/THA. Follow-up functional scoring was done at 6 months postoperatively. Apixaban and enoxaparin were found to be equally efficacious in preventing venous thromboembolism; however, apixaban had a better safety profile. The apixaban group had nonsignificant higher tendency for wound discharge, atrial fibrillation and transient ischaemic attack. Enoxaparin had nonsignificant greater tendency for bleeding, wound dehiscence and pulmonary complications. Apixaban is a safe alternative to conventionally used enoxaparin for chemoprophylaxis in patients undergoing THA or TKA.

Radiologic mimics of pulmonary embolism

The diagnosis of pulmonary embolism (PE) is often made more challenging by the presence of diseases that can mimic thromboembolic disease. There is no specific or sensitive constellation of clinical signs or symptoms that can be used to diagnose PE. Ventilation/perfusion scans can have false-positive findings related to mediastinal conditions that can compress the pulmonary arteries, and pulmonary hemorrhage can resemble PE on V/Q scanning with potentially devastating consequences if anticoagulation is started. CT-scan related issues l eading to potential false-positive diagnoses range from inadequate imaging technique, to systemic-pulmonary shunting, to non-thrombotic occlusion of pulmonary arteries by tumor, septic emboli, and emboli of fat, air, and foreign material, as well as vasculitic processes. Careful assessment of the patient and consideration of these potential mimickers is imperative to correct diagnosis of this potentially life-threatening condition.

Pulmonary artery obstruction index, pulmonary artery diameter and right ventricle strain as prognostic CT findings in patient with acute pulmonary embolism

OBJECTIVE

This study was designed to determine predictors of pulmonary hypertension and signs of right heart dysfunction caused by pulmonary embolism (PE) that may lead to early detection of high-risk patients. So the predictive value of pulmonary artery obstruction index (PAOI), measured by pulmonary CT angiography (PCTA) in the acute setting, in predicting the patients susceptible to PE cardiac complications was evaluated. Also two other PCTA indices, pulmonary artery diameter (PAD), and right ventricle (RV) strain, in these patients were investigated and their predictive value for cardiac complications on follow up echocardiography were demonstrated.

MATERIALS AND METHODS

In the study 120 patients with a definite diagnosis of PE were included. The PAOI, PAD and RV strain were measured using PCTA at the time of the initial diagnosis. Transthoracic echocardiography was done 6 months after the diagnosis of PE and RV echocardiographic indices were measured. Pearson correlation was used to investigate correlation between PAOI, PAD, RV strain and signs of right heart dysfunction.

RESULTS

PAOI was strongly correlated with systolic pulmonary artery pressure (SPAP) (r=0.83), RV systolic pressure (r=0.78) and RV wall thickness (r=0.61) in long-term follow up echocardiography. A higher rate of RV dysfunction and RV dilation was detected among the patients with higher PAOI (P<0.001). PAOI≥18 was strongly predictive for development of RV dysfunction. Also developments of pulmonary hypertension, RV systolic hypertension, RV dilation, RV dysfunction, and RV hypertrophy were significantly more common among patients with higher PAD and RV strain (P<0.001).

CONCLUSIONS

PAOI, PAD and RV strain are sensitive and specific PCTA indices that can predict the development of long-term complications such as pulmonary hypertension and right heart dysfunction, at the time of initial PE diagnosis.

Differential diagnoses of acute ground-glass opacity in chest computed tomography: pictorial essay

Ground-glass opacity is a very frequent and unspecified finding in chest computed tomography. Therefore, it admits a wide range of differential diagnoses in the acute context, from viral pneumonias such as influenza virus, coronavirus disease 2019 and cytomegalovirus and even non-infectious lesions, such as vaping, pulmonary infarction, alveolar hemorrhage and pulmonary edema. For this diagnostic differentiation, ground glass must be correlated with other findings in imaging tests, with laboratory tests and with the patients' clinical condition. In the context of a pandemic, it is extremely important to remember the other pathologies with similar findings to coronavirus disease 2019 in the imaging exams.

Intimal Sarcoma of the Great Vessels

Intimal sarcomas of the pulmonary artery and aorta are rare entities with a poor prognosis. In many instances, pulmonary artery sarcomas are misinterpreted as acute or chronic pulmonary thromboembolism, whereas aortic intimal sarcomas are often misdiagnosed as protuberant atherosclerotic disease or intimal thrombus. Discernment of intimal sarcomas from these and other common benign entities is essential for the timely initiation of aggressive therapy. The most useful imaging modalities for assessment of a suspected intimal sarcoma include CT angiography, fluorine 18-fluorodeoxyglucose PET, and MRI. The authors discuss the clinical features, current treatment options, characteristic imaging findings, and underlying pathologic features of intimal sarcomas. The authors emphasize imaging discernment of intimal sarcomas and how their differential diagnosis is informed by knowledge of radiologic-pathologic correlation. The most reliable distinguishing imaging features are also emphasized to improve accurate and timely diagnosis. Online supplemental material is available for this article. ^©RSNA, 2021.

Pulmonary Embolism Versus Mimics on Dual-energy Spectral Computed Tomography: An Algorithmic Approach

Pulmonary embolism is a commonly encountered diagnosis that is traditionally identified on conventional computed tomography angiography. Dual-energy computed tomography (DECT) is a new technology that may aid the initial identification and differential diagnosis of pulmonary embolism. In this review, we present an algorithmic approach for assessing pulmonary embolism on DECT, including acute versus chronic pulmonary embolism, relationship to conventional computed tomography angiography, surrogate for likelihood of hemodynamic significance, and alternative diagnoses for DECT perfusion defects.

Pulmonary Embolism: A Practical Guide for the Busy Clinician

Acute pulmonary embolism (PE) is the third most common acute cardiovascular condition, and its prevalence increases over time. D-dimer has a very high negative predictive value, and if normal levels of D-dimer are detected, the diagnosis of PE is very unlikely. The final diagnosis should be confirmed by computed tomographic scan. However, echocardiography is the most available, bedside, low-cost, diagnostic procedure for patients with PE. Risk stratification is of utmost importance and is mainly based on hemodynamic status of the patient. Patients with PE and hemodynamic stability require further risk assessment, based on clinical symptoms, imaging, and circulating biomarkers.

Improving Contrast Enhancement in Pulmonary CTA: The value of breathing maneuvers

Purpose

To investigate contrast dynamics and artifacts associated with different breathing maneuvers during pulmonary computed tomography angiography (pCTA) in a prospective randomized clinical trial.

Method

Three different breathing maneuvers (inspiration, expiration, Mueller) were randomly assigned to 146 patients receiving pCTA for suspected pulmonary embolism (PE). Contrast enhancement of central and peripheral arteries and imaging quality of lung parenchyma were compared and analyzed. Results were compared by using the analysis of variances (ANOVA) and Kruskal-Wallis-Test.

Results

Mean enhancement in the pulmonary trunk was highest during breath-hold in inspiration (293 HU, range 195-460 HU) compared to Mueller (259 HU, range 136-429 HU, p = 0022) and expiration (267 HU, range 115-376 HU). This was similar for the right pulmonary artery (inspiration 289 HU, range 173-454 HU; Mueller 250 HU, range 119-378 HU; p = 0.007; expiration 257 HU, range 114-366 HU; p = 0.032) and left pulmonary artery (inspiration 280.3 HU, range 170-462 HU; Mueller 245 HU, range 111-371 HU; p = 0.016; expiration 252 HU, range 110-371 HU).Delineation of peripheral arteries was significantly better in inspiration vs Mueller (p = 0.006) and expiration (p = 0.049). Assessment of the lung parenchyma was significantly better in inspiration vs Mueller (p = 0.013) or expiration (p < 0.001).

Conclusions

Resting inspiratory position achieved the highest enhancement levels in central and peripheral pulmonary arteries and best image quality of the pulmonary parenchyma in comparison to other breathing maneuvers. It is necessary to train the maneuver prior to the examination in order to avoid deep inspiration with the risk of suboptimal opacification of the pulmonary arteries.

The Use of Antithrombotics in Critical Illness

Hypercoagulable tendencies may develop in critically ill dogs and to a less known extent, cats. Although the use of antithrombotics is well-established in critically ill people, the indications and approach are far less well-known in dogs and cats. The goal of this article was to review the relevant CURATIVE guidelines, as well as other sources, and to provide recommendations for critically ill patients with directions for future investigation.

Pulmonary Artery Intimal Sarcoma: A Deadly Diagnosis in Disguise

Pulmonary artery intimal sarcoma (PAIS) is a very rare tumour. The prevalence of PAIS is estimated to be between 0.001% and 0.003%, but this may be an underestimation because of potential misdiagnosis due to its similar presentation to that of pulmonary thromboembolism. The prognosis is very poor, with median overall survival between 11 and 18 months. We report a case of a 36-year-old man who presented to our cardiac surgery clinic reporting nonspecific symptoms and was found to have PAIS requiring surgical resection and adjuvant chemotherapy. We outline the radiologic features, pathologic characteristics, surgical approach, and chemotherapy treatment utilized.

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.

Computed tomography angiography for presence of systemic-to-pulmonary artery shunt in transpleural systemic arterial supply

PURPOSE

To investigate radiographic indications and relevant clinical symptoms of retrograde systemic-to-pulmonary artery shunt (RSPAS).

METHODS

Forty-six consecutive patients, with transpleural systemic arterial supply to the lung confirmed by surgery or conventional angiography, underwent chest computed tomography angiography (CTA). Patients with the finding of RSPAS in CT scans were compared with those among whom no retrograde systemic-to-pulmonary artery shunt (NRSPAS) was present. Differences in clinical features, distribution and diameters of systemic supplying arteries between RSPAS and NRSPAS were assessed.

RESULTS

RSPAS in twenty patients (8 left and 12 right) and NRSPAS in 26 patients (14 left and 12 right) were detected at CTA. Hemoptysis and sputum were more frequent in RSPAS (85 % and 60 %, respectively) than in NRSPAS (46 % and 31 %, respectively) (P < 0.05). Single systemic supplying artery was more common in NRSPAS (65 %) while multiple systemic arteries were more frequent in RSPAS (65 %) (P < 0.05). The mean diameter of systemic arteries (6.13 ± 0.57 mm) in RSPAS was significantly larger than that (4.26 ± 0.55 mm) in NRSPAS (P < 0.0001). The anatomic location of systemic arteries crossing the thickened pleura distributed more intensively in apical and costal pleura in RSPAS than that in NRSPAS (P < 0.05). The distribution of systemic arteries adjacent to left or right lung was not statistically significant between RSPAS and NRSPAS.

CONCLUSION

Radiographic features of RSPAS are different from NRSPAS. RSPAS may include enlarged and multiple systemic supplying arteries. And that may suggest greater risk of hemoptysis.

Multiplatform, Non-Breath-Hold Fast Scanning Protocols: Should We Stop Giving Breath-Hold Instructions for Routine Chest CT? [Formula: see text]

OBJECTIVE

We assessed if non-breath-hold (NBH) fast scanning protocol can provide respiratory motion-free images for interpretation of chest computed tomography (CT).

MATERIALS AND METHODS

In our 2-phase project, we first collected baseline data on frequency of respiratory motion artifacts on breath-hold chest CT in 826 adult patients. The second phase included 62 patients (mean age 66 ± 15 years; 21 females, 41 males) who underwent an NBH chest CT on either single-source (n = 32) or dual-source (n = 30) multidetector-row CT scanners. Clinical indications for chest CT, reason for using NBH CT, scanner type, scan duration, and radiation dose (CT dose index volume, dose length product) were recorded. Two thoracic radiologists (R1 and R2) independently graded respiratory motion artifacts (1 = no respiratory motion artifacts with unrestricted evaluation; 2 = minor motion artifacts limited to one lung lobe or less with good diagnostic quality; 3 = moderate motion artifacts limited to 2 to 3 lung lobes but adequate for clinical diagnosis; 4 = poor evaluability or unevaluable from severe motion artifacts; and 5 = limited quality due to other causes like high noise, beam hardening, or metallic artifacts), and recorded pulmonary and mediastinal findings. Descriptive analyses, Cohen κ test for interobserver agreement, and Student t test were performed for statistical analysis.

RESULTS

No NBH chest CT were deemed uninterpretable by either radiologist; most NBH CT (R1-59 of 62, 95%; R2-62 of 62, 100%) had no or minimal motion artifacts. Only 3 of 62 (R1) NBH chest CT had motion artifacts limiting diagnostic evaluation for lungs but not in the mediastinum.

CONCLUSION

Non-breath-hold fast protocol enables acquisition of diagnostic quality chest CT free of respiratory motion artifacts in patients who cannot hold their breath.

Imaging of Chronic Thromboembolic Disease

Acute pulmonary embolism (PE) is a leading cause of cardiovascular morbidity. The most common long-term complication of acute PE is chronic thromboembolic disease, a heterogenous entity which ranges from asymptomatic imaging sequelae to persistent symptoms. Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare disease that can develop in this population and represents the only treatable type of pulmonary hypertension. Recognition of the characteristic findings of chronic pulmonary embolism and CTEPH provides not only diagnostic information, but is also crucial for guiding therapy. The present state-of-the-art review focuses on the multimodality imaging features of chronic pulmonary embolism. Detailed description and illustrations of relevant imaging findings will be demonstrated for ventilation/perfusion (V/Q) scan, CT scan and Dual-Energy CT and MRI and features that distinguish chronic PE from common imaging mimics.

The filling defect of pulmonary artery, an imaging finding what we should know

The most common cause of pulmonary artery filling defects on computed tomography pulmonary angiography or magnetic resonance imaging is pulmonary thromboembolism, but not infrequently, the presentation of this finding lacks specificity. Given that the morbidity and mortality associated with pulmonary thromboembolism is high, proper diagnosis of the condition is essential. Unusual or more rarely encountered etiologies must be considered when clinical manifestations and imaging findings are inconsistent. With this review, our purpose is to describe possible causes of pulmonary arterial filling defects. We aim to provide clinicians with a comprehensive list of differential diagnoses to facilitate a measured approach to the assessment of pulmonary arterial filling defects on computed tomography pulmonary angiography or magnetic resonance imaging.

Multimodal indirect imaging signs of pulmonary embolism

The clinical diagnosis of pulmonary embolism is often difficult, as symptoms range from syncope and chest pain to shock and sudden death. Adding complexity to this picture, some patients with non-diagnosed pulmonary embolism may undergo unenhanced imaging examinations for a number of reasons, including the prevention of contrast medium-related nephrotoxicity, anaphylactic/anaphylactoid reactions and nephrogenic systemic fibrosis, as well as due to patients' refusal or lack of venous access. In this context, radiologists' awareness and recognition of indirect signs are cornerstones in the diagnosis of pulmonary embolism. This article describes the indirect signs of pulmonary embolism on chest X-ray, unenhanced CT, and MRI.

Value of follow-up angiography: additional interventions in patients undergoing catheter-directed thrombolysis for massive and submassive pulmonary embolism

PURPOSE

Catheter-directed thrombolysis (CDT) is an emerging, minimally invasive treatment for patients with massive and submassive pulmonary embolism (PE). The value of follow-up pulmonary angiography for evaluating improvement after CDT is limited by a paucity of large studies assessing its utility and role for additional intervention. The purpose of our study was to assess the role of next-day pulmonary angiography for CDT in patients with acute massive and submassive PE undergoing continuous pulmonary arterial pressure monitoring, and secondarily, determine factors that are correlated with a need for further therapy.

METHODS

Patients who underwent CDT from 2006 to 2016 for massive and submassive PE were reviewed. Patient demographics, comorbidities, preprocedural lab results, noninvasive hemodynamic studies, and technical variables were recorded. Among patients receiving next-day angiography, those requiring further therapy, defined as continued CDT beyond the standard 24 hours (with or without catheter repositioning or exchange) and/or mechanical or suction thrombectomy were contrasted with those not requiring additional therapy to assess for the role of angiography and patient factors that correlate with need for further therapy.

RESULTS

Thirty-two patients underwent CDT for massive (n=14) and submassive (n=18) PE. Eighteen (56.3%) were male, 14 (43.7%) were Caucasian, 18 (56.3%) were African-American, with a mean age of 66.2 years (range, 26-87 years). Of the 27 (84.4%) patients that underwent next-day pulmonary angiography, 16 (59.3%) did not require additional therapy and 11 (40.7%) did require additional therapy. Additional therapy included extended CDT beyond 24 hours (n=4), mechanical/suction thrombectomy (n=5), or both extended CDT and mechanical/suction thrombectomy (n=2). Younger age (50.1 vs. 62.2 years, P = 0.039) was correlated with a need for further therapy. Initial (40.7 vs. 34.8 mmHg, P = 0.248), next-day (31.5 vs. 26.3 mmHg, P = 0.259), and interval change (4.6 vs. 8.0 mmHg, P = 0.669) in pulmonary artery pressures were not statistically significant between patient subsets. Preprocedural right ventricular/left ventricular ratio (RV/LV) also did not differ significantly (1.74 vs. 1.75, P = 0.961). Thirty-day mortality was comparable (2 vs. 1, P = 0.332).

CONCLUSION

Next-day pulmonary angiography is a useful method to identify patients needing additional therapy including extended CDT and/or mechanical or suction thrombectomy in acute PE management. Pulmonary arterial pressures and preprocedural RV/LV ratios were not found to be predicative of those requiring further intervention.