Computed Tomography Pulmonary Angiography Studies Research Articles

Pulmonary embolism versus pulmonary vasculitis in Hughes-Stovin syndrome: Characteristic computed tomography pulmonary angiographic findings and diagnostic and therapeutic implications. HSS International Study Group

Background and aimHughes-Stovin syndrome (HSS) is a rare systemic vasculitis with widespread venous/arterial thrombosis and pulmonary vasculitis. Distinguishing between pulmonary embolism (PE) and in-situ thrombosis in the early stages of HSS is challenging. The aim of the study is to compare clinical, laboratory, and computed tomography pulmonary angiography (CTPA) characteristics in patients diagnosed with PE versus those with HSS. MethodsThis retrospective study included 40 HSS patients with complete CTPA studies available, previously published by the HSS study group, and 50 patients diagnosed with PE from a single center. Demographics, clinical and laboratory findings, vascular thrombotic events, were compared between both groups. The CTPA findings were reviewed, with emphasis on the distribution, adherence to the mural wall, pulmonary infarction, ground glass opacification, and intra-alveolar hemorrhage. Pulmonary artery aneurysms (PAAs) in HSS were assessed and classified. ResultsThe mean age of HSS patients was 35 ± 12.3 years, in PE 58.4 ± 17 (p < 0.0001). Among PE 39(78 %) had co-morbidities, among HSS none. In contrast to PE, in HSS both major venous and arterial thrombotic events are seen.. Various patterns of PAAs were observed in the HSS group, which were entirely absent in PE. Parenchymal hemorrhage was also more frequent in HSS compared to PE (P < 0.001). ConclusionMajor vascular thrombosis with arterial aneurysms formation are characteristic of HSS. PE typically appear loosely-adherent and mobile whereas “in-situ thrombosis” seen in HSS is tightly-adherent to the mural wall. Mural wall enhancement and PAAs are distinctive pulmonary findings in HSS. The latter findings have significant therapeutic ramifications.

Improved image quality in CT pulmonary angiography using deep learning-based image reconstruction

We investigated the effect of deep learning-based image reconstruction (DLIR) compared to iterative reconstruction on image quality in CT pulmonary angiography (CTPA) for suspected pulmonary embolism (PE). For 220 patients with suspected PE, CTPA studies were reconstructed using filtered back projection (FBP), adaptive statistical iterative reconstruction (ASiR-V 30%, 60% and 90%) and DLIR (low, medium and high strength). Contrast-to-noise ratio (CNR) served as the primary parameter of objective image quality. Subgroup analyses were performed for normal weight, overweight and obese individuals. For patients with confirmed PE (n = 40), we further measured PE-specific CNR. Subjective image quality was assessed independently by two experienced radiologists. CNR was lowest for FBP and enhanced with increasing levels of ASiR-V and, even more with increasing strength of DLIR. High strength DLIR resulted in an additional improvement in CNR by 29–67% compared to ASiR-V 90% (p < 0.05). PE-specific CNR increased by 75% compared to ASiR-V 90% (p < 0.05). Subjective image quality was significantly higher for medium and high strength DLIR compared to all other image reconstructions (p < 0.05). In CT pulmonary angiography, DLIR significantly outperforms iterative reconstruction for increasing objective and subjective image quality. This may allow for further reductions in radiation exposure in suspected PE.

Prospective Evaluation of AI Triage of Pulmonary Emboli on CT Pulmonary Angiograms.

Background Artificial intelligence (AI) algorithms have shown high accuracy for detection of pulmonary embolism (PE) on CT pulmonary angiography (CTPA) studies in academic studies. Purpose To determine whether use of an AI triage system to detect PE on CTPA studies improves radiologist performance or examination and report turnaround times in a clinical setting. Materials and Methods This prospective single-center study included adult participants who underwent CTPA for suspected PE in a clinical practice setting. Consecutive CTPA studies were evaluated in two phases, first by radiologists alone (n = 31) (May 2021 to June 2021) and then by radiologists aided by a commercially available AI triage system (n = 37) (September 2021 to December 2021). Sixty-two percent of radiologists (26 of 42 radiologists) interpreted studies in both phases. The reference standard was determined by an independent re-review of studies by thoracic radiologists and was used to calculate performance metrics. Diagnostic accuracy and turnaround times were compared using Pearson χ2 and Wilcoxon rank sum tests. Results Phases 1 and 2 included 503 studies (participant mean age, 54.0 years ± 17.8 [SD]; 275 female, 228 male) and 1023 studies (participant mean age, 55.1 years ± 17.5; 583 female, 440 male), respectively. In phases 1 and 2, 14.5% (73 of 503) and 15.9% (163 of 1023) of CTPA studies were positive for PE (P = .47). Mean wait time for positive PE studies decreased from 21.5 minutes without AI to 11.3 minutes with AI (P < .001). The accuracy and miss rate, respectively, for radiologist detection of any PE on CTPA studies was 97.6% and 12.3% without AI and 98.6% and 6.1% with AI, which was not significantly different (P = .15 and P = .11, respectively). Conclusion The use of an AI triage system to detect any PE on CTPA studies improved wait times but did not improve radiologist accuracy, miss rate, or examination and report turnaround times. © RSNA, 2023 Supplemental material is available for this article. See also the editorial by Murphy and Tee in this issue.

Efficacy and Impact of a Multimodal Intervention on CT Pulmonary Angiography Ordering Behavior in the Emergency Department

ObjectiveTo evaluate the efficacy of a multimodal intervention in reducing CT pulmonary angiography (CTPA) overutilization in the evaluation of suspected pulmonary embolism in the emergency department (ED). MethodsPrevious mixed-methods analysis of barriers to guideline-concordant CTPA ordering results was used to develop a provider-focused behavioral intervention consisting of a clinical decision support tool and an audit and feedback system at a multisite, tertiary academic network. The primary outcome (guideline concordance) and secondary outcomes (yield and CTPA and D-dimer order rates) were compared using a pre- and postintervention design. ED encounters for adult patients from July 5, 2017, to January 3, 2019, were included. Fisher’s exact tests and statistical process control charts were used to compare the pre- and postintervention groups for each outcome. ResultsOf the 201,912 ED patient visits evaluated, 3,587 included CTPA. Guideline concordance increased significantly after the intervention, from 66.9% to 77.5% (P < .001). CTPA order rate and D-dimer order rate also increased significantly, from 17.1 to 18.4 per 1,000 patients (P = .035) and 30.6 to 37.3 per 1,000 patients (P < .001), respectively. Percent yield showed no significant change (12.3% pre- versus 10.8% postintervention; P = .173). Statistical process control analysis showed sustained special-cause variation in the postintervention period for guideline concordance and D-dimer order rates, temporary special-cause variation for CTPA order rates, and no special-cause variation for percent yield. ConclusionOur success in increasing guideline concordance demonstrates the efficacy of a mixed-methods, human-centered approach to behavior change. Given that neither of the secondary outcomes improved, our results may demonstrate potential limitations to the guidelines directing the ordering of CTPA studies and D-dimer ordering.

Positive rate and quality assessment of CT pulmonary angiography in sickle cell disease: a case‒control study.

Pulmonary complications are common in sickle cell disease (SCD) and can mimic pulmonary embolisms (PEs), leading to potential overuse of computed tomography pulmonary angiography (CTPA). Maximizing the quality of CTPA is essential for its diagnostic accuracy. However, little is known about the positive rate and quality of CTPA in SCD. This retrospective case‒control study aimed to determine the positive rate and quality of CTPA studies performed to rule out PE in SCD (HbSS genotype) patients compared to a control group. Logistic regression analysis was used to identify independent factors associated with suboptimal CTPA studies, defined as a mean enhancement of < 210 HU in the pulmonary artery. The study included 480 patients, consisting of 240 SCD patients and 240 controls. The positive rate of PE was 4.0%, with a similar rate in both SCD patients and the control group (4.2% vs. 3.8%, p = 0.08). However, SCD patients had significantly lower contrast enhancement of the pulmonary artery than the control group (266.1 ± 90.5 HU vs. 342.2 ± 116.1 HU, p < 0.01). Notably, 25.4% of SCD patients had suboptimal scans. The logistic regression model demonstrated that SCD was significantly associated with suboptimal pulmonary arterial contrast enhancement compared to the control group (OR = 4.4; 95% CI: 2.4-8.3). This study revealed a relatively low positive rate of CTPA in both SCD patients and the control group. However, SCD was significantly associated with suboptimal image quality due to inadequate contrast enhancement of the pulmonary artery. Further research is needed to identify measures that can enhance the quality of CTPA studies in SCD patients and to establish a specific imaging protocol for this patient population.

Comparison of Diagnostic Quality and Radiation Dose between Test Bolus and Bolus Tracking protocols for Computed Tomography Pulmonary Angiography (CTPA) among Pregnant Women in Two Tertiary Centres

Introduction: Computed Tomography Pulmonary Angiography (CTPA) among pregnant women is often non-diagnostic and may need the repetition of CTPA. This study aims to compare the test bolus and the bolus tracking protocols for CTPA among pregnant women by analysing the mean contrast enhancement of the pulmonary artery, diagnostic quality and radiation dosage, as well as the outcome of repeated CTPA among pregnant women due to initial non-diagnostic CTPA. Methods: This retrospective study from two tertiary centres included pregnant women who underwent CTPA using test bolus and bolus tracking protocols. CTPA quality, mean pulmonary artery enhancement and dose length product (DLP) were collected and compared between both protocols. The frequency and outcome of CTPA repetition due to suboptimal quality were analysed. Results: Test bolus protocol yields a slightly higher number of diagnostic qualities CTPA than bolus tracking protocol; however not statistically significant. The bolus tracking protocol had significantly better acceptable CTPA quality than the test bolus protocol. Test bolus protocol had significantly lower mean DLP, 220 mGy.cm ± 69, than bolus tracking protocol, 323 mGy.cm ± 34, p-value &lt;0.001. Half of the repeated CTPA did not show significantly better CTPA quality on repetition. Conclusion: No significant difference between test bolus and bolus tracking protocol in CTPA among pregnant women, but the bolus tracking protocol had better overall CTPA quality with higher radiation dose. Repetition of CTPA studies for poor CTPA quality may not always benefit. Hence, we advise weighing the risk and benefits of study repetition.

Editorial

Editorial

Computed Tomography Angiograms Performed for Patients with Suspected Pulmonary Embolism

Background: Pulmonary embolism is a known condition in the emergency department with high morbidity and mortality. Computed tomography pulmonary angiography (CTPA) is a rapid diagnostic tool to detect pulmonary embolism however, the number of positive scans has decreased and the frequency of observed non-embolic findings has increased over time as this tool has been overutilized to provide other alternative diagnoses. Objective: This study aims to estimate the prevalence of pulmonary embolism and non-embolic findings in patients who underwent CT pulmonary angiography for suspected pulmonary embolism. Design and Setting: In this cross-sectional study we retrospectively analyzed consecutive 158 CTPA images and reports performed for suspected pulmonary embolism at a Saudi tertiary care hospital. The non-embolic findings were classified based on their location. Results: The prevalence of pulmonary embolism was 26.6%. No statistically significant difference was found between the diagnosis of pulmonary embolism with respect to gender and age. The prevalence of non-embolic findings among the whole study was 86.7%. Pulmonary findings represented 45.2% of all non-embolic findings followed by pleural findings in 18.3%. Lung opacification and pleural effusion were the most commonly occurring findings. Conclusion: Relative to other studies our center has a reasonable prevalence of CTPA studies being positive for pulmonary embolism however, we encourage balancing the potential benefits and harms by following a well-structured clinical approach to improve the healthcare quality and safety.

A comparison of pulmonary embolism in pediatric and adult patients with acute COVID-19

BackgroundCOVID-19 is associated with pulmonary embolism (PE) in adults. However, the rate of PE in pediatric patients with acute COVID-19 evaluated by CT pulmonary angiography (CTPA) has not been evaluated. ObjectiveDetermine PE rate in pediatric patients with acute COVID-19 and compare to adults. Materials and methodsA retrospective review of CTPA studies, performed between March 2020 and January 2021 on pediatric patients with acute COVID-19, but not MIS-C, was performed. CTPAs performed on an adult cohort of acute COVID-19 patients during April 2020 were reviewed for comparison. Pediatric and chest radiologists independently reviewed CTPAs of pediatric and adult patients, respectively. ResultsOf the 355 acute COVID-19 pediatric patients treated during the study period, 14 (16.6 ± 4.8y, median-18.5y, 64% female) underwent CTPA. Of the 1868 acute COVID-19 adults treated during two weeks in April 2020, 50 (57.2 ± 17.0y, median-57.0y, 42% female) underwent CTPA. The PE rate was 14% in the pediatric group (2 patients) and 18% in the adult group (9 patients) (p = 1.0). Both pediatric patients with PE were obese, over 18y, and had asthma, diabetes mellitus, or hypertension. No child<18y with acute COVID-19 had PE. In the adult cohort, higher alanine-aminotransferase and D-dimer levels were associated with PE (p = 0.04 and p = 0.004, respectively). ConclusionDespite similar PE rates in pediatric and adult patients, PE occurred in acute COVID-19 pediatric patients who were >18y, obese, and had at least 1 comorbidity. Children <18y with COVID-19 did not have PE.

CT pulmonary angiography findings in HIV-infected patients referred for suspected pulmonary thrombo-embolic disease.

BackgroundSouth Africa bares a significant burden of HIV and imaging is commonly performed as part of the workup for respiratory distress.ObjectivesThe aim of this study was to document the prevalence of pulmonary thrombo-embolic disease (PTED) and other findings in HIV-infected patients referred for CT pulmonary angiography (CTPA) for suspected PTED.MethodForty CTPA studies of documented HIV-infected individuals investigated for suspected PTED during a 1-year period were retrieved, anonymised and interpreted by three consultant radiologists. Inter-reader reliability was calculated using Free Marginal multi-rater Kappa.ResultsFourteen of the forty cases (35%) were positive for PTED. In the pulmonary embolism (PE)-positive group, 57.14% had peripheral disease and 42.86% had both peripheral and central disease. Associated findings in the PE-positive cases were pulmonary infarcts (17.5%), mosaic attenuation (17.5%) and linear atelectasis (7.5%). The most common incidental findings were solid pulmonary nodules (52.5%), non-wedge-shaped consolidation (45%), cardiomegaly (52.5%) and enlarged intra-thoracic lymph nodes (52.5%). Thirty per cent of the study population had findings related directly to the presence of PTED, whilst most cases in the study (77.5%) had pulmonary findings unrelated to PTED. In the PE-negative cases, 55% reported emergent findings that warranted immediate or urgent medical attention.ConclusionComputed tomography pulmonary angiography imaging is critical for diagnosing PE. However, further investigation into the judicious application of CTPA in HIV-infected patients with suspected PTED is required, as CTPA findings in most of the cases in this study were unrelated to PE.

The Impact of Pop-Up Clinical Electronic Health Record Decision Tools on Ordering Pulmonary Embolism Studies in the Emergency Department.

Emergency physicians make time-sensitive care decisions for life threatening diagnoses and utilize evidence-based decision rules and testing with high sensitivity to ensure that critical diagnoses are not missed. Current literature suggests that there is over testing for pulmonary embolism in the emergency department. This study aimed to determine whether the addition of a pop-up notification of the Modified Wells Criteria into the workflow would impact the number of total orders for computed tomography pulmonary angiography (CTPA) or the diagnostic yield of those studies. This study was a retrospective observational study comparing CTPA utilization rates and diagnostic yield among physicians at a single academic emergency department in the 1 year prior and 1 year post implementation of an active electronic health recored (EHR) pop-up of Modified Well's scoring when ordering a CTPA. CTPA utilization rates were statistically equivalent, p <0.0001 within a 0.5% equivalence margin, during the pre and post intervention years. The observed difference was 0.1% (95% CI -0.02%, 0.21%). Despite proving equivalence in the rates of CTPA studies ordered, the diagnostic yield, however, was significantly different (p=0.001), 32.35% in the pre-intervention year compared to 41.60% in the post-intervention year. There are many barriers to the implementation of successful EHR alerts. These findings support and validate previous studies that have shown a higher diagnostic yield of CT angiography for pulmonary embolism after implementation of active alerts integrated into the EHR with ordering studies. These tools are effective quality improvement initiatives, and their use should be encouraged.

Pulmonary vasculitis in Hughes-Stovin syndrome (HSS): a reference atlas and computed tomography pulmonary angiography guide\u2014a report by the HSS International Study Group

IntroductionHughes-Stovin syndrome (HSS) is a systemic vasculitis characterized by widespread venous/arterial thrombosis and pulmonary artery aneurysms (PAAs), which is associated with serious morbidity and mortality. All fatalities reported in HSS resulted from unpredictable fatal suffocating hemoptysis. Therefore, it is necessary to recognize pulmonary complications at an early stage of the disease.ObjectivesThe aims of this study are to develop a reference atlas of images depicting the characteristic features of HSS by computed tomography pulmonary angiography (CTPA). To make a guide for physicians by developing a classification of PAAs according to the severity and risk of complications associated with each distinct lesion type.MethodsThe Members of the HSS International Study Group (HSSISG) collected 42 cases, with high-quality CTPA images in one radiology station and made reconstructions from the source images. These detailed CTPA studies were reviewed for final image selection and approved by HSSISG board members. We classified these findings according to the clinical course of the patients.ResultsThis atlas describes the CTPA images that best define the wide spectrum of pulmonary vasculitis observed in HSS. Pulmonary aneurysms were classified into six radiographic patterns: from true stable PAA with adherent in-situ thrombosis to unstable leaking PAA, BAA and/or PAP with loss of aneurysmal wall definition (most prone to rupture), also CTPA images demonstrating right ventricular strain and intracardiac thrombosis.ConclusionThe HSSISG reference atlas is a guide for physicians regarding the CTPA radiological findings, essential for early diagnosis and management of HSS-related pulmonary vasculitis.Key Points• The Hughes-Stovin syndrome (HSS) is a systemic vasculitis characterized by extensive vascular thrombosis and pulmonary artery aneurysms (PAAs) that can lead to significant morbidity and mortality.• All fatalities reported in HSS were related to unpredictable massive hemoptysis; therefore, it is critical to recognize pulmonary complications at an early stage of the disease.• The HSS International Study Group reference atlas classifies pulmonary vasculitis in HSS at 6 different stages of the disease process and defines the different radiological patterns of pulmonary vasculitis notably pulmonary artery aneurysms, as detected by computed tomography pulmonary angiography (CTPA).• The main aim of the classification is to make a guide for physicians about this rare syndrome. Such a scheme has never been reached before since the first description of the syndrome by Hughes and Stovin since 1959. This classification will form the basis for future recommendations regarding diagnosis and treatment of this syndrome.

Performance of an artificial intelligence tool with real-time clinical workflow integration - Detection of intracranial hemorrhage and pulmonary embolism.

Performance of an artificial intelligence tool with real-time clinical workflow integration - Detection of intracranial hemorrhage and pulmonary embolism.

Utilization of serum D-dimer assays prior to computed tomography pulmonary angiography scans in the diagnosis of pulmonary embolism among emergency department physicians: a retrospective observational study

BackgroundA variety of evidence-based algorithms and decision rules using D-Dimer testing have been proposed as instruments to allow physicians to safely rule out a pulmonary embolism (PE) in low-risk patients.ObjectiveTo describe the prevalence of D-Dimer utilization among emergency department (ED) physicians and its impact on positive yields and utilization rates of Computed Tomography Pulmonary Angiography (CTPA).MethodsData was collected on all CTPA studies ordered by ED physicians at three sites during a 2-year period. Using a chi-square test, we compared the diagnostic yield for those patients who had a D-Dimer prior to their CTPA and those who did not. Secondary analysis was done to examine the impact of D-Dimer testing prior to CTPA on individual physician diagnostic yield or utilization rate.ResultsA total of 2811 CTPAs were included in the analysis. Of these, 964 CTPAs (34.3%) were ordered without a D-Dimer, and 343 (18.7%) underwent a CTPA despite a negative D-Dimer. Those CTPAs preceded by a D-Dimer showed no significant difference in positive yields when compared to those ordered without a D-Dimer (9.9% versus 11.3%, p = 0.26). At the individual physician level, no statistically significant relationship was found between D-Dimer utilization and CTPA utilization rate or diagnostic yield.ConclusionThis study provides evidence of suboptimal adherence to guidelines in terms of D-Dimer screening prior to CTPA, and forgoing CTPAs in patients with negative D-Dimers. However, the lack of a positive impact of D-Dimer testing on either CTPA diagnostic yield or utilization rate is indicative of issues relating to the high false-positive rates associated with D-Dimer screening.

Association of computed tomography pulmonary angiography findings with clinical outcome in patients with acute pulmonary embolism

Context: Acute pulmonary embolism (PE) is one of the common and potentially fatal medical emergencies. The short-term mortality of PE ranges from less than 1% in hemodynamically stable patients to over 90% in patients presenting with cardiopulmonary arrest.[1] Patients presenting with PE have a high risk of mortality in the first 30 days.[2],[3],[4],[5] Echocardiography is routinely done in cases of PE for knowing cardiac status but echo being highly operator dependent, Computed Tomography (CT) pulmonary angiography (CTPA) can provide an alternative with lesser operator dependence. The main purpose of this study is to assess the prognostic value of different parameters measured by multi-detector CT pulmonary angiography (CTPA) in evaluating the clinical outcome of acute PE patients.Aim and Objectives: To study association of left atrium (LA) volume, LA volume index, RVV/LVV ratio, IVC reflux, interventricular septal bowing with clinical outcome.Methods and Materials: The prospective study was conducted in the Department of Radio-Diagnosis, Sri Venkateswara Institute of Medical Sciences (SVIMS), Tirupati in the time frame of March 2018 to June 2019. A total of 46 cases that were confirmed to have acute pulmonary thromboembolism on CTPA meeting the study criteria were studied for location of emboli, LA volume, LA volume index, RVV/LVV ratio, IVC reflux, interventricular septal bowing. The parameters were compared with adverse clinical outcomes which were defined as death within 30 days or escalation of therapy, according to the MAPPET-3 ( Management Strategies and Prognosis in Pulmonary Embolism Trial-3) study criteria.[7]Statistical Analysis Used: Chi-square test was used for comparisons of categorical variables, and Student t-test was used for comparisons in the distributions of continuous variables by using IBM SPSS statistics 20. A P value <0.05 was considered significant.Results: Our study included 46 patients belonging to age range of 18 to 83 years with evidence of pulmonary thromboembolism on CTPA study. Out of these, 18 (39%) patients had adverse events, where 17 (37%) patients died within 30 days, and 1 (2%) had a cardiac arrest where he was revived after cardiopulmonary resuscitation within 30 days from diagnosis of acute PE. There was no difference in the distribution of age, sex or other comorbidities between the patients who had adverse events and those who did not. In our study, patients with centrally lodged thrombi showed higher mortality and other adverse events than patients with more peripherally lodged PE (p value = 0.022). There was no evidence of any statistically significant association between the IVC reflux, septal bowing, cardiac volume parameters with adverse events within 30 days of diagnosis of acute PE.Conclusion: In our study, we found the location of thrombus on CTPA to be a significant factor in predicting the adverse outcome. Other parameters like LA volume, LA volume index, RVV/LVV ratio, IVC reflux interventricular septal bowing did not demonstrate a significant relationship with 30-day adverse outcomes. The use of cardiac volumes in predicting the clinical outcome did not show any significant relationship, and this could be due to underlying conditions like hypertension, smoking, systemic diseases. The use of cardiac chamber volumes in predicting clinical outcome needs to be studied on a larger sample size to look for the role of other systemic factors affecting its volume.

Increased Incidence of Acute Pulmonary Embolism in Emergency Department Patients During the COVID‐19 Pandemic

Early detection of acute pulmonary embolism (PE) in patients with SARS-CoV-2 infection is integral to the clinical management of these patients. Many recently published studies have evaluated incidence of PE in hospitalized patients with COVID-191-9 , however there is relatively limited data describing patients with SARS-CoV-2 infection and concomitant diagnosis of acute PE upon initial presentation. Therefore, the purpose of this study is to (i) evaluate the incidence of acute pulmonary embolism (PE) in patients undergoing computed tomography pulmonary angiography (CTPA) in the emergency department (ED) across six hospitals in New York City during the height of the COVID-19 pandemic compared to a non-pandemic period, and (ii) compare the characteristics and early outcomes of patients presenting with PE during the pandemic (n=87) to patients presenting with PE during a non-pandemic period (n=34).

P039: Utilization of serum D-dimer assays and computed tomography pulmonary angiography (CTPA) scans in the diagnosis of pulmonary embolism among emergency department (ED) physicians

Introduction: As the availability of Computed Tomography Pulmonary Angiography (CTPA) to rule out pulmonary embolism (PE) increases, so too does its utilization, and consequent overutilization. A variety of evidence-based algorithms and decision rules using clinical criteria and D-Dimer testing have been proposed as instruments to allow physicians to safely rule out a PE in low-risk patients. However, studies have shown mixed results with respect to both physician uptake of these decision rules and their impact on improving ordering practices among physicians. The objective of this study is to describe the prevalence of D-Dimer utilization among ED physicians and its impact on positive yield rates of CTPAs in a community setting. Methods: Data was collected on all CTPA studies ordered by ED physicians at two very high-volume community hospitals and an affiliated urgent care centre during the 2-year period between January 1, 2016 and December 31, 2017. For each CTPA, we determined if 1) a D-Dimer had been ordered prior to CTPA, if 2) the D-Dimer was positive, and if 3) the CTPA was positive for a PE. Using a chi-square test, we compared the diagnostic yield for those patients who had a D-Dimer prior to their CTPA and those who did not. Results: A total of 2,811 CTPAs were included in the analysis. Of these, 964 CTPAs (34.3%) were ordered without a D-Dimer. Of those 1,847 patients who underwent D-Dimer testing prior to the CTPA, 343 (18.7%) underwent a CTPA despite a negative D-Dimer. When compared as a group, those CTPAs preceded by a D-Dimer showed no significant difference in positive yields when compared to those CTPAs ordered without a prior D-Dimer (9.9% versus 11.3%, p = 0.26). Conclusion: The findings of this study present a complicated picture of the impact of D-Dimer utilization on CTPA ordering patterns. There is evidence of suboptimal uptake of routine D-Dimer ordering, and adherence to guidelines in terms of forgoing CTPAs in low-risk patients with negative D-Dimers. While this study design leaves unanswered the question of how many CTPAs were avoided as a result of a negative D-Dimer, the finding of a similar positive yield among those patients who had a D-Dimer ordered versus those who did not is interesting, and illustrative of the issues arising from the high false-positive rates associated with D-Dimer screening.

Salvage of Suboptimal Enhancement of Pulmonary Artery in Pulmonary CT Angiography Studies: Rapid kVp Switch Dual Energy CT Experience

Background: Multidetector computed tomography (MDCT) angiography is considered as the gold standard imaging modality in the evaluation of acute pulmonary embolism. Optimum vascular enhancement is critical for MDCT studies. The suboptimal opacification in pulmonary artery could be salvaged using low-energy virtual monoenergetic images (VMI) at rapid kVp switch dual energy CT. Objectives: To explore the potential improvement in pulmonary artery opacification and to assess the change in image quality parameters in VMI using fast switch kVp dual energy CT. Patients and Methods: The CT images of 877 patients who were referred with a preliminary diagnosis of pulmonary embolism were reviewed. Sixty patients with suboptimal enhancement (&lt; 200 Hounsfeld Unit [HU]) were involved. Standard images (140 kVp) and VMI from 40 to 120 keV were generated. Attenuation, noise, signal to noise ratio (SNR) and contrast to noise ratio (CNR) were measured in the pulmonary artery. Using VMIs, the best image was determined as the image with the main pulmonary artery opacification greater than 200 HU and image quality ≥ 3. Fifty six studies that met these criteria were considered as salvaged. At this best energy level, quantitative parameters were compared with standard images. Results: The mean attenuation of pulmonary arteries was 169.80 HU in standard images in patients with suboptimal enhancement. The attenuations of VMIs at 40, 45, 50, 55, 60, 65, and 70 keV were significantly higher than standard images (P &lt; 0.001). Similar findings were observed with SNR and CNR. In the salvaged patients, the average increase in mean pulmonary artery attenuation was 62% (from 172.61 ± 23.4 to 280.55 ± 40.7), the average increase in SNR was 38% (from 12.1 ± 5.3 to 16.7 ± 7.1) and the average increase in CNR was 48% (9.2 ± 4.3 to 13.7 ± 6) (P &lt; 0.001). Conclusions: Low keV VMI reconstructions significantly increase pulmonary artery attenuation, CNR and SNR compared to standard image reconstructions. Suboptimal CT studies could be salvaged using low keV VMIs.

Outcomes of Multidetector Computed Tomography Pulmonary Angiography in Pregnant and Postpartum Women With Suspected Pulmonary Embolism.

Verify whether there is a difference in likelihood of developing pulmonary embolism (PE) between pregnant women, nonpregnant women of reproductive age, and postpartum (up to 6 weeks) women, by comparing their outcomes on computed tomography pulmonary angiography (CTPA) done for suspicion of PE. Retrospective cohort study of 1463 CTPA done for suspicion of PE in females of reproductive age (18-40 years), nonpregnant, pregnant (antepartum), and postpartum, from 2 tertiary-care academic hospitals between October 2006 and September 2015. Primary outcome was diagnosis of PE on imaging. Additional assessment was made of technical adequacy of the studies and method of delivery for the postpartum cohort (vaginal vs caesarean birth). Twenty-nine technically nondiagnostic studies were excluded. The effect of any potential variable on PE status was tested using univariate logistic regression. Subgroup analysis was performed after excluding patients with independent risk factors for PE. The rate of CTPA positive for PE was less among pregnant patients compared to early postpartum and nonpregnant women of similar age, 2.9% vs 11.5% and 10.3%, respectively. Pregnancy was associated with statistically significant decreased odds ratio of developing a PE on CTPA, 0.23 (0.09-0.89), P value = .004. After excluding patients with additional independent risk factors for PE, there was no statistically significant odds ratio association between presence of PE on CTPA and pregnancy 0.41 (0.13-1.34), P value = .14. Rate of CTPA positive for PE in pregnant women was lower than in nonpregnant and early postpartum women. Pregnancy was statistically significantly less likely to be associated with positive PE on a CTPA study. The common perception that pregnancy (antepartum state) is associated with an increased risk of PE may require a thorough critical reappraisal.

The relationship between computed tomographic obstruction index and pulmonary vein cross-sectional area in acute pulmonary embolism.

To investigate whether the increased obstruction of the pulmonary arteries was associated with reduced pulmonary vein areas in acute pulmonary embolism (APE). We retrospectively analyzed a consecutive series of computed tomography pulmonary angiography studies of 107 patients with APE and 101 controls without APE between November 2010 and January 2019. The control and patient groups were compared with each other for differences between the mean cross-sectional areas of pulmonary veins. Further analysis was conducted by dividing the patient group into high-risk patients (≥ 20%) and low-risk patients (< 20%) according to the pulmonary arterial obstruction index. The mean cross-sectional area of the pulmonary veins in these two groups was compared. The mean cross-sectional areas of the 4 pulmonary veins at the ostium level (CSAPV) were significantly lower for the patient group (mean: 102.6 mm2) compared with the control group (111.8 mm2) (p < 0.001). CSAPV cutoff value for determining the diagnosis of APE that maximized the accuracy was 109.12 mm2 (AUC = 0.721; 95% CI 0.649-0.794); its sensitivity and specificity were 78.2% and 69.2%, respectively. CSAPV cutoff value for differentiating high-risk APE that maximized the accuracy was 102.6 mm2 (AUC = 0.634; 95% CI 0.525-0.743); its sensitivity and specificity were 61.9% and 53.8%, respectively. There is a negative correlation between the CSAPV and thrombotic material burden in the pulmonary arteries of patients with APE. Hence, the CSAPV can be used as a diagnostic tool in the evaluation of the presence and severity of pulmonary embolism.