Computed Tomography Pulmonary Angiography Scans Research Articles

No added value of the age‐adjusted D‐dimer cut‐off to the YEARS algorithm in patients with suspected pulmonary embolism

Background The YEARS algorithm was designed to simplify the diagnostic work-up of pulmonary embolism (PE) and to reduce the number of necessary computed tomography pulmonary angiography (CTPA) scans. An alternative strategy to reduce the number of CTPAs is the age-adjusted D-dimer cut-off (ADJUST) in patients aged 50years or older. We aimed to investigate whether a combination of both diagnostic strategies might save additional CTPAs. Methods The YEARS algorithm consists of three items (clinical signs of deep venous thrombosis, hemoptysis, 'PE most likely diagnosis') with simultaneous D-dimer testing using a pre-test dependent threshold. We performed a post hoc analysis in 3465 patients managed according to YEARS to compare the number of patients managed without CTPA scans and associated diagnostic failures in hypothetical scenarios with different YEARS-ADJUST combinations. Results Following the YEARS algorithm, 1651 patients (48%) were managed without CTPA; PE was diagnosed in 456 (13%) patients at baseline and 18 patients with initial normal testing suffered venous thromboembolism (VTE) during 3-month follow-up (failure rate 0.61%; 95% confidence interval [CI], 0.36-0.96). If ADJUST had been fully integrated in YEARS, 1627 patients (47%) would have been managed without CTPA (absolute decrease of 0.69%; 95% CI -1.7 to 3.0), at cost of four additional missed PE diagnoses at baseline, for a projected 3-month VTE failure rate of 0.75% (95% CI, 0.49-1.13). None of the other studied scenarios showed relevant improvements in efficiency as well, but all led to more missed diagnoses. Conclusion In our cohort, there was no added value of implementing ADJUST in the YEARS algorithm.

"Pulmonary Vein Sign" for Pulmonary Embolism Diagnosis in Computed Tomography Angiography.

Considering that pulmonary arterial obstruction decreases venous flow, we hypothesized that filling defects in pulmonary veins can be identified in areas adjacent to pulmonary embolism (PE). This sign was named the "pulmonary vein sign" (PVS), and we evaluated its prevalence and performance for PE diagnosis in computed tomography pulmonary angiography (CTPA). This retrospective study enrolled consecutive patients with clinical suspicion of PE who underwent CTPA scan. The PVS was defined by the following criteria: (a) presence of a homogeneous filling defect of at least 2cm in a pulmonary vein; (b) attenuation of the left atrium>160 Hounsfield units. Using the cases that presented PE on CTPA as reference, sensitivity, specificity, and positive and negative predictive values were calculated for PVS. In total, 119 patients (73 female; mean age, 62years) were included in this study. PE was diagnosed in 44 (35.8%) patients. The PVS was present in 16 out of 44 patients with PE. Sensitivity was 36.36% (95% confidence interval (CI) 22.83-52.26%); specificity, 98.67% (95% CI 91.79-99.93%); positive predictive value, 94.12% (95% CI 69.24-99.69%); negative predictive value, 72.55% (95% CI 62.67-80.70%). The Kappa index for the PVS was good (0.801; 95% CI 0.645-0.957). PVS was correlated with lobar and segmental pulmonary embolism (p<0.01). Despite a low sensitivity, presence of the pulmonary vein sign was highly specific for PE, with a good agreement between readers. This sign could contribute for PE diagnosis on CTPA studies.

The prevalence and radiological findings of pulmonary embolism in HIV-positive patients referred for computed tomography pulmonary angiography in the Western Cape of South Africa.

SummaryAim:To provide imaging data and report associations between human immunodeficiency virus (HIV), tuberculosis (TB) and pulmonary embolism (PE) in a South African population that underwent computed tomography pulmonary angiography (CTPA) for suspected PE.Methods:A validated Qanadli severity scoring system for PE was used for 164 CTPA scans, and parenchymal, pleural and cardiovascular complications were reported. Serological confirmation of HIV testing and microbiological confirmation of TB were recorded.Results:Prevalence of PE in the CTPA population was 26% (95% CI: 19.67–33.65%). HIV-positive prevalence in patients with PE was 67% (95% CI: 48.17–82.04%), however it was not statistically significantly different when compared with the patients without PE (p = 1). HIV-positive patients had more extensive partial thrombus in the right middle lobe (p = 0.045), but no other differences when compared with HIV-negative patients. TB prevalence in patients with PE was 57% (95% CI: 34.49–76.81%). This was statistically significantly different when compared with the patients without PE (p = 0.073 at the 10% level). Prevalence of TB co-morbidity in the HIV-positive group with proven PE was 71% (95% CI: 41.90– 91.61%), however there was no statistically significant difference in comparison with the HIV-negative patients with TB and PE (p= 0.305).Conclusion:The high number of patients presenting for CTPA who were HIV infected (and also infected with TB) highlights that PE evaluation should include severity/extent of the disease, as these patients may have more severe disease in specific lung lobes. The use of a validated scoring system, such as the Qanadli score, when reporting PE may have a profound effect on patient risk stratification, management and prognosis and would also provide a system for collecting larger volumes of data for analysis.

Diagnostic yield of CT pulmonary angiography in the diagnosis of pulmonary embolism: A single center experience

The purpose of this study was to investigate the clinical application of computed tomography pulmonary angiography (CTPA) in patients with suspected pulmonary embolism (PE) based on a single-center experience. Medical records and radiological reports of 450 patients (272 men and 178 women; mean age 58.9 years; range 14-95 years) with suspected PE who underwent CTPA and triple rule-out CT scans over a period of 6 months were retrospectively reviewed. Prevalence of PE was analysed to determine the diagnostic yield of CT in these two scanning protocols. Of 450 patient records, the positive rate of PE was 30.7%. Triple rule-out CT protocol was performed in 75 out of 450 patients with the diagnostic yield of PE being only 8% (6 out of 75 patients had PE), which is significantly lower than the 35.2% as shown in the CTPA group (132 out of 375 had PE). Mean effective dose was 2.8±2.6 mSv and 13.5±7.8 mSv for CTPA and triple rule-out protocols, respectively. This study shows that CTPA has high diagnostic yield in the diagnosis of pulmonary embolism, hence justifying its appropriateness as a routine imaging modality. However, triple rule-out CT is not recommended due to the low diagnostic yield. Further reduction in radiation and contrast medium doses is necessary.

Automated iterative neutrosophic lung segmentation for image analysis in thoracic computed tomography.

Lung segmentation is a fundamental step in many image analysis applications for lung diseases and abnormalities in thoracic computed tomography (CT). The authors have previously developed a lung segmentation method based on expectation-maximization (EM) analysis and morphological operations (EMM) for our computer-aided detection (CAD) system for pulmonary embolism (PE) in CT pulmonary angiography (CTPA). However, due to the large variations in pathology that may be present in thoracic CT images, it is difficult to extract the lung regions accurately, especially when the lung parenchyma contains extensive lung diseases. The purpose of this study is to develop a new method that can provide accurate lung segmentation, including those affected by lung diseases. An iterative neutrosophic lung segmentation (INLS) method was developed to improve the EMM segmentation utilizing the anatomic features of the ribs and lungs. The initial lung regions (ILRs) were extracted using our previously developed EMM method, in which the ribs were extracted using 3D hierarchical EM segmentation and the ribcage was constructed using morphological operations. Based on the anatomic features of ribs and lungs, the initial EMM segmentation was refined using INLS to obtain the final lung regions. In the INLS method, the anatomic features were mapped into a neutrosophic domain, and the neutrosophic operation was performed iteratively to refine the ILRs. With IRB approval, 5 and 58 CTPA scans were collected retrospectively and used as training and test sets, of which 2 and 34 cases had lung diseases, respectively. The lung regions manually outlined by an experienced thoracic radiologist were used as reference standard for performance evaluation of the automated lung segmentation. The percentage overlap area (POA), the Hausdorff distance (Hdist), and the average distance (AvgDist) of the lung boundaries relative to the reference standard were used as performance metrics. The proposed method achieved larger POAs and smaller distance errors than the EMM method. For the 58 test cases, the average POA, Hdist, and AvgDist were improved from 85.4±18.4%, 22.6±29.4 mm, and 3.5±5.4 mm using EMM to 91.2±6.7%, 16.0±11.3 mm, and 2.5±1.0 mm using INLS, respectively. The improvements were statistically significant (p<0.05). To evaluate the accuracy of the INLS method in the identification of the lung boundaries affected by lung diseases, the authors separately analyzed the performance of the proposed method on the cases with versus without the lung diseases. The results showed that the cases without lung diseases were segmented more accurately than the cases with lung diseases by both the EMM and the INLS methods, but the INLS method achieved better performance than the EMM method in both cases. The new INLS method utilizing the anatomic features of the rib and lung significantly improved the accuracy of lung segmentation, especially for the cases affected by lung diseases. Improvement in lung segmentation will facilitate many image analysis tasks and CAD applications for lung diseases and abnormalities in thoracic CT, including automated PE detection.

Clot resolution after 3 weeks of anticoagulant treatment for pulmonary embolism: comparison of computed tomography and perfusion scintigraphy

Little is known about the natural history of clot resolution in the initial weeks of anticoagulant therapy in patients with acute pulmonary embolism (PE). Clot resolution of acute PE was assessed with either computed tomography pulmonary angiography scan (CT-scan) or perfusion scintigraphy scan (Q-scan) after 3weeks of treatment. This was a predefined safety analysis of the Einstein PE study, including PE patients, randomized to either enoxaparin with vitaminK antagonist (VKA) or rivaroxaban. A similar scan as at baseline was repeated after 3weeks. The percentage of vascular obstruction (PVO) was calculated on the basis of a weighted semiquantitative estimation of obstruction. Clot resolution was assessed blindly by calculating the relative change after 3weeks. PE was diagnosed in 264 patients with CT-scan and in 83 with Q-scan. Baseline characteristics were similar. At baseline, the mean PVO assessed with CT-scan (PVO-CT) and the mean PVO assessed with Q-scan (PVO-Q) were both 21% (standard deviation [SD]13%) (P=0.9). The mean relative decrease in PVO was 71% (SD33%) for PVO-CT, and 62% (SD36%) for PVO-Q (P=0.02); complete resolution was observed in 44% (116/264; 95% confidence interval [CI]38-50%) and 31% (26/83; 95%CI22-42%) with CT-scan and Q-scan, respectively (P=0.04). No difference in clot resolution between enoxaparin/VKA and rivaroxaban was found. In patients with acute PE, only 3weeks of anticoagulant treatment leads to complete clot resolution in a considerable proportion of patients, and normalization is more often observed with CT-scan than with Q-scan.

Efficacy of ‘breath holding at ease’ during CT pulmonary angiography in the improvement of contrast enhancement in pulmonary arteries

The aim of this study is to assess whether breath-hold at ease by patients during the CT pulmonary angiography (CTPA) will improve contrast enhancement in pulmonary arteries. Retrospective review was conducted on 51 consecutive CTPA studies undertaken in the traditional method of patients taking deep inspiration and breath-hold immediately prior to scanning, and subsequently 75 consecutive CTPA studies with patients breathing-holding at ease immediately prior to and during the scanning. Attenuation values in pulmonary arteries of different anatomical levels in both groups were measured in Hounsfield unit (HU). Results were compared between the two groups. The mean attenuation value in pulmonary arteries including pulmonary trunk, main and proximal pulmonary arteries calculated in HU in the 'deep inspiration and breath-hold' group was 327 HU (95% confidence interval: 315 to 339 HU). The mean attenuation value in pulmonary arteries in the 'breath hold at ease' group was calculated to be 390 HU (95% confidence interval: 381 to 399 HU); that is, an overall 17.95% increase (P-value < 0.0001) in attenuation value in this group. By asking patients to breath-hold at ease instead of taking deep inspiration and breath hold prior to CTPA scan can effectively improve contrast enhancement in pulmonary arteries, therefore producing a higher-quality CT pulmonary angiography scan.

P143 A Retrospective Study of Echocardiography and Follow-Up After Acute Pulmonary Embolism – Are We Missing Chronic Thromboembolic Pulmonary Hypertension?

IntroductionPulmonary Hypertension (PH) is defined as raised Pulmonary Arterial Systolic Pressure ≥25mmHg at rest on Right Heart Catheterisation.1 Chronic Thromoboembolic Pulmonary Hypertension (CTEPH) is a recognised complication of pulmonary embolism...

Thrombus load and acute right ventricular failure in pulmonary embolism: correlation and demonstration of a “tipping point” on CT pulmonary angiography

The aim of this study was to determine the correlation between increasing pulmonary embolism thrombus load and right ventricular (RV) dilatation as demonstrated by CT pulmonary angiography (CTPA) and to assess the thrombus load threshold which indicates impending RV decompensation. 2425 consecutive CTPAs were retrospectively analysed. Thrombus load using a modified Miller score (MMS), RV to left ventricular (RV:LV) ratio, presence of septal shift, and pulmonary artery and aorta size were analysed in 504 positive CTPA scans and a representative cohort of 100 negative scans. Results were correlated using non-parametric analysis (two-tailed t-test or χ(2) test) and Pearson's rank correlation. Increasing thrombus load correlated with a higher RV:LV ratio, with a statistically significant difference in RV:LV ratios between the negative and positive pulmonary embolism (PE) cohorts. Larger thrombus loads (MMS ≥12 vs MMS <12) were strongly correlated with RV strain (mean RV:LV ratio, 1.323 vs 0.930; p<0.0001). Smaller thrombus loads had no significant influence on RV strain. Septal shift was also more likely with an MMS of ≥12, as was an increase in pulmonary artery diameter (r=0.221, p<0.001). With increasing thrombus load in PE, there is CTPA evidence of RV decompensation with an MMS threshold of 12. This suggests a "tipping point" beyond which RV decompensation is more likely to occur. This is the first study to describe this tipping point between a thrombus load of MMS >12 and an increase in RV:LV ratio. This finding may help to improve risk stratification in patients with acute PE diagnosed by CTPA.

A guide to foetal dose minimisation in computed tomography pulmonary angiography of the pregnant patient

AbstractPurpose: For pregnant patients the imaging choice between computed tomography pulmonary angiography (CTPA) and ventilation‐perfusion scintigraphy (VQ) in the investigation of pulmonary emboli (PE) is clouded by perceptions of radiation dose levels reaching the foetus. There is also uncertainty amongst medical professionals regarding the subsequent need to implement measures directed at reducing this dose. The aim of this article is to clarify the various theories surrounding CTPA of the pregnant patient and provide radiographers and medical professionals with a clear, concise understanding of how to reduce the radiation dose to the foetus during CTPA scanning. Methods: In a review of the current data surrounding foetal doses in relation to CTPA this paper is able to compare CTPA and VQ foetal doses. By collating information from the limited number of studies performed on foetal dose reduction techniques for CTPA a number of conclusions were drawn in order to formulate a scanning guide for radiographers. Results: Current opinion suggests that the benefits of CTPA outweigh those of VQ with respect to foetal radiation dose. Survey evidence suggests that often no foetal dose reduction strategies are implemented when scanning a pregnant woman for CTPA. Recently published studies have shown that simply by altering the CTPA scanning parameters, such as kVp, mAs, and scan length, using lead protection on the abdomen, and even ingesting barium sulphate solution the dose received by the foetus can be reduced by at least half. Conclusion: Since the stochastic effects of radiation are relatively unknown it is prudent to use any practical techniques aimed at reducing the foetal dose during a CTPA study. Since most of the measures investigated are practical and cause little patient discomfort the authors suggest that consideration should be given to integrating these modifications into current routine scanning protocols.

Chinese multi-center study of lung scintigraphy and CT pulmonary angiography for the diagnosis of pulmonary embolism

To evaluate diagnostic value of the PISA-PED and PIOPED II criteria for lung scintigraphy and compare it with CT pulmonary angiography (CTPA) for the detection of pulmonary embolism (PE). Five hundred and forty-four consecutive patients with suspected PE were enrolled. All patients underwent lung ventilation/perfusion (V/P) scan, chest radiography, and CTPA. Two readers used the PIOPED II criteria, and 2 used the PISA-PED criteria for the interpretation of lung scintigraphy. CTPA scans were interpreted by two experienced radiologists. Lung scintigraphy and CTPA were categorized as PE present, absent or non-diagnostic. PE was present in 321 of 544 patients. Using PIOPED II criteria, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 85.1, 82.5, 88.1, and 78.4% respectively for V/P scan. Using PISA-PED criteria, sensitivity, specificity, PPV, and NPV were 86.0, 81.2, 86.8, and 80.1% respectively, and none was non-diagnostic. Sensitivity, specificity, PPV, and NPV were 81.7, 93.4, 94.9, and 77.3%, respectively for CTPA. PISA-PED interpretation has similar diagnostic accuracy to PIOPED II interpretation, does not have non-diagnostic scan, with lower cost and radiation, thus should be considered as a choice for patients with suspected PE.

Could the number of CT angiograms be reduced in emergency department patients suspected of pulmonary embolism?

This study was undertaken to identify the prevalence of pulmonary embolism (PE) in the emergency department (ED) of an urban teaching hospital and also to test a Bayesian model in estimating the number of CT pulmonary angiography (CTA) expected to be performed in an emergency department. The data for this study was obtained through a retrospective review of electronic medical records for all ED patients suspected of PE who underwent chest CTA or ventilation perfusion scanning (V/Q) between 2009 and 2010. The data is presented as means and standard deviation for continuous variables and percentages with 95% confidence intervals (95%CI) for proportions. The prevalence of PE was used as pre-test probability in the Bayesian model. Post-test probability was obtained using a Fagan nomogram and likelihood ratios for CTA. A total of 778 patients (560 females) with mean age of 50 years (range 18-98 years) were enrolled (98.3% underwent chest CTA and 1.7% underwent V/Q scan). A total of 69 patients had PE, rendering an overall prevalence of 8.9% (95%CI, 7.1% to 11.1%) for PE. We calculated that 132 CTA's per year could be avoided in our institution, without compromising safe exclusions of PE (keeping post-test probability of PE below 2%). Despite differences in our patient populations and /or study designs, the prevalence of PE in our institution is about average compared to other institutions. Our proposed model for calculating redundant chest CTA is simple and can be used by institutions to identify overuse of CTA.

Pulmonary Embolism in Pediatric Patients: Survey of CT Pulmonary Angiography Practices and Policies

To determine the current policies and practices of Society for Pediatric Radiology (SPR) members regarding the evaluation of pediatric patients with suspected pulmonary embolism (PE) with an emphasis on use of computed tomography pulmonary angiography (CTPA). Institutional review board exemption was granted for this study. Surveys were mailed electronically to the 1575 members of the SPR representing 416 institutions. Information gathered included the existence of written policies, the imaging study of choice for suspected PE, routine acquisition of chest radiographs before CTPA, currently used CTPA techniques, modifications of protocols for radiation dose reduction, typical DLP (dose-length-product) for CTPA, and estimated annual frequency of performing CTPA for evaluating PE in children. Survey items pertaining to policies and practices were compared between practice settings and populations using chi-square analysis. One hundred and sixty members representing 118 institutions responded, which resulted in a response rate of 28% (118/416), on an institutional basis. Of these 118 respondents, 104 (88%) perform CTPA in children with clinical suspicion of PE. Of the 104 respondents who perform CTPA, 26 (25%) have a written policy for CTPA, 93 (89%) perform CTPA as the first study choice, and 67 (64%) routinely obtain chest radiographs before CTPA. The most commonly used CTPA techniques in children with clinical suspicion of PE include intravenous contrast amount of 2 mL/kg, mechanical injection of intravenous contrast, and tailored bolus tracking method for CTPA scan initiation by observing the Hounsfield units of contrast in the central pulmonary artery on the monitoring scan. Sixty respondents (58%) modify CTPA imaging protocols for evaluating PE in children in order to decrease radiation dose. The two most common modifications for radiation dose reduction were reduced mAs in 41 (68%) and automatic exposure control in 38 (63%). The majority of respondents (88%) did not know the typical DLP for a 20-kg child during CTPA study performed to evaluate for PE. A significantly greater percentage of radiation dose-reduction techniques are performed within academic institutions compared with private institutions (P = .03). Most survey respondents perform CTPA as the study of choice for evaluating PE in children, but there is considerable variability in their policies and practices. Respondents from academic medical centers are more likely to employ radiation dose-reduction techniques for CTPA than those in private practice settings.

Prospective respiratory-triggered 64-slice CT pulmonary angiography for detection of pulmonary embolism—a feasibility study in a porcine model

The objective of this study is to investigate the feasibility of prospectively respiratory-triggered CT pulmonary angiography (CTPA) for detection of pulmonary embolism (PE) in a porcine model. A free-breathing respiratory-triggered multislice CTPA (120 kV, 140 mAs(eff), 2.5-mm slice thickness) and two CTPA in breath-hold technique (120 kV, 140 mAs(eff.) and 250mAs(eff), 1-mm and 3-mm image reconstruction) were performed in six pigs with pulmonary embolism. Diagnostic accuracy was computed, and differences in detection rates between both techniques were assessed on a per-embolus basis with the Wilcoxon test. Thin-sliced 1-mm images, acquired with 250mAs(eff), served as the standard of reference. Respiratory-triggered CTPA reached high diagnostic accuracy in detection of lobar and segmental PE equal to the results with the breath-hold technique (p > 0.05). For detection of subsegmental emboli, standard breath-hold techniques performed significantly better than respiratory-gated CTPA (sensitivity, 68.3% versus 24.4%; p < 0.05). Free-breathing respiratory-triggered CTPA is feasible for detection of lobar and segmental PE, with diagnostic accuracy equivalent to that of a standard CTPA in breath-hold. Although this technique is not recommended for assessment of emboli in the subsegmental vasculature, prospective respiratory-triggered CTPA may be of added value in patients who cannot hold their breath appropriately for CTPA scanning.