The diagnostic yield for computed tomography pulmonary angiography in patients with anticoagulation

BACKGROUND:Patients who present to the emergency department(ED)for suspected pulmonary embolism(PE)are often on active oral anticoagulation(AC).However,the diagnostic yield of computed tomography pulmonary angiography(CTPA)in screening for PE in patients who present on AC has not been well characterized.We aim to investigate the diagnostic yield of CTPA in diagnosing PE depending on AC status.METHODS:We reviewed and analyzed the electronic medical records of patients who underwent CTPA for PE at a university hospital ED from June 1,2019,to March 25,2022.Primary outcome was the incidence of PE on CTPA depending on baseline AC status and indication for AC.RESULTS:Of 2,846 patients,242 were on AC for a history of venous thromboembolism(VTE),210 were on AC for other indications,and 2,394 were not on AC.The incidence of PE on CTPA was significantly lower in patients on AC for other indications(5.7%)when compared to patients on AC for prior VTE(24.3%)and patients not on AC at presentation(9.8%)(P<0.001).In multivariable analysis among the whole cohort,AC was associated with a positive CTPA(odds ratio[OR]0.26,95%confidence interval[CI]:0.15-0.45,P<0.001).CONCLUSION:The incidence of PE among patients undergoing CTPA in the ED is lower in patients previously on AC for indications other than VTE when compared to those not on AC or those on AC for history of VTE.AC status and indication for AC may affect pre-test probability of a positive CTPA,and AC status therefore warrants consideration as part of future diagnostic algorithms among patients with suspected PE.

The application study of dual-energy CT nonlinearblending technique in pulmonary angiography

Objective This study aimed to explore the feasibility of enhancing image quality in computed tomography(CT) pulmonary angiography (CTPA) and reducing radiation dose using the nonlinear blending (NLB)technique of dual-energy CT.Methods A total of 61 patients scheduled for CTPA were enrolled, and 30 patients underwent dual-energyscanning. Nonlinear blending images (NLB group) and three groups of linear blending images (LB group,80 kV group, and 140 kV group) were reconstructed after scanning;31 patients underwent single-energyscanning (120 kV group). The CT values and standard deviations of the pulmonary trunk, left and rightpulmonary arteries, and ipsilateral back muscle at the bifurcation level of the left and right pulmonaryarteries were measured. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the fivegroups were calculated. The subjective image quality of the five groups was assessed. The radiation dosesof the dual- and single-energy groups were recorded and calculated.Results The CNR and SNR values of blood vessels in the NLB group were significantly higher than thosein the LB, 140 kV, and 80 kV groups (CNR of pulmonary artery trunk: t = 3.50, 4.06, 7.17, all P < 0.05;SNRof pulmonary trunk: t = 3.76, 4.71, 6.92, all P < 0.05). There were no statistical differences in the CNR andSNR values between the NLB group and 120 kV group (P > 0.05). The effective radiation dose of the dualenergygroup was lower than that of the single-energy group (t = –4.52, P < 0.05). The subjective scores ofimages in the NLB group were the highest (4.28 ± 0.74).Conclusion The NLB technique of dual-energy CT can improve the image quality of CTPA and reducethe radiation dose, providing more reliable imaging data for the clinical diagnosis of pulmonary embolism.

Computed tomography pulmonary angiography using a 20% reduction in contrast medium dose delivered in a multiphasic injection

AIM To evaluate the feasibility of reducing the dose of iodinated contrast agent in computed tomography pulmonary angiography(CTPA). METHODS One hundred and twenty-seven patients clinically suspected of having pulmonary embolism underwent spiral CTPA, out of whom fifty-seven received 75 mL and the remaining seventy a lower dose of 60 mL of contrast agent. Both doses were administered in a multiphasic injection. A minimum opacification threshold of 250 Hounsfield units(HU) in the main pulmonary artery is used for assessing the technical adequacy of the scans. RESULTS Mean opacification was found to be positively correlated to patient age(Pearson's correlation 0.4255, P < 0.0001) and independent of gender(male:female, 425.6 vs 450.4,P = 0.34). When age is accounted for, the study and control groups did not differ significantly in their mean opacification in the main(436.8 vs 437.9, P = 0.48),left(416.6 vs 419.8, P = 0.45) or the right pulmonary arteries(417.3 vs 423.5, P = 0.40). The number of sub-optimally opacified scans(the mean opacification in the main pulmonary artery < 250 HU) did not differ significantly between the study and control groups(7 vs 10).CONCLUSION A lower dose of iodine contrast at 60 mL can be feasibly used in CTPA without resulting in a higher number of sub-optimally opacified scans.

Non-selective pulmonary angiography for venous thromboembolism diagnosis, a better choice?

Objective: To evaluate the efficiency of non-selective pulmonary angiography for pulmonary embolism diagnosis. Methods: 105 consecutive subjects diagnosed with limb deep venous thrombosis (DVT) by lower limb phlebography underwent non-selective pulmonary angiography. Results: 52.38% patients were diagnosed with pulmonary embolism, 21.9% with inferior vena cava thromboembolism, and 9.52% with pulmonary embolism combined with inferior vena cava thrombosis. Images obtained by non-selective pulmonary angiography had a good correlation with selective pulmonary angiography. Conclusion: The non-selective pulmonary angiography was a simplified, efficient and safe method for pulmonary embolism diagnosis. Large clinical trials are still needed to further evaluate the accuracy and safety of the non-selective method.

Correlation of D-dimer level with the radiological severity indexes of pulmonary embolism on computed tomography pulmonary angiography

Background It is known that the main role of D-dimer has been as an exclusionary test in patients with suspected venous thromboembolism.However,the D-dimer is increasingly beginning to find clinical utility as a marker in the evaluation of the extent of the embolic disease.The aim of the study was to determine whether D-dimer levels predict the radiological markers of pulmonary embolism （PE） severity using Mastora score.Methods This prospective study involved 69 patients with acute PE proved by computed tomography pulmonary angiography （CTPA）.The D-dimer level was noted.A pulmonary artery obstruction index （PAOI; Mastora score） ≥21.3% indicated severe obstruction of PE.A right ventricle/left ventricle （RV/LV） ratio 〉0.9 indicated RV dysfunction.Results The median D-dimer level and PAOI were 765 μg/L （95% C/：750-1 205 μg/L） and 16.77% （95% CI：16.32%-23.06%）,respectively.The D-dimer level was positively correlated with PAOI （r=0.417,P 〈0.000 1）.PAOI ≥21.3% was associated with high D-dimer levels （median,993 μg/L （95% C/：856-1 841 μg/L）,Z=-2.991,P=0.003）.The D-dimer level was correlated with the RV/LV ratio （r=0.272,P=0.024）.RV/LV ratios 〉0.9 were associated with high D-dimer levels （median,880 μg/L （95% CI：764-1 360 μg/L）,Z=-2.070,P=0.038）.PAOI was positively correlated with the RV/LV ratio （r =0.390,P=0.001）.After three months,both the PAOI and D-dimer levels decreased （Z=-7.009,P 〈0.000 1; Z=-6.976,P〈0.000 1,respectively）.Conclusion D-dimer levels are positively correlated with PE burden and right ventricle dysfunction on CTPA,and can help monitor the therapeutic response.

Hemodynamic effects and safety of pulmonary angiography in Chinese patients with pulmonary hypertension

Background Pulmonary angiography is widely performed in pulmonary hypertension patients, but its immediate effects on right heart hemodynamics and safety are not well known. The objective of this study was to investigate the right heart hemodynamic effects and safety of pulmonary angiography in Chinese patients with pulmonary hypertension. Methods Between January 2008 and June 2009, pulmonary hypertension patients undergoing pulmonary angiography were consecutively enrolled. Pulmonary angiography was performed during breath-holding after deep breathing. The baseline clinical data, hemodynamic measurements before and after pulmonary angiography and complications occurring within 48 hours after angiography were recorded. Results Ninety-five patients were included. All received non-ionic contrast medium with a volume of （75.7±29.8） ml. Angiography reduced heart rate in patients with baseline mean pulmonary arterial pressure 〉 60 mmHg （change of heart rate： （-3.1±7.0） beats/min, P=0.005）, increased mean right atrial pressure, diastolic and end-diastolic right ventricular pressure in patients with baseline mean pulmonary arterial pressure 〈60 mmHg （all P 〈0.05）. Patients with decreased mean pulmonary arterial pressure （change of mean pulmonary arterial pressure 〈 -10 mmHg） had the highest total pulmonary resistance （P=0.009 vs. no change in mean pulmonary arterial pressure （change of mean pulmonary arterial pressure, -10 mmHg to 10 mmHg）; P=0.03 vs. increased mean pulmonary arterial pressure （change of mean pulmonary arterial pressure 〉 10 mmHg）） and the lowest cardiac output （P=-0.018 vs. no change in mean pulmonary arterial pressure; P=0.013 vs. increased mean pulmonary arterial pressure）. There were 7 complications （7%）, with 6 related to catheter and only 1 directly related to angiography. All complications were mild and no death occurred. Conclusion Pulmonary angiography has minimal effect on right heart hemodynamics and is safe in pulmonary hypertension patients.

Role of pulmonary perfusion magnetic resonance imaging for the diagnosis of pulmonary hypertension:A review

Among five types of pulmonary hypertension,chronic thromboembolic pulmonary hypertension(CTEPH)is the only curable form,but prompt and accurate diagnosis can be challenging.Computed tomography and nuclear medicine-based techniques are standard imaging modalities to non-invasively diagnose CTEPH,however these are limited by radiation exposure,subjective qualitative bias,and lack of cardiac functional assessment.This review aims to assess the methodology,diagnostic accuracy of pulmonary perfusion imaging in the current literature and discuss its advantages,limitations and future research scope.

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.

Gadolinium Enhances Dual-energy Computed Tomography Scan of Pulmonary Artery

Objective To evaluate the feasibility of using gadopentetate dimeglumine(Gd-DTPA)for dual-energy computed tomography pulmonary angiography(CTPA).Methods Sixty-six patients were randomly divided into three groups and underwent CTPA.Group A had a turbo flash scan using an iohexol injection,Group B had a turbo flash scan using Gd-DTPA,and Group C had a dual-energy scan using Gd-DTPA.The original images of Group C were linearly blended with a blending factor of 0.5 or reconstructed at 40,50,60,70,80,90,100,and 110 keV,respectively.The groups were compared in terms of pulmonary artery CT value,image quality,and radiation dose.Results The pulmonary artery CT values were significantly higher in Group C40keV than in Groups B and C,but lower than in Group A.There was no significant difference in the image noise of Groups C40keV,B,and C.Moreover,Group A had the largest beam hardening artifacts of the superior vena cava(SVC),followed by Groups B and C.Group C40keV showed better vascular branching than the other three groups,among which Group B was superior to Group A.The subjective score of the image quality of Groups A,B,and C showed no significant difference,but the score was significantly higher in Group C40keV than in Groups A and B.The radiation dose was significantly lower in Group B than in Groups A and C.Conclusion Gd-CTPA is recommended to patients who are unsuitable for receiving an iodine-based CTPA.Furthermore,a turbo flash scan could surpass a dual-energy scan without consideration for virtual monoenergetic imaging.

Diagnostic Evaluation of Pulmonary Embolism: A Computerized Tomography Based Study

Pulmonary embolism (PE) is potentially life threatening condition which requires adequate diagnosis. Since computerized tomography pulmonary angiography (CTPA) described the presence of a clot subjectively, an objective and quantification method to characterize plural parenchymal abnormality, pulmonary vessels and heart is needed (in order to diagnose PE). This study was directed to investigate whether the presence of plural parenchymal findings correlates with the PE and as well, it was designed to answer two basic questions based on CTPA findings done for clinical suspicion of PE: firstly, what are the plural parenchymal abnormalities associated with PE;secondly, correlation of PE with the presence of heart changes and pulmonary vessels measurements. CTPA scans were acquired for 55 patients suspected of having PE and another 50 subjects who were considered as control. The clinical signs and pleuroparenchymal abnormalities, pulmonary artery tree measurements, right ventricle and atrium diameters, Inter ventricular septum width as well as the myocardium thickening were characterized and correlated with PE. The results showed that the PE patients group has more dilated measurements than the normal control subjects. The right ventricle diameter changes were found to be significantly related to the presence of PE at p ≤ 0.001. Significant changes at p ≤ 0.005 were also noticed in the pulmonary trunk diameter as well as the right and left main pulmonary arteries with no significant changes detected in the distal portion of both pulmonary arteries diameters. The common complaints from PE patients were chest pain, shortness of breathing, lower limb swelling, tachycardia and syncope. Consolidation, ground glass opacifications, mosaic, right ventricle morphological changes and pleural effusion were present in the majority of patients undergoing CTPA for the clinical suspicion of PE. CTPA is considered as the diagnostic modality of choice in characterization of pulmonary vessels, atrium and ventricle changes as well as pleura parenchymal abnormalities in patients with or without PE.

CT angiography of pulmonary embolism using a 64 slice multi-detector scanner

Background Multi-detector computed tomography （MDCT） has already been the first line investigation method for diagnosis of pulmonary embolism （PE）. Reducing the amount of contrast medium used during CT scanning could decrease the incidental rate of adverse reactions. Our study amied to evaluate the image quality of pulmonary arteries using 64 slice multi-detector CT with small volumes of contrast media injection. Methods Forty nonconsecutive patients without PE or other lung diseases were randomly assigned to two groups. Group A underwent CT scanning with 16×1 .25 mm collimation and a 70 ml contrast injection, while group B had CT with 64×0.625 mm collimation and 20 ml of contrast injection. Two readers independently depicted the segmental and subsegmental pulmonary arteries. Reasons we could not analyze the pulmonary artery or that led to misdiagnosis of pulmonary embolism were evaluated, including the degree of contrast enhancement of the main pulmonary artery, and factors that caused misdiagnosis of PE （flow-related artifacts, partial volume artifact, beam-hardening artifacts and enhancement of pulmonary vein）. The independent samples t-test, Mann-Whitney U test and Pearson chi-square test were applied. Results There were no significant differences in image quality of segmental and subsegmental arteries between the two groups. No significant difference was found for factors that made pulmonary arteries non-analyzable or in the misdiagnosis of PE, except the degree of contrast enhancement. Conclusion 64×0.625 mm collimation with 20 ml contrast injection could depict the pulmonary arteries well.

Contrast enhanced MR angiography in pulmonary sequestration

Objective To evaluate the feasibility of contrast enhanced three-dimensional(3D)magnetic resonance angiography(MRA)in identifying the systemic blood supply in pulmonary sequestration.Methods Three patients who were suspected of pulmonary sequestration were examined by contrast enhanced 3D MRA.MR images were compared with surgical findings.Results Contrast enhanced 3D MRA clearly demonstrated systemic arteries from the descending thoracic aorta supplying the basilar segments of the lower lobe in each case.Pulmonary veins from these segments,which drained into the left atrium in two cases,were also detected.MRA images were consistent with those observed in surgery.Conclusion Contrast enhanced 3D MRA allows accurate diagnosis of pulmonary sequestration and may obviate the need for more invasive investigations.

Incidence of Pleural Effusion in Patients with Pulmonary Embolism

Background： No data on the incidence ofpleural effusion （PE） in Chinese patients with pulmonary embolism are available to date. The aim of the current study was to investigate the frequency of PE in a Chinese population of patients with pulmonary embolism. Methods： This was a retrospective observational single-center study. All data of computed tomography pulmonary angiography （CTPA） performed over 6-year period on adult patients with clinically suspected pulmonary embolism were analyzed. Results： From January 2008 until December 2013, PE was identified in 423 of 3141 patients （13.5%） with clinically suspected pulmonary embolism who underwent CTPA, The incidence of PE in patients with pulmonary embolism （19.9%） was significantly higher than in those without embolism （9.4%） （P 〈 0.001 ）. Majority of PEs in pulmonary embolism patients were small to moderate and were unilateral. The locations of emboli and the numbers of arteries involved, CT pulmonary obstruction index, and parenchymal abnormalities at CT were not associated with the development of PE, Conclusions： PEs are present in about one fifth of a Chinese population of patients with pulmonary embolism, which are usually small, unilateral, and unsuitable for diagnostic thoracentesis.

Primary pulmonary artery chondrosarcoma： the use of different imaging modalities

Fewer than 300 patients with primary pulmonary artery sarcoma have been reported since 1923,when it was first described by Mandelstamm.1 The diagnosis of pulmonary artery sarcoma is difficult,and misdiagnosis as chronic pulmonary embolism often occurs.Herein,we reported a case of primary pulmonary artery chondrosarcoma.So far as we know,this patient served as the first case ever reported to receive computed tomography pulmonary angiography （CTPA）,gadolinium enhanced magnetic resonance imaging （MRI）,and positron emission tomography/computed tomography （PET/CT） before surgery.By these means,the utility of different imaging modalities for pulmonary artery sarcoma was well demonstrated.Keywords：primary pulmonary artery chondrosarcoma; computed tomography pulmonary angiography;magnetic resonance imaging; positron emission tomography