Management of suspected acute pulmonary embolism in the era of CT angiography: a statement from the Fleischner Society

Diagnostic yield of CT thorax angiography in patients suspected of pulmonary embolism: independent predictors and protocol adherence

Objectives

To determine the diagnostic yield of computed tomography scanning of the pulmonary arteries (CTPA) in our centre and factors associated with it. Differences between specialties as well as adherence to protocol were investigated.

Methods

All patients receiving a first CTPA for pulmonary embolism (PE) in 2010 were included. Data about relevant clinical information and the requesting specialty were retrospectively obtained. Differences in diagnostic yield were tested using a chi-squared test. Independent predictors were identified with multivariate logistic regression.

Results

PE on CTPA was found in 224 of the 974 patients (23 %). Between specialties, diagnostic yield varied from 19.5 to 23.9 % (p = 0.20). Independent predictors of diagnostic yield were: age, sex, D-dimer, cough, dyspnea, cardiac history, chronic obstructive pulmonary disease (COPD), atelectasis/consolidation, intrapulmonary mass and/or interstitial pulmonary disease on CT. Wells scores were poorly documented (n = 127, 13.0 %). Poor adherence to protocol was also shown by a high amount of unnecessary D-dimer values with a high Wells-score (35 of 58; 58.6 %).

Conclusions

The diagnostic yield of CTPA in this study was relatively high in comparison with other studies (6.7–31 %). Better adherence to protocol might improve the diagnostic yield further. A prospective study could confirm the independent predictors found in this study.

Teaching Points

• Pulmonary embolism is potentially life-threatening and requires quick and reliable diagnosis.

• Computed tomography of the pulmonary arteries (CTPA) provides this reliable diagnosis.

• Several independent predictors of diagnostic yield of CTPA for pulmonary embolism were identified.

• Diagnostic yield of CTPA did not differ between requesting specialties in our Hospital.

• Better protocol adherence could improve the diagnostic yield of CTPA for pulmonary embolism.

Evaluation of imaging quality of pulmonary 64-MDCT angiography in pregnancy and puerperium

OBJECTIVE

The aim of this study was to quantitatively and qualitatively evaluate pulmonary 64-MDCT angiography image quality in pregnancy and puerperium, compared with female nonpregnant control subjects.

MATERIALS AND METHODS

The study group comprised 124 consecutive pregnant and postpartum women and 124 female nonpregnant control subjects who presented with suspected pulmonary embolism. The individual studies were evaluated for subjective and objective diagnostic quality.

RESULTS

Objective measurements of the arterial enhancement in the pulmonary trunk and left and right pulmonary arteries found that there was no statistically significant difference in attenuation values between the pregnant and puerperium group and the control group for pulmonary artery opacification. The mean attenuation in the pulmonary trunk was 270.54 HU in the pregnant group, 277.53 HU in the puerperium group, and 293.90 HU in the control group.

CONCLUSION

We found no significant difference in diagnostic quality of pulmonary CT angiography using MDCT between the study and control groups. The use of MDCT acquisition, faster injection rates, higher contrast medium concentration, and higher trigger levels may decrease the number of nondiagnostic studies in this population. MDCT may be a worthwhile investigation in the majority of pregnant patients with suspected pulmonary embolism.

Prevalence of venous thromboembolism at diagnosis of upper gastrointestinal cancer

BACKGROUND

Venous thromboembolism (VTE) in patients with upper gastrointestinal (GI) cancer increases morbidity and mortality. This study aimed to determine the prevalence of VTE at diagnosis of upper GI cancer.

METHODS

Patients admitted between February 2008 and February 2011 with upper GI cancer (pancreatic, extrahepatic biliary, lower oesophageal, gastro-oesophageal junction or gastric cancer) were investigated in a cross-sectional cohort study. At cancer diagnosis, all patients were examined for deep vein thrombosis (DVT) by means of bilateral compression ultrasonography. From February 2009 and onwards, computed tomographic pulmonary angiography (CTPA) was also performed for the diagnosis of pulmonary embolism (PE).

RESULTS

Some 250 patients had ultrasonography; CTPA was performed in 143 patients on admission. DVT was detected in 13 (5·2 per cent) of the 250 patients, eight (3·2 per cent) of whom were asymptomatic. DVT was correlated with tumour location in the pancreaticobiliary tract (odds ratio (OR) 6·27, 95 per cent confidence interval 1·18 to 33·38; P = 0·031) and tumour stage IV (OR 19·34, 2·33 to 160·70; P = 0·006). PE was detected in 11 (7·7 per cent) of 143 patients, eight (5·6 per cent) of whom were asymptomatic. PE embolism was also significantly more common in patients with pancreaticobiliary tract cancer (OR 7·81, 1·28 to 47·62; P = 0·026) and in those with stage IV disease (OR 17·19, 1·83 to 161·50; P = 0·013).

CONCLUSION

The prevalence of VTE at cancer diagnosis was significantly higher in patients with pancreaticobiliary tract cancer than in those with other forms of upper GI cancer, and in patients with advanced cancer stage.

High-pitch ECG-synchronized pulmonary CT angiography versus standard CT pulmonary angiography: a prospective randomized study

OBJECTIVE

The purpose of this study was to compare high-pitch ECG-synchronized pulmonary CT angiography (CTA) with standard pulmonary CTA with regard to radiation dose and image quality in patients with suspected pulmonary embolism.

SUBJECTS AND METHODS

This prospective study was approved by the institutional review board, and participants provided informed consent. Patients with suspected pulmonary embolism (60% women; mean age, 57 ± 14 years) were randomized to undergo high-pitch ECG-synchronized pulmonary CTA (n = 26) or standard pulmonary CTA (n = 21). Two independent readers assessed subjective image quality of pulmonary arteries, cardiovascular structures, and pulmonary parenchyma. Signal intensity (SI) was measured in one segmental and three central pulmonary arteries.

RESULTS

High-pitch ECG-synchronized pulmonary CTA showed higher SI (p < 0.001) for pulmonary arteries. Image quality scores indicated improvement in assessment of cardio-vascular structures (p < 0.001), minimization of motion of central (p < 0.001) pulmonary arteries, and an increase in pulmonary arterial enhancement (p = 0.01) with high-pitch ECG-synchronized pulmonary CTA. Image quality scores for lung assessment were higher for standard pulmonary CTA (p < 0.001). The amount of contrast agent administered was similar between techniques (p = 0.86). Radiation dose was lower for high-pitch ECG-synchronized pulmonary CTA (p < 0.001).

CONCLUSION

High-pitch ECG-synchronized pulmonary CTA provides higher pulmonary arterial SI, decreased motion of central pulmonary arteries, and improved assessment of cardiovascular structures with similar contrast dose and lower radiation compared with standard pulmonary CTA.

Diagnosis and treatment of pulmonary embolism: a multidisciplinary approach

The diagnosis of pulmonary embolism (PE) is frequently considered in patients presenting to the emergency department or when hospitalized. Although early treatment is highly effective, PE is underdiagnosed and, therefore, the disease remains a major health problem. Since symptoms and signs are non specific and the consequences of anticoagulant treatment are considerable, objective tests to either establish or refute the diagnosis have become a standard of care. Diagnostic strategy should be based on clinical evaluation of the probability of PE. The accuracy of diagnostic tests for PE are high when the results are concordant with the clinical assessment. Additional testing is necessary when the test results are inconsistent with clinical probability. The present review article represents the consensus-based recommendations of the Interdisciplinary Association for Research in Lung Disease (AIMAR) multidisciplinary Task Force for diagnosis and treatment of PE. The aim of this review is to provide clinicians a practical diagnostic and therapeutic management approach using evidence from the literature.

Reduced z-axis coverage in multidetector-row CT pulmonary angiography decreases radiation dose and diagnostic accuracy of alternative diseases

OBJECTIVE

To investigate the effect of a two-third reduction of the scanned length (i.e. 10 cm) on diagnosis of both pulmonary embolism (PE) and alternative diseases.

METHODS

247 consecutive patients suspected of acute PE had a CT pulmonary angiography (CTPA) of the thorax (standard length, L). Based on this acquisition, a second set of images was created to obtain a scan length of 10 cm caudally to the aortic arch (l). Images were anonymized, randomized and interpreted by two independent readers. The quality of enhancement, the presence of PE and the possible alternative and/or complementary diagnoses were recorded. A McNemar exact test investigated differences in discrepancies between readers and between scan lengths.

RESULTS

57 (23%) patients had an acute PE. Among l sets, PE was missed by both readers in one (1.8%) patient, because the unique clot was localized in a subsegmental artery out of the 10-cm range. There were discrepancies between L and l sets in 9 (3.6%) and 11 (4.5%) patients, by Readers 1 and 2 (p=0.820), respectively. Discrepancies between the readers of L sets and those between both sets were not different regardless of the reader (p>0.99). There were discrepancies between both sets for alternative and/or complementary diagnoses in 43 (17.2%) patients.

CONCLUSION

Although its performance in diagnosing PE is maintained, CTPA should not be restricted to a range of 10 cm centred over the pulmonary hilum, because alternative and/or complementary diagnoses could be missed.

ADVANCES IN KNOWLEDGE

(1) A 10-cm CTPA acquisition reduces the radiation dose by two-thirds as compared with a standard one, but does not impair the accuracy for the diagnosis of PE. (2) Significant alternative diagnoses are missed in 17.2% of patients when reducing the acquisition height to 10 cm.

Variable D-dimer thresholds for diagnosis of clinically suspected acute pulmonary embolism

BACKGROUND

Computed tomography pulmonary angiography (CTPA) is frequently requested using diagnostic algorithms for suspected pulmonary embolism (PE). For suspected deep vein thrombosis, it was recently shown that doubling the D-dimer threshold in patients with low pretest probability safely decreased the number of ultrasonograms. We evaluated the safety and efficiency of a similar strategy in patients with suspected PE.

METHODS

We performed a post-hoc analysis of 2213 consecutive patients of two cohort studies with suspected PE who were managed according to current standards: PE ruled out in case of unlikely probability (Wells rule ≤ 4 points) and a D-dimer level < 0.5 μg mL(-1) . CTPA was performed in all other cases. All patients were followed for 3 months. We calculated 3-month venous thromboembolism (VTE) incidence and the number of required CTPAs for selective D-dimer thresholds in patients with low clinical probability (< 2 points, D-dimer threshold < 1.0 μg mL(-1) ) and intermediate probability (2-6 points, D-dimer threshold < 0.5 μg mL(-1) ).

RESULTS

Using standard management, PE could be excluded without CTPA in 26% of patients, with a 3-month VTE incidence of 0.88% (95% confidence interval [CI] 0.29-2.1%). Using selective D-dimer thresholds, PE could be excluded without CTPA in 36% of patients, with a 3-month VTE incidence of 2.1% (95% CI 1.2-3.4%) in patients managed without CTPA, an increase of 1.2 percentage points (95% CI -0.3 to 2.2).

CONCLUSIONS

Applying selective D-dimer thresholds reduces the need for CTPA by 11 percentage points but is associated with an increased failure rate. Prospective studies should evaluate the safety and net clinical benefit of this approach.

Comparison of non-invasive diagnostic tests to multi-detector CT pulmonary angiography for the diagnosis of pulmonary embolism

CONTEXT

Acute pulmonary embolism (PE) remains a diagnostic and therapeutic challenge to physicians. There are various non-invasive diagnostic modalities been suggested to diagnose pulmonary embolism.

AIM

We tried to find the performance of various non-invasive investigations in comparison to multi-detector Computerized Tomography (MDCT pulmonary angiography for the diagnosis of PE).

SETTINGS AND DESIGN

A prospective cohort study was conducted in 80 hospitalized medical patients.

MATERIALS AND METHODS

There were 80 patients with Wells score > 2 who were included. The demographic data, non-invasive investigations, and MDCT pulmonary angiography were conducted in these patients. The sensitivity (SEN), specificity (SPE), positive predictive value (PPV), and negative predictive value (NPV) were calculated for each test.

RESULTS

Out of 80 patients, 77.5% patients were with Wells score 3-6 and 22.5% patients were with Wells score more than 6. The test with highest sensitivity was d-dimer (SEN - 90%, P = 0.091) followed by PAH on TTE (SEN - 83%, PPV - 86%, P = 0.006). The most specific test was ECG showing S1Q3T3 (SPE - 100%, P = 0.421), followed by Wells score > 6 (SPE - 91%, P = 0.211). There was no test with sensitivity and specificity more than 90%

CONCLUSION

In all patients with intermediate to high-risk probability MDCT pulmonary angiography is the most accurate test to diagnose PE and should be performed at the earliest. The combination of 2-dimensional ECHO and d-dimer can be used in patients with a high clinical suspicion of PE on pre-test probability where MDCT pulmonary angiography is not possible.

The influence of education on appropriateness rates for CT pulmonary angiography in emergency department patients

RATIONALE AND OBJECTIVES

To evaluate appropriate utilization rates for computed tomography (CT) pulmonary angiography (CTPA) in a tertiary center emergency department (ED), before and after a health care provider educational intervention.

MATERIALS AND METHODS

Institutional Review Board-approved retrospective study. Records for 100 consecutive CTPA studies ordered by the ED were retrieved from a radiology database. Appropriateness rates for the studies were determined using information from existing literature (clinical decision rules and society guidelines). Where pretest probability was not performed, it was calculated by the authors. After ED health care provider education regarding appropriateness guidelines through a dedicated lecture and question-and-answer session, appropriateness rates for another 100 consecutive CTPA ordered by the ED were calculated.

RESULTS

In the preeducational intervention, 1% of patients had Wells scores performed, 65% were women, and 29% were age <40 years. Before CTPA, 40% patients had d-dimer testing, 15% of patients had a "negative" d-dimer, 17% had alternative explanations for chest pain, and 76% had low or intermediate pretest probability. Appropriateness rates for CTPA was 7%, and 8% of studies were positive. Postintervention, no Wells scores were performed, 59% were women, and 34% <40 years. Before CTPA, 32% of patients had d-dimer, 16% had a "negative" d-dimer, 22% had alternative explanations for chest pain, and 84% had low or intermediate pretest probability. The appropriateness rate for CTPA was 6% and 10% of studies were positive.

CONCLUSION

A single educational intervention had no effect on appropriate utilization rates for CTPA. Repeated and sustained educational interventions may help improve imaging ordering pathways through the ED and other departments.

Associations between presence of relevant information in referrals to radiology and prevalence rates in patients with suspected pulmonary embolism

RATIONALE AND OBJECTIVES

The purpose of this study was to assess if the presence of information including the pretest probability (Wells score), other known risk factors, and symptoms given on referrals for computed tomography (CT) pulmonary angiography correlated with prevalence rates for pulmonary embolism (PE). Also, to evaluate for differences between a university and a regional hospital setting regarding patient characteristics, amount of relevant information provided on referrals, and prevalence rates for pulmonary embolism.

MATERIALS AND METHODS

Retrospective review of all consecutive referrals (emergency room, inpatient, and outpatient) for CT performed on children and adults for suspected PE from two sites: a tertiary (university) hospital (site 1) and a secondary (regional) hospital (site 2) over a 5-year period.

RESULTS

The overall prevalence rate was 510/3641 or 14% of all referrals. Significantly higher number of males had a positive CT compared to women (18% versus 12%, P < .001). Although no statistically significant relationship between a greater amount of relevant information on the referral and the probability for positive finding existed, a slight trend was noted (P = .09). In two categories, "hypoxia" and "signs of deep vein thrombosis," the presence of this information conferred a higher probability for pulmonary embolism, P < .001. In the categories, "chest pain," "malaise," and "smoker/chronic obstructive pulmonary disease", the absence of information conferred a higher probability for pulmonary embolism.

CONCLUSIONS

The amount of relevant clinical information on the request did not correlate with prevalence rates, which may reflect a lack of documentation on the part of emergency physicians who may use a "gestalt" approach. Request forms likely did not capture all relevant patient risks and many factors may interact with each other, both positively and negatively. Pretest probability estimations were rarely performed, despite their inclusion in major society guidelines.

Impact of iodine delivery rate with varying flow rates on image quality in dual-energy CT of patients with suspected pulmonary embolism

RATIONALE AND OBJECTIVES

To prospectively compare four contrast material injection protocols for dual-energy computed tomography (CT) pulmonary angiography (DE-CTPA) in patients with suspected pulmonary embolism (PE).

MATERIALS AND METHODS

One hundred twenty consecutive patients were randomized to contrast material injection protocols defined by different iodine concentrations and iodine delivery rates (IDRs): (A) 80 mL iopromide 370/4 mL/sec = IDR 1.4 gI/sec; (B) 80 mL iopromide 370 at 3 mL/sec = IDR 1.1 gI/sec; (C) 98 mL iopromide 300 at 4.9 mL/sec = IDR 1.4 gI/sec; and (D) 98 mL iopromide 300 at 3.7 mL/sec = IDR 1.1 gI/sec. Attenuation values were measured in the inflow tract (subclavian vein-superior vena cava-right atrium), target tract (right ventricle-pulmonary trunk-pulmonary arteries), and outflow tract (left atrium-left ventricle-ascending aorta). Two readers assessed subjective image quality of CTPA images and iodine perfusion maps. The number of artifacts due to hyperdense contrast material on iodine perfusion maps was recorded.

RESULTS

Target tract attenuation was highest for protocol A with 374 ± 98 Hounsfield units (HU) (highly concentrated contrast material/high IDR). This was significant compared to protocols B and D (P = .0118, P = .0427) but not compared to protocol C (P = .3395). No significant difference in target tract attenuation was found between protocols B (309 ± 80 HU), protocol C (352 ± 119 HU), and D (325 ± 74 HU). CTPA and iodine perfusion map image quality for protocol A was rated significantly higher compared to all other protocols (median score = 5/4; P < .0001 for both) with moderate interreader agreement (κ = 0.58/0.47). Protocols A and B displayed increased artifacts on iodine perfusion maps compared to protocols C and D (3 versus 2).

CONCLUSION

Despite increased artifacts on iodine perfusion maps, highly concentrated iodinated contrast material combined with high flow rates provides improved diagnostic image quality and has the highest target-tract attenuation for DE-CTPA protocols.

Dual-energy CT based vascular iodine analysis improves sensitivity for peripheral pulmonary artery thrombus detection: an experimental study in canines

PURPOSE

To evaluate the performance of dual-energy CT (DECT) based vascular iodine analysis for the detection of acute peripheral pulmonary thrombus (PE) in a canine model with histopathological findings as the reference standard.

MATERIALS AND METHODS

The study protocol was approved by our institutional animal committee. Thrombi (n = 12) or saline (n = 4) were intravenously injected via right femoral vein in sixteen dogs, respectively. CT pulmonary angiography (CTPA) in DECT mode was performed and conventional CTPA images and DECT based vascular iodine studies using Lung Vessels application were reconstructed. Two radiologists visually evaluated the number and location of PEs using conventional CTPA and DECT series on a per-animal and a per-clot basis. Detailed histopathological examination of lung specimens and catheter angiography served as reference standard. Sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) of DECT and CTPA were calculated on a segmental and subsegmental or more distal pulmonary artery basis. Weighted κ values were computed to evaluate inter-modality and inter-reader agreement.

RESULTS

Thirteen dogs were enrolled for final image analysis (experimental group = 9, control group = 4). Histopathological results revealed 237 emboli in 45 lung lobes in 9 experimental dogs, 11 emboli in segmental pulmonary arteries, 49 in subsegmental pulmonary arteries, 177 in fifth-order or more distal pulmonary arteries. Overall sensitivity, specificity, accuracy, PPV, and NPV for CTPA plus DECT were 93.1%, 76.9%, 87.8%, 89.4%, and 84.2% for the detection of pulmonary emboli. With CTPA versus DECT, sensitivities, specificities, accuracies, PPVs, and NPVs are all 100% for the detection of pulmonary emboli on a segmental pulmonary artery basis, 88.9%, 100%, 96.0%, 100%, and 94.1% for CTPA and 90.4%, 93.0%, 92.0%, 88.7%, and 94.1% for DECT on a subsegmental pulmonary artery basis; 23.8%, 96.4%, 50.4%, 93.5%, and 36.7% for CTPA and 95.9%, 75.5%, 88.2%, 86.5%, and 91.9% on a sub-subsegmental and more distal pulmonary artery basis, respectively. Good inter-modality (κ = 0.65, P<0.001) and inter-reader (κ = 0.70, P<0.001) agreement were observed.

CONCLUSION

With histopathological findings as the reference standard, DECT based vascular iodine analysis improves the sensitivity for detecting peripheral PE compared with CTPA, albeit at the price of decreased specificity and PPV.

Diagnostic accuracy of lung ultrasound for pulmonary embolism: a systematic review and meta-analysis

BACKGROUND

Computed tomographic pulmonary angiography (CTPA) has simplified the diagnostic approach to patients with suspected pulmonary embolism (PE). However, PE diagnosis is still probabilistic and CTPA should be used with caution in some patient groups, such as patients with severe renal insufficiency and pregnant women. Among alternative imaging tests, lung ultrasound is the most promising technique. We aimed to systematically assess the diagnostic accuracy of lung ultrasound for PE diagnosis.

METHODS

Studies evaluating the diagnostic accuracy of lung ultrasound for the diagnosis of PE were systematically searched for in the MEDLINE and EMBASE databases (up to June 2012). The QUADAS-2 tool was used for the quality assessment of the primary studies. A bivariate random-effects regression approach was used for summary estimates of both sensitivity and specificity.

RESULTS

Ten studies, for a total of 887 patients, were included. A composite reference test was used in six studies, with single-row detector CTPA as the principal imaging test in four studies. Overall, seven studies used a proper reference test. Lung ultrasound bivariate weighted mean sensitivity was 87.0% (95% confidence interval [CI] 79.5, 92.0%), whereas bivariate weighted mean specificity was 81.8% (95% CI 71.0, 89.3%).

CONCLUSIONS

Our findings suggest that lung ultrasound may be a useful diagnostic tool in the management of patients with suspected PE. However, several methodological drawbacks of the primary studies limit any definite conclusion. Further well-designed accuracy studies are necessary before planning diagnostic management studies, in particular in those with a contraindication for CTPA.

The rate of resolution of clot burden measured by pulmonary CT angiography in patients with acute pulmonary embolism

OBJECTIVE

The purpose of this article is to quantitatively assess the rate of resolution of clot burden detected on pulmonary CT angiography (CTA) in patients with acute pulmonary embolism (PE).

MATERIALS AND METHODS

We evaluated 111 consecutive patients (55 men and 56 women) in a retrospective cohort who were diagnosed with PE by pulmonary CTA and had at least one follow-up pulmonary CTA within 1 year. Two radiologists in consensus measured the volume of each clot using a semiautomated quantification program. Semiquantitative measures of clot burden were also computed. The resolution rates of the total clot volume, as well as clot volumes of the central (main and lobar) and peripheral vessels (segmental and subsegmental), were analyzed.

RESULTS

The mean (± SD) clot volume per study was 3403.3 ± 6505.6 mm(3) at baseline and 531.6 ± 2383.5 mm(3) at the follow-up pulmonary CTA. Overall, 85 patients (77% ) showed complete resolution at the follow-up pulmonary CTA. Complete resolution was seen in 17 of 30 patients (56.7%) at a follow-up interval of 1-14 days, in 24 of 31 patients (77.4%) at 29-90 days, and in 32 of 34 patients (94.1%) after 90 days. The total clot volume measurements summed for all patients decreased by 78% (central clot, 69.4%; peripheral clot, 86.0%) at 14 days, by 96.6% (central clot, 93.4%; peripheral clot, 100%) at 90 days, and by 97.7% (central clot, 95.9%; peripheral clot, 100%) after 90 days.

CONCLUSION

Clot burden resolved completely in 77% of patients during the follow-up period. Our analysis showed that clots resolved faster in the peripheral arteries than in the central pulmonary arteries.

Evaluation of high-pitch flash scan for pulmonary venous CTA on a 128-slice dual source CT: compared with prospective ECG-triggered sequence scan

To compare the image quality (IQ) and radiation dose of high-pitch scan and prospective ECG-triggered sequence scan on a 128-slice DSCT system for patients with atrial fibrillation (AF). Pulmonary venous (PV) CTA was performed with two protocols, including high-pitch scan and prospective ECG-triggered sequence scan. For each protocol, 20 sex, age and body-mass-index (mean 24.2 kg/m(2)) matched patients were identified. Two experienced radiologists, who were blinded to the scan protocols, independently graded the CT images of the two groups by a 5-point scale for subjective IQ assessment. Measured CT attenuation (Hounsfield units ± standard deviation), signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) at various anatomic locations were also recorded for objective IQ evaluation. Radiation exposure parameters [dose length product (DLP) and effective radiation dose (ERD)] were compared. Twenty-three patients (57.5 %) showed an ECG pattern of AF in total. Subjective IQ was rated excellent in 100 % for the high-pitch scan group, while minor step artifacts were observed in two patients (10 %) with arrhythmia for the prospective ECG-triggered sequence group. There was no significant difference on IQ, neither by subjective, nor by objective measures (SNR, CNR) between the two groups. The ERD of high-pitch flash scan and prospective ECG-triggered sequence scan were 0.9 (± 0.25) and 2.9 (± 0.69) mSv, respectively. Significantly lower radiation was achieved by using high-pitch flash scan (P < 0.05). High-pitch flash scan can provide similar subjective and objective IQ compared with prospective ECG-triggered sequence scan for PV CTA, while radiation exposure was significantly reduced.

How I diagnose acute pulmonary embolism

The clinical diagnosis of acute pulmonary embolism (PE) is frequently considered in patients presenting to the emergency department or when hospitalized. Since symptoms are a-specific and the consequences of anticoagulant treatment are considerable, objective tests to either establish or refute the diagnosis have become a standard of care. Computed tomographic pulmonary angiography (CTPA), which has replaced pulmonary angiography as first-line imaging test, is associated with radiation exposure, several complications resulting from contrast dye administration, and over diagnosis. Importantly, CTPA can be avoided in 20% to 30% of patients who present with a first or recurrent episode of clinically suspected acute PE by using a standardized algorithm. This algorithm should always include a clinical decision rule to assess the likelihood that PE is present, followed by a D-dimer blood test and/or CTPA. The aim of this review is to provide clinicians this practical diagnostic management approach using evidence from the literature.

A completed audit cycle of the lateral scan projection radiograph in CT pulmonary angiography (CTPA); the impact on scan length and radiation dose

AIM

To investigate the effect of incorporating a lateral scan projection radiograph (topogram) in addition to the standard frontal topogram on excess scan length in computed tomography pulmonary angiography (CTPA) and to quantify the impact on effective dose.

MATERIALS AND METHODS

Fifty consecutive patients referred for exclusion of pulmonary embolism who had undergone a CTPA examination with conventional frontal topogram to plan scan length (protocol A) were compared with 50 consecutive patients who had undergone a CTPA study with frontal and additional lateral topogram for planning (protocol B) in a retrospective audit. Optimal scan length was defined from lung apex to lung base. Mean excess scan length beyond these landmarks was determined. The mean organ doses to the thyroid, liver, and stomach, as well as mean effective dose, were estimated using standard conversion factors.

RESULTS

The mean excess scan length was significantly lower in protocol B compared to the protocol A cohort (19.5 ± 17.4 mm [mean ± standard deviation] versus 39.1 ± 20.4 mm, p < 0.0001). The mean excess scan length below the lung bases was significantly lower in the protocol B cohort compared to the protocol A group (7.5 ± 12.7 mm versus 23 ± 16.6 mm, p < 0.0001), as were the mean organ doses to the stomach (4.24 ± 0.81 mGy versus 5.22 ± 1.06 mGy, p < 0.0001) and liver (5.60 ± 0.64 mGy versus 6.38 ± 0.81 mGy, p < 0.0001). A non-significant reduction in over-scanning above the apices in protocol B was observed compared with protocol A (12 ± 8.8 mm versus 16.2 ± 13.6 mm, p = 0.07), which equated to lower mean thyroid organ dose in (3.28 ± 1.76 mGy versus 4.11 ± 3.11 mGy, p = 0.104).

CONCLUSION

The present audit indicates that incorporation of a lateral topogram into the CTPA protocol, together with radiographer education, reduces excess scan length, which significantly reduces the dose to the liver and stomach, and potentially lowers the dose to the thyroid. This simple dose-saving technique can be applied to all CT investigations of the chest on all CT systems with immediate effect.

Comparison of non-invasive diagnostic tests to multi-detector CT pulmonary angiography for the diagnosis of pulmonary embolism

CONTEXT

Acute pulmonary embolism (PE) remains a diagnostic and therapeutic challenge to physicians. There are various non-invasive diagnostic modalities been suggested to diagnose pulmonary embolism.

AIM

We tried to find the performance of various non-invasive investigations in comparison to multi-detector Computerized Tomography (MDCT pulmonary angiography for the diagnosis of PE).

SETTINGS AND DESIGN

A prospective cohort study was conducted in 80 hospitalized medical patients.

MATERIALS AND METHODS

There were 80 patients with Wells score > 2 who were included. The demographic data, non-invasive investigations, and MDCT pulmonary angiography were conducted in these patients. The sensitivity (SEN), specificity (SPE), positive predictive value (PPV), and negative predictive value (NPV) were calculated for each test.

RESULTS

Out of 80 patients, 77.5% patients were with Wells score 3-6 and 22.5% patients were with Wells score more than 6. The test with highest sensitivity was d-dimer (SEN - 90%, P = 0.091) followed by PAH on TTE (SEN - 83%, PPV - 86%, P = 0.006). The most specific test was ECG showing S1Q3T3 (SPE - 100%, P = 0.421), followed by Wells score > 6 (SPE - 91%, P = 0.211). There was no test with sensitivity and specificity more than 90%

CONCLUSION

In all patients with intermediate to high-risk probability MDCT pulmonary angiography is the most accurate test to diagnose PE and should be performed at the earliest. The combination of 2-dimensional ECHO and d-dimer can be used in patients with a high clinical suspicion of PE on pre-test probability where MDCT pulmonary angiography is not possible.

Diagnostic management of acute deep vein thrombosis and pulmonary embolism

Acute deep vein thrombosis (DVT) and pulmonary embolism (PE) represent two expressions of a similar clinical pathological process, often referred to as venous thromboembolism (VTE). It has long been recognized that, as clinical signs and symptoms of PE and DVT are not specific for the diagnosis, objective diagnosis in both patients presenting with leg symptoms and those with chest symptoms is mandatory. Since the last review on this subject in this journal in 2009, several large trials have been performed that shed new light on all aspects of the diagnostic management of suspected VTE, especially in the field of simplified clinical decision rules, age-dependent D-dimer cut-offs and magnetic resonance imaging. A literature search covering the period 2007-2012 was performed using the Medline/PubMed database to identify all relevant papers regarding the diagnostic management of acute PE and DVT. Established concepts and the latest evidence on this subject will be the main focus of this review.

Idiopathic pulmonary fibrosis complicated by acute thromboembolic disease: chest X-ray, HRCT and multi-detector row CT angiographic findings

Idiopathic pulmonary fibrosis (IPF) is a chronic diffuse interstitial disease characterized by a predominant reticular pattern of involvement of the lung parenchyma which can be well documented by High Resolution Computed Tomography (HRCT). While almost half of the patients with IPF may develop pulmonary arterial hypertension, the occurrence of superimposed acute thrombo-embolic disease is rare.We describe a case of an 87 yrs old female who was found to have IPF complicated by acute pulmonary thrombo-embolism during the clinical and radiological investigation of a rapidly worsening dyspnea. While chest x-ray findings were initially considered consistent with a congestive heart failure, a bed side echocardiography revealed findings suggestive of pulmonary arterial hypertension and right ventricular failure with enlargement of both right cavities and associated valvular regurgitations. An acute thrombo-embolic disease was initially ruled out by a perfusion lung scintigraphy and subsequently confirmed by contrast-enhanced multi-detector CT which showed an embolus at the emergency of the right inter-lobar artery with associated signs of chronic pulmonary hypertension. However, unenhanced scans performed with both conventional and high resolution techniques also depicted a reticular pattern of involvement of lung parenchyma considered suggestive of IPF despite a atypical upper lobe predominance. IPF was later confirmed by further clinical, serological and instrumental follow-up.

Medical emergencies: pulmonary embolism and acute severe asthma

In this, the second of two articles covering specific medical emergencies, we discuss the definitions, epidemiology, pathophysiology, acute and chronic management of pulmonary embolus and acute severe asthma.

Dual-energy CT of the lung

OBJECTIVE

The introduction of dual-energy CT (DECT) has ushered in the ability of material differentiation and tissue characterization beyond the traditional CT attenuation scale. This quality has been exploited for visualizing and quantifying the specific tissue content using radiographic contrast agents, such as iodine-based contrast media or inhaled xenon gas. Applications of this paradigm in the thorax include characterization of the pulmonary blood pool in the setting of acute or chronic pulmonary embolism (PE) and characterization of diseases of the lung parenchyma. Selective xenon detection is being explored for imaging of lung ventilation. In addition, the usefulness of DECT-based selective iodine uptake measurements has been described for the diagnosis and surveillance of thoracic malignancies. This article reviews the current applications of DECT-based imaging techniques in the chest with an emphasis on the diagnosis and characterization of pulmonary thromboembolic disorders.

CONCLUSION

DECT can provide both anatomic and functional information about the lungs in a variety of pulmonary disease states based on a single contrast-enhanced CT examination. This quality has been shown to improve the diagnosis of acute and chronic PEs, other vascular disorders, lung malignancies, and parenchymal diseases. Further developments in DECT techniques and CT scanner technology will further foster and enhance the utility of this application and open new avenues in lung imaging.

Short-term mortality in acute pulmonary embolism: clot burden and signs of right heart dysfunction at CT pulmonary angiography

PURPOSE

To assess the correlation between volumetric measurements of clot, semiquantitative clot burden indexes, and signs of right heart dysfunction at computed tomographic (CT) pulmonary angiography in patients with acute pulmonary embolism (PE) and to determine whether clot burden and signs of right heart dysfunction are associated with short-term mortality.

MATERIALS AND METHODS

This retrospective study was institutional review board approved and HIPAA compliant. CT pulmonary angiographic studies (January 2007 through December 2007) with findings positive for PE were retrieved. Two readers evaluated signs of right heart dysfunction at CT pulmonary angiography, measured clot volume using a dedicated software program, and assessed clot burden using semiquantitative scores (Qanadli and Mastora). Spearman rank coefficient was used to investigate correlation between clot burden measures and signs of right heart dysfunction. Uni- and multivariate analyses were used to test association between CT pulmonary angiographic findings and short-term mortality.

RESULTS

A total of 635 CT pulmonary angiographic studies from 635 patients (304 men, 331 women; mean age, 59 years) were included; 39 (6%) patients died within 30 days. Clot volume was strongly correlated with Qanadli score (ρ=0.841, P<.01) and Mastora score (ρ=0.863, P<.01) and moderately correlated (ρ=0.378, P<.01) with the ratio of right ventricle diameter to left ventricle diameter (RV/LV ratio). Among the pulmonary angiographic signs, only increase in RV/LV ratio (cut-off value, 1.0) was independently associated with short-term mortality in multivariate analysis.

CONCLUSION

Clot volume strongly correlated with semiquantitative CT scores of clot burden, and greater clot volume was associated with higher incidence of right heart dilatation. Increase in RV/LV ratio was associated with short-term mortality; however, measures of clot burden were not.

Thromboembolic complications in nephrotic syndrome: imaging spectrum

Thromboembolism is a well-known complication of nephrotic syndrome. Pulmonary embolism, renal vein thrombosis, and deep vein thrombosis are the most common venous thromboembolic diseases in patients with nephrotic syndrome, while arterial thromboembolic complications are observed less frequently. Imaging plays an important role in the detection and follow-up of thromboembolism in these patients. The purpose of this essay is to describe the epidemiology, pathophysiological mechanisms, the imaging diagnosis, and treatment of thromboembolism in patients with nephrotic syndrome.

Imaging of acute pulmonary embolism

Acute pulmonary thromboembolism (PE) is a cardiovascular emergency associated with significant morbidity and a 5-35 % mortality for untreated pulmonary embolism. If promptly diagnosed and treated, the mortality rate can be significantly reduced. Diagnosis of acute PE continues to be a clinical challenge, with diagnostic imaging playing an important role. This review discusses the clinical challenges of diagnosing acute PE, presents an evidence-based review of the current tests and ever-evolving imaging technology, and highlights special considerations related to radiation dose, contrast media use, and pregnant patients.

Low-dose radiation with 80-kVp computed tomography to diagnose pulmonary embolism: a feasibility study

BACKGROUND

Mounting collective radiation doses from computed tomography (CT) implies an increased risk of radiation-induced cancer in exposed populations, especially in the young.

PURPOSE

To evaluate radiation dose and image quality at 80-kVp CT to diagnose acute pulmonary embolism (PE) compared with a previous study at 100 and 120 kVp with all other scanning parameters unchanged.

MATERIAL AND METHODS

A custom-made chest phantom with a 12 mg I/mL-syringe was scanned at 80/100/120 kVp to evaluate relative changes in computed tomographic dose index (CTDI(vol)), attenuation, image noise, and contrast-to-noise ratio (CNR). Fifty patients underwent 80 kVp 16-row detector CT at 100 "Quality reference" mAs. A total of 350 mg I/kg were injected to compensate for increased CNR at 80 kVp, while 300 mg I/kg had been used at 100/120 kVp. CTDI(vol), dose-length product (DLP), and estimated effective dose were evaluated including Monte Carlo simulations. Pulmonary artery attenuation and noise were measured and CNR calculated. Two radiologists evaluated subjective image quality using a four-grade scale.

RESULTS

Switching from 120 to 80 kVp in the phantom study decreased radiation dose by 67% while attenuation and noise increased 1.6 and 2.0 times, respectively, and CNR decreased by 16%. Switching from 120 to 80 kVp in the patient studies decreased estimated effective dose from 4.0 to 1.2 mSv (70% decrease) in median while pulmonary artery attenuation and noise roughly doubled from 332 to 653 HU and from 22 to 49 HU, respectively, resulting in similar CNR (13 vs. 12). At 80 kVp all examinations were regarded as adequate (8%) or excellent (92%).

CONCLUSION

Switching from 120 to 80 kVp CT without increased mAs but slightly increased iodine dose may be of special benefit to diagnose PE in younger individuals with preserved renal function where the primary aim is to minimize radiation dose and reaching levels below that of scintigraphy.

Neonatal pulmonary artery thrombosis

Pulmonary artery thrombosis in neonates is a rare entity. We describe two neonates with this diagnosis; their presentation, evaluation, and management. These cases highlight the importance of this differential diagnosis when evaluating the cyanotic neonate.