Value of negative spiral CT angiography in patients with suspected acute PE: analysis of PE occurrence and outcome

Image Quality of Iodine Maps for Pulmonary Embolism: A Comparison of Subtraction CT and Dual-Energy CT

OBJECTIVE. The objective of this study was to compare the image quality of iodine maps derived from subtraction CT and from dual-energy CT (DECT) in patients with suspected pulmonary embolism (PE). SUBJECTS AND METHODS. In this prospective study conducted between July 2016 and April 2017, consecutive patients with suspected PE underwent unenhanced CT at 100 kV and dual-energy pulmonary CT angiography at 100 and 140 kV on a dual-source scanner. The scanner was set to generate subtraction and DECT iodine maps at similar radiation doses. In 55 patients (30 women, 25 men; mean age ± SD, 63.4 ± 11.9 years old), various subjective image quality criteria including diagnostic acceptability were rated on a 5-point scale by four radiologists and a radiology resident. In 29 patients (17 women, 12 men; mean age, 62.4 ± 11.7 years old) with confirmed perfusion defects, the signal-difference-to-noise ratio (SDNR) between perfusion defects and adjacent normally perfused parenchyma was measured in corresponding ROIs on subtraction and DECT iodine maps. McNemar and Wilcoxon signed-rank tests were used for statistical comparisons. RESULTS. Diagnostic acceptability was rated excellent or good in a mean of 67% (range, 31-80%) of subtraction CT studies and 36% (5-69%) of DECT studies (p < 0.05 for four of the five radiologists), mainly because of fewer artifacts on subtraction CT. Mean SDNR was marginally higher for subtraction CT than for DECT (18.6 vs 17.1, p = 0.06) and was significantly higher in the upper lobes (21.8 vs 17.9, p < 0.05). CONCLUSION. Radiologist-judged image quality of pulmonary iodine maps was higher for subtraction CT than for DECT with similar to higher SDNR. Subtraction CT is a software-only solution, so it may be an attractive alternative to DECT for depicting perfusion defects.

Clinical consequences of an indeterminate CT pulmonary angiogram in cancer patients

Our aim was to evaluate clinical management and outcomes in cancer patients who had an indeterminate Computed Tomographic Pulmonary Angiogram (CTPA) for the assessment of pulmonary embolus. We reviewed 1000 CTPA studies and identified 251 limited (indeterminate) CTPA. We examined follow-up imaging and reviewed clinical management decisions and any positive diagnosis of venous thromboembolic disease (VTE) within the subsequent 90 days. 60 patients (23.9%) had a follow-up imaging study within five days. 8 had a positive study for VTE disease within 5 days. 3 patients (1.2%) were placed on anticoagulation therapy based on the limited CT result.

Four-year cumulative radiation exposure in patients undergoing computed tomography angiography for suspected pulmonary embolism

Purpose. The objective of this study was to determine the estimated effective radiation dose of pulmonary CT angiography (CTA) for suspected pulmonary embolism (PE) contributing to total medical radiation exposure over a 4-year period. Materials and Methods. This investigation retrospectively reviewed 300 patients who presented to the emergency department and received a pulmonary CTA scan for suspected PE. We evaluated these patients' electronic medical record to determine their estimated radiation exposure to CT scans during the following four years. Using DLP to E conversion coefficients, we calculated the cumulative effective radiation dose each subject received. Results. A total of 900 CT scans were reviewed in this study. Pulmonary CTA delivered an average effective radiation dose of 10.7 ± 2.5 mSv and accounted for approximately 65% of subjects' 4-year cumulative medical radiation dose. Only 6.3% of subjects had a positive acute PE according to their radiology report. Conclusion. Pulmonary CTA accounted for the majority of subjects' medically related effective radiation dose over a 4-year period. With only a minority of subjects having positive findings for acute PE, increased efforts should be made to clinically assess pretest probability before the consideration of imaging.

Clinical outcomes in patients with isolated subsegmental pulmonary emboli diagnosed by multidetector CT pulmonary angiography

INTRODUCTION

CT Pulmonary Angiography has been shown to be equivalent to Ventilation/ Perfusion scanning in 3-month outcome studies, but it detects more pulmonary emboli. Isolated subsegmental pulmonary emboli are thought to account for some of the increase in diagnosis, but it is not known whether these emboli represent a harbinger for future thromboembolic events. The objective of this study was to determine the 3-month clinical outcomes of a cohort of patients diagnosed with isolated subsegmental pulmonary emboli.

MATERIALS AND METHODS

Review of 10,453 consecutive CTPA radiology reports over 74-month period since the implementation of Multidetector CT Pulmonary Angiography identified a cohort of 93 patients found to have acute pulmonary embolism isolated to subsegmental pulmonary arteries without other evidence of deep venous thrombosis at one institution. The study measured 3-month clinical outcomes (anticoagulation use, recurrence, death, hemorrhage) determined by review of records and telephone interviews with physicians.

RESULTS

Seventy-one patients (76%) were treated with anticoagulation and/or IVC filter, while 22 (24%) were observed without therapy. One patient (1/93, 1.05%; 95% CI: 0-6.6%) who was treated with anticoagulants and a vena caval filter had a recurrent subsegmental pulmonary embolus. No patients died of pulmonary embolism. There were 8 hemorrhages, including 5 (5.3%) major hemorrhages without any hemorrhage-related mortality.

CONCLUSIONS

Patients diagnosed with isolated subsegmental pulmonary emboli have favorable 3-month outcomes. Short-term prognosis for recurrent thromboembolism may be lower than the risk of adverse events with anticoagulation in patients at high risk of hemorrhage.

CTPA as the gold standard for the diagnosis of pulmonary embolism

PURPOSE

The estimated annual incidence of pulmonary embolism (PE) is between 69 to 205 cases per 100,000 persons-years. New imaging studies have been developed during the past decade. Chest CTPA, especially multidetector CT, has proven to be superior or equal to PA angiography, even detecting smaller filling defects. We reviewed the differences in opinion to the diagnosis of PE between chest radiologists (CR) who interpret CTPA and interventional radiologists (IR) who perform PA angiography and what they consider the "gold standard" for the diagnosis of PE.

METHODS

Two surveys were designed, one for chest radiologists and one for interventional radiologists. An e-mail survey was sent to the members of the Society of Thoracic Radiology and the Society of Interventional Radiologists.

RESULTS

IR with < 10 years since finishing training were less likely to consider CTPA the gold standard, OR 0.45 (0.2-0.9). CR with < 10 years since finishing training were more likely to consider CTPA the gold standard, OR 2.0 (1.1-3.9). Most IR performed < 5 PA angiographies in the last 2 years (69%). CR considered CTPA the gold standard for the diagnosis of PE, OR 3.3 (1.8-6.1). Binary logistic regression analysis for both groups demonstrated that the only variable associated with CTPA as gold standard for the diagnosis of PE was being a chest radiologist.

CONCLUSION

The majority of the radiologists surveyed indicated that CTPA is the new reference standard for the diagnosis of pulmonary embolism. We agree with this statement based on the evidence available at this time.

Computed tomography pulmonary angiography: an assessment of the radiology report

RATIONALE AND OBJECTIVE

The aim of this study was to evaluate the uncertainty in computed tomographic pulmonary angiography (CTPA) radiology reports, manifested by descriptions of report limitations and image quality.

MATERIALS AND METHODS

CTPA reports between 2004 and 2006 were reviewed for patient demographic data (age, gender, pregnancy state), radiologist data (years of experience, subspecialty, final dictation by an attending radiologist vs a resident being present and dictating the report), the presence of pulmonary embolism (PE), and key words describing examination quality and limitations.

RESULTS

There were 2151 CTPA reports. Patterns of reporting CTPA in the impression sections of radiology reports were as follows: (1) PE conclusively positive (10%), (2) PE conclusively negative (29%), (3) PE negative to segmental arteries (27%), (4) PE negative to central pulmonary arteries (21%), (5) PE negative but suboptimal examination (8%), and (6) nondiagnostic examination (5%). Among the last three categories, seven PEs were not initially diagnosed but were found on subsequent imaging examinations. Limitations in image quality, respiratory motion artifact, and contrast enhancement were most frequently mentioned as limitations in image quality (62% and 28% of all reports, respectively). Radiologists tended to report limitations in image quality if they were thoracic radiology subspecialists, had >10 years of experience, or worked independently (P < .001).

CONCLUSION

Different patterns of reporting CTPA exist and vary on the basis of individual radiologists' subspecialties, experience, and whether they work independently or with residents. Certain wording regarding the presence of PE may falsely imply negativity of PE in a limited examination.

Clinically suspected acute pulmonary embolism: a comparison of presentation, radiological features and outcome in patients with and without PE

BACKGROUND

Relatively little is known about prognosis in patients for whom suspected pulmonary embolism (PE) is refuted by imaging.

AIM

This prospective study of suspected PE therefore compared clinico-radiological features and outcome in patients with and without PE.

DESIGN AND METHODS

Computed tomographic pulmonary angiography (CTPA) confirmed or refuted PE in consecutive patients. Clinical, laboratory and radiological features were recorded at baseline, and mortality at 1 year determined. Univariate and multivariate analyses identified variables associated with PE.

RESULTS

PE was diagnosed in 45 patients and refuted in 141. The PE and 'non-PE' groups were similar with regard to extravascular radiology (though consolidation was significantly more common in the PE group [present in 24 (53%) of the PE group and 42 (30%) of the non-PE group, P < 0.01)], comorbidities (no significant differences), and baseline characteristics (only serum D-dimer concentrations were independently associated with PE by multivariate analysis, P = 0.001). Right ventricular dimensions were significantly higher in the PE group, [right ventricular to left ventricular ratio was 0.98 (range 0.64-2.48) in the PE group and 0.92 (range 0.66-1.95) in the non-PE group, P < 0.05]. In the PE group, right ventricular dimensions rose sharply when 10 or more segmental pulmonary arteries were occluded. One year all-cause mortality was 6.7% in the PE group and 13.5% in the non-PE group (no significant difference, P = 0.218).

CONCLUSION

Among a cohort of patients presenting with clinically suspected PE, clinical characteristics, co-morbidities and radiological features were similar when comparing groups with CTPA-proven or CTPA-refuted PE. However RV dimensions, radiological consolidation on imaging and D-dimer levels were significantly higher in the PE group. Patients with suspected PE have a poor prognosis irrespective of whether PE is confirmed. This appears accentuated in patients without PE, a finding possibly under-recognized in clinical practice.

The role of multidetector computed tomography angiography for the diagnosis of pulmonary embolism

From a radiological point of view, computed tomography pulmonary angiography (CTPA) has effectively become the de-facto first-line imaging test for the evaluation of pulmonary embolism (PE), as patients with a high-quality negative CTPA do not require further examination or treatment for suspected PE. We are likely to see further technical developments in CT technology in the near future. These advances will most likely further improve image quality. Several questions or issues remain, including strategies for further imaging when CT is inconclusive or contraindicated, issues regarding radiation exposure, the prevalence of PE in specific populations, best tests and pathways in specific patient groups, including patients with specific comorbidities such as oncology patients or patients with chronic obstructive pulmonary disease. Also, the question whether all PE patients need anticoagulation, the clinical effect of follow-up imaging, and the accuracy of different clinical prediction rules, remains.

MDCT of acute thrombotic and nonthrombotic pulmonary emboli

Acute pulmonary embolism (PE) remains a common clinical challenge. MDCT pulmonary angiography has become the first line imaging study in the diagnosis of PE because of its speed, accuracy, low-interobserver variability, and ability to provide alternative diagnoses. This review article highlights the role of MDCT in the evaluation of acute thrombotic PE in the era of PIOPED 2. MDCT findings of acute PE and some potential pitfalls are covered as well as some of the controversies in imaging young and pregnant patients. MDCT findings of acute non-thrombotic PE are also covered. This latter group may be occult on the angiographic portion of the study but may declare themselves through secondary findings. Their findings and potential mimics are included so that the interpreting radiologist can make the most of a CT to rule out PE.

Gadolinium-enhanced pulmonary magnetic resonance angiography in the diagnosis of acute pulmonary embolism: a prospective study on 48 patients

OBJECTIVE

Gadolinium-enhanced pulmonary magnetic resonance angiography (MRA) can be an option in patients with a history of previous adverse reaction to iodinated contrast material and renal insufficiency. Radiation is also avoided. The aim of this study is to prospectively compare the diagnostic value of MRA with that of a diagnostic strategy, taking into account catheter angiography, computed tomography angiography (CTA), and lung scintigraphy [ventilation-perfusion (VQ)].

MATERIAL AND METHODS

Magnetic resonance angiography was done in 48 patients with clinically suspected pulmonary embolism (PE) using fast gradient echo coronal acquisition with gadolinium. Interpretation was done with native coronal images and multiplanar maximum intensity projection reconstructions. Results were compared to catheter angiography (n=15), CTA (n=34), VQ (n=45), as well as 6-12 months clinical follow-ups, according to a sequenced reference tree.

RESULTS

The final diagnosis of PE was retained in 11 patients (23%). There were two false negatives and no false positive results with MRA. Computed tomography angiography resulted in no false negatives or false positives. Magnetic resonance angiography had a sensitivity of 82% and a specificity of 100%.

CONCLUSION

In our study, pulmonary MRA had a sensitivity of 82% and a specificity of 100% for the diagnosis of PE, with slightly less sensitivity than CTA. In the diagnostic algorithm of PE, pulmonary MRA should be considered as an alternative to CTA when iodine contrast injection or radiation is a significant matter.

Helical CT for the Evaluation of Acute Pulmonary Embolism

OBJECTIVE

In this article, we review the current role of CT pulmonary angiography and indirect CT venography for the evaluation of pulmonary thromboembolic disease.

CONCLUSION

With advances in MDCT technology, evaluation of pulmonary thromboembolic disease can now be performed with combined CT pulmonary angiography and CT venography as a "one-stop-shopping" test. CT pulmonary angiography is cost-effective, is accurate, has high interobserver agreement, and has an added advantage of detecting other life-threatening diseases in the chest that mimic pulmonary embolism.

Computed Tomography Angiography

Multidetector-row computed tomography (MDCT) is an essential diagnostic modality for many clinical algorithms. This is particularly true with regard to the evaluation of cardiovascular disease. As a result of increased image acquisition speed, improved spatial resolution, and greater scan volume, MDCT angiography (computed tomography angiography [CTA]) has become an excellent noninvasive imaging technique, replacing intra-arterial digital subtraction angiography for most vascular territories. The clinical success of CTA depends on precise synchronization of image acquisition with optimal vascular enhancement. As technology continuously evolves, however, this task can be challenging. It remains important to have a fundamental knowledge of the principles behind technical parameters and contrast medium administration. This article reviews these essential principles, followed by an overview of current clinical applications.