Diagnosis of acute pulmonary embolism in outpatients: comparison of thin-collimation multi-detector row spiral CT and planar ventilation-perfusion scintigraphy

An overview of systematic reviews on imaging tests for diagnosis of pulmonary embolism applying different network meta-analytic methods

PURPOSE

This study aimed to apply different methods of diagnostic test accuracy network meta-analysis (DTA-NMA) for studies reporting results of five imaging tests for the diagnosis of suspected pulmonary embolism (PE): pulmonary angiography (PA), computed tomography angiography (CTPA), magnetic resonance angiography (MRA), planar ventilation/perfusion (V/Q) scintigraphy and single-photon emission computed tomography ventilation/perfusion (SPECT V/Q).

METHODS

We searched four databases (MEDLINE [via PubMed], Cochrane CENTRAL, Scopus, and Epistemonikos) from inception until June 2, 2022 to identify systematic reviews (SRs) describing diagnostic accuracy of PA, CTPA, MRA, V/Q scan and SPECT V/Q for suspected PE. Study-level data were extracted and pooled using a hierarchical summary receiver operating characteristic (HSROC) meta-regression approach and two DTA-NMA models to compare accuracy estimates of different imaging tests. Risk of bias was assessed using the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies-2) tool and certainty of evidence using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) framework.

RESULTS

We identified 13 SRs, synthesizing data from 33 primary studies and for four imaging tests (PA, CTPA, MRA and V/Q scan). The HSROC meta-regression model using PA as the reference standard showed that MRA had the best overall diagnostic performance with sensitivity of 0.93 (95% confidence interval [CI]: 0.76, 1.00) and specificity of 0.94 (95% CI: 0.84, 0.99). However, DTA-NMA models indicated that V/Q scan had the highest sensitivity, while CTPA was most specific.

CONCLUSION

Selecting a different DTA-NMA method to assess multiple diagnostic tests can affect estimates of diagnostic accuracy. There is no established method, but the choice depends on the data and familiarity with Bayesian statistics.

ACR Appropriateness Criteria® Suspected Pulmonary Embolism: 2022 Update

Pulmonary embolism (PE) remains a common and important clinical condition that cannot be accurately diagnosed on the basis of signs, symptoms, and history alone. The diagnosis of PE has been facilitated by technical advancements and multidetector CT pulmonary angiography, which is the major diagnostic modality currently used. Ventilation and perfusion scans remain largely accurate and useful in certain settings. MR angiography can be useful in some clinical scenarios and lower-extremity ultrasound can substitute by demonstrating deep vein thrombosis; however, if negative, further studies to exclude PE are indicated. In all cases, correlation with the clinical status, particularly with risk factors, improves not only the accuracy of diagnostic imaging but also overall utilization. Other diagnostic tests have limited roles. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer-reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances in which peer-reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Pediatric Pulmonary Embolism: Imaging Guidelines and Recommendations

In contrast with the algorithms and screening criteria available for adults with suspected pulmonary embolism, there is a paucity of guidance on the diagnostic approach for children. The incidence of pulmonary embolism in the pediatric population and young adults is higher than thought, and there is an urgent need for updated guidelines for the imaging approach to diagnosis in the pediatric population. This article presents an up-to-date review of imaging techniques, characteristic radiologic findings, and an evidence-based algorithm for the detection of pediatric pulmonary embolism to improve the care of pediatric patients with suspected pulmonary embolism.

Acute pulmonary embolism multimodality imaging prior to endovascular therapy

The manuscript discusses the application of CT pulmonary angiography, ventilation–perfusion scan, and magnetic resonance angiography to detect acute pulmonary embolism and to plan endovascular therapy. CT pulmonary angiography offers high accuracy, speed of acquisition, and widespread availability when applied to acute pulmonary embolism detection. This imaging modality also aids the planning of endovascular therapy by visualizing the number and distribution of emboli, determining ideal intra-procedural catheter position for treatment, and signs of right heart strain. Ventilation–perfusion scan and magnetic resonance angiography with and without contrast enhancement can also aid in the detection and pre-procedural planning of endovascular therapy in patients who are not candidates for CT pulmonary angiography.

Radiologist Performance in the Detection of Pulmonary Embolism: Features that Favor Correct Interpretation and Risk Factors for Errors

PURPOSE

This study aimed to assess the factors contributing toward accurate detection and erroneous interpretation of pulmonary embolism (PE).

MATERIALS AND METHODS

Over 13 months, all computed tomography pulmonary angiography studies were retrospectively rereviewed by a chest radiologist. Two additional chest radiologists assessed cases with disagreement between the first interpretation and rereview. The number, extent, and location of PE and specialty training, experience, time of study, kV, resident prelim, use of iterative reconstruction, signal to noise ratio (SNR), and reports describing the study as "limited" were recorded. Parametric and nonparametric statistical testing was performed (significance P<0.05).

RESULTS

Of 2555 computed tomography pulmonary angiography cases assessed, there were 230 true positive (170 multiple, 60 single PE), 2271 true negative, 35 false-negative (15 multiple and 20 single PE), and 19 false-positive studies. The overall sensitivity, specificity, positive predictive value, negative predictive value and accuracy of radiologists was 86.8%, 99.2%, 92.4%, 98.5%, and 97.9%. Sensitivity for the detection of multiple and central PE was significantly higher than the detection of single and peripheral PE, respectively (P<0.01 for both). The sensitivity of thoracic radiologists (91.7%) was higher than nonthoracic (82.8%) and reached significance for single PE (89.2% vs. 61.4%, P<0.02). Errors were more likely in cases with lower SNR (P=0.04) and those described as limited (P<0.001). Misses occurred more frequently in the upper lobe posterior and lower lobe lateral segments and subsegments (P=0.038).

CONCLUSIONS

The accuracy for PE detection is high, but errors are more likely in studies with single PE interpreted by nonthoracic radiologists, especially when located in certain segments and in cases with low SNR or described as limited.

ACR Appropriateness Criteria® Acute Chest Pain-Suspected Pulmonary Embolism

Pulmonary embolism (PE) remains a common and important clinical condition that cannot be accurately diagnosed on the basis of signs, symptoms, and history alone. The diagnosis of PE has been facilitated by technical advancements and multidetector CT pulmonary angiography, which is the major diagnostic modality currently used. Ventilation and perfusion scans remain largely accurate and useful in certain settings. Lower-extremity ultrasound can substitute by demonstrating deep vein thrombosis; however, if negative, further studies to exclude PE are indicated. In all cases, correlation with the clinical status, particularly with risk factors, improves not only the accuracy of diagnostic imaging but also overall utilization. Other diagnostic tests have limited roles. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer-reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Optimization of image quality in pulmonary CT angiography with low dose of contrast material

Aim: The aim of this study was to compare objective image quality data for patient pulmonary embolism between a conventional pulmonary CTA protocol with respect to a novel acquisition protocol performed with optimize radiation dose and less amount of iodinated contrast medium injected to the patients during PE scanning. Materials and Methods: Sixty- four patients with Pulmonary Embolism (PE) possibility, were examined using angio-CT protocol. Patients were randomly assigned to two groups: A (16 women and 16 men, with age ranging from 19-89 years) mean age, 62 years with standard deviation 16; range, 19-89 years) - injected contrast agent: 35-40 ml. B (16 women and 16 men, with age ranging from 28-86 years) - injected contrast agent: 70-80 ml. Other scanning parameters were kept constant. Pulmonary vessel enhancement and image noise were quantified; signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. Subjective vessel contrast was assessed by two radiologists in consensus. Result: A total of 14 cases of PE (22 %) were found in the evaluated of subjects (nine in group A, and five in group B). All PE cases were detected by the two readers. There was no significant difference in the size or location of the PEs between the two groups, the average image noise was 14 HU for group A and 19 HU for group B. The difference was not statistically significant (p = 0.09). Overall, the SNR and CNR were slightly higher on group B (24.4 and 22.5 respectively) compared with group A (19.4 and 16.4 respectively), but those differences were not statistically significant (p = 0.71 and p = 0.35, respectively). Conclusion and Discussion: Both groups that had been evaluated by pulmonary CTA protocol allow similar image quality to be achieved as compared with each other’s, with optimize care dose for both protocol and contrast volume were reduced by 50 % in new protocol comparing to the conventional protocol.

SPECT-CT/VQ versus CTPA for diagnosing pulmonary embolus and other lung pathology: Pre-existing lung disease should not be a contraindication

INTRODUCTION

Single Photon Emission Computed Tomography-Ventilation-Perfusion (SPECT-VQ) with low-dose CT (SPECT-CT/VQ) has equivalent diagnostic accuracy to CTPA for diagnosing pulmonary embolus (PE) while using lower radiation doses, but is underutilized owing to perceived inaccuracy of scintigraphy in the setting of pre-existing lung disease. This study assesses the accuracy of SPECT-CT/VQ compared with CTPA for the diagnosis of PE, including in patients with pre-existing lung disease.

METHODS

Retrospective non-inferiority cohort study of all patients who underwent SPECT-CT/VQ scanning at St Vincent's Hospital, NSW, from June 2012 to November 2013, who also had a CTPA within the same admission and <72 h apart (n = 102).

RESULTS

SPECT-CT/VQ had 100% sensitivity and 94.4% specificity when compared with CTPA. Of the 102 patients, 14 were lung transplant patients, and 27 had other pre-existing lung disease (41/102, 40.2%), with SPECT-CT/VQ having a sensitivity of 100% and specificity of 97.2% in this patient group. Non-inferiority of SPECT-CT/VQ was demonstrated at a significance level of 0.005.

CONCLUSION

SPECT-CT/VQ has high sensitivity and specificity for diagnosing PE compared with CTPA, even among patients with pre-existing lung disease, with lower radiation doses.

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.

Contribution of V/Q SPECT to planar scintigraphy in the diagnosis of pulmonary embolism

AIM

To evaluate the feasibility of V/Q SPECT and analyze its contribution to planar V/Q lung scintigraphy in the diagnosis of pulmonary embolism (PE).

MATERIAL AND METHODS

A total of 109 patients with suspected PE showing Wells score>2 and elevated D-dimer were studied. The V/Q could not be completed in 7 patients, so they were excluded. Ventilation and perfusion scans were done using Technegas and (99m)Tc-MAA. Planar study included 8 projections on a 256×256 matrix and 128 projections on a 128×128 matrix were acquired for the SPECT study, applying an iterative method. Planar images were interpreted according to modified PIOPED criteria, and SPECT by the guidelines of the EANMMI. The results with both techniques were compared.

RESULTS

V/Q planar scintigraphy and SPECT could be performed in 102 patients. V/Q planar scintigraphy was considered "diagnostic" in 39 of the 102 patients, and "non-diagnostic" in 63. Of the 39 "diagnostic" studies, 31 were reported as high probability of PE and 8 as normal. Of the 63 "non-diagnostic", 26 corresponded to intermediate, 29 to low, and 8 to very low probability. The SPECT study was "diagnostic" in 97 and indeterminate in only 5. All patients with a high probability planar scintigraphy had a positive SPECT. In the 8 patients with a normal planar scintigraphy SPECT was negative in 5 and positive in 3. In the 63 patients with a "non-diagnostic" planar scintigraphy SPECT was "diagnostic" in 58 of them, positive in 17 and negative in 41.

CONCLUSION

V/Q SPECT is a feasible technique as it was performed in 102 of the 109 patients who were enrolled in the study (94%). The addition of V/Q SPECT to planar V/Q decreases the number of "non-diagnostic" reports from 62% in planar scintigraphy to 4.9% in SPECT. Therefore, V/Q SPECT should be included in the diagnosis approach of PE due to its high diagnostic yield.

Imaging diagnosis of acute pulmonary embolism

Pulmonary embolism represents a major public healthcare problem and it also imposes frequent clinical diagnostic issues. Despite the availability of the D-dimer tests, imaging remains the mainstay for its diagnosis. Computed tomography pulmonary angiography (CTPA) is now the most widely used diagnostic test and its utility has been well validated in a large number of trials. Nuclear medicine techniques, which are also well established, are now used significantly less frequently. Magnetic resonance pulmonary angiography is developing as an alternative to CTPA in patients who have contraindications to iodinated contrast media. Catheter pulmonary angiography remains the gold standard, although it is being used increasingly less frequently. In this article, we review the current knowledge on the imaging diagnosis of acute pulmonary embolism with special emphasis on the noninvasive techniques.

SPECT/CT and pulmonary embolism

Acute pulmonary embolism (PE) is diagnosed either by ventilation/perfusion (V/P) scintigraphy or pulmonary CT angiography (CTPA). In recent years both techniques have improved. Many nuclear medicine centres have adopted the single photon emission CT (SPECT) technique as opposed to the planar technique for diagnosing PE. SPECT has been shown to have fewer indeterminate results and a higher diagnostic value. The latest improvement is the combination of a low-dose CT scan with a V/P SPECT scan in a hybrid tomograph. In a study comparing CTPA, planar scintigraphy and SPECT alone, SPECT/CT had the best diagnostic accuracy for PE. In addition, recent developments in the CTPA technique have made it possible to image the pulmonary arteries of the lungs in one breath-hold. This development is based on the change from a single-detector to multidetector CT technology with an increase in volume coverage per rotation and faster rotation. Furthermore, the dual energy CT technique is a promising modality that can provide functional imaging in combination with anatomical information. Newer high-end CT scanners and SPECT systems are able to visualize smaller subsegmental emboli. However, consensus is lacking regarding the clinical impact and treatment. In the present review, SPECT and SPECT in combination with low-dose CT, CTPA and dual energy CT are discussed in the context of diagnosing PE.

Cancer survivorship, a unique and growing cohort in medical practice: radiology perspective

The unique medical and psychologic burdens of cancer survivorship have only recently been recognized. This rapidly expanding cohort of patients will be seen increasingly by non-oncology physicians who must consider medical issues related to their cancer or its therapy for any presenting symptoms. Appropriate use of clinical imaging is essential for diagnosing treatment-related complications, recurrent tumor, or emergence of second primaries. This article will review clinical imaging in common medical problems uniquely found in cancer survivors.

Dynamic computed tomographic pulmonary angiography as a problem-solving tool in indeterminate computed tomographic angiography for pulmonary embolism

OBJECTIVE

Computed tomographic pulmonary angiography may be indeterminate in regions of slow arterial flow because of underlying lung disease. In this case, dynamic computed tomographic angiography of the pulmonary vasculature (dynamic CTPA) was used to confirm flow variation within the pulmonary arteries in regions of pulmonary fibrosis and excluded pulmonary embolism.

CONCLUSIONS

Dynamic CTPA successfully demonstrates flow variation within the pulmonary arteries and may be a useful adjunct to exclude pulmonary embolism in CTPA cases with questionable arterial filling defects.

Critical issues in the evaluation and management of adult patients presenting to the emergency department with suspected pulmonary embolism

This clinical policy from the American College of Emergency Physicians is the revision of a 2003 clinical policy on the evaluation and management of adult patients presenting with suspected pulmonary embolism (PE).(1) A writing subcommittee reviewed the literature to derive evidence-based recommendations to help clinicians answer the following critical questions: (1) Do objective criteria provide improved risk stratification over gestalt clinical assessment in the evaluation of patients with possible PE? (2) What is the utility of the Pulmonary Embolism Rule-out Criteria (PERC) in the evaluation of patients with suspected PE? (3)What is the role of quantitative D-dimer testing in the exclusion of PE? (4) What is the role of computed tomography pulmonary angiogram of the chest as the sole diagnostic test in the exclusion of PE? (5) What is the role of venous imaging in the evaluation of patients with suspected PE? (6) What are the indications for thrombolytic therapy in patients with PE? Evidence was graded and recommendations were given based on the strength of the available data in the medical literature.

Incremental value of CT venography combined with pulmonary CT angiography for the detection of thromboembolic disease: systematic review and meta-analysis

OBJECTIVE

The objective of our study was to assess the incremental role of CT venography (CTV) combined with pulmonary CT angiography (CTA) in detecting venous thromboembolic disease with a systematic review and meta-analysis of the literature.

MATERIALS AND METHODS

MEDLINE, Embase, and Web of Science were searched for relevant original articles published from January 1, 1995, to December 31, 2009. A random-effects model was used to obtain the incremental value of CTV in detecting thromboembolic disease.

RESULTS

Twenty-four studies, which included 17,373 patients, met our inclusion criteria. A meta-analysis showed that CTV increased detection rates of venous thromboembolic disease by identifying an additional 3% of cases (95% CI, 2-4%) of isolated deep venous thrombosis (DVT). A subgroup analysis of a high-risk group did not show any difference in the detection of isolated DVT.

CONCLUSION

The addition of CTV results in the increased detection of thromboembolic disease. CTV combined with pulmonary CTA has a promising role as a quick and efficient test for venous thromboembolism.

Venous thromboembolism: deep venous thrombosis and pulmonary embolism in a neurosurgical population

Object

Venous thromboembolism (VTE), a combination of deep venous thrombosis (DVT) and pulmonary embolism (PE), is a major cause of morbidity and death in neurosurgical patients. This study evaluates 1) the risk of developing lower-extremity DVT following a neurosurgical procedure; 2) the timing of initiation of pharmacological DVT prophylaxis upon the occurrence of VTE; and 3) the relationship between DVT and PE as related to VTE prophylaxis in neurosurgical patients.

Methods

The records of all neurosurgical patients between January 2006 and December 2008 (2638 total) were reviewed for clinical documentation of VTE. As part of a quality improvement initiative, a subgroup of 1638 patients was studied during the implementation of pharmacological prophylaxis. A high-risk group of 555 neurosurgical patients in the intensive care unit underwent surveillance venous lower-extremity duplex ultrasonography studies twice weekly. All patients throughout the review received mechanical DVT prophylaxis. Pharmacological DVT prophylaxis, consisting of 5000 U of subcutaneous heparin twice daily (initially started within 48 hours of a neurosurgical procedure and subsequently within 24 hours of a procedure) was implemented in combination with mechanical prophylaxis. The DVT and PE rates were calculated for each group.

Results

In the surveillance group (555 patients), 84% of the DVTs occurred within 1 week and 92% within 2 weeks of a neurosurgical procedure. There was a linear correlation between the duration of surgery and DVT development. The use of subcutaneous heparin reduced the rate of DVT from 16% to 9% when medication was given at either 24 or 48 hours postoperatively, without any increase in hemorrhagic complications. In the overall group (2638 patients), there were 94 patients who exhibited clinical signs of a possible PE and therefore underwent spiral CT; 22 of these patients (0.8%) had radiological confirmation of PE. There was no correlation between the use of pharmacological prophylaxis at either time point and the occurrence of PE, despite a 43% reduction in the lower-extremity DVT rate with pharmacological intervention.

Conclusions

The majority of DVTs occurred within the first week after a neurosurgical procedure. There was a linear correlation between the duration of surgery and DVT occurrence. Use of early subcutaneous heparin (at either 24 or 48 hours) was associated with a 43% reduction of developing a lower-extremity DVT, without an increase in surgical site hemorrhage. There was no association of pharmacological prophylaxis with overall PE occurrence.

Update on techniques for the diagnosis of pulmonary embolism

IMPORTANCE OF THE FIELD

The clinical suspicion of acute pulmonary embolism (PE) is frequently raised. However, the diagnosis of PE is confirmed in only 20 - 30% of these patients. The high incidence in addition to the potential harm from false-positive or false-negative diagnostic decisions underline the importance of a standardised diagnostic algorithm with high sensitivity as well as specificity.

AREAS COVERED IN THIS REVIEW

This article reviews the diagnostic tests for the diagnosis of PE.

WHAT THE READER WILL GAIN

This review provides an overview of the different clinical decision rules (CDRs), D-dimer tests and imaging techniques in patients suspected of PE. Furthermore, the diagnostic process in patients with clinically suspected recurrent PE, suspicion during pregnancy and new research areas are discussed.

TAKE HOME MESSAGE

Various diagnostic tests are available to detect or exclude PE with good accuracy. CDRs and D-dimer tests play an important role in the exclusion of PE. Neither is sufficient as a single test, but the combination of an 'unlikely' clinical prediction and a normal D-dimer test result safely excludes PE. In case of a high CDR score and/or an elevated D-dimer concentration, extra imaging is necessary with multi-slice computed tomography pulmonary angiography as first choice modality.

Chest multidetector computed tomography (MDCT) in patients with suspected acute pulmonary embolism: diagnostic yield and proportion of other clinically relevant findings

PURPOSE

The authors evaluated the diagnostic yield of chest multidetector computed tomography (MDCT) in acute pulmonary embolism (PE) and the proportion of other clinically relevant findings in a large cohort of consecutive inpatients and patients referred from the emergency department (outpatients).

MATERIALS AND METHODS

A total of 327 radiological reports of chest MDCT scans performed for suspected acute PE in 327 patients (158 men, 169 women; mean age 69 years, standard deviation 17.33 years; 233 inpatients, 94 outpatients) were retrospectively evaluated and classified into four categories: 1, positive for PE; 2, negative for PE but positive for other findings requiring specific and immediate intervention; 3, completely negative or positive for findings with a potential for significant morbidity requiring specific action on follow-up; 4, indeterminate. The distribution of findings by categories among the entire population and inpatients and outpatients separately was calculated (chi-square test, α=0.05).

RESULTS

In the entire population, the diagnostic yield (i.e. proportion of cases classified as category 1) was 20.2% (66/327). Proportions of cases classified as categories 2, 3 and 4 were 27.5% (90/327), 44.3% (145/327) and 7.9% (26/327), respectively. No statistically significant difference was found between inpatients and outpatients (p=0.193).

CONCLUSIONS

In patients with suspected acute PE, chest MDCT provides evidence of conditions requiring immediate and specific intervention (i.e. categories 1 and 2) in nearly 50% of cases, without differences between inpatients and outpatients.