From the Guidelines
MRI is not recommended as a first-line imaging test for diagnosing pulmonary embolism (PE), and CT pulmonary angiography (CTPA) remains the gold standard due to its high sensitivity and specificity, as stated in the NCCN Guidelines for Cancer-Associated Venous Thromboembolic Disease, Version 2.2024 1. The preferred imaging technique for the initial diagnosis of PE is CTA, which allows for indirect evaluation of pulmonary vessels, with advantages including accurate imaging of mediastinal and parenchymal structures, accurate visualization of emboli in many regions of the pulmonary vasculature, and ability to detect signs of right ventricular (RV) enlargement, which can be used in assessing risk for adverse clinical outcomes 1. Some key points to consider when evaluating PE diagnosis include:
- The most common presenting symptoms of PE are dyspnea, pain, and tachypnea, which were present in 85%, 40%, and 29% of patients with PE, respectively 1.
- Alternative imaging modalities used for the diagnosis of PE include X-ray pulmonary angiography with contrast, MR angiography with contrast, and ventilation-perfusion (VQ) scan if CTA is contraindicated 1.
- In specific situations where radiation exposure is a significant concern or when iodinated contrast is contraindicated, V/Q scanning is typically preferred over MRI 1, as supported by the 2014 ESC guidelines on the diagnosis and management of acute pulmonary embolism 1.
- The limited availability of MRI technology optimized for pulmonary vascular imaging and the need for specialized expertise in interpreting these studies further restricts its practical application for PE diagnosis in most clinical settings, as noted in the guidelines on the diagnosis and management of acute pulmonary embolism by the European Society of Cardiology (ESC) 1.
From the Research
MRI for Pulmonary Embolism (PE)
- The use of MRI for diagnosing pulmonary embolism is not as common as other imaging modalities like CT pulmonary angiography (CTPA) due to various factors including sensitivity and specificity 2.
- However, recent studies have explored the diagnostic accuracy of magnetic resonance (MR) sequences for displaying different levels of pulmonary artery involvement in pulmonary embolism (PE) 3.
- One study found that enhanced volume-interpolated body examination (VIBE) surpassed other MR sequences in revealing PE, particularly in segmental analysis, which is essential for emergency patients with contraindications for receiving iodinated contrast or concerns about ionizing radiation 3.
- Another study discussed the performance of contrast-enhanced pulmonary magnetic resonance angiography (MRA) for the diagnosis of PE as an effective non-ionizing alternative to contrast-enhanced computed tomography and nuclear medicine ventilation/perfusion scanning 4.
- The application of magnetic resonance angiography to detect acute pulmonary embolism and plan endovascular therapy has also been explored, offering an alternative for patients who are not candidates for CTPA 5.
Diagnostic Accuracy of MRI for PE
- The sensitivity and specificity of MRI for PE diagnosis vary depending on the sequence used, with VIBE showing the highest sensitivity and specificity in one study 3.
- The diagnostic performance of MRI sequences for PE detection has been compared to CTPA, which is considered the reference standard 3.
- The results suggest that MRI can be a useful diagnostic tool for PE, particularly in certain patient populations or when other imaging modalities are contraindicated 3, 4, 5.
Clinical Applications of MRI for PE
- MRI can be used as an alternative to CTPA for diagnosing PE in patients with contraindications to iodinated contrast or concerns about ionizing radiation 4, 5.
- The use of MRI for PE diagnosis can help reduce the burden of medical imaging radiation and maintain good patient outcomes 4.
- MRI can also aid in the planning of endovascular therapy for PE by visualizing the number and distribution of emboli and determining ideal intra-procedural catheter position for treatment 5.