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Diagnosis of peripheral pulmonary emboli by MR imaging: an experimental study in dogs
1Department of Radiological Sciences, University of California, School of Medicine, Los Angeles 90024.
Abstract:
The peripheral pulmonary arteries of 5 dogs were embolized with boiled autologous clots via the external right jugular vein. Angiography determined the location and approximate size of the emboli in the peripheral pulmonary arteries. With spin echo techniques, transverse axial magnetic resonance (MR) images (0.3 T, 12.77 MHz) were obtained in each animal from apex to thorax base, on a permanent magnet scanner. The sensitivity of MR imaging was assessed to detect these clots and to determine their size and location. In 2 dogs, scans were also obtained before embolization in order to exclude possible artifactual areas of increased signal. Fourteen out of 19 emboli were identified on the MR scans as areas of increased signal. Their diameter measured a minimum of 2.7 mm matching the filling defects seen on the angiograms. There were three false positive emboli on MR probably related to slow blood flow in the inferior vena cava. There were 9 false negative emboli on MR. The increased MR signal seen in dogs with pulmonary emboli results from the embolus itself and from slow blood flow distal to the obstructive embolus.
Insights
Magnetic resonance (MR) imaging can detect pulmonary emboli in dogs, identifying clot location and size. However, MR imaging showed false positives and negatives, indicating limitations in diagnosing these clots.
Area of Science:
- Veterinary Radiology
- Cardiovascular Imaging
- Pulmonary Embolism Research
Background:
- Pulmonary embolism (PE) is a critical condition affecting pulmonary arteries.
- Accurate detection of PE is essential for timely and effective treatment.
- Magnetic resonance (MR) imaging offers a non-invasive approach to visualize vascular structures.
Purpose of the Study:
- To assess the sensitivity and specificity of MR imaging in detecting peripheral pulmonary artery emboli in dogs.
- To evaluate the accuracy of MR imaging in determining the size and location of pulmonary emboli.
- To understand the MR signal characteristics associated with pulmonary emboli.
Main Methods:
- Peripheral pulmonary arteries in 5 dogs were embolized with autologous clots.
- Angiography was used to confirm embolus location and size.
- Transverse axial spin echo MR images were acquired using a 0.3 T permanent magnet scanner.
- MR imaging sensitivity for clot detection was compared with angiographic findings.
Main Results:
- MR imaging identified 14 out of 19 emboli as areas of increased signal, with a minimum diameter of 2.7 mm.
- Three false positive findings were attributed to slow blood flow in the inferior vena cava.
- Nine emboli were false negatives, suggesting limitations in detection.
- Increased MR signal was linked to the embolus itself and slow distal blood flow.
Conclusions:
- MR imaging demonstrates potential for detecting pulmonary emboli in dogs.
- The technique showed moderate sensitivity and specificity, with limitations due to false positives and negatives.
- Findings suggest that increased MR signal in pulmonary arteries can be caused by emboli and altered blood flow patterns.
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