Table 1.
Definition of direct and indirect findings of pulmonary embolism on MRA.
| Direct findings of PE on MRA | Definition |
|---|---|
| Filling defect in the pulmonary arteries | Low signal intensity clot in the pulmonary arteries after contrast enhancement |
| Vessel cutoff sign | Vessel completely obstructed and amputated on Maximum Intensity Projection images |
| Double bronchus signa | Two low signal intensity structures in cross-section- one representing a bronchus and the other representing the occlusive thrombus |
| Central dot signa | Central high intensity in the clot |
| Ghost vessel signa | Enhancement of a vessel wall surrounding an obstructing embolus on delayed contrast enhances MRA images |
| Bright clot signa | High T1 signal intensity from intraluminal methemoglobin on a pre-contrast image |
| Indirect findings of PE on MRA | |
| Pulmonary venous stasis | Higher signal intensity vein related to slow flow and delayed timing of the peak enhancement time course of contrast through this vein |
| Atelectasis | Strong enhanced lung reflects collapsed lung |
| Perfusion defects | Wedge shaped areas of low signal intensity due to loss of lung parenchymal enhancement |
| Visceral pleural enhancementa | liner enhancement along lung surface |
| White-black-white signa | A perfusion defect surrounded by enhancing lung |
| Pulmonary infarction | High T2 weighted wedge shaped area of lung parenchyma without enhancement |
| Blank slate signa | A large area of completely black lung that has no signal intensity with in it |
Abbreviations: PE-pulmonary embolism, MRA- magnetic resonance angiography.
a
Findings unique for contrast enhanced MRA.