Pulmonary angiography

Pulmonary Vascular Imaging: PE Diagnostics

Computed tomographic angiography (CTA) and magnetic resonance angiography (MRA) play a decisive role in identifying acute life-threatening conditions.

A classic clinical example of the use of imaging methods is the diagnosis of massive pulmonary embolism (PE). In this condition, vascular occlusion by a large embolus leads to pulmonary infarction.

During the examination (both on radiography and CTA), the radiologist can visualize the following signs:

• Presence of the embolus itself, obstructing the vessel lumen (e.g., occlusion of the lower lobe pulmonary artery).
• Extensive consolidation of the lung tissue in the affected area, corresponding to the infarction zone (e.g., in the lower lobe of the right lung).
• Signs of cavitation (cavity formation) within the pulmonary infarction zone.

Method Comparison: CTA vs. Lung MRA

Both CTA and MRA have specific indications and features for evaluating the pulmonary vasculature. In general, both methods demonstrate comparable and similar results when addressing the following tasks:

• Detection and treatment planning for pulmonary arteriovenous malformations (AVMs).
• Diagnosis of pulmonary sequestration.
• Visualization of bronchial arteries (both methods handle this task equally well).

Advantages of CT angiography: CTA is considered the preferred method due to superior visualization of the lung parenchyma itself. This allows for the simultaneous evaluation of lung tissue status during a single scan (e.g., detecting concomitant bronchiectasis), making the method more versatile in emergency practice.

Application of CTA and MRA in Emergency Angioneurology

CT and MR angiography techniques are also widely used to assess other vascular beds, particularly in the diagnosis of acute stroke, where the evolution of algorithms has shifted from simple non-contrast CT to contrast-enhanced techniques (dynamic perfusion and CTA).

Features of CT methods in stroke:

• CTA has high sensitivity for intravascular emboli.
• Multiphasic CTA allows for the evaluation of collateral circulation.
• A normal CTA indicates a low likelihood of benefit from intervention.
• CT perfusion shows decreased perfusion in the infarction zone.
• The complex (CT + CTA + CT perfusion) helps rule out hemorrhage, confirm occlusion, and assess the at-risk zone (the ischemic penumbra — penumbra).
• Limitations: CT methods are unreliable for infarctions of the posterior cranial fossa (PCF) or deep brain nuclei and are informative mainly for the supratentorial circulation.

Features of MRI and MRA:

• MRI has a clear superiority in diagnosing cerebral infarction, regardless of the lesion's location (including small infarcts and PCF lesions).
• The DWI sequence is exceptionally sensitive to acute infarction, while the combination of T2, DWI, and FLAIR detects minute hemorrhages.
• MRI allows for the selection of patients with an unknown time of symptom onset (e.g., "wake-up stroke") by evaluating the mismatch between DWI and FLAIR sequences. This can extend the therapeutic window for thrombectomy up to 24 hours.
• MRA is better at detecting acute dissection of the carotid and vertebral arteries and, unlike CTA, is not subject to the negative impact of plaque calcification.
• Limitations of MRI as a first-line method: Limited availability, long scan times, complex preparation (presence of implanted devices), and patient monitoring difficulties.

Class and exam questions

What else to study on this topic

• Evaluation of collateral circulation on multiphasic CT angiography
• Diffusion-weighted imaging (DWI) and detection of acute ischemia
• Ischemic penumbra and methods for its evaluation using CT perfusion
• The concept of mismatch between DWI and FLAIR sequences
• Predictors of probable recanalization on CT (multisegment thrombus sign)

Other topics in the "Interventional radiology" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.