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Pulmonary magnetic resonance angiography
J F Meaney1, L O Johansson, H Ahlstrom
1Department of Radiology, Leeds General Infirmary, Leeds LS1 3EX, United Kingdom.
Abstract:
Early attempts to image the pulmonary vasculature with spin-echo magnetic resonance (MR) imaging were hampered by severe image degradation related to respiratory and cardiac pulsation artifact, susceptibility at interfaces between lung parenchyma and vessel wall, and poor contrast between flowing blood and intravascular filling defects of emboli. With the development of gradient-echo MR angiographic techniques some of these limitations were overcome; however, the need for multiple breath-holds and the frequent occurrence of flow-related artifacts that could simulate pulmonary emboli diminished their clinical utility. With the development of contrast-enhanced MR angiography, many of the limitations of earlier techniques were addressed. Images of both lungs with high signal-to-noise ratios and high contrast between flowing blood and pulmonary emboli could be acquired in a single breath-hold, during "first-pass" imaging with extracellular contrast agents in the coronal plane. However, subsegmental vessels could not be assessed with this approach. The technique has been refined further by imaging each lung separately in the sagittal plane; this offers higher resolution and total lung coverage and requires a shorter breath-hold. Finally, several investigators have reported preliminary data on imaging of the pulmonary vasculature with blood pool agents, exploiting respiratory triggering or navigator echoes to eliminate the need for breath-holding for the detection of pulmonary emboli.
Insights
Magnetic resonance (MR) angiography has evolved to overcome limitations in imaging the pulmonary vasculature. Advanced contrast-enhanced techniques now provide high-resolution, single-breath-hold imaging for detecting pulmonary emboli.
Area of Science:
- Radiology
- Medical Imaging
- Cardiovascular Imaging
Background:
- Early spin-echo MR imaging of pulmonary vasculature suffered from motion artifacts and poor contrast.
- Gradient-echo MR angiography improved imaging but required multiple breath-holds and had flow-related artifacts.
- Pulmonary embolism detection remained challenging with earlier MR techniques.
Purpose of the Study:
- To review the evolution of magnetic resonance (MR) angiography techniques for imaging the pulmonary vasculature.
- To highlight advancements in contrast-enhanced MR angiography for improved pulmonary embolism detection.
- To discuss the clinical utility and limitations of various MR imaging approaches for the pulmonary arteries.
Main Methods:
- Evolution from spin-echo to gradient-echo MR angiography.
- Development and refinement of contrast-enhanced MR angiography (CE-MRA) techniques.
- Application of extracellular and blood pool contrast agents with respiratory triggering/navigator echoes.
Main Results:
- Contrast-enhanced MR angiography enables high signal-to-noise ratio and contrast imaging in a single breath-hold.
- Refined sagittal plane imaging offers higher resolution and total lung coverage.
- Blood pool agents with respiratory triggering show promise for breath-hold-free pulmonary embolism detection.
Conclusions:
- Contrast-enhanced MR angiography represents a significant advancement for pulmonary vasculature imaging.
- Technological refinements have improved resolution, coverage, and breath-hold requirements.
- Emerging techniques show potential for non-breath-hold detection of pulmonary emboli.