Pulmonary MR angiography (MRA) has faced the challenges of overcoming the problems of respiratory motion, cardiac pulsation, and susceptibility artifact at air-tissue interfaces yet still being able to resolve small sub-segmental pulmonary arteries. Early development of pulmonary MRA techniques focused on black blood and time-of-flight approaches. Neither of these has proven reliable. Three-dimensional (3D) contrast MRA now offers several advantages that make pulmonary MRA possible. The 3D spoiled gradient echo technique has an intrinsically short echo time (TE). With high performance gradients, echo times under 3 and even 1-2 ms are available. These are sufficient to eliminate susceptibility artifact. Due to the enhancement with paramagnetic contrast, 3D contrast MRA is less affected by inflow variations that create pulsation artifact on time-of-flight and phase contrast imaging. Breath-holding eliminates respiratory motion artifact. The net result is that it is now possible to depict smaller, more distal pulmonary arteries, comparable even to spiral CTA (computed tomographic angiography) but without incurring the risks associated with the intravenous administration of a large bolus of iodinated contrast (Figure 2.1).
KeywordsPulmonary Artery Equilibrium Phase Data Respiratory Motion Artifact Distal Pulmonary Artery Pulmonary Arteriography
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