MR angiography of carotid arteries

Before covering the basics a question is to be answered as to why one should use contrast-enhanced MR angiography as compared to other imaging modalities or even other MR angiographic techniques. As compared to other imaging modalities the answer is easy. Contrast-enhanced MR angiography is fast, (relatively) operator independent, patient friendly, without the use of nephrotoxic contrast agents or even ionizing radiation. Although ultrasound is a fierce competitor for imaging the carotid arteries, its limited field-of-view and the inability to postprocess the data (reconstruct it in any desired direction) are not in favour of this modality. Furthermore, as can ultrasound, MRI can also visualize the vascular wall, allowing for better assessment of the risk of plaque burden. Major drawbacks can be the availability of suitable MR systems and the costs of an MR examination. As compared to the more conventional MR angiographic techniques the answer is also easy. Contrast-enhanced MR angiography is not flow-dependent, which makes the overall quality of the acquired data much better. Furthermore, contrast-enhanced MR angiography has a much higher signal-to-noise ratio and often a better contrast-to-noise ratio due to the fact that three-dimensional volumes with ultrashort TR values are used. Finally, contrast-enhanced MR angiography is much faster than conventional MR angiographic techniques like time-of-flight (also known as inflow) or phase-contrast MR angiography.