A typical CE MRA examination includes several traditional pulse sequences (e.g. T1-weighted and T2-weighted fast spin echo pulse sequences). These images are particularly important for imaging not only concomitant visceral pathology, but also vessel wall abnormalities such as wall thickening (e.g. aortitis) or intramural hematoma . These preliminary non-contrast pulse sequences are then usually followed by a localization scan for the CE MRA examination. These are typically performed using a bright blood pulse sequence such as TOF MRA or, more recently, steady state free precession (SSFP) pulse sequences (true FISP, Siemens Medical Solutions; Balanced FFE, Philips; FIESTA, GE Medical Systems).
For the CE MRA examination itself, the 3D MRA acquisition is usually performed three times. A pre-contrast 3D MRA acquisition is recommended to ensure proper anatomic coverage and precise positioning of the 3D volume. Unwanted aliasing artifacts, for example, can easily be identified on the pre-contrast scan. It is also recommended that the pre-contrast 3D MRA acquisition be performed in an identical fashion to the actual CE MRA acquisition as this will familiarize the patient to both the breath holding procedure and the expected length for the breath hold. In addition, the pre-contrast acquisition can serve as a mask for subsequent image subtraction, if desired. For the CE MRA, acquisitions are typically performed in both the arterial and delayed phases. The addition of the second delayed phase acquisition will ensure proper visualization of vessels with slow flow or depiction of a late filling false channel in the case of an aortic dissection. Additionally, the second acquisition can often distinguish artifacts from true vascular findings (Fig. 4). Finally, the inclusion of the second post-contrast 3D MRA acquisition may provide additional venous depiction which may be of clinical importance in certain specific clinical situations.
Within this chapter, it is hoped that the reader has established a baseline understanding of the basic theory for CE MRA and improved his or her familiarity with the various terms and options available. In the chapters that follow, the different clinical indications for CE MRA will be discussed with specific technical suggestions for CE MRA.
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