X-ray angiography and more recently CT angiog-raphy have been considered the gold standard examinations for assessment of the abdominal aorta. However, the invasive nature of the investigation, the large amount of potentially nephrotoxic contrast media involved and the use for ionizing radiation have always been negative factors strengthening the call for a full non-invasive method for demonstration of the abdominal aorta and iliac arteries. Rapid advances in medical technology have made this possible in current clinical practice through magnetic resonance angiography (MRA). Major improvements in image acquisition times and reductions in the volumes of contrast agent utilized have made 3D CE MRA a fast, reproducible, and patient-friendly examination [1,2]. A full MRA study of the abdominal aorta can require as few as 10 minutes of scanner time. The lack of ionizing radiation and use of non-nephrotoxic gadolinium-based contrast agents makes this exam considerably safer for patients.
A major factor that has driven the development and clinical use of CE MRA is the need to overcome the limitations of noncontrast gradient-echo time-of-flight (TOF) techniques. The drawbacks of TOF imaging include long imaging times, an inability to see in-plane and small vessels, and the loss of signal in aneurysmal vascular structures secondary to turbulent flow. The use of paramagnetic contrast agents and faster 3D gradient recalled echo techniques have provided a strong competitor to x-ray angiography and CT angiogra-phy as the first line of study for precise evaluation of the abdominal aorta. The aims of this chapter are to describe the technical approaches to CE MRA of the abdominal aorta and to provide an overview of the pertinent clinical applications in this vascular territory.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.