Time resolved imaging can be useful for optimization of a pulmonary 3D CE MRA. Pulmonary 3D CE MRA has become particularly popular for pre-procedural pulmonary venous mapping in patients with paroxysmal atrial tachycardias in whom electrophysiological pulmonary venous ablation procedures are contemplated.
In this case, time resolved imaging can be used as a bolus timing scan to ensure proper timing of imaging for peak pulmonary venous imaging. This can be performed using a fast 2D or 3D technique. The 3D technique has the advantage of spatial coverage but for 3-5 sec temporal resolution provides insufficient spatial resolution for definitive pulmonary venous imaging. Time resolved 3D imaging can be performed using a sufficiently large 3D volume to cover the left atrium and proximal pulmonary veins with spatial resolution of the order of 2 x 2 mm in-plane, and 2.5 mm through plane. A contrast bolus of 12-15 mL is infused at 3 mL/sec is typically required. This relatively low spatial resolu tion sequence provides a series of images that can illustrate contrast bolus progression through the superior vena cava, right heart, pulmonary arteries, pulmonary veins, left heart, and aorta. From this preliminary time resolved scan, the optimum time for pulmonary venous imaging can be chosen for acquisition of a high-spatial resolution 3D CE MRA. The high spatial resolution pulmonary venous 3D CE MRA typically is acquired with a 1.21.5 mm through plane spatial resolution and an acquisition time of 10-15 seconds per 3D MRA. This high-resolution 3D CE MRA acquisition is obtained during the administration of approximately 30 mL of Gd-chelate contrast media injected at 3 mL/sec.
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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.