For accurate volume-targeting, it is important that the 3D scout scan (Scout 3) and 3D high-resolution coronary MRA are acquired at the same timepoint in the cardiac cycle (identified from the images of Scout 2) and using the same suppression of respiratory motion. For high resolution imaging, the gating window should be reduced to ~5 mm and the localization of the navigator should remain unchanged when compared to Scout 3.Typi-cally, the duration of the acquisition window is also reduced for high resolution coronary MRA (50 - 100 ms).Volume targeting for the right coronary system can be performed using a 3-point planscan tool. Three user-specified points (as viewed on Scout 3) on the proximal RCA, the mid-RCA and the distal RCA define the orientation and location of the center plane of the imaged volume. For the left coronary system, one point on the LM, and one point on the mid-LAD and mid-LCX prescribe a near-transverse view that includes the proximal segments of the left coronary arterial system. The highest (most cranial) point of the left coronary system is not always on the left main. Therefore, it is important to ensure that the prescribed volume encompasses the major proximal segments of the left coronary system. Alternative plane orientations parallel to the LCX and/or the LAD have also been used and long segments of the LCX are often visualized on scans of the RCA. These high resolution volume targeted MRAs provide ideal localizer scans for dual-inversion black-blood coronary vessel wall imaging. In whole-heart coronary MRA as described by Weber and co-workers , a transverse volume that encompasses the apex and the pulmonary artery as viewed on Scout 1 is planned. Although the whole-heart scan lasts 10-15 min, near-isotropic resolution is obtained (Tables 3,4).
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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.