The sequences used for 3D CE MRA are spoiled gradient-recalled-echo (SGE) sequences with zero interpolation in the partition or the slice-selected direction. The abdominal aorta is generally well displayed with a contrast dose of 0.1 mmol/kg of gadobenate dimeglumine (Gd-BOPTA) or 0.2 mmol/kg of a non-protein interacting gadolinium
contrast agent [3,4]. One of the goals in optimizing the sequence parameters is to keep the overall image acquisition time to a minimum, so that acquisition can be achieved in a single breath-hold. This goal is further aided by short TR and TE values. The short TR permits an overall reduction of the imaging time while a short TE helps in minimizing T2* effects. Whenever feasible, the highest possible spatial resolution should be utilized. The speed of acquisition and the spatial resolution of 3D CE MRA are determined and ultimately limited by the performance characteristics of the gradient and other hardware of the scanner. Until comparatively recently, most improvements in performance were achieved by increasing the gradient strength of the scanner. However, the need to avoid neuro-muscular stimulation from rapid gradient switching limits this approach. This limitation has inspired the development of techniques that acquire data much differently and/or more rapidly. These techniques improve the temporal resolution without compromising the spatial resolution and with out requiring high gradient strengths. Among these newer approaches are time-resolved techniques which allow repeated acquisition of a volume of interest during the passage of the contrast agent bolus.
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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.