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With further refinements, namely a good mask subtraction, fast 2D pulse sequences can also be used to provide 2D projectional angiograms similar to those of conventional x-ray digital subtraction angiography (DSA). Wang et al [5,6] have successfully implemented 2D MR DSA using a specialized off-line complex subtraction algorithm. This technique is particularly helpful for illustration of distal run-off vessels [6,7].A series of relatively thick (8-10 cm) 2D projectional images are acquired during the intravenous injection of 6-10 mL of Gd-chelate contrast agent. During each injection, a series of 2D MR DSA is performed with

Fig. 1. 2D MR DSA of the ankle using complex subtraction. Projectional 2D subtraction images were obtained as a single slab, typically 80100 mm thick, with spoiled gradient echo imaging using the standard head coil. 2D images were acquired repeatedly at 2-second intervals beginning simultaneously with the hand injection of a 7 mL bolus of Gd-chelate contrast media via a peripheral intravenous catheter at approximately 3 mL/sec. The contrast injection is followed by 20 ml of saline flush at the same rate. From these images the bolus timing for the thigh and knee stations can be determined and the timing for the abdomen-pelvis can be estimated. Typically the time to fill the abdomen pelvis is 2/3 the time required to reach the ankles. It is also possible to identify when veins begin to enhance so that the window of arterial enhancement without venous enhancement can be identified (Reprinted and modified with permission from [17])

Fig. 1. 2D MR DSA of the ankle using complex subtraction. Projectional 2D subtraction images were obtained as a single slab, typically 80100 mm thick, with spoiled gradient echo imaging using the standard head coil. 2D images were acquired repeatedly at 2-second intervals beginning simultaneously with the hand injection of a 7 mL bolus of Gd-chelate contrast media via a peripheral intravenous catheter at approximately 3 mL/sec. The contrast injection is followed by 20 ml of saline flush at the same rate. From these images the bolus timing for the thigh and knee stations can be determined and the timing for the abdomen-pelvis can be estimated. Typically the time to fill the abdomen pelvis is 2/3 the time required to reach the ankles. It is also possible to identify when veins begin to enhance so that the window of arterial enhancement without venous enhancement can be identified (Reprinted and modified with permission from [17])

Fig. 2a-c. 2D MR DSA of the cerebral vasculature in a patient with a frontal AVM. An axial T2w image (a) shows areas of flow void (arrow) indicating an AVM. For MRA DSA 2D images were acquired repeatedly at 0.5 second intervals with alternate acquisition of sagittal (b) and axial (c) projections. Imaging was started simultaneously with the injection of a 7 mL bolus of Gd-BOPTA via a peripheral intravenous catheter at 3.5 mL/sec. The contrast injection was followed by a 20 ml saline flush at the same injection rate. Both the sagittal and axial projections nicely display the AVM (arrows) and the early venous drainage can be followed due to the high temporal resolution [Image courtesy of Prof. Danielle Balériaux, Clinique de Neuroradiologie, Hôpital Erasmus, Brussels, Belgium]

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c frame rates of every 2-3 seconds (Fig. 1). The technique, however, continues to be investigational with limited availability, nevertheless in imaging of cerebral AV-malformation it can already compete with catheter angiography (Fig. 2).

Baby Sleeping

Baby Sleeping

Everything You Need To Know About Baby Sleeping. Your baby is going to be sleeping a lot. During the first few months, your baby will sleep for most of theday. You may not get any real interaction, or reactions other than sleep and crying.

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