(VSOP = very small superparamagnetic iron oxide particles) This new class of contrast agents with smaller particle size than SPIO offers advantages for MR angiography. SPIO particles are usually coated with an organic polymer such as dextran, carboxydextran or polyethylene glycol, which limits the minimal overall particle size that can be obtained. VSOP-C184 consists of an aqueous solution of superparamagnetic iron oxide particles with a citrate coating and the overall particle size of 4-8 nm.
Short name: VSOP-C184, central moiety: Fe, concentration: 29 g Fe/l, relaxivity: R1=20.1, R2=37.1, B0=0.94 T.

(VSOP) A new class of contrast agents with smaller particle size than SPIO or USPIO with advantages for MR angiography, caused through a longer plasma half-life.

See also Ultrasmall Superparamagnetic Iron Oxide and Superparamagnetic Iron Oxide.

Postprocessing techniques for artery vein separation by segmentation of the entire vessel structures from the background with different approaches.
Phase contrast imaging can also be used to differentiate arteries and veins based on flow-velocity or flow direction. The fact that arterial and venous flows are in opposite directions also has the advantage to separate the vessels in time of flight angiography.

Volumetric imaging is a 3D technique where all the MRI signals are collected from the entire tissue sample and imaged as a whole entity, therefore providing a high signal to noise ratio. The acquisition of isotropic voxels or thin slices with high spatial resolution allows to create multiplanar reconstructions in all planes; a compensation for the usually longer scan time. The acquisition time can be reduced by parallel imaging technique.
New T2 weighted variants of 3D sequences (FSE-XETA, T2-SPACE, VISTA) have been introduced that differ from conventional FSE sequences. An echo train containing up to 200 echoes obtained at a minimum echo spacing allows very fast acquisition. A flip angle modulation (flip angle sweep - FAS) during the FSE readout carries magnetization as long as possible to avoid blurring and provide optimal signal at the effective echo time. This type of imaging is well suited for brain and spine MRI procedures.
Newer T1 weighted variants include Liver Acquisition with Volume Acquisition (LAVA) and T1W High Resolution Isotropic Volume Examination (THRIVE), which have advantages for dynamic breath hold imaging in liver and abdominal examinations.

See also Volume Imaging, 3 Dimensional Imaging.