With this magnetic resonance angiography technique flowing blood appears dark.
MR black blood techniques have been developed for cardiovascular imaging to improve segmentation of myocardium from the blood pool. Black blood MRA techniques decrease the signal from blood with reference to the myocardium and make it easier to perform cardiac chamber segmentation.
ECG gated spin echo sequences with presaturation pulses for magnetization preparation will show strong intravascular signal loss due to flow effects when appropriate imaging conditions including spatial presaturation are used. The sequence use the flow void effect as blood passes rapidly through the selected slice.
For dark blood preparation, a pair of nonselective and selective 180° inversion pulses are used, followed by a long inversion time to null signal from inflowing blood. A second selective inversion pulse can also be applied with short inversion time to null the fat signal. These in cardiac imaging used black blood techniques are referred to as double inversion recovery T1 measurement turbo spin echo or fast spin echo, and double-inversion recovery STIR.

Phenomenological (classical) equations of motion for the macroscopic magnetization vector. They include the effects of precession about the magnetic field (static and RF) and the T1 and T2 relaxation times.

When a group of spins is placed in a magnetic field, each spin aligns in one of the two possible orientations. The relative numbers of spins with different alignments will be given by the Boltzmann distribution.
Definition: if a system of particles, which are able to exchange energy in collisions is in thermal equilibrium, then the relative number (population) of particles, N1 and N2, in two particular energy levels with corresponding energies, E1 and E2, is given by N1/N2 = exp [-(E1 - E2)/kT] where k is the Boltzmann constant and T is the absolute temperature.
For example, in NMR of protons at room temperature in a magnetic field of 0.25 tesla, the difference in relative numbers of spins aligned with the magnetic field and against the field is about one part in a million; the small excess of nuclei in the lower energy state is the basis of the net magnetization and the resonance phenomenon.

A method of tracking moving spins after tagging them (locally altering their magnetization). The moving spins are then imaged at some time after tagging to show where the bolus (the small tagged volume of spins) has moved in the imaging plane.

The coordinate system most frequently used to quantitatively describe a n-dimensional space.
In 2 dimensions, i.e. a plane, it describes any point as a function of 2 perpendicular unit vectors (1,0) and (0,1) and in 3 dimensions as a function of 3 perpendicular unit vectors (1,0,0), (0,1,0) and (0,0,1). Functions in 2 dimensions are often conveniently described using the so-called theory of functions. When using this type of mathematical description, the imaginary number
i = √(-1) is introduced to label the y-axis.
a + ib is then actually a 2 dimensional vector with a x-axis component of 'a' and a y-axis component of 'b'.
The 'a' is called the real part and the 'b' the imaginary part of the function, an expression that is frequently encountered in MRI, where the real image is a pixel-wise representation of 'a' and the imaginary image a pixel-wise representation of 'b', with 'a' and 'b' the components of the xy-magnetization along the x- and y-axis, respectively.
(Renatus Cartesius/Rene Descartes, 1596-1650, French philosopher and mathematician)