flip angle

flip an·gle

in a magnetic resonance imaging pulse sequence, the deviation toward transverse plane of the average axis of the protons induced by radiofrequency signals; low angles are used in rapid or bright blood imaging sequences.

flip angle

in magnetic resonance imaging, the degree of rotation of the macroscopic magnetization vector produced by a radiofrequency pulse with respect to the direction of the static magnetic field.

flip angle

An MRI term for the angle to which the net magnetisation is rotated or tipped relative to the main magnetic field direction by applying a radiofrequency excitation pulse at the Larmor frequency. The flip angle is used to define the angle of excitation for a field echo pulse sequence.

flip an·gle

(flip ang'gĕl)
In a magnetic resonance imaging sequence, the rotation of the average axis of the protons induced by radiofrequency signals; low angles are used in rapid-imaging sequences and to show a signal from flowing blood.
References in periodicals archive ?
The protocol included an axial T1-weighted turbo spin echo (TSE) sequence with fat suppression in the transverse plane with the following parameters: repetition time, TR = 625 ms, echo time, TE = 12 ms, flip angle, [alpha] = 150[degrees], and voxel size, 0.
These maps were used to calculate the dynamic change in relaxation rate from the dynamic scan using a flip angle method proposed by Li et al.
The Ernest angle (5) is the flip angle in spoiled gradient-echo imaging where signal intensity is maximized:
As the T1-relaxation time of intravascular contrast is shorter than that of a parenchymal organ, the 3-dimensional spoiled gradient-echo sequence would use a larger flip angle for MR angiography and a smaller flip angle for parenchymal organ imaging.
It is apparent that the flip angle, important as it is, it does not directly show deviation from uniformity.
Increasing the flip angle also results in better suppression of stationary tissue.
0]) and the square of the flip angle ([alpha]) and is directly proportional to the duty cycle (D) and the volume of the patient imaged (V).
The nonselective RF pulse permits ultra-short echo spacing and the variable flip angle results in a pseudo steady-state with maintained relative tissue contrast (Figure 5) as well as a reduction of blurring associated with high ETL.
7) This effect, known as the dielectric effect, causes the flip angle and signal measured in the breast to be nonuniform (Figure 2).
The reduction from a flip angle of 180[degrees] (to typically approximately 120[degrees]) has been well tolerated thus far without any noticeable deleterious effect on image contrast.
Manipulations traditionally used to limit SAR include reducing acquisition flip angle (eg, from 180[degrees] on fast spin-echo [FSE] and ~40[degrees] on gradient-recalled echo [GRE]), which could potentially affect image contrast.