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.
Farlex Partner Medical Dictionary © Farlex 2012

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.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

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.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012
References in periodicals archive ?
The protocol included: T2-weighted HASTE (Half-Fourier acquisition single-shot turbo spin-echo) (TR/TE, 1200/94; flip angle, 150[degrees]), T1-weighted FLASH (fast low angle shot magnetic resonance imaging) (TR/TE, 169/4.76; flip angle, 70[degrees]) and T2-weighted TruFISP (true fast imaging with steady-state precession) (TR/TE, 3.75/1.8; flip angle, 50[degrees]) with slice thickness 4 mm, FOV 320-400 mm, and acquisition matrix 256-448 mm in three planes.
The image sequence included the following: (1) a sagittal and axial PD-weighted turbo spin-echo sequence with fat suppression, a flip angle of 90[degrees], a repetition time of 3000 ms, an echo time of 41 ms, a field of view (FOV) of 170 mm, 20 slices, a 480 x 640-pixel matrix, and a slice thickness of 3 mm; (2) a coronal PD-weighted sequence with fat suppression, a flip angle of 150[degrees], a repetition time of 3500 ms, an echo time of 41 ms, a FOV of 170 mm, 20 slices, a 217 x 320-pixel matrix, and a slice thickness of 3 mm; and (3) a sagittal T1-weighted turbo spin-echo with a repetition time of 579 ms, an echo time of 11 ms, a flip angle of 90[degrees], a FOV of 170 mm, 20 slices, a 480 x 640-pixel matrix, and a slice thickness of 3 mm.
Previous studies have used a variable flip angle (VFA) approach [18] to acquire volume T1 maps within a clinically acceptable time.
The parameters used for the patients were as follows: Turbospin echo T2 weighted sequences (T2 w) (TR: 3000, TE:74, flip angle: 150), spin echo T1 w sequence (TR:473, TE:7.7, flip angle: 90) on the axial plane, turbospin echo fat-saturated T2 w sequence (TR: 3300, TE:74, flip angle: 150) on the coronal plane, and turbospin echo T2 w sequence (TR: 6030, TE:103, flip angle: 150) on the sagittal plane.
3D-Proton Density-Non-Fat Suppressed-SPACE (Sampling Perfection with Application optimized Contrasts using different flip angle Evolutions) sequence (flip angle = 120[degrees]; repetition time (TR) = 1,000 msec; echo time (TE) = 46 msec; bandwidth = 460 Hz/pixel; Field of View (FOV) = 160 mm x 160 mm; matrix size = 320 x 300 pixels; voxel size = 0.5 x 0.5 x 0.5 mm (3) ) and
Increased flip angle is recommended in the evaluation of the biliary tree using liver-specific gadolinium-enhanced MRC.
Four acquisitions were obtained in a chronological order with a field of view (FOV) of 22 x 22 x 6 cm (AP x RL x FH): precontrast [T.sub.1]-weighted fast field echo (FFE) acquisition using a flip angle of 5[degrees] ("FA5" acquisition) in 1 minute 22 seconds; [T.sub.2]-weighted imaging ("T2W" acquisition) in 50 seconds; B1 mapping measurement acquisition ("B1MAP" acquisition) in 1 minute 23 seconds; and DCE acquisition using a flip angle of 15[degrees] ("FA15" acquisition) in 6 minutes 47 seconds with 65 dynamic scans.
The T1-weighted images were acquired as a 3D volume (256 x 256 x 174) using a spoiled gradient echo sequence with TR/TI/TE = 10400/4500/300 ms, flip angle = 15[degrees], and voxel size = 0.9375 x 0.9375 x 1 [mm.sup.3].
The imaging parameters for the 3D TOF-MRA scan were as follows: TR/TE = 23/3.5 ms; flip angle = 20.0[degrees]; FOV = 200 x 200 mm; matrix size = 488 x 249; SENSE factor = 2.5; slice thickness = 1.0 mm; and NEX = 1.
The 3D TOF MRA protocol utilizes TONE (tilted optimized nonsaturating excitation) to reduce saturation effects [7]; the mean flip angle was 25[degrees].
BMAT of the L3 and femoral necks on T1-weighted MRI (TR/TE, 150ms/4.4ms, flip angle, 70[degrees]) was segmented at the Image Analysis Laboratory by trained, quality-controlled, and cross-validated technicians using image analysis software (SliceOmatic, Tomovision Inc., Montreal, Canada).
It is apparent that the flip angle, important as it is, it does not directly show deviation from uniformity.