Rapid 3D radiofrequency field mapping using catalyzed double‐angle method
19
Citation
23
Reference
10
Related Paper
Citation Trend
Abstract:
Abstract A new method is presented for rapid and accurate large volumetric radiofrequency (RF) field (B ) mapping. This method is a modification of the double‐angle method (DAM), which accelerates imaging speed and applies 3D acquisition to improve B measurement accuracy. It reduces repetition time and scan time by introducing a catalyzation RF pulse chain at the end of each DAM repetition cycle. The catalyzation pulse chain ensures that, after each TR period, the longitudinal magnetizations reach the same state for both measurements at two flip angles for the DAM so that the long TR requirement (TR ≥ 5 T 1 ) for complete relaxation of longitudinal magnetization of DAM becomes unnecessary. A multi‐echo imaging sequence is additionally incorporated to further improve the efficiency of data acquisition. Simulations demonstrate an excellent flip angle measurement accuracy for catalyzed DAM even with TR << T 1 . Phantom and in vivo volunteer studies are presented to demonstrate the catalyzation effect upon B mapping and the application of 3D catalyzed DAM for rapid and accurate large volume RF field mapping. Copyright © 2009 John Wiley & Sons, Ltd.Keywords:
Flip angle
Pulse sequence
Pulse sequence
Flip angle
SIGNAL (programming language)
Nuclear Overhauser effect
Cite
Citations (49)
A new pulse sequence for the measurement of NMR logging is proposed in this article, based on the improvement of original CPMG pulse sequence. In the orig inal pulse sequence, after a CPMG pulse sequence, wait time (or T\-1 relay) is needed to allow the magnetization vector return to equilibrium, then the ne xt me asuring CPMG pulse sequence can be applied. The wait time is kept long and the l ogging speed is low in formations that contain long T\-1 components, since t he log ging apparatus is moving continuously along the bore hole. This is unfavorable b ecause the spin-latti ce relaxation time (T\-1) of oil and gas is always long . However, it's noti ced th at if a 90° pulse from the -x direction (or a 270° pulse from the x direction ) i s applied after the former CMPG pulse sequence, the long T\-1 components can be po larized more completely, then the wait time can be shortened and logging speed c an be improved. The advantage of the improved pulse sequence is proved by calcul ations and analyses.
Pulse sequence
Sequence (biology)
T2 relaxation
Cite
Citations (0)
Flip angle
Pulse sequence
Fast spin echo
SIGNAL (programming language)
Echo (communications protocol)
Sequence (biology)
Echo time
Gradient echo
Cite
Citations (30)
Hyperpolarization
Cite
Citations (23)
Flip angle
Pulse sequence
Gradient echo
Echo (communications protocol)
Cite
Citations (0)
Flip angle
Pulse sequence
Fast spin echo
Echo (communications protocol)
Sequence (biology)
Cite
Citations (0)
Pulse sequence
Sequence (biology)
Derivative (finance)
Cite
Citations (1)
Pulse sequence
Sequence (biology)
Cite
Citations (0)
Pulse sequence
Sequence (biology)
Cite
Citations (1)
Flip angle
Dephasing
Pulse sequence
Bloch equations
SIGNAL (programming language)
Cite
Citations (686)