Abstract
Purpose: To design multidimensional spatially selective radiofrequency
(RF) pulses for inner volume imaging (IVI) with threedimensional
(3D) fast spin echo (FSE) sequences. Enhanced
background suppression is achieved by exploiting particular
signal properties of FSE sequences.
Theory and Methods: The CPMG condition dictates that echo
amplitudes will rapidly decrease if a 90 phase difference between
excitation and refocusing pulses is not present, and refocusing flip
angles are not precisely 180. This mechanism is proposed as a
means for generating additional background suppression for spatially
selective excitation, by biasing residual excitation errors
toward violating the CPMG condition. 3D RF pulses were designed
using this method with a 3D spherical spiral trajectory, undersampled
by factor 5.6 for an eight-channel PTx system, at 3 Tesla.
Results: 3D-FSE IVI with pulse durations of approximately 12
ms was demonstrated in phantoms and for T2-weighted brain
imaging in vivo. Good image quality was obtained, with mean
background suppression factors of 103 and 82 6 6 in phantoms
and in vivo, respectively.
Conclusion: Inner Volume Imaging with 3D-FSE has been demonstrated
in vivo with tailored 3D-RF pulses. The proposed
design methods are also applicable to 2D pulses. M
(RF) pulses for inner volume imaging (IVI) with threedimensional
(3D) fast spin echo (FSE) sequences. Enhanced
background suppression is achieved by exploiting particular
signal properties of FSE sequences.
Theory and Methods: The CPMG condition dictates that echo
amplitudes will rapidly decrease if a 90 phase difference between
excitation and refocusing pulses is not present, and refocusing flip
angles are not precisely 180. This mechanism is proposed as a
means for generating additional background suppression for spatially
selective excitation, by biasing residual excitation errors
toward violating the CPMG condition. 3D RF pulses were designed
using this method with a 3D spherical spiral trajectory, undersampled
by factor 5.6 for an eight-channel PTx system, at 3 Tesla.
Results: 3D-FSE IVI with pulse durations of approximately 12
ms was demonstrated in phantoms and for T2-weighted brain
imaging in vivo. Good image quality was obtained, with mean
background suppression factors of 103 and 82 6 6 in phantoms
and in vivo, respectively.
Conclusion: Inner Volume Imaging with 3D-FSE has been demonstrated
in vivo with tailored 3D-RF pulses. The proposed
design methods are also applicable to 2D pulses. M
| Original language | English |
|---|---|
| Journal | Magnetic Resonance in Medicine |
| DOIs | |
| Publication status | E-pub ahead of print - 2015 |