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Radiofrequency phase encoded half‐pulses in simultaneous multislice ultrashort echo time imaging
Author(s) -
Rettenmeier Christoph,
Stenger V. Andrew
Publication year - 2019
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.27693
Subject(s) - undersampling , image quality , sinc function , pulse sequence , multislice , optics , phase (matter) , sensitivity (control systems) , physics , nuclear magnetic resonance , aliasing , materials science , computer science , artificial intelligence , computer vision , image (mathematics) , electronic engineering , quantum mechanics , engineering
Purpose To describe a simultaneous multislice (SMS) ultrashort echo time (UTE) imaging method using radiofrequency phase encoded half‐pulses in combination with power independent of number of slices (PINS) inversion recovery (IR) pulses to generate multiple‐slice images with short T 2 * contrasts in less than 3 min with close to an eightfold acceleration compared with a standard 2D approach. Theory and Methods Radiofrequency phase encoding is applied in an SMS (N SMS = 4) excitation scheme using “sinc” half‐pulses. With the use of coil sensitivity encoding (SENSE) and controlled aliasing in parallel imaging (CAIPI) in combination with a gradient echo 2D spiral readout trajectory and IR PINS pulses for contrast enhancement a fast UTE sequence is developed. Images are obtained using a model‐based reconstruction method. Sequence details and performance tests on phantoms as well as the heads of healthy volunteers at 3T are presented. Results An SMS UTE sequence with an undersampling factor of 4 is developed using radiofrequency phase encoded half‐pulses and PINS IR pulses which enables the acquisition of 8 slices at 0.86 2 mm 2 resolution in less than 3‐min scan time. UTE images of the head are obtained showing highlighted signal of cortical bone. Image quality and T 2 contrast are comparable to the one obtained by corresponding single slice acquisitions with only minor deviations. Conclusions The method combining radiofrequency phase encoded SMS half‐pulses and PINS IR pulses presents a suitable approach to SMS UTE imaging. The usage of coil sensitivity information and increased sampling density by means of interleaved slice group acquisitions allows to reduce the total scan time by a factor close to 8.