TY  - JOUR
AU  - Völzke, Yannik
AU  - Akbey, Suzan
AU  - Löwen, Daniel
AU  - Pracht, Eberhard Daniel
AU  - Stirnberg, Rüdiger
AU  - Gras, Vincent
AU  - Boulant, Nicolas
AU  - Zaiss, Moritz
AU  - Stöcker, Tony
TI  - Calibration-free whole-brain CEST imaging at 7T with parallel transmit pulse design for saturation homogeneity utilizing universal pulses (PUSHUP).
JO  - Magnetic resonance in medicine
VL  - 93
IS  - 2
SN  - 1522-2594
CY  - New York, NY [u.a.]
PB  - Wiley-Liss
M1  - DZNE-2024-01380
SP  - 630 - 642
PY  - 2025
AB  - Chemical exchange saturation transfer (CEST) measurements at ultra-high field (UHF) suffer from strong saturation inhomogeneity. Retrospective correction of this inhomogeneity is possible to some extent, but requires a time-consuming repetition of the measurement. Here, we propose a calibration-free parallel transmit (pTx)-based saturation scheme that homogenizes the saturation over the imaging volume, which we call PUlse design for Saturation Homogeneity utilizing Universal Pulses (PUSHUP).Magnetization transfer effects depend on the saturation B 1 rms 
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AB  -  B<sub>1</sub><sup>rms</sup> </td></tr></table>
AB  - </td></tr></table>
AB  - 
AB  -  . PUSHUP homogenizes the saturation B 1 rms 
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AB  -  B<sub>1</sub><sup>rms</sup> </td></tr></table>
AB  - </td></tr></table>
AB  - 
AB  -  by using multiple saturation pulses with alternating B 1 
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AB  -  B<sub>1</sub> </td></tr></table>
AB  - </td></tr></table>
AB  - 
AB  -  -shims. Using a database of B 1 
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AB  -  B<sub>1</sub> </td></tr></table>
AB  - </td></tr></table>
AB  - 
AB  -  maps, universal pulses are calculated that remove the necessity of time-consuming, subject-based pulse calculation during the measurement.PUSHUP was combined with a whole-brain three-dimensional-echo planar imaging (3D-EPI) readout. Two PUSHUP saturation modules were calculated by either applying whole-brain or cerebellum masks to the database maps. The saturation homogeneity and the group mean CEST amplitudes were calculated for different B 1 
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AB  -  B<sub>1</sub> </td></tr></table>
AB  - </td></tr></table>
AB  - 
AB  -  -correction methods and were compared to circular polarized (CP) saturation in five healthy volunteers using an eight-channel transmit coil at 7 Tesla.In contrast to CP saturation, where accurate CEST maps were impossible to obtain in the cerebellum, even with extensive B 1 
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AB  - <table align="center" cellspacing="0"  cellpadding="2"><tr><td nowrap="nowrap" align="center">
AB  -  B<sub>1</sub> </td></tr></table>
AB  - </td></tr></table>
AB  - 
AB  -  -correction, PUSHUP CEST maps were artifact-free throughout the whole brain. A 1-point retrospective B 1 
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AB  -  B<sub>1</sub> </td></tr></table>
AB  - </td></tr></table>
AB  - 
AB  -  -correction, that does not need repeated measurements, sufficiently removed the effect of residual saturation inhomogeneity.The presented method allows for homogeneous whole-brain CEST imaging at 7 Tesla without the need of a repetition-based B 1 
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AB  -  B<sub>1</sub> </td></tr></table>
AB  - </td></tr></table>
AB  - 
AB  -  -correction or online pulse calculation. With the fast 3D-EPI readout, whole-brain CEST imaging with 45 saturation offsets is possible at 1.6 mm resolution in under 4 min.
KW  - Humans
KW  - Brain: diagnostic imaging
KW  - Magnetic Resonance Imaging: methods
KW  - Algorithms
KW  - Image Processing, Computer-Assisted: methods
KW  - Phantoms, Imaging
KW  - Calibration
KW  - Adult
KW  - Male
KW  - Female
KW  - CEST (Other)
KW  - magnetization transfer (Other)
KW  - parallel transmit (Other)
KW  - ultra‐high field (Other)
KW  - universal pulses (Other)
LB  - PUB:(DE-HGF)16
C2  - pmc:PMC11604840
C6  - pmid:39301770
DO  - DOI:10.1002/mrm.30305
UR  - https://pub.dzne.de/record/273901
ER  -