Tailored and universal parallel transmit broadband pulses for homogeneous 3D excitation of the human heart at 7T.
Magn Reson Med
; 92(2): 730-740, 2024 Aug.
Article
in En
| MEDLINE
| ID: mdl-38440957
ABSTRACT
PURPOSE:
To research and evaluate the performance of broadband tailored kT-point pulses (TP) and universal pulses (UP) for homogeneous excitation of the human heart at 7T.METHODS:
Relative 3D B 1 + $$ {\mathrm{B}}_1^{+} $$ -maps of the thorax were acquired from 29 healthy volunteers. TP and UP were designed using the small-tip-angle approximation for a different composition of up to seven resonance frequencies. TP were computed for each of the 29 B 1 + $$ {\mathrm{B}}_1^{+} $$ -maps, and UPs were calculated using 22 B 1 + $$ {\mathrm{B}}_1^{+} $$ -maps and tested in seven testcases. The performance of the pulses was analyzed using the coefficient of variation (CV) in the 3D heart volumes. The 3D gradient-echo (GRE) scans were acquired for the seven testcases to qualitatively validate the B 1 + $$ {\mathrm{B}}_1^{+} $$ -predictions.RESULTS:
Single- and double-frequency optimized pulses achieved homogeneity in flip angle (FA) for the frequencies they were optimized for, while the broadband pulses achieved uniformity in FA across a 1300 Hz frequency range.CONCLUSION:
Broadband TP and UP can be used for homogeneous excitation of the heart volume across a 1300 Hz frequency range, including the water and the main six fat peaks, or with longer pulse durations and higher FAs for a smaller transmit bandwidth. Moreover, despite large inter-volunteer variations, broadband UP can be used for calibration-free 3D heart FA homogenization in time-critical situations.Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Imaging, Three-Dimensional
/
Heart
Limits:
Adult
/
Female
/
Humans
/
Male
Language:
En
Journal:
Magn Reson Med
Journal subject:
DIAGNOSTICO POR IMAGEM
Year:
2024
Document type:
Article
Affiliation country:
Germany
Country of publication:
United States