Comparison of Amplitude- and Amplitude-Frequency-Modulated Pulses for Outer Volume Suppression in Cardiac MRI
Application to Myocardial T 2 Mapping
A. Arami (TU Delft - Applied Sciences, Leiden University Medical Center)
M. Bozic (TU Delft - Applied Sciences)
Christal van de Steeg-Henzen (HollandPTC)
Y. Zhao (TU Delft - Applied Sciences)
Y. Zhang (TU Delft - Applied Sciences)
Q. Tao (TU Delft - Applied Sciences)
Alexandru Cernicanu (Philips Benelux)
Hildebrandus Johannes Lamb (Leiden University Medical Center)
S.D. Weingärtner (TU Delft - ImPhys/Computational Imaging, HollandPTC, TU Delft - Applied Sciences)
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Abstract
Purpose
To evaluate single- and dual-band pulse modules for suppressing extra-cardiac signal in cardiac MRI, and test their applicability for time-efficient imaging with reduced FOV in myocardial 𝑇2 mapping at 3 T.
Methods
Outer Volume Suppression (OVS) was implemented using two regional saturation slabs, along the phase-encoding direction. Different Amplitude-Modulated (AM) and Amplitude-Frequency-Modulated (AM-FM) pulses were explored. AM sinc and AM-FM Hyperbolic Secant (HS) pulses, as single- (S:1b and HS:1b) and dual-band (S:2b and HS:2b) versions, were chosen for full evaluation. Pulses were individually optimized for minimal residual signal and optimal suppression-band profiles. Pulse performance was assessed through simulations and phantom experiments, and evaluated in seven healthy subjects using residual signal and quantitative myocardial 𝑇2 mapping with rFOV.
Results
In simulations, optimized HS pulses demonstrated superior suppression-band profile homogeneity and 𝐵0 robustness, while both pulse classes showed comparable 𝐵+1 sensitivity. Phantom data revealed better signal suppression with HS pulses (S:1b: 19.22% ± 3.23%, S:2b: 16.85% ± 6.80%, HS:1b: 4.66% ± 1.04%, HS:2b: 2.85% ± 1.01%). The residual difference across slabs was slightly reduced using simultaneous dual-band compared with sequential single-band approaches (S:1b: 3.81% vs. S:2b: 0.92%; HS:1b: 4.56% vs. HS:2b: 0.66%). In vivo, despite significantly lower residual with HS pulses (p = 0.0015) and visually observed artifacts with sinc pulses, no significant difference in 𝑇2 was observed across all configurations (p = 0.087) in myocardial 𝑇2 mapping.
Conclusion
AM-FM pulses achieved robust suppression of extra-cardiac signals, with dual-band implementations minimizing suppression-band differences. This can enable artifact-free rFOV imaging, for improved image quality in myocardial 𝑇2
mapping.
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