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Saturation pulse design for quantitative myocardial T1 mapping.

Chow K, Kellman P, Spottiswoode BS, Nielles-Vallespin S, Arai AE, Salerno M, Thompson RB - J Cardiovasc Magn Reson (2015)

Bottom Line: The optimized BIR4-90 reduced the maximum residual /MZ/M0/ to <1 %, a 5.8× reduction compared to a reference BIR4-90.An optimized 3-pulse train achieved a maximum residual /MZ/M0/ <1 % for the 1.5 T optimization range compared to 11.3 % for a standard 90°-90°-90° pulse train, while a 6-pulse train met this target for the wider 3 T ranges of B0 and [Formula: see text].Adiabatic and pulse train saturation pulses optimized for different constraints found at 1.5 T and 3 T achieved <1 % residual /MZ/M0/ in phantom experiments, enabling greater accuracy in quantitative saturation recovery T1 imaging.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Faculty of Medicine and Dentistry, 1082 Research Transition Facility, University of Alberta, Edmonton, AB, T6G 2V2, Canada. kelvin.chow@ualberta.ca.

ABSTRACT

Background: Quantitative saturation-recovery based T1 mapping sequences are less sensitive to systematic errors than the Modified Look-Locker Inversion recovery (MOLLI) technique but require high performance saturation pulses. We propose to optimize adiabatic and pulse train saturation pulses for quantitative T1 mapping to have <1 % absolute residual longitudinal magnetization (/MZ/M0/) over ranges of B0 and [Formula: see text] (B1 scale factor) inhomogeneity found at 1.5 T and 3 T.

Methods: Design parameters for an adiabatic BIR4-90 pulse were optimized for improved performance within 1.5 T B0 (±120 Hz) and [Formula: see text] (0.7-1.0) ranges. Flip angles in hard pulse trains of 3-6 pulses were optimized for 1.5 T and 3 T, with consideration of T1 values, field inhomogeneities (B0 = ±240 Hz and [Formula: see text]=0.4-1.2 at 3 T), and maximum achievable B1 field strength. Residual MZ/M0 was simulated and measured experimentally for current standard and optimized saturation pulses in phantoms and in-vivo human studies. T1 maps were acquired at 3 T in human subjects and a swine using a SAturation recovery single-SHot Acquisition (SASHA) technique with a standard 90°-90°-90° and an optimized 6-pulse train.

Results: Measured residual MZ/M0 in phantoms had excellent agreement with simulations over a wide range of B0 and [Formula: see text]. The optimized BIR4-90 reduced the maximum residual /MZ/M0/ to <1 %, a 5.8× reduction compared to a reference BIR4-90. An optimized 3-pulse train achieved a maximum residual /MZ/M0/ <1 % for the 1.5 T optimization range compared to 11.3 % for a standard 90°-90°-90° pulse train, while a 6-pulse train met this target for the wider 3 T ranges of B0 and [Formula: see text]. The 6-pulse train demonstrated more uniform saturation across both the myocardium and entire field of view than other saturation pulses in human studies. T1 maps were more spatially homogeneous with 6-pulse train SASHA than the reference 90°-90°-90° SASHA in both human and animal studies.

Conclusions: Adiabatic and pulse train saturation pulses optimized for different constraints found at 1.5 T and 3 T achieved <1 % residual /MZ/M0/ in phantom experiments, enabling greater accuracy in quantitative saturation recovery T1 imaging.

No MeSH data available.


Related in: MedlinePlus

A  map (bottom left) and T1 maps (top row) using SASHA with a reference 90°-90°-90° saturation pulse, SASHA with a proposed 6-pulse train, and MOLLI in a swine. Air regions with low signal intensities are masked for visualization. A profile of T1 values along the left ventricular wall shows decreased T1 values in the lateral wall coinciding with reduced  values
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Fig8: A map (bottom left) and T1 maps (top row) using SASHA with a reference 90°-90°-90° saturation pulse, SASHA with a proposed 6-pulse train, and MOLLI in a swine. Air regions with low signal intensities are masked for visualization. A profile of T1 values along the left ventricular wall shows decreased T1 values in the lateral wall coinciding with reduced values

Mentions: Parametric T1 and maps acquired in a swine are shown in Fig. 8 and a profile is extracted along the left ventricle. Myocardial T1 values from the 90°-90°-90° SASHA and MOLLI sequences show a >50 % artifactual decrease in the lateral wall, spatially coinciding with reduced values. T1 values using the 6-pulse SASHA sequence were more spatially uniform across both the myocardium (1386 ± 70 ms along the profile) and the overall field of view.Fig. 8


Saturation pulse design for quantitative myocardial T1 mapping.

Chow K, Kellman P, Spottiswoode BS, Nielles-Vallespin S, Arai AE, Salerno M, Thompson RB - J Cardiovasc Magn Reson (2015)

A  map (bottom left) and T1 maps (top row) using SASHA with a reference 90°-90°-90° saturation pulse, SASHA with a proposed 6-pulse train, and MOLLI in a swine. Air regions with low signal intensities are masked for visualization. A profile of T1 values along the left ventricular wall shows decreased T1 values in the lateral wall coinciding with reduced  values
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4589956&req=5

Fig8: A map (bottom left) and T1 maps (top row) using SASHA with a reference 90°-90°-90° saturation pulse, SASHA with a proposed 6-pulse train, and MOLLI in a swine. Air regions with low signal intensities are masked for visualization. A profile of T1 values along the left ventricular wall shows decreased T1 values in the lateral wall coinciding with reduced values
Mentions: Parametric T1 and maps acquired in a swine are shown in Fig. 8 and a profile is extracted along the left ventricle. Myocardial T1 values from the 90°-90°-90° SASHA and MOLLI sequences show a >50 % artifactual decrease in the lateral wall, spatially coinciding with reduced values. T1 values using the 6-pulse SASHA sequence were more spatially uniform across both the myocardium (1386 ± 70 ms along the profile) and the overall field of view.Fig. 8

Bottom Line: The optimized BIR4-90 reduced the maximum residual /MZ/M0/ to <1 %, a 5.8× reduction compared to a reference BIR4-90.An optimized 3-pulse train achieved a maximum residual /MZ/M0/ <1 % for the 1.5 T optimization range compared to 11.3 % for a standard 90°-90°-90° pulse train, while a 6-pulse train met this target for the wider 3 T ranges of B0 and [Formula: see text].Adiabatic and pulse train saturation pulses optimized for different constraints found at 1.5 T and 3 T achieved <1 % residual /MZ/M0/ in phantom experiments, enabling greater accuracy in quantitative saturation recovery T1 imaging.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Faculty of Medicine and Dentistry, 1082 Research Transition Facility, University of Alberta, Edmonton, AB, T6G 2V2, Canada. kelvin.chow@ualberta.ca.

ABSTRACT

Background: Quantitative saturation-recovery based T1 mapping sequences are less sensitive to systematic errors than the Modified Look-Locker Inversion recovery (MOLLI) technique but require high performance saturation pulses. We propose to optimize adiabatic and pulse train saturation pulses for quantitative T1 mapping to have <1 % absolute residual longitudinal magnetization (/MZ/M0/) over ranges of B0 and [Formula: see text] (B1 scale factor) inhomogeneity found at 1.5 T and 3 T.

Methods: Design parameters for an adiabatic BIR4-90 pulse were optimized for improved performance within 1.5 T B0 (±120 Hz) and [Formula: see text] (0.7-1.0) ranges. Flip angles in hard pulse trains of 3-6 pulses were optimized for 1.5 T and 3 T, with consideration of T1 values, field inhomogeneities (B0 = ±240 Hz and [Formula: see text]=0.4-1.2 at 3 T), and maximum achievable B1 field strength. Residual MZ/M0 was simulated and measured experimentally for current standard and optimized saturation pulses in phantoms and in-vivo human studies. T1 maps were acquired at 3 T in human subjects and a swine using a SAturation recovery single-SHot Acquisition (SASHA) technique with a standard 90°-90°-90° and an optimized 6-pulse train.

Results: Measured residual MZ/M0 in phantoms had excellent agreement with simulations over a wide range of B0 and [Formula: see text]. The optimized BIR4-90 reduced the maximum residual /MZ/M0/ to <1 %, a 5.8× reduction compared to a reference BIR4-90. An optimized 3-pulse train achieved a maximum residual /MZ/M0/ <1 % for the 1.5 T optimization range compared to 11.3 % for a standard 90°-90°-90° pulse train, while a 6-pulse train met this target for the wider 3 T ranges of B0 and [Formula: see text]. The 6-pulse train demonstrated more uniform saturation across both the myocardium and entire field of view than other saturation pulses in human studies. T1 maps were more spatially homogeneous with 6-pulse train SASHA than the reference 90°-90°-90° SASHA in both human and animal studies.

Conclusions: Adiabatic and pulse train saturation pulses optimized for different constraints found at 1.5 T and 3 T achieved <1 % residual /MZ/M0/ in phantom experiments, enabling greater accuracy in quantitative saturation recovery T1 imaging.

No MeSH data available.


Related in: MedlinePlus