Demonstration of fast multi‐slice quasi‐steady‐state chemical exchange saturation transfer (QUASS CEST) human brain imaging at 3T

Kim, Hahnsung; Krishnamurthy, Lisa C.; Sun, Phillip Zhe

doi:10.1002/mrm.29028

Cited by 20 publications

(24 citation statements)

References 54 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Adopting multislice or 3D-CEST sequences will undoubtedly improve the clinical CEST imaging. [48][49][50][51] Nevertheless, the 3D-CEST imaging scan time will be prolonged. Therefore, it is critical to implement the QUASS algorithm to account for short Ts/Td to speed up 3D-CEST imaging, particularly helpful at high magnetic fields to alleviate the specific absorption rate.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Demonstration of fast and equilibrium human muscle creatine CEST imaging at 3 T

Liu

Yang

Luo

et al. 2022

Magnetic Resonance in Med

Self Cite

View full text Add to dashboard Cite

Purpose Creatine chemical exchange saturation transfer (CrCEST) MRI is used increasingly in muscle imaging. However, the CrCEST measurement depends on the RF saturation duration (Ts) and relaxation delay (Td), and it is challenging to compare the results of different scan parameters. Therefore, this study aims to evaluate the quasi‐steady‐state (QUASS) CrCEST MRI on clinical 3T scanners. Methods T1 and CEST MRI scans of Ts/Td of 1 s/1 s and 2 s/2 s were obtained from a multi‐compartment creatine phantom and 5 healthy volunteers. The CrCEST effect was quantified with asymmetry analysis in the phantom, whereas 5‐pool Lorentzian fitting was applied to isolate creatine from phosphocreatine, amide proton transfer, combined magnetization transfer and nuclear Overhauser enhancement effects, and direct water saturation in four major muscle groups of the lower leg. The routine and QUASS CrCEST measurements were compared under two different imaging conditions. Paired Student's t‐test was performed with p‐values less than 0.05 considered statistically significant. Results The phantom study showed a substantial influence of Ts/Td on the routine CrCEST quantification (p = 0.02), and such impact was mitigated with the QUASS algorithm (p = 0.20). The volunteer experiment showed that the routine CrCEST, amide proton transfer, and combined magnetization transfer and nuclear Overhauser enhancement effects increased significantly with Ts and Td (p < 0.05) and were significantly smaller than the corresponding QUASS indices (p < 0.01). In comparison, the QUASS CrCEST MRI showed little dependence on Ts and Td, indicating its robustness and accuracy. Conclusion The QUASS CrCEST MRI is feasible to provide fast and accurate muscle creatine imaging.

show abstract

Section: Discussionmentioning

confidence: 99%

“…Third, this study used a single‐slice CEST‐MRI sequence. Adopting multislice or 3D‐CEST sequences will undoubtedly improve the clinical CEST imaging 48–51 . Nevertheless, the 3D‐CEST imaging scan time will be prolonged.…”

Section: Discussionmentioning

confidence: 99%

Demonstration of fast and equilibrium human muscle creatine CEST imaging at 3 T

Liu

Yang

Luo

et al. 2022

Magnetic Resonance in Med

Self Cite

View full text Add to dashboard Cite

show abstract

“…shows that the signal built up is in first order, given by e ÀR1ρÁTprep towards Equation (10). Interestingly, the dynamic rate and the steady-state magnetization are governed by the same rate constant R 1p, which leads to the fact that the transient and steady-state values can be transformed into each other, first described by Breitling et al 9 and recently explored in detail by Sun et al [10][11][12][13] The principal idea here is that the dynamic constant R 1ρ Δω ð Þ can be expressed by the steady-state Z-value and vice versa; reforming Equation (3) yields the off-resonant R 1ρ from the steady-state Zvalue and R 1obs :…”

Section: Transient Statementioning

confidence: 96%

“…For shorter preparation times, a dynamic or transient state version of the signal equation can be derived for Z ref and Z label from Equation (2), which shows that the signal built up is in first order, given by

e^{- R_{1 ρ} \cdot T_{prep}}

towards Equation (10). Interestingly, the dynamic rate and the steady‐state magnetization are governed by the same rate constant R 1p, which leads to the fact that the transient and steady‐state values can be transformed into each other, first described by Breitling et al 9 and recently explored in detail by Sun et al 10–13 The principal idea here is that the dynamic constant

R_{1 ρ} ((), Δω)

can be expressed by the steady‐state Z‐value and vice versa; reforming Equation (3) yields the off‐resonant

R_{1 ρ}

from the steady‐state Z‐value and R 1obs :

R_{1 ρ} ((), Δω) = P^{2} \frac{R_{1 italicobs}}{Z^{ss} ((), Δω)}

The key idea is that we can think of Z ss as a function of

R_{1 ρ}

, or we can think of

R_{1 ρ}

as a function of Z ss . So long as Z rec is greater than 0, Equation (2) is invertible and the dependencies on Z ss or

R_{1 ρ}

are monotonic.…”

Section: The Cest Signal Equationmentioning

confidence: 99%

Theory of chemical exchange saturation transfer MRI in the context of different magnetic fields

et al. 2022

View full text Add to dashboard Cite

Chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) is a versatile MRI method that provides contrast based on the level of molecular and metabolic activity. This contrast arises from indirect measurement of protons in low concentration molecules that are exchanging with the abundant water proton pool. The indirect measurement is based on magnetization transfer of radio frequency (rf)‐prepared magnetization from the small pool to the water pool. The signal can be modeled by the Bloch–McConnell equations combining standard magnetization dynamics and chemical exchange processes. In this article, we review analytical solutions of the Bloch–McConnell equations and especially the derived CEST signal equations and their implications. The analytical solutions give direct insight into the dependency of measurable CEST effects on underlying parameters such as the exchange rate and concentration of the solute pools, but also on the system parameters such as the rf irradiation field B1, as well as the static magnetic field B0. These theoretical field‐strength dependencies and their influence on sequence design are highlighted herein. In vivo results of different groups making use of these field‐strength benefits/dependencies are reviewed and discussed.

show abstract

“…Recently, a quasi–steady‐state (QUASS) CEST analysis has been established to derive the equilibrium CEST effect (i.e., long Ts and Td) from the experimental measurements, improving the quantification of the underlying CEST system 48–53 . Kim et al examined QUASS CEST MRI for a CEST sequence with a multi‐slice readout after a single RF saturation pulse 54 . Although multi‐slice readout can be obtained after a single RF labeling pulse, each subsequent slice suffers an additional loss of CEST effect due to post‐saturation delay 55 .…”

Section: Introductionmentioning

confidence: 99%

Quasi–steady‐state amide proton transfer (QUASS APT) MRI enhances pH‐weighted imaging of acute stroke

Sun

2022

Magnetic Resonance in Med

Self Cite

View full text Add to dashboard Cite

Purpose: Chemical exchange saturation transfer (CEST) imaging measurement depends not only on the labile proton concentration and pH-dependent exchange rate but also on experimental conditions, including the relaxation delay and radiofrequency (RF) saturation time. Our study aimed to extend a quasi-steady-state (QUASS) solution to a modified multi-slice CEST MRI sequence and test if it provides enhanced pH imaging after acute stroke. Methods: Our study derived the QUASS solution for a modified multislice CEST MRI sequence with an unevenly segmented RF saturation between image readout and signal averaging. Numerical simulation was performed to test if the generalized QUASS solution corrects the impact of insufficiently long relaxation delay, primary and secondary saturation times, and multi-slice readout. In addition, multiparametric MRI scans were obtained after middle cerebral artery occlusion, including relaxation and CEST Z-spectrum, to evaluate the performance of QUASS CEST MRI in a rodent acute stroke model. We also performed Lorentzian fitting to isolate multi-pool CEST contributions. Results:The QUASS analysis enhanced pH-weighted magnetization transfer asymmetry contrast over the routine apparent CEST measurements in both contralateral normal (−3.46% ± 0.62% (apparent) vs. −3.67% ± 0.66% (QUASS), P < 0.05) and ischemic tissue (−5.53% ± 0.68% (apparent) vs. −5.94% ± 0.73% (QUASS), P < 0.05). Lorentzian fitting also showed significant differences between routine and QUASS analysis of ischemia-induced changes in magnetization transfer, amide, amine, guanidyl CEST, and nuclear Overhauser enhancement (−1.6 parts per million) effects. Conclusion:Our study demonstrated that generalized QUASS analysis enhanced pH MRI contrast and improved quantification of the underlying CEST contrast mechanism, promising for further in vivo applications. K E Y W O R D Samide proton transfer (APT), CEST, magnetization transfer MTR asymmetry (MTR asym ), pH imaging, stroke This study was supported by a National Institutes of Health (NIH), grant R01NS083654 (p.z.s.).

show abstract

Demonstration of fast multi‐slice quasi‐steady‐state chemical exchange saturation transfer (QUASS CEST) human brain imaging at 3T

Cited by 20 publications

References 54 publications

Demonstration of fast and equilibrium human muscle creatine CEST imaging at 3 T

Demonstration of fast and equilibrium human muscle creatine CEST imaging at 3 T

Theory of chemical exchange saturation transfer MRI in the context of different magnetic fields

Quasi–steady‐state amide proton transfer (QUASS APT) MRI enhances pH‐weighted imaging of acute stroke

Contact Info

Product

Resources

About