Demonstration of fast and equilibrium human muscle creatine CEST imaging at <scp>3 T</scp>

Liu, Zhou; Yang, Qian; Luo, Honghong; Luo, Dingcun; Qian, Long; Liu, Xin; Zheng, Hairong; Sun, Phillip Zhe; Wu, Yin

doi:10.1002/mrm.29223

Cited by 10 publications

(18 citation statements)

References 53 publications

(102 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Due to the low exchange rates, the CrCEST signal is still strong in the GuanCEST with low B 1 values (0.8 μT) and contributes less than 25% of the total GuanCEST for the B 1 = 0.8–2.0 μT (Figures 1C–E). Therefore, careful analysis is required when interpreting the CrCEST signal extracted with the multi‐Lorentzian fitting approach, in which the CrCEST contribution is even lower than 25% due to the presence of other NOE and CEST signals at 1.95 ppm in the brain 20,48,49 . When applying this PLOF approach for Cr mapping in muscle, the CrCEST contribution at 1.95 ppm can be significantly higher due to the high concentration of Cr and low level of protein GuanCEST 22 .…”

Section: Discussionmentioning

confidence: 99%

The exchange rate of creatine CEST in mouse brain

Zhang

Wang

Park

et al. 2023

Magnetic Resonance in Med

View full text Add to dashboard Cite

Purpose:To estimate the exchange rate of creatine (Cr) CEST and to evaluate the pH sensitivity of guanidinium (Guan) CEST in the mouse brain. Methods: Polynomial and Lorentzian line-shape fitting (PLOF) were implemented to extract the amine, amide, and Guan CEST signals from the brain Z-spectrum at 11.7T. Wild-type (WT) and knockout mice with the guanidinoacetate N-methyltransferase deficiency (GAMT −/− ) that have low Cr and phosphocreatine (PCr) concentrations in the brain were used to extract the CrCEST signal. To quantify the CrCEST exchange rate, a two-step Bloch-McConnell (BM) fitting was used to fit the CrCEST line-shape, B 1 -dependent CrCEST, and the pH response with different B 1 values. The pH in the brain cells was altered by hypercapnia to measure the pH sensitivity of GuanCEST.Results: Comparison between the Z-spectra of WT and GAMT −/− mice suggest that the CrCEST is between 20% and 25% of the GuanCEST in the Z-spectrum at 1.95 ppm between B 1 = 0.8 and 2 μT. The CrCEST exchange rate was found to be around 240-480 s −1 in the mouse brain, which is significantly lower than that in solutions (∼1000 s −1 ). The hypercapnia study on the mouse brain revealed that CrCEST at B 1 = 2 μT and amineCEST at B 1 = 0.8 μT are highly sensitive to pH change in the WT mouse brain. Conclusions:The in vivo CrCEST exchange rate is slow, and the acquisition parameters for the CrCEST should be adjusted accordingly. CrCEST is the major contribution to the opposite pH-dependence of GuanCEST signal under different conditions of B 1 in the brain. K E Y W O R D S amide CEST, amine CEST, chemical exchange saturation transfer (CEST), concentration, creatine CEST (CrCEST), exchange rate, guanidinium CEST (GuanCEST), high spectral resolution (HSR) CEST, polynomial Lorentzian line-shape fitting (PLOF), two-step Bloch-McConnell (BM) fitting Ziqin Zhang and Kexin Wang contributed equally to this work.

show abstract

Section: Discussionmentioning

confidence: 99%

The exchange rate of creatine CEST in mouse brain

Zhang

Wang

Park

et al. 2023

Magnetic Resonance in Med

View full text Add to dashboard Cite

show abstract

“…Because the NOE effect exhibits multiple peaks and their origins have not been fully established, our study focused on downfield CEST effects. In short, the inverse Z‐spectrum from 1 to 6 ppm was fitted with MT (−1.5 ppm), direct water saturation (DWS) (0 ppm), CEST@2 ppm, amine (2.75 ppm), and APT (3.5 ppm) effects 42,43 . The nonlinearly constrained fitting routine was performed with constraints allowing peak amplitude and line width to vary from 0.2‐ to 5‐fold the initial guesses, and the peak frequency offsets were ±0.2 ppm of each chemical shift.…”

Section: Methodsmentioning

confidence: 99%

Demonstration of pH imaging in acute stroke with endogenous ratiometric chemical exchange saturation transfer magnetic resonance imaging at 2 ppm

Sun

2022

NMR in Biomedicine

Self Cite

View full text Add to dashboard Cite

pH change is often considered a hallmark of metabolic disruption in diseases such as ischemic stroke and cancer. Chemical exchange saturation transfer (CEST) MRI, particularly amide proton transfer (APT), has emerged as a noninvasive pH imaging approach. However, there are changes in multipool CEST effects besides APT MRI. Our study investigated radiofrequency (RF) amplitude‐based ratiometric CEST pH imaging in acute stroke. Briefly, adult male Wistar rats underwent CEST MRI under two RF saturation (B1) levels of 0.75 and 1.5 μT following middle cerebral artery occlusion. Magnetization transfer (MT), direct water saturation, CEST at 2 ppm (CEST@2 ppm), amine (2.75 ppm), and APT (3.5 ppm) effects were resolved with the multipool Lorentzian fitting approach. The ratiometric analysis was measured in the ischemic lesion and the contralateral normal area, which was also correlated with pH‐specific MT and the relaxation normalized APT (MRAPT) index. MT, amine CEST effect, and their respective ratiometric indices did not show significant changes in ischemic regions (p > 0.05), as expected. Whereas APT decreased in the ischemic lesion for B1 of 1.5 μT (p < 0.01), the correlation between the amide ratio with MRAPT index was moderate (r = 0.52, p = 0.02). By comparison, the ischemic tissue showed a significantly increased CEST@2 ppm for both saturation levels from the contralateral normal area (p ≤ 0.01). Importantly, the CEST@2 ppm ratio decreased in the ischemic lesion (p < 0.01), which highly correlated with the MRAPT index (r = 0.93, p < 0.001). To summarize, our study demonstrated the feasibility of endogenous CEST@2 ppm ratiometric imaging of pH upon acute stroke, promising to detect pH changes in metabolic diseases.

show abstract

“…[36][37][38][39][40] A quasi-steady-state (QUASS) analysis has been recently introduced to reconstruct the equilibrium CEST results from experimental data, which has been extended to further account for the effects of post-saturation delay and an arbitrary flip angle excitation. [41][42][43][44][45] It helps to examine if CEST quantification, such as Lorentzian (model-free) and spinlock (model-based) fittings, can benefit from QUASS reconstruction to resolve multi-pool contributions accurately. 35 Our study first simulated Z-spectra using classical three-pool Bloch-McConnell equations (amide, guanidine, and bulk water signals) under serially varied Ts, Td, and T 1 parameters.…”

Section: Introductionmentioning

confidence: 99%

Comparison of model‐free Lorentzian and spinlock model‐based fittings in quantitative CEST imaging of acute stroke

Sun

2023

Magnetic Resonance in Med

Self Cite

View full text Add to dashboard Cite

PurposeCEST MRI detects complex tissue changes following acute stroke. Our study aimed to test if spinlock model‐based fitting of the quasi‐steady‐state (QUASS)‐reconstructed equilibrium CEST MRI improves the determination of multi‐pool signal changes over the commonly‐used model‐free Lorentzian fitting in acute stroke.Theory and MethodsMultiple three‐pool CEST Z‐spectra were simulated using Bloch‐McConnell equations for a range of T1, relaxation delay, and saturation times. The multi‐pool CEST signals were solved from the simulated Z‐spectra to test the accuracy of routine Lorentzian (model‐free) and spinlock (model‐based) fittings without and with QUASS reconstruction. In addition, multiparametric MRI scans were obtained in rat models of acute stroke, including relaxation, diffusion, and CEST Z‐spectrum. Finally, we compared model‐free and model‐based per‐pixel CEST quantification in vivo.ResultsThe spinlock model‐based fitting of QUASS CEST MRI provided a nearly T1‐independent determination of multi‐pool CEST signals, advantageous over the fittings of apparent CEST MRI (model‐free and model‐based). In vivo data also demonstrated that the spinlock model‐based QUASS fitting captured significantly different changes in semisolid magnetization transfer (−0.9 ± 0.8 vs. 0.3 ± 0.8%), amide (−1.1 ± 0.4 vs. −0.5 ± 0.2%), and guanidyl (1.0 ± 0.4 vs. 0.7 ± 0.3%) signals over the model‐free Lorentzian analysis.ConclusionOur study demonstrated that spinlock model‐based fitting of QUASS CEST MRI improved the determination of the underlying tissue changes following acute stroke, promising further clinical translation of quantitative CEST imaging.

show abstract

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

Cited by 10 publications

References 53 publications

The exchange rate of creatine CEST in mouse brain

The exchange rate of creatine CEST in mouse brain

Demonstration of pH imaging in acute stroke with endogenous ratiometric chemical exchange saturation transfer magnetic resonance imaging at 2 ppm

Comparison of model‐free Lorentzian and spinlock model‐based fittings in quantitative CEST imaging of acute stroke

Contact Info

Product

Resources

About