Improving the detection sensitivity of p<scp>H</scp>‐weighted amide proton transfer <scp>MRI</scp> in acute stroke patients using extrapolated semisolid magnetization transfer reference signals

Heo, Hye Young; Zhang, Yi; Burton, Tina; Jiang, Shanshan; Zhao, Yongbo; Zijl, Peter C.M. van; Leigh, R. John; Zhou, Jinyuan

doi:10.1002/mrm.26799

Cited by 82 publications

(146 citation statements)

References 77 publications

Supporting

Mentioning

138

Contrasting

Order By: Relevance

“…For six‐pool model simulations and experiments, to avoid the effects of rNOE and asymmetric MT, we used the EMR method to fit the reference signals for the quantification of CEST signals, and derived the metrics as MTR EMR , AREX EMR , R ex_EMR and Δ R ex_EMR , respectively. Specifically for EMR, CEST data with Δ ω from –6500 to –3500 Hz and 3500 to 6500 Hz and ω 1 of 3.6 μT, and with Δ ω from –4000 to –2500 Hz and 2500 to 4000–Hz and ω 1 of 1.0 μT, were fitted to a two‐pool MT model (see Appendix).…”

Section: Methodsmentioning

confidence: 99%

“…Therefore, MTR asym does not accurately report specific information on composition. Thus, to avoid some of these confounding factors, other approaches, such as an extrapolated semi‐solid MT reference (EMR) approach, a Lorentzian difference (LD) analysis and a three‐point method, etc., have been developed. To further increase the specificity of CEST4 metrics, an inverse subtraction method which takes account of variations in T 1w , named apparent exchange‐dependent relaxation (AREX), has also been developed .…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Increased CEST specificity for amide and fast‐exchanging amine protons using exchange‐dependent relaxation rate

Zhang

Wang

et al. 2017

NMR in Biomedicine

View full text Add to dashboard Cite

Chemical exchange saturation transfer (CEST) imaging of amides at 3.5 ppm and fast-exchanging amines at 3 ppm provides a unique means to enhance the sensitivity of detection of, for example, proteins/peptides and neurotransmitters, respectively, and hence can provide important information on molecular composition. However, despite the high sensitivity relative to conventional magnetic resonance spectroscopy (MRS), in practice, CEST often has relatively poor specificity. For example, CEST signals are typically influenced by several confounding effects, including direct water saturation (DS), semi-solid non-specific magnetization transfer (MT), the influence of water relaxation times (T ) and nearby overlapping CEST signals. Although several editing techniques have been developed to increase the specificity by removing DS, semi-solid MT and T influences, it is still challenging to remove overlapping CEST signals from different exchanging sites. For instance, the amide proton transfer (APT) signal could be contaminated by CEST effects from fast-exchanging amines at 3 ppm and intermediate-exchanging amines at 2 ppm. The current work applies an exchange-dependent relaxation rate (R ) to address this problem. Simulations demonstrate that: (1) slowly exchanging amides and fast-exchanging amines have distinct dependences on irradiation powers; and (2) R serves as a resonance frequency high-pass filter to selectively reduce CEST signals with resonance frequencies closer to water. These characteristics of R provide a means to isolate the APT signal from amines. In addition, previous studies have shown that CEST signals from fast-exchanging amines have no distinct features around their resonance frequencies. However, R gives Lorentzian lineshapes centered at their resonance frequencies for fast-exchanging amines and thus can significantly increase the specificity of CEST imaging for amides and fast-exchanging amines.

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Increased CEST specificity for amide and fast‐exchanging amine protons using exchange‐dependent relaxation rate

Zhang

Wang

et al. 2017

NMR in Biomedicine

View full text Add to dashboard Cite

show abstract

“…While these two effects act synergistically and add up in the APTw MRI contrast of brain tumors due to the considerable MTC asymmetry at higher B 1 , they do not for pH assessment in ischemic stroke, where the pH dependence of the rNOE effect compensates a part of the pH dependence of the APT signal. To address this and illustrate the detrimental effect of the MTR asym (3.5 ppm) approach, Heo et al performed a study in ischemic stroke patients using the EMR approach, confirming pH effects in both quantitative APT # and NOE # images. Use of the more specific APT # images showed a great enhancement of the APT MRI sensitivity to pH compared with conventional APTw MRI (Fig.…”

Section: Current Applicationsmentioning

confidence: 99%

“…Use of the more specific APT # images showed a great enhancement of the APT MRI sensitivity to pH compared with conventional APTw MRI (Fig. ), allowing a more reliable delineation of the acidosis penumbra . It is expected that the pH/diffusion mismatch will be better than the current standard of care criteria (perfusion/diffusion mismatch) at identifying the true viable tissue area at risk of infarction, ie, the ischemic penumbra.…”

Section: Current Applicationsmentioning

confidence: 99%

See 1 more Smart Citation

APT‐weighted MRI: Techniques, current neuro applications, and challenging issues

Zhou

Heo

Knutsson

et al. 2019

Magnetic Resonance Imaging

Self Cite

255

329

View full text Add to dashboard Cite

Amide proton transfer‐weighted (APTw) imaging is a molecular MRI technique that generates image contrast based predominantly on the amide protons in mobile cellular proteins and peptides that are endogenous in tissue. This technique, the most studied type of chemical exchange saturation transfer imaging, has been used successfully for imaging of protein content and pH, the latter being possible due to the strong dependence of the amide proton exchange rate on pH. In this article we briefly review the basic principles and recent technical advances of APTw imaging, which is showing promise clinically, especially for characterizing brain tumors and distinguishing recurrent tumor from treatment effects. Early applications of this approach to stroke, Alzheimer's disease, Parkinson's disease, multiple sclerosis, and traumatic brain injury are also illustrated. Finally, we outline the technical challenges for clinical APT‐based imaging and discuss several controversies regarding the origin of APTw imaging signals in vivo. Level of Evidence: 3 Technical Efficacy Stage: 3 J. Magn. Reson. Imaging 2019;50:347–364.

show abstract

CEST, ASL, and magnetization transfer contrast: How similar pulse sequences detect different phenomena

Knutsson

Ahlgren

et al. 2018

Magnetic Resonance in Med

View full text Add to dashboard Cite

Chemical exchange saturation transfer (CEST), arterial spin labeling (ASL), and magnetization transfer contrast (MTC) methods generate different contrasts for MRI. However, they share many similarities in terms of pulse sequences and mechanistic principles. They all use RF pulse preparation schemes to label the longitudinal magnetization of certain proton pools and follow the delivery and transfer of this magnetic label to a water proton pool in a tissue region of interest, where it accumulates and can be detected using any imaging sequence. Due to the versatility of MRI, differences in spectral, spatial or motional selectivity of these schemes can be exploited to achieve pool specificity, such as for arterial water protons in ASL, protons on solute molecules in CEST, and protons on semi-solid cell structures in MTC. Timing of these sequences can be used to optimize for the rate of a particular delivery and/or exchange transfer process, for instance, between different tissue compartments (ASL) or between tissue molecules (CEST/MTC). In this review, magnetic labeling strategies for ASL and the corresponding CEST and MTC pulse sequences are compared, including continuous labeling, single-pulse labeling, and multi-pulse labeling. Insight into the similarities and differences among these techniques is important not only to comprehend the mechanisms and confounds of the contrasts they generate, but also to stimulate the development of new MRI techniques to improve these contrasts or to reduce their interference. This, in turn, should benefit many possible applications in the fields of physiological and molecular imaging and spectroscopy.

show abstract

Improving the detection sensitivity of pH‐weighted amide proton transfer MRI in acute stroke patients using extrapolated semisolid magnetization transfer reference signals

Cited by 82 publications

References 77 publications

Increased CEST specificity for amide and fast‐exchanging amine protons using exchange‐dependent relaxation rate

Increased CEST specificity for amide and fast‐exchanging amine protons using exchange‐dependent relaxation rate

APT‐weighted MRI: Techniques, current neuro applications, and challenging issues

CEST, ASL, and magnetization transfer contrast: How similar pulse sequences detect different phenomena

Contact Info

Product

Resources

About