PRO‐QUEST: a rapid assessment method based on progressive saturation for quantifying exchange rates using saturation times in CEST

Demetriou, Eleni; Tachrount, Mohamed; Zaiß, Moritz; Shmueli, Karin; Golay, Xavier

doi:10.1002/mrm.27155

Cited by 10 publications

(22 citation statements)

References 39 publications

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“…[28][29][30][31] Ideally, for providing the most useful estimation of the metabolite of interest, the actual physical CEST propertiesproton exchange rate, and solute concentration should be mapped. In accordance, various efforts were previously taken to achieve quantitative CEST imaging 32 such as the quantitation of exchange using saturation power (QUESP) or time (QUEST) [33][34][35] and Omega plot 36 methods. These methods exploit the dependency of the CEST signal on the saturation power (or saturation time) and fit the MTR asym for a single offset as a function of the saturation parameter to estimate the labile proton volume fraction and exchange rate.…”

Section: Introductionmentioning

confidence: 99%

CEST MR‐Fingerprinting: Practical considerations and insights for acquisition schedule design and improved reconstruction

Perlman

Herz

Zaiß

et al. 2019

Magnetic Resonance in Med

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Purpose: To understand the influence of various acquisition parameters on the ability of CEST MR-Fingerprinting (MRF) to discriminate different chemical exchange parameters and to provide tools for optimal acquisition schedule design and parameter map reconstruction. Methods: Numerical simulations were conducted using a parallel computing implementation of the Bloch-McConnell equations, examining the effect of TR, TE, flip-angle, water T 1 and T 2 , saturation-pulse duration, power, and frequency on the discrimination ability of CEST-MRF. A modified Euclidean distance matching metric was evaluated and compared to traditional dot product matching. L-Arginine phantoms of various concentrations and pH were scanned at 4.7T and the results compared to numerical findings. Results: Simulations for dot product matching demonstrated that the optimal flipangle and saturation times are 30 • and 1100 ms, respectively. The optimal maximal saturation power was 3.4 μT for concentrated solutes with a slow exchange rate, and 5.2 μT for dilute solutes with medium-to-fast exchange rates. Using the Euclidean distance matching metric, much lower maximum saturation powers were required (1.6 and 2.4 μT, respectively), with a slightly longer saturation time (1500 ms) and 90 • flip-angle. For both matching metrics, the discrimination ability increased with the repetition time. The experimental results were in agreement with simulations, demonstrating that more than a 50% reduction in scan-time can be achieved by Euclidean distance-based matching. Conclusions: Optimization of the CEST-MRF acquisition schedule is critical for obtaining the best exchange parameter accuracy. The use of Euclidean distance-based matching of signal trajectories simultaneously improved the discrimination ability and reduced the scan time and maximal saturation power required. |

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Section: Introductionmentioning

confidence: 99%

CEST MR‐Fingerprinting: Practical considerations and insights for acquisition schedule design and improved reconstruction

Perlman

Herz

Zaiß

et al. 2019

Magnetic Resonance in Med

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“…Second, the PRO-QUEST method with single irradiation frequency might be susceptible to B0 shifts. As the previous pre-clinical study reported, this could be mitigated by using broad bandwidth saturation pulses (21). A bandwidth of 300 Hz was used in the present study in consideration of the B0 effect.…”

Section: Discussionmentioning

confidence: 99%

“…The PRO-QUEST sequence was originally developed on a 9.4T pre-clinical scanner to reduce the time for measuring chemical exchange rates (21). In this method, an initial saturation pulse sequence is followed by delays ( Figure 1A) or off-resonance saturation pulses ( Figure 1B) interleaved under non-steady-state conditions while the water magnetization is sampled subsequently through a Look-Locker acquisition until a steady-state magnetization is reached.…”

Section: Methodsmentioning

confidence: 99%

“…(21).In healthy volunteers, the PRO-QUEST image of signal evolution at the final sampling point and the corresponding saturation recovery curves show clear contrast between WM, GM and cerebrospinal fluid (CSF) (Figure 4Band 4E) contrary to the Look-Locker image (Figure 4A) and the corresponding saturation recovery curves (without off-resonance saturation pulses) (Figure 4D), which is primarily based on water content M0. This confirms the effect of progressive CEST pulses and magnetisation transfer (MT).…”

mentioning

confidence: 94%

“…Recently, a novel CEST pulse sequence called PRO‐QUEST (Progressive saturation for quantifying exchange rates using saturation times) has demonstrated the feasibility of estimating pH sensitive metrics independent of concentration, both in phantoms and in vivo ischemic rat brains at 9.4T. Here, we aim to translate the PRO‐QUEST sequence to a 3T clinical scanner and demonstrate estimation of pH‐sensitive indices in phantoms with various pH values and apply the method to assess in vivo human neural tissues.…”

Section: Introductionmentioning

confidence: 99%

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Translating pH‐sensitive PROgressive saturation for QUantifying Exchange rates using Saturation Times (PRO‐QUEST) MRI to a 3T clinical scanner

Kim

Kujawa

Battiston

et al. 2020

Magnetic Resonance in Med

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Purpose: To translate the recently developed PRO-QUEST (Progressive saturation for quantifying exchange using saturation times) sequence from preclinical 9.4T to 3T clinical magnetic field strength. Methods: Numerical simulations were performed to define the optimal saturation flip angles for PRO-QUEST saturation pulses of at 3T and demonstrate the effect of a ∆T2 error on the exchange rate (kex) estimation at various field strengths. Exchange dependent relaxation rate (Rex) was measured for glutamate solutions in various pH, healthy volunteers and patients with multiple sclerosis (MS). Additionally, concentration-independent ratiometric Rex maps were produced to evaluate regional signal variations across the brain of human volunteers. Results: The calculated Rex significantly correlates with pH in glutamate samples, however kex values are underestimated as compared to those previously obtained at 9.4T. In the ratiometric Rex map of healthy volunteers, no significant differences are found between grey matter, white matter and basal ganglia. In patients with MS, white matter lesions are visible in single saturation power Rex maps whilst only a periventricular lesion is apparent in the ratiometric Rex map. Conclusion: We demonstrate that quantification of pH sensitive indices using PRO-QUEST is feasible at 3T within clinically acceptable acquisition times. Our initial findings in patients with MS show that pH sensitive indices varied with the type of lesion examined whilst no significant difference was found in healthy volunteers between tissue types, suggesting that it would be worthwhile to apply PRO-QUEST in a larger cohort of patients to better understand its distinct imaging features relative to conventional techniques.

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MR fingerprinting for semisolid magnetization transfer and chemical exchange saturation transfer quantification

2022

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Chemical exchange saturation transfer (CEST) MRI has positioned itself as a promising contrast mechanism, capable of providing molecular information at sufficient resolution and amplified sensitivity. However, it has not yet become a routinely employed clinical technique, due to a variety of confounding factors affecting its contrast-weighted image interpretation and the inherently long scan time. CEST MR fingerprinting (MRF) is a novel approach for addressing these challenges, allowing simultaneous quantitation of several proton exchange parameters using rapid acquisition schemes. Recently, a number of deep-learning algorithms have been developed to further boost the performance and speed of CEST and semi-solid macromolecule magnetization transfer (MT) MRF. This review article describes the fundamental theory behind semisolid MT/CEST-MRF and its main applications. It then details supervised and unsupervised learning approaches for MRF image reconstruction and describes artificial intelligence (AI)-based pipelines for protocol optimization. Finally, practical considerations are discussed, and future perspectives are given, accompanied by basic demonstration code and data.

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PRO‐QUEST: a rapid assessment method based on progressive saturation for quantifying exchange rates using saturation times in CEST

Abstract: Because of the reduced scan time and insensitivity to nonchemical exchange factors such as direct water saturation, PRO-QUEST can serve as an excellent alternative for researchers and clinicians interested to map pH changes in vivo.

Cited by 10 publications

References 39 publications

CEST MR‐Fingerprinting: Practical considerations and insights for acquisition schedule design and improved reconstruction

CEST MR‐Fingerprinting: Practical considerations and insights for acquisition schedule design and improved reconstruction

Translating pH‐sensitive PROgressive saturation for QUantifying Exchange rates using Saturation Times (PRO‐QUEST) MRI to a 3T clinical scanner

MR fingerprinting for semisolid magnetization transfer and chemical exchange saturation transfer quantification

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