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

Zaiß, Moritz; Jin, Tao; Kim, Seong‐Gi; Gochberg, Daniel F.

doi:10.1002/nbm.4789

Cited by 25 publications

(39 citation statements)

References 72 publications

(139 reference statements)

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“…However, another study has shown that APT imaging at 3.5 ppm using B 1,RMS = 1.0 μT performed on two human brains also results in an appropriate APT effect 27 suggesting that the inclusion of saturation with low power (in addition to high power) is still beneficial. Also, the steady‐state optimal B 1 amplitude has been described for a system with a free water pool and a CEST pool 28 . It is a function of the T 1 and T 2 of the free water pool, the solute‐to‐free‐water‐pool exchange rate k s , and frequency offset.…”

Section: Discussionmentioning

confidence: 99%

Chemical Exchange Saturation Transfer MRI for Differentiating Radiation Necrosis From Tumor Progression in Brain Metastasis—Application in a Clinical Setting

Mehrabian

Chan

Sahgal

et al. 2022

Magnetic Resonance Imaging

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Background High radiation doses of stereotactic radiosurgery (SRS) for brain metastases (BM) can increase the likelihood of radiation necrosis (RN). Advanced MRI sequences can improve the differentiation between RN and tumor progression (TP). Purpose To use saturation transfer MRI methods including chemical exchange saturation transfer (CEST) and magnetization transfer (MT) to distinguish RN from TP. Study Type Prospective cohort study. Subjects Seventy patients (median age 60; 73% females) with BM (75 lesions) post‐SRS. Field Strength/Sequence 3‐T, CEST imaging using low/high‐power (saturation B1 = 0.52 and 2.0 μT), quantitative MT imaging using B1 = 1.5, 3.0, and 5.0 μT, WAter Saturation Shift Referencing (WASSR), WAter Shift And B1 (WASABI), T1, and T2 mapping. All used gradient echoes except T2 mapping (gradient and spin echo). Assessment Voxel‐wise metrics included: magnetization transfer ratio (MTR); apparent exchange‐dependent relaxation (AREX); MTR asymmetry; normalized MT exchange rate and pool size product; direct water saturation peak width; and the observed T1 and T2. Regions of interests (ROIs) were manually contoured on the post‐Gd T1w. The mean (of median ROI values) was compared between groups. Clinical outcomes were determined by clinical and radiologic follow‐up or histopathology. Statistical Tests t‐Test, univariable and multivariable logistic regression, receiver operating characteristic, and area under the curve (AUC) with sensitivity/specificity values with the optimal cut point using the Youden index, Akaike information criterion (AIC), Cohen's d. P < 0.05 with Bonferroni correction was considered significant. Results Seven metrics showed significant differences between RN and TP. The high‐power MTR showed the highest AUC of 0.88, followed by low‐power MTR (AUC = 0.87). The combination of low‐power CEST scans improved the separation compared to individual parameters (with an AIC of 70.3 for low‐power MTR/AREX). Cohen's d effect size showed that the MTR provided the largest effect sizes among all metrics. Data Conclusion Significant differences between RN and TP were observed based on saturation transfer MRI. Evidence Level: 3 Technical Efficacy: Stage 2

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Section: Discussionmentioning

confidence: 99%

Chemical Exchange Saturation Transfer MRI for Differentiating Radiation Necrosis From Tumor Progression in Brain Metastasis—Application in a Clinical Setting

Mehrabian

Chan

Sahgal

et al. 2022

Magnetic Resonance Imaging

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“…Since this approach is based on the assumption that the water saturation profile is perfectly asymmetric without CEST agents, there are increasing effects to improve the methods of quantifying CEST images. The Web site () and review articles by Zaiss et al , provided in-depth descriptions of CEST theory, mathematical modeling using Bloch-McConnell equations, and quantifying Z-spectral data, along with several examples.…”

Section: Cest Based Molecular Imagingmentioning

confidence: 99%

Label-Free Chemically and Molecularly Selective Magnetic Resonance Imaging

Liu

Thamizhchelvan

et al. 2023

Chemical & Biomedical Imaging

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Biomedical imaging, especially molecular imaging, has been a driving force in scientific discovery, technological innovation, and precision medicine in the past two decades. While substantial advances and discoveries in chemical biology have been made to develop molecular imaging probes and tracers, translating these exogenous agents to clinical application in precision medicine is a major challenge. Among the clinically accepted imaging modalities, magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) exemplify the most effective and robust biomedical imaging tools. Both MRI and MRS enable a broad range of chemical, biological and clinical applications from determining molecular structures in biochemical analysis to imaging diagnosis and characterization of many diseases and image-guided interventions. Using chemical, biological, and nuclear magnetic resonance properties of specific endogenous metabolites and native MRI contrast-enhancing biomolecules, label-free molecular and cellular imaging with MRI can be achieved in biomedical research and clinical management of patients with various diseases. This review article outlines the chemical and biological bases of several label-free chemically and molecularly selective MRI and MRS methods that have been applied in imaging biomarker discovery, preclinical investigation, and image-guided clinical management. Examples are provided to demonstrate strategies for using endogenous probes to report the molecular, metabolic, physiological, and functional events and processes in living systems, including patients. Future perspectives on label-free molecular MRI and its challenges as well as potential solutions, including the use of rational design and engineered approaches to develop chemical and biological imaging probes to facilitate or combine with label-free molecular MRI, are discussed.

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“…CEST MRI has recently taken center stage due to the rapid development of CEST methodologies 19,20 . A significant advantage of CEST MRI is that it allows for the detection of contrast based on natural metabolites such as amino acids 21 , peptides [22][23][24] , and sugars 25,26 , along with sensitivity to pH [27][28][29] , making it suitable for clinical imaging 30 .…”

Section: -Introductionmentioning

confidence: 99%

Development of a Synthetic Biosensor for Chemical Exchange MRI UtilizingIn SilicoOptimized Peptides

Fillion

Bricco

Lee

et al. 2023

Preprint

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Chemical Exchange Saturation Transfer (CEST) magnetic resonance imaging (MRI) has been identified as a novel alternative to classical diagnostic imaging. Over the last several decades, many studies have been conducted to determine possible CEST agents, such as endogenously expressed compounds or proteins, that can be utilized to produce contrast with minimally invasive procedures and reduced or non-existent levels of toxicity. In recent years there has been an increased interest in the generation of genetically engineered CEST contrast agents, typically based on existing proteins with CEST contrast or modified to produce CEST contrast. We have developed an in-silico method for the evolution of peptide sequences to optimize CEST contrast and showed that these peptides could be combined to create de novo biosensors for CEST MRI. A single protein, superCESTide 2.0, was designed to be 198 amino acids. SuperCESTide 2.0 was expressed in E. coli and purified with size-exclusion chromatography. The magnetic transfer ratio asymmetry (MTRasym) generated by superCESTide 2.0 was comparable to levels seen in previous CEST reporters, such as protamine sulfate (salmon protamine, SP), Poly-L-Lysine (PLL), and human protamine (hPRM1). This data shows that novel peptides with sequences optimized in silico for CEST contrast that utilizes a more comprehensive range of amino acids can still produce contrast when assembled into protein units expressed in complex living environments.

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

Cited by 25 publications

References 72 publications

Chemical Exchange Saturation Transfer MRI for Differentiating Radiation Necrosis From Tumor Progression in Brain Metastasis—Application in a Clinical Setting

Chemical Exchange Saturation Transfer MRI for Differentiating Radiation Necrosis From Tumor Progression in Brain Metastasis—Application in a Clinical Setting

Label-Free Chemically and Molecularly Selective Magnetic Resonance Imaging

Development of a Synthetic Biosensor for Chemical Exchange MRI UtilizingIn SilicoOptimized Peptides

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