Towards the complex dependence of MTRasym on T1w in amide proton transfer (APT) imaging

Zu, Zhongliang

doi:10.1002/nbm.3934

Cited by 61 publications

(77 citation statements)

References 47 publications

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“…For the next step, this acquisition protocol will be used to comprehensively assess the actual clinical relevance of relaxation compensation in CEST‐MRI for various neuro‐oncological clinical questions. In particular, the translation to 3 T enables investigation of the controversially discussed overcompensation of T 1 at this magnetic field strength using the AREX approach (Equation ) . The unravelling of the different CEST signals and compensation for competing relaxation effects by the presented acquisition protocol can also enable obtaining more detailed information on the origin of CEST contrast in vivo.…”

Section: Discussionmentioning

confidence: 99%

Relaxation‐compensated APT and rNOE CEST‐MRI of human brain tumors at 3 T

Goerke

Soehngen

Deshmane

et al. 2019

Magnetic Resonance in Med

111

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Purpose Relaxation‐compensated CEST‐MRI (i.e., the inverse metrics magnetization transfer ratio and apparent exchange‐dependent relaxation) has already been shown to provide valuable information for brain tumor diagnosis at ultrahigh magnetic field strengths. This study aims at translating the established acquisition protocol at 7 T to a clinically relevant magnetic field strength of 3 T. Methods Protein model solutions were analyzed at multiple magnetic field strengths to assess the spectral widths of the amide proton transfer and relayed nuclear Overhauser effect (rNOE) signals at 3 T. This prior knowledge of the spectral range of CEST signals enabled a reliable and stable Lorentzian‐fitting also at 3 T where distinct peaks are no longer resolved in the Z‐spectrum. In comparison to the established acquisition protocol at 7 T, also the image readout was extended to three dimensions. Results The observed spectral range of CEST signals at 3 T was approximately ±15 ppm. Final relaxation‐compensated amide proton transfer and relayed nuclear Overhauser effect contrasts were in line with previous results at 7 T. Examination of a patient with glioblastoma demonstrated the applicability of this acquisition protocol in a clinical setting. Conclusion The presented acquisition protocol allows relaxation‐compensated CEST‐MRI at 3 T with a 3D coverage of the human brain. Translation to a clinically relevant magnetic field strength of 3 T opens the door to trials with a large number of participants, thus enabling a comprehensive assessment of the clinical relevance of relaxation compensation in CEST‐MRI.

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Section: Discussionmentioning

confidence: 99%

Relaxation‐compensated APT and rNOE CEST‐MRI of human brain tumors at 3 T

Goerke

Soehngen

Deshmane

et al. 2019

Magnetic Resonance in Med

111

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“…This study utilized a saturation power of 1.5 μT, which has proved to be capable of maintaining the dominant contribution of the APT effect in MTR asym analysis and generating good contrast between tumor and normal‐appearing brain tissues . In addition, a recent simulation study has demonstrated the insensitive MTR asym to T 1w at the saturation powers of 1–3 μT at 3T, due to a comparable T 1 recovery effect and T 1w ‐related saturation effect . Therefore, T 1w normalized APTw was not necessary under the current imaging settings.…”

Section: Discussionmentioning

confidence: 99%

Diagnostic performance of multiparametric MRI in the evaluation of treatment response in glioma patients at 3T

Liu

Chen

et al. 2019

Magnetic Resonance Imaging

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Background MRI is one of the most important techniques to assess the treatment response of gliomas. However, differentiating tumor recurrence (TuR) from treatment effects (TrE) remains challenging. Purpose To compare the diagnostic performance of MR diffusion‐weighted imaging (DWI), arterial spin labeling (ASL), proton MR spectroscopy (MRS), and amide proton transfer (APT) imaging in differentiating between TuR and TrE in posttreatment glioma patients. Study Type Prospective. Population Thirty patients with suspected tumor progression. Field Strength/Sequence DWI, ASL, proton MRS, and APT imaging were performed at 3T MR. Assessment MR indices, including ADC, relative cerebral blood flow (rCBF), ratios of Cho/Cr, Cho/NAA, and NAA/Cr and APT‐weighted (APTw) effect were obtained from DWI, ASL, proton MRS, and APT imaging, respectively. Indices were measured in the contralateral normal‐appearing white matter and lesions defined on the Gd‐enhanced T1w image. TuR or TrE was either determined histologically or clinically from longitudinal MRI follow‐up for at least 6 months. Statistical Tests The diagnostic performance of the indices was evaluated using Student's t‐test, receiver operating characteristic (ROC) curve, and multivariate logistic regression analyses. Results Among the 30 patients, 16 were diagnosed as having TuR and the rest having TrE. The recurrent tumors showed a significantly higher APTw effect (1.56 ± 1.14%) and rCBF (1.44 ± 0.61) compared with lesions representing treatment effects (–0.44 ± 1.34% and 0.72 ± 0.25, respectively, with P < 0.001). The areas under the curve (AUCs) were 0.87 and 0.90 for APTw and rCBF, respectively, in differentiating between TuR and TrE. Combining APTw and rCBF achieved a higher AUC of 0.93. MRS index ratios of Cho/Cr (P = 0.25), Cho/NAA (P = 0.16), and NAA/Cr (P = 0.86) and ADC (P = 0.37) showed no significant differences between TuR and TrE lesions, with AUCs lower than 0.70. Data Conclusion Compared with DWI and MRS, ASL and APT imaging techniques showed better diagnostic capability in distinguishing TuR from TrE. Level of Evidence: 1 Technical Efficacy: Stage 4 J. Magn. Reson. Imaging 2020;51:1154–1161.

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“…CEST contrast computation using the proposed Z‐spectra fitting using both models 1 and 2 mitigates the MT effect and is less sensitive to T 1 ; however, complete removal of these effects from true CEST contrast has not been achieved to date. Another study reported that for nonsteady‐state acquisition, the effect of T 1 is substantially less. In this study, we have considered only two CEST pools and a single rNOE.…”

Section: Discussionmentioning

confidence: 99%

“…For simulation, the concentrations were taken from references , and exchange rate measured in vivo from rat brain . Three amine protons were considered for each glutamate molecule.…”

Section: Methodsmentioning

confidence: 99%

Evaluating the feasibility of creatine‐weighted CEST MRI in human brain at 7 T using a Z‐spectral fitting approach

et al. 2019

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The current study aims to evaluate the feasibility of creatine (Cr) chemical exchange saturation transfer (CEST)‐weighted MRI at 7 T in the human brain by optimizing the saturation pulse parameters and computing contrast using a Z‐spectral fitting approach. The Cr‐weighted (Cr‐w) CEST contrast was computed from phantoms data. Simulations were carried out to obtain the optimum saturation parameters for Cr‐w CEST with lower contribution from other brain metabolites. CEST‐w images were acquired from the brains of four human subjects at different saturation parameters. The Cr‐w CEST contrast was computed using both asymmetry analysis and Z‐spectra fitting approaches (models 1 and 2, respectively) based on Lorentzian functions. For broad magnetization transfer (MT) effect, Gaussian and Super‐Lorentzian line shapes were also evaluated. In the phantom study, the Cr‐w CEST contrast showed a linear dependence on concentration in physiological range and a nonlinear dependence on saturation parameters. The in vivo Cr‐w CEST map generated using asymmetry analysis from the brain represents mixed contrast with contribution from other metabolites as well and relayed nuclear Overhauser effect (rNOE). Simulations provided an estimate for the optimum range of saturation parameters to be used for acquiring brain CEST data. The optimum saturation parameters for Cr‐w CEST to be used for brain data were around B1rms = 1.45 μT and duration = 2 seconds. The Z‐spectral fitting approach enabled computation of individual components. This also resulted in mitigating the contribution from MT and rNOE to Cr‐w CEST contrast, which is a major source of underestimation in asymmetry analysis. The proposed modified z‐spectra fitting approach (model 2) is more stable to noise compared with model 1. Cr‐w CEST contrast obtained using fitting was 6.98 ± 0.31% in gray matter and 5.45 ± 0.16% in white matter. Optimal saturation parameters reduced the contribution from other CEST effects to Cr‐w CEST contrast, and the proposed Z‐spectral fitting approach enabled computation of individual components in Z‐spectra of the brain. Therefore, it is feasible to compute Cr‐w CEST contrast with a lower contribution from other CEST and rNOE.

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Towards the complex dependence of MTR_asym on T_1w in amide proton transfer (APT) imaging

Cited by 61 publications

References 47 publications

Relaxation‐compensated APT and rNOE CEST‐MRI of human brain tumors at 3 T

Relaxation‐compensated APT and rNOE CEST‐MRI of human brain tumors at 3 T

Diagnostic performance of multiparametric MRI in the evaluation of treatment response in glioma patients at 3T

Evaluating the feasibility of creatine‐weighted CEST MRI in human brain at 7 T using a Z‐spectral fitting approach

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