Robust motion correction in <scp>CEST</scp> imaging exploiting low‐rank approximation of the z‐spectrum

Wech, Tobias; Köstler, Herbert

doi:10.1002/mrm.27206

Cited by 18 publications

(34 citation statements)

References 22 publications

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“…40 Low-rank approximations of Z-spectra have been used to improve SNR in hyper-CEST images, 41 as well as for iterative motion correction of creatine CEST spectra in skeletal muscle. 42 However, in both applications, few spectral peaks are present compared with the feature-rich in vivo Z-spectra acquired in CEST experiments with low saturation powers.…”

Section: Introductionmentioning

confidence: 99%

Adaptive denoising for chemical exchange saturation transfer MR imaging

et al. 2019

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High image signal–to–noise ratio (SNR) is required to reliably detect the inherently small chemical exchange saturation transfer (CEST) effects in vivo. In this study, it was demonstrated that identifying spectral redundancies of CEST data by principal component analysis (PCA) in combination with an appropriate data–driven extraction of relevant information can be used for an effective and robust denoising of CEST spectra. The relationship between the number of relevant principal components and SNR was studied on fitted in vivo Z–spectra with artificially introduced noise. Three different data–driven criteria to automatically determine the optimal number of necessary components were investigated. In addition, these criteria facilitate straightforward assessment of data quality that could provide guidance for CEST MR protocols in terms of SNR. Insights were applied to achieve a robust denoising of highly sampled low power Z–spectra of the human brain at 3 and 7 T. The median criterion provided the best estimation for the optimal number of components consistently for all three investigated artificial noise levels. Application of the denoising technique to in vivo data revealed a considerable increase in image quality for the amide and rNOE contrast with a considerable SNR gain. At 7 T the denoising capability was quantified to be comparable or even superior to an averaging of six measurements. The proposed denoising algorithm enables an efficient and robust denoising of CEST data by combining PCA with appropriate data–driven truncation criteria. With this generally applicable technique at hand, small CEST effects can be reliably detected without the need for repeated measurements.

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Section: Introductionmentioning

confidence: 99%

Adaptive denoising for chemical exchange saturation transfer MR imaging

et al. 2019

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“…SVD and principal component analysis methods utilize the spectral correlation between all voxels throughout the entire image to reduce noise levels. [36][37][38][39][40] Compared to SVD and principal component analysis methods, MLSVD CEST can exploit the additional spectral correlation between all the rows and columns of the CEST images and hence yield better noise reduction performance, as demonstrated in Figures 2 and 3. MLSVD and SVD retain optimal performance when the noise distribution in complex k-space is Gaussian.…”

Section: Discussionmentioning

confidence: 99%

High‐sensitivity CEST mapping using a spatiotemporal correlation‐enhanced method

Chen

Cao

Koehler

et al. 2020

Magnetic Resonance in Med

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Purpose To obtain high‐sensitivity CEST maps by exploiting the spatiotemporal correlation between CEST images. Methods A postprocessing method accomplished by multilinear singular value decomposition (MLSVD) was used to enhance the CEST SNR by exploiting the correlation between the Z‐spectrum for each voxel and the low‐rank property of the overall CEST data. The performance of this method was evaluated using CrCEST in ischemic mouse brain at 11.7 tesla. Then, MLSVD CEST was applied to obtain Cr, amide, and amine CEST maps of the ischemic mouse brain to demonstrate its general applications. Results Complex‐valued Gaussian noise was added to CEST k‐space data to mimic a low SNR situation. MLSVD CEST analysis was able to suppress the noise, recover the degraded CEST peak, and provide better CrCEST quality compared to the smoothing and singular value decomposition (SVD)‐based denoising methods. High‐resolution Cr, amide, and amine CEST maps of an ischemic stroke using MLSVD CEST suggest that CrCEST is also a sensitive pH mapping method, and a wide range of pH changes can be detected by combing CrCEST with amine CEST at high magnetic fields. Conclusion MLSVD CEST provides a simple and efficient way to improve the SNR of CEST images.

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“…No antispasmodic drug was given as part of this research and bowel motion may affect the results. Motion correction of CEST data can be difficult due to changes in image contrast between saturation frequencies; however, methods currently being developed to address this could be applied in future work …”

Section: Discussionmentioning

confidence: 99%

“…Motion correction of CEST data can be difficult due to changes in image contrast between saturation frequencies; however, methods currently being developed to address this could be applied in future work. 36 To prevent overfitting, the number of free parameters cannot be too high. For this reason, in this work we used a four-pool model with a single CEST pool and a single NOE pool.…”

Section: Discussionmentioning

confidence: 99%

Optimization and repeatability of multipool chemical exchange saturation transfer MRI of the prostate at 3.0 T

Evans

Torrealdea

Rega

et al. 2019

Magnetic Resonance Imaging

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Background Chemical exchange saturation transfer (CEST) can potentially support cancer imaging with metabolically derived information. Multiparametric prostate MRI has improved diagnosis but may benefit from additional information to reduce the need for biopsies. Purpose To optimize an acquisition and postprocessing protocol for 3.0 T multipool CEST analysis of prostate data and evaluate the repeatability of the technique. Study Type Prospective. Subjects Five healthy volunteers (age range: 24–47 years; median age: 28 years) underwent two sessions (interval range: 7–27 days; median interval: 20 days) and two biopsy‐proven prostate cancer patients were evaluated once. Patient 1 (71 years) had a Gleason 3 + 4 transition zone (TZ) tumor and patient 2 (55 years) had a Gleason 4 + 3 peripheral zone (PZ) tumor. Field Strength 3.0 T. Sequences run: T2‐weighted turbo‐spin‐echo (TSE); diffusion‐weighted imaging; CEST; WASABI (for B0 determination). Assessment Saturation, readout, and fit‐model parameters were optimized to maximize in vivo amide and nuclear Overhauser effect (NOE) signals. Repeatability (intrasession and intersession) was evaluated in healthy volunteers. Subsequently, preliminary evaluation of signal differences was made in patients. Regions of interest were drawn by two post‐FRCR board‐certified readers, both with over 5 years of experience in multiparametric prostate MRI. Statistical Tests Repeatability was assessed using Bland–Altman analysis, coefficient of variation (CV), and 95% limits of agreement (LOA). Statistical significance of CEST contrast was calculated using a nonparametric Mann–Whitney U‐test. Results The optimized saturation scheme was found to be 60 sinc‐Gaussian pulses with 40 msec pulse duration, at 50% duty‐cycle with continuous‐wave pulse equivalent B1 power (B1CWPE) of 0.92 μT. The magnetization transfer (MT) contribution to the fit‐model was centered at –1.27 ppm. Intersession coefficients of variation (CVs) of the amide, NOE, and magnetization transfer (MT) and asymmetric magnetization transfer ratio (MTRasym) signals of 25%, 23%, 18%, and 200%, respectively, were observed. Fit‐metric and MTRasym CVs agreed between readers to within 4 and 10 percentage points, respectively. Data Conclusion Signal differences of 0.03–0.10 (17–43%) detectable depending upon pool, with MT the most repeatable (signal difference of 17–22% detectable). Level of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:1238–1250.

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Robust motion correction in CEST imaging exploiting low‐rank approximation of the z‐spectrum

Abstract: The newly introduced method allows for a robust registration of CEST image series, which are corrupted by rigid and nonrigid motion of the investigated organ. The technique therefore improves the diagnostic value in various applications of CEST.

Cited by 18 publications

References 22 publications

Adaptive denoising for chemical exchange saturation transfer MR imaging

Adaptive denoising for chemical exchange saturation transfer MR imaging

High‐sensitivity CEST mapping using a spatiotemporal correlation‐enhanced method

Optimization and repeatability of multipool chemical exchange saturation transfer MRI of the prostate at 3.0 T

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