Evaluation of partial k-space strategies to speed up time-domain EPR imaging

Subramanian, S.; Chandramouli, Gadisetti V.R.; McMillan, A.; Gullapalli, Rao P.; Devasahayam, Nallathamby; Mitchell, James B.; Matsumoto, Shingo; Krishna, Murali C.

doi:10.1002/mrm.24508

Cited by 10 publications

(8 citation statements)

References 31 publications

(86 reference statements)

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“…The final image is obtained by a three dimensional Fourier transformation of these pseudo-echos. More sophisticated methods for k-space sampling were described elsewhere [21]. These can reduce the acquisition burden imposed by the necessity to acquire the number of time traces equal to the number of voxels in the resulting image.…”

Section: Pulse Sequences and Imaging Methodsmentioning

confidence: 99%

Comparison of pulse sequences for R1-based electron paramagnetic resonance oxygen imaging

Epel

Halpern²

2015

Journal of Magnetic Resonance

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Electron paramagnetic resonance (EPR) spin-lattice relaxation (SLR) oxygen imaging has proven to be an indispensable tool for assessing oxygen partial pressure in live animals. EPR oxygen images show remarkable oxygen accuracy when combined with high precision and spatial resolution. Developing more effective means for obtaining SLR rates is of great practical, biological and medical importance. In this work we compared different pulse EPR imaging protocols and pulse sequences to establish advantages and areas of applicability for each method. Tests were performed using phantoms containing spin probes with oxygen concentrations relevant to in vivo oxymetry. We have found that for small animal size objects the inversion recovery sequence combined with the filtered backprojection reconstruction method delivers the best accuracy and precision. For large animals, in which large radio frequency energy deposition might be critical, free induction decay and three pulse stimulated echo sequences might find better practical usage.

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Section: Pulse Sequences and Imaging Methodsmentioning

confidence: 99%

Comparison of pulse sequences for R1-based electron paramagnetic resonance oxygen imaging

Epel

Halpern²

2015

Journal of Magnetic Resonance

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“…The details of the EPRI system are found in previous publications [15,17,24]. Briefly, the home built spectrometer operates at 300 MHz.…”

Section: Experiments and Methodsmentioning

confidence: 99%

Accelerated electron paramagnetic resonance imaging using partial Fourier compressed sensing reconstruction

Chou

Chandramouli²,

Shin

et al. 2017

Magnetic Resonance Imaging

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Purpose Electron paramagnetic resonance (EPR) imaging has evolved as a promising tool to provide non-invasive assessment of tissue oxygenation levels. Due to the extremely short T2 relaxation time of electrons, single point imaging (SPI) is used in EPRI, limiting achievable spatial and temporal resolution. This presents a problem when attempting to measure changes in hypoxic state. In order to capture oxygen variation in hypoxic tissues and localize cycling hypoxia regions, an accelerated EPRI imaging method with minimal loss of information is needed. Methods We present an image acceleration technique, partial Fourier compressed sensing (PFCS), that combines compressed sensing (CS) and partial Fourier reconstruction. PFCS augments the original CS equation using conjugate symmetry information for missing measurements. To further improve image quality in order to reconstruct low-resolution EPRI images, a projection onto convex sets (POCS)-based phase map and a spherical-sampling mask are used in the reconstruction process. The PFCS technique was used in phantoms and in vivo SCC7 tumor mice to evaluate image quality and accuracy in estimating O2 concentration. Results In both phantom and in vivo experiments, PFCS demonstrated the ability to reconstruct images more accurately with at least a 4-fold acceleration compared to traditional CS. Meanwhile, PFCS is able to better preserve the distinct spatial pattern in a phantom with a spatial resolution of 0.6 mm. On phantoms containing Oxo63 solution with different oxygen concentrations, PFCS reconstructed linewidth maps that were discriminative of different O2 concentrations. Moreover, PFCS reconstruction of partially sampled data provided a better discrimination of hypoxic and oxygenated regions in a leg tumor compared to traditional CS reconstructed images. Conclusions EPR images with an acceleration factor of four are feasible using PFCS with reasonable assessment of tissue oxygenation. The technique can greatly enhance EPR applications and improve our understanding cycling hypoxia. Moreover this technique can be easily extended to various MRI applications.

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“…The trajectory used herein uses conjugate symmetry and randomized sampling. Owing to pure phase encoding and low B 0 field (10 mT), image phase in SP-EPRI is more tractable than in MRI (12). The reconstructed images in Figure 1 show a high degree of conjugate symmetry is possible in SP-EPRI.…”

Section: K-space Sampling Strategymentioning

confidence: 99%

“…Although this method improves temporal resolution (by a factor of 3) by eliminating the need of multiple data acquisitions (7) required to secure multiple images with same FOV, further reduction in acquisition time is needed for singlepoint imaging. In MRI, a myriad of techniques have been proposed to accelerate imaging, such as parallel imaging (8)(9)(10), partial Fourier reconstruction (11) [also applied to SP-EPRI (12)], and compressed sensing reconstruction (13). Among them, compressed sensing has recently surfaced as a promising method that can accelerate image acquisition by enabling high ratio of undersampling without a loss of image quality.…”

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confidence: 99%

Accelerated 4D quantitative single point EPR imaging using model‐based reconstruction

Jang

Matsumoto

Devasahayam

et al. 2014

Magnetic Resonance in Med

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Purpose EPRI has surfaced as a promising non-invasive imaging modality that is capable of imaging tissue oxygenation. Due to extremely short spin-spin relaxation time, EPRI benefits from single point imaging and inherently suffers from limited spatial and temporal resolution, preventing localization of small hypoxic tissues and differentiation of hypoxia dynamics, making accelerated imaging a crucial issue. Method In this study, methods for accelerated single point imaging were developed by combining a bilateral k-space extrapolation technique with model-based reconstruction that benefits from dense sampling in the parameter domain (measurement of the T2* decay of an FID). In bilateral k-space extrapolation, more k-space samples are obtained in a sparsely sampled region by bilaterally extrapolating data from temporally neighboring k-spaces. To improve the accuracy of T2* estimation, a principal component analysis (PCA)-based method was implemented. Result In a computer simulation and a phantom experiment, the proposed methods showed its capability for reliable T2* estimation with high acceleration (8-fold, 15-fold, and 30-fold accelerations for 61×61×61, 95×95×95, and 127×127×127 matrix, respectively). Conclusion By applying bilateral k-space extrapolation and model-based reconstruction, improved scan times with higher spatial resolution can be achieved in the current SP-EPRI modality.

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Evaluation of partial k-space strategies to speed up time-domain EPR imaging

Cited by 10 publications

References 31 publications

Comparison of pulse sequences for R1-based electron paramagnetic resonance oxygen imaging

Comparison of pulse sequences for R1-based electron paramagnetic resonance oxygen imaging

Accelerated electron paramagnetic resonance imaging using partial Fourier compressed sensing reconstruction

Accelerated 4D quantitative single point EPR imaging using model‐based reconstruction

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