Noise Analysis of MREIT at 3T and 11T Field Strength

Sadleir, Rosalind; Grant, Samuel C.; Zhang, S.U.; Oh, Seogil; Lee, B.I.; Pyo, Hyun Chan; Park, C.J.; Woo, Eun Jin; Lee, S.Y.; Seo, Jin Keun; Kwon, Oh In

doi:10.1109/iembs.2005.1617011

Cited by 7 publications

(15 citation statements)

References 11 publications

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“…11 This fact was experimentally verified for the phantom experiment. The histograms of background for real and imaginary images in a slice are shown in Figs.…”

Section: Distribution Of Noisementioning

confidence: 59%

“…The standard deviation of this noise can be extracted from the background. 11,18 Therefore, if we assume that for each pixel inside the subject X R is the random variable representing the corrupted intensity in real images and X I is the random variable representing the corrupted intensity in imaginary images, we have for one pixel…”

Section: Distribution Of Noisementioning

confidence: 99%

“…The images can become very noisy and unusable if acquisition parameters are not chosen appropriately, the energy of the injected current pulse is not enough, or the size of the studied subject is very small. The noise and its effect on the current density images are studied in the literature in two main works by Scott et al 10 and Sadlier et al 11 The former studied the effect of MRI acquisition parameters like echo time (TE), injected current pulse width (Tc), and current amplitude on the noise level in the images. The latter used the fact that the noise distribution in real and imaginary images is zero mean Gaussian.…”

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confidence: 99%

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Noise distribution and denoising of current density images

et al. 2015

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Abstract. Current density imaging (CDI) is a magnetic resonance (MR) imaging technique that could be used to study current pathways inside the tissue. The current distribution is measured indirectly as phase changes. The inherent noise in the MR imaging technique degrades the accuracy of phase measurements leading to imprecise current variations. The outcome can be affected significantly, especially at a low signal-to-noise ratio (SNR). We have shown the residual noise distribution of the phase to be Gaussian-like and the noise in CDI images approximated as a Gaussian. This finding matches experimental results. We further investigated this finding by performing comparative analysis with denoising techniques, using two CDI datasets with two different currents (20 and 45 mA). We found that the block-matching and three-dimensional (BM3D) technique outperforms other techniques when applied on current density (J). The minimum gain in noise power by BM3D applied to J compared with the next best technique in the analysis was found to be around 2 dB per pixel. We characterize the noise profile in CDI images and provide insights on the performance of different denoising techniques when applied at two different stages of current density reconstruction.

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“…11 This fact was experimentally verified for the phantom experiment. The histograms of background for real and imaginary images in a slice are shown in Figs.…”

Section: Distribution Of Noisementioning

confidence: 59%

Section: Distribution Of Noisementioning

confidence: 99%

mentioning

confidence: 99%

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Noise distribution and denoising of current density images

et al. 2015

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“…The strength of the B z signal is directly proportional to the amplitude of the injection current. Noise analyses showed that the noise level in B z data is inversely proportional to the product of the signal‐to‐noise ratio (SNR) of the MR magnitude image Ψ and the total current injection time Δ T (4, 13). We should increase the product ΨΔ T to be able to reduce the imaging current without deteriorating the quality of B z images.…”

Section: Introductionmentioning

confidence: 99%

Experimental performance evaluation of multi‐echo ICNE pulse sequence in magnetic resonance electrical impedance tomography

Minhas¹,

Jeong²,

Kim³

et al. 2011

Magnetic Resonance in Med

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Latest experimental results in magnetic resonance electrical impedance tomography (MREIT) demonstrated high-resolution in vivo conductivity imaging of animal and human subjects using imaging currents of 5 to 9 mA. Externally injected imaging currents induce magnetic flux density distributions, which are affected by a conductivity distribution. Since we extract the induced magnetic flux density images from MR phase images, it is essential to reduce noise in the phase images. In vivo human and disease model animal experiments require reduction of imaging current amplitudes and scan times. In this article, we investigate a multi-echo based MREIT pulse sequence where we utilize a remaining time after the first echo within one TR to obtain more echo signals. It also allows us to prolong the total current injection time. From phantom and animal imaging experiments, we found that this method significantly reduces the noise level in measured magnetic flux density images. We describe experimental validation of the multi-echo sequence by comparing its performance with a single-echo method using 3 mA imaging currents. The proposed method will be advantageous for an imaging region with long T2 values such as the brain and knee. Depending on T2 values, we suggest using two or three echoes in future experimental studies. Magn Reson Med 66:957-965, 2011. V C 2011 Wiley-Liss, Inc.

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“…As the first step toward these goals, Sadleir et al (2005a) examined noise levels in measured magnetic flux density using two MREIT systems at 3 and 11 T field strengths. They found that typical noise levels were about 0.25 and 0.05 nT at 3 and 11 T, respectively, at a voxel size of 3 × 3 × 3 mm 3 .…”

Section: Introductionmentioning

confidence: 99%

High field MREIT: setup and tissue phantom imaging at 11 T

et al. 2006

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Magnetic resonance electrical impedance tomography (MREIT) has the potential to provide conductivity and current density images with high spatial resolution and accuracy. Recent experimental studies at a field strength of 3 T showed that the spatial resolution of conductivity and current density images may be similar to that of conventional MR images as long as enough current is injected, at least 20 mA when the object being imaged has a size similar to the human head. To apply the MREIT technique to image small conductivity changes using less injection current, we performed MREIT studies at 11 T field strength, where noise levels in measured magnetic flux density data are significantly lower. In this paper we present the experimental results of imaging biological tissues with different conductivity values using MREIT at 11 T. We describe technical difficulties encountered in using high-field MREIT systems and possible solutions. High-field MREIT is suggested as a research tool for obtaining accurate conductivity data from tissue samples and animal subjects.

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Noise Analysis of MREIT at 3T and 11T Field Strength

Cited by 7 publications

References 11 publications

Noise distribution and denoising of current density images

Noise distribution and denoising of current density images

Experimental performance evaluation of multi‐echo ICNE pulse sequence in magnetic resonance electrical impedance tomography

High field MREIT: setup and tissue phantom imaging at 11 T

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