Optimization of magnetic flux density for fast MREIT conductivity imaging using multi-echo interleaved partial fourier acquisitions

BioMedical Engineering OnLine

Eung Je Woo²  Oh In Kwon¹  Hyung Joong Kim²  Woo Chul Jeong²  Munish Chauhan² 

[1]Department of Mathematics, Konkuk University, Seoul, Korea

[2]Department of Biomedical Engineering, Kyung Hee University, Yongin, Korea

关键词: Current density;    Magnetic flux density;    Interleaved partial fourier acquisition;    MRI;    MREIT;   

Others  :  797397
DOI  :  10.1186/1475-925X-12-82

 received in 2013-06-19, accepted in 2013-08-21,  发布年份 2013

【 摘 要 】

Background

Magnetic resonance electrical impedance tomography (MREIT) has been introduced as a non-invasive method for visualizing the internal conductivity and/or current density of an electrically conductive object by externally injected currents. The injected current through a pair of surface electrodes induces a magnetic flux density distribution inside the imaging object, which results in additional magnetic flux density. To measure the magnetic flux density signal in MREIT, the phase difference approach in an interleaved encoding scheme cancels out the systematic artifacts accumulated in phase signals and also reduces the random noise effect by doubling the measured magnetic flux density signal. For practical applications of in vivo MREIT, it is essential to reduce the scan duration maintaining spatial-resolution and sufficient contrast. In this paper, we optimize the magnetic flux density by using a fast gradient multi-echo MR pulse sequence. To recover the one component of magnetic flux density B_z, we use a coupled partial Fourier acquisitions in the interleaved sense.

Methods

To prove the proposed algorithm, we performed numerical simulations using a two-dimensional finite-element model. For a real experiment, we designed a phantom filled with a calibrated saline solution and located a rubber balloon inside the phantom. The rubber balloon was inflated by injecting the same saline solution during the MREIT imaging. We used the multi-echo fast low angle shot (FLASH) MR pulse sequence for MRI scan, which allows the reduction of measuring time without a substantial loss in image quality.

Results

Under the assumption of a priori phase artifact map from a reference scan, we rigorously investigated the convergence ratio of the proposed method, which was closely related with the number of measured phase encode set and the frequency range of the background field inhomogeneity. In the phantom experiment with a partial Fourier acquisition, the total scan time was less than 6 seconds to measure the magnetic flux density B_z data with 128×128 spacial matrix size, where it required 10.24 seconds to fill the complete k-space region.

Conclusion

Numerical simulation and experimental results demonstrated that the proposed method reduces the scanning time and provides the recovered B_z data comparable to what we obtained by measuring complete k-space data.

【 授权许可】

   
2013 Chauhan et al.; licensee BioMed Central Ltd.

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