利用动态接收增益提高磁共振成像信噪比的方法
收稿日期: 2014-04-16
修回日期: 2014-11-04
网络出版日期: 2014-12-05
基金资助
国家科技重大专项资助项目(2011ZX05008-004).
Improving Signal-to-Noise Ratio in Magnetic Resonance Imaging Using Dynamic Receiver Gain
Received date: 2014-04-16
Revised date: 2014-11-04
Online published: 2014-12-05
Supported by
国家科技重大专项资助项目(2011ZX05008-004).
提出了一种提高磁共振成像(MRI)信噪比的有效方法．该方法在每次采集回波信号前，能够快速、灵活地控制MRI 接收机的增益，实现磁共振信号动态范围的压缩；在图像重建之前采用双精度浮点运算扩展动态范围压缩的磁共振信号，最终得到信噪比提高的重建图像．在1.5 T 超导MRI 系统上进行了自旋回波序列的水模成像，实验结果表明，相比传统的基于固定接收增益的扫描图像，利用该方法得到的T1 加权图像信噪比可以提高10%．和其他提高磁共振信号动态范围的方法相比，该方法无需增加额外硬件电路，避免多次采集图像，因而具有实现成本低的优点，是一种提高MRI 信噪比的有效方法．
关键词： 磁共振成像(MRI); 动态接收增益; 量化噪声; 动态范围; 信噪比
孙宏宇1 , 汤伟男2 , 王为民1* . 利用动态接收增益提高磁共振成像信噪比的方法[J]. 波谱学杂志, 2014 , 31(4) : 515 -522 . DOI: 10.11938/cjmr20140406
A method to increase signal-to-noise ratio (SNR) in magnetic resonance imaging using dynamic receiver gain was proposed. In the method, the receiver gain was adjusted dynamically according to amplitude of each echo signal before acquisition. By doing so, the receiver dynamic range could be optimized to improve SNR of each acquisition. To reconstruct the images, a double-precision floating-point arithmetic processing procedure was used to expand the dynamic range of all acquisitions to the same scale. Imaging experiments were conducted using the proposed method on a 1.5 T clinical MRI scanner.
The results showed that the SNR of T1-weighted images could be improved by approximately 10%, compared to the fixed-receiver-gain images. More importantly, the method proposed needs no extra circuits or multiple time-consuming scans. It is concluded that using dynamic receiver gain for each acquisition is an effective way to improve SNR in MR imaging, especially for high-resolution and high-filed imaging applications.
Key words： MRI; dynamic receiver gain; quantization noise; dynamic range; signal-tonoise ratio
[1] Oh C H, Ryu Y C, Hyun J H, et al. Dynamic range expansion of receiver by using optimized gain adjustment for high-field MRI[J]. Concept Magn Reson A, 2010, 36A: 243－254.
[2] Elliott M A, Insko E K, Greenman R L, et al. Improved resolution and signal-to-noise ratio in MRI via enhanced signal digitization[J]. J Magn Reson, 1997, 130: 300－304.
[3] Maudsley A A. Dynamic range improvement in NMR imaging using phase scrambling[J]. J Magn Reson, 1987, 76: 287－305.
[4] Wedeen V J, Chao Y, Ackerman J L, et al. Dynamic range compression in MRI by means of nonlinear gradient pulse[J]. Magn Reson Med, 1988, 6: 287－295.
[5] Oh C H, Hilal S K, Wu E X, et al. Phase-scrambled RF excitation for 3D volume-selective multislice NMR imaging[J]. Magn Reson Med, 1992, 28: 290－299.
[6] Johnson G, Wu E X, Hilal S K, et al. Optimized phase scrambling for RF phase encoding[J]. J Magn Reson B, 1994, 103: 59－63.
[7] Maudsley A A. Sensitivity in fourier imaging[J]. J Magn Reson, 1986, 68: 363－366.
[8] Behin R, Bishop J, Henkelman R M, et al. Dynamic range requirements for MRI[J]. Concept Magn Reson B, 2005, 26B: 28－35.
[9] Otake Y, Kose K, Haishi T, et al. A solution to the dynamic range problem in MRI using a parallel imaging acquisition[J]. Concept Magn Reson B, 2006, 29B: 161－167.
[10] Takeda K, Takegoshi K. Noise reduction by dynamic signal preemphasis[J]. J Magn Reson, 2011, 208: 305－308.
[11] Ning R, Dai Y, Yang G, et al. A digital receiver with fast frequency- and gain-switching capabilities for MRI systems[J]. Magn Reson Mater Phy, 2009, 22: 333－342.
[12] Bollenbeck J, Vester M, Oppelt R, et al. ISMRM Annual Meeting[C]. Miami: The International Society for Magnetic Resonance in Medicine, 2005.
[13] Delsuc M A, Lallemand J Y. Improvement of dynamic range in NMR by oversampling[J]. J Magn Reson, 1986, 69: 504－507.
[14] Li Rui(李睿), Xiao Liang(肖亮), Wang Wei-min(王为民), et al. The design of a digital receiver system for MRI scanners(磁共振成像信号的数字化接收系统设计)[J]. Chinese J Magn Reson(波谱学杂志), 2009, 26(3): 359－368.
[15] Xiao Liang(肖亮), Tang Wei-nan(汤伟男), Wang Wei-min(王为民), et al. An FPGA-based single-chip gradient control module for magnetic resonance imaging(基于单片FPGA 的磁共振成像梯度计算模块)[J]. Chinese J Magn Reson(波谱学杂志), 2010, 27(2): 163－171.
[16] Wang Hong(王洪), Sun Hong-yu(孙宏宇), Tang Wei-nan(汤伟男), et al. An FPGA-based multi-channel receiver module for magnetic resonance imaging (基于单片FPGA 的多通道磁共振成像接收模块)[J]. Chinese J Magn Reson(波谱学杂志), 2012, 29(2): 239－247.
[17] Wang Hong(王洪), Xiong Ze-chong(熊泽冲), Lin Xian-chai(林先钗), et al. A computer-on-module based highperformance control interface with gigabit ethernet for magnetic resonance imaging spectrometer(基于模块计算机的千兆网磁共振谱仪控制接口)[J]. Chinese J Magn Reson(波谱学杂志), 2012, 29(4): 499－507.
[18] Fuderer M. The information content of MR images[J]. IEEE T Med Imaging, 1988, 7: 368－380.
[19] Watts R, Wang Y. k-space interpretation of the Rose model: noise limitation on the detectable resolution in MRI[J]. Magn Reson Med, 2002, 48: 550－554.
[20] Bennett W R. Spectra of quantized signals[J]. Bell System Technical J, 1948, 27: 446－471.
[21] McCann A J, Workman A, McGrath C, et al. A quick and robust method for measurement of signal-to-noise ratio in MRI[J]. Phys Med Biol, 2013, 58: 3 775－3 790.
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