用于引导HIFU治疗的永磁开放式MRI系统研究
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摘要
目前,永磁开放式MRI在HIFU治疗中的应用仍处在发展阶段,在系统软、硬件和成像方法等方面还有许多技术问题急需解决。本论文对术前、术中和术后等阶段存在的一些技术问题进行了研究,主要内容如下：
1.具有快速增益切换功能的数字接收机
在HIFU治疗的术前诊断中,需要尽可能精确地对病灶进行定位和边界勾勒。这就需要获得高分辨的MRI诊断图像,而常规的数字接收机将会面临动态范围不足的问题。本文提出了增益快速切换方法来提高接收机的动态范围,并研制出具有快速增益切换功能的数字接收机。对比实验证明,该方法可以有效提高数字接收机的动态范围。
2.MRI的正交线圈数字合成方法为了对病灶进行精确定位和边界勾勒,需要高质量的MRI图像。永磁MRI的一个不足之处在于图像信噪比比较低。提高接收通道的灵敏度对解决这一问题是十分关键的。本文针对现有正交合成技术的不足,提出了正交线圈数字合成方法来提高永磁MRI图像信噪比,最后进行了实验验证。
3.梯度系统延时的校正
在HIFU术前诊断中,需要利用T2加权像对病灶进行精确定位和边界勾勒。获得T2加权像一般采用的FSE成像序列。FSE是一种比较成熟的成像序列,随着其自身的不断完善,一些仪器上的非理想因素逐渐成为影响FSE图像质量的关键。本文针对梯度系统延时对FSE成像的影响,提出了多通道独立延时触发方法来校正梯度延时的方法,并研制了具有多通道独立延时触发功能的脉冲序列发生器。最后对梯度延时校正效果进行了验证。
4.多层同步成像技术研究
在临床诊断中,特别是在肝脏病变的诊断中,T1加权像可以提供重要的诊断信息,因此被作为常规扫描之一。在HIFU治疗中,T1加权像不但可以提供术前诊断信息,还可用于术后对治疗效果进行评估。然而,在永磁MRI系统中进行T1加权成像需要较短的TR,这将导致在一个TR时间内扫描的层数受到限制。本文提出了采用多层同步成像技术来解决这一问题,并对现有的多层同步成像技术进行了必要的改进。论文介绍了多层同步成像的原理及实现方法,并给出计算机模拟和成像实验结果。
5.MRI在HIFU术中监控的应用研究
HIFU治疗过程中,医生需要根据靶点及其周围组织的温度来决定所施加的热剂量。本文在永磁MRI系统上,对质子共振频率测温方法进行了研究；并提出采用导航回波技术和动态匀场方法来克服永磁系统磁场长期、短期波动,以及磁场的空间分布随时间改变等问题。在永磁MRI系统上进行测温实验,实验结果表明,采用导航回波技术和动态匀场方法可以有效提高永磁MRI测温精度。
Magnetic resonance imaging (MRI) guided high intensity focused ultrasound (HIFU) treatment has attracted a lot of attention in recent years. However, there are still many key technical problems to be overcome before the MRI-guided HIFU becomes practical. The studies in this thesis will focus on MRI equipment building-up and imaging techniques for guidance of HIFU treatment. The MRI system is equipped with U-type permanent magnet to fulfill the requirements of guiding the HIFU treatments. To be specific, the following items will be covered:
1. A digital receiver with fast gain switching capability
Before HIFU treatment, high resolution MRI images are probably required for precise localization and outline of diseases. However, a typical MRI digital receiver cannot always meet the requirement of dynamic range in high resolution imaging due to ADC resolution restriction. In order to increase the dynamic range of the digital receiver, a method of fast gain switching is proposed, and a corresponding receiver unit is implemented. The effectiveness of the fast gain switching method and the performance of the proposed digital receiver are verified and demonstrated experimentally.
2. Digital Combination of signals from quadrature MRI receiver coils
In order to ensure sufficient accuracy of lesion localization, signal-to-noise ratio (SNR) of MRI images should be taken into account. An effective method of improving the SNR is using quadrature receiver coils (I-coil and Q-coil) to detect MRI signals. However, the sensitivity imbalance between I and Q receive channels will lead to unexpected quality degradation of final images. In order to address this imbalance problem, we propose a digital combination method to optimize SNR of final images, in which the weighting coefficients of I and Q channels are determined dynamically in K-space. It is demonstrated that the digital combination method is effective to enhance SNR of the final images acquired with quadrature MRI receiver coils.
3. Correction of gradient delay
Fast spin echo (FSE) imaging sequence is typically used to obtain T2-weighted MRI images, which is supposed to provide good contrast between tumor and normal tissues. Unfortunately the FSE sequence is rather susceptible to imperfections in equipment and configuration--gradient delay is one of them. In order to correct the effects of the gradient delay, a novel method is proposed, in which the gradient channels are always triggered earlier than the radio-frequency channels. An MRI pulse programmer providing this independent trigger delay is developed, and the correction of the gradient delay is experimentally demonstrated.
4. Simultaneous multi-slice imaging
T1-weighted MR images can provide important information in preoperative diagnosis and postoperative evaluation, especially for liver disease. Generally, in low-field MRI scanners, a shorter TR is used for T1-weighted imaging. As a result, the allowable slice number in one TR is limited. In this paper, simultaneous multi-slice imaging (SMI) method is utilized to overcome this difficulty. Theory and specific implementation details are described, and the results of computer simulation and MRI experiments are reported.
5. MRI monitoring techniques
During HIFU treatment, temperal temperature evaluation of disease and surrounding tissues is important. In this thesis, MR thermometry with proton resonance frequency is investigated on a low-field MRI scanner with U-type permanent magnet. Nevertheless, high openness of the U-type construction will cause the scanner to be severely sensitive to the variation of external electromagnetic field. Another challenge induced by the high openness is significant variation of Bo field distribution. In order to reduce or eliminate these effects on thermometry imaging, a series of corrections are treated, including navigator echo and dynamic shimming. Finally, a thermometry experiment is executed with these corrections, and the results are compared with those obtained without the corrections.
1.具有快速增益切换功能的数字接收机
在HIFU治疗的术前诊断中,需要尽可能精确地对病灶进行定位和边界勾勒。这就需要获得高分辨的MRI诊断图像,而常规的数字接收机将会面临动态范围不足的问题。本文提出了增益快速切换方法来提高接收机的动态范围,并研制出具有快速增益切换功能的数字接收机。对比实验证明,该方法可以有效提高数字接收机的动态范围。
2.MRI的正交线圈数字合成方法为了对病灶进行精确定位和边界勾勒,需要高质量的MRI图像。永磁MRI的一个不足之处在于图像信噪比比较低。提高接收通道的灵敏度对解决这一问题是十分关键的。本文针对现有正交合成技术的不足,提出了正交线圈数字合成方法来提高永磁MRI图像信噪比,最后进行了实验验证。
3.梯度系统延时的校正
在HIFU术前诊断中,需要利用T2加权像对病灶进行精确定位和边界勾勒。获得T2加权像一般采用的FSE成像序列。FSE是一种比较成熟的成像序列,随着其自身的不断完善,一些仪器上的非理想因素逐渐成为影响FSE图像质量的关键。本文针对梯度系统延时对FSE成像的影响,提出了多通道独立延时触发方法来校正梯度延时的方法,并研制了具有多通道独立延时触发功能的脉冲序列发生器。最后对梯度延时校正效果进行了验证。
4.多层同步成像技术研究
在临床诊断中,特别是在肝脏病变的诊断中,T1加权像可以提供重要的诊断信息,因此被作为常规扫描之一。在HIFU治疗中,T1加权像不但可以提供术前诊断信息,还可用于术后对治疗效果进行评估。然而,在永磁MRI系统中进行T1加权成像需要较短的TR,这将导致在一个TR时间内扫描的层数受到限制。本文提出了采用多层同步成像技术来解决这一问题,并对现有的多层同步成像技术进行了必要的改进。论文介绍了多层同步成像的原理及实现方法,并给出计算机模拟和成像实验结果。
5.MRI在HIFU术中监控的应用研究
HIFU治疗过程中,医生需要根据靶点及其周围组织的温度来决定所施加的热剂量。本文在永磁MRI系统上,对质子共振频率测温方法进行了研究；并提出采用导航回波技术和动态匀场方法来克服永磁系统磁场长期、短期波动,以及磁场的空间分布随时间改变等问题。在永磁MRI系统上进行测温实验,实验结果表明,采用导航回波技术和动态匀场方法可以有效提高永磁MRI测温精度。
Magnetic resonance imaging (MRI) guided high intensity focused ultrasound (HIFU) treatment has attracted a lot of attention in recent years. However, there are still many key technical problems to be overcome before the MRI-guided HIFU becomes practical. The studies in this thesis will focus on MRI equipment building-up and imaging techniques for guidance of HIFU treatment. The MRI system is equipped with U-type permanent magnet to fulfill the requirements of guiding the HIFU treatments. To be specific, the following items will be covered:
1. A digital receiver with fast gain switching capability
Before HIFU treatment, high resolution MRI images are probably required for precise localization and outline of diseases. However, a typical MRI digital receiver cannot always meet the requirement of dynamic range in high resolution imaging due to ADC resolution restriction. In order to increase the dynamic range of the digital receiver, a method of fast gain switching is proposed, and a corresponding receiver unit is implemented. The effectiveness of the fast gain switching method and the performance of the proposed digital receiver are verified and demonstrated experimentally.
2. Digital Combination of signals from quadrature MRI receiver coils
In order to ensure sufficient accuracy of lesion localization, signal-to-noise ratio (SNR) of MRI images should be taken into account. An effective method of improving the SNR is using quadrature receiver coils (I-coil and Q-coil) to detect MRI signals. However, the sensitivity imbalance between I and Q receive channels will lead to unexpected quality degradation of final images. In order to address this imbalance problem, we propose a digital combination method to optimize SNR of final images, in which the weighting coefficients of I and Q channels are determined dynamically in K-space. It is demonstrated that the digital combination method is effective to enhance SNR of the final images acquired with quadrature MRI receiver coils.
3. Correction of gradient delay
Fast spin echo (FSE) imaging sequence is typically used to obtain T2-weighted MRI images, which is supposed to provide good contrast between tumor and normal tissues. Unfortunately the FSE sequence is rather susceptible to imperfections in equipment and configuration--gradient delay is one of them. In order to correct the effects of the gradient delay, a novel method is proposed, in which the gradient channels are always triggered earlier than the radio-frequency channels. An MRI pulse programmer providing this independent trigger delay is developed, and the correction of the gradient delay is experimentally demonstrated.
4. Simultaneous multi-slice imaging
T1-weighted MR images can provide important information in preoperative diagnosis and postoperative evaluation, especially for liver disease. Generally, in low-field MRI scanners, a shorter TR is used for T1-weighted imaging. As a result, the allowable slice number in one TR is limited. In this paper, simultaneous multi-slice imaging (SMI) method is utilized to overcome this difficulty. Theory and specific implementation details are described, and the results of computer simulation and MRI experiments are reported.
5. MRI monitoring techniques
During HIFU treatment, temperal temperature evaluation of disease and surrounding tissues is important. In this thesis, MR thermometry with proton resonance frequency is investigated on a low-field MRI scanner with U-type permanent magnet. Nevertheless, high openness of the U-type construction will cause the scanner to be severely sensitive to the variation of external electromagnetic field. Another challenge induced by the high openness is significant variation of Bo field distribution. In order to reduce or eliminate these effects on thermometry imaging, a series of corrections are treated, including navigator echo and dynamic shimming. Finally, a thermometry experiment is executed with these corrections, and the results are compared with those obtained without the corrections.
引文
1. Frizzell L. Threshold dosages for damage to mammalian liver by high intensity focused ultrasound. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 1988,35:578-581.
2. ter Haar GR, Sinnett D and Rivens I. High intensity focused ultrasound-A surgical technique for the treatment of discrete liver tumors. Physics in Medicine and Biology, 1989,34:1743-1750.
3. Sibille A, Pra TF, Chapelon JY, Fadil FA, Henry L, Theillere Y, Poncho T and Cathignol D. Extracorporeal ablation of the liver tissue by high-intensity focused ultrasound. Oncology, 1993,50:375-379.
4. Cheng SQ, Zhou ZD, Tang ZY, Yu Y, Wang HZ, Bao SS and Qian DC. High-intensity focused ultrasound in the treatment of experimental liver tumour. Journal of Cancer Research and Clinical Oncology,1997,123:219-223.
5. Chaussy C and Thuroff S. The status of high-intensity focused ultrasound in the treatment of localized prostate cancer and the impact of a combined resection. Current Urology Reports,2003,4:248-252.
6. Leslie TA and Kennedy JE. High-intensity focused ultrasound principles, current uses, and potential for the future. Ultrasound Quarterly,2006,22(4):263-272.
7. Ahmed HU, Zacharakis E, Dudderidge T, Armitage JN, Scott R, Calleary J, Illing R, Kirkham A, Freeman A, Ogden C, Allen C and Emberton M. High-intensity-focused ultrasound in the treatment of primary prostate cancer: the first UK series. British Journal of Cancer,2009,101:19-26.
8. Hadjisavvas V, loannides K, Komodromos M, Mylonas N and Damianou C. Evaluation of the contrast between tissues and thermal lesions in rabbit in vivo produced by high intensity focused ultrasound using fast spin echo MRI sequences. Journal of Biomedical Science and Engineering,2010,4:51-61.
9. Siomos VJ and Barqawi AB. The current status of cryotherapy and high-intensity focused ultrasound in the treatment of low-grade prostate cancer. Reviews on Recent Clinical Trials,2011,21241237.
10. Rowland IJ, Rivens I, Chen L, Lebozer CH, Collins DJ, ter Haar GR and Leach MO. MRI study of hepatic tumors following high intensity focused ultrasound surgery. British Journal of Radiology,1997,70:144-153.
11. Germain D, Chevallier P, Laurent A and Saint-Jalmes H. MR monitoring of tumor thermal therapy. Magnetic Resonance Materials in Physics, Biology and Medicine,2001, 13:47-59.
12. Vogel MW, Pattynama PMT, Lethimonnier FL and Roux PL. Use of fast spin echo for phase shift magnetic resonance thermometry. Journal of Magnetic Resonance Imaging, 2003,18:507-512.
13. Jolesz F, Hynynen K, McDannold N, Freundlich D and Kopelman D. Noninvasive thermal ablation of hepatocellular carcinoma by using magnetic resonance imaging-guided focused ultrasound. Gastroenterology,2004,127:S242-S249.
14. Rieke V and Pauly KB. MR thermometry. Journal of Magnetic Resonance Imaging,2008, 27:376-390
15. Ludemann L, Wlodarczyk W, Nadobny J, Weihrauch M, Gellermann J and Wust P. Non-invasive magnetic resonance thermography during regional hyperthermia. International Journal of Hyperthermia,2010,26(3):273-282.
16. Ajit S, Jeffrey LD and Jonathan SL. Developing a multichannel temperature probe for interventional MRI. Journal of Magnetic Resonance Imaging,1998,8(1):197-202.
17. Galiana G, Branca RT, Jenista ER and Warren WS. Accurate temperature imaging based on intermolecular coherences in magnetic resonance. Science,2008,322:421-424.
18. Hayashi N, Watanabbe Y, Masumoto T, Mori H, Aoki S, Ohtomo K, Okitsu 0 and Takahashi T. Utilization of low-field MR scanners. Magnetic Resonance in Medical Sciences,2004,3: 27-38.
19. Senft C, Franz K, Ulrich CT, Bink A, Szelenyi A, Gasser T and Seifert V. Low field intraoperative MRI-guided surgery of gliomas:A single center experience. Clinical Neurology and Neurosurgery,2010,112(3):237-243.
20. Seifert V, Gasser T and Senft C. Low field intraoperative MRI in glioma surgery. Intraoperative imaging,2011,109(2):35-41.
21. Carl AM, Kensten B and Elsa H. A high performance digital receiver for home-built nuclear magnetic resonance spectrometers. Review of Scientific Instruments,2002,73:453-458.
22. Behin R, Bishop J and Henkelman RM. Dynamic range requirements for MRI. Concepts in Magnetic Resonance,2005,26B:28-35.
23. Otake Y, Kose K and Haishi T. A solution to the dynamic range problem in MRI using a parallel image acquisition. Concepts in Magnetic Resonance,2006,29B:161-167.
24. Brigit LS and William AE. Optimizing MRI signal-to-noise ratio for quadrature unmatched RF coils:Two preamplifiers are better than one. Magnetic Resonance Medical Science, 1996,36:104-110.
25. Valkama M, Renfors M and Koivunen V. Advanced DSP for I/Q imbalance compensation in a low-IF receiver. IEEE International Conference on Communications,2000, 2(3):768-772.
26. Atikinson IC, Lu A and Thulborn KR. Characterization and correction of system delays and eddy currents for MR imaging with ultrashort echo-time and time-varying gradient. Magnetic Resonance in Medicine,2009,62:532-537.
27. Brodsky EK, Samsonov AA and Block WF. Characterizing and correcting gradient errors in non-Cartesian imaging:are gradient errors linear time-invariant? Magnetic Resonance in Medicine,2009,62:1466-1476.
28. Han H, Ouriadov AV, Fordham E and Balcom BJ. Direct measurement of magnetic field gradient waveforms. Concepts in Magnetic Resonance,2010,36A:349-360.
29. Rooney WD, Johnson G, Li X, Cohen ER, Kim SG, Ugurbil K and Springer CS. Magnetic field and tissue dependencies of human brain longitudinal 1H2O relaxation in vivo. Magnetic Resonance in Medicine,2007,57:308-318.
30. Lee KJ, Wild JM, Griffiths PD and Paley MNJ. Simultaneous multislice imaging with slice-multiplexed RF pulses. Magnetic Resonance in Medicine,2005,54:755-760.
31. Poorter JD, Wagter CD, Deene YD, Thomsen C, Stahlberg F, Achten E. Noninvasive MRI thermometry with the proton resonance frequency method:In vivo results in human muscle. Magnetic Resonance in Medicine,1995,33:74-81.
32. Matsumoto R, Multkern RV, Hushek SG and Jolesz FA. Tissue temperature monitoring for thermal interventional therapy: Comparison for T1-weighted MR sequences. Journal of Magnetic Resonance Imaging,1994,4:65-70.
33. Morvan D, Leroy-Willing A, Malgouyres A, Cuenod CA, Jehenson P and Syrota A. Simultaneous temperature and regional blood volume measurements in human muscle using an MRI fast diffusion technique. Magnetic Resonance in Medicine,1993, 29:371-377.
1. Li GY and Xie HB. Digital nuclear magnetic resonance spectrometer. Review of Scientific Instruments,1999,70:1511-1513.
2. Li GY, Jiang Y, Yan XL and Jiang Y. Digital nuclear magnetic resonance spectrometer. Review of Scientific Instruments,2001,72:4460-4463.
3. Jiang Y, Jiang Y, Tao HY and Li GY. A complete digital radio-frequency source for nuclear magnetic resonance spectroscopy. Review of Scientific Instruments,2002,73:3329-3331.
4. Xu Q, Shen J, Jiang Y and Li GY. A Complete digital receiver for nuclear magnetic resonance spectrometer. Chinese Journal of Magnetic Resonance,2005,22:357-365.
5. Xu Q, Shen J, Li JQ and Li GY. Compensation for unknown acquisition delay caused by digital receiver without external synchronization in NMR and MRI. Magnetic Resonance Materials in Physics, Biology and Medicine,2005,18:217-224.
6. Shen J, Xu Q, Liu Y and Li GY. Home-built magnetic resonance imaging system (0.3 T) with a complete digital spectrometer. Review of Scientific Instruments,2005, 76:105101.1-105101.8.
7. Shen J, Ning Ruipeng, Liu Y and Li GY. A method for reducing eddy current induced by gradient coils. Acta Physica Sinica,2006,55:3060-3066.
8. Xu Q, Wang H, Xu ZJ and Li GY. Frequency domain multiplexing for parallel acquisition of MR images. Electronics Letters,2006,42:326-327.
9. Wang H, Xu Q, Ren JJ and Li GY. Four-channel magnetic resonance imaging receiver using frequency domain multiplexing. Review of Scientific Instruments,2007, 78:015102.1-015120.6.
10. Liu Y, Li JQ and Li GY. A novel selective-excitation RF pulse for magnetic resonance imaging. Magnetic Resonance Materials in Physics, Biology and Medicine,2008, 21:199-205.
11. Liu Y and Li GY. F_TDM receiver for parallel acquisition of MRI. Electronics Letters,2008, 44:454-455.
12. Ning RP, Dai YD, Yang G and Li GY. A digital receiver with fast frequency-and gain-switching capabilities for MRI systems. Magnetic Resonance Materials in Physics, Biology and Medicine,2009,22:333-342.
13. Shen J, Liu Y, Li JQ and Li GY. A powerful graphical pulse sequence programming tool for magnetic resonance imaging. Magnetic Resonance Materials in Physics, Biology and Medicine,2005,18:332-342.
14.沈杰,,李鲠颖,国家发明专利ZL200410068161.0,一种用于图形化脉冲序列编译器中实现回波数据重组的方法。
15. Carl AM, Kensten B and Elsa H. A high performance digital receiver for home-built nuclear magnetic resonance spectrometers. Review of Scientific Instruments,2002,73:453-458.
16. Behin R, Bishop J and Henkelman RM. Dynamic range requirements for MRI. Concepts in Magnetic Resonance,2005,26B:28-35.
17. Otake Y, Kose K and Haishi T. A solution to the dynamic range problem in MRI using a parallel image acquisition. Concepts in Magnetic Resonance,2006,29B:161-167.
1. Kose K, Endoh K, Inouye T.1988. Quantization noise reduction by nonlinear amplitude compression. In:7th Annual Meeting of SMRM, San Francisco. p 961.
2. Elliott MA, Insko EK, Greenman RL, Leigh JS. Improved resolution and signal-to-noise ratio in MRI via enhanced signal digitization. J Magn Reson 1998,130:300-304.
3. Behin R, Bishop J, Henkelman RM. Dynamic range requirements for MRI. Concepts Magn Reson 2005,26B:28-35.
4. Otake Y, Kose K, Haishi T. A solution to the dynamic range problem in MRI using a parallel image acquisition. Concepts Magn Rson 2006,29B:161-167.
5. Watts R, Wang Y.2002. k-Space interpretation of the Rose model:noise limitation on the detectable resolution in MRI. Magn Reson Med 48:550-554.
6. Gengying Li, Haibin Xie. Digital quadrature detection in nuclear magnetic resonance spectroscopy. Rev Sci Instrum 1999,70:1511-1513.
7. XC2S50 (2004) Data sheet, Xillinx,1-800-255-7788.
8. AD8331(2008) Data sheet, analog devices, Norwood, MA 02062-9106.
9. AD9244 (2005) Data sheet, analog devices, Norwood, MA,02062-9106.
10. AD6620 (2001) Data sheet, analog devices, Norwood, MA,02062-9106.
1. C.-N. Chen, D. I. Hoult and V. J. Sank. Quadrature detection coils-a further 2 improvement in sensitivity [J]. Journal of Magnetic Resonance (1983),54(2),324-327.
2. Valkama, Mikko, Renfors and Markku, Advanced DSP for I/Q imbalance compensation in a low-IF receiver. IEEE international conference on communications (2000),2(3), 768-772.
3. Feng Linmin, Quadrature head coil of open Mark2000 MRI system [J]. Chinese Journal of Medical Instrumentation (1999),23(6),328-329.
4. Birgit L. Sorgenfrei, William A. Edelstein. Optimizing MRI signal-to-noise ratio for quadrature unmatched RF coils two preamplifiers are better than one [J]. Magnetic Resonance in Medical Science (1996),36,104-110.
5. Wang He, Zhang Lei, Ning Ruipeng, Li Gengying, et al. A method for RF-field mapping based on Fourier transformation. Chinese J Magn Reson,2007,24 (4):446-453.
6. Mei Lixue, Wang He, Li Gengying, et al. A two-channel surface coil for vertebral imaging on low-field MRI systems. Chinese J Magn Reson,2008,25(1):33-38
1. Zhang S, Block KT, Frahm J. (2010) Magnetic Resonance imaging in real time:Advance using radial FLASH. J Magn Reson Imag 31:101-109.
2. De Vita E, Thomas DL, Roberts S, Parkes HG, Turner R, Kinchesh P, Shmueli K, Yousry TA, Ordidge RJ. (2003) High resolution MRI of the brain at 4.7 Tesla using fast spin echo imaging. Brit J Radiol 76:631-637.
3. Han H, Ouriadov AV, Fordham E, Balcom BJ. (2010) Direct measurement of magnetic field gradient waveforms. Concept Magn Reson 36A:349-360.
4. Carlson JW, Derby KA, Hawryszko KC, Weideman M. (1992) Design and evaluation of shielded gradient coils. Magn Reson Med 26:191-206.
5. Turner R. (1993) Gradient coil design:A review of methods. Magn Reson Imaging 11:903-920.
6. Liney G. (2005) MRI from A to Z: A definitive guide for medical professionals, Cambridge University Press, New York, pp164.
7. Gach HM, Lowe IJ, Madio DP, Caprihan A, Altobelli SA, Kuethe DO, Fukushima E. (1998) A programmable pre-emphasis system. Magn Reson Med 40:427-431.
8. Atkinson IC, Lu A, Thulborn KR. (2009) Characterization and correction of system delays and eddy currents for MR imaging with ultrashort echo-time and time-varying gradients. Magn Reson Med 62:532-537.
9. Brodsky EK, Samsonov AA, Block WF. (2009) Characterizing and correcting gradient errors in non-Cartesian imaging:Are gradient errors linear time-invariant (LTI)? Magn Reson Med 62:1466-1476.
10. Peters DC, Derbyshire JA, McVeigh ER. (2003) Centering the projection reconstruction trajectory:Reducing gradient delay errors. Magn Reson Med 50:1-6.
11. Kim DH, Spielman DM. (2006) Reducing gradient imperfections for spiral magnetic resonance spectroscopic imaging. Magn Reson Med 56:198-203.
12. Papadakis NG, Wilkinson AA, Carpenter TA, Hall LD. (1997) A general method for measurement of the time integral of variant magnetic field gradients:Application to 2D spiral imaging. Magn Reson Imag 15:567-578.
13. Reeder SB, Atalar E, Faranesh AZ, McVeigh ER. (1999) Referenceless interleaved echo-planar imaging. Magn Reson Med 41:87-94.
14. Model 281 Three-Axis Gradient Amplifier System With 601S Power Supply, Operating, Installation, and Service Manual. Copley Controls Corp., USA.
15. Odebrecht CC, Tagle D, Zuriaga FB and Steren CA. A pulse grogrammer for nuclear magnetic resonance spectrometers. Concepts in Magnetic Resonance,2007, 30A:127-131.
16. Shen J, Xu Q, Liu Y and Li GY. Home-built magnetic resonance imaging system (0.3 T) with a complete digital spectromer. Review of Scientific Instruments,2005, 76:105101.1105101.8.
17. Shen J, Liu Y, Li JQ and Li GY. A powerful graphical pulse sequence programming tool for magnetic resonance imaging. Magnetic Resonance Materials in Physics, Biology and Medicine,2005,18:332-342.
1. Luigi Landini, Vincenzo Positano, Maria Santarelli 2005 Advanced Image Processing in Magnetic Resonance imaging (New York:CRC Press) p16
2. Lee KJ, Wild JM, Griffiths PD, Paley MNJ 2005 Magn Reson Med 54:755-760
3. John BW.1988 Magn Reson Med 8:275-284
4. Souza SP, Szumowski J, Dumoulin CL, et al.1988 J Comput Assist Tomogr 12:1026-1030
5. Glover GH.1991 J Magn Reson Imaing 1:457-461
6. Rebecca MG, Alex DB 2009 Concepts Magn Reson A 34:305-314
7. Kaiser R 1974 J Magn Reson 15:44-63
8. Ray Freeman 2003 Concepts Magn Reson A17:71-85
9. Meakin P, Jesson JP 1973 J Magn Reson 11:182-206
10. Traficante DD, McGregor MM 2002 Concepts Magn Reson 14:308-325
11. Li Geng-Ying, Jiang Yu, Wu Xue-Wen 1993 Chemical Physics Letters 202 82
12. Li Geng-Ying, Xu Liang, Wu Xue-Wen 1993 Magn. Reson. Chem.31:656-658
13. Li Geng-Ying 1996 Acta Phys. Sin.45(4) 681-688.
14. Li Geng-Ying, Wu Xue-Wen 1991 Acta Phys. Sin.40(10) 1717-1722.
15. Shen Jie, Ning Rui-Peng, Liu Ying, et al 2006 Acta Phys. Sin.55(6) 3060-07.
16. Shen Jie, Xu Qin, Liu Ying, et al 2005 Rev Sci Intrum 76 105101
1. Mika W. Vogel, Peter M. T. Pattynama, Franck L. Lethimonnier, et al. Use of fast spin echo for phase shift magnetic resonance thermometry. J Magn Reson Imaging 2003; 18:507-512.
2. Shankaranarayanan A, Duerk JL, Lewin JS. Developing a multichannel temperature probe for interventional MRI. J Magn Reson Imaging,1998; 81:197-202.
3. Rieke V, Pauly KB. MR thermometry. J Magn Reson Imaging,2008; 27:376-390.
4. Matsumoto R, Multkern RV, Hushek SG, Jolesz FA. Tissue temperature monitoring for thermal interventional therapy: comparison for T1-weighted MR sequences. J Magn Reson Imaging 1994; 4:65-70.
5. Morvan D, Leroy-Willing A, Malgouyres A, Cuenod CA, Jehenson P, Syrota A. Simultaneous temperature and regional blood volume measurements in human muscle using an MRI fast diffusion technique. Magn Reson Med 1993; 29:371-377.
6. Graham SJ, Stanisz GJ, Kecojevic A, Bronskill MJ, Henkelman RM. Analysis of changes in MR properties of tissues after heat treatment. Magn Reson Med 1999; 42:1061-1071.
7. Poorter JD, Wagter CD, Deene YD, et al. Noninvasive MRI thermometry with the proton resonance frequency (PRF) method:in vivo results in human muscle. Magn Reson Med 1995; 33:74-81
8. McDonald N, Tempany C, Jolesz F, Hynynen K. Evaluation of referenceless thermometry in MRI-guided focused ultrasound surgery of uterine fibroids. J Magn Reson Imaging 2008; 28:1026-1032.
9. Ishihara Y, Caleron A, Watanabe H, et al. A precise and fast temperature mapping using water proton chemical shift. Magn Reson Med 1995; 34:814-823.
10. Sinha S, Oshiro T, Sinha U, Lufkin R. Phase imaging on a.2-T MR scanner:application to temperature monitoring during ablation procedures. J Magn Reson Imaging,1997; 7:918-928.
11. Chung YC, Duerk DL, Shankaranarayanan A, Candlng MH, Merkle EM, Lewin JS. Temperature Measurement Using Echo-Shifted FLASH at Low Field for Interventional MRI. J Magn Reson Imaging,1999; 9:138-145.
12. Hayashi N, Watanabe Y, Masumoto T, et al. Utilization of low-field MR scanners. Magn Reson Med Sci 2004; 3:27-38.
13. Blanco RT, Ojala R, Kariniemi J, Perala J, Niinimaki J, Tervonen O. Interventional and intra-operative MRI at low field scanner-a review. Eur J Radiol 2005; 56:130-42.
14. Bauer C, Raich H, Jeschke G, Blumler P. Design of a permanent magnet with a mechanical sweep suitable for variable-temperature continuous-wave and pulsed EPR spectroscopy. J Magn Reson 2009; 198:222-227.
15. El-Sharkawy AM, Schar M, Bottomley PA, Atalar E. Monitoring and correcting spatio-temporal variations of the MR scanner's static magnetic field. Magn Reson Mater Phys 2006; 19:223-236.
16. Barmet C, Zanche ND, Wilm BJ, Pruessmann KP. A transmit/receive system for magnetic field monitoring of in vivo MRI. Magn Reson Med 2009; 62:269-276.
2. ter Haar GR, Sinnett D and Rivens I. High intensity focused ultrasound-A surgical technique for the treatment of discrete liver tumors. Physics in Medicine and Biology, 1989,34:1743-1750.
3. Sibille A, Pra TF, Chapelon JY, Fadil FA, Henry L, Theillere Y, Poncho T and Cathignol D. Extracorporeal ablation of the liver tissue by high-intensity focused ultrasound. Oncology, 1993,50:375-379.
4. Cheng SQ, Zhou ZD, Tang ZY, Yu Y, Wang HZ, Bao SS and Qian DC. High-intensity focused ultrasound in the treatment of experimental liver tumour. Journal of Cancer Research and Clinical Oncology,1997,123:219-223.
5. Chaussy C and Thuroff S. The status of high-intensity focused ultrasound in the treatment of localized prostate cancer and the impact of a combined resection. Current Urology Reports,2003,4:248-252.
6. Leslie TA and Kennedy JE. High-intensity focused ultrasound principles, current uses, and potential for the future. Ultrasound Quarterly,2006,22(4):263-272.
7. Ahmed HU, Zacharakis E, Dudderidge T, Armitage JN, Scott R, Calleary J, Illing R, Kirkham A, Freeman A, Ogden C, Allen C and Emberton M. High-intensity-focused ultrasound in the treatment of primary prostate cancer: the first UK series. British Journal of Cancer,2009,101:19-26.
8. Hadjisavvas V, loannides K, Komodromos M, Mylonas N and Damianou C. Evaluation of the contrast between tissues and thermal lesions in rabbit in vivo produced by high intensity focused ultrasound using fast spin echo MRI sequences. Journal of Biomedical Science and Engineering,2010,4:51-61.
9. Siomos VJ and Barqawi AB. The current status of cryotherapy and high-intensity focused ultrasound in the treatment of low-grade prostate cancer. Reviews on Recent Clinical Trials,2011,21241237.
10. Rowland IJ, Rivens I, Chen L, Lebozer CH, Collins DJ, ter Haar GR and Leach MO. MRI study of hepatic tumors following high intensity focused ultrasound surgery. British Journal of Radiology,1997,70:144-153.
11. Germain D, Chevallier P, Laurent A and Saint-Jalmes H. MR monitoring of tumor thermal therapy. Magnetic Resonance Materials in Physics, Biology and Medicine,2001, 13:47-59.
12. Vogel MW, Pattynama PMT, Lethimonnier FL and Roux PL. Use of fast spin echo for phase shift magnetic resonance thermometry. Journal of Magnetic Resonance Imaging, 2003,18:507-512.
13. Jolesz F, Hynynen K, McDannold N, Freundlich D and Kopelman D. Noninvasive thermal ablation of hepatocellular carcinoma by using magnetic resonance imaging-guided focused ultrasound. Gastroenterology,2004,127:S242-S249.
14. Rieke V and Pauly KB. MR thermometry. Journal of Magnetic Resonance Imaging,2008, 27:376-390
15. Ludemann L, Wlodarczyk W, Nadobny J, Weihrauch M, Gellermann J and Wust P. Non-invasive magnetic resonance thermography during regional hyperthermia. International Journal of Hyperthermia,2010,26(3):273-282.
16. Ajit S, Jeffrey LD and Jonathan SL. Developing a multichannel temperature probe for interventional MRI. Journal of Magnetic Resonance Imaging,1998,8(1):197-202.
17. Galiana G, Branca RT, Jenista ER and Warren WS. Accurate temperature imaging based on intermolecular coherences in magnetic resonance. Science,2008,322:421-424.
18. Hayashi N, Watanabbe Y, Masumoto T, Mori H, Aoki S, Ohtomo K, Okitsu 0 and Takahashi T. Utilization of low-field MR scanners. Magnetic Resonance in Medical Sciences,2004,3: 27-38.
19. Senft C, Franz K, Ulrich CT, Bink A, Szelenyi A, Gasser T and Seifert V. Low field intraoperative MRI-guided surgery of gliomas:A single center experience. Clinical Neurology and Neurosurgery,2010,112(3):237-243.
20. Seifert V, Gasser T and Senft C. Low field intraoperative MRI in glioma surgery. Intraoperative imaging,2011,109(2):35-41.
21. Carl AM, Kensten B and Elsa H. A high performance digital receiver for home-built nuclear magnetic resonance spectrometers. Review of Scientific Instruments,2002,73:453-458.
22. Behin R, Bishop J and Henkelman RM. Dynamic range requirements for MRI. Concepts in Magnetic Resonance,2005,26B:28-35.
23. Otake Y, Kose K and Haishi T. A solution to the dynamic range problem in MRI using a parallel image acquisition. Concepts in Magnetic Resonance,2006,29B:161-167.
24. Brigit LS and William AE. Optimizing MRI signal-to-noise ratio for quadrature unmatched RF coils:Two preamplifiers are better than one. Magnetic Resonance Medical Science, 1996,36:104-110.
25. Valkama M, Renfors M and Koivunen V. Advanced DSP for I/Q imbalance compensation in a low-IF receiver. IEEE International Conference on Communications,2000, 2(3):768-772.
26. Atikinson IC, Lu A and Thulborn KR. Characterization and correction of system delays and eddy currents for MR imaging with ultrashort echo-time and time-varying gradient. Magnetic Resonance in Medicine,2009,62:532-537.
27. Brodsky EK, Samsonov AA and Block WF. Characterizing and correcting gradient errors in non-Cartesian imaging:are gradient errors linear time-invariant? Magnetic Resonance in Medicine,2009,62:1466-1476.
28. Han H, Ouriadov AV, Fordham E and Balcom BJ. Direct measurement of magnetic field gradient waveforms. Concepts in Magnetic Resonance,2010,36A:349-360.
29. Rooney WD, Johnson G, Li X, Cohen ER, Kim SG, Ugurbil K and Springer CS. Magnetic field and tissue dependencies of human brain longitudinal 1H2O relaxation in vivo. Magnetic Resonance in Medicine,2007,57:308-318.
30. Lee KJ, Wild JM, Griffiths PD and Paley MNJ. Simultaneous multislice imaging with slice-multiplexed RF pulses. Magnetic Resonance in Medicine,2005,54:755-760.
31. Poorter JD, Wagter CD, Deene YD, Thomsen C, Stahlberg F, Achten E. Noninvasive MRI thermometry with the proton resonance frequency method:In vivo results in human muscle. Magnetic Resonance in Medicine,1995,33:74-81.
32. Matsumoto R, Multkern RV, Hushek SG and Jolesz FA. Tissue temperature monitoring for thermal interventional therapy: Comparison for T1-weighted MR sequences. Journal of Magnetic Resonance Imaging,1994,4:65-70.
33. Morvan D, Leroy-Willing A, Malgouyres A, Cuenod CA, Jehenson P and Syrota A. Simultaneous temperature and regional blood volume measurements in human muscle using an MRI fast diffusion technique. Magnetic Resonance in Medicine,1993, 29:371-377.
1. Li GY and Xie HB. Digital nuclear magnetic resonance spectrometer. Review of Scientific Instruments,1999,70:1511-1513.
2. Li GY, Jiang Y, Yan XL and Jiang Y. Digital nuclear magnetic resonance spectrometer. Review of Scientific Instruments,2001,72:4460-4463.
3. Jiang Y, Jiang Y, Tao HY and Li GY. A complete digital radio-frequency source for nuclear magnetic resonance spectroscopy. Review of Scientific Instruments,2002,73:3329-3331.
4. Xu Q, Shen J, Jiang Y and Li GY. A Complete digital receiver for nuclear magnetic resonance spectrometer. Chinese Journal of Magnetic Resonance,2005,22:357-365.
5. Xu Q, Shen J, Li JQ and Li GY. Compensation for unknown acquisition delay caused by digital receiver without external synchronization in NMR and MRI. Magnetic Resonance Materials in Physics, Biology and Medicine,2005,18:217-224.
6. Shen J, Xu Q, Liu Y and Li GY. Home-built magnetic resonance imaging system (0.3 T) with a complete digital spectrometer. Review of Scientific Instruments,2005, 76:105101.1-105101.8.
7. Shen J, Ning Ruipeng, Liu Y and Li GY. A method for reducing eddy current induced by gradient coils. Acta Physica Sinica,2006,55:3060-3066.
8. Xu Q, Wang H, Xu ZJ and Li GY. Frequency domain multiplexing for parallel acquisition of MR images. Electronics Letters,2006,42:326-327.
9. Wang H, Xu Q, Ren JJ and Li GY. Four-channel magnetic resonance imaging receiver using frequency domain multiplexing. Review of Scientific Instruments,2007, 78:015102.1-015120.6.
10. Liu Y, Li JQ and Li GY. A novel selective-excitation RF pulse for magnetic resonance imaging. Magnetic Resonance Materials in Physics, Biology and Medicine,2008, 21:199-205.
11. Liu Y and Li GY. F_TDM receiver for parallel acquisition of MRI. Electronics Letters,2008, 44:454-455.
12. Ning RP, Dai YD, Yang G and Li GY. A digital receiver with fast frequency-and gain-switching capabilities for MRI systems. Magnetic Resonance Materials in Physics, Biology and Medicine,2009,22:333-342.
13. Shen J, Liu Y, Li JQ and Li GY. A powerful graphical pulse sequence programming tool for magnetic resonance imaging. Magnetic Resonance Materials in Physics, Biology and Medicine,2005,18:332-342.
14.沈杰,,李鲠颖,国家发明专利ZL200410068161.0,一种用于图形化脉冲序列编译器中实现回波数据重组的方法。
15. Carl AM, Kensten B and Elsa H. A high performance digital receiver for home-built nuclear magnetic resonance spectrometers. Review of Scientific Instruments,2002,73:453-458.
16. Behin R, Bishop J and Henkelman RM. Dynamic range requirements for MRI. Concepts in Magnetic Resonance,2005,26B:28-35.
17. Otake Y, Kose K and Haishi T. A solution to the dynamic range problem in MRI using a parallel image acquisition. Concepts in Magnetic Resonance,2006,29B:161-167.
1. Kose K, Endoh K, Inouye T.1988. Quantization noise reduction by nonlinear amplitude compression. In:7th Annual Meeting of SMRM, San Francisco. p 961.
2. Elliott MA, Insko EK, Greenman RL, Leigh JS. Improved resolution and signal-to-noise ratio in MRI via enhanced signal digitization. J Magn Reson 1998,130:300-304.
3. Behin R, Bishop J, Henkelman RM. Dynamic range requirements for MRI. Concepts Magn Reson 2005,26B:28-35.
4. Otake Y, Kose K, Haishi T. A solution to the dynamic range problem in MRI using a parallel image acquisition. Concepts Magn Rson 2006,29B:161-167.
5. Watts R, Wang Y.2002. k-Space interpretation of the Rose model:noise limitation on the detectable resolution in MRI. Magn Reson Med 48:550-554.
6. Gengying Li, Haibin Xie. Digital quadrature detection in nuclear magnetic resonance spectroscopy. Rev Sci Instrum 1999,70:1511-1513.
7. XC2S50 (2004) Data sheet, Xillinx,1-800-255-7788.
8. AD8331(2008) Data sheet, analog devices, Norwood, MA 02062-9106.
9. AD9244 (2005) Data sheet, analog devices, Norwood, MA,02062-9106.
10. AD6620 (2001) Data sheet, analog devices, Norwood, MA,02062-9106.
1. C.-N. Chen, D. I. Hoult and V. J. Sank. Quadrature detection coils-a further 2 improvement in sensitivity [J]. Journal of Magnetic Resonance (1983),54(2),324-327.
2. Valkama, Mikko, Renfors and Markku, Advanced DSP for I/Q imbalance compensation in a low-IF receiver. IEEE international conference on communications (2000),2(3), 768-772.
3. Feng Linmin, Quadrature head coil of open Mark2000 MRI system [J]. Chinese Journal of Medical Instrumentation (1999),23(6),328-329.
4. Birgit L. Sorgenfrei, William A. Edelstein. Optimizing MRI signal-to-noise ratio for quadrature unmatched RF coils two preamplifiers are better than one [J]. Magnetic Resonance in Medical Science (1996),36,104-110.
5. Wang He, Zhang Lei, Ning Ruipeng, Li Gengying, et al. A method for RF-field mapping based on Fourier transformation. Chinese J Magn Reson,2007,24 (4):446-453.
6. Mei Lixue, Wang He, Li Gengying, et al. A two-channel surface coil for vertebral imaging on low-field MRI systems. Chinese J Magn Reson,2008,25(1):33-38
1. Zhang S, Block KT, Frahm J. (2010) Magnetic Resonance imaging in real time:Advance using radial FLASH. J Magn Reson Imag 31:101-109.
2. De Vita E, Thomas DL, Roberts S, Parkes HG, Turner R, Kinchesh P, Shmueli K, Yousry TA, Ordidge RJ. (2003) High resolution MRI of the brain at 4.7 Tesla using fast spin echo imaging. Brit J Radiol 76:631-637.
3. Han H, Ouriadov AV, Fordham E, Balcom BJ. (2010) Direct measurement of magnetic field gradient waveforms. Concept Magn Reson 36A:349-360.
4. Carlson JW, Derby KA, Hawryszko KC, Weideman M. (1992) Design and evaluation of shielded gradient coils. Magn Reson Med 26:191-206.
5. Turner R. (1993) Gradient coil design:A review of methods. Magn Reson Imaging 11:903-920.
6. Liney G. (2005) MRI from A to Z: A definitive guide for medical professionals, Cambridge University Press, New York, pp164.
7. Gach HM, Lowe IJ, Madio DP, Caprihan A, Altobelli SA, Kuethe DO, Fukushima E. (1998) A programmable pre-emphasis system. Magn Reson Med 40:427-431.
8. Atkinson IC, Lu A, Thulborn KR. (2009) Characterization and correction of system delays and eddy currents for MR imaging with ultrashort echo-time and time-varying gradients. Magn Reson Med 62:532-537.
9. Brodsky EK, Samsonov AA, Block WF. (2009) Characterizing and correcting gradient errors in non-Cartesian imaging:Are gradient errors linear time-invariant (LTI)? Magn Reson Med 62:1466-1476.
10. Peters DC, Derbyshire JA, McVeigh ER. (2003) Centering the projection reconstruction trajectory:Reducing gradient delay errors. Magn Reson Med 50:1-6.
11. Kim DH, Spielman DM. (2006) Reducing gradient imperfections for spiral magnetic resonance spectroscopic imaging. Magn Reson Med 56:198-203.
12. Papadakis NG, Wilkinson AA, Carpenter TA, Hall LD. (1997) A general method for measurement of the time integral of variant magnetic field gradients:Application to 2D spiral imaging. Magn Reson Imag 15:567-578.
13. Reeder SB, Atalar E, Faranesh AZ, McVeigh ER. (1999) Referenceless interleaved echo-planar imaging. Magn Reson Med 41:87-94.
14. Model 281 Three-Axis Gradient Amplifier System With 601S Power Supply, Operating, Installation, and Service Manual. Copley Controls Corp., USA.
15. Odebrecht CC, Tagle D, Zuriaga FB and Steren CA. A pulse grogrammer for nuclear magnetic resonance spectrometers. Concepts in Magnetic Resonance,2007, 30A:127-131.
16. Shen J, Xu Q, Liu Y and Li GY. Home-built magnetic resonance imaging system (0.3 T) with a complete digital spectromer. Review of Scientific Instruments,2005, 76:105101.1105101.8.
17. Shen J, Liu Y, Li JQ and Li GY. A powerful graphical pulse sequence programming tool for magnetic resonance imaging. Magnetic Resonance Materials in Physics, Biology and Medicine,2005,18:332-342.
1. Luigi Landini, Vincenzo Positano, Maria Santarelli 2005 Advanced Image Processing in Magnetic Resonance imaging (New York:CRC Press) p16
2. Lee KJ, Wild JM, Griffiths PD, Paley MNJ 2005 Magn Reson Med 54:755-760
3. John BW.1988 Magn Reson Med 8:275-284
4. Souza SP, Szumowski J, Dumoulin CL, et al.1988 J Comput Assist Tomogr 12:1026-1030
5. Glover GH.1991 J Magn Reson Imaing 1:457-461
6. Rebecca MG, Alex DB 2009 Concepts Magn Reson A 34:305-314
7. Kaiser R 1974 J Magn Reson 15:44-63
8. Ray Freeman 2003 Concepts Magn Reson A17:71-85
9. Meakin P, Jesson JP 1973 J Magn Reson 11:182-206
10. Traficante DD, McGregor MM 2002 Concepts Magn Reson 14:308-325
11. Li Geng-Ying, Jiang Yu, Wu Xue-Wen 1993 Chemical Physics Letters 202 82
12. Li Geng-Ying, Xu Liang, Wu Xue-Wen 1993 Magn. Reson. Chem.31:656-658
13. Li Geng-Ying 1996 Acta Phys. Sin.45(4) 681-688.
14. Li Geng-Ying, Wu Xue-Wen 1991 Acta Phys. Sin.40(10) 1717-1722.
15. Shen Jie, Ning Rui-Peng, Liu Ying, et al 2006 Acta Phys. Sin.55(6) 3060-07.
16. Shen Jie, Xu Qin, Liu Ying, et al 2005 Rev Sci Intrum 76 105101
1. Mika W. Vogel, Peter M. T. Pattynama, Franck L. Lethimonnier, et al. Use of fast spin echo for phase shift magnetic resonance thermometry. J Magn Reson Imaging 2003; 18:507-512.
2. Shankaranarayanan A, Duerk JL, Lewin JS. Developing a multichannel temperature probe for interventional MRI. J Magn Reson Imaging,1998; 81:197-202.
3. Rieke V, Pauly KB. MR thermometry. J Magn Reson Imaging,2008; 27:376-390.
4. Matsumoto R, Multkern RV, Hushek SG, Jolesz FA. Tissue temperature monitoring for thermal interventional therapy: comparison for T1-weighted MR sequences. J Magn Reson Imaging 1994; 4:65-70.
5. Morvan D, Leroy-Willing A, Malgouyres A, Cuenod CA, Jehenson P, Syrota A. Simultaneous temperature and regional blood volume measurements in human muscle using an MRI fast diffusion technique. Magn Reson Med 1993; 29:371-377.
6. Graham SJ, Stanisz GJ, Kecojevic A, Bronskill MJ, Henkelman RM. Analysis of changes in MR properties of tissues after heat treatment. Magn Reson Med 1999; 42:1061-1071.
7. Poorter JD, Wagter CD, Deene YD, et al. Noninvasive MRI thermometry with the proton resonance frequency (PRF) method:in vivo results in human muscle. Magn Reson Med 1995; 33:74-81
8. McDonald N, Tempany C, Jolesz F, Hynynen K. Evaluation of referenceless thermometry in MRI-guided focused ultrasound surgery of uterine fibroids. J Magn Reson Imaging 2008; 28:1026-1032.
9. Ishihara Y, Caleron A, Watanabe H, et al. A precise and fast temperature mapping using water proton chemical shift. Magn Reson Med 1995; 34:814-823.
10. Sinha S, Oshiro T, Sinha U, Lufkin R. Phase imaging on a.2-T MR scanner:application to temperature monitoring during ablation procedures. J Magn Reson Imaging,1997; 7:918-928.
11. Chung YC, Duerk DL, Shankaranarayanan A, Candlng MH, Merkle EM, Lewin JS. Temperature Measurement Using Echo-Shifted FLASH at Low Field for Interventional MRI. J Magn Reson Imaging,1999; 9:138-145.
12. Hayashi N, Watanabe Y, Masumoto T, et al. Utilization of low-field MR scanners. Magn Reson Med Sci 2004; 3:27-38.
13. Blanco RT, Ojala R, Kariniemi J, Perala J, Niinimaki J, Tervonen O. Interventional and intra-operative MRI at low field scanner-a review. Eur J Radiol 2005; 56:130-42.
14. Bauer C, Raich H, Jeschke G, Blumler P. Design of a permanent magnet with a mechanical sweep suitable for variable-temperature continuous-wave and pulsed EPR spectroscopy. J Magn Reson 2009; 198:222-227.
15. El-Sharkawy AM, Schar M, Bottomley PA, Atalar E. Monitoring and correcting spatio-temporal variations of the MR scanner's static magnetic field. Magn Reson Mater Phys 2006; 19:223-236.
16. Barmet C, Zanche ND, Wilm BJ, Pruessmann KP. A transmit/receive system for magnetic field monitoring of in vivo MRI. Magn Reson Med 2009; 62:269-276.