طراحی و بهینه‌سازی پالس‌های الکترومغناطیسی پیوسته برای مطالعه پدیده انتقال اشباع به واسطه تبادل شیمیایی در تصویربرداری تشدید مغناطیسی با حل عددی معادلات بلاخ-مک‌کانل

رضائیان, محمدرضا; حسین‌زاده, غلامعلی; سلطانیان‌زاده, حمید

doi:10.22041/ijbme.2014.13558

نوع مقاله : مقاله کامل پژوهشی

نویسندگان

¹ ﺩﺍﻧﺸﺠﻮی ﺩﻛﺘﺮی، ﮔﺮﻭﻩ ﺑﻴﻮﺍﻟﻜﺘﺮﻳﮏ، ﻗﻄﺐ ﻋﻠﻤﻰ ﻛﻨﺘﺮﻝ ﻭ ﭘﺮﺩﺍﺯﺵ ﻫﻮﺷﻤﻨﺪ، ﺩﺍﻧﺸﻜﺪﻩ ﻣﻬﻨﺪﺳﻰ ﺑﺮﻕ ﻭ ﻛﺎﻣﭙﻴﻮﺗﺮ، ﺩﺍﻧﺸﮕﺎﻩ ﺗﻬﺮﺍﻥ

² ﺩﺍﻧﺸﻴﺎﺭ، ﮔﺮﻭﻩ ﺑﻴﻮﺍﻟﻜﺘﺮﻳﮏ، ﻗﻄﺐ ﻋﻠﻤﻰ ﻛﻨﺘﺮﻝ ﻭ ﭘﺮﺩﺍﺯﺵ ﻫﻮﺷﻤﻨﺪ، ﺩﺍﻧﺸﻜﺪﻩ ﻣﻬﻨﺪﺳﻰ ﺑﺮﻕ ﻭ ﻛﺎﻣﭙﻴﻮﺗﺮ، ﺩﺍﻧﺸﮕﺎﻩ ﺗﻬﺮﺍﻥ

³ ﺍﺳﺘﺎﺩ، ﮔﺮﻭﻩ ﺑﻴﻮﺍﻟﻜﺘﺮﻳﮏ، ﻗﻄﺐ ﻋﻠﻤﻰ ﻛﻨﺘﺮﻝ ﻭ ﭘﺮﺩﺍﺯﺵ ﻫﻮﺷﻤﻨﺪ، ﺩﺍﻧﺸﻜﺪﻩ ﻣﻬﻨﺪﺳﻰ ﺑﺮﻕ ﻭ ﻛﺎﻣﭙﻴﻮﺗﺮ، ﺩﺍﻧﺸﮕﺎﻩ ﺗﻬﺮﺍﻥ

10.22041/ijbme.2014.13558

چکیده

ﭘﺪﻳﺪﻩ ﺍﻧﺘﻘﺎﻝ ﺍﺷﺒﺎﻉ ﺑﻪ ﻭﺍﺳﻄﻪ ﺗﺒﺎﺩﻝ ﺷﻴﻤﻴﺎﻳﻰ (CEST) ﻛﺎﻧﺘﺮﺍﺳﺘﻰ ﺟﺪﻳﺪ ﺭﺍ ﺩﺭ ﺗﺼﻮﻳﺮﺑﺮﺩﺍﺭی ﺑﻪ ﺭﻭﺵ ﺗﺸﺪﻳﺪ ﻣﻐﻨﺎﻃﻴﺴﻰ (MRI) ﻣﻄﺮﺡ ﻛﺮﺩﻩ ﺍﺳﺖ. ﺍﻳﻦ ﻛﺎﻧﺘﺮﺍﺳﺖ ﺑﺴﻴﺎﺭ ﭘﻴﭽﻴﺪﻩ ﺑﻪ ﭘﺎﺭﺍﻣﺘﺮﻫﺎی ﻣﺘﻌﺪﺩی ﺍﺯ ﺟﻤﻠﻪ ﻧﻮﻉ، ﺷﺪﺕ ﻭ ﺳﺎﻳﺮ ﻭﻳﮋﮔﻰﻫﺎی ﭘﺎﻟﺲ ﺍﻟﻜﺘﺮﻭﻣﻐﻨﺎﻃﻴﺲ (RF) ﺑﺴﺘﮕﻰ ﺩﺍﺭﺩ. ﻋﻤﻮﻣﺎً ﺩﻭ ﻧﻮﻉ ﭘﺎﻟﺲ ﭘﻴﻮﺳﺘﻪ ﻭ ﻳﺎ ﮔﺴﺴﺘﻪ ﺑﺮﺍی ﺍﻧﺠﺎﻡ ﻓﺮﺍﻳﻨﺪ ﺍﺷﺒﺎﻉ ﺑﻜﺎﺭ ﻣﻰﺭﻭﺩ. ﻃﺮﺍﺣﻰ ﭘﺎﻟﺲ RF ﺑﺮ ﺍﺳﺎﺱ ﺣﻞ ﻣﻌﺎﺩﻻﺕ ﺑﻼﺥ- ﻣﮏ ﻛﺎﻧﻞ ﺍﻧﺠﺎﻡ ﻣﻰﺷﻮﺩ. ﻫﺪﻑ ﺍﺻﻠﻰ ﺍﻳﻦ ﻣﻘﺎﻟﻪ ﺍﺳﺘﺨﺮﺍﺝ ﭘﺎﺭﺍﻣﺘﺮﻫﺎی ﭘﺎﻟﺲﻫﺎی ﭘﻴﻮﺳﺘﻪ RF ﺑﻪ ﻧﺤﻮی ﺍﺳﺖ ﻛﻪ ﻣﻨﺠﺮ ﺑﻪ ﺍﺭﺗﻘﺎی ﺍﻳﻦ ﻛﺎﻧﺘﺮﺍﺳﺖ ﺷﻮﺩ. ﭘﺎﻟﺲﻫﺎی ﮔﺴﺴﺘﻪ ﺑﻪ ﺩﻟﻴﻞ ﺿﺮﻳﺐ ﺟﺬﺏ ﻭﻳﮋﻩ ﺍﻣﻮﺍﺝ (SAR) ﺍﺯ ﺗﻮﺟﻪ ﺑﻴﺸﺘﺮی ﺑﺮﺧﻮﺭﺩﺍﺭﻧﺪ؛ ﻭﻟﻰ ﺍﺯ ﺁﻧﺠﺎﻳﻰ ﻛﻪ ﮔﺴﺴﺘﻪﺳﺎﺯی ﺑﺮ ﺍﺳﺎﺱ ﭘﺎﻟﺲﻫﺎی ﭘﻴﻮﺳﺘﻪ ﺍﻧﺠﺎﻡ ﻣﻰﺷﻮﺩ، ﺑﻬﻴﻨﻪﺳﺎﺯی ﭘﺎﻟﺲ ﭘﻴﻮﺳﺘﻪ، ﻣﻨﺠﺮ ﺑﻪ ﭘﺎﻟﺲ ﮔﺴﺴﺘﻪ ﺑﻬﺘﺮی ﺧﻮﺍﻫﺪ ﺷﺪ.. ﺑﻪ ﻫﻤﻴﻦ ﻋﻠﺖ ﻭ ﺍﺯ ﻃﺮﻓﻰ ﺑﺪﻟﻴﻞ ﻣﺮﺳﻮﻡ ﺑﻮﺩﻥ ﺑﻜﺎﺭﮔﻴﺮی ﭘﺎﻟﺲﻫﺎی RF ﺑﺎ ﭘﻮﺵ ﭘﻴﻮﺳﺘﻪ ﻣﺴﺘﻄﻴﻠﻰ، ﮔﻮﺳﻰ ﻭ ﻓﺮﻣﻰ ﺩﺭ ،MRI ﺗﻤﺮﻛﺰ ﺍﺻﻠﻰ ﺍﻳﻦ ﻣﻘﺎﻟﻪ ﺑﺮ ﺍﻳﮕﻮﻧﻪ ﭘﺎﻟﺲﻫﺎ ﺑﻮﺩﻩ ﺍﺳﺖ. ﺩﺭ ﺍﻳﻦ ﺑﺮﺭﺳﻰ ﻋﻼﻭﻩ ﺑﺮ ﺗﺨﺼﻴﺺ ﻋﺮﺽ ﭘﺎﻟﺲ ﻣﺤﺪﻭﺩ ﺑﻪ ﭘﺎﻟﺲﻫﺎی ﮔﻮﺳﻰ ﻭ ﻓﺮﻣﻰ ﺑﺮ ﺍﺳﺎﺱ ﺗﻘﺮﻳﺐ 60dB، ﺑﻪ ﻣﻘﺪﺍﺭ SAR ﻧﻴﺰ ﺗﻮﺟﻪ ﺷﺪﻩ ﺍﺳﺖ. ﺑﺮﺍی ﺁﻧﻜﻪ ﻣﻌﻴﺎﺭ ﺩﺭﺳﺘﻰ ﺍﺯ ﻗﺎﺑﻠﻴﺖ ﭘﺎﻟﺲﻫﺎ ﻭ ﺍﻣﻜﺎﻥ ﻗﻴﺎﺱ ﺁﻧﻬﺎ ﺣﺎﺻﻞ ﺷﻮﺩ، ﻣﻘﺪﺍﺭ ﺯﺍﻭﻳﻪ ﭼﺮﺧﺶ (ﺯﺍﻭﻳﻪ ﺍﻧﺤﺮﺍﻑ) ﻫﻤﻪ ﺁﻧﻬﺎ ﻳﻜﺴﺎﻥ ﺗﻨﻈﻴﻢ ﺷﺪﻩ ﺍﺳﺖ. ﻧﺘﺎﻳﺞ ﻧﺸﺎﻥ ﻣﻰﺩﻫﺪ ﻛﻪ ﺍﺯ ﻟﺤﺎﻅ ﺍﺛﺮ CEST ﻭ SAR ﺑﺘﺮﺗﻴﺐ ﭘﺎﻟﺲ ﻣﺴﺘﻄﻴﻠﻰ، ﻓﺮﻣﻰ ﻭ ﮔﻮﺳﻰ ﺑﻬﺘﺮﻳﻦ ﻋﻤﻜﺮﺩ ﺭﺍ ﺩﺍﺭﻧﺪ. ﺑﻮﺍﺳﻄﻪ ﻣﺸﻜﻼﺕ ﻣﻮﺟﻮﺩ ﺩﺭ ﺳﺎﺧﺖ ﻭ ﺍﺟﺮﺍی ﭘﺎﻟﺲ ﻣﺴﺘﻄﻴﻠﻰ ﻭ ﻫﻤﭽﻨﻴﻦ ﻣﺤﺪﻭﺩﻳﺖﻫﺎﻳﻰ ﻛﻪ ﺑﻮﺍﺳﻄﻪ ﺍﻟﮕﻮی ﻣﻜﺎﻧﻰ ﺗﺤﺮﻳﮏ ﺳﻴﻨﮏ ﮔﻮﻧﻪ ﻭﺟﻮﺩ ﺩﺍﺭﻧﺪ، ﭘﺎﻟﺲﻫﺎی ﮔﻮﺳﻰ ﻭ ﻓﺮﻣﻰ ﻫﻤﭽﻨﺎﻥ ﻣﻮﺭﺩ ﺗﻮﺟﻪ ﻫﺴﺘﻨﺪ. ﺩﺭ ﭘﺎﻟﺲ ﻣﺴﺘﻄﻴﻠﻰ ﺑﻪ ﺍﺯﺍی ﺩﺍﻣﻨﻪ 7/5 ﻣﻴﻜﺮﻭﺗﺴﻼ، ﭘﺎﻟﺲ ﮔﻮﺳﻰ ﺑﻪ ﺍﺯﺍی ﺍﻧﺤﺮﺍﻑ ﻣﻌﻴﺎﺭ 7/0 ﺛﺎﻧﻴﻪ ﻭ ﭘﺎﻟﺲ ﻓﺮﻣﻰ ﺑﻪ ﺍﺯﺍی ﺿﺮﻳﺐ D ، 3/0 ﺛﺎﻧﻴﻪ ﺑﻬﺘﺮﻳﻦ ﻋﻤﻠﻜﺮﺩ ﺭﺍ ﺩﺍﺭﺍ ﺑﻮﺩﻧﺪ؛ ﺍﻳﻦ ﻧﺘﺎﻳﺞ ﺑﺎ ﻓﺮﻣﻮﻝ ﺗﺠﺮﺑﻰ ﻧﻴﺰ ﺗﻄﺎﺑﻖ ﺩﺍﺷﺖ.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Designing and Optimization of Continuous Electromagnetic RF Pulses for Studying CEST MRI by Numerical Solution to the Bloch-McConnell Equations

نویسندگان [English]

Mohammad Reza Rezaeian ¹
Gholam Ali Hossein-Zadeh ²
Hamid Soltanian Zadeh ³

¹ Ph.D Student, Control and Intelligent Processing Center of Excellence (CIPCE), School of Electrical and Computer Engineering, University of Tehran

² Associate Professor, Control and Intelligent Processing Center of Excellence (CIPCE), School of Electrical and Computer Engineering, College of Engineering, University of Tehran

³ Professor, Control and Intelligent Processing Center of Excellence (CIPCE), School of Electrical and Computer Engineering, College of Engineering, University of Tehran

چکیده [English]

Chemical exchange saturation transfer (CEST) is a new mechanism of contrast generation in magnetic resonance imaging (MRI) which differentiates molecule biomarkers via chemical shift. CEST MRI contrast mechanism is very complex and depends on radio frequency (RF) power and RF pulse shape. Two approaches have been used to saturate contrast agent (CA) protons: continuous wave CEST (CW-CEST) and pulsed CEST. To find the optimal RF pulse, numerical solution of Bloch-McConnell equations (BME) may be used. In this paperwe find the optimum values of RF pulse parameters that maximize the CEST contrast. Discrete pulses have lower specific absorption ratio (SAR) than CW RF pulses. However, since discretization is performed on continuous RF pulses, optimizing the continuous RF pulses leads to the optimization of discrete RF pulses. Therefore, in this paper, Rectangular, Gaussian and Fermi pulses are investigated as CW RF pulses. In this investigation, in addition to considering the SAR limitation, 60 dB approximation for the RF pulse amplitude is used. To compare the efficiency of pulses, their resultant flip angles (FA) are assumed equal. Efficiency of CW-CEST is investigated using two parameters, CEST ratio and SAR. According to these parametres, rectangular, Fermi and Gaussian RF pulses have the best performance respectively. Since implementation of rectangular RF is harder than Gaussian and Fermi RF pulses, Fermi and Gaussian RF pulses are desired. Our results suggest that it is possible to maximize CEST ratio by optimizing parameters of rectangular (with an amplitude of 5.7μT), Gaussian (σ about 0.7s) and Fermi (a-value about 0.3s) pulses. Results are verified by empirical formulation of CEST ratio.

کلیدواژه‌ها [English]

Bloch-McConnell equations
CEST MRI
Numerical solution
A-spectra
SAR

مراجع

[1] K.M. Ward, A.H. Aletras and R.S. Balababn, “A new class of CAs for MRI based on proton chemical exchange dependent saturating transfer (CEST),” J Magn Reson, vol.143, pp. 79-87, 2000.

[2] P.C.M. van Zijl and N. Yadav, “Chemical exchange saturation transfer (CEST): what is in a name and what isn’t?”Magnetic Resonance Imaging, vol.65, pp. 927-948, 2011.

[3] G. Liu, “Development of PARACEST MRI to detect cancer biomarkers,”PhD, dissertation, Dept. Biomedical engineering, Case Western Reserve. Univ., 2008.

[4] K.L Desmond, G.J Stanisz, “Understanding quantitative pulsed CEST in the presence of MT,”Magn.Reso.MED, vol.67, no.4, pp.979-990, 2012.

[5] M.R. Rezaeian, G.A. Hossien-Zadehand H.Soltanian-Zadeh, “Numerical Solutions to the Bloch –McConnell Equations with Radio Frequency”,in: Proceedings of the international society of Electrical Engineering, 20^th Conference on Electrical Engineering, Tehran, Iran, pp. 1584-1589, 2012.

[6] M. Kim, J. Gillen, B.A. Lanman, J. Zhou and P.C.M van Zijl “Water saturation shift refrencing (WASSR) for chemical exchange saturation transfer (CEST) experiments,” Magn.Reson.Med , vol.61, pp. 1441-1450, 2009.

[7] J. S. Lee, R.R. Regatte, A. Jerschow “Isolating chemical exchange saturation transfer contrast from magnetization transfer asymmetry under two-frequency RF irradiation, '' J Magn Reson, vol.215, pp.56-63, 2011.

[8] Y. Tee, A. A. Khrapitchev, N. R. Sibson, S. J. Payne, and M. A. Chappell, “Evaluating the use of a continuous approximation for model-based quantification of pulsed chemical exchange saturation transfer (CEST),” J Magn Reson, vol. 45, pp. 767-780, 2012.

[9] E. Vinogradov, A. Dean Sherry, and R. E. Lenkinski, “CEST: from basic principles to applications, challenges and opportunities,” J Magn Reson, 2012.

[10] P.Z. Sun, “Simultaneous determination of labile proton concentration and exchange rate utilizing optimal RF power: radio frequency power (RFP) dependence of chemical exchange saturation transfer (CEST) MRI,” J Magn Reson, vol. 202, no. 2, pp. 155–161, 2010.

[11] B. Schmitt, M. Zaiß, J. Zhou, and P. Bachert, “Optimization of pulse train presaturation for CEST imaging in clinical scanners,” Magn.Reson.Med, vol. 65, no. 6, pp. 1620–1629, 2011.

[12] G. Liu, M. M Ali, B. Yoo, M. A. Griswold, J. A. Tkach and M. D. Pagel, “PARACEST MRI with improved temporal resolution,” Magn. Reson.Med, vol. 61, pp.399-408, 2009.

[13] P.Z. Sun, P. C. M. van Zijl and J. Zhou, “Optimization of the irradiation power in chemical exchange dependent saturation transfer experiments,” J Magn Reson, vol.175, pp. 193-200, 2005.

[14] P.Z. Sun, T. Benner, A. Kumar, and A. G. Sorensen, “Investigation of optimizing and translatingpH‐ sensitive pulsed‐chemical exchange saturation transfer (CEST) imaging to a 3T clinical scanner,” Magn.Reson.Med, vol. 60, no. 4, pp. 834–841, 2008.

[15] M. Zaiss, B. Schmitt and P. Bachert “Quantitative separation of CEST effect from magnetization transfer and spillover effects by lorantzian-line-fit analysis of Z-spectrum,” J Magn Reson, vol.211, pp. 149-155, 2011.

[16] D. Woeessner, S. Zhang, M. E. Merritt and A. D. Sherry “Numerical solution of the Bloch equations provides insights into the optimum design of PARACEST agents for MRI,” Magn. Reson.Med, vol.53, no.4, pp.790-799, 2005.

[17] A. X. Li, R.H.E. Hudson, J.W. Barrett, C. K. Jones, S. H. Pasternak and R. Bartha, “Four-pool modeling of proton exchange processes in biological systems in the presence of MRI-paramagnetic chemical exchange saturation transfer (PARACEST) agents,” Magn. Reson.Med, vol.60, pp. 1197-1206, 2008.

[18] R.V. Mulkern and M. L. Williams, “The general solution to the Bloch equation with constant RF and relaxation terms: application to saturation and slice selection,” Med Phys, vol.20, pp. 5-13, 1993.

[19] S. A. Roell, W. Dreher and D. Leibfritz, “A general solution of the standard magnetization transfer model,”J Magn Reson, vol.132, pp. 96-101, 1998.

[20] P. K. Madhu and A. Kumar “Direct Cartesian- space solutions of generalized Bloch equations in the rotating frame,” J Magn ResonA, vol.114, pp. 201-211, 1995.

[21] K. Murase and N. Tanki, “Numeric solution to the time-dependent Bloch equations revisited,”Magnetic Resonance Imaging, vol.12, no.5, pp. 1-6, 2010.

[22] S. A. Smith, J. A. D. Farrell, C.K Jones, D.S. Reich, P.A. Calabresi and P.C.M van Zijl, “Pulsed magnetization transfer imaging with body coil transmission at 3 Tesla: feasibility and application,” Magn. Reson.Med, vol.56, pp. 866-875, 2006.

[23] M. A. Bernstein, K. F. King, and X. J. Zhou, “Handbook of MRI pulse sequences,’’ Elsevier-Academic Press, 2004, pp. 110.

نشریه‌ی علمی مهندسی پزشکی زیستی

مراجع

مراجع

دوره 8، شماره 1 - شماره پیاپی 1
فروردین 1393
صفحه 87-99

مراجع

مراجع

دوره 8، شماره 1 - شماره پیاپی 1فروردین 1393صفحه 87-99

دوره 8، شماره 1 - شماره پیاپی 1
فروردین 1393
صفحه 87-99