臺灣博碩士論文加值系統

本論文旨在研究開發一個應用在3T磁振造影系統上，適合接收幼兒腦部影像的多通道射頻接收相列線圈。相列線圈的外罩是設計成服帖於七歲幼兒頭部及頸部曲線以增加雜訊比。相列線圈包含32個圓形的平面線圈。所有的線圈設計為平均直徑8公分，並且均勻地分佈于整個外罩。利用調整線圈重疊區域在最佳面積以及低雜訊前端放大器，我們減少了線圈之間的耦合影響。在性能測試上，S12的平均值為-14dB (最小值 = -28dB)。這個相列線圈是用來接收大腦靜態以及動態的核磁共振訊號。影像分析是與32線圈的成人頭部線圈比較。我們發現幼兒相列線圈以及成人相列線圈的訊雜比的比例在邊緣為1.85，而在中間是差不多的。在動態的磁振造影掃描分析中，從幼兒相列線圈所得的時運上的訊雜比為從成人相列線圈所得的120%。以結論來說，我們設計的多通道射頻接收線圈能為幼兒腦部磁振造影影像提供在時域以及空間上較好的雜訊比。

The aim of this thesis is to develop a multi-channel radio-frequency (RF) receive coil array applicable to pediatric brains on a 3T magnetic resonance imaging (MRI) system. The helmet of the array was designed to fit 7-year-old children’s head and neck in order to improve the signal-to-noise ratio. The array consisted of 32 circular surface coils. All coils had 8 cm diameter and were evenly distributed. By optimally overlapping adjacent coils and using low input-impedance preamplifiers, we reduced the coupling between coils efficiently. The average of S12 from bench measurement was -14dB (minimum = -28dB). This array was used to acquire brain static and dynamic MRI. Images were compared with those from a 32-channel adult head coil array. We found that the ratio of SNR between the image from the pediatric array and that from the adult array at the periphery of the head was 1.85, and nearly the same in the center of the head. In dynamic MRI scans, the mean of temporal SNR (tSNR) of the data acquired from a pediatric array was 120% of that of the data acquired from an adult array. We conclude that our multi-channel RF receiving coil array can provide high SNR and tSNR pediatric brain magnetic resonance images.

口試委員會審定書 #
誌謝 i
中文摘要 ii
ABSTRACT iii
CONTENTS iv
FIGURES vi
TABLES viii
Chapter 1 INTRODUCTION 1
Chapter 2 METHOD 3
2.1 Mechanical housing design 3
2.2 Circuit design 6
2.3 Bench Measurements 8
2.3.1 Tuning, Detuning and Quality Factor 8
2.3.2 Decoupling 8
2.3.3 Preamplifier decoupling and Matching 9
2.4 Imaging Experiments 10
2.4.1 Experiment Sequences 10
2.4.2 Subjects and Phantoms 10
2.4.3 Image Analysis 12
Chapter 3 Results 13
3.1 Bench Measurements 13
3.1.1 Tuning, Detuning and Quality Factor 13
3.1.2 Decoupling 15
3.2 IMAGING EXPERIMENTS 16
3.2.1 Noise correlation 16
3.2.2 Signal-to-noise ratio 16
3.2.3 Anatomical Images 19
3.2.4 SNR map 19
3.2.5 Time-domain SNR (tSNR) 22
Chapter 4 DISCUSSION 25
REFERENCE 27

[1]Keil B, Alagappan V, Mareyam A, McNab JA, Fujimoto K, Tountcheva V, Triantafyllou C, Dilks DD, Kanwisher N, Lin W, Grant PE, Wald LL. Size optimized 32-channel brain arrays for 3 T pediatric imaging. Magn Reson Med 2011;66(6):1777-1787.
[2]J. Hyde, W. Froncisz, A. Jesmanowicz, J. B. Kneeland, T. M. Grist, Parallel image acquisition from noninteracting local coils. J. Magn. Reson. 1986:70, 512.
[3]C. E. Hayes, P. B. Roemer, Noise correlation in data simultaneously acquired from multiple surface coil arrays. Magn. Reson. Med. 1990:16, 181-191.
[4]P. B. Roemer, W. A. Edelstein, C. E. Hayes, S. P. Souza, O. M. Mueller, The NMR phased array. Magn. Reson. Med. 1990:16, 192-225.
[5]Wiesinger F, Boesiger P, Pruessmann KP. Electrodynamics and ultimate SNR in parallel MR imaging. Magn Reson Med 2004;52(2):376-390.
[6]Ohliger MA, Grant AK, Sodickson DK. Ultimate intrinsic signal-to-noise ratio for parallel MRI: electromagnetic field considerations. Magn Reson Med 2003;50(5): 1018-1030.
[7]Zhu Y, Hardy CJ, Sodickson DK, Giaquinto RO, Dumoulin CL, Kenwood G, Niendorf T, Lejay H, McKenzie CA, Ohliger MA, Rofsky NM. Highly parallel volumetric imaging with a 32-element RF coil array. Magn Reson Med 2004;52:869–877.
[8]McDougall MP, Wright SM. 64-channel array coil for single echo acquisition magnetic resonance imaging. Magn Reson Med 2005;54:386–392.
[9]Wiggins GC, Alagappan V, Potthast A, Schmitt M, Wiggins CJ, Fischer H, Jahns K, Benner T, Polimeni J, Wald LL. Design optimization and SNR performance of 3T 96 channel phased array head coils. In: Proceedings of the 15th Annual Meeting of ISMRM, 2007 (Abstract 243).
[10]Schmitt M, Potthast A, Sosnovik DE, Wiggins GC, Triantafyllou C, Wald LL. A 128 channel receive-only cardiac coil for 3T. In: Proceedings of the 15th Annual Meeting of ISMRM, 2007 (Abstract 245).
[11]Wiesinger F. Parallel magnetic resonance imaging: potential and limitations at high field [Dissertation]. Zurich: Swiss Federal Institute of Technology 2005.
[12]Wiggins GC, Triantafyllou C, Potthast A, Reykowski A, Nittka M, Wald LL. 32-channel 3 Tesla receive-only phased-array head coil with soccer-ball element geometry. Magn Reson Med 2006;56: 216–223.
[13]Lanz T, Kellman P, Nittka M, Greiser A, Griswold MA. A 32 channel cardiac array optimized for parallel imaging. Proceedings of the 14th Annual Meeting of ISMRM, Seattle, USA 2006:2578.
[14]Deppe MH, Parra-Robles J, Marshall H, Lanz T, Wild JM. A flexible 32-channel receive array combined with a homogeneous transmit coil for human lung imaging with hyperpolarized 3He at 1.5 T. Magn Reson Med 2011;66(6):1788-1797.
[15]Nordmeyer-Massner JA, De Zanche N, Pruessmann KP. Mechanically adjustable coil array for wrist MRI. Magn Reson Med 2009;61(2):429-438.
[16]V. Alagappan, G. C. Wiggins, J. R. Polimeni, and L. L. Wald. A 32-channel Receive Array Coil for Pediatric Brain Imaging at 3T. In: Proceedings of the 17th Annual Meeting of ISMRM, 2009 (Abstract 108).
[17]Age-Optimized 32-Channel Brain Arrays for 3T Pediatric Imaging. In: In: Proceedings of the 18th Annual Meeting of ISMRM, 2010 (Abstract 643).
[18]Vanderby SA, Babyn PS, Carter MW, Jewell SM, McKeever PD. Effect of anesthesia and sedation on pediatric MR imaging patient flow. Radiology 2010;256:229–237.
[19]Nellhaus G. Head circumference from birth to eighteen years. Practical composite international and interracial graphs. Pediatrics 1968; 41:106–114.
[20]M. Hergt, R. Oppelt, M. D. Vester, A. Reykowski, K. M. Huber, K. Jahns, H. J. Fischer, Low noise preamplifier with integrated cable trap, Proceedings of the 15th Annual Meeting of ISMRM, Berlin, (2007) p. 1037.
[21]C. Possanzini, M. Bouteljie, Influence of magnetic field on preamplifiers using GaAs FET technology, Proceedings of the 16th Annual Meeting of ISMRM, Toronto, (2008) p. 1123.
[22]D. I. Hoult, G. Kolansky, A Magnetic-Field-Tolerant Low-Noise SiGe Pre-amplifier and T/R Switch, Proceedings of the 18th Annual Meeting of ISMRM, Stockholm, (2010) p. 649.
[23]R. Lagore, B. Roberts, B. G. Fallone, N. De Zanche, Comparison of Three Preamplifier Technologies: Variation of Input Impedance and Noise Figure With B0 Field Strength, Proceedings of the 19th Annual Meeting of ISMRM, Montreal, (2011) p. 1864.
[24]G. C. Wiggins, J. R. Polimeni, A. Potthast, M. Schmitt, V. Alagappan, L. L. Wald, 96-Channel receive-only head coil for 3 Tesla: design optimization and evaluation, Magn. Reson. Med. 62 (2009) 754–762.
[25]A. Kumar, W. A. Edelstein, P. A. Bottomley, Noise figure limits for circular loop MR coils, Magn. Reson. Med. 61 (2009) 1201–1209.
[26]Waber DP, De MC, Forbes PW, Almli CR, Botteron KN, Leonard G, Milovan D, Paus T, Rumsey J. The NIH MRI study of normal brain development: performance of a population based sample of healthy children aged 6 to 18 years on a neuropsychological battery. J Int Neuropsychol Soc 2007;13:729–746.
[27]Wang, J., Reykowski, A. and Dickas J. Calculation of the signal-to-noise ratio for simple surface coils and arrays of coils. IEEE Trans. Biomed. Eng. 42, 908–917 (1995).