JoVE Journal > Medicine
Summary
Abstract
Introduction
Protocol
Resultados
Discussion
Declarações
Acknowledgements
Materials
Referências
Tadução automática
Please note that all translations are automatically generated. Click here for the English version.
Medicina

7号特斯拉的心脏磁共振成像

Published: January 06, 2019
doi:
10.3791/55853
, , , , , , ,
1The Centre for Advanced Imaging,The University of Queensland, Brisbane, Australia, 2Department of Diagnostic and Interventional Radiology,University Clinic Würzburg, Würzburg, Germany, 3Siemens Healthcare Pty Ltd, Brisbane, Australia, 4Richard Slaughter Centre of Excellence in CVMRI,The Prince Charles Hospital, Brisbane, Australia, 5MRI.Tools GmbH, Berlin, Germany

Summary

超高场磁共振固有的灵敏度增益为心脏的高空间分辨率成像提供了希望。在这里, 我们描述了一个协议定制的功能心血管磁共振 (cmr) 在 7 tesla 使用先进的多通道射频线圈, 磁场闪烁和触发概念。

Abstract

cmr 具有超高磁场 (磁场强度 b 0≥7 tesla), 受益于高磁场强度所固有的信噪比 (snr) 优势, 并有可能提供更好的信号对比度和空间分辨率. 虽然取得了很好的成果, 但由于能量沉积的限制和传输场不均匀性和磁场不均匀等物理现象, 超高场 cmr 具有挑战性。此外, 磁流体力学效应使得数据采集与心脏运动的同步变得困难。目前, 对新型磁共振技术的探索正在应对这些挑战。如果所有的障碍都能克服, 超高场 cmr 可能会为功能 cmr、心肌组织表征、微观结构成像或代谢成像带来新的机会。认识到这一潜力, 我们展示了为 cmr 7 特斯拉量身定制的多通道射频 (rf) 线圈技术 , 以及高阶 b0 闪烁和心脏触发的备用信号, 有利于高保真函数 cmr。通过所提出的设置, 可以在检查时间内完成心脏室量化, 类似于在较低场强时完成的时间。为了分享这一经验并支持传播这一专业知识, 本工作描述了我们在7特斯拉为功能 cmr 量身定制的设置和协议。

Introduction

心血管磁共振 (cmr) 是被证明的临床价值与越来越多的临床适应症 1,2。特别是, 心脏形态和功能的评估是非常重要的, 通常通过跟踪和可视化整个心脏周期的心脏运动, 使用分段呼吸保持二维 (2d) 电影 (cine) 成像技术。虽然需要高时空分辨率、高血心肌对比度和高信噪比 (snr), 但数据采集受到心脏和呼吸运动以及使用多种呼吸保持和需要的高度限制对于整个心脏或左心室覆盖往往会导致大量的扫描时间。并行成像、同时进行多切片成像或其他加速技术有助于解决与运动相关的约束3、4、5、6。

此外, 为了从较高磁场的固有信噪比增益中获益,b0 = 3 tesla 的高场系统越来越多地用于临床常规7,8。这一发展还鼓励了对超高场 (b0≥7 tesla, f≥298 mhz) cmr9、10、11、12、13、14的调查.在 snr 和血心肌对比度的增益固有的更高的场强有希望被转移到增强功能 cmr 使用空间分辨率超过今天的限制 15,16,17. 反过来, 预计将有新的可能性进行基于磁共振的心肌组织特征、代谢成像和微观结构成像.到目前为止, 已有几个小组已经证明了 cmr 在7特斯拉的可行性, 并已推出了专门定制的超高场技术 17,18, 19, 20, 21,22。关于这些有希望的发展, 超高场遗留集束弹药的潜力可被认为尚未开发 13。同时, 物理现象和实际障碍, 如磁场不均匀性、射频激发场 (rf) 不均匀性、非共振伪影、介电效应、局部组织加热和场强度等独立的射频功率沉积约束使超高场成像具有挑战性 10,17。后者用于控制射频诱导组织加热, 确保安全运行。此外, 基于心电图 (ecg) 的触发可能会受到磁流体动力 (mhd) 效应19、23、24 的显著影响。为了应对组织中短波长引起的挑战, 提出了在7 特斯拉为 cmr 量身定制的多元素收发器 rf 线圈阵列 21、25、26、27。并行射频传输为传输场整形提供了手段, 也称为 b1 + 闪烁, 可以减少磁场的不均匀性和易感性 18,28.虽然在目前阶段, 其中一些措施可能会增加实验的复杂性, 概念已被证明是有帮助的, 并可能转化为 cmr 1.5 t 或 3 t 的临床领域的优势。

目前, 二维平衡稳态无进动 (bssfp) cine 成像是 1.5 t 和3t1 临床功能 cmr 的参考标准。最近, 该序列在7特斯拉成功使用, 但仍有大量挑战.应用患者特异性b1 +闪烁和额外的 rf 线圈调整来管理射频功率沉积约束, 并对序列典型的带状伪影进行仔细的 b0 闪烁控制.左心室 (lv) 功能评估的平均扫描时间为 93分钟, 这些努力将检查时间延长到临床可接受的范围之外。在这里, 被破坏的梯度回波序列提供了一个可行的替代方案。在7特斯拉时, 报告了 lv 功能评估的总检查时间 (29±5) 分钟, 这与低场强21的临床成像方案吻合较好。因此, 破坏梯度回波为基础的 cmr 受益于超高场的 t1 松弛时间延长,从而增强了血液心肌对比度优于 1.5 t 梯度回波成像。这使得微妙的解剖结构 , 如心包 , 二尖瓣和三尖瓣 , 以及状肌肉很好地识别。一致的, 被宠坏的梯度回声为基础的心脏室定量在 7 tesla 与 lv 参数得出的 2d bssfp cine 成像在 1.5 t20。除此之外, 准确的右心室 (rv) 室量化最近证明了使用高分辨率破坏梯度回波序列在 7 tesra29 的可行性。

认识到 cmr 在超高领域的挑战和机遇, 这项工作提出了一个设置和协议定制的功能 cmr 收购上的调查 7 tesla 研究扫描仪。该协议概述了技术基础, 显示了如何克服障碍, 并提供了实际注意事项, 有助于将额外的实验开销控制在最低限度。与今天的临床实践相比, 拟议的成像协议是空间分辨率的四倍改进。它旨在为临床适应者、医生科学家、转化研究人员、应用专家、mr 放射技师、技术人员和进入该领域的新进入者提供指导。

Protocol

这项研究得到了澳大利亚昆士兰大学道德委员会的批准, 并从研究中包括的所有科目中获得了知情同意。 1. 科目 在昆士兰大学内部招聘18岁以上的志愿者科目。 知情同意 在进入磁共振成像 (mri) 安全区之前, 告知每个研究对象接受检查的潜在风险。具体而言, 讨论超高磁场暴露和可能的禁忌症进行核磁共振检查。通知参加考试的主体是自愿的, 在任何时候?…

Representative Results

图 4显示了志愿者心脏 cine 检查的代表性结果。显示的是短轴的舒张和收缩时间框架和人的心脏的四室长轴视图。与长轴视图 (图 4a、 4a、4a、4a) 相比, 短轴视图的空间分辨率 (图 4a、 4a、 4a、4a)明显较高。在短轴和长轴切片中, 图…

Discussion

功能 cmr 检查可在特斯拉7成功进行。基于场强驱动的信噪比增益, 可以获得显著较高的空间分辨率的人的心脏的 cine 图像相比, 1.5 或 3 t。虽然在较低的临床场强 1, 30 下, 通常使用6至8毫米的切片厚度和1.2 至2.0 毫米的平面体素边缘长度, 但7特斯拉的测量可以以4毫米的切片厚度和各向同性的方式进行平面内分辨率为 1.0 mm。

在7特斯拉?…

Declarações

The authors have nothing to disclose.

Acknowledgements

提交人承认昆士兰大学高级成像中心国家成像设施的设施和科学和技术援助。我们还要感谢格雷厄姆·加洛威和伊恩·布雷顿帮助索拉尔夫·尼恩多夫获得 caesie 赠款。

Materials

7 Tesla MRI system Siemens Investigational Device
32-Channel -1H-Cardiac Coil MRI.Tools GmbH Transmit/Receive RF Coil for MR Imaging and Spectroscopy at 7.0 Tesla
ECG Trigger Device Siemens
Pulse Trigger Device Siemens
DOWNLOAD MATERIALS LIST

Referências

  1. Kramer, C. M., et al. Standardized cardiovascular magnetic resonance (CMR) protocols 2013 update. Journal of Cardiovascular Magnetic Resonance. 15 (1), 1 (2013).
  2. Earls, J. P., Ho, V. B., Foo, T. K., Castillo, E., Flamm, S. D. Cardiac MRI: Recent progress and continued challenges. Journal of Magnetic Resonance Imaging. 16 (2), 111-127 (2002).
  3. Wintersperger, B. J., et al. Cardiac CINE MR imaging with a 32-channel cardiac coil and parallel imaging: Impact of acceleration factors on image quality and volumetric accuracy. Journal of Magnetic Resonance Imaging. 23 (2), 222-227 (2006).
  4. Schmitt, M., et al. A 128-channel receive-only cardiac coil for highly accelerated cardiac MRI at 3 Tesla. Magnetic Resonance in Medicine. 59 (6), 1431-1439 (2008).
  5. Wech, T., et al. High-resolution functional cardiac MR imaging using density-weighted real-time acquisition and a combination of compressed sensing and parallel imaging for image reconstruction. RöFo: Fortschritte Auf Dem Gebiete Der Röntgenstrahlen Und Der Nuklearmedizin. 182 (8), 676-681 (2010).
  6. Stäb, D., et al. CAIPIRINHA accelerated SSFP imaging. Magnetic Resonance in Medicine. 65 (1), 157-164 (2011).
  7. Gutberlet, M., et al. Influence of high magnetic field strengths and parallel acquisition strategies on image quality in cardiac 2D CINE magnetic resonance imaging: comparison of 1.5 T vs. 3.0 T. European Radiology. 15 (8), 1586-1597 (2005).
  8. Gutberlet, M., et al. Comprehensive cardiac magnetic resonance imaging at 3.0 Tesla: feasibility and implications for clinical applications. Investigative radiology. 41 (2), 154-167 (2006).
  9. Kraff, O., Fischer, A., Nagel, A. M., Mönninghoff, C., Ladd, M. E. MRI at 7 tesla and above: Demonstrated and potential capabilities: Capabilities of MRI at 7T and Above. Journal of Magnetic Resonance Imaging. 41 (1), 13-33 (2015).
  10. Moser, E., Stahlberg, F., Ladd, M. E., Trattnig, S. 7-T MR-from research to clinical applications?. NMR in Biomedicine. 25 (5), 695-716 (2012).
  11. Hecht, E. M., Lee, R. F., Taouli, B., Sodickson, D. K. Perspectives on Body MR Imaging at Ultrahigh Field. Magnetic Resonance Imaging Clinics of North America. 15 (3), 449-465 (2007).
  12. Niendorf, T., et al. W(h)ither human cardiac and body magnetic resonance at ultrahigh fields? technical advances, practical considerations, applications, and clinical opportunities: Advances in ultrahigh field Cardiac and Body Magnetic Resonance. NMR in Biomedicine. 29 (9), 1173-1179 (2016).
  13. Niendorf, T., Sodickson, D. K., Krombach, G. A., Schulz-Menger, J. Toward cardiovascular MRI at 7 T: clinical needs, technical solutions and research promises. European Radiology. 20 (12), 2806-2816 (2010).
  14. Niendorf, T., et al. Progress and promises of human cardiac magnetic resonance at ultrahigh fields: A physics perspective. Journal of Magnetic Resonance. 229, 208-222 (2013).
  15. Hinton, D. P., Wald, L. L., Pitts, J., Schmitt, F. Comparison of Cardiac MRI on 1.5 and 3.0 Tesla Clinical Whole Body Systems. Investigative Radiology. 38 (7), 436-442 (2003).
  16. Ohliger, M. A., Grant, A. K., Sodickson, D. K. Ultimate intrinsic signal-to-noise ratio for parallel MRI: Electromagnetic field considerations. Magnetic resonance in medicine. 50 (5), 1018-1030 (2003).
  17. Vaughan, J. T., et al. Whole-body imaging at 7T: Preliminary results. Magnetic Resonance in Medicine. 61 (1), 244-248 (2009).
  18. Hezel, F., Thalhammer, C., Waiczies, S., Schulz-Menger, J., Niendorf, T. High Spatial Resolution and Temporally Resolved T2* Mapping of Normal Human Myocardium at 7.0 Tesla: An Ultrahigh Field Magnetic Resonance Feasibility Study. PLOS ONE. 7 (12), e52324 (2012).
  19. Suttie, J. J., et al. 7 Tesla (T) human cardiovascular magnetic resonance imaging using FLASH and SSFP to assess cardiac function: validation against 1.5 T and 3 T. NMR in biomedicine. 25 (1), 27-34 (2012).
  20. von Knobelsdorff-Brenkenhoff, F., et al. Cardiac chamber quantification using magnetic resonance imaging at 7 Tesla-a pilot study. European Radiology. 20 (12), 2844-2852 (2010).
  21. Winter, L., et al. Comparison of three multichannel transmit/receive radiofrequency coil configurations for anatomic and functional cardiac MRI at 7.0T: implications for clinical imaging. European Radiology. 22 (10), 2211-2220 (2012).
  22. Schmitter, S., et al. Cardiac imaging at 7 tesla: Single- and two-spoke radiofrequency pulse design with 16-channel parallel excitation: Cardiac Imaging at 7T. Magnetic Resonance in Medicine. 70 (5), 1210-1219 (2013).
  23. Krug, J., Rose, G., Stucht, D., Clifford, G., Oster, J. Limitations of VCG based gating methods in ultra high field cardiac MRI. Journal of Cardiovascular Magnetic Resonance. 15 (Suppl 1), W19 (2013).
  24. Stäb, D., Roessler, J., O’Brien, K., Hamilton-Craig, C., Barth, M. ECG Triggering in Ultra-High Field Cardiovascular MRI. Tomography. 2 (3), 167-174 (2016).
  25. Gräßl, A., et al. Design, evaluation and application of an eight channel transmit/receive coil array for cardiac MRI at 7.0T. European Journal of Radiology. 82 (5), 752-759 (2013).
  26. Graessl, A., et al. Modular 32-channel transceiver coil array for cardiac MRI at 7.0T. Magnetic Resonance in Medicine. 72 (1), 276-290 (2014).
  27. Snyder, C. J., et al. Initial results of cardiac imaging at 7 tesla. Magnetic Resonance in Medicine. 61 (3), 517-524 (2009).
  28. Meloni, A., et al. Detailing magnetic field strength dependence and segmental artifact distribution of myocardial effective transverse relaxation rate at 1.5, 3.0, and 7.0 T: Magnetic Field Dependence of Myocardial R 2 *. Magnetic Resonance in Medicine. 71 (6), 2224-2230 (2014).
  29. von Knobelsdorff-Brenkenhoff, F., et al. Assessment of the right ventricle with cardiovascular magnetic resonance at 7 Tesla. Journal of Cardiovascular Magnetic Resonance. 15, 23 (2013).
  30. Petersen, S. E., et al. Reference ranges for cardiac structure and function using cardiovascular magnetic resonance (CMR) in Caucasians from the UK Biobank population cohort. Journal of Cardiovascular Magnetic Resonance. 19 (1), (2017).
  31. Frauenrath, T., et al. Feasibility of cardiac gating free of interference with electro-magnetic fields at 1.5 Tesla, 3.0 Tesla and 7.0 Tesla using an MR-stethoscope. Investigative radiology. 44 (9), 539-547 (2009).
  32. Frauenrath, T., et al. Acoustic cardiac triggering: a practical solution for synchronization and gating of cardiovascular magnetic resonance at 7 Tesla. Journal of Cardiovascular Magnetic Resonance. 12 (1), 67 (2010).
  33. Schroeder, L., et al. A Novel Method for Contact-Free Cardiac Synchronization Using the Pilot Tone Navigator. Proceedings of the International Society for Magnetic Resonance in Medicine. 24, 3103 (2016).

Tags

Cardiac MRI7 TeslaUltra-high FieldMulti-channel RF CoilSubject PositioningB0 ShimmingECG TriggeringMyocardial Function AssessmentSpatial ResolutionTransceiver ArrayPatient Table SetupPower-splitterPhase-shifterTransmit-receive Interface
check_url/pt/55853?article_type=t

Play Video
PDF
DOI
DOWNLOAD MATERIALS LIST
Citar este artigo
Stäb, D., Al Najjar, A., O’Brien, K., Strugnell, W., Richer, J., Rieger, J., Niendorf, T., Barth, M. Cardiac Magnetic Resonance Imaging at 7 Tesla. J. Vis. Exp. (143), e55853, doi:10.3791/55853 (2019).
Baixar citação
Reimpressões e Permissões

View Video

✖

To prove you're not a robot, please enter the text in the image below

CAPTCHA Image
Play CAPTCHA Audio
Refresh Image