Active acoustic noise cancellation for MRI

描述(由申请人提供)：这项工作的长期目标是开发一种专门为MRI环境量身定做的可行的声学噪声控制(ANC)系统。这项提议的具体目标是设计、建造和实施一种工作的有源降噪原型，该原型可以显著降低核磁共振钻孔内的声压级。这就需要深入了解核磁共振声场的真实特征。这项研究的中心假设是，MRI操作产生的强烈声能与梯度脉冲强烈相关；因此，它可以由一个不阻碍初级成像操作的有源ANC系统控制。我们相信，从我们的初步研究中揭示的核磁共振声谱的音调行为非常适合于有源噪声消除技术，这种技术通常对可预测的谐波信号起到很好的作用。其基本原理是，磁共振成像抑制声学噪声的能力有望为原型设计提供新的控制算法，这些算法可以进行评估。主动噪声控制在概念上很有吸引力，因为它避免了对核心MRI系统的重大重建。此外，该控制系统的成功实施将消除或至少减少作为非常高场强应用(&gt；7特斯拉)的障碍之一的声学噪声，从而允许在未来的医学成像和研究中采用更高的领域。在这项拟议的研究中，将追求以下具体目标：1)识别和表征可控MRI噪声的性质-调查辐射声压特性，阐明其与各种成像序列的梯度脉冲的函数关系，并识别可控制的显著特征。2)确定可行的传感和激励概念-开发可行的传感和激励方法，有效地抑制MRI扫描仪内孔内的主要声学噪声特征。3)开发ANC系统--设计并实现患者耳口附近主动ANC的原型。

DESCRIPTION (provided by applicant): The long-term goal of this work is to develop a feasible acoustic noise control (ANC) system specifically tailored for MRI environment. The specific objective of this proposal is to design, construct and implement a working active noise reduction prototype that can substantially reduce the sound pressure levels inside the MRI bore. This requires an in-depth understanding of the true characteristics of MRI sound fields. The central hypothesis of this study is that the intense sound energy produced by the operation of MRI is strongly correlated with gradient pulses; and thus it can be controlled by an active ANC system that does not impede the primary imaging operation. It is our belief that the tonal behavior of the MRI sound spectrum revealed from our preliminary studies is well suitable for active noise cancellation techniques that normally work well for predictable harmonic signals. The rationale is that the ability of suppression acoustical noise in MRI is expected to seed new control algorithms that can be evaluated for prototyping. Active noise control is conceptually appealing because it avoids major reconstruction of the core MRI system. Furthermore, the successful implementation of this control system will remove, or at least diminish, acoustic noise as one of the barriers at very high field strength applications (> 7 Tesla), and hence allow for even higher fields to be employed for medical imaging and research in the future. In this proposed studies, the following specific aims will be pursued: 1) Identify and characterize the nature of controllable MRI noise - to investigate the radiated sound pressure characteristics, clarify their functional relationships with the gradient pulses of various imaging sequences, and identify significant features that can be controlled. 2) Determine feasible sensing and actuation concepts - to develop feasible sensing and actuation approaches that will be effective in suppressing the dominant acoustic noise signatures inside the MRI scanner bore. 3) Develop an ANC system - to design and implement a prototype for active ANC in the vicinity of the patient's ear and mouth.