Technology Science Department, Universidad de Guadalajara, Centro Universitario de la Ciénega, Ocotlan, Jalisco 47810, Mexico.
Department of Physics, FFCLRP, University of São Paulo, Ribeirão Preto, São Paulo 14040-901, Brazil.
Rev Sci Instrum. 2024 Jul 1;95(7). doi: 10.1063/5.0206856.
Magnetomotive ultrasound (MMUS) stands out as a promising and effective ultrasound-based method for detecting magnetic nanoparticles (MNPs) within tissues. This innovative technique relies on the precise estimation of micrometric displacements induced by the interaction of an external magnetic field with MNPs. Pulsed MMUS has emerged as a strategic alternative to address limitations associated with harmonic excitation, such as heat generation in amplifiers and coils, frequency-dependent tissue mechanical responses, and prolonged magnetic field rise times. Despite the growing interest in MMUS, the devices conventionally employed to excite the coil are not specifically tailored to generate intense magnetic fields while minimizing interference with the transient behavior of induced displacements. To bridge this gap, our work introduces the design and fabrication of two pulse generators: one based on a capacitor-discharge circuit and the other on a resonant-inverter circuit. We evaluated the performance of these pulse generators by considering parameters such as the magnetic field generated, rise and fall times, and their ability to supply sustained current for varied pulse widths across different pulse repetition frequencies. Furthermore, we carried out a practical MMUS implementation using tissue-mimicking phantoms, demonstrating the capability of both devices to achieve magnetic fields of up to 1 T and average displacements of 25 µm within the phantom. In addition, we estimated the shear wave velocity, effective shear modulus, and their temperature-dependent variations. Our findings highlight the versatility and efficacy of the proposed pulse generators and emphasize their potential as low-cost platforms for theranostic applications, enabling the assessment of targeted entities within biological tissues.
磁激励超声（MMUS）作为一种有前途且有效的基于超声的方法，可用于检测组织内的磁性纳米颗粒（MNPs）。这项创新技术依赖于对外磁场与 MNPs 相互作用引起的微位移的精确估计。与谐波激励相关的局限性，如放大器和线圈中的热产生、频率相关的组织力学响应和延长的磁场上升时间，促使人们转而采用脉冲 MMUS 技术。尽管人们对 MMUS 的兴趣日益浓厚，但传统上用于激励线圈的设备并非专门设计用于产生强磁场，同时最小化对感应位移瞬态行为的干扰。为了弥补这一差距，我们的工作介绍了两种脉冲发生器的设计和制造：一种基于电容放电电路，另一种基于谐振逆变器电路。我们通过考虑生成的磁场、上升和下降时间以及它们在不同脉冲重复频率下为不同脉冲宽度持续供应电流的能力等参数，评估了这些脉冲发生器的性能。此外，我们使用组织模拟体进行了实际的 MMUS 实现，展示了这两种设备都能够在体模中实现高达 1 T 的磁场和 25 µm 的平均位移。此外，我们还估计了剪切波速度、有效剪切模量及其随温度的变化。我们的研究结果强调了所提出的脉冲发生器的多功能性和有效性，并强调了它们作为低成本平台在治疗诊断应用中的潜力，能够评估生物组织内的靶向实体。
