Utkur M, Muslu Y, Saritas E U
Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey. National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey.
Phys Med Biol. 2017 May 7;62(9):3422-3439. doi: 10.1088/1361-6560/62/9/3422. Epub 2017 Apr 5.
Magnetic particle imaging (MPI) has been shown to provide remarkable contrast for imaging applications such as angiography, stem cell tracking, and cancer imaging. Recently, there is growing interest in the functional imaging capabilities of MPI, where 'color MPI' techniques have explored separating different nanoparticles, which could potentially be used to distinguish nanoparticles in different states or environments. Viscosity mapping is a promising functional imaging application for MPI, as increased viscosity levels in vivo have been associated with numerous diseases such as hypertension, atherosclerosis, and cancer. In this work, we propose a viscosity mapping technique for MPI through the estimation of the relaxation time constant of the nanoparticles. Importantly, the proposed time constant estimation scheme does not require any prior information regarding the nanoparticles. We validate this method with extensive experiments in an in-house magnetic particle spectroscopy (MPS) setup at four different frequencies (between 250 Hz and 10.8 kHz) and at three different field strengths (between 5 mT and 15 mT) for viscosities ranging between 0.89 mPa · s-15.33 mPa · s. Our results demonstrate the viscosity mapping ability of MPI in the biologically relevant viscosity range.
磁粒子成像（MPI）已被证明在诸如血管造影、干细胞追踪和癌症成像等成像应用中能提供显著的对比度。最近，人们对MPI的功能成像能力越来越感兴趣，其中“彩色MPI”技术已探索分离不同的纳米颗粒，这可能用于区分处于不同状态或环境的纳米颗粒。粘度映射是MPI一项很有前景的功能成像应用，因为体内粘度升高与许多疾病有关，如高血压、动脉粥样硬化和癌症。在这项工作中，我们通过估计纳米颗粒的弛豫时间常数，提出了一种用于MPI的粘度映射技术。重要的是，所提出的时间常数估计方案不需要任何关于纳米颗粒的先验信息。我们在内部磁粒子光谱（MPS）装置中，于四个不同频率（250赫兹至10.8千赫兹之间）和三个不同场强（5毫特斯拉至15毫特斯拉之间），针对0.89毫帕·秒至15.33毫帕·秒范围内的粘度进行了广泛实验，验证了该方法。我们的结果证明了MPI在生物学相关粘度范围内的粘度映射能力。
