Feedback Control for Transportation of Magnetic Fluids With Minimal Dispersion: A First Step Toward Targeted Magnetic Drug Delivery
Feedback Control for Transportation of Magnetic Fluids With Minimal Dispersion: A First Step Toward Targeted Magnetic Drug Delivery
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DOI：
10.1109/tcst.2016.2539322
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发表时间：
2017-01-01
影响因子：
4.8
通讯作者：
Komaee, Arash
中科院分区：
文献类型：
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作者：
Komaee, Arash
在靶向磁性药物输送中，附着在磁性纳米颗粒上的药物通过外加磁场以较高的浓度输送到体内的靶向区域(如肿瘤)。除了人体的复杂性带来的许多技术困难外，该方案的性能在概念上受到磁场的固有趋势的限制，即分散在其作用力下运动的任何磁性粒子星座。当一点磁性流体(磁性纳米颗粒在水中的悬浮液)在磁场中运动时，这种趋势会导致浓度的逐渐损失。为了将这种不良影响减小到可接受的程度，提出了一种电磁铁动态控制的反馈控制策略，以最小的色散将磁流体光斑从磁区的边缘驱动到中心目标。用磁流体的质心和分布的协方差矩阵来表示磁流体的斑点，这些控制目标被描述为一个最优控制问题，它约束前者的运动，同时最小化后者的轨迹(作为分散度的一种度量)。为了简化这一问题的求解，将精确由偏微分方程组描述的铁磁流体动力学近似为一组有限维状态空间方程，通过进一步逼近Hamilton-Jacobi-Bellman方程，给出了这一较简单模型的次优控制。给出了闭环系统的仿真结果，结果表明，所提出的控制方法能够将磁流体光斑以较小的分散度移动到中心目标。
In targeted magnetic drug delivery, drugs attached to magnetic nanoparticles are delivered to targeted regions of the body (e.g., tumors) at high concentrations by the application of external magnetic fields. Beyond many technical difficulties posed by the complexities of the human body, the performance of this scheme is limited in concept by the inherent tendency of the magnetic fields to disperse any constellation of magnetic particles moving under their applied forces. This tendency causes a gradual loss of concentration when a spot of ferrofluid (suspension of magnetic nanoparticles in water) moves inside a magnetic field. To minimize this undesirable effect to an acceptable level, a feedback control policy for the dynamic control of electromagnets is presented to drive a ferrofluid spot from the edge of a domain to a central target with minimal dispersion. Representing the spot of ferrofluid by its center of mass and the covariance matrix of its distribution, these control goals are formulated as an optimal control problem that constrains the motion of the former, while minimizing the trace of the latter (as a measure of dispersion). To simplify the solution of this problem, the ferrofluid dynamics, which is precisely governed by a partial differential equation, is approximated by a finite-dimensional set of state-space equations, and a suboptimal control is developed for this simpler model by further approximation of the Hamilton-Jacobi-Bellman equation. Simulation results are presented for the closed-loop system, which demonstrate that the proposed control is able to move the ferrofluid spot to a central target with reasonably small dispersion.