粒径分布对磁性粒子成像采样频率范围的影响

Particle size distribution on the influence of magnetic particle imaging acquisition frequency range

为了研究磁性粒子成像(magnetic particle imaging,MPI)中采样频率和粒径分布对测量精度的影响,对一维MPI模进行仿真分析,发现确保准确求解浓度分布函数所需的有效频率范围并不是固定的,而是随着某些参数的变化而变化,即MPI中存在最低采样频率。若系统采样频率低于这一值,则不管信噪比多高,均无法得到准确的样品浓度分布。这其实是香农采样定理在MPI中的体现。在影响最低采样频率的诸多因素中,样品粒径分布带来的影响最为突出。最后,在合适的采样参数设置规则下,求出不同粒径分布所对应的最低采样频率,并从求解算法入手分析,对最低采样频率随粒径分布参数的变化规律给出了合理解释。

To determine the impact of sampling frequency and particle size distribution on measurement accuracy in magnetic particle imaging（MPI）,by analying the simulation of one-dimensional model of MPI,we found the required frequency range for the accurate solution of magnetic nanoparticles（MNPs）concentration in sample was not fixed,but varied with the changes of some parameters,thus the concept of minimum sampling frequency was proposed.If the selected sampling frequency is less than the minimum sampling frequency,the accurate distribution of MNPs in sample cannot be obtained regardless of how high the signalto-noise-ratio（SNR）is.Among the factors affecting the minimum sampling frequency,an analysis of the impact that the size distributions of MNPs has on the minimum sampling frequency is focused upon.Besides,an appropriate rule of sampling parameter settings is used to obtain the minimum sampling frequency corresponding to different size distribution of MNPs.Furthermore,through the analysis of solution algorithm,this paper gives a reasonable explanation on variation rules that minimum sampling frequency varies with the parameters of particle size distribution.