A novel three-dimensional magnetic particle imaging system based on the frequency mixing for the point-of-care diagnostics

Abstract

The magnetic particle imaging (MPI) is a technology that can image the concentrations of the superparamagnetic iron oxide nanoparticles (SPIONs) which can be used in biomedical diagnostics and therapeutics as non-radioactive tracers. We proposed a point-of-care testing MPI system (PoCT-MPI) that can be used for preclinical use for imaging small rodents (mice) injected with SPIONs not only in laboratories, but also at emergency sites far from laboratories. In particular, we applied a frequency mixing magnetic detection method to the PoCT-MPI, and proposed a hybrid field free line generator to reduce the power consumption, size and weight of the system. The PoCT-MPI is [Formula: see text] in size and weighs less than 100 kg. It can image a three-dimensional distribution of SPIONs injected into a biosample with less than 120 Wh of power consumption. Its detection limit is [Formula: see text], 10 mg/mL, [Formula: see text] (Fe).

Figure 1

The proposed PoCT-MPI.

Figure 2

Operation of the PoCT-MPI.

Figure 3

The result of scanning the samples(in dotted red circles) located in four positions of top, bottom, left and right using PoCT-MPI. simulation: (a) samples, (b) sinograms, (c) recontructed images, experiment(PoCT-MPI) : (d) samples, (e) sinograms, (f), recontructed images, (g) superimposed images (d + f).

Figure 4

The sensitivity of the PoCT-MPI. The iron concentrations are 10 mg/mL. (a) negative control, (b) 5 $\mathrm{\mu }\text{L}$, 50 $\mathrm{\mu }\text{g}$ (Fe), (c) 2 $\mathrm{\mu }\text{L}$, 20 $\mathrm{\mu }\text{g}$ (Fe), (d) 1 $\mathrm{\mu }\text{L}$, 10 $\mathrm{\mu }\text{g}$ (Fe), (e) 0.5 $\mathrm{\mu }\text{L}$, 5 $\mathrm{\mu }\text{g}$ (Fe), (f) 0.2 $\mathrm{\mu }\text{L}$, 2 $\mathrm{\mu }\text{g}$ (Fe), (g) 0.13 $\mathrm{\mu }\text{L}$, 1.3 $\mathrm{\mu }\text{g}$ (Fe).

Figure 5

The spatial resolution of the PoCT-MPI.

Figure 6

The scan of rat’s brains in which the SPIONs (dotted red circle) was injected. (a) negative control, (b) 48 $\mathrm{\mu }\text{L}$ SPIONs, (c) 96 $\mathrm{\mu }\text{L}$ SPIONs.

Figure 7

3D scan result of alive mouse. (a) the SPIONs-injected mouse. (b) sinograms. (c) reconstructed images. (d) overlay of RGB and reconstructed image. (e) overlay of X-ray and reconstructed image.

Figure 8

Temperature of the FFL coil.

Figure 9

A timing diagram of DPM.

Figure 10

2D and 3D volume images of sample. (a) image sequence of XY plane, (b) 3D volume image, (c)–(e) 2D images (in top) when Y is 60 mm, 40 mm and 20 mm.

Figure 11

Simulation of the FMMD method. (a) The nonlinear magnetization curve of SPIONs. (b) The magnetic fields consisting of two frequency components $f_1$ and $f_2$. (c) A distorted response signal. (d) A spectrum analysis of response signals with fast fourier transformation (FFT).

Figure 12

FMMD sensor. A radio frequency (RF) coil box in (a) was replaced with (b) for PoCT-MPI. (a) The FMMD sensor. (b) 40 mm (inner diameter) RF coil for PoCT-MPI. (c) The output with no SPIONs. (d) The output with SPIONs.

Figure 13

The proposed FFL generator of the PoCT-MPI. (a) A quadrupole magnet based FFL generator, (b) The proposed hybrid FFL generator in which magnets in one side of (a) are replaced with a coil-based electromagnet so that the sample can be inserted inside in the Z-axis. (c) A computer-aided design (CAD) of PoCT-MPI’s FFL generator. The figure was created using Rhino 6.0. (https://www.rhino3d.com/).

Figure 14

Comparing Selection Field between quadrupole and hybrid magnets. (a) are magnetic fields of quadrupole with a gradient of $(G_x,G_y,G_z)=(2.9,0,-2.9)$ T/m. (b) are the magnetic fields of the proposed hybrid magnet in which amples can be fed into it, with gradient $(2.9,0,-1)$ T/m. (c) shows the measuring result of the manetic field of the prototype of the hybrid magnet.

Figure 15

Rotation and translation of selection field. Each elements consist of three slice of plane,which are XY, XZ, Z-Y plane, respectively. Nine combinations consisting of Z-axis rotation ($-{45}^{\circ }$, 0${}^{\circ }$, 45${}^{\circ }$) and translation $(-40,0,40)$ mm in the rotated X-axis direction is also displayed.

Figure 16

Shifting FFL generator. The FFL generator shifts with the sample fixed. The figure was created using Rhino 6.0.