Frequency distribution of the nanoparticle magnetization in the presence of a static as well as a harmonic magnetic field.
We explore the properties of the signal from magnetic nanoparticles. The nanoparticle signal has been used to generate images in magnetic particle imaging (MPI). MPI promises to be one of the most sensitive methods of imaging small numbers magnetic nanoparticles and therefore shows promise for molecular imaging. The nanoparticle signal is generated with a pure sinusoidal magnetic field that repeatedly saturates the nanoparticles creating harmonics in the induced magnetization that are easily isolated from the driving field. Signal from a selected position is isolated using a static magnetic field to completely saturate all of the particles outside a voxel enabling an image to be formed voxel by voxel. The signal produced by the magnetization of the nanoparticles contains only odd harmonics. However, it is demonstrated experimentally that with the addition of a static magnetic field bias even harmonics are introduced which increase the total signal significantly. Further, the distribution of signal among the harmonics depends on the static bias field so that information might be used to localize the nanoparticle distribution. Finally, the field required to completely saturate nanoparticles can be quite large and theory predicts that the field required is determined by the smallest nanoparticles in the sample.
Department of Radiology, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire 03756, USA. john.b.weaver@dartmouth.edu
John B
JB
Weaver
Adam M
AM
Rauwerdink
Charles R
CR
Sullivan
Ian
I
Baker
D000465:Algorithms; D016477:Artifacts; D004574:Electromagnetic Fields; D004867:Equipment Design; D005290:Ferric Compounds / Q000737:chemistry; D005583:Fourier Analysis; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008280:Magnetics; D053768:Metal Nanoparticles / Q000737:chemistry; D015233:Models, Statistical; D053758:Nanoparticles / Q000737:chemistry; D049329:Nanostructures / Q000737:chemistry; D036103:Nanotechnology / Q000379:methods*; D013696:Temperature
D005290:Ferric Compounds; C000499:ferric oxide