Magnetic particle imaging (MPI) based on the nonlinear interaction between internally administered magnetic nanoparticles and electromagnetic waves that externally irradiate the body has attracted attention for the early diagnosis of diseases such as cancer. In MPI, the local magnetic field distribution is scanned, and the magnetization signals are detected from the magnetic nanoparticles inside a target region. However, interference of the magnetization signals generated from the magnetic nanoparticles outside a target region due to nonlinear responses results in the degradation of image resolution. In this study, we clearly show that the degradation of image resolution is a result of the presence of even harmonics in the magnetization response of magnetic nanoparticles. We propose a new image reconstruction method for reducing these even harmonics and a correction method for suppressing the interference of the signals. This is achieved by taking into account the difference between the saturated waveform of the magnetization signal detected from the magnetic nanoparticles outside a target region and that detected from the magnetic nanoparticles inside a target region. In this study, we perform numerical analyses to prove that the image resolution in the molecular imaging technique can be improved by using our proposed image reconstruction method, which is based on the abovementioned ideas. Furthermore, a fundamental system is constructed and the numerical analyses are experimentally validated by using magnetic nanoparticles with a diameter of ~20 nm.

Date Published: 13 March 2009
PDF: 8 pages
Proc. SPIE 7258, Medical Imaging 2009: Physics of Medical Imaging, 72584I (13 March 2009); doi: 10.1117/12.807335

Published in SPIE Proceedings Vol. 7258:
Medical Imaging 2009: Physics of Medical Imaging
Ehsan Samei; Jiang Hsieh, Editor(s)