Usefulness of Magnetic Particle Imaging for Monitoring the Effect of Magnetic Targeting

Abstract

Purpose: Magnetic targeting refers to the attachment of therapeutic agents to magnetizable particles such as magnetic nanoparticles (MNPs) and then applying magnetic fields to concentrate them to the targeted region such as solid tumors. The purpose of this study was to investigate the usefulness of magnetic particle imaging (MPI) for monitoring the effect of magnetic targeting using tumor-bearing mice. Materials and Methods: Colon-26 cells (1 × 10 6 cells) were implanted into the backs of eight-week-old male BALB/c mice. When the tumor volume reached approximately 100 mm 3 , the mice were divided into treated (n = 8) and untreated groups (n = 8). The tumors in the treated group were directly injected with MNPs (Resovist ® , 250 mM) and a neodymium magnet was attached to the tumor surface, whereas the magnet was not attached to the tumor in the untreated group. The mice were imaged using our MPI scanner and the average and maximum MPI values were obtained by drawing a region of interest (ROI) on the tumor, with the threshold value for extracting the contour of the tumor being taken as 40% of the maximum MPI value in the ROI. The relative tumor volume growth (RTVG) was calculated from (V − V0)/V0, where V0 and V represented the tumor volume immediately before and after the injection of MNPs, respectively. Results: The average and maximum MPI values in the treated group were significantly higher than those in the untreated group 3 days after the injection of MNPs, suggesting the effectiveness of magnetic targeting. There were no significant differences in RTVG between the two groups. Conclusion: Our preliminary results suggest that MPI is useful for monitoring the effect of magnetic targeting.

Combining magnetic particle imaging and magnetic fluid hyperthermia in a theranostic platform

“…In the saturated regions, the particles are effectively locked in place and neither an appreciable MPI signal nor heating occur in response to an AC excitation field. We and other groups have been actively exploring the ramifications of MPI and gradient fields in MFH (Tasci et al 2009; Khandhar et al 2012; Murase, Takata, et al 2013; Murase, Aoki, et al 2015; Kuboyabu et al 2016; Maruyama et al 2016; Bauer et al 2016; Behrends, Buzug, and A. Neumann 2016). …”

“…MPI has been used in several in vivo application domains to date, including cell tracking (Zheng, Vazin, et al 2015; Zheng, See, et al 2016), cancer imaging (Yu et al 2016), blood pool and perfusion imaging (Orendorff et al 2016), angiography and cardiac imaging (J Weizenecker et al 2009), lung ventilation and perfusion studies (Nishimoto et al 2015; Zhou et al 2016), and predicting the effect of MFH (Kuboyabu et al 2016). These results highlight the strengths of MPI: zero background signal, zero depth attenuation of the signal, high sensitivity, linear quantification, and no half-life associated with the tracer signal such that physiologic clearance times determine the time horizons available in longitudinal studies.…”

In vivo tracking and quantification of inhaled aerosol using magnetic particle imaging towards inhaled therapeutic monitoring

“…This enabled localized treatment of tumors (potentially lung tumors) while sparing other tissues with non-specific SPION uptake 47 , 50 . Furthermore, because SPIONs can be shifted by magnetomotive forces from magnetic gradient fields, the therapeutic aerosol can be additionally moved in an image-guided fashion to a target region of the lung, increasing therapeutic efficiency 43 , 74 .…”

Magnetic particle imaging: tracer development and the biomedical applications of a radiation-free, sensitive, and quantitative imaging modality

“…MPI is particularly useful because of the linear quantitation and lack of background signal, providing spatial information which allows the accurate monitoring of therapeutic agent delivery. 306 This information illustrates the quantity of drug delivered to the target site, as well as the drug dosage distribution within the body. The ability to track drug delivery also allows for real-time adjustment of ensuing doses, ensuring that the dosage at the target site remains within the patient's therapeutic window (Fig.…”