Application of Magnetic Particle Imaging to Pulmonary Imaging Using Nebulized Magnetic Nanoparticles

Abstract

Purpose: To investigate the feasibility of applying magnetic particle imaging (MPI) to pulmonary imaging using nebulized magnetic nanoparticles (MNPs) and to quantify the mucociliary clearance in the lung, using small animal experiments. Materials and Methods: Intrapulmonary administration of MNPs was performed in seven-week-old male ICR (Institute of Cancer Research) mice (n = 8) using a nebulized microsprayer connected to a high-pressure syringe containing 50 μL of MNPs (500 mM Resovist®). We imaged the lungs using our MPI scanner 2.5 hours, 1 day, 3 days, and 7 days after the intrapulmonary administration of MNPs. The average MPI value was calculated by drawing a region of interest (ROI) on the lungs by taking the threshold value for extracting the contour as 20% of the maximum MPI value within the ROI. The MPI value was defined as the pixel value of the transverse image reconstructed from the third-harmonic signals. Mice were sacrificed immediately after the last MPI and X-ray CT studies on day 7, and 5 lobes of the lung in each mouse were extracted to confirm the accumulation of iron using Berlin blue staining. Results: We could visualize the distribution of MNPs in the lungs as positive contrast using MPI with use of nebulized MNPs. The presence of iron in the lung was confirmed by Berlin blue staining. The average MPI value decreased with time and tended to saturate. The clearance rate was calculated to be 0.505 day −1 from the time course of the average MPI value in the lungs. Conclusion: Our preliminary results suggest that MPI can be applied to pulmonary imaging by nebulizing MNPs and can be useful for quantifying the mucociliary clearance in the lung.

Firstin vivomagnetic particle imaging of lung perfusion in rats

“…This work on MPI lung perfusion adds to previous work on MPI preclinical imaging in the torso region, including on lung ventilation, whole body blood pool imaging and whole body stem cell tracking (showing 200 cell sensitivity) (Nishimoto et al 2015; Keselman et al 2016; Zheng, Vazin, et al 2015; Zheng, See, et al 2016). Collectively, the high quality images and range of applications demonstrated in the literature suggest the general utility of MPI for lung imaging.…”

“…Previously, Nishimoto (Nishimoto et al 2015) demonstrated promise for MPI in lung imaging with the first in vivo MPI ventilation studies in mice using a nebulized microsprayer to deliver Resovist to the lungs. Here, we report a method for preparing a novel MPI lung perfusion imaging agent, macroaggregated albumin-SPIOs (MAA-SPIOs), and demonstrate its efficacy and biodistribution for in vivo MPI lung perfusion imaging in rats.…”

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

“…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.…”

The relaxation wall: experimental limits to improving MPI spatial resolution by increasing nanoparticle core size

“…MPI is best compared to gold-standard tracer imaging techniques, such as nuclear medicine, but without the limitations of radiation safety or radionuclide half-life for longitudinal imaging. As such, MPI shows excellent promise for clinical applications such as angiography (Haegele et al 2012; Salamon et al 2016), stem cell tracking and vitality assessment (Fidler et al 2015; Them et al 2016; Zheng, Vazin, et al 2015; Zheng, von See, et al 2016), brain perfusion (Orendorff et al 2016), lung perfusion (Zhou et al 2016),lung ventilation (Nishimoto et al 2015), cancer imaging (E. Yu et al 2016), and localized hyperthermia (Murase, Aoki, et al 2015; Hensley et al 2016).…”