Magnetic particle imaging (MPI) is a new tracer-based imaging modality that is useful in diagnosing various pathophysiology related to the vascular system and for sensitive tracking of cytotherapies. MPI uses nonradioactive and easily assimilated nanometer-sized iron oxide particles as tracers. MPI images the nonlinear Langevin behavior of the iron oxide particles and has allowed for the sensitive detection of iron oxide-labeled therapeutic cells in the body. This review will provide an overview of MPI technology, the tracer, and its use in vascular imaging and cytotherapies using molecular targets.

BackgroundAntimicrobial stewardship (AMS) is a crucial tool for rationalizing the use of antimicrobial agents and reducing the burden of antimicrobial resistance. We aimed to assess the impact of AMS interventions on antimicrobial utilization and adherence to antimicrobial guidelines.MethodsWe conducted a prospective quasi-experimental study at a major tertiary hospital in the United Arab Emirates. Using standardized World Health Organization’s methodology, point-prevalence surveys (PPS) were performed in November 2019 and January 2022. Core AMS interventions consisted of proactive bloodstream infection service, proactive and reactive infectious diseases consult service, prospective audit and feedback by clinical pharmacists, development of antimicrobial guidelines based on cumulative antibiograms, and implementation of induction programs for new clinical staff. Days of therapy (DOT) per 1000 patient days present and rate of compliance with antimicrobial guidelines were compared before and after the core interventions. Multiple logistic regression analysis was carried out to adjust for the potential confounding effects of age, gender, hospitalization within 90 days, central or peripheral line insertion, urinary catheterization, and mechanical ventilation. P-value<0.05 was considered statistically significant.ResultsPre- and post-intervention PPSs included 292 and 370 patients, respectively. Both had similar age and gender distribution. Patients receiving antimicrobials were 51% (149/292) in 2019 and 45% (166/370) in 2022 (p 0.12). Univariate analysis showed a reduced post-intervention DOT per 1000 patients present (6.1 +/- 16.2 vs 2.4 +/-5.1, p<0.01) and an improved post-intervention guideline compliance (59% vs 67%, p 0.23). Following multiple logistic regression, the reduction in post-intervention DOT remained statistically significant (co-efficient -0.17 (95% CI -8.58 to -1.94, p<0.01), and the improvement in guideline adherence became statistically significant (adjusted odds ratio 1.91 (95% CI 1.05 to 3.45, p 0.03).ConclusionCoordinated and sustained AMS interventions have a significant impact on improving antimicrobial utilisation and adherence to guidelines.

Magnetic particle imaging (MPI) is a sensitive, high contrast tracer modality that images superparamagnetic iron oxide nanoparticles (SPIOs), enabling radiation-free theranostic imaging. MPI resolution is currently limited by scanner and particle constraints. Recent tracers have experimentally shown 10x resolution and signal improvements, with dramatically sharper M-H curves. Experiments suggest that this results from interparticle interactions, conforming to literature definitions of superferromagnetism. We thus call our tracers superferromagnetic iron oxide nanoparticles (SFMIOs). While SFMIOs provide excellent signal and resolution, they exhibit hysteresis, with non-negligible remanence and coercivity. We provide the first report on MPI scanning with remanence and coercivity, including the first quantitative measurements of SFMIO remanence decay and reformation using a novel multi-echo pulse sequence. We also describe an SNR-optimized pulse sequence for SFMIOs under human electromagnetic safety limitations. The resolution from SFMIOs could enable clinical MPI with 10x reduced scanner selection fields, reducing hardware costs by up to 100x.

Magnetic particle imaging (MPI) is a sensitive, highcontrast tracer modality that images superparamagnetic iron oxide nanoparticles, enabling radiation-free theranostic imaging. MPI resolution is currently limited by scanner and particle constraints. Recent tracers have experimentally shown 10× resolution and signal improvements with dramatically sharper M−H curves. Experiments show a dependence on interparticle interactions, conforming to literature definitions of superferromagnetism. We thus call our tracers superferromagnetic iron oxide nanoparticles (SFMIOs). While SFMIOs provide excellent signal and resolution, they exhibit hysteresis with non-negligible remanence and coercivity. We provide the first quantitative measurements of SFMIO remanence decay and reformation using a novel multiecho pulse sequence. We characterize MPI scanning with remanence decay and coercivity and describe an SNR-optimized pulse sequence for SFMIOs under human electromagnetic safety limitations. The resolution from SFMIOs could enable clinical MPI with 10× reduced scanner selection fields, reducing hardware costs by up to 100×.