Liu Sitong, Heshmat Anahita, Andrew Jennifer, Barreto Izabella, Rinaldi-Ramos Carlos M
Department of Chemical Engineering, University of Florida Gainesville FL 32611 USA
Department of Radiology, University of Florida Gainesville FL 32610-0374 USA.
Nanoscale Adv. 2023 May 1;5(11):3018-3032. doi: 10.1039/d3na00105a. eCollection 2023 May 30.
Magnetic particle imaging (MPI) is a novel biomedical imaging modality that allows non-invasive, tomographic, and quantitative tracking of the distribution of superparamagnetic iron oxide nanoparticle (SPION) tracers. While MPI possesses high sensitivity, detecting nanograms of iron, it does not provide anatomical information. Computed tomography (CT) is a widely used biomedical imaging modality that yields anatomical information at high resolution. A multimodal imaging agent combining the benefits of MPI and CT imaging would be of interest. Here we combine MPI-tailored SPIONs with CT-contrast hafnium oxide (hafnia) nanoparticles using flash nanoprecipitation to obtain dual-imaging MPI/CT agents. Co-encapsulation of iron oxide and hafnia in the composite nanoparticles was confirmed transmission electron microscopy and elemental mapping. Equilibrium and dynamic magnetic characterization show a reduction in effective magnetic diameter and changes in dynamic magnetic susceptibility spectra at high oscillating field frequencies, suggesting magnetic interactions within the composite dual imaging tracers. The MPI performance of the dual imaging agent was evaluated and compared to the commercial tracer ferucarbotran. The dual-imaging agent has MPI sensitivity that is ∼3× better than this commercial tracer. However, worsening of MPI resolution was observed in the composite tracer when compared to individually coated SPIONs. This worsening resolution could result from magnetic dipolar interactions within the composite dual imaging tracer. The CT performance of the dual imaging agent was evaluated in a pre-clinical animal scanner and a clinical scanner, revealing better contrast compared to a commercial iodine-based contrast agent. We demonstrate that the dual imaging agent can be differentiated from the commercial iodine contrast agent using dual energy CT (DECT) imaging. Furthermore, the dual imaging agent displayed energy-dependent CT contrast arising from the combination of SPION and hafnia, making it potentially suitable for virtual monochromatic imaging of the contrast agent distribution using DECT.
磁粒子成像（MPI）是一种新型的生物医学成像方式，可对超顺磁性氧化铁纳米颗粒（SPION）示踪剂的分布进行无创、断层和定量追踪。虽然MPI具有高灵敏度，能检测到纳克级的铁，但它无法提供解剖学信息。计算机断层扫描（CT）是一种广泛应用的生物医学成像方式，能以高分辨率提供解剖学信息。结合MPI和CT成像优势的多模态成像剂会很有意义。在此，我们利用快速纳米沉淀法将MPI定制的SPION与CT造影剂氧化铪（铪）纳米颗粒相结合，以获得双成像MPI/CT剂。通过透射电子显微镜和元素映射证实了复合纳米颗粒中氧化铁和氧化铪的共包封。平衡和动态磁性表征显示，在高振荡场频率下，有效磁直径减小，动态磁化率谱发生变化，这表明复合双成像示踪剂内部存在磁相互作用。对双成像剂的MPI性能进行了评估，并与商用示踪剂 ferucarbotran进行了比较。该双成像剂的MPI灵敏度比这种商用示踪剂高约3倍。然而，与单独包覆的SPION相比，复合示踪剂的MPI分辨率有所下降。这种分辨率下降可能是由于复合双成像示踪剂内部的磁偶极相互作用所致。在临床前动物扫描仪和临床扫描仪中对双成像剂的CT性能进行了评估，结果显示与商用碘基造影剂相比，其对比度更好。我们证明，使用双能CT（DECT）成像可以将双成像剂与商用碘造影剂区分开来。此外，双成像剂显示出由SPION和氧化铪组合产生的能量依赖性CT对比度，这使其有可能适用于使用DECT对造影剂分布进行虚拟单色成像。
