NiFe2O4@SiO2 superparamagnetic nanoparticles as contrast agents in image-guided adaptive brachytherapy (IGABT)

Focusing on the study of superparamagnetic iron oxide samples for applications as contrast agents, the potential utility of NiFe2O4@SiO2 sample as a contrast agent in image guided adapted brachytherapy (IGABT) treatments is described here. This magnetic sample was prepared by controlled hydrothermal synthesis with urea addition and further TEOS reaction using the Sto<spacing diaeresis>ber method. X-ray patterns show diffraction maxima indexed to a cubic symmetry of S. G. Fd-3m with Z = 8, compatible with an inverse spinel-type structure. Polyhedral shape particles with a size of about 21 +/- 5 nm, together with a homogeneous silica coating of 12.7 +/- 1 nm thickness were observed in TEM images Catheters and plastic needles containing NiFe2O4@SiO2 sample in agarose solution mixture were investigated. Images obtained by magnetic resonance imaging (MRI), computed tomography (CT) and X-ray of the ovoid applicator containing NiFe2O4@SiO2 sample in agarose solution mixture, suggest that this sample may be useful for visualizing the source path by performing a T2 weighted MRI and without the need to acquire a CT image. This process reduces uncertainties due to patient movements between imaging modalities as well as procedure time. MRI and CT images of the interstitial needles filled with this solution at different concentrations confirm that it is also suitable for use as a contrast agent. Finally, the investigated sample-agarose mixture was also inserted into a block of human-like pork tissue to approximate an "in vivo" experimentation. The results suggest that the studied sample may be useful in IGABT treatments and intraoperative BT where a series of catheters are implanted into the surgical cavity. Currently, the contrast agents used are not visible inside plastic needles. Our study shows that no toxicity is introduced into the system since the sample is contained within plastic catheters and never encounters the tissue.