Magnetic Resonance Imaging Safety of Magnetically Controlled Growing Rods in an In Vivo Animal Model.

STUDY DESIGN: Experimental animal study. OBJECTIVE: To investigate the interaction between magnetically controlled growing rods (MCGRs) and magnetic resonance imaging (MRI). SUMMARY OF BACKGROUND DATA: Growing rod treatment through serial operations results in adverse effects on the patient and high treatment costs. MCGRs can be lengthened noninvasively in an outpatient setting and with lower treatment costs. When MRI investigation is required, the interaction between MCGRs and MRI is an issue of concern in patients with MCGRs. This study investigated MRI compatibility of MCGRs in an in vivo setting. METHODS: The study was conducted on three sheep. A standard posterior approach was used. One polyaxial pedicle screw at the ends was placed. Two sheep were instrumented unilaterally and one bilaterally with MCGRs. Temperature change was measured using MR-compatible sensors. Thoracic and lumbar MRIs were obtained using a 0.3 T MRI unit. MRI waves were applied for 45 minutes and temperature changes were recorded every 3 minutes. The lengths of the MCGRs were measured and anteroposterior and lateral spine radiographs were obtained pre- and postoperatively. RESULTS: No displacement in the positions of the MCGRs occurred. The lengths of the MCGRs did not change compared with the preoperative length. The ability of the MCGRs to elongate was not impaired after MRI scanning. There was a mean increase in the temperature of the MCGRs by 1.45°C (0.5-2.4°C). The MCGRs had a strong scattering effect on MRI of the related segments. CONCLUSION: This study indicated that lower magnet MRI is safe in an animal model with MCGRs, with no displacement of the rods and no changes in their length, no significant heating, and no adverse effects on the lengthening mechanism but with a significant scattering effect on visualization of the surrounding tissues. Further investigations are needed to clarify the exact distance where an MRI investigation of distant organs may be done without scattering. LEVEL OF EVIDENCE: N/A.

Quantitative Characterization of Magnetic Mobility of Nanoparticle in Solution-Based Condition.

Magnetic nanoparticles are considered as the ideal substrate to selectively isolate target molecules or organisms from sample solutions in a wide variety of applications including bioassays, bioimaging and environmental chemistry. The broad array of these applications in fields requires the accurate magnetic characterization of nanoparticles for a variety of solution based-conditions. Because the freshly synthesized magnetic nanoparticles demonstrated a perfect magnetization value in solid form, they exhibited a different magnetic behavior in solution. Here, we present simple quantitative method for the measurement of magnetic mobility of nanoparticles in solution-based condition. Magnetic mobility of the nanoparticles was quantified with initial mobility of the particles using UV-vis absorbance spectroscopy in water, ethanol and MES buffer. We demonstrated the efficacy of this method through a systematic characterization of four different core-shell structures magnetic nanoparticles over three different surface modifications. The solid nanoparticles were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD) and saturation magnetization (Ms). The surfaces of the nanoparticles were functionalized with 11-mercaptoundecanoic acid and bovine serum albumin BSA was selected as biomaterial. The effect of the surface modification and solution media on the stability of the nanoparticles was monitored by zeta potentials and hydrodynamic diameters of the nanoparticles. Results obtained from the mobility experiments indicate that the initial mobility was altered with solution media, surface functionalization, size and shape of the magnetic nanoparticle. The proposed method easily determines the interactions between the magnetic nanoparticles and their surrounding biological media, the magnetophoretic responsiveness of nanoparticles and the initial mobilities of the nanoparticles.

Spectral response modification of TiO2 MSM photodetector with an LSPR filter.

We fabricated UVB filtered TiO2 MSM photodetectors by the localized surface plasmon resonance effect. A plasmonic filter structure was designed using FDTD simulations. Final filter structure was fabricated with Al nano-cylinders with a 70 nm radius 180 nm period on 360 nm SiO2film. The spectral response of the TiO2 MSM photodetector was modified and the UVB response was reduced by approx. 60% with an LSPR structure, resulting in a peak responsivity shift of more than 40 nm. To our knowledge, this is the first published result for the spectral response modification of TiO2 photodetectors with LSPR technique.