Safety of metallic implants in magnetic resonance imaging

Cataloged from PDF version of article.Magnetic Resonance Imaging (MRI) is safe only if we take safety precautions. In the presence of a metallic implant inside the body, three types of magnetic fields encountered in MRI (Static magnetic field, radiofrequency field, gradient field) may become the sources of safety problems. In this thesis, temperature increase created by a pacemaker under MRI is investigated. Electromagnetic simulations are performed, in-vivo, phantom experiments are conducted and finally bioheat equation is solved to find the corresponding temperature increase. Using this temperature increase the input power can be limited to ensure safe scans. MRI compatible lead design is the essential innovation of this thesis which is directly applicable to any kind of metallic, wire shaped interventional MRI device.Ferhanoğlu, OnurM.S

Ultra-stable nano-micro bubbles in a biocompatible medium for safe delivery of anti-cancer drugs

Abstract We conducted a series of experimental investigations to generate laser-stimulated millimeter bubbles (MBs) around silver nanoparticles (AgNPs) and thoroughly examined the mechanism of bubble formation within this nanocomposite system. One crucial aspect we explored was the lifetime and kinetics of these bubbles, given that bubbles generated by plasmonic nanoparticles are known to be transient with short durations. Surprisingly, our findings revealed that the achieved lifetime of these MBs extended beyond seven days. This impressive longevity far surpasses what has been reported in the existing literature. Further analysis of the experimental data uncovered a significant correlation between bubble volume and its lifetime. Smaller bubbles demonstrated longer lifetimes compared to larger ones, which provided valuable insights for future applications. The experimental results not only confirmed the validity of our model and simulations but also highlighted essential characteristics, including extended lifetime, matching absorption coefficients, adherence to physical boundary conditions, and agreement with simulated system parameters. Notably, we generated these MBs around functionalized AgNPs in a biocompatible nanocomposite medium by utilizing low-power light excitation. By readily binding potent cancer drugs to AgNPs through simple physical mixing, these medications can be securely encapsulated within bubbles and precisely guided to targeted locations within the human body. This capability to deliver drugs directly to the tumor site, while minimizing contact with healthy tissues, can lead to improved treatment outcomes and reduced side effects, significantly enhancing the quality of life for cancer patients

A speckle-enhanced prism spectrometer with high dynamic range

WOS: 000451914600015We present a novel spectrometer device offering a wide wavelength range and high resolution. The device builds upon a conventional prism spectrometer; however, an additional scattering medium is introduced to generate a wavelength-dependent speckle pattern on the detector array. Simultaneous use of the prism and the scattering medium allows for both improved resolution and wavelength range. The generated speckle pattern secures a significant improvement in the resolution (up to 100 folds) and dynamic range over a conventional prism spectrometer. With the proposed spectrometer, implemented using a CCD camera, we demonstrate up to 17-pm resolution at 855-nm central wavelength and 756.5-nm wavelength range revealing a dynamic range of similar to 44 500. The dynamic range could be further improved upon using a detector array having larger area and a scattering medium offering a nar-rower spectral correlation function. With further development, the proposed device could be useful in a variety of spectroscopy applications, such as deep imaging of retinal layers in optical coherence tomography.Scientific and Technological Research Council of Turkey (TUBITAK) [116F142]This work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK) under Grant 116F142

Speckle-enhanced prism spectrometer

We present an improved prism spectrometer with high wavelength range and spectral resolution. The device is an upgraded prism spectrometer that utilizes an additional scattering medium leading to a wavelength-dependent speckle pattern. We demonstrate < 20 pm resolution and \sim 750 nm wavelength range with the proposed device. With the demonstrated spectral resolution, the speckle-enhanced prism could provide the means to image deep tissue layers in Optical Coherence Tomography.Türkiye Bilimsel ve Teknoloji Araştırma Kurumu (TÜBİTAK

Scattering metal waveguide based speckle-enhanced prism spectrometry

We present an optical efficiency improved speckle spectrometer where a scattering metal wave-guide is utilized along with a conventional prism spectrometer. We conducted extensive tests on 25 different scatterers, involving a variety of nanoparticle concentrations, scattering layer thicknesses, and wave-guide vs. non-guiding type scatterers. We observed 35 pm spectral resolution at 1.3% optical efficiency, which we could only achieve with similar to 0.01% optical efficiency using a conventional non-guiding scatterer. Thus our new implementation provides up to two orders of magnitude improvement in optical efficiency at the same spectral resolution, as opposed to scatterers that are not sandwiched between metal plates. The improvement in optical efficiency allows for rapid (similar to 5 mu sec exposure) acquisition of the spectrum with a conventional CMOS camera. Thanks to its excellent spectral resolution and diminished optical losses, the proposed spectrometer could be utilized in high frame-rate, real time spectrum reconstruction applications, such as Optical Coherence Tomography

In-situ measurement of anisotropic Young’s modulus in fused deposition modeling printed cantilevers

In this study, we investigate the effect of fused deposition modeling printing direction on the effective Young's modulus value of cantilevers. Through finite-element simulations and experiments with seven different dimensions and totaling over 100 cantilevers, we have observed the impact of printing direction on cantilever resonance. Unlike the conventional compressive and tensile stress-strain characterization, observation of the resonance allows for in-situ testing on the final device under test during operation. Initially, we observed the bulk filament modulus to be 4.5 GPa based on the optimal match between experiments and realistic finite element models expressing the internal structures of the longitudinal and transverse printed cantilevers. Then, the effective Young's modulus of the cantilevers is inferred through sweeping the Young's modulus that provides the best fit between the experiments, conventional cantilever formulations and finite-element simulations with solid, homogeneous, and isotropic cantilever model. Overall, we observed an average effective Young's modulus of 3.35 GPa for the cantilevers with longitudinal (along the cantilever axis) deposited filaments and an average effective Young's Modulus of 2.50 GPa for the transverse (perpendicular to the cantilever axis, along the width dimension) deposited Polylactic acid cantilevers. Eventually, simplified shape outline and effective Young's modulus for the corresponding printing direction eases the subsequent theoretical and simulation analyses. The presented methodology is also applicable to micrometric and sub-micrometric scale serial manufacturing techniques (i.e. two-photon polymerization) where the laser beams steering direction causes anisotropy in the mechanical properties of the device under test.TUBA-GEBIP ; Türkiye Bilimler Akademis