Browsing by Author "Alipour, Akbar"
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Item Open Access Heterodoped manoparticles as dual-mode contrast agent for MRI(IEEE, 2018) Alipour, Akbar; Sharma, Vijay Kumar; Soran-Erdem, Zeliha; Kelestemur, Yusuf; Aykut, Zaliha Gamze; Demir, Hilmi VolkanThe purpose of this work is to synthesize Mn-Fe heterodoped ZnSe tetrapod nanocrystals (NCs) as dualmode MRI contrast agent to offer synergetic beneficial over the single contrast tracer. Also, in vivo feasibility of the Mn-Fe heterodoped ZnSe tetrapod NCs as a dualmode contrast agent has been studied.Item Open Access A new class of cubic SPIONs as a dual-mode T1 and T2 contrast agent for MRI(Elsevier, 2018) Alipour, Akbar; Soran-Erdem, Zeliha; Utkur, Mustafa; Sharma, Vijay Kumar; Algın, Oktay; Sarıtaş, Emine Ülkü; Demir, Hilmi VolkanSuperparamagnetic iron oxide nanoparticles (SPIONs) are widely used as a robust negative contrast agent on conventional MRI. In this study, we (a) synthesized a new class of cubic SPIONs as a dual-mode contrast agent in MRI and (b) showed the in-vivo feasibility of these nanaoparticles as a simultaneous positive and negative contrast agent. Relaxation properties and contrast enhancement analysis of the synthesized SPIONs with two different shapes (cubic vs. spherical) and three different sizes 7 nm, 11 nm, and 14 nm were investigated to evaluate contrast enhancement in-vitro. In-vivo MRI experiments were performed on a 3T MR scanner, where a healthy anesthetized rat was imaged before, and from 20 to 80 min after intravenous injection of 1 mg/kg of contrast agent. Representative transmission electron microscopy (TEM) images of the synthesized nanoparticles reveal that the particles are well dispersed in a solvent and do not aggregate. The in-vitro relaxivity and contrast enhancement analysis show that, among all six SPIONs tested, 11-nm cubic SPIONs possess optimal molar relaxivities and contrast enhancement values, which can shorten the spin-lattice and spin-spin relaxation times, simultaneously. No noticeable toxicity is observed during in-vitro cytotoxicity analysis. In-vivo T1-and T2-weighted acquisitions at 60-min post-injection of 11-nm cubic SPIONs result in 64% and 48% contrast enhancement on the T1-and T2-weighted images, respectively. By controlling the shape and size of SPIONs, we have introduced a new class of cubic SPIONs as a synergistic (dual-mode) MRI contrast agent. 11-nm cubic SPIONs with smaller size and high positive and negative contrast enhancements were selected as a promising candidate for dual-mode contrast agent. Our proof-of-concept MRI experiments on rat demonstrate the in-vivo dual-mode contrast enhancement feasibility of these nanoparticles.Item Open Access Wireless deep-subwavelength metamaterial enabling sub-mm resolution magnetic resonance imaging(Elsevier, 2018) Gökyar, Sayım; Alipour, Akbar; Ünal, Emre; Atalar, Ergin; Demir, Hilmi VolkanA wireless deep-subwavelength metamaterial architecture is proposed, modeled and demonstrated for a high-resolution magnetic resonance imaging (HR-MRI) application that is miniaturized to be resonant at approximately λ0/1500 dimensions. The proposed structure has the adjustable resonance frequency from 65 MHz to 5.5 GHz for the sub-cm footprint area (8 mm × 8 mm for this study) and provides a quality factor (Q-factor) of approximately 80 in free space for 123 MHz of operation. This structure consists of a cross-via metallized partial-double-layer metamaterial, sandwiching a dielectric thin film; this structure strongly localizes the electric field in this film and has a highly capacitive metal overlay that allows for a wide range of frequency adjustment. Although the achieved resonance frequencies enable a large number of applications, as a proof-of-concept demonstration, we experimentally showed the operation of this wireless metastructure in HR-MRI to highlight its precise frequency adjustment and signal-to-noise-ratio (SNR) improvement capabilities. The proposed metamaterial was found to maintains high Q-factors despite loading with a body-mimicking lossy phantom. The experimental results indicated that the proposed metastructure can be used as an SNR-enhancing device offering 15-fold SNR enhancements that allows for imaging of objects as small as 200 μm in diameter in its vicinity, at an unprecedented level of resolution at the given DC field using standard head coils. As a result of its deep-subwavelength miniaturization accompanied by reasonable Q-factor with outstanding resonance frequency adjustment capability, this class of metastructure is proved to be an excellent candidate for in vivo medical applications.Item Open Access Wireless thin-film microwave resonators for sensing and marking(2017-05) Alipour, AkbarRapid progress in wireless microwave technology has attracted increasing interest for high-performance wireless devices. The thin- lm microwave technology is now evolving into the mainstream of applications but signi cant advances are required in resonator architectures and processing for operation in the desired frequency ranges. This dissertation studies the thin- lm microwave technology to develop wireless resonators and describes the core elements that give rise to resonators for high performance in wireless sensing and marking. Speci c to wireless sensing, we proposed and developed a novel wireless microwave resonator scheme that enables telemetric strain sensing avoiding the need for calibration at di erent interrogation distances. In this work, we showed that by using both the proposed sensor architecture and wireless measurement method, strain can be successfully extracted independent of the interrogation distance for the rst time. The experimental results indicate high sensitivity and linearity for the proposed system. This approach enables mobile wireless sensing with varying interrogation distance. For wireless marking, we investigated an ultra-thin, exible, passive radio frequency (RF) based resonator compatible with magnetic resonance imaging (MRI) that successfully was tested in clinic. The ultra-thin and exible architecture of the device o ers an e ective and safe MR visualization and improves the feasibility and reliability of anatomic marking at various surfaces of the body. Results show that, at low background ip angles, the proposed structure enables precise and rapid visibility with high marker-to-background contrast as well as high signal-to-noise ratio (SNR). Also clinical studies have led to a successful biopsy procedure using marking functionality of our device. In another work related to marking, we proposed a new method to enhance local SNR and resolution without disturbing the B1- eld. Here we used our passive RF resonator in the inductively uncoupled mode for endocavity MR imaging. T1- and T2-weighted sequences were employed for phantom and in vivo experiments. The obtained images show the feasibility of the proposed technique to improve the SNR and the resolution in the vicinity of the device. These ndings will allow for new possibilities in applications using wireless sensing and marking approaches shown in this thesis.