Application Of Tomography Imaging Research Articles

Synthesis and Properties of Ag‐Au Alloy Nanoparticles with Controlled Composition for Computed Tomography Imaging Applications

AbstractNumerous non‐invasive assays have been developed to support CT imaging, consequently increasing the precision of diagnosis. Although these efforts made a significant contribution to clinical research, there is still more to be done. The goal is to replace conventional contrast agents with more potent ones. In this study, Ag−Au alloy nanoparticles were fabricated by substitution method between the precursor Au3+ and the previously prepared Ag nanoparticles. Effects of Au3+ quantity on the formation and characteristics of Ag−Au alloy nanoparticles were investigated. It showed that Ag−Au nanoalloy with a size of 14.2±1.0 nm, SPR absorption peak at 520 nm, and Ag: Au atomic ratio of approximately 3 : 1 were appropriate for biomedical applications. After phase transfer using poly (maleic anhydride‐alt‐1‐octadecene) (PMAO), the nano Ag−Au solution owned remarkable durability, stability and non‐toxicity Vero healthy cell line at high test concentration. In‐vitro CT imaging demonstrated a good X‐ray adsorption coefficient, and the hounsfield units (HU) was noticeably increased. As a promising CT contrast agent, the X‐ray attenuation of nano Ag−Au solutions correlated linearly with concentrations. These findings led to a potential application in the biomedical field, particularly in computed tomography (CT) imaging diagnosis.

De Novo Approaches to the Solid-Phase Separation of Titanium(IV) and Scandium(III): Translating Speciation Data to Selective On-Bead Chelation toward Applications in Nuclear Medicine.

The solution chemistry of the hydrolytic, early-transition-metal ions Ti4+ and Sc3+ represents a coordination chemistry challenge with important real-world implications, specifically in the context of 44Ti/44Sc and 45Ti/NatSc radiochemical separations. Unclear speciation of the solid and solution phases and tertiary mixtures of mineral acid, organic chelators, and solid supports are common confounds, necessitating tedious screening of multiple variables. Herein we describe how thermodynamic speciation data in solution informs the design of new solid-phase chelation approaches enabling separations of Ti4+ and Sc3+. The ligands catechol (benzene-1,2-diol) and deferiprone [3-hydroxy-1,2-dimethyl-4(1H)-pyridone] bind Ti4+ at significantly more acidic conditions (2-4 pH units) than Sc3+. Four chelating resins were synthesized using either catechol or deferiprone with two different solid supports. Of these, deferiprone appended to carboxylic acid polymer-functionalized silica (CA-Def) resin exhibited excellent binding affinity for Ti4+ across a wide range of HCl concentrations (1.0-0.001 M), whereas Sc3+ was only retained in dilute acidic conditions (0.01-0.001 M HCl). CA-Def resin produced separation factors of >100 (Ti/Sc) in 0.1-0.4 M HCl, and the corresponding Kd values (>1000) show strong retention of Ti4+. A model 44Ti/44Sc generator was produced, showing 65 ± 3% yield of 44Sc in 200 μL of 0.2 M HCl with a significant 44Ti breakthrough of 0.1%, precluding use in its current form. Attempts, however, removed natSc in loading fractions and a dilute (0.4 M HCl) wash and recovered 80% of the loaded 45Ti activity in 400 μL of 6 M HCl. The previously validated 45Ti chelator TREN-CAM was used for comparative proof-of-concept reactions with the CA-Def eluent (in HCl) and literature-reported hydroxamate-based resin eluents (in citric acid). CA-Def shows improved radiolabeling efficiency with an apparent molar activity (AMA) of 0.177 mCi nmol-1, exceeding the established methods (0.026 mCi nmol-1) and improving the separation and recovery of 45Ti for positron emission tomography imaging applications.

Neutral Ligands as Potential 64Cu Chelators for Positron Emission Tomography Imaging Applications in Alzheimer's Disease.

Positron emission tomography (PET), which uses positron-emitting radionuclides to visualize and measure processes in the human body, is a useful noninvasive diagnostic tool for Alzheimer's disease (AD). The development of longer-lived radiolabeled compounds is essential for further expansion of the use of PET imaging in healthcare, and diagnostic agents employing longer-lived radionuclides such as 64Cu (t1/2 = 12.7 h, β+ = 17%, β- = 39%, electron capture EC = 43%, and Emax = 0.656 MeV) can accomplish this task. One limitation of 64Cu PET agents for neuroimaging applications is their limited lipophilicity due to the presence of several anionic groups needed to ensure strong Cu chelation. Herein, we evaluate a series of neutral chelators containing the 1,4,7-triazacyclononane or 2,11-diaza[3.3](2,6)pyridinophane macrocycles that have pyridyl-containing arms incorporating Aβ-peptide-interacting fragments. The crystal structures of the corresponding Cu complexes confirm that the pyridyl N atoms are involved in binding to Cu. Radiolabeling and autoradiography studies show that the compounds efficiently chelate 64Cu, and the resulting complexes exhibit specific binding to the amyloid plaques in the AD mouse brain sections versus wild-type controls.

New Approach to Dental Morphometric Research Based on 3D Imaging Techniques.

Recent progress in imaging and image processing techniques has provided for improvements in odontological research in a variety of aspects. Thus, the presented method has been developed precisely in order to assess metrically 3D reconstructions of teeth. Rapidly and accurately obtained data of a wide range and appropriate density are sufficient enough for morphometric studies rather than tooth size assessments which are inherent to conventional techniques. The main contributions providing for holistic and objective morphometric analysis of teeth are the following: (1) interpretation of basic dental morphological features; (2) automated of orientational coordinate system setup based on tooth surface analysis; (3) new tooth morphometric parameters which could not be obtained through application of conventional odontometric techniques; (4) methodological novelty for automated odontomorphometric analysis pipeline. Application of tomographic imaging, which has been used for obtaining 3D models, expands the proposed method potential further through providing detailed and comprehensive reconstructions of teeth. The current study was conducted on unique material from the archaeological site of Sunghir related to the Upper Palaeolithic period. Metric assessments of external and internal morphological layers of teeth were performed in common orientation and sectioning. The proposed technique allowed more profound analysis of Sunghirian teeth which date back to the times of modern human morphology formation.

Design guidelines for collimating or focusing graded-index fiber tips.

Graded-index optical fiber probes suitable for focusing or collimating the output of an optical fiber at a wavelength of 1.3 µm have become an enabling technology in optical coherence tomography imaging applications for in vivo bioimaging. Such fiber tips however remain uncommon in other photonics applications. This paper provides the first numerical study of graded-index fiber tips covering a broad range of wavelengths spanning from the UV to short-infrared. The wavelength dependency and the influence of probe geometry on performance characteristics such as far-field divergence angle, spot size and working distance are analyzed. The paper yields easily accessible design guidelines for the fabrication of collimating or focusing fiber tips. Fiber collimators have considerable potential for use in free-space systems and could benefit a range of devices such as variable attenuators, dynamic wavelength equalisers and large 3D optical cross-connect switches, whereas focusing fiber tips have applications in high-resolution imaging.

An Image Reconstruction Algorithm with Experimental Validation for Electrical Impedance Tomography Imaging Applications

In the Non-Invasive Bio Impedance Technique (NIBIT) a low current pulse with high frequency inserted between two electrodes of the object while measuring voltages from the other remaining electrodes with respect to the reference electrode. The electrode arrangement is defined in the form of cylindrical shapes of the surface of the phantom. After these arrangements, it inserts the current pulse and measures the voltages according to the selected data acquisition method of bio impedance. The presented algorithm analyzes and defines each obtained data sample from the used phantoms and also allows Image Reconstruction (IR) based on developed Graphical User interface (GUI) on MATLAB. The used IR approach is based on Tikhonov regularization and FEM. The FEM and Tikhonov regularization are mathematical approaches that deal with Forward Problem (FP) and Inverse Problem (IP) of images. In our approach, the FP solution is identified first in order to reconstruct the conductivity distribution through the EIT inverse solution. Thereafter, This FP is solved through the known current pulse of a given conductivity medium. Likewise, the IP is identified and solved through the boundary potential of the object. The end of the obtained result provides a comparable result for the used phantom according to its internal structure. This proposed technique is still reliable despite having some standardization issue according to the procedure.

Dental root development associated with treatments by rapid maxillary expansion/reverse headgear and slow maxillary expansion.

To assess dental root development in two groups of paediatric patients who received treatments with reverse headgear and rapid maxillary expansion and slow maxillary dental arch expansion. The 20 subjects (13 girls, 7 boys; mean age: 8.9 ± 1.3 years) in the first group were treated with a Petit-type reverse headgear attached to a full-coverage bonded rapid maxillary expander via elastics (RME&RHg group). The 20 subjects included in the second group (9 girls, 11 boys; mean age: 9.1 ± 2.2 years) were selected among patients who were treated with Hawley appliances for slow maxillary expansion (SME group). Digitized panoramic radiographs were used. A total of 960 permanent teeth (maxillary-mandibular incisors, canines, premolars, and first molars) were measured quantitatively for pre-treatment and post-treatment. No significant increase was found except for the right and left maxillary and mandibular second premolars and left mandibular and first premolar in the RME&RHg group (P < 0.05). Teeth length values increased significantly in all maxillary and mandibular teeth except maxillary first molars and mandibular incisors in the SME group (P < 0.05). Inter-group comparisons showed that statistically significant differences were observed in maxillary and mandibular incisors, left maxillary first premolar, and molar teeth (P > 0.05). A limitation of this study is the use of two-dimensional radiographic images for root length measurement. However, ethical obligations limit the dental cone beam computed tomography imaging application for protection of paediatric patients from harm. RME&RHg therapy inhibits root development of maxillary and mandibular teeth in the early period. However, further studies should be performed to determine whether this effect on root development is reversible or irreversible.

The correlation of computed tomography in the evaluation of septoplasty patients.

Septoplasty is one of the frequently applied nasal surgical procedures. There is still no gold standart objective method to evaluate the patients whom suffers from nasal blockage. To evaluate the septoplasty candidate with a Paranasal Computerised Tomography (PNCT) is one of the most discussed topic in the otorhinolaryngology surgical philosophy. In this study, we aim to interpret the value of nasal valve areas measured by PNCT for both septoplasty candidates and the control population. We believe that this information could be useful for the evaluation of patients before undergoing a septoplasty procedure. 600 coronal and axial tomography sections performed between May 2014 and February 2018 at the University Of Gaziantep Radiology Dept. were assessed. These tomography sections were divided into two groups called the septoplasty and the control. The septoplasty group was made up of three hundred paranasal sinus tomography images scanned before patients' septoplasty operations. The control group was created by screening 300 maxillofacial tomography's which were taken due to the suspicion of trauma at the University Of Gaziantep Emergency Clinic between May 2014 and January 2018. There were 192 (64%) patients with left nasal septal deviation and 108 (36%) patients with right nasal septal deviation. The Independent Sample T-Test revealed that the mean internal nasal valve angle in the left septoplasty group was significantly lower than that of the control group (P < 0.005). A comparison of the right side nasal values revealed a significant statistical change according to the Independent Sample T-Test between the value of the right septoplasty and the control groups (P < 0.005). The sectional areas of nasal tomography images may show different values. However, it is still difficult to say that the clinical application of tomography images could be used as one of the indication criteria for the septoplasty procedure.

Quantitative Microwave Imaging Method in Lebesgue Spaces With Nonconstant Exponents

An innovative nonlinear inverse scattering approach in variable exponent Lebesgue spaces is proposed for microwave imaging purposes. The main objective of the approach is to overcome one of the main problems associated with reconstruction procedures developed in Lebesgue spaces with constant exponent, i.e., the need for the selection of the optimum Lebesgue-space norm parameter, which is critical for obtaining accurate reconstructions, and no exact rules exist for this choice. The approach proposed in this paper is oriented to tomographic imaging applications at microwave frequencies, for which the adopted inversion procedure is based on a Gauss–Newton method, which has been reformulated in the unconventional variable exponent Lebesgue spaces. The capabilities of the approach are demonstrated by a set of numerical simulations, in which cylindrical dielectric targets are inspected. Moreover, an experimental result is reported.

Investigation of soft component in cosmic ray detection

Cosmic ray detection is a research area which finds various applications in tomographic imaging of large size objects. In such applications, the background sources which contaminate cosmic muon signal require a good understanding of the creation processes, as well as reliable simulation frameworks with high predictive power are needed. One of the main background source is the “soft component”, that is electrons and positrons. In this paper a simulation framework based on GEANT4 has been established to pin down the key features of the soft component. We have found that the electron and positron flux shows a remarkable invariance against various model parameters including the muon emission altitude or primary particle energy distribution. The correlation between simultaneously arriving particles have been quantitatively investigated, demonstrating that electrons and positrons tend to arrive within a close distance and with low relative angle. This feature, which is highly relevant for counting detectors, has been experimentally verified under open sky and at shallow depth underground. The simulation results have been compared to existing other measurements as well as other simulation programs.

Supercomputer technologies in tomographic imaging applications

Currently, tomographic imaging is widely used in medical and industrial non-destructive testing applications. X-ray tomography is the prevalent imaging technology. Modern medical X-ray CT scanners provide up to 1 mm spatial resolution. The disadvantage of X-ray tomography is that it cannot be used for regular medical examinations. Early breast cancer diagnosis is one of the most pressing issues in modern healthcare. Ultrasound tomography devices are being developed in USA, Germany and Russia to address this problem. One of the main challenges in ultrasound tomographic imaging is the development of efficient algorithms for solving inverse problems of wave tomography, which are nonlinear three-dimensional coefficient inverse problems for a hyperbolic differential equation. Solving such computationally-expensive problems requires the use of supercomputers.

Laser-wakefield accelerators as hard x-ray sources for 3D medical imaging of human bone.

A bright μm-sized source of hard synchrotron x-rays (critical energy Ecrit > 30 keV) based on the betatron oscillations of laser wakefield accelerated electrons has been developed. The potential of this source for medical imaging was demonstrated by performing micro-computed tomography of a human femoral trabecular bone sample, allowing full 3D reconstruction to a resolution below 50 μm. The use of a 1 cm long wakefield accelerator means that the length of the beamline (excluding the laser) is dominated by the x-ray imaging distances rather than the electron acceleration distances. The source possesses high peak brightness, which allows each image to be recorded with a single exposure and reduces the time required for a full tomographic scan. These properties make this an interesting laboratory source for many tomographic imaging applications.

An iterative algorithm for computed tomography image reconstruction from limited-angle projections

In application of tomography imaging, limited-angle problem is a quite practical and important issue. In this paper, an iterative reprojection-reconstruction (IRR) algorithm using a modified Papoulis-Gerchberg (PG) iterative scheme is developed for reconstruction from limited-angle projections which contain noise. The proposed algorithm has two iterative update processes, one is the extrapolation of unknown data, and the other is the modification of the known noisy observation data. And the algorithm introduces scaling factors to control the two processes, respectively. The convergence of the algorithm is guaranteed, and the method of choosing the scaling factors is given with energy constraints. The simulation result demonstrates our conclusions and indicates that the algorithm proposed in this paper can obviously improve the reconstruction quality.

Development of TOF-PET detectors based on the Multi-Gap Resistive Plate Chambers

We describe the development, construction and preliminary results obtained with medium-size Multi-Gap Resistive Plate Chambers prototypes designed to detect and localize 511keV photons for Positron Emission Tomography imaging applications. The devices are intended for in-beam monitoring of the treatment plans throughout deep tumor therapy with hadron beams; emphasis is put on achieving coincidence time resolutions of few hundred ps, in order to exploit optimized reconstruction algorithm and reduce the heavy non-correlated background contributions distinctive of this operation. Using technologies developed for high energy physics experiments, the detectors can be built for covering large areas, thus leading the way to the conception of full-body PET systems at low cost.

Ultrawideband Noise Radar Imaging of Impenetrable Cylindrical Objects Using Diffraction Tomography

Ultrawideband (UWB) waveforms achieve excellent spatial resolution for better characterization of targets in tomographic imaging applications compared to narrowband waveforms. In this paper, two-dimensional tomographic images of multiple scattering objects are successfully obtained using the diffraction tomography approach by transmitting multiple independent and identically distributed (iid) UWB random noise waveforms. The feasibility of using a random noise waveform for tomography is investigated by formulating a white Gaussian noise (WGN) model using spectral estimation. The analytical formulation of object image formation using random noise waveforms is established based on the backward scattering, and several numerical diffraction tomography simulations are performed in the spatial frequency domain to validate the analytical results by reconstructing the tomographic images of scattering objects. The final image of the object based on multiple transmitted noise waveforms is reconstructed by averaging individually formed images which compares very well with the image created using the traditional Gaussian pulse. Pixel difference-based measure is used to analyze and estimate the image quality of the final reconstructed tomographic image under various signal-to-noise ratio (SNR) conditions. Also, preliminary experiment setup and measurement results are presented to assess the validation of simulation results.

Accelerated nonlinear multichannel ultrasonic tomographic imaging using target sparseness.

This paper presents an accelerated iterative Landweber method for nonlinear ultrasonic tomographic imaging in a multiple-input multiple-output (MIMO) configuration under a sparsity constraint on the image. The proposed method introduces the emerging MIMO signal processing techniques and target sparseness constraints in the traditional computational imaging field, thus significantly improves the speed of image reconstruction compared with the conventional imaging method while producing high quality images. Using numerical examples, we demonstrate that incorporating prior knowledge about the imaging field such as target sparseness accelerates significantly the convergence of the iterative imaging method, which provides considerable benefits to real-time tomographic imaging applications.

Synthesis of PEGylated low generation dendrimer-entrapped gold nanoparticles for CT imaging applications

Dendrimer-entrapped gold nanoparticles (Au DENPs) can be formed using low-generation dendrimers pre-modified by polyethylene glycol (PEG). The formed PEGylated Au DENPs with desirable stability, cytocompatibility, and X-ray attenuation properties enable efficient computed tomography imaging of the heart and tumor model of mice.

Dendrimer-stabilized bismuth sulfide nanoparticles: synthesis, characterization, and potential computed tomography imaging applications

We report here a general approach to synthesizing dendrimer-stabilized bismuth sulfide nanoparticles (Bi2S3 DSNPs) for potential computed tomography (CT) imaging applications. In this study, ethylenediamine core glycidol hydroxyl-terminated generation 4 poly(amidoamine) dendrimers (G4.NGlyOH) were used as stabilizers to first complex the Bi(III) ions, followed by reaction with hydrogen sulfide to generate Bi2S3 DSNPs. By varying the molar ratio of Bi atom to dendrimer, stable Bi2S3 DSNPs with an average size range of 5.2-5.7 nm were formed. The formed Bi2S3 DSNPs were characterized via different techniques. X-ray absorption coefficient measurements show that the attenuation of Bi2S3 DSNPs is much higher than that of iodine-based CT contrast agent at the same molar concentration of the active element (Bi versus iodine). 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell viability assay and hemolysis assay reveal that the formed Bi2S3 DSNPs are noncytotoxic and have a negligible hemolysis effect in the studied concentration range. Furthermore, we show that cells incubated with the Bi2S3 DSNPs are able to be imaged using CT, a prominent enhancement at the point of rabbit injected subcutaneously with the Bi2S3 DSNPs is able to be visualized via CT scanning, and the mouse's pulmonary vein can be visualized via CT after intravenous injection of the Bi2S3 DSNPs. With the good biocompatibility, enhanced X-ray attenuation property, and tunable dendrimer chemistry, the designed Bi2S3 DSNPs should be able to be further functionalized, allowing them to be used as a highly efficient contrast agent for CT imaging of different biological systems.

Facile hydrothermal synthesis of low generation dendrimer-stabilized gold nanoparticles for in vivo computed tomography imaging applications

We report a facile approach to synthesizing low generation poly(amidoamine) (PAMAM) dendrimer-stabilized gold nanoparticles (Au DSNPs) for in vivo computed tomography (CT) imaging applications. In this study, amine-terminated generation 2 PAMAM dendrimers were employed as stabilizers to form gold nanoparticles via a simple hydrothermal method. The formed aminated Au DSNPs were then acetylated to neutralize the dendrimer terminal amines, rendering the particles with improved biocompatibility. The final formed acetylated Au DSNPs were characterized via different techniques. We show that the formed Au DSNPs with an Au core size of 5.6 nm are relatively uniform and stable at different pH (5–8) and temperature (4–50 °C) conditions. X-ray attenuation coefficient measurements show that the Au DSNPs display approximately the same X-ray attenuation property as that of Omnipaque, a clinically used iodinated contrast agent. Importantly, the acetylated Au DSNPs showed much better performance in CT imaging of the major organs of rats (heart, liver, kidney, spleen, and bladder) in vivo than Omnipaque, likely due to their nanometer size and thus prolonged blood circulation time. The formed Au DSNPs may be used as a promising contrast agent for CT imaging of different biological systems.

Facile formation of folic acid-modified dendrimer-stabilized gold–silver alloy nanoparticles for potential cellular computed tomography imaging applications

We report a facile approach to fabricating dendrimer-stabilized gold-silver alloy nanoparticles (Au-Ag alloy DSNPs) for targeted in vitro computed tomography (CT) imaging of cancer cells. In this study, folic acid (FA)-modified amine-terminated generation 5 poly(amidoamine) dendrimers (G5·NH2-FA) were used as stabilizers to prepare Au-Ag alloy DSNPs by simultaneously reducing both gold and silver salts, followed by acetylation of the dendrimer terminal amines. The formed Au-Ag alloy DSNPs were characterized via different techniques. We show that the formed Au-Ag alloy DSNPs are spherical in shape with a relatively narrow size distribution, have good water solubility and colloidal stability, and display higher X-ray attenuation intensity than the iodine-based contrast agent of Omnipaque at the same molar concentration of the active element (i.e., Au plus Ag, or iodine). Cytotoxicity assay results show that the Au-Ag alloy DSNPs are cytocompatible in a given concentration range. Importantly, the formed Au-Ag alloy DSNPs are able to be specifically taken up by cancer cells overexpressing FA receptors and enable targeted CT imaging of the cancer cells. Given the unique structural characteristics of dendrimers and the facile synthesis of DSNPs, the developed Au-Ag alloy DSNPs may be used for various biomedical applications in sensing, diagnosis, and therapeutics.