Surface-supported single atoms with long magnetic lifetime, also called single atom magnets, represent the ultimate limit of downscaling of a magnetic bit. Due to the possibility to write, store and read information in their magnetic states, these atoms are model systems for future ultra-high-density magnetic storage devices. In this review, the properties of the most investigated single atom magnet, namely a Ho atom adsorbed on an ultrathin MgO film, will be presented together with the techniques used to address its quantum level structure and magnetic stability. The temperature and field dependent relaxation mechanisms of this unconventional magnetic system will be discussed based on recent findings. Finally, an overview of the open issues and possible future directions of the research will be provided.

Structural and magnetic properties of Sc-substituted cobalt ferrites were studied by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and vibrating-sample magnetometry. The Sc_xCoFe_2-xO₄ (x ≤ 0.3) specimens prepared as thin films by a sol-gel deposition method were polycrystalline having cubic spinel structure with a small increase in the lattice constant compared to CoFe₂O₄ . The Raman spectral analyses suggested that the Sc-doped specimens have higher tetrahedral Co²⁺ population than that of pristine CoFe₂O₄ . The magnetic hysteresis curves of the Sc_xCoFe_2-xO₄ specimens indicated that the saturation and remanent magnetization decrease proportionally with the increase of Sc composition (x). The decrease in the ferrimagnetic parameters is understandable in terms of the octahedral substitution of non-magnetic Sc³⁺ ions. However, the octahedral Sc³⁺ ions caused an increase of the coercivity.

Magnetic bubbles are circular magnetic domains that may occur in thin magnetic films with perpendicular magnetic anisotropy (PMA). Because they can form with high topological stability and can be manipulated by external driving forces, magnetic bubbles have been considered as prominent information carriers, which are set to 1 or 0, corresponding to the presence or absence. For practical applications, such information carriers must be written and deleted in a specific area of the magnetic thin film. Herein, we report that the magnetic bubbles can be written and deleted using local magnetic fields. By applying a localized magnetic field from the magnetic tip of a magnetic force microscopy to the stripe domain structures of the PMA multilayer, bubbles can be written at room temperature via the transformation from stripe domains to magnetic bubbles. The deleting of the bubbles in the targeted area demonstrated by the local magnetic field accompanied by a uniform external field. Our findings can provide a key for manipulating information carriers in the spintronic device based on topological magnetic structures such as magnetic skyrmions and bubbles.

The present study aims to evaluate PET quantification for the fluoro deoxy glucose (FDG) brain PET images using two MR attenuation maps by comparing them with images using CT attenuation map in a healthy volunteer. The two MR attenuation maps include four segments of the Dixon sequence (soft tissue, fat, lung, and air), and five segmentations of the Dixon based bone model (soft tissue, fat, lung, air, and bone). Quantifications of the standardized uptake values (SUVs) for 133 regions of FDG brain PET images using voxel wise analyses revealed significant differences between CT and Dixon AC (mean difference = −0.93 ± 0.25). However, applying the Dixon based bone model AC reduced the estimation error compared with CTAC (mean difference = −0.66 ± 0.21). An attenuation map including bone information using the Dixon based bone model can reduce underestimation of SUV compared to Dixon from brain PET/MR imaging. In particular, errors were decreased more in the near skull regions than in central regions.

SmCo₅ is well known for its high coercivity. However, still room is available to increase the coercive power of SmCo₅, since the theoretical values of the compound is far higher than the achieved values. Different attempts, in this regard, have been made either by controlling the microstructure or the chemical composition. However, it is noted that no or very few literature is available regarding the control of microstructure through solidification. Three types of SmCo₅ compound were prepared through induction melting technique so that final solidification be manipulated by controlling the mold temperature. Fractrographic analysis revealed a unique peritectic structure in SmCo₅ compound. It was observed that the peritectic plates, having nano-size thickness, remain present even after high temperature sintering operation. The nano-scale peritectic plates may affect the final magnetic properties, especially the coercivity of the subject compound.

This paper deals with comparative investigation on permanent magnet synchronous machines (PMSMs) with identical stator structure based on electromagnetic field analysis. By considering their rotor types with rareearth magnets, the influence of space vector pulse width modulation inverter on machine performance is investigated based on the predicted phase current. As analysis models, a surface-mounted PMSM (SPMSM) with parallel magnetization, a SPMSM with Halbach magnetization, and an interior PMSM (IPMSM) are employed for their comparison. For their effective investigation, machines are designed to have identical equivalent circuit parameters, such as resistance and induced voltage in no-load condition. Based on the dynamic modeling of the SVPWM inverter, the phase current is predicted, and their output characteristic, power losses and radial force density are comparatively investigated by electromagnetic field analysis. In addition, with a manufactured machine, the validity of this paper is demonstrated as well.

This paper presents the magnetic flux density and cogging torque calculation of a surface permanent magnet synchronous machines. We obtained analytical magnetic field solutions produced by permanent magnets based on the magnetic vector potential. Then, the analytical solutions for cogging torque were obtained. All analytical results were validated with two-dimensional finite element analysis and experimental results.

Permanent magnets are currently attracting much attention as they are used in various application devices requiring high magnetic force. There are many types of permanent magnets with different properties, and they need to be tested for suitability for the applied devices. Sintered NdFeB permanent magnets have a large coercive force and are used in a variety of application systems. In particular, they are being used in circuit breakers to protect the DC transmission and distribution systems, which are actively being developed now. DC maintains a constant current value because it does not have a frequency. Thus, it is very difficult to interrupt large transient currents when an accident occurs. Therefore, a new type of induction needle and a permanent magnet near a mechanical break contact were combined. This induction needle is serially connected to a ground wire. This new breaking technique extinguishes the arch that occurs between the contacts by pushing it to the ground using an induction needle. The permanent magnet applied here, however, must be strong against a high-temperature arc that occurs quickly, and must generate a high magnetic force. Simulations were conducted with FEM (finite element method) and TDM (time difference method) using Maxwell, an electronic analysis program, and a permanent magnet that is appropriate for use as a component of a circuit breaker was selected. Consequently, it was found that the use conditions of permanent magnets varied by the arch generated in the mechanical circuit breaker.

The magnetic properties and mineral composition of black burnished pottery and reddish-brown pottery with soot unearthed from Pungnaptoseong, and restored black burnished pottery were investigated to determine the black coloring mechanism and firing condition. Results indicate that an increase in the amount of magnetic iron oxide (especially Fe3O4) by the thermal reduction reaction of hematite influences the development of black color on the surface. Furthermore, for each sample, the black surface was determined to contain the highest amount of magnetic iron oxide, followed by the black to dark gray matrix, and then the brownish matrix. These results suggested that the ancient black burnished pottery was produced by a stronger reduction reaction on the surface, as compared to the matrix during the firing process. Further, the pottery with a black to dark gray matrix was produced through intense and prolonged reduction firing, compared to the pottery with a brownish matrix.

This paper investigates the complete performance impact analysis of Synchronous Reluctance Motor (SynRM) designed for an electric Auto Rickshaw application. Here, different magnetic core steel grades are used for the same motor geometry with the TLA rotor. As it is an electric traction application, proper operation of the motor under various operating specifications is critical. Therefore, a thorough study is conducted using the finite-element method combined with an experiment-based magnetic material model at rated speed. Based on the magnetization and hysteresis characteristics of the steel sheets, variations on the performance indexes such as the average torques, torque ripples, and iron losses by using a different stator and rotor materials are investigated. Some valuable comparison results are provided through simulation and experimental validation results are shown with a prototype built.

The effects of alternating magnetic field (AMF) stimulation on the proliferation of human liver cancer cells (HepG2) under varying frequencies from 500 Hz to 2 kHz were investigated. The AMF stimulator generated a magnetic field of 5 mT with a saw tooth pulse waveform, the frequency of alternating pulses was controlled by the duty factor of the digital control circuit. HepG2 cells were cultured in a 6-well plate over a magnetic coil using a cooling system while been kept for 48 hours in an incubator. After magnetic stimulation of 0.5, 1 and 2 kHz, the proliferation rates of the HepG2 cells saw almost no difference compared to liver cancer cells that were not stimulated. However, the proliferation rates at 1.4 kHz were reduced by up to 66 % compared to the non-stimulated cells. In other words, HepG2 cancer cells can be suppressed by magnetic stimulation of a certain frequency. These results are in good agreement with those from analysis of cell viability using MTT assay, a colorimetric assay used for assessing cell metabolic activity. This phenomenon of a suppression frequency may be related with various ionic flows that occur in the ion channels of cell membranes.

This study was conducted to investigate the effects of high frequency repetitive transcranial magnetic stimulation (rTMS) on spasticity and gait ability in incomplete spinal cord injury (SCI) patients. 14 subjects were randomly assigned to each of 7 experimental and control groups. 20 Hz high frequency rTMS was applied to the experimental group for 20 minutes per day, 5 times a week for a total of 4 weeks and sham rTMS was applied to the control group. The subjects were assessed for spasticity by Modified Ashworth Scale (MAS) and Spinal Cord Injury Assessment Tool for Spasticity (SCATS). In the evaluation of gait ability, 10 Meter Walk Test (10MWT) for gait speed and Community walk test (CWT) for ability of community ambulation were used. A significant improvement in MAS, SCATS, 10MWT and CWT was observed after intervention in the experimental group (p < 0.05), and there was a significant improvement in all evaluation items compared to the control group (p < 0.05). The results of this study suggest that high frequency rTMS applied to primary motor cortex (M1) positively affects spasticity and gait ability in incomplete spinal cord injury patients.

In recent years, studies have been conducted to confirm the battery charge/discharge state using a magnetic resonance (MR) system. However, due to the structural characteristics of the battery, some difficulties exist in acquiring the signal. For example, because a loop coil does not coincide with the battery cell structure, non-uniform areas exist inside the cell samples, and it works as a limit to acquiring a quantitative MR signal measuring from the pack of lithium-ion batteries (LIB). In addition, the radio-frequency (RF) signals are weakened by the aluminum layer of the cell package. In this paper, we proposed a planar RF coil to obtain uniform ¹H and ⁷Li signals from this shielding-packaged battery cell in 7 Tesla (T) magnetic resonance image (MRI). To demonstrate the usefulness of the proposed planar RF coil, we designed a loop coil for ¹H and ⁷Li, a planar coil for ¹H, and a cut coil for ¹H and ⁷Li. Then the performance of each coil was compared through a bench test. The water phantom image was acquired with each coil, and the signal intensity profile and signal-to-noise ratio (SNR) were calculated and compared. The ¹H/⁷Li images and spectra of the electrolyte phantom were obtained using the cut coils, and the results were compared with the phantom.

This study aims to observe and estimate the temperature changes caused by the echo train lengths (ETLs) of fast-spin echo to ensure radiofrequency (RF)-related safety. RF-induced heating on ETL-stepped changes is evaluated using the proton resonance frequency shift (PRF) method and optic-fiber thermography (OFT). The increase in temperature caused by a clinical sequence was compared to that accumulated by the corresponding ETLs. The temperatures are similarly increased in ETLs from 10 to 30 (PRF: 0.109 ± 0.025 ℃, OFT: 0.079 ±0.009 ℃), suggesting that a large number of ETLs could be utilized at practical sites. The RF-induced heating in the clinical setting (PRF: 0.775 ± 0.069 ℃, OFT: 0.510 ± 0.015 ℃) is comparable to the estimated temperature on the ETL-stepped changes (PRF: 0.780 ℃, OFT: 0.553 ℃). These enable accelerated acquisition with a large number of ETLs to be practically used and RF-induced safety to be thoroughly guaranteed.

Cobalt doped magnetite Co²⁺_0.1Fe²⁺_0.9Fe³⁺₂O₄ nanocrystals were synthesized chemically using simple one step coprecipitation in the absence and presence of the magnetic field. The nanocrystals were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), magnetization studies by vibrational spectroscopy magnetometer (VSM). The signal intensity of the prepared nanoparticles was measured by magnetic resonance imaging (MRI). The cytotoxicity of the two samples versus W138 normal lung cells and AS49 lung cancer cells was investigated by MTT assay, in vitro. The TEM images showed non-spherical and aggregated nanoparticles, heterogeneously dispersed with 100 nm average size. The XRD and selected area electron diffraction of the two samples revealed good crystallinity for both samples. The room temperature magnetization curves demonstrate the general ferrimagnetic trend with a clear difference in the coercivity and the remanence keeping the saturation magnetization nearly stable. The measured MR signal intensity was well-matched with the result of the M-H loops where the sample prepared in the absence of the field was a promising T2 contrast agent. Both samples have low cytotoxicity compared to Doxorubicin.

In this study, we present a transmission-line design based on the concept of composed right- and left-hand microstrip (CRLHTL) that is able to produce a uniform B₁ field at five different frequencies. The design uses the same conductor line for all five frequencies, and maintains a uniform field along the Z axis. The CRLH concept is used to ensure that the line is operating with a uniform propagation constant in a lossless scenario. We performed electromagnetic simulations to validate the design.

As the main transportation mode of oil and gas, oil and gas pipelines play an irreplaceable role in energy transportation. Metal magnetic memory detection technology can detect early stress concentration and invisible damage, and can be detected under the action of the geomagnetic field, without the need to magnetize the pipeline in advance. Since the magnetic memory signal is relatively weak, the actual detected signal will be affected by environmental noise, sensor jitter, and pipeline surface deposits. Therefore, the magnetic memory signal needs to be denoised. In this paper, the translation invariant wavelet denoising method, which is improved based on wavelet threshold denoising method, is used to denoise the collected pipeline magnetic memory signals. The experimental results show that the signal-to-noise ratio (SNR) obtained by this method is 4.97 % higher than the unmodified wavelet threshold denoising, and 3.18 % higher than the SNR obtained by the particle swarm optimization wavelet threshold denoising

First author

Abstract: This paper study the hybrid nanofluid flow over a stretching sheet with additional effect of Wu’s slip. Comparative study of four different hybrid nanofluids is done here. We have considered manganese zinc ferrite NnZnFe2O4, Nickle zinc ferrite NiZnFe2O4 as nanoparticles whereas Kerosene oil C10H22 and Engine oil C8H18 as base fluids. Darcy Forchheimer porous medium is considered in momentum equation. Heat equation is studied in presence of different effects namely radiation, convective condition, temperature dependent heat source sink and viscous dissipation. Transformations are applied on PDE’s to form the governing equation of ODE’s. Shooting method technique is used to solve the governing equations. Velocity, temperature, Nusselt number and skin friction behaviour against different parameters is analyzed via graphs. Velocity of the fluid decays for higher slip parameter. Motion of the fluid increases for greater values of Forchheimer number. Temperature is increasing function of Biot number.

The radiomics based on positron emission tomography (PET) data and random forest can predict overall survival rate of head and neck squamous cell carcinoma (HNSCC). We used the texture features extracted from PET and clinical information from patients with HNSCC (n = 138). The Spearman's correlation analysis, Kaplan-Meier log rank test and random forest were used for survival significance and to predict survival rate of patients with HNSCC. Zone Length Non-Uniformity (ZLNU) was defined as a new key radiomics feature to predict survival rate. For stage N2 group, predicted survival rate was 76.2 % and actual survival rate was 73.3 %. For stage IVA group, predicted survival rate was 74.7 % and actual survival rate was 73.8 %. The result of this study that applications of ¹⁸F-(FDG)-PET images using radiomics features was validated and could be expected to be used as the basis for future research using MRI images with more distinct structures.

The purpose of this study was to evaluate the T1 relaxation times to distinguish between media with different contrast agent molarities (0.5 mmol/mL and 1.0 mmol/mL) for different magnetic field strengths (1.5 T and 3.0 T) in magnetic resonance imaging. Herein, we used the T1 mapping technique instead of signal intensities for evaluation. The T1 times were shorter for higher molarities at the same magnetic field strength (p = 0.043); however, there were no significant distinctions for the same molarity at different magnetic field strengths. Therate of change of the T1 duration for half the molarity of the phantom concentration was higher at low concentrations of the contrast agent. Therefore, the results indicate that higher concentrations of the contrast agent may not be necessary to obtain better imaging contrast.

Photon-counting detectors (PCDs) are replacing energy integrating detectors in electromagnetic wave transmission imaging to achieve high performance. The purpose of this study was to develop an indirect PCD system for transmission imaging. The detector module is a combination of scintillator and SiPM, the SiPM is insensitive to magnetic field and operating at low voltage. A 2D array of a GAGG coupled with SiPM, positioning logic circuit, and preamplifier were enclosed in housing that sealed from light. A channel reduction circuit was used to identify the channel from the positioning logic circuit, and then output an analog pulse signal corresponding to the valid channel. The pulse signal measurements were performed using a oscilloscope. The profile analysis of the flood map confirmed that each point was distinct in both the center and peripheral regions. Additionally, the letters engraved on the phantom in the images were confirmed. Therefore, the indirect PCD system has potential for transmission imaging. Our future work will design an indirect PCD for low-energy photon detection and multi-energy imaging.

The purpose of this study is to use a Monte Carlo simulation to derive optimal values for collimator design variables and to produce an optimized collimator for a gamma camera using a 3D printing direct metal laser sintering (DMLS) technique. For the optimization studies, GATE (Geant4 application for tomographic emission) simulation was used, and we tested lead, tungsten, and a full absorber. A total of 15 design variables were simulated using hole sizes of 0.5 mm, 0.7 mm, and 1.0 mm and slat heights from 10 mm to 20 mm at intervals of 2.5 mm. The scintillator used GAGG (gadolinium aluminum gallium garnet) and was set to a size of 25.8 × 25.8 mm². The radiation of the source used in the simulation was 37 MBq, and the source was a 140 keV point source. To obtain the diverging collimator optimization design variables, the point source was detected and an image was acquired to analyze the sensitivity and spatial resolution values. As a result, tungsten, which has good hardness, was used. If the source is located in the center of the diverging collimator, the FWHM is limited to 3.0 mm or less. The optimization value is obtained by considering the permeability, sensitivity, and spatial resolution at a height of 15 mm or higher. The results obtained by moving the source were also similar to those obtained when the source was located at the center. Based on the values of the optimized design variables, this study designed and produced a collimator using DMLS, which is a 3D printing technique. We believe this process can be applied in various fields, such as medical and industrial sectors; optimized collimators can be produced for different purposes while maintaining high precision.

To implement dual-energy cone-beam computed tomography (CBCT), a 1 to 3 mm thick copper filter was applied in front of the kilovolt generator mounted on a medical linear accelerator. The energy calibration was performed from three energy peaks among the electromagnetic radiation, gamma rays, emitted by the ¹⁹²Ir source. The energy spectrum was measured using a cadmium zinc telluride (CZT) detector. A figure-of-merit(FOM) value was defined and evaluated in order to consider both the increase in the mean energy and the decrease in the intensity according to the filter. For a 1 mm thick filter, the FOM values were 0.82 and 0.92 for tube voltages of 100 and 120 kVp, respectively. The intens ity was maintained reasonably and the effect of increasing the mean energy was evident, thus indicating its suitability for implementing dual-energy CBCT.

Tooth bleaching gel, that comes in direct contact with the tooth surface for a long time, affects hard dental tissue. Nonthermal plasma consists electrons, ions, charged particles, electric filed and magnetic field. The motion of an electrically charged particle such as electron and ion can generate both electric and magnetic field. This study was conducted to investigate how tooth bleaching with 15 % hydrogen peroxide (HP) and plasma (from electric currents and magnetic fields) affects hard dental tissue. Extracted human teeth were treated with 15 % HP, with and without plasma. We fabricated a 15 % HP gel with neutral pH, and applied the gel and plasma to tooth surfaces for 30 minutes. The overall color change following 15 % HP gel and plasma was higher than in the other groups, and there were no significant changes in microhardness or mineral contents. Application of 15 % HP and plasma showed a bleaching high effect, with no damage to hard dental tissue. Even though 15 % HP has adverse effects, results can be effective without danger if treatment times are kept short.

A hybrid multiplexer readout circuit one dimensional resistive charge division (1D-RCD) chain and winner takes all (WTA) circuit was proposed for MR-compatible PET detector modules. To prove the effectiveness of the circuit, three different readout circuits including WTA, 2D-RCD and proposed hybrid RCD-WTA multiplexer were evaluated for 4 × 4 LYSO-GAPD PET detector. Various parameters were precisely measured and quantitatively characterized. While there were considerable differences observed in rise time, fall time, pulse width and amplitude of analog output waveforms for each circuit, the detector performance was quite similar in crystal identification and energy resolution. However, pincushion distortion was observed in the flood histogram of 2D-RCD, and spatial linearity was relatively degraded. The coincidence time resolutions were 487 ps, 955 ps, and 676 ps for WTA, 2D-RCD, and hybrid RCD-WTA multiplexer, respectively. These results demonstrated that proposed hybrid multiplexer could effectively reduce the number of analog electronic channels from N² to only 2 for an N × N photosensor array, while maintaining intrinsic performance of multichannel PET detector requiring energy, position and time information for incidence photons.

Recently, deep learning (DL) based semantic segmentation approach has been widely applied in medical image analysis. The semantic segmentation approach based DL technique was employed in the diagnosis of dentalconditions with digital panoramic radiography (DRP). The purpose of this study is to investigate the accuracy of the semantic segmentation of Deeplab v3+ in the diagnosis of 5 different dental disease - apical, abrasion, caries, impaction, perio. DPR database (512×748-pixel, including 86 panoramic radiography) was used for semantic segmentation (DeepLab v3+). To validate the performance, the confusion matrix (maximum 97 %) was estimated. In addition, significant classification and semantic segmentation results were assessed. From the result of this study, the DL model could be a useful tool for the dentist to identify dental diseases as a clinical aid software.

Magnetic resonance imaging (MRI) shows high contrast and resolution on the soft tissues and nervous tissues without radiation hazard, which is used as an essential diagnostic test in the radiology. Cross excitation meansto show artifacts upon the signal loss from overlapped radio frequency (RF) in some anatomical locations during the image acquisition process with RF pulse. To lower cross excitation artifacts, their images wereanalyzed by the changes of flip angle, TR, and TE. Ingenia 3.0T CX MRI by Philips was used for image acquisition. Self-developed water phantom used for quality control of MRI was used. SNR values at 40 degreeof flip angle were 1,354 ±7.12 and 214 ± 2.10; those at 70 degree were 1,375 ± 7.31 and 305 ± 2.12; and those at 90 degree were 1,413 ± 7.93 and 357 ± 2.33, for water and artifact, respectively. CNR values were 1,140 ± 7.01,1,070 ± 7.18, and 1,056 ± 7.12 at 40, 70 and 90 degree of flip angle, respectively (P < 0.05). As flip angle was lowered more, artifact was decreased more. In case of 90 degree of flip angle, artifact was decreased more asTR was longer. These results are anticipated to be used as the fundamental data to acquire more valued medical images in terms of diagnostics with MRI to diagnose various diseases.

The demand in medical field for Mobile Computed Tomography in high-energy electromagnetic area is exploding. To measure the distribution of exposure doses in abdomen inspection, this study placed 2 glass dosimeter elements on the entry point and exit point, respectively, 2-3 cm above the navel, the central point of abdominal inspection, and measured exposure doses in different parts. And, to reduce measurement errors, MDCT scanning was done 5 times. Acquired images were analyzed qualitatively to identify usefulness in medical treatment. Qualitative analysis of images was done about image contrast, lesion discovery rate, and clarity of border. Five specialists (2 medical doctors specializing radiology and 3 radiologists with working experiences over 10 years) were asked to classify the results on the 5-point scale (1 - very poor; 2 - poor; 3 - average; 4 - good; 5 - very good). In skull CT scanning, exposure doses measured with glass dosimeter were as follows: 21.4 ± 0.43 mGy by 4-MDCT; 13.7 ± 0.43 mGy by 128-MDCT; 5.02 ± 0.19 by Mobile CT, which shows that Mobile CT requires relatively lower dose to get meaningful images in diagnosis (P < 0.05). In skull CT scanning, the images acquired from MDCT and Mobile CT were graded on the 5-point Likert scale: 4-MDCT images got 3.50 point; 128-MDCT images got 4.43 point; Mobile CT images got 4.21 point. The 128-MDCT got the highest point, followed by 4-MDCT and Mobile CT. The difference was statistically significant (P < 0.05). The above findings show that Mobile CT is good for getting high-quality image and reducing radiation exposure doses. It seems that more hospitals will use Mobile CT.

Dental erosion is the irreversible loss of dental hard tissue by acids not by bacteria. The prevalence rate of dental erosion is on the rise these days, and the consumption of acidic beverages is recognized as one of the main risk factors. Therefore, in this study, pH of certain commercial fruit juices was measured to determine whether they cause enamel corrosion of teeth, and the changes in calcium (Ca) and phosphorous (P) were evaluated by quantitative analysis using energy dispersive X-ray spectroscopy (EDS). As the pH decreased, the solubility of Ca increased, and as the exposure time increased, the loss of Ca was greater. Ingestion of fruit juice with a low pH affects the risk of dental erosion, and the retention time of the juice in oral cavity should be shortened as long-term contact with the juice may cause the tooth damage.

With the recent advancement of artificial intelligence (AI), data-based research is being actively conducted in the dental medical field. However, there is a limited amoun of research yet based on algorithms using panoramic radiography. This study was conducted to find the standard AI reading that distinguishes the young from the elderly using panoramic radiographic images, and to confirm the applicability of the method as a means of increasing the reliability of a diagnosis. A total of 117 panoramas in A dental clinic were used. The selected radiographic images were classified into two groups: the old group and the young group. To load the classified images into the suggested and designed multi-layer neural network model (modified DarkNet), they were split into 70 % training data and 30 % testing data using the ‘SplitEachLable()’ Matlab function. To identify the old group, the focal class activation mapping or CAM (the height of the alveolar bone and the major places where other treatment actions took place) area was estimated. To identify the young group, a wide CAM area over the entire area was estimated as a feature. These data could be important quantitative indicators ofthe health of the alveolar bone and of the overall dental condition. Significant results and features were derived to show the potential of quantitative indicators for dental care. The results of this study confirmed the possibility of estimating the alveolar bone age based on AI.

The purpose of this study is to analyze the accuracy of digital dental models acquired using cone beam computed tomography (CBCT), an electromagnetic wave method. While there are many reports comparing CBCT and intra oral scanners, there are few comparative studies on the accuracy of different digital dental models acquired using CBCT. Targeting this problem, in this study, we tried to analyze the accuracy of dental prosthesis data generated by different CBCT models with 3D computer programs. To this end, a single preparation dental model, 3-unit bridge dental model, and full dental model were selected and photographed using CBCT to obtain a DICOM file, which was later converted into an STL file. The converted STL file was analyzed qualitatively and quantitatively for trueness and precision using a 3D superimposition program. Although there were statistically significant differences in the trueness values of the three digital dental models (P < 0.05), no significant differences could be observed in the precision values (P > 0.05). In conclusion, using CBCT-based dental models, it may be difficult to fabricate dental prosthesis due to a distortion between the rounded part of the tooth, the prepared tooth, and adjacent teeth. However, if the accuracy of sharpness in CBCT images can be increased, in the future, this method may be employed to manufacture dental prosthesis for clinical applications.

We developed a depth of interaction (DOI) detector for positron emission tomography (PET) using different kinds of reflectors. The detector module consists of two layers of scintillator arrays, which was composed of 4 × 4 Gadolinium Aluminum Gallium Garnet (GAGG) crystals of size 3 mm × 3 mm × 10 mm, and 4 × 4 silicon photomultiplier (SiPM) arrays. The bottom layer optically coupled to the SiPM used a diffuse reflector and the top layer used a specular reflector. The layer interacted with gamma ray and crystal could be determined by analyzing the signal size because it obtained for each layer is different by using different reflectors for the crystals for each layer. The detector performance was analyzed by the flood image, energy spectrum with two photoelectric peaks, and energy resolution. In the experiment for the detector module performance, all pixels in the flood map were well decoded, and the energy spectrum of each pixel is measured with two photo peaks.

Recently, there have been several physics and clinical studies on the use of lower tube potentials in CT imaging, with the purpose of improving image quality or further reducing radiation dose. We investigated an experimental study using a series of different sized, polymethyl methacrylate (PMMA) phantoms, demonstrating the potential strategy for dose reduction and to distinguish component of plaque by imaging their energy responses using CT. We investigated the relationship between different sizes of cylinderic PMMA equivalent phantoms with diameter of 12, 16, 20, 24, and 32 cm and used contrast at various tube voltages (80, 100, 120, and 140 kVp) using a 16–detector row CT scanner. The contrast represented CT numbers as different materials for the water, calcium chloride, and iodine. Phantom insertions also allow quantitative measures of image noise, contrast, contrast-to-noise ratio (CNR) and figure of merit (FOM). When evaluating FOM, it was found that the lower kVp provided the better CNR. An experimental study was performed to demonstrate reduced dose for both dose efficient and practical feasibility for different patient sizes and diagnostic tasks by relating achievable CNR and the volume CT dose index (CTDI vol). The use of spectra optimized to the specific application could provide further improvements of distinguishing iodine, calcium and plaque component for patient size. The purpose of this study was to evaluate variations in image noise and contrast using different tube potentials in a CTDI phantom on contrast imaging.

The paper was to find out effects of cerebral motor excitability and hand dexterity used to 1 Hz low frequency repetitive transcranial magnetic stimulation (rTMS) combined with hand manual therapy (HMT) on dominant hand difference in chronic stroke patients. 16 stroke patients were classified into the dominant hand HMT with r TMS group (DHMT+rTMSG) and non-dominant hand HMT with rTMS group (NDHMT+rTMSG), and 1 Hz low-frequency rTMS with HMT was performed. Motor evoked potentials (MEPs) amplitude, latency and box and block test (BBT) were used to confirm cerebral motor activity and hand dexterity. In DHMT+rTMSG, MEPs amplitude, latency and BBT showed significant differences. In NDHMT+rTMSG, MEPs amplitude, latency only showing significant difference. In the comparison between groups, MEPs amplitude, latency showed significant difference. Therefore, the 1 Hz low frequency rTMS combined with HMT according to the dominant hand difference is considered to be an n approach applied in the recovery of hand function in stroke.

A depth of interaction detector was designed using three layers of the scintillation pixel array and silicon photomultiplier through DETECT2000 simulation. The upper and lower layers used diffuse reflectors, and the middle layer used specular reflectors to distinguish the light signal arising from each layer. The signals obtained at each layer were characterized by different locations at which photoelectric peaks were formed in the energy spectrum, which could be analyzed to track the layers in which gamma-rays and scintillation pixels interacted. Based on the simulation results, the basic experiment was conducted to obtain the energy spectrum. In the experiment, three photoelectric peaks were identified in the energy spectrum as in the simulation, and the layers interacted with gamma-rays, and scintillation pixels for each layer were distinguished by analyzing each photoelectric peak. It is anticipated that by applying the detector design obtained from this study to future small animal PET operating with MRI, the depth at which gamma-rays and scintillators interact will be measurable, thus improving the spatial resolution outside the FOV.

The paper was to investigate the effects of a combination of 10-Hz high-frequency repetitive transcranial magnetic stimulation (rTMS) and somatosensory training (SST) on upper limb motor and hand function in chronic stroke patients. Upper limb motor and hand function were evaluated using Fugl-Meyer assessment (FMA), manual functions test (MFT), and pinch, grasping strength. The results revealed that there was a significant difference in FMA and MFT before and after the SST after 10-Hz high-frequency rTMS (p<0.05). The experimental group showed a significant improvement in FMA and pinch strength compared to the control group (p<0.05). There was no significant improvement between MFT and grasping strength between the groups (p>0.05). Thus, 10-Hz high-frequency rTMS, combined with SST, can be considered to be an effective treatment for the recovery of upper limb motor and hand function in chronic stroke patients.

This paper was presented at the IcAUMS2018, Jeju, Korea, June 3-7, 2018.