Full-width At Half-maximum Values Research Articles

Analytical and experimental FWHM of a gamma camera: theoretical and practical issues.

Introduction. It is well known that resolution on a gamma camera varies as a function of distance, scatter and the camera’s characteristics (collimator type, crystal thickness, intrinsic resolution etc). Manufacturers frequently provide only a few pre-calculated resolution values (using a line source in air, 10–15 cm from the collimator surface and without scattering). However, these are typically not obtained in situations resembling a clinical setting. From a diagnostic point of view, it is useful to know the expected resolution of a gamma camera at a given distance from the collimator surface for a particular setting in order to decide whether it is worth scanning patients with “small lesion” or not. When dealing with absolute quantification it is also mandatory to know precisely the expected resolution and its uncertainty in order to make appropriate corrections.Aim. Our aims are: to test a novel mathematical approach, the cubic spline interpolation, for the extraction of the full width at half maximum (FWHM) from the acquisition of a line source (experimental resolution) also considering measurement uncertainty; to compare it with the usually adopted methods such as the gaussian approach; to compare it with the theoretical resolution (analytical resolution) of a gamma camera at different distances; to create a web-based educational program with which to test these theories.Methods. Three mathematical methods (direct calculation, global interpolation using gaussian and local interpolation using splines) for calculating FWHM from a line source (planar scintigraphy) were tested and compared. A NEMA Triple Line Source Phantom was used to obtain static images both in air and with different scattering levels. An advanced, open-source software (MATLAB/Octave and PHP based) was created “ad hoc” to obtain and compare FWHM values and relative uncertainty.Results and Conclusion. Local interpolation using splines proved faster and more reliable than the usually-adopted Gaussian interpolation. The proposed freely available software proved effective in assessing both FWHM and its uncertainty.

Adaptive Autoregressive Model for Reduction of Noise in SPECT.

This paper presents improved autoregressive modelling (AR) to reduce noise in SPECT images. An AR filter was applied to prefilter projection images and postfilter ordered subset expectation maximisation (OSEM) reconstruction images (AR-OSEM-AR method). The performance of this method was compared with filtered back projection (FBP) preceded by Butterworth filtering (BW-FBP method) and the OSEM reconstruction method followed by Butterworth filtering (OSEM-BW method). A mathematical cylinder phantom was used for the study. It consisted of hot and cold objects. The tests were performed using three simulated SPECT datasets. Image quality was assessed by means of the percentage contrast resolution (CR%) and the full width at half maximum (FWHM) of the line spread functions of the cylinders. The BW-FBP method showed the highest CR% values and the AR-OSEM-AR method gave the lowest CR% values for cold stacks. In the analysis of hot stacks, the BW-FBP method had higher CR% values than the OSEM-BW method. The BW-FBP method exhibited the lowest FWHM values for cold stacks and the AR-OSEM-AR method for hot stacks. In conclusion, the AR-OSEM-AR method is a feasible way to remove noise from SPECT images. It has good spatial resolution for hot objects.

High-quality InSb growth by metalorganic vapor phase epitaxy

We have investigated the electron transport properties and crystallinity of InSb films deposited on GaAs substrates. The films were grown by metalorganic vapor phase epitaxy with trimethylindium and trisdimethylaminoantimony as In and Sb sources. Using a two-step growth method and investigating growth conditions extensively, we found that the electron mobility of films either 1.0 or 1.5μm thick strongly depended on the temperature at which the first layer (25nm thick) was grown. The highest mobility, 61,200cm2V−1s−1, was obtained at growth temperature of 260°C and the smallest full-width at half-maximum (FWHM) of the X-ray deflection rocking curve, 205arcsec, was obtained at 320°C. These mobility and FWHM values, both of which are for a total InSb thickness of 1.5μm, are superior to those of InSb films grown by molecular beam epitaxy. Secondary ion mass spectrometry measurements showed that below 340°C the carbon impurity concentration increased drastically with decreasing growth temperature. This carbon incorporated InSb indicated p-type behavior at low temperature by Hall measurement. These results suggest that high concentrations of carbon impurities compensated the extrinsic electrons generated from InSb/GaAs interfacial dislocations.

Selective area growth of GaN nanostructures: A key to produce high quality (11–20) a-plane pseudo-substrates

Selective area growth of GaN nanostructures was performed on (11-20) a-plane GaN/sapphire templates. The dominant lateral growth rate along the in-plane c-direction produces the coalescence of the individual nanostructures into a continuous film. Photoluminescence measurements show the appearance of donor-bound and free exciton emissions in individual nanostructures, pointing towards an improvement of the material quality as compared to the original template. Upon nanostructures coalescence a decrease of the full width half maximum value, down to 2 meV, is observed. These results reveal the high quality of the coalesced film, opening the way to fabricate high quality, non-polar GaN pseudo-substrates.

Spray Pyrloysed TiO2 Dye Sensitized Solar Cells

Thin film of Titanium dioxide (TiO2) has generated a lot of interest because of its attractive properties such as wide band gap, high refractive index, high dielectric constant and absence of non toxicity. TiO2 thin films have been widely investigated for various optical applications and have attracted considerable attention for optical filter, gas sensor, ceramic membranes, photocatalysts and solar cells. Three crystallograpic modifications occur in TiO2: Brookite, Anatase and Rutile. The anatase phase was formed when at growth temperature between 400°C – 700°C and then after 700°C the rutile was formed. The rutile phase has greater density (ρ=4.25 g/cm3) and refractive index (n=2.75 at λ=550 nm) than the anatase phase (ρ = 3.89 g/cm3 and n=2.54 at λ=550 nm).The XRD profiles of TiO2 films deposited on ITO substrates maintained at different substrate temperatures and annealed at 500ºC for 1h are polycrystalline in nature and oriented along (101), (200) planes, A (101) being the predominant peak. The films exhibited tetragonal crystal structure and the peak intensities are in agreement with the JCPDS data (No. 21-1272). The intensity of the diffraction peaks gradually increases and full-width half maximum value increases with increase in substrate temperature and the observed peaks are in agreement with the reported value. The crystallite size is evaluated from the FWHM of the (101) plane using the Scherrer’s formula. The micro strain (ε) and dislocation density (δ) were also calculated. The effect of substrate temperature on the micro-structural parameters of TiO2 indicates that the crystallite size of TiO2 thin films can be tuned between 42 to 25 nm by varying the substrate temperature. It is observed that strain and dislocation density increases as there is decrease in the crystallite size.Transmission spectra of the annealed TiO2 films deposited at different substrate temperatures exhibit 30 to 50 % transmission which increases upto 70 %. The value of the absorption co-efficient(α) was calculated from the transmission spectra. Band gap of the films was calculated from the Tauc’s plot decreased from 3.45 eV to 3.20 eV with increase of substrate temperature. Similar behaviour was observed by earlier workers.Gold ohmic contacts were evaporated on both the ends of the surface of the films. Linear I –V characteristics is observed. The room temperature resistivity of the films were 1x107 ohm cm, 7x 106 ohm cm, 4 x 106 ohm cm and 1x 106 ohm cm were obtained for the films deposited at 375°C, 400°C, 425°C, 450°C respectively. To reduce the resistivity of the films, they were annealed in vacuum at 450°C for 1 hour. The resistivity of the films decreased to 2 x 103 ohm cm, 7 x 102 ohm cm, 3 x 102 ohm cm and 90 ohm cm for the films deposited at 375°C, 400°C, 425°C, 450°C respectively after vacuum annealing. The room temperature mobility and carrier concentration of the films after vacuum anneal varied in the range 10 cm2V-1s-1 to 3 cm2V-1s-1 and from 3.2 x 1015 cm-3 to 2.31 x 1016 cm-3 for the films deposited at 375°C, 400°C, 425°C, 450°C respectively.Preliminary studies on Dye sensitized solar cells prepared using a combination of natural dyes (Strawberries, Hibiscus, Chlorophyll) in the ratio (1:1:1) as photo-sensitizer, showed the better photovoltaic performance compared with other single dyes. For the films deposited at 450°C and vacuum ennealed, Voc of 0.46V, Jsc of 1.25 mA cm-2, ff of 0.63, η of 0.36% were obtained for a cell area of 5 cm2.

Effect of AC target power on AlN film quality

The influence of alternating current (AC) target power on film stress, roughness, and x-ray diffraction rocking curve full width half maximum (FWHM) was examined for AlN films deposited using S-gun magnetron sputtering on insulative substrates consisting of Si wafers with 575 nm thermal oxide. As the AC target power was increased from 5 to 8 kW, the deposition rate increased from 9.3 to 15.9 A/s, film stress decreased from 81 to −170 MPa, and the rocking curve FWHM increased from 0.98 to 1.03°. AlN film behavior is observed to change with target life; films deposited at 200 kWh target life were approximately 40 MPa more compressive and had 0.02° degree higher rocking curve FWHM values than films deposited at 130 kWh. AlN films deposited in two depositions were compared with films deposited in a single deposition, in order to better characterize the growth behavior and properties of AlN films deposited on an existing AlN film, which is not well understood. Two deposition films, when compared with single deposition films, showed no variation in residual stress trends or grain size behavior, but the average film roughness increased from 0.7 to 1.4 nm and rocking curve FWHM values increased by more than 0.25°.

Nanoporous InGaN prepared by KOH electrochemical etching with different light sources

A number of porous InGaN samples of relatively high In composition ∼47% were prepared via electrochemical etching using diluted KOH bath. The porous samples were synthesised with the assistance of different types of illumination; Xenon and UV light. Fabrication of porous InGaN without light illumination was also demonstrated. The effects of using different light sources on the properties of porous InGaN were studied for the first time. Observation through field emission scanning electron spectroscopy (FESEM) revealed that different types of illumination resulted in different surface morphologies. Overall, the high resolution X-ray diffraction (HR-XRD) rocking curves measurement showed that the value of full width at half maximum (FWHM) of all etched samples decreased relative to the as-grown sample due to removal of dislocation defects on the surface after etching. It should be noted that, etched sample that used Xenon illumination showed the lowest FWHM value. On the other hand, photoluminescence (PL) measurement indicated that all of the porous InGaN samples exhibited higher PL intensity than the as-grown sample, showing improvement in the aspect of optical property. Moreover, red-shifted characteristic in PL spectra was also observed in the porous samples, suggesting a relaxation of compressive stress occurred in the samples. The properties observed imply the potential utility of porous InGaN in optical and sensor applications.

Characterization of free-standing single-crystal diamond prepared by hot-filament chemical vapor deposition

Hot filament chemical vapor deposition (HFCVD) possesses a large potential to scale-up for the growth of single-crystal diamond (SCD). This study investigates the crystalline qualities of SCD fabricated by HFCVD. A tungsten impurity level of 1018cm−3 was detected with secondary ion mass spectroscopy. The full-width at half maximum (FWHM) of the rocking curve (004) was 39.5arcsec, where that of seed substrates was 42.8arcsec. A clear free-exciton recombination radiation was observed in cathodoluminescence spectra. The Raman spectra presented a single peak centered at 1333.2cm−1 with a FWHM value of 1.9cm−1. These results indicate that the HFCVD-grown SCD has good crystalline quality comparable to the seed substrates.

Quantitative analysis of crystal scale deformation heterogeneity during cyclic plasticity using high-energy X-ray diffraction and finite-element simulation

Modern high-energy X-ray diffraction (HEXD) experiments coupled with a crystal-based finite-element model employing forward projection of virtual X-rays through each element is applied to study cyclic plasticity. An Okegawa mold copper specimen was cyclically deformed in situ at the Advanced Photon Source. The strain amplitudes of the cyclic experiments reached well into the plastic regime and diffraction images were generated at several points in the loading history using a HEXD methodology. Four grains within the bulk of a polycrystalline sample were tracked and interrogated with X-rays. Diffraction peak data were reduced to center of mass (COM) and full width at half maximum (FWHM) values in the detector coordinates 2θ (radial) and η (azimuthal). The peaks evolved with cycles and changed significantly when the plastic strain amplitude was increased. Large changes in the peaks (especially the azimuthal FWHM values) were also observed during the course of one loading cycle; larger η FWHM values were seen at the compressive end of the cycles. This trend was reversed when the sample was initially loaded in compression. Diffracted intensity distributions were also seen to change significantly from one grain to the next. Using a virtual diffractometer model, COM and FWHM values were computed from the modeling results by projecting virtual X-rays through the finite-element mesh and compared to the experimental data. The finite-element polycrystal model serves as the final step in the data reduction process, revealing significant spatial heterogeneity of orientation, stress and plastic strain rate distributions. Studying these distributions collectively will be necessary to fully understand the detailed elastic–plastic deformation behavior within each grain and to explore problems such as microcrack initiation hypotheses in polycrystalline materials.

SU‐F‐18C‐14: Hessian‐Based Norm Penalty for Weighted Least‐Square CBCT Reconstruction

Purpose:To develop a Hessian‐based norm penalty for cone‐beam CT (CBCT) reconstruction that has a similar ability in suppressing noise as the total variation (TV) penalty while avoiding the staircase effect and better preserving low‐contrast objects.Methods:We extended the TV penalty to a Hessian‐based norm penalty based on the Frobenius norm of the Hessian matrix of an image for CBCT reconstruction. The objective function was constructed using the penalized weighted least‐square (PWLS) principle. An effective algorithm was developed to minimize the objective function using a majorization‐minimization (MM) approach. We evaluated and compared the proposed penalty with the TV penalty on a CatPhan 600 phantom and an anthropomorphic head phantom, each acquired at a low‐dose protocol (10mA/10ms) and a high‐dose protocol (80mA/12ms). For both penalties, contrast‐to‐noise (CNR) in four low‐contrast regions‐of‐interest (ROIs) and the full‐width‐at‐half‐maximum (FWHM) of two point‐like objects in constructed images were calculated and compared.Results:In the experiment of CatPhan 600 phantom, the Hessian‐based norm penalty has slightly higher CNRs and approximately equivalent FWHM values compared with the TV penalty. In the experiment of the anthropomorphic head phantom at the low‐dose protocol, the TV penalty result has several artificial piece‐wise constant areas known as the staircase effect while in the Hessian‐based norm penalty the image appears smoother and more similar to that of the FDK result using the high‐dose protocol.Conclusion:The proposed Hessian‐based norm penalty has a similar performance in suppressing noise to the TV penalty, but has a potential advantage in suppressing the staircase effect and preserving low‐contrast objects.This work was supported in part by National Natural Science Foundation of China (NNSFC), under Grant Nos. 60971112 and 61375018, and Fundamental Research Funds for the Central Universities, under Grant No. 2012QN086.

Growth of zinc oxide on pyrolytic graphite sheet by electrochemical and mist chemical vapor depositions

AbstractGrowth of zinc oxide (ZnO) on pyrolytic graphite sheet (PGS) by electrochemical deposition (ECD) and mist chemical vapor deposition (CVD) was investigated in the viewpoint of crystal orientations. We examined the fullwidth at half‐maximum (FWHM) of X‐ray rocking curve profiles of graphite 0002 and ZnO 0002 diffractions for the investigations. In the case of ECD, thermal annealing at 400, 800, and 1000 °C for PGS before the growth reduced the FWHM value of the grown ZnO.On the other hand, in the case of mist CVD, the growth process and an etching process which may flatten the surface roughness simultaneously occurred. As a result, the FWHM values of the grown ZnO and the PGS were almost the same. These results indicate that each ZnO grain was grown on each graphite grain along with a same c‐orientation direction. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of surrounding materials on iterative reconstruction-based line-source response function, and annihilations outside the source assessed by a small animal PET scanner

The aims of this study were (1) to evaluate the effect of surrounding materials on the iterative reconstruction-based line-source response function (IR-RF) of (18)F, (11)C, (13)N, and (15)O using a preclinical PET system, and (2) to determine whether and how annihilation outside the source can be visualized experimentally. We performed all the measurements using the LabPET-8 PET/CT subsystem built-in the Triumph II platform (TriFoil Imaging, Inc., Northridge, CA, USA). IR-RF was measured for (18)F, (11)C, (13)N, and (15)O, and was expressed as full-width at half-maximum (FWHM) and full-width at tenth maximum (FWTM) using a glass capillary phantom mounted in materials of various densities, which were chosen to cover the wide range of real tissues. To determine whether and how annihilation outside the source can be visualized, we designed a concentric ring paper phantom, which consisted of a source at the center with 4 ring-like paper layers. When the radionuclides were placed in air (material density 0g/cm(3)), IR-RFs were similar among the radionuclides tested. As the surrounding material density increased, IR-RFs for higher energy-emitting radionuclides ((11)C, (13)N, and (15)O) became worse, whereas those of (18)F remained relatively constant over the range of surrounding material densities (0-2.17g/cm(3)). Both FWHM and FWTM values were closely correlated with mean energy of radionuclides at middle to high material densities (material density 0.94-2.17g/cm(3)). The FWTM/FWHM ratio of high energy-emitting radionuclides such as (15)O increased as a function of material density, which was followed by subsequent decrease at high material densities (1.2-2.17g/cm(3)). Using a concentric ring paper phantom, annihilations outside the source were visible and measurable. The innermost layer was visible with all radionuclides, whereas the outer layers only with high energy positron emitters. The results indicate that surrounding material affects IR-RF particularly for high energy positron emitters. Furthermore, annihilation outside the radio-active source can be visualized with some circumstances such as those seen with a concentric ring paper phantom.

Cube Texture Formation of Cu-33at.%Ni Alloy Substrates and CeO<sub>2</sub> Buffer Layer for YBCO Coated Conductors

Cube texture formation of Cu-33 at.%Ni alloy substartes and CeO2buffer layer prepared by chemical solution deposition on the textured substrate were investigated by electron back scattered diffraction (EBSD) and XRD technics systematically. The results shown that a strong cube textured Cu-33at.%Ni alloy substrate with the cube texture fraction of 99.8 % (< 10°) was obtained after annealing at 1000°C for 1 h. The full width half maximum (FWHM) values for the X-ray (111) phi-scan and (002) omega-scan in this substrate were 7.31° and 5.51°, respectively. Furthermore, the cube texture fraction of epitaxially grown CeO2buffer layer was 95 % (< 10°), and the FWHM values of phi-scan and omega-scan being 6.98° and 5.92°, respectively.

Preparation of Epitaxial MgO Films Deposited by RF Magnetic Sputtering on the IBAD-MgO Substrate

We deposited epi-MgO films on the textured ion beam assisted deposition (IBAD)-MgO substrates by RF magnetic sputtering at different substrate temperatures (600–850 °C), RF powers (110–224 W) and oxygen partial pressures (19.5–58.6 mTorr). The microstructure and surface morphology of epi-MgO films were characterized by X-ray diffraction (XRD) and atom force microscope (AFM). It was found that epi-MgO films with c-axis orientation could be easily fabricated for broad parameter ranges. But the in-plane full width half maximum (FWHM) of the epi-MgO film was dependent on the parameters, and the epi-MgO film with the smallest FWHM value of 5.22° was obtained at the optimum parameters. What’s more, the GdBa2Cu3O7 films deposited on the epi-MgO/IBAD-MgO substrate by RF magnetic sputtering showed c-axis orientation.

Intensity inhomogeneity correction for magnetic resonance imaging of human brain at 7T

To evaluate the performance and efficacy for intensity inhomogeneity correction of various sequences of the human brain in 7T MRI using the extended version of the unified segmentation algorithm. Ten healthy volunteers were scanned with four different sequences (2D spin echo [SE], 3D fast SE, 2D fast spoiled gradient echo, and 3D time-of-flight) by using a 7T MRI system. Intensity inhomogeneity correction was performed using the "New Segment" module in SPM8 with four different values (120, 90, 60, and 30 mm) of full width at half maximum (FWHM) in Gaussian smoothness. The uniformity in signals in the entire white matter was evaluated using the coefficient of variation (CV); mean signal intensities between the subcortical and deep white matter were compared, and contrast between subcortical white matter and gray matter was measured. The length of the lenticulostriate (LSA) was measured on maximum intensity projection (MIP) images in the original and corrected images. In all sequences, the CV decreased as the FWHM value decreased. The differences of mean signal intensities between subcortical and deep white matter also decreased with smaller FWHM values. The contrast between white and gray matter was maintained at all FWHM values. LSA length was significantly greater in corrected MIP than in the original MIP images. Intensity inhomogeneity in 7T MRI can be successfully corrected using SPM8 for various scan sequences.

A new approach to designing circular grating focusing reflector

A new approach to designing planar, high numerical aperture, low loss, focusing reflectors using circular subwavelength high contrast gratings is presented. Through analyzing particular physical scene, a mathematical transformation from existing “focus line” convergent beam, which can be achieved by bar grating reflector, to the convergent beam with a “focus point”, is obtained. By changing the shape of the bar grating reflector with the mathematical transformation obtained, a circular grating reflector, which can achieve “focus point” convergent beam, is obtained. The focusing properties and reflection characteristic of the circular grating reflector are numerically studied with the finite element method. After the radially polarized light reflected from circular grating reflector with a diameter of 29.788 μm, the beam will focus at 10 μm away from the reflector, resulting in a numerical aperture of 0.8302 and a reflectivity of 0.9163. In the focal plane, the numerical simulation results present a field distribution with a full width half maximum value of 1.5548μm, which is extremely close to diffraction limit.

Initial clinical experience with a quadrupole butterfly coil for spinal injection interventions in an open MRI system at 1.0 tesla

To report our initial clinical experience with a new magnetic resonance imaging (MRI) quadrupole coil that allows interventions in prone position. Fifteen patients (seven women, eight men; average age, 42.8 years) were treated in the same 1.0-Tesla Panorama High Field Open (HFO) MRI system (Panorama HFO) using a quadrupole butterfly coil (Bfly) and compared with 15 patients matched for sex, age, and MR intervention using the MultiPurposeL coil (MPL), performed in conventional lateral decubitus position (all, Philips Medical Systems, Best, The Netherlands). All interventions were performed with a near-real-time proton density turbo spin echo (PD TSE) sequence (time to repeat/time to echo/flip angle/acquisition time, 600 ms/10 ms/90°/3 s/image). Qualitative and quantitative image analyses were performed, including signal intensity, signal-to-noise and contrast-to-noise ratio (SNR, CNR), contrast, and full width at half maximum (FWHM) measurements. Contrast differed significantly between the needle and muscles (Bfly 0.27/MPL 0.17), as well as the needle and periradicular fat (0.13/0.24) during the intervention (both, p=0.029), as well as the CNR between muscles and the needle (10.61/5.23; p=0.010), although the FWHM values did not (2.4/2.2; p=0.754). The signal intensity of the needle in interventional imaging (1152.9/793.2; p=0.006) and the postinterventional SNR values of subcutaneous fat (15.3/28.6; p=0.007), muscles (6.6/11.8; p=0.011), and the CNR between these tissues (8.7/17.5; p=0.004) yielded significant differences. The new coil is a valid alternative for MR-guided interventions in an open MRI system at 1.0 tesla, especially if patients cannot (or prefer not to) be in a lateral decubitus position or if prone positioning yields better access to the target zone.

偏振态、相位和振幅对受激辐射损耗中损耗光焦斑的影响

As Stimulated Emission Depletion (STED) super-resolution microscopy has a lower resolution, this paper explores the effects of multiphysical variables including light polarization, phases and amplitudes on the focal spots, in order to form a ring-shape depletion focus spot with sharper Full Width at Half Maximum (FWHM) and to increase the resolution of the microscopy. According to Richards-Wolf vector theory, the models of depletion focus spots were established under the actions of polarization, phase and amplitude, the focus spot distribution was calculated in different polarization, phase and amplitude conditions and the distribution of effective fluorescent excitation was obtained by optimizing the parameters. The results show that: by using azimuthal polarization light as depletion, the FWHM is better than those of radial or circular ones; modulations of phase and amplitude are able to reduce the FWHM, and the theoretical value of effective fluorescent excitation FWHM is only 13.2 nm after optimization. By using polarization state, phase and amplitude to modulate the depletion focus spot, the FWHM can be reduced and a higher resolution can be obtained, which is more effective than that using only single physical variable. Moreover, the high quality depletion focus spot and super-resolution ability can be obtained with azimuthal polarization light in STED and the resolution can further be optimized by phase or amplitude modulations based on different realities.

Validation of noise reduction in iterative reconstruction: a simulation phantom study

In the iterative reconstruction method, image noise tends to increase in proportion to falling available photon count and increasing update number. Image filtering is an important factor in single photon emission computed tomography (SPECT) image reconstruction, but it is frequently treated in a subjective way. The aim of this study was to evaluate the effects of pre-reconstruction filtering and post-reconstruction filtering on the iterative reconstruction process. Using simulation phantoms, projection data were reconstructed using ordered subsets expectation maximization (OSEM) with or without compensation for resolution recovery. Pre- and post-reconstruction filtering was performed using a Butterworth filter (BW) (range: 0.3-1.3 cycles/cm) and a Gaussian filter (GA) (range: 0.3-1.3 mm) with various parameters. We evaluated the variances of full width at half maximum (FWHM), coefficients of variation (CV), image contrast and normalized mean squared error (NMSE) values. The FWHM values for pre-reconstruction filtering tended to be lower than those observed for post-reconstruction filtering. These values were 5.1 mm (pre-reconstruction) and 6.7 mm (post-reconstruction). The CV on pre- and post-reconstruction filtering was 7.5% and 11.6%. Pre-reconstruction filtering reduced image noise more effectively than post-reconstruction filtering. The contrast for pre-reconstruction filtering was similar to that observed after post-reconstruction filtering. However, contrast after filtering with a GA slowly decreased as compared to the BW. NMSE values obtained by pre-reconstruction filtering tended to be lower than those observed for post-reconstruction filtering. Pre-reconstruction filtering provided SPECT image quality comparable to that from post-reconstruction filtering, especially when using the BW. Our results suggest that pre-reconstruction filtering is a beneficial method when applied to the iterative reconstruction method with or without compensation for resolution recovery.

Enhanced Sensitivity of Anti-Symmetrically Structured Surface Plasmon Resonance Sensors with Zinc Oxide Intermediate Layers

We report a novel design wherein high-refractive-index zinc oxide (ZnO) intermediary layers are used in anti-symmetrically structured surface plasmon resonance (SPR) devices to enhance signal quality and improve the full width at half maximum (FWHM) of the SPR reflectivity curve. The surface plasmon (SP) modes of the ZnO intermediary layer were excited by irradiating both sides of the Au film, thus inducing a high electric field at the Au/ZnO interface. We demonstrated that an improvement in the ZnO (002) crystal orientation led to a decrease in the FWHM of the SPR reflectivity curves. We optimized the design of ZnO thin films using different parameters and performed analytical comparisons of the ZnO with conventional chromium (Cr) and indium tin oxide (ITO) intermediary layers. The present study is based on application of the Fresnel equation, which provides an explanation and verification for the observed narrow SPR reflectivity curve and optical transmittance spectra exhibited by (ZnO/Au), (Cr/Au), and (ITO/Au) devices. On exposure to ethanol, the anti-symmetrically structured showed a huge electric field at the Au/ZnO interface and a 2-fold decrease in the FWHM value and a 1.3-fold larger shift in angle interrogation and a 4.5-fold high-sensitivity shift in intensity interrogation. The anti-symmetrically structured of ZnO intermediate layers exhibited a wider linearity range and much higher sensitivity. It also exhibited a good linear relationship between the incident angle and ethanol concentration in the tested range. Thus, we demonstrated a novel and simple method for fabricating high-sensitivity, high-resolution SPR biosensors that provide high accuracy and precision over relevant ranges of analyte measurement.