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Optimized image acquisition for dopamine transporter imaging with ultra-high resolution clinical pinhole SPECT
摘要： SPECT can be used to image dopamine transporter (DaT) availability in the human striatum, e.g. for diagnosis of Parkinson’s disease (PD). As traditional SPECT provides limited resolution and sensitivity, we proposed a full ring focusing multi-pinhole SPECT system (G-SPECT-I (Beekman 2015 Eur. J. Nucl. Med. Mol. Imaging 42 S209)) which demonstrated a 2.5 mm reconstructed resolution in phantom scans. G-SPECT-I achieves data completeness in the scan region of interest by translating the patient bed with an xyz-stage and combining projections from all bed positions into image reconstruction using a scanning focus method (SFM). This paper aims to develop dedicated SFM parameters for performing a DaTscan with high effective sensitivity and appropriate sampling. To this end, the axial scanning length was restricted and transaxial bed trajectories with a reduced number of positions based on a convex hull data-completeness model were tested. Quantitative accuracy was assessed using full G-SPECT-I simulations of an Alderson phantom based on measured system matrices. For each sampling strategy, the specific binding ratio (SBR) and asymmetry index (AI) in the left and right striatum, as well as the Localized SBR (L-SBR) and the Localized AI (L-AI) in eight striatal sub-regions were calculated and compared to those of the reference scan which performs full brain oversampling using 112 bed positions. Results show that structures essential for PD diagnosis were visually and quantitatively barely affected even when using the lowest number of bed translations (i.e. 4). The maximum deviation from the reference was only 1.5%, 1.5%, 5.5% and 7.0% for the SBR, AI, L-SBR and L-AI, respectively, when 4 positions were used. Thus, it is possible to perform an accurate DaTscan with a confined axial scan region and a limited number of focused bed positions. This enables protocols for extremely fast dynamic SPECT scans with less than half-minute time frames, which can be useful for motion correction.
关键词： sampling,pinhole collimator,brain imaging,high resolution SPECT,DaTscan,high sensitivity SPECT,clinical SPECT
更新于2025-09-10 09:29:36
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Optical characterization of different waist diameter on microfiber loop resonator humidity sensor
摘要： In this paper, the effect of different waist diameter on silica microfiber loop resonator (MLR) relative humidity (%RH) sensor is reported. The silica fiber was tapered to vary the waist diameter to 3 μm, 4 μm, 5 μm,7 μm, 8 μm and 10 μm using flame brushing technique. The MLR with a 300 μm diameter loop was formed by manually twisted the tapered fiber under an optical microscope into a self-touching loop. Initially, the effect of whispering gallery modes (WGMs) on the MLR was observed. Transmission mode spectra were observed to determine the number of resonated wavelength and quality factor (Q-factor). The Q-factor is observed to be >105 for all samples and MLR with 3 μm diameter achieve the highest Q-factor value. A significant response to %RH from 35% to 85% was observed due to the change of refractive index between the MLR and the surrounding medium resulting different light attenuation in the microfiber. The sensitivity increased by a factor of 12.2 for the MLR with diameter of 7 μm as compared to the smaller diameter MLRs and a factor of 13.7 as compared to straight microfiber (SmF). As for resolution, the MLR with waist diameter of 7 μm improve by a factor of 5 as compared to the smaller waist diameter and a factor of 6.5 as compared to SmF. The proposed humidity sensor employs the microfiber loop resonator without any sensitive material coated on it which reduced the complexity during the fabrication and manufacturing process. The reported results may contribute to the optimal waist diameter of microfiber loop resonators for humidity sensing application.
关键词： sensitivity,resolution,humidity sensor,microfiber loop resonator,Whispering gallery mode
更新于2025-09-10 09:29:36
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Nanocomposites-based nitrated polyethersulfone and doped ZnYNiO for selective As <sup>3+</sup> sensor application
摘要： The contamination of arsenic (As3+) cation in drinking water is one of the most well-known sources for human arsenic poison. Due to its high toxicity to human, there is a need to develop an efficient and low-cost method to detect it in aquatic environment. A sensor of nitrated polyethersulfone (PES-NO2) doped with ZnYNiO nanocomposites was successfully fabricated. PES-NO2 was synthesized in this study using H2SO4: HNO3 while ZnYNiO nanoparticles were fabricated using wet-chemical technique under low temperature and basic condition. The results of Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) analysis did confirm the interactions between the doped nanoparticles and nitro functions grafted on PES backbone. The developed polymeric nanocomposite (PES-NO2-ZnYNiO) was then used as a superb coating sensor for As3+. The working electrode of desire heavy metal ion sensor was fabricated by glassy carbon electrode (GCE) coated with PES-NO2-ZnYNiO nanocomposites as layer of thin film. To estimate the cationic sensor performances, a calibration curve obtained from current versus electrolyte (selective As3+ ion) concentration relation was plotted. The linearity of calibration curve is found over the linear dynamic range (LDR) of 0.1 nM~0.1 mM. The slope of calibration curve is used to measure the sensitivity and detection limit (DL) of As3+ cation sensor, and these are 9.8101 μA μM?1 cm?2 and 96.77 ± 4.84 pM, respectively. Therefore, the As3+ ion sensor is found as selective with good sensitivity, reproducible with high accuracy, validated in real environmental samples, long-term stability in aqueous medium, and highly active with short response time.
关键词： arsenic sensor,sensitivity,characterization,electrochemical method,synthesis,ZnYNiO,environmental safety,nitrated polyethersulfone
更新于2025-09-10 09:29:36
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[IEEE 2018 2nd International Conference on Engineering Innovation (ICEI) - Bangkok (2018.7.5-2018.7.6)] 2018 2nd International Conference on Engineering Innovation (ICEI) - Diabetic retinopathy fundus image classification using discrete wavelet transform
摘要： Diabetes is an incurable disease which erodes away body slowly, this disease in becoming common and becoming a cause of social distress. The only solution to this problem is early detection of disease and take precautionary measure to keep its effects to minimum. Since it affects various parts of body, the affected organ also includes eye which is very sensitive to any kind of distress. Diabetic Retinopathy effects of diabetes on eye retina, which includes rupturing of retina blood vessels and abnormal growth of blood vessels in retina, which ultimately causes blindness. Diabetic Retinopathy can be identified by examining the retinoscopy images. In this paper, retinoscopy images were processed using wavelet transform. Wavelet coefficients extracted from the images were obtained to identify Diabetic Retinopathy. KNN and SVM were used to classify the retinoscopy images. This papers have shown remarkable improvement as compared to previous studies, with KNN at 98.16 % accuracy and SVM at 97.85 % accuracy.
关键词： sensitivity,specificity,Discrete Wavelet Transform (DWT),accuracy,KNN,Diabetic Retinopathy (DR),histogram equalization,SVM
更新于2025-09-10 09:29:36
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Studies on Temperature and Strain Sensitivities of a Few-mode Critical Wavelength Fiber Optic Sensor
摘要： This paper studied the relationship between the temperature/strain wavelength sensitivity of a fiber optic in-line Mach-Zehnder Interferometer (MZI) sensor and the wavelength separation of the measured wavelength to the critical wavelength (CWL) in a CWL-existed interference spectrum formed by interference between LP01 and LP02 modes. The in-line MZI fiber optic sensor has been constructed by splicing a section of specially designed few-mode fiber (FMF), which support LP01 and LP02 modes propagating in the fiber, between two pieces of single mode fiber. The propagation constant difference, Δβ, between the LP01 and LP02 modes, changes non-monotonously with wavelength and reaches a maximum at the CWL. As a result, in sensor operation, peaks on the different sides of the CWL then shift in opposite directions, and the associated temperature/strain sensitivities increase significantly when the measured wavelength points become close to the CWL, from both sides of the CWL. A theoretical analysis carried out has predicted that with this temperature/strain sensor approach, the temperature/strain wavelength sensitivities are governed by the wavelength difference between the measured wavelength and the CWL. This conclusion was seen to agree well with the experimental results obtained. Combining the wavelength shifts of the peaks and the CWL in the transmission spectrum of the SFS structure, this study has shown that this approach forms the basis of effective designs of high sensitivity sensors for multi-parameter detection and offering a large measurement range to satisfy the requirements needed for better industrial measurements.
关键词： few mode fiber,temperature sensitivity,In-line Mach-Zehnder interferometer,strain sensitivity,critical wavelength
更新于2025-09-09 09:28:46
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Design considerations of a surface plasmon resonance (SPR) based tapered fiber optic bio-sensing probe with graphene-MoS2 over layers
摘要： In this paper, we have reported the design considerations of a surface plasmon resonance (SPR) based tapered fiber optic sensor by coating a thin film of platinum on a tapered fiber core followed by graphene-molybdenum disulphide (MoS2) monolayers. The theoretical study is based on five-layer matrix model. To see the effect of graphene-MoS2 over layers, performance parameters in terms of sensitivity and detection accuracy are evaluated for four taper profiles viz. exponential-linear, linear, parabolic and quadratic along with the taper ratio. From results, we inferred that with increase in taper ratio sensitivity also increases while detection accuracy decreases monotonically. For the proposed sensor configuration, maximum sensitivity value is found to be 7.04μm/RIU at taper ratio 2.0 for exponential-linear taper profile while maximum detection accuracy obtained is 16.7623μm-1, at taper ratio 1.0. Thus, the results show that by introducing additional graphene-MoS2 monolayers, the sensitivity of the proposed sensing probe is enhanced by more than 44% at taper ratio 2 as compared to the conventionally used SPR based fiber optic sensors coated with platinum only. Also, the effect of increasing number of layers of graphene and MoS2 on the performance parameters is evaluated and compared. The advantageous features of the graphene and MoS2 layers have also been discussed for bio-sensing applications.
关键词： surface plasmon resonance,graphene,Fiber optic sensors,sensitivity and detection accuracy,molybdenum di-sulphide
更新于2025-09-09 09:28:46
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Design and numerical analysis of a graphene-coated fiber-optic SPR biosensor using tungsten disulfide
摘要： This article provides a simple hybrid design and rigorous numerical analysis of a fiber optic–based surface plasmon resonance (SPR) biosensor for DNA hybridization. The sensor core and both sides of the cladding are constructed with optical fiber, whereas the middle portion of the cladding is filled with the proposed hybrid of silver, tungsten disulfide (WS2), graphene, and a sensing medium. To the best of our knowledge, this is the first demonstration of such a highly sensitive SPR biosensor using WS2 for sensing DNA hybridization. The sensitivity, detection accuracy, and figure of merit are considered as the performance parameters and are analyzed in detail. The analyses reveal an impressive enhancement of the overall performance of the proposed sensor. Insertion of a WS2 layer between silver and graphene provides a sensor with sensitivity higher than that of other sensors reported to date. Additionally, concurrent improvement of all performance parameters is shown by this hybrid sensor, which is not the case for sensors based only on graphene. An increased number of graphene-only layers increases the sensitivity and decreases the detection accuracy and figure of merit. Numerical analysis shows that the variation of the SPR angle for mismatched DNA strands is quite negligible, whereas that for complementary DNA strands is considerable, which is essential for proper detection of DNA hybridization. Therefore, the proposed biosensor opens a new window toward detection of biomolecular interactions.
关键词： DNA hybridization,transmittance,surface plasmon resonance angle,Biosensor,sensitivity,tungsten disulfide
更新于2025-09-09 09:28:46
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Design and investigation of a sensitivity-enhanced fiber Bragg grating sensor for micro-strain measurement
摘要： The fiber Bragg grating (FBG) sensors are widely used in strain measurement. However, the current FBG sensors are not sensitive enough to monitor the micro-strain. In order to provide a feasible method to monitor the micro-strain of lithium-ion battery, a novel fiber Bragg grating (FBG) strain sensors with enhanced sensitivity was developed in this paper. A lever mechanism was adopted to enhance the sensor sensitivity and flexure hinges as well as serpentine springs were used in sensor structure. The sensor structure dimension was optimized through theoretical calculation and finite element analysis, and the optimized sensor was manufactured and tested. The results of calibration test show that in the measuring range of ±500 με, the sensor has strain sensitivity of 11.49 pm/με, good linearity and repeatability as well as tiny hysteresis error. The battery experimental results illustrate there is a same trend between strain and voltage of battery, and a good uniformity under three working modes of battery. This proposed FBG sensor will provide a solution for strain measurement of battery.
关键词： Sensitivity-enhanced,Battery strain measurement,Flexure hinge,FBG sensor
更新于2025-09-09 09:28:46
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A THz Receiver with Novel Features and Functionality
摘要： The presented THz receiver is based on an antenna coupled titanium micro-bolometer. A new geometrical design improves the robustness and extends the lifetime of the sensor. A study of sensor lifetime using different biasing currents is presented. The lifetime was verified by several tests and over 1000 operating hours. A new micro-bolometer sensitivity measurement algorithm is presented in the paper and measurement results using the proposed algorithm are shown. The new algorithm was developed to be suitable for ATM production testing. In the paper, a novel feature called “sensitivity boosting” is described, together with its influence on sensitivity and lifetime.
关键词： micro-bolometer lifetime,sensitivity boosting,THz micro-bolometer
更新于2025-09-09 09:28:46
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Solving the oxygen sensitivity of sensitized photon upconversion in life science applications
摘要： The conversion of low-energy light into high-energy light, also known as upconversion, can be exploited in life science applications such as bioimaging and phototherapy. Sensitized triplet–triplet annihilation upconversion (sTTA-UC) is one type of upconversion in which a photosensitizer is excited using a low-energy light and then transfers energy to an annihilator that emits at much higher energy. Changing the molecular components enables the fine-tuning of excitation and emission wavelengths. sTTA-UC is an appealing approach because it results in high upconversion efficiencies. However, its sensitivity to the presence of dioxygen in living cells and biological tissues is problematic. In this Review , the essential requirements of sTTA-UC for bio-nanodevices and life science applications are outlined before discussing the different ways to circumvent the dioxygen sensitivity of sTTA-UC.
关键词： phototherapy,dioxygen sensitivity,sensitized triplet–triplet annihilation upconversion,bioimaging,upconversion
更新于2025-09-09 09:28:46