Search

In the present study, the response of the crystalline scintillator LaBr3:Ce when excited with X-rays at tube voltages from 50 kVp to 150 kVp was investigated, for possible use in hybrid medical-imaging systems. A single crystal (10 × 10 × 10 mm3) was irradiated by X-rays within the aforementioned tube-voltage range, and the absolute efficiency (AE), as well as the detective quantum efficiency for zero spatial-frequency (DQE(0)), were measured. The energy-absorption efficiency (EAE), the quantum-detection efficiency (QDE) and the spectral compatibility with various optical photodetectors were also calculated. The results were compared with the published data for the LaCl3:Ce, Bi4Ge3O12 (BGO), Lu2SiO5:Ce (LSO), and CdWO4 single crystals of equal dimensions. The AE values of the examined crystal were found to be higher than those of the compared crystals across the whole X-ray tube-voltage range. Regarding the EAE, LaBr3:Ce demonstrated a comparatively better performance than the LaCl3:Ce crystal. The emitted-light spectrum of LaBr3:Ce was found to be compatible with various types of photocathodes and silicon photomultipliers. Moreover, the LaBr3:Ce crystal exhibited excellent performance concerning its DQE(0). Considering these properties, the LaBr3:Ce crystal could be considered as a radiation-detector option for hybrid medical-imaging modalities, such as PET/CT and SPECT/CT.

It is well known that the luminescence efficiency of single crystals is affected by external parameters, such as the environmental temperature, especially in harsh environments. Due to this, it is of worth to examine the influence of temperature on the luminescence output of single-crystal scintillators. In this study lutetium aluminum garnet (Lu3Al5O12:Ce-LuAG:Ce) was examined, against previously published data for cadmium tungstate (CdWO4) and calcium fluoride doped with europium (CaF2:Eu) single crystals. Experiments were carried using a medical X-ray source, set to fixed high voltage (90kVp) and tube current/exposure time product (63mAs), in order to record the produced light, under different temperature conditions (20-120 Celsius). An interesting finding is that temperature, in the examined range, appear to have minimal influence on the light output of LuAG:Ce, in the contrary to the previously examined crystals (CdWO4 and CaF2:Eu) where the luminescence output constantly decreased with increasing temperature. The thermal stability of LuAG:Ce, in the examined temperature range, renders it a good choice, besides medical imaging, also for application in harsh environments as well as for long-term operation in high power LEDs.

A rare-earth trihalide scintillator, CeBr3, in 1 cm edge cubic monocrystal form, is examined with regard to its principal luminescence and scintillation properties, as a candidate for radiation imaging applications. This relatively new material exhibits attractive properties, including short decay time, negligible afterglow, high stopping power and emission spectrum compatible with several commercial optical sensors. In a setting typical for X-ray radiology (medical X-ray tube, spectra in the range 50–140 kVp, human chest equivalent filtering), the crystal’s light energy flux, absolute efficiency (AE) and X-ray luminescence efficiency (XLE) were determined. Light energy flux results are superior in comparison to other four materials broadly used in modern medical imaging (slope of the linear no-threshold fit was 29.5). The AE is superior from 90 kVp onwards and reaches a value of 29.5 EU at 140 kVp. The same is true for the XLE that, following a flat response, reaches 9 × 10−3 at 90 kVp. Moreover, the spectral matching factors and the respective effective efficiencies (EE) are calculated for a variety of optical sensors. The material exhibits full compatibility with all the flat-panel arrays and most of the photocathodes and Si PMs considered in this work, a factor that proves its suitability for use in state-of-the-art medical imaging applications, such as CT detectors and planar arrays for projection imaging.

The aim of this study is to evaluate the suitability of crystalline scintillator LaCl3:Ce for possible use in hybrid medical imaging systems, such as PET/CT and SPECT/CT scanners. For this purpose, a single crystal (10 × 10 × 10 mm3) was irradiated by X-rays within the tube voltage range from 50 to 150 kVp, and the absolute efficiency (AE) was measured experimentally. The energy absorption efficiency (EAE), quantum detection efficiency (QDE), and the spectral compatibility with various optical detectors were also calculated with the use of mathematical formulas. The results were compared with published data for Bi4Ge3O12 (BGO), Lu2SiO5:Ce (LSO), and CdWO4 single crystals of equal dimensions, commonly used in medical imaging applications. The luminescence efficiency values of the examined crystal were found to be higher than those of LSO, BGO, and CdWO4 crystals, within the whole X-ray tube voltage range. In the matter of EAE, LaCl3:Ce demonstrated reduced performance with respect to LSO and CdWO4 crystals. The emission spectrum of LaCl3:Ce was found to be compatible with various types of photocathodes and silicon photomultipliers (SiPMs). Considering these properties, LaCl3:Ce crystal could be considered suitable for use in hybrid medical imaging systems.

The aim of the current study was to present a simple method for the fabrication of quantum dot (QD)/polymer films for possible use as a luminescent material in medical applications. To this aim the poly(methyl methacrylate) (PMMA) polymer matrix was modified in order to host Zinc Copper Indium Sulfide encapsulated by an outer core of Zinc Sulfide (ZnCuInS/ZnS) QD nanocrystals, through dispersion. Four composite PMMA films of ZnCuInS/ZnS nanocrystals with maximum emission at 530 nm and concentrations of 1.0, 4.0, 6.0 and 10.0 %w/v, were prepared. X-ray irradiation and scanning electron microscopy (SEM) micrographs were used to evaluate the volume homogeneity of the final samples, as a measure of QD dispersion. The coefficient of variation (CV) estimated from homogeneity measurements, increased with increasing concentration, for the 1.0, 4.0 and 6.0 %w/v samples. The minimum CV value was obtained for the 10.0 %w/v sample which is attributed to the incorporation of sonication in the final product, during the fabrication process. Homogenous dispersion was observed from the SEM micrographs.

During the last decades, there is increasing interest in applications of scintillators at harsh environments (i.e., high temperatures or radiation fluxes), such as in geophysical detectors for deep geology boreholes, non-destructive testing (NDT) of pipelines in oil and gas industry, space and marine exploration, nuclear reactor monitoring, radiation chemistry, etc. To this aim, the current study is the first step towards the investigation of the luminescence efficiency dependence of single-crystal scintillators over wide temperature ranges. Calcium fluoride doped with europium (CaF2:Eu) was selected due to the fact that it has a high melting point at 1418°C and is also robust to mechanical and thermal shocks. The dimensions of the single-crystal sample were 10x10x10 mm3, and it was irradiated using typical X-ray radiographic exposures (90 kVp, 63mAs) in order to measure the light photon intensity dependence with temperature (22 to 128 °C). The luminescence efficiency was found maximum at the lowest examined temperature (22.01 efficiency units-E.U. at 22 °C-environmental). With increasing temperature, the luminescence efficiency decreased almost exponentially due to thermal quenching (4.43 efficiency units-E.U. at 128 °C).

Scintillators are radiation converters applied in medical imaging detectors, in applications at harsh environments, including in geophysical detectors for deep geology boreholes, non-destructive testing (NDT) in gas and oil facilities, space, marine exploration, etc. In this study the luminescence efficiency dependence of single-crystal scintillators was examined with increasing temperature. Cadmium tungstate (CdWO4) was examined against calcium fluoride doped with europium (CaF2:Eu). The dimensions of the single crystals’ samples were 10x10x10 mm3 and were irradiated using X-ray radiographic exposures (90 kVp, 63mAs) to measure the light output with temperature (22 to 128 °C). The luminescence efficiency was found in both cases maximum at the lowest examined temperature (23.06 efficiency units-E.U for CdWO4 and 22.01 E.U. for CaF2:Eu, at 22 °C-environmental). With increasing temperature, the luminescence efficiency constantly decreased for both crystals due to thermal quenching (5.32 efficiency units for CdWO4 and 4.43 for CaF2:Eu, at 128 °C). In the mid-range (50-80 °C) CdWO4 shows increased differences compared to CaF2:Eu. CdWO4 has a higher density (7.9 g/cm 3) and luminescence signal than CaF2:Eu (3.18 g/cm 3), thus it is suitable, besides medical imaging, also for operation in harsh environments.

The aim of the current work was to investigate the modulation transfer function (MTF) of a non-destructive testing (NDT)/ industrial inspection CMOS sensor in conjunction with a calcium tungstate (CaWO4) thin screen, following both the IEC 62220-1:2003 and IEC 62220-1-1:2015 methods. Thin screen samples, with dimensions of 2.7x3.6 cm2 and mean coating thickness of 36.26 mg/cm2 (actual thickness: 118.9 μm estimated from scanning electron microscopy-SEM images) were extracted from an Agfa Curix universal screen and were manually coupled to the active area of a high resolution, active pixel (APS), complementary metal oxide semiconductor (CMOS) sensor. Experiments were performed using the RQA-5 beam quality, as described in the IEC series. Modulation transfer function was assessed using the slanted-edge method. The final MTF, following IEC 62220-1-1:2015 was obtained through averaging the oversampled edge spread function (ESF), using a custom-made software developed in our laboratory. MTF values were found with close agreement in the low and medium spatial frequency ranges, for both methods. Thereafter, MTFs calculated following the 62220-1:2003 protocol, were found overestimated for spatial frequencies higher than 5.7 cycles/mm. The combination of the thin calcium tungstate screen and the CMOS sensor provided very promising image resolution properties and thus could be also considered for use in CMOS based X-ray imaging devices, for various applications.

The aim of this study was to investigate the modulation transfer function (MTF) and the effective gain transfer function (eGTF) of a non-destruc­­tive testing (NDT)/industrial inspection complementary metal oxide semi­conductor (CMOS) sensor in conjunction with a thin calcium tungstate (CaWO4) screen. Thin screen samples, with dimensions of 2.7x3.6 cm2 and thick­ness of 118.9 μm, estimated from scanning electron microscopy-SEM im­ages, were extracted from an Agfa Curix universal screen and coupled to the active area of an active pixel (APS) CMOS sensor. MTF was assessed using the slanted-edge method, following the IEC 62220-1-1:2015 method. MTF values were found high across the examined spatial frequency range. eGTF was found maximum when CaWO4 was combined with charge-coupled devices (CCD) of broadband anti-reflection (AR) coating (17.52 at 0 cycles/mm). The com­bi­nation of the thin CaWO4 screen with the CMOS sensor provided very pro­mis­ing image resolution and adequate efficiency properties, thus could be also con­sidered for use in CMOS based X-ray imaging devices, for various applications.

The aim of this article is to evaluate optical characteristics, such as the intrinsic conversion efficiency and the inherent light propagation efficiency of three polymethyl methacrylate (PMMA)/methyl methacrylate (MMA) composite ZnCuInS/ZnS (core/shell) nanocrystal flexible films. The concentrations of these were 100 mg/mL, 150 mg/mL, and 250 mg/mL, respectively. Composite films were prepared by homogeneously diluting dry powder quantum dot (QD) samples in toluene and subsequently mixing these with a PMMA/MMA polymer solution. The absolute luminescence efficiency (AE) of the films was measured using X-ray excitation. A theoretical model describing the optical photon propagation in scintillator materials was used to calculate the fraction of the generated optical photons passed through the different material layers. Finally, the intrinsic conversion efficiency was calculated by considering the QD quantum yield and the optical photon emission spectrum.

Quantum dots (QDs) are quite interesting materials due to their unique chemical and physical properties. ZnCuInS/ZnS QDs can be produced either in hydrophobic or hydrophilic form, are non-toxic, and thus favorable for studies in the area of biology. Poly(methyl methacrylate) (PMMA) is a well-known biocompatible resin which is widely used in dentistry, ophthalmology, and orthopedic surgery. Four composite PMMA films of ZnCuInS/ZnS nanocrystals with maximum emission at 530 nm and concentrations of 1.0, 4.0, 6.0, and 10.0 %w/v, were prepared. X-ray irradiation was used to evaluate the volume homogeneity of the final samples, as a measure of QD dispersion. The luminescent efficiency was evaluated, under ultraviolet (UV) irradiation. The process of UV irradiation involved the experimental measurement of the forward luminescent light, as well as the backward luminescent light, in order to accurately calculate the energy quantum efficiency (EQE) of ZnCuInS/ZnS QDs. Reflected UV radiation was also measured, and results showed that it ranges from 2% to 6% approximately as the QD concentration rises from 1.0 %w/v to 10.0 %w/v. Beyond 6.0 %w/v, the reflected UV radiation remains essentially unchanged. Additionally, the reflected UV radiation remained unaffected as the power of the incident UV increased. Approximately 9% of incident UV radiation passed through the 1.0 %w/v sample, whereas for the samples with higher ZnCuInS/ZnS concentration, 0% UV radiation passed through. The EQE reached a maximum of about 45% with the 10.0 %w/v sample, while it remained practically unaffected relative to the increase of the emitted UV power. The homogeneity measurements revealed that the coefficient of variation (CV) increased with increasing concentration, for the 1.0, 4.0, and 6.0 %w/v samples. The minimum CV was obtained for the sample of 10.0 %w/v due to the incorporation of sonication in the final product, during the fabrication process.

The aim of this work was to prepare three composite ZnCuInS/ZnS (core/shell) quantum dot (QD) flexible films and to examine their luminescent properties under X-ray excitation for potential use in medical imaging modalities. Three PMMA/ QD ZnCuInS composite films, with emission at 530 nm prepared, with concentrations 2.5, 10.0 and 15.0 %w/v. Composite films prepared by homogenously diluting dry powder QD samples in toluene and subsequently mixing with a PMMA/MMA polymer solution. The Absolute Luminescence Efficiency (AE) of the produced films was assessed using medical X-ray excitation. It found that the AE of the films is decreasing in an almost linear way, with increasing X-ray tube voltage. Also, it found that for QDs concentration up to 10.0 %w/v, the AE is increasing rapidly while after that point the relative increase of AE is rather limited. The spectral compatibility of the ZnCuInS/ZnS screen, with various existing optical detectors, was investigated after emission spectra measurements. Highest compatibility (over 90%) found for most CMOS and CCD detectors used in modern imaging modalities.

In this study, the light output of a zinc selenide activated with tellurium (ZnSe: Te) single crystal was measured for X-ray radiography applications. A cubic crystal (10 &times, 10 &times, 10 mm) was irradiated using X-rays with tube voltages from 50 to 130 kV. The resulting energy absorption efficiency, detective quantum efficiency, and absolute luminescence efficiency were compared to published data for equally sized GSO: Ce (gadolinium orthosilicate) and BGO (bismuth germanium oxide) crystals. The emitted light was examined to estimate the spectral compatibility with widely used optical sensors. Energy absorption efficiency and detective quantum efficiency of ZnSe: Te and BGO were found to be similar, within the X-ray energies in question. Light output of all three crystals showed a tendency to increase with increasing X-ray tube voltage, but ZnSe: Te stood at least 2 EU higher than the others. ZnSe: Te can be coupled effectively with certain complementary metal&ndash, oxide&ndash, semiconductors (CMOS), photocathodes, and charge-coupled-devices (CCD), as the effective luminescence efficiency results assert. These properties render the material suitable for various imaging applications, dual-energy arrays included.

The aim of the present work was to investigate the absolute luminescence efficiency (AE) of a lutetium aluminum Lu3Al5O12:Ce (LuAG:Ce) garnet, doped with cerium, combined with various microelectronic optical sensors. Two LuAG:Ce samples, with dimensions of 5 × 5 × 10 and 10 × 10 × 10 mm3 were examined. The light emitted by the crystals, was evaluated by performing measurements of the AE using X-rays from 50 to 130 kV. The spectral compatibility of the LuAG:Ce crystal, with various existing optical detectors, was investigated after emission spectra measurements. Results were compared with previously published data for commercially available lutetium based and cerium doped crystals, such as, (Lu,Gd)2SiO5:Ce and Lu2SiO5:Ce, frequently used in medical imaging applications. Absolute efficiency was found maximum at 130 kVp for the 5 × 5 × 10 mm3 LuAG:Ce crystal (31.86 efficiency units-E.U). AE of the 10 × 10 × 10 mm3 LuAG:Ce crystal was found higher than both LGSO:Ce and LSO:Ce crystals (of equal dimensions). The emission spectrum of LuAG:Ce is excellent matched with the spectral sensitivities of photocathodes, charge coupled devices (CCD), non-passivated amorphous hydrogenated silicon photodiodes (a-Si:H) and complementary metal-oxide semiconductors (CMOS) microelectronic devices employed in radiation detection. Considering the higher luminescence efficiency values than currently used crystals and the spectral compatibility with the various photodetectors, LuAG:Ce single crystal could be considered for use in imaging detectors, such as, PET/CT scanners.

X-ray detectors are used in medical imaging for the representation of diagnostic information. Digital detector performance is evaluated through appropriate parameters in the spatial domain (i.e. contrast, noise or resolution) and in the frequency domain. Dental radiography is a domain of medical imaging. The purpose of this work is the examination of a commercially available digital dental imaging detector through spatial frequency domain parameters. The available detector was a commercially available image receptor SCHICK CDR, working in indirect mode that is a scintillator coupled to a Complementary Metal Oxide Semiconductor (CMOS) photoreceptor. The detector was irradiated at an X-ray system with 60 kVp and 70 kVp tube voltages utilized in intraoral radiography. The detector linearity, Modulation Transfer Function (MTF), Normalized Noise Power Spectrum (NNPS) and Detective Quantum Efficiency (DQE) were measured according to literature. The Entrance Surface Air Kerma (ESAK) was measured with an RTI PIRANHA X-ray multimeter. The images were evaluated as presented to the dentist by the detector software, in 12bit format. The resolution of the detector was found better than 100 μm. The DQE curves suggested optimum exposure conditions below 133 μGy.

This paper presents a new method for assessing the three-point-bending (3PB) strength of mortar beams in a non-destructive manner, based on neural network (NN) models. The models are based on the radial basis function (RBF) architecture and the fuzzy means algorithm is employed for training, in order to boost the prediction accuracy. Data for training the models were collected based on a series of experiments, where the cement mortar beams were subjected to various bending mechanical loads and the resulting pressure stimulated currents (PSCs) were recorded. The input variables to the NN models were then calculated by describing the PSC relaxation process through a generalization of Boltzmannn-Gibbs statistical physics, known as non-extensive statistical physics (NESP). The NN predictions were evaluated using k-fold cross-validation and new data that were kept independent from training; it can be seen that the proposed method can successfully form the basis of a non-destructive tool for assessing the bending strength. A comparison with a different NN architecture confirms the superiority of the proposed approach.

The aim of the present study was to design a microscopy image analysis (MIA) system for predicting the 5-year survival of patients with laryngeal squamous cell carcinoma, employing histopathology images of lesions, which had been immunohistochemically (IHC) stained for p63 expression. Biopsy materials from 42 patients, with verified laryngeal cancer and follow-up, were selected from the archives of the University Hospital of Patras, Greece. Twenty six patients had survived more than 5 years and 16 less than 5 years after the first diagnosis. Histopathology images were IHC stained for p63 expression. Images were first processed by a segmentation method for isolating the p63-expressed nuclei. Seventy-seven features were evaluated regarding texture, shape, and physical topology of nuclei, p63 staining, and patient-specific data. Those features, the probabilistic neural network classifier, the leave-one-out (LOO), and the bootstrap cross-validation methods, were used to design the MIA-system for assessing the 5-year survival of patients with laryngeal cancer. MIA-system accuracy was about 90 % and 85 %, employing the LOO and the Bootstrap methods, respectively. The image texture of p63-expressed nuclei appeared coarser and contained more edges in the 5-year non-survivor group. These differences were at a statistically significant level (p < 0.05). In conclusion, this study has proposed an MIA-system that may be of assistance to physicians, as a second opinion tool in assessing the 5-year survival of patients with laryngeal cancer, and it has revealed useful information regarding differences in nuclei texture between 5-year survivors and non-survivors.

The absolute luminescence efficiency (AE) of a calcium fluoride (CaF2:Eu) single crystal doped with europium was studied using X-ray energies met in general radiography. A CaF2:Eu single crystal with dimensions of 10 &times, 10 &times, 10 mm3 was irradiated by X-rays. The emission light photon intensity of the CaF2:Eu sample was evaluated by measuring AE within the X-ray range from 50 to 130 kV. The results of this work were compared with data obtained under similar conditions for the commercially employed medical imaging modalities, Bi4Ge3O12 and Lu2SiO5:Ce single crystals. The compatibility of the light emitted by the CaF2:Eu crystal, with the sensitivity of optical sensors, was also examined. The AE of the 10 &times, 10 mm3 CaF2:Eu crystal peaked in the range from 70 to 90 kV (22.22 efficiency units, E.U). The light emitted from CaF2:Eu is compatible with photocathodes, charge coupled devices (CCD), and silicon photomultipliers, which are used as radiation sensors in medical imaging systems. Considering the AE results in the examined energies, as well as the spectral compatibility with various photodetectors, a CaF2:Eu single crystal could be considered for radiographic applications, including the detection of charged particles and soft gamma rays.

Introduction Although T1 weighted spin echo (T1W SE) images are widely used to study anatomical details and pathologic abnormalities of the brain, its role in delineation of lesions and reduction of artifacts has not been thoroughly investigated. BLADE is a fairly new technique that has been reported to reduce motion artifacts and improve image quality. Objective The primary objective of this study is to compare the quality of T1-weighted fluid attenuated inversion recovery (FLAIR) images with BLADE technique (T1W FLAIR BLADE) and the quality of T1W SE images in the MR imaging of the brain. The goal is to highlight the advantages of the two sequences as well as which one can better reduce flow and motion artifacts so that the imaging of the lesions will not be impaired. Materials and methods Brain examinations with T1W FLAIR BLADE and T1W SE sequences were performed on 48 patients using a 1.5 T scanner. These techniques were evaluated by two radiologists based on: a) a qualitative analysis i.e. overall image quality, presence of artifacts, CSF nulling; and b) a quantitative analysis of signal-to-noise ratios (SNR), contrast-to-noise ratios (CNR) and Relative Contrast. The statistical analysis was performed using the Kruskal-Wallis non-parametric system. Results In the qualitative analysis, BLADE sequences had a higher scoring than the conventional sequences in all the cases. The overall image quality was better on T1W FLAIR BLADE. Motion and flow-related artifacts were lower in T1W FLAIR BLADE. Regarding the SNR measurements, T1W SE appeared to have higher values in the majority of cases, whilst T1W-FLAIR BLADE had higher values in the CNR and Relative Contrast measurements. Conclusion T1W FLAIR BLADE sequence appears to be superior to T1W SE in overall image quality and reduction of motion and flow-pulsation artifacts as well as in nulling CSF and has been preferred by the clinicians. T1W FLAIR BLADE may be an alternative approach in brain MRI imaging.

This work presents the non-symmetric fuzzy means algorithm which is a new methodology for training Radial Basis Function neural network models. The method is based on a non-symmetric fuzzy partition of the space of input variables which results to networks with smaller structures and better approximation capabilities compared to other state-of-the-art training procedures. The lower modeling error and the smaller size of the produced models become particularly important when they are used in online applications. This is demonstrated by integrating the model produced by the proposed algorithm in a Model Predictive Control configuration, resulting in better control performance and shorter computational times.

The aim of the present study was to examine the effect of scintillator material properties on the signal difference to noise ratio ( SdNR ) under X-ray imaging conditions. To this aim, SdNR was modelled in terms of scintillator material properties such as the quantum detection efficiency (QDE), the intrinsic energy conversion efficiency (ICE) and the light transmission efficiency (LTE). Scintillators were assumed to be in the form of scintillator layers (phosphor screens) with various thicknesses ranging from 70 to 110 mg/cm 2 . Data on the X-ray absorption and optical properties of the scintillators were either calculated from tabulated data, i.e. X-ray attenuation coefficients for QDE estimation, or were obtained from previous experimental studies. It was found that in a wide range of X-ray tube voltages the Gd 2 O 2 S:Tb scintillator produced higher SdNR values, while the CsI:Tl scintillator was better at lower voltages (below 65 kVp). It was additionally verified that, in the range of X-ray diagnostic energies, SdNR increases with the thickness of the scintillator layer screen. In conclusion, SdNR may be critically affected by scintillator properties and, hence, it may be significantly improved by appropriately selecting the type and thickness of the phosphor screen to be integrated into an imaging system.

This study presents the design and development of a novel mobile wireless system to be used for monitoring seismic events and related electromagnetic signals, employing smart mobile devices like personal digital assistants (PDAs) and wireless communication technologies such as wireless local area networks (WLANs), general packet radio service (GPRS) and universal mobile telecommunications system (UMTS). The proposed system enables scientists to access critical data while being geographically independent of the sites of data sources, rendering it as a useful tool for preliminary scientific analysis.

This work presents a comparison between direct and indirect neural control methods based on the radial basis function (RBF) architecture. As far as direct control schemes are concerned, a novel direct inverse neural RBF controller taking into account the applicability domain criterion (INCAD) is utilized. ? model predictive control (MPC) formulation based on RBF networks is tested as an example of indirect method. The performances of the two control schemes are evaluated and compared on a highly nonlinear control problem, namely control of a continuous stirred tank reactor (CSTR) with multiple stable and unstable steady states. Results show that the INCAD controller is able to provide satisfactory performance, while performing almost instant calculation of the control actions. MPC on the other hand, outperforms the INCAD in terms of speed of responses, due to the built-in optimization capability; however, the lengthy procedure of solving online the optimization problem impedes the practical use of MPC on systems with fast dynamics.

Background. P63 immunostaining has been considered as potential prognostic factor in laryngeal cancer. Considering that P63 is mainly nuclear stain, a possible correlation between the texture of P63-stained nuclei and the tumor’s grade could be of value to diagnosis, since this may be related to biologic information imprinted as texture on P63 expressed nuclei.Objective. To investigate the association between P63 stained nuclei and histologic grade in laryngeal tumor lesions.Methods. Biopsy specimens from laryngeal tumour lesions of 55 patients diagnosed with laryngeal squamous cell carcinomas were immunohistochemically (IHC) stained for P63 expression. Four images were digitized from each patient’s IHC specimens. P63 positively expressed nuclei were identified, the percentage of P63 expressed nuclei was computed, and 118 textural, morphological, shape, and architectural features were calculated from each one of the 55 laryngeal lesions. Data were split into the low grade (21 grade I lesions) and high grade (34 grade II and grade III lesions) classes for statistical analysis.Results. With advancing grade, P63 expression decreased, P63 stained nuclei appeared of lower image intensity, more inhomogeneous, of higher local contrast, contained smaller randomly distributed dissimilar structures and had irregular shape.Conclusion. P63 expressed nuclei contain important information related to histologic grade.

To design a pattern recognition (PR) system for discriminating between low- and high-grade laryngeal cancer cases, employing immunohistochemically stained, for p63 expression, histopathology images.The PR system was designed to assist in the physician's diagnosis for improving patient survival. The material comprised 55 verified cases of laryngeal cancer, 21 of low-grade and 34 of high-grade malignancy. Histopathology images were first processed for automatically segmenting p63 expressed nuclei. Fifty-two features were next extracted from the segmented nuclei, concerning nuclei texture, shape, and physical topology in the image. Those features and the Probabilistic Neural Network classifier were used to design the PR system on the multiprocessors of the Nvidia 580 GTX graphics processing unit (GPU) card using the Compute Unified Device Architecture parallel programming model and C++ programming language.PR system performance in classifying laryngeal cancer cases as low grade and high grade was 85.7% and 94.1%, respectively. The system's overall accuracy was 90.9%, using 7 features, and its estimated accuracy to "unseen" by the system cases was 80%.Optimum system design was feasible after employing parallel processing techniques and GPU technology. The proposed system was structured so as to function in a clinical environment, as a research tool, and with the capability of being redesigned on site when new verified cases are added to its repository.

This paper presents the development of a soft-sensor receiving as inputs Pressure Stimulated Current (PSC) characteristics in order to predict a critical mechanical property of cement-based materials, in a non-destructive manner. The soft-sensor is based on a Radial Basis Function (RBF) network that starts with an empty hidden layer and evolves its structure and synaptic weights as new data become available. Results have shown that the proposed approach can be used successfully to evolve a predictive tool based on input-output data, whereas it is superior compared to other adaptive modeling techniques.

This paper presents a nonlinear controller based on an inverse neural network model of the system under control. The neural controller is implemented as a Radial Basis Function (RBF) network trained with the powerful fuzzy means algorithm. The resulting controller is tested on a nonlinear DC motor control problem and the results illustrate the advantages of the proposed approach.

In this paper a novel variable selection method based on Radial Basis Function (RBF) neural networks and genetic algorithms is presented. The fuzzy means algorithm is utilized as the training method for the RBF networks, due to its inherent speed, the deterministic approach of selecting the hidden node centers and the fact that it involves only a single tuning parameter. The trade-off between the accuracy and parsimony of the produced model is handled by using Final Prediction Error criterion, based on the RBF training and validation errors, as a fitness function of the proposed genetic algorithm. The tuning parameter required by the fuzzy means algorithm is treated as a free variable by the genetic algorithm. The proposed method was tested in benchmark data sets stemming from the scientific communities of time-series prediction and medicinal chemistry and produced promising results.

In the Technological Educational Institution (T.E.I.) of Athens, new technologies are used for teaching electronic engineering modules for some time. This work presents the teaching of the module of power electronics by introducing a number of new methods. The educational portal, software simulations and electronic examinations support the teaching process and finally evaluate knowledge assimilation. Features and advantages of their implementation are presented and discussed.

In addition to existing non-destructive testing methods a novel technique is presented here. It is based on Dielectric Spectroscopy (DS) methodology for the verification of mechanical damages in geomaterial structures. Such techniques do not influence the material structure or properties, thus it can be re-examined with various methods. In this work damages are introduced in a geomaterial by uniaxial stress isothermally. The damage caused to marble samples and its influences on the dielectric loss angle were examined relative to stress. Results indicate that when stress produces microcracks then tan δ increases and a loss peak appears in the studied frequency range.