Medical Imaging Detection Research Articles

Luminescence Property of Rare-Earth Doped Bismuth-Borate Glasses

We fabricated rare-earth doped bismuth borate glasses by using melt-quench technique. Two different types glass samples of xBi2O3: (100-x)B2O3 (x=30 and 50) were made to compare the luminescence properties. We measured x-ray luminescence of Bi-glass by using a x-ray tube. Several dopants were doped into the Bi-glass to measure the x-ray luminescence such as CeO2, Nd2O3, Er2O3, Dy2O3, Pr2O3, Sm2O3, Ho2O3, Gd2O3 and CeF3. Among them, Dy2O3, Nd2O3 and Sm2O3 doped Bi-glass emitted luminescence. We measured emission spectrum of each samples. Dy2O3 doped bi-glass has emission band at 482nm, 575nm, 662nm and 765nm. Nd2O3 doped bi-glass have emission band at 895nm and Sm2O3 doped Bi-glass has emission band at 569nm, 598nm, 641nm and 705nm. Moreover, Bi-glass scintillators with high light yield with good radiation hardness and low cost can be applied in high energy and nuclear physics, medical imaging, homeland security and radiation detection.

Hybrid multi micropattern gaseous photomultiplier for detection of liquid-xenon scintillation

Gaseous PhotoMultipliers (GPM) are a very promising alternative of vacuum PMTs especially for large-size noble-liquid detectors in the field of Functional Nuclear Medical Imaging and Direct Dark Matter Detection. We present recent characterization results of a Hybrid-GPM made of three Micropattern Gaseous Structures; a Thick Gaseous Electron Multiplier (THGEM), a Parallel Ionization Multiplier (PIM) and a MICROMesh GAseous Structure (MICROMEGAS), operating in Ne/CF4 (90:10). Gain values close to 107 were recorded in this mixture, with 5.9keV x-rays at 1100mbar, both at room temperature and at that of liquid xenon (T=171K). The results are discussed in term of scintillation detection. While the present multiplier was investigated without photocathode, complementary results of photoextraction from CsI UV-photocathodes are presented in Ne/CH4 (95:5) and CH4 in cryogenic conditions.

Studying the luminescence efficiency of Lu2O3:Eu nanophosphor material for digital X-ray imaging applications

Scintillator materials are widely used in X-ray medical imaging detector applications, coupled with available photoreceptors like radiographic film or photoreceptors suitable for digital imaging like a-Si, charge-coupled devises (CCD), complementary metal-oxide-semiconductors (CMOS) and GaAs). In addition, scintillators can be utilized in non-medical imaging detectors such as industrial detectors for non-destructive testing (NDT) and detectors used for security purposes (i.e. airport luggage control). Image quality and dose burden in the above applications is associated with the amount of optical photons escaping the scintillator as well as the amount of optical photons captured by the photoreceptor. The former is characterized by the scintillator efficiency and the latter by the spectral matching between the emission spectrum of the scintillator and the spectral response of the photoreceptor. Recently, a scintillator material, europium-activated lutetium oxide (Lu2O3:Eu), has shown improved scintillating properties. Lu2O3:Eu samples of compact nanocrystalline non-agglomerated powder were developed in our laboratory using homogeneous precipitation from a water-toluene solution in the presence of polyvinyl alcohol as a surfactant. In order to test their light-emission properties, experimental measurements under the excitation of X-ray spectra with X-ray tube voltages between 50 kVp and 140 kVp were performed. This range of applied voltages is appropriate for X-ray radiology, NDT and security applications. Lu2O3:Eu was evaluated with respect to output yield and spectral compatibility of digital imaging photoreceptors (CCD-based, CMOS-based, amorphous silicon a:Si flat panels, ES20 and GaAs). High light yield and spectral compatibility increase the performance of the medical detector and reduce the dose burden to the personnel involved. In addition a theoretical model was used to determine the values for the Lu2O3:Eu optical photon light propagation parameters. The inverse diffusion length was found to be equal to 33 cm2/g. In addition Lu2O3:Eu was found to match well with several photoreceptors capable of digital imaging (i.e. GaAs).

QALT study of scintillating material in digital flat panels for medical imaging

QALT method (Quantitative Accelerated Life Test) is extensively used in industrial world to assess the reliability of components or systems under stresses, find major influent parameters and the laws of evolution of component or system properties. Such an approach was used in digital X-ray flat detectors for medical imaging to study the defect mechanism of scintillator under temperature and humidity. The scintillator was encapsulated as it can be in a detector to protect it from humidity. QALT experiments showed that the total quantity of light emitted by the scintillator does not decrease with aging time, so that sensitivity decrease will never be the failure mode for humid heat treatments. Structure size of material was also measured. A completely different behavior was found for the parameter controlling structure evolution depending on encapsulation type. Calculations show that the permeation coefficient of the seal used for encapsulation can modify greatly the apparent law of evolution of scintillator structure size.

Fabrication and Luminescent Properties of Eu3+-Doped Yttrium Lanthanum Oxide Transparent Ceramics

High-transparent Eu3+-doped yttrium lanthanum oxide ceramics were fabricated with nanopowders and the highest transmittance in the visible light wavelength region reaches 78%. The Eu3+-doped transparent ceramics exhibited a broad absorption band around 240 nm, a sharp red emission at 611 nm under X-ray excitation and the fluorescent decay time of 0.96 ms. It is expected to be a potential polycrystalline scintillation material for the applications in medical-imaging detectors.

Implementation of Computer Aided Diagnosis System Based on Parallel Approach of Ant Based Medical Image Segmentation

Problem statement: The aim of this study is to develop Computer Aided Diagnosis (CAD) system for the detection of brain tumor by using parallel implementation of ACO system for medical image segmentation applications due to the rapid execution for obtaining and extracting the Region of Interest (ROI) from the images for diagnostic purposes in medical field. Approach: For ROI segmentation, metaheuristic based Parallel Ant colony Optimization (PACO) approach has been implemented. The system has been simulated in the Mat lab for the parallel processing, using the master slave approach and information exchange. The scheme is tested up to 10 real time MRI brain images. Here parallelism is inherent in program loops, which focused on performing searching operation in parallel. Results: The computational results shows that parallel ACO systems uses the concept of the parallelization approach enabled the utilization of the intensity similarity measurement technique because of the capability of parallel processing. Conclusion: Medical image segmentation and detection at the early stage played vital roles for many health-related applications such as medical diagnostics, drug evaluation, medical research, training and teaching. Due to the rapid progress in the technologies for segmenting digital images for diagnostic purposes in medical field parallel Ant based CAD system are technologically feasible for Medical Domain which will certainly reduce the mortality rate.

Comparative Study of HgI2, PbI2 and TlBr Films Aimed for Ionizing Radiation Detection in Medical Imaging

ABSTRACTWide bandgap semiconductor films were obtained by spray pyrolysis, thermal evaporation and casting. These films were characterized under similar conditions in order to compare their structures, surface morphology and photocurrent properties. All films show either a crystalline or a polycrystalline structure. SEM pictures of sprayed films present holes and fissures and non-total covering of the substrate. The photoresponse was obtained for evaporated TlBr films, HgI2 casted with polystyrene (PS) scaffold, sprayed and evaporated PbI2 films. The photo to dark current ratio is discussed as well as the difference of photo to dark current at an electric field of 100 V/cm. The discussion also focuses on a future optimized material.

Luminescence and Scintillation Characteristics of ${\rm Rb}_{2}{\rm LiCeBr}_{6}$ Single Crystal

Luminescence and scintillation properties of Rb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> LiCeBr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> single crystal are presented. This is a new elpasolite scintillation material and is grown by vertical Bridgman technique. Under X-ray excitation, Ce <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> luminescence is observed between 365 and 415 nm. An energy resolution of 6.3% (FWHM) is obtained for the 662 keV full γ-ray absorption peak. The sample crystal shows good light yield of 33 000 ph/MeV of absorbed γ -ray energy. The sample crystal also shows 5.0% nonproportionality in the 31 to 1333 keV range. The luminescence decay time curve can be characterized by two decay time components with decay time constants of 55 ns (87%) and 284 ns (13%), respectively. Scintillation properties indicate that this compound can be an attractive candidate for medical imaging and radiation detection applications.

The Role of Pattern Recognition in Computer-Aided Diagnosis and Computer-Aided Detection in Medical Imaging: A Clinical Validation

The idea to use texture analysis in medical imaging has been considered since the early 1970s. However, the exciting evolution of both texture analysis algorithms and computer technology revived researchers' interest in applications for medical imaging in recent years. Technical innovations in medical cross-sectional imaging have opened up new vistas for the exploration of the human body, enabling both high spatial and temporal resolution. On Difficulties Caused by Missing Reference Image Datasets One of the main problems in the development of systems for the analysis of medical images or segmentation algorithms is the set of images that is used for both the development and the testing of the system. This paper proposes a diagnostic scheme follows a familiar two-step approach. Initially, textural information is extracted from the image. Subsequently, the extracted information is fed into a decisional algorithm that is designed to perform the diagnostic task.The talk covers new methods for pattern recognition and computer-aided diagnosis in the field of MRI, such as functional MRI for human brain mapping, therapy control by automatic lesion detection in multiple sclerosis, and new approaches to breast cancer diagnosis in MRI mammography. In the light of such innovative techniques for pattern recognition in biomedicine, the increasing demand for publicly accessible validation platforms is emphasized. With image texture analysis in the role of the visual perceptional function, the process of feature extraction and image coding is achieved. The extracted features can now be merged into a diagnosis by using a decision-making algorithm, with choices that range from the rule-based models to the traditional statistical analysis to the more popular (and often more successful) artificial intelligence techniques, such as neural networks and genetic algorithms. By using image texture analysis as the preprocessing step in CAD schemes, the input generation process is automated and, therefore, is reproducible and robust. Some techniques represent texture on the basis of the spectral properties of an image. Others are model-based techniques that analyze texture by identifying an appropriate model that reflects the prior beliefs and knowledge about the type of images to be analyzed. There are textural features that describe local image statistics and others that describe global statistics.

Correction to "Status of Direct Conversion Detectors for Medical Imaging With X-Rays" [Aug 09 1800-1809

In the above titled paper (ibid., vol. 56, no. 4, pp. 1800-1809, Aug. 09), an error appeared in Table III. A corrected version of Table III is presented here.

Origin of Radiation‐Induced Degradation in Polymer Solar Cells

AbstractPolymer solar cells have been shown to degrade under X‐rays. Here, in situ polymer photovoltaic performance and recombination lifetimes are measured and it is found that charge accumulation is the primary reason for degradation of solar cells. This is affected by the mixing ratio of donor and acceptor in the bulk heterojunction. Both a quantitative understanding and the physical model of the degradation mechanism are presented. Understanding of the degradation mechanism is extended in polymer donor–acceptor bulk heterojunction systems to propose a material combination for making radiation hard diodes that can find important application in fields ranging from memory arrays to organic X‐ray detectors for medical imaging.

Study on Crystal Growth and Scintillation Characteristics of Cs$_{2}$ LiCeCl$_{6}$

In this work, we present the crystal growth and scintillation properties of our newly developed scintillation crystal, Cs <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> LiCeCl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> , for a γ-ray spectroscopy. This scintillation crystal is grown by using the vertical Bridgman method. The crystal of this material belongs to the elpasolite family characterized by a cubic structure and potentially can be easily grown in large volumes. Under the X-ray excitation, cerium emission band is observed to peak at 385 nm and 405 nm. An energy resolution (full width at half maximum over the peak position) of 5.5% was observed for the 662 keV full absorption peak. We measured an absolute light yield of 22 000 photons/MeV of absorbed η -ray energy. The crystal shows three main scintillation decay time components of 101 ns (42%), 557 ns (35%) and 2.9 μs (23%). This material is highly hygroscopic and special attention was paid during data taking and handling processes. We believe that the Cs <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> LiCeCl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> crystal can be a promising material for medical imaging and radiation detection. Moreover due to the presence of Li ions, this scintillation crystal can also be a possible candidate for thermal neutron detection.

The Growth and Characterization of the Cerium Contained Inorganic Halide Scintillators

A report on the crystal growth, luminescence and scintillation characteristics of two developed scintillators, CsCe2Cl7 and Cs2NaCeCl6 are presented. CsCe2Cl7 is a new scintillation material. These crystals were grown by the Czochralski pulling technique. The X-ray diffraction technique was used to verify the structure of crystals. Under the X-ray excitation emission, the CsCe2Cl7 showed a broad emission band in the wavelength range from 370 to 470 nm while the Cs2NaCeCl6 crystal showed a spectrum in the wavelength range from 370 to 440 nm. The energy resolutions (FWHM of peak position) for the 662 keV full energy peak of 5.5% and 8.3% were observed at room temperature for the CsCe2Cl7 and Cs2NaCeCl6 crystals, respectively. The scintillation decay time measurement curves showed that, CsCe2Cl7 crystal has a single exponential decay function with a decay time of 50 ns. The Cs2NaCeCl6 crystal exhibited three main decay time components, a short component with a decay time constant of 91 ns and 36% intensity, an intermediate component with a decay time constant of 601 ns and intensity 33%, followed by a long component with a 3.2 µs decay time constant and an intensity of 31% of the total light yield. On the basis of the scintillation results of these materials grown, it is believe that these scintillation crystals can find a place in medical imaging and radiation detection system.

Cs 2LiGdCl 6 (Ce): New scintillation material

We investigated the scintillation properties of Cs 2LiGdCl 6:Ce 3+ as a function of the Ce concentration. X-ray excited luminescence spectra of the scintillation material showed broad emission bands between 360 and 460 nm, with two overlapping peaks, due to the d→f transitions on Ce 3+ ions. The samples provide good scintillation results. The energy resolution was found to be 5.0% (FWHM) at 662 keV for 10% Ce sample. Under γ-ray excitation, Cs 2LiGdCl 6:Ce 3+ showed three exponential decay time components of about 130–200 ns decay time constant. The light output of the investigated samples was 20,000 photons/MeV for a 10% Ce concentration. The light output deviation from the linear response is within 7% between the energy range of 31 and 1333 keV. Overall, the scintillation properties confirm that Cs 2LiGdCl 6:Ce 3+ single crystal is a promising candidate for medical imaging and radiation detection.

Synthesis and luminescence of CePO4:Tb/LaPO4 core/sheath nanowires

CePO4:Tb/LaPO4 nanowires with a core/sheath architecture have been successfulsynthesized by a facile aqueous chemical method mediated by originalCePO4:Tb aggregation seeds. The seed crystals serve as both a luminescence center and a nucleation sitefor epitaxial growth. The seed nanocrystals have an irregular sphere-like shape with an averagesize of around 6.8 nm and a narrow size distribution. When the seed crystals are coated withLaPO4, the resultingcore/sheath CePO4:Tb/LaPO4 nanowires have mean diameters of about 7.6 nm and lengths up to331 nm. Both photo- and x-ray luminescence demonstrate that theLaPO4 coating increases the luminescence efficiency. These core/sheath structured nanowires mayfind potential applications in solid state lighting, medical imaging and radiation detection.

Nanoparticle-labeled stem cells: a novel therapeutic vehicle

Nanotechnology has been described as a general purpose technology. It has already generated a range of inventions and innovations. Development of nanotechnology will provide clinical medicine with a range of new diagnostic and therapeutic opportunities such as medical imaging, medical diagnosis, drug delivery, and cancer detection and management. Nanoparticles such as manganese, polystyrene, silica, titanium oxide, gold, silver, carbon, quantum dots, and iron oxide have received enormous attention in the creation of new types of analytical tools for biotechnology and life sciences. Labeling of stem cells with nanoparticles overcame the problems in homing and fixing stem cells to their desired site and guiding extension of stem cells to specific directions. Although the biologic effects of some nanoparticles have already been assessed, information on toxicity and possible mechanisms of various particle types remains inadequate. The aim of this review is to give an overview of the mechanisms of internalization and distribution of nanoparticles inside stem cells, as well as the influence of different types of nanoparticles on stem cell viability, proliferation, differentiation, and cytotoxicity, and to assess the role of nanoparticles in tracking the fate of stem cells used in tissue regeneration.

Optical simulation of monolithic scintillator detectors using GATE/GEANT4

Much research is being conducted on position-sensitive scintillation detectors for medical imaging, particularly for emission tomography. Monte Carlo simulations play an essential role in many of these research activities. As the scintillation process, the transport of scintillation photons through the crystal(s), and the conversion of these photons into electronic signals each have a major influence on the detector performance; all of these processes may need to be incorporated in the model to obtain accurate results. In this work the optical and scintillation models of the GEANT4 simulation toolkit are validated by comparing simulations and measurements on monolithic scintillator detectors for high-resolution positron emission tomography (PET). We have furthermore made the GEANT4 optical models available within the user-friendly GATE simulation platform (as of version 3.0). It is shown how the necessary optical input parameters can be determined with sufficient accuracy. The results show that the optical physics models of GATE/GEANT4 enable accurate prediction of the spatial and energy resolution of monolithic scintillator PET detectors.

Scintillation mechanisms of inorganic materials: From crystal characteristics to scintillation properties

Finding new inorganic scintillator crystals with better performance for demanding applications, such as high-energy physics, medical imaging, and radiation detection, has been a long-standing challenge. Thanks to an intensive interdisciplinary effort between theoreticians, experimentalists and crystal growers, current scintillator performances are reaching the intrinsic limits imposed by the crystal. However, demand continues for more efficient scintillators with higher light output, better energy resolution and lower cost of production. This article discusses the basic concepts of scintillation in inorganic materials, focusing on how physics can provide pathways to assist in scintillator discovery.

Scintillation properties of Cs2LiGdCl6: Ce3+

Abstract In this communication, we investigated the scintillation properties of Cs 2 LiGdCl 6 :10% Ce 3+ single crystal. This scintillation crystal is grown by using the vertical Bridgman technique. X-rays induced emission spectra show that, Cs 2 LiGdCl 6 :10% Ce 3+ emits into the Ce 3+ band, spanning from 365 nm to 450 nm wavelengths. Under γ-ray excitation, the sample crystal shows three main decay time components of 129 ns (51%), 573 ns (32%) and 8.9 μs (17%). It offers an energy resolution of 5.0% (FWHM) for the 662 keV full absorption peak at room temperature. We measured an absolute light yield of 20,000 photons/MeV of absorbed γ-ray energy. We found that with a little exposure to the air, the scintillation properties of the Cs 2 LiGdCl 6 :10% Ce 3+ crystal deteriorate, which is attributed to the highly hygroscopic nature of this material. We believe that the Cs 2 LiGdCl 6 :10% Ce 3+ crystal can be a promising material for medical imaging and radiation detection. Moreover due to the presence of Li and Gd constituents, this scintillation crystal can also be the possible candidate for thermal neutron detection.

Status of Direct Conversion Detectors for Medical Imaging With X-Rays

Imaging detectors for medical X-ray and computed tomography (CT) applications have undergone many improvements and technology changes over time. But most (dynamic) detectors sold in this field still rely on indirect conversion, using scintillators and photodiodes to convert the X-ray quanta ultimately into electrical signals. Direct conversion detectors promise very high spatial resolution and high signal-to-noise ratios. Some direct conversion materials may allow for counting or even energy resolving detection of the X-ray quanta. Based on this, for example spectrally resolving CT systems are becoming an interesting option for the next decade. This contribution highlights the requirements of advanced medical X-ray and CT imaging and reviews examples of status and progress in the field. The emphasis is on the direct conversion sensors for pixelated detectors, but considerations on read-out concepts and on associated challenges such as interconnects will also be presented. Finally, the most burning issues, such as count rate limitations and polarization effects, will be discussed from an application point of view.