X-ray Tube Voltage Research Articles

Air Kerma Calculation in Diagnostic Medical Imaging Devices Using Group Method of Data Handling Network

The air kerma, which is the amount of energy given off by a radioactive substance, is essential for medical specialists who use radiation to diagnose cancer problems. The amount of energy that a photon has when it hits something can be described as the air kerma (the amount of energy that was deposited in the air when the photon passed through it). Radiation beam intensity is represented by this value. Hospital X-ray equipment has to account for the heel effect, which means that the borders of the picture obtain a lesser radiation dosage than the center, and that air kerma is not symmetrical. The voltage of the X-ray machine can also affect the uniformity of the radiation. This work presents a model-based approach to predict air kerma at various locations inside the radiation field of medical imaging instruments, making use of just a small number of measurements. Group Method of Data Handling (GMDH) neural networks are suggested for this purpose. Firstly, a medical X-ray tube was modeled using Monte Carlo N Particle (MCNP) code simulation algorithm. X-ray tubes and detectors make up medical X-ray CT imaging systems. An X-ray tube's electron filament, thin wire, and metal target produce a picture of the electrons' target. A small rectangular electron source modeled electron filaments. An electron source target was a thin, 19,290 kg/m3 tungsten cube in a tubular hoover chamber. The electron source-object axis of the simulation object is 20° from the vertical. For most medical X-ray imaging applications, the kerma of the air was calculated at a variety of discrete locations within the conical X-ray beam, providing an accurate data set for network training. Various locations were taken into account in the aforementioned voltages inside the radiation field as the input of the GMDH network. For diagnostic radiology applications, the trained GMDH model could determine the air kerma at any location in the X-ray field of view and for a wide range of X-ray tube voltages with a Mean Relative Error (MRE) of less than 0.25%. This study yielded the following results: (1) The heel effect is included when calculating air kerma. (2) Computing the air kerma using an artificial neural network trained with minimal data. (3) An artificial neural network quickly and reliably calculated air kerma. (4) Figuring out the air kerma for the operating voltage of medical tubes. The high accuracy of the trained neural network in determining air kerma guarantees the usability of the presented method in operational conditions.

Low energy X-ray dosimeter based on LYSO:Ce fluorescent powder.

Cerium-doped lutetium yttrium orthosilicate (LYSO:Ce) powder has been synthesized by the co-precipitation method. The influence of the Ce3+ doping concentration on the lattice structure and luminescence characteristics of LYSO:Ce powder was investigated by X-ray diffraction (XRD) and photoluminescence (PL). The XRD measurement indicates that the lattice structure of LYSO:Ce powder was not changed by doping ions. PL results show that LYSO:Ce powder has better luminescence performance when the Ce doping concentration is 0.3mol%. In addition, the fluorescence lifetime of the samples was measured, and the results show that LYSO:Ce has a short decay time. The radiation dosimeter was prepared by LYSO:Ce powder with a Ce doping concentration of 0.3mol%. Radioluminescence properties of the radiation dosimeter also were studied under X-ray irradiation at doses from 0.03 to 0.76Gy, with dose rate from 0.09 to 2.284Gy/min. The results show that the dosimeter has a certain linear relationship response and stability. The radiation responses of the dosimeter at different energies were obtained under X-ray irradiation with X-ray tube voltages ranging from 20 to 80kV. The results show that the dosimeter has a certain linear relationship response in the low energy range of radiotherapy. These results indicate the potential application of LYSO:Ce powder dosimeters in remote radiotherapy and online radiation monitoring.

A comparative study between pure bismuth/tungsten and the bismuth tungsten oxide for flexible shielding of gamma/X rays

Thermoplastic vulcanizate based flexible W/Bi and bismuth tungsten oxide composites with different doping ratios from 20% to 100% are successfully fabricated. The ray attenuation abilities of the composites are determined at X-ray tube voltages of 80 KVp–120 KVp, and at gamma rays of 59 keV, 122 keV, 343 keV and 960 keV. The surface morphology and elements mapping of W/Bi and bismuth tungsten oxide particles within the polymer have confirmed a more uniform dispersion of bismuth tungsten oxide than W/Bi. Shielding parameters such as transmittance T, mass/linear attenuation coefficients μm and μ, as well as lead equivalent δPb are investigated experimentally and numerically by Monte Carlo code NECP-MCX as well as XCOM program. The transmittance of γ ray decreases exponentially with the areal density of the functional particles, and the best shielding of X-ray goes to 100 KVp tube voltage, followed by 80 KVp and 120 KVp. A comparison of the two series of composites are made that W/Bi always has advantages over bismuth tungsten oxide in attenuation coefficients and lead equivalent, because the extra containing oxygen atoms in bismuth tungsten oxide crystal actually provide very weak additional shielding. Test of mechanical property also reflects the advantage of using pure W/Bi over bismuth tungsten oxide in flexibility. As substitutes for Pb containing materials, these two types of composites could be of potential use in medical diagnosis, interventional surgery, or biological radiation protection, etc.

UVA-emitting composite film based on LaB3O6:Ce3+ phosphor for X-ray imaging

A series of UVA-emitting LaB3O6:Ce3+ phosphors and La0.96Ce0.04B3O6/PMMA films were prepared. The calcining temperature, activator concentration and PL test temperature were studied for the luminescence properties of the phosphor. And the effect of phosphor content on transmittance and X-ray radiation capacity of the composite films was also studied. The results show that LaB3O6:Ce3+ emits continuous double peaks at 358 nm and 380 nm when excited at 333 nm, the fluorescence lifetime is about 10 ns, and the luminescence intensity at 150 °C is 73.71% of that at room temperature, which can be used as phosphors for UV phototherapy applications. Under X-ray excitation, the integrated intensity of the La0.96Ce0.04B3O6/PMMA composite film has a good linear relationship with the X-ray tube current and tube voltage, and the X-ray imaging of a car key taken by La0.96Ce0.04B3O6/PMMA composite film has good signal-to-noise ratio, which can be used for X-ray detection and imaging.

Application of multispectral computed tomography for the characterisation of natural graphite

The established mineralogical and chemical analysis methods for graphite ores require complex sample preparation. Moreover, they do not produce 3D images of the polymineralic rock structure and texture. The lack of 3D information can lead to an erroneous assessment of the quality-determining properties of graphite ores, such as graphite flake size (grain size), graphite flake size distribution, and impurities. Therefore, there is a need to obtain 3D information from graphite ores and concentrates. Industrial computed tomography (CT or single-spectrum CT) is a unique technique that enables the examination of rocks in the 3D regime. The challenge in CT analysis of ores is the different absorption properties of mineral phases present. Low X-ray tube generator voltages lead to pronounced artefacts (volume defects) if highly absorbing gangue phases (e.g. iron sulfides) are present. Therefore, high X-ray tube voltages must be applied. However, graphite and associated gangue minerals, as well as contained cracks and voids in the ore, can exhibit similar absorption properties at higher generator energies (above 120 kV). Multispectral CT (MSP-CT) measurements offer a minimisation of CT artefacts and an increase in grey value contrasts. This work investigates the application of the MSP-CT measurements, significantly improving mineral differentiation.

Non-Toxic and Flexible Radiation-Shielding Composites Based on Natural Rubber Containing Elemental W Fillers for Efficient Shielding against X/γ-rays

Conventional radiation-shielding composites usually contain lead, which results in high toxicity and poor portability. Tungsten (W) is an ideal radiation-shielding element that can replace lead due to its high atomic number and non-toxicity. In this work, radiation-shielding composites were prepared using natural rubber (NR) as a matrix and three different particle size powders, namely W, WO3 and WC, as fillers. The results show that, for X-rays, the linear attenuation coefficient of radiation-shielding composites based on natural rubber containing WC with a particle size of 50 μm (50 WC/NR) is 27.005 cm−1 at an X-ray tube voltage of 40 kV, which is more than 14 times the linear attenuation coefficient of NR. For γ-rays, a linear attenuation coefficient of 50 WC/NR achieves 8.320 cm−1 at 81 keV, which is over 55 times the linear attenuation coefficient of NR. In addition, 50 WC/NR had the highest elongation at break at 548.989% and had the lowest hardness at 62 HA. In summary, 50 WC/NR can be used as an alternative to traditional radiation-shielding materials containing lead and has wide application prospects.

A Quantitative Method for the Composition of 7B05 Cast-Rolled Aluminum Alloys Based on Micro-Beam X-ray Fluorescence Spectroscopy and Its Application in Element Segregation of Recrystallization

Microscopic content segregation is among the important reasons for the anisotropy of mechanical properties in the cast-rolled sheets of the 7B05 aluminum alloy. It is of great significance to study the uniformity of aluminum alloys in terms of the microscopic composition and structure. In this study, a precise method for composition quantification based on micro-beam X-ray fluorescence spectroscopy is established by parameter optimization and a calibration coefficient. Furthermore, this method was applied for exploring and quantifying the relationship between recrystallization and deformation microstructures. The results show that the comprehensive measurement effects of all elements are the best when the X-ray tube voltage is 50 kV, the current is 150 μA, and the single-pixel scanning time is 100 ms. After verification, the sum of differences between the measured values and the standard values for all elements using the calibration coefficient is only 0.107%, which confirms the accuracy of the optimized quantitative method. Three types of segregation indexes in national standards were used to capture small differences, and finally ensure that the segregation degrees of elements are Ti > Fe > Cr > Cu > Mn > Zr > Zn > Al. The quantitative segregation results obtained by the spatial-mapping method show that the difference in the content of Al and Zn is approximately 0.2% between the recrystallization region and the deformation region, the difference in the content of Fe and Ti is 0.018% and 0.013%, the difference in the content of Cr, Cu and Zr is approximately 0.01%, and the difference in the content of Mn is not obvious, only 0.004%.

Metal Artifact Reduction in Dental CBCT Images Using Direct Sinogram Correction Combined with Metal Path-Length Weighting.

Metal artifacts in dental computed tomography (CT) images, caused by highly X-ray absorbing objects, such as dental implants or crowns, often more severely compromise image readability than in medical CT images. Since lower tube voltages are used for dental CTs in spite of the more frequent presence of metallic objects in the patient, metal artifacts appear more severely in dental CT images, and the artifacts often persist even after metal artifact correction. The direct sinogram correction (DSC) method, which directly corrects the sinogram using the mapping function derived by minimizing the sinogram inconsistency, works well in the case of mild metal artifacts, but it often fails to correct severe metal artifacts. We propose a modified DSC method to reduce severe metal artifacts, and we have tested it on human dental images. We first segment the metallic objects in the CT image, and then we forward-project the segmented metal mask to identify the metal traces in the projection data with computing the metal path length for the rays penetrating the metal mask. In the sinogram correction with the DSC mapping function, we apply the weighting proportional to the metal path length. We have applied the proposed method to the phantom and patient images taken at the X-ray tube voltage of 90 kVp. We observed that the proposed method outperforms the original DSC method when metal artifacts were severe. However, we need further extensive studies to verify the proposed method for various CT scan conditions with many more patient images.

Technical note: Water-equivalent thickness of Superflab bolus material at diagnostic x-ray energies.

The purpose of this work was to determine the water-equivalent thickness of Superflab bolus material for narrow and broad field-of-view (FOV) x-ray geometries at diagnostic x-ray energies. Transmission measurements were performed for incremental thicknesses of Superflab bolus material and water in narrow and broad FOV x-ray geometries. The transmission data was fit to a non-linear model for x-ray transmission - the Archer model. Water-equivalent thickness of Superflab was calculated based upon fitting parameters to transmission curves for 75, 95, and 115kV x-ray tube voltages. Measured x-ray transmission factors for water and Superflab were used to determine the water equivalence of Superflab. For all x-ray tube voltages and geometries, the water equivalence of Superflab was greater than one, indicating that Superflab is more attenuating than water. This effect was stronger for broad FOV geometries. At 95kV, 30cm of Superflab corresponded to 32.0cm of water in the narrow FOV geometry, and 34.3cm of water in the broad FOV geometry. The Archer model fitting parameters and Superflab water equivalence are reported for all x-ray beam conditions explored in this work. Superflab bolus material is more attenuating than water at diagnostic x-ray energies. The Archer model and its respective fitting parameters reported in this work may be used to estimate the water-equivalent thickness of Superflab for diagnostic x-ray spectra.

Proposing Intelligent Approach to Predicting Air Kerma within Radiation Beams of Medical X-ray Imaging Systems.

The air kerma is a key parameter in medical diagnostic radiology. Radiologists use the air kerma parameter to evaluate organ doses and any associated patient hazards. The air kerma can be simply described as the deposited kinetic energy once a photon passes through the air, and it represents the intensity of the radiation beam. Due to the heel effect in the X-ray sources of medical imaging systems, the air kerma is not uniform within the X-ray beam's field of view. Additionally, the X-ray tube voltage can also affect this nonuniformity. In this investigation, an intelligent technique based on the radial basis function neural network (RBFNN) is presented to predict the air kerma at every point within the fields of view of the X-ray beams of medical diagnostic imaging systems based on discrete and limited measured data. First, a diagnostic imaging system was modeled with the help of the Monte Carlo N Particle X version (MCNPX) code. It should be noted that a tungsten target and beryllium window with a thickness of 1 mm (no extra filter was applied) were used for modeling the X-ray tube. Second, the air kerma was calculated at various discrete positions within the conical X-ray beam for tube voltages of 40 kV, 60 kV, 80 kV, 100 kV, 120 kV, and 140 kV (this range covers most medical X-ray imaging applications) to provide the adequate dataset for training the network. The X-ray tube voltage and location of each point at which the air kerma was calculated were used as the RBFNN inputs. The calculated air kerma was also assigned as the output. The trained RBFNN model was capable of estimating the air kerma at any random position within the X-ray beam's field of view for X-ray tube voltages within the range of medical diagnostic radiology (20-140 kV).

Al2O3:C optically stimulated luminescence dosimetry for evaluation of potential factors contributing to entrance skin doses received by liver cancer patients undergoing Transarterial Chemoembolization

Transarterial Chemoembolization (TACE) has been accepted as an effective technique that can be practically used for liver cancer treatment due to its outstanding benefits for patients with large, infiltrative, and multifocal tumors that cannot be surgically removed. However, this invasive image-guided technique may potentially result in higher radiation doses than general diagnostic radiology. Radiation-induced skin injury caused by excessive exposure to X-rays during fluoroscopically guided procedures has been previously reported. Therefore, dose assessment during TACE examination is relevant to minimize radiological hazards and reduce patient distress.The study aims to 1) quantify the magnitude of radiation doses received in TACE treatments, 2) evaluate potential factors contributing to an increase of the entrance skin dose, and 3) demonstrate an improved image-guided procedure for reducing radiation doses while maintaining high X-ray image quality. The study was carried out employing an anthropomorphic phantom to determine radiation dose using a standard commercial optically stimulated luminescence dosimeter (OSLD). Experimental data was collected from 370 patients under three specific image-guided techniques. They include 1) abdomen frontal 3 fps procedure where a pathway of blood flow was created using an image acquisition rate of three frames per second (fps), 2) navigation where a blood vessel roadmap was created with subtraction of bones and organs, and 3) fluoroscopy where X-ray beams were continuously delivered to a target for creating real-time images with no interference removed. Analysis of variance was used to demonstrate the difference of the mean entrance skin doses (ESDs) among the three imaging techniques. A multiple regression model was also used to investigate potential factors contributing to the increased ESDs.The study confirms that the ESDs received by TACE patients using these three imaging techniques are not significantly different. Moreover, the statistical-based model shows that the five main factors obtained from the exposure parameters and patient dosimetric data contribute to the patient ESDs. They include 1) the dose area product (DAP), 2) fluoroscopy time, 3) X-ray tube voltage, 4) X-ray tube current, and 5) total diagnostic images. All information is reported based on the machine DICOM-RDSR (Digital Imaging and Communication in Medicine – Radiation Dose Structured Report) data after completed examinations. Finally, the ANOVA test confirms that this simplified model can be used to estimate the radiation doses received by TACE patients, accounting for a 95% confidence interval.

Modified Bismuth Nanoparticles: A New Targeted Nanoprobe for Computed Tomography Imaging of Cancer.

Objective Recently, development of multifunctional contrast agent for effective targeted molecular computed tomography (CT) imaging of cancer cells stays a major problem. In this study, we explain the ability of Triptorelin peptide-targeted multifunctional bismuth nanoparticles (Bi2S3@ BSA-Triptorelin NPs) for molecular CT imaging. Materials and Methods In this experimental study, the formed nanocomplex of Bi2S3@ BSA-Triptorelin NPs was characterized using different methods. The MTT cytotoxicity test was performed to determine the appropriate concentration of nanoparticles in the MCF-7 cells. The X-ray attenuation intensity and Contrast to Noise Ratio (CNR) of targeted and non-targeted nanoparticles were measured at the concentrations of 25, 50, and 75 µg/ml and X-ray tube voltages of 90, 120 and 140 kVp. Results We showed that the formed Bi2S3@ BSA-Triptorelin NPs with a Bi core size of approximately ~8.6 nm are nontoxic in a given concentration (0-200 µg/ml). At 90, 120, and 140 tube potentials (kVp), the X-ray attenuation of targeted cells were 1.35, 1.36, and 1.33-times, respectively, more than non-targeted MCF-7cells at the concentration of 75 μg/ml. The CNR values at 90, 120, and 140 kVp tube potentials were 171.5, 153.8 and 146.3 c/ϭ, respectively. ConclusionThese findings propose that the diagnostic nanocomplex of Bi2S3@ BSA-Triptorelin NPs can be applied as a good contrast medium for molecular CT techniques.

The Evaluation of Contrast-to-Noise Ratio in CT Images Using Different Parameters of Gold Nanoparticles versus Omnipaque

Purpose: Gold Nanoparticles (GNPs) with high density and an atomic number have lately been proposed as an alternative contrast agent for Computed Tomography (CT).
 Materials and Methods: In the present study, the Contrast-to-Noise Ratio (CNR) of GNPs from various shapes, sizes, concentrations, and surface chemistry was compared with an iodine contrast agent using CT at different X-ray tube voltages and concentrations.
 Results: Our findings showed that GNPs in various concentrations, shapes, sizes, and X-ray tube energies from 80 to 140 kVp revealed greater image CNR than iodinated contrast media (Omnipaque). Smaller spherical GNPs (13 nm) had greater CNR than larger ones (60 nm) and Gold Nanorods )GNRs( with a larger Aspect Ratio (AR) represented excellent effect on CNR. In addition, Polyethylene Glycol (PEG) covering on GNRs decreased CNR. We observed image CNR was increased using increasing in kVp and concentration.
 Conclusion: Smaller spherical GNPs can be proposed as a potential candidate as a future contrast agent alternative to iodinated contrast media.

Evaluation of Micro- and Nano-Bismuth(III) Oxide Coated Fabric for Environmentally Friendly X-Ray Shielding Materials

This research focuses on the development of environmentally friendly textile-based shielding composites, from micro-sized and nanosized Bi2O3 particles, against ionizing radiation. Polyester fabric dyne-coated with either micro- or nano-Bi2O3 particles shields some X-rays but the effectiveness is poor. With only ∼58% uptake of micro-sized Bi2O3 particles dyeing on polyester fabric, the insufficient amount of Bi2O3 leaded to the low density of particles, resulting in only 30% of X-ray shielding at 80 kVp. Cotton fabric coated with either micro- or nano-Bi2O3/poly(vinyl alcohol) (PVA) composites, on the other hand, demonstrated the capacity to attenuate X-ray generated by high diagnostic X-ray tube voltages of 70–100 kVp, in compliance with medical protection requirements. The X-ray attenuation performance of cotton fabric coated with either micro-Bi2O3/PVA or nano-Bi2O3/PVA nanocomposite decreased progressively with increasing tube acceleration voltages, however their ionizing radiation-shielding performance enhanced with the number of fabric layers. Interestingly, for all X-ray tube voltages evaluated, the micro-Bi2O3/PVA composite outperformed the nano- Bi2O3/PVA composite in terms of X-ray shielding. At a weight ratio of 66.7% Bi2O3, 10 layers of cotton fabric coated with micro- Bi2O3/PVA composite can attenuate 90, 85, and 80% of X-ray photons at 70, 80, and 100 kVp, respectively. As a result, these less harmful X-ray shielding materials have the potential to replace lead-based composites, which are highly toxic to human health and have negative environmental consequences.

Chemically bonded tungsten-based polymer composite for X-rays shielding applications

Lead-free metal-polymer composite based X-ray shielding apparel has been of great concern in recent years due to its flexibility, less toxicity, lightweight, etc. The conventional metal-polymer composites based apparels suffers from non-uniform attenuation due to the non-uniform distribution of fillers in the polymer matrix. In this work, efforts were made to address this drawback by developing a chemically bonded metal-polymer composite by incorporating tungsten trioxide (WO3) solution in the blend of polyvinyl alcohol and polyvinyl pyrrolidone. Developed composites were characterized and their X-ray attenuation properties were determined using the X-ray tube voltage of 50–140 kV. The XRD and SEM analyses revealed the formation of the sodium tungstate (Na2WO4.2H2O) phase and its uniform distribution in the polymer matrix, respectively. FT-IR and XPS data showed the formation of a coordinate bond between the W and polymer matrix, which is responsible for the uniform distribution of W-based filler. The polymer composite made with 17 % of WO3 loading is found to be optimum. The 2.35 mm thick sample possesses the attenuation equivalent to 0.25 mm lead at 100 kV, which is recommended by IAEA (International Atomic Energy Agency) to fabricate radiation shielding aprons to attenuate scattered X-rays. The developed composite shows a tensile strength of 4.6 MPa, which is suitable for fabricating wearable radiation shields.

Micro-CT scan optimisation for mechanical loading of tibia with titanium tibial tray: A digital volume correlation zero strain error analysis

Primary stability of press-fit tibial trays is achieved by introducing an interference fit between bone and implant. The internal cancellous bone strains induced during this process and during loading have yet to be quantified experimentally. Advancements in large-gantry micro-CT imaging and digital volume correlation (DVC) allow quantification of such strains. However, before undertaking such a test, experimental requirements and DVC performance need to be examined, particularly considering the presence of a large orthopaedic implant (tibial tray). The aim of this study was to assess the DVC zero-strain accuracy (mean absolute error: MAER) and precision (standard deviation of error: SDER) on a cadaveric human tibia implanted with a titanium press-fit tray across four plausible scanning configurations, using a cabinet micro-CT system (Nikon XT H 225 ST). These varied in rotation step and resulting scanning time (106 min vs. 66 min), presence or absence of a 2 mm-thick aluminium cylinder for mechanical testing, and X-ray tube voltage (150 kVp vs. 215 kVp). One proximal tibia was implanted and micro-CT scanned (42 μm/pixel), with repeated scanning and specimen repositioning in between. DVC (DaVis, LaVision, direct correlation) was performed on nine cubic volumes of interest (VOIs: 13.4 mm-side) and across the entire proximal tibia. Strain errors were comparable across the four scanning configurations and sufficiently low for assessing bone within its elastic region in VOIs (MAER=223-540 με; SDER=88-261 με) and at organ level (MAER=536 με; SDER=473 με). Whilst the investigated experimental conditions, including a large titanium implant, present added complexity for DVC analysis, scans of sufficient quality can be achieved, reaching a compromise between the DVC requirements and the wanted application. The approach used for choosing the X-ray source settings considering the transmitted X-ray signal intensity and source power, is also discussed.

Effect of x-ray tube voltage variation to value of contrast to noise ratio (CNR) on computed tomography (CT) Scan at RSUD Bali Mandara

Research has been conducted on the effect of variations in X-ray tube voltage to value of Contrast to Noise Ratio (CNR) on CT Scan at Bali Mandara Hospital using a phantom as a patient replacement. This research aims to determine the effect of X-ray tube voltage to the CNR value. Exposure factors used are X-ray tube voltage with variations of 80, 110, 120 and 135 kV, constant X-ray tube current of 150 mA and constant exposure time of 1 s. The readings of Io, Ib, and sb values in phantom images were performed using RadiAnt DICOM Viewer software (64 bit) and analysis of the effect X-ray tube voltage on CNR values was determined by regression test. The results of the analysis show that the variation of the X-ray tube voltage has a significant effect on the CNR value, where the greater X-ray tube voltage, the greater the CNR value. When the X-ray tube voltage is adjusted to 135 kV, the optimal CNR values are 113.52 for air, 35.06 for derlin, 13.93 for acrylic, 10.44 for nylon and 12.19 for polypropylene.

Luminescence and Structural Characterization of Gd2O2S Scintillators Doped with Tb3+, Ce3+, Pr3+ and F for Imaging Applications

Radiodiagnostic technologies are powerful tools for preventing diseases and monitoring the condition of patients. Medicine and sectors such as industry and research all use this inspection methodology. This field demands innovative and more sophisticated systems and materials for improving resolution and sensitivity, leading to a faster, reliable, and safe diagnosis. In this study, a large characterization of gadolinium oxysulfide (Gd2O2S) scintillator screens for imaging applications has been carried out. Seven scintillator samples were doped with praseodymium (Pr3+), terbium (Tb3+) activators and co-doped with praseodymium, cerium, and fluorine (Gd2O2S:Pr,Ce,F). The sample screens were prepared in the laboratory in the form of high packing density screens, following the methodology used in screen sample preparation in infrared spectroscopy and luminescence. Parameters such as quantum detection efficiency (QDE), energy absorption efficiency (EAE), and absolute luminescence efficiency (ALE) were evaluated. In parallel, a structural characterization was performed, via XRD and SEM analysis, for quality control purposes as well as for correlation with optical properties. Spatial resolution properties were experimentally evaluated via the Modulation Transfer Function. Results were compared with published data about Gd2O2S:Pr,Ce,F screens produced with a standard method of a sedimentation technique. In particular, the ALE rose with the X-ray tube voltage up to 100 kVp, while among the different dopants, Gd2O2S:Pr exhibited the highest ALE value. When comparing screens with different thicknesses, a linear trend for the ALE value was not observed; the highest ALE value was measured for the 0.57 mm thick Gd2O2S:Pr,Ce,F sample, while the best MTF values were found in the thinner Gd2O2S:Pr,Ce,F screen with 0.38 mm thickness.

The Effects of Different Exposure Factors on Leakage Radiation in an X-ray Room

This study evaluated leakage radiation doses inside an x-ray room at patient’s positioning levels. The effects of different exposure settings (X-ray tube voltage, radiation exposure intensity, dosimeter position, and distance from X-ray tube) on leakage radiation dose are estimated. Various x-ray tubes and models were used in this evaluation. The findings of this study revealed that, the increase of tube voltage (kVp), and tube current (mAs) led to a concomitant increase in the quantity of leakage radiation, whereas the increase in distance from X-ray tube and dosimeter position reduces the intensity of recorded leakage radiation according to inverse square low. In addition, the evaluation of leakage X-ray for investigated X-ray units illustrated that, leakage radiation doses at patient level around X-ray tubes were within the permissible occupational dose. Finally, the reduction of leakage radiation dose can be acquired by reducing the intensity of radiation (mAs) and increasing the distance between imaged object and x-ray source.

Reduced of radiation exposure and iodine load at CT angiography of the aorta before aortic and aortic valve replacement surgery

Objective . The comparison of protocols of computed tomography (CT) angiography of the aorta and their modification in conditions of radiation and iodine load reducing on the patient. Methods . In 95 patients (57 men, 38 women, mean age 61.4 ± 15.6 years) CT angiography of the aorta was performed using two- and three-zone scanning protocols with the voltage value on the X-ray tube (80 and 100kV) depending on the anthropometric measure namely body mass index (BMI). We compared dose length product parameters (DLP), effective dose (E), time and duration of scanning, as well as counting the amount of injected contrast agent (CM) between groups examined using a two-zone and three-zone protocols at an X-ray tube voltage of 80 and 100kV. Results . Analysis of the data obtained showed that the DLP and E values were statistically significantly lower with the CT angiography of the aorta protocol, which consisted of three scanning zones (at 80kV p = 0.008; at 100kV p < 0.001). At the same time, there was no significant difference in the length of the study area in groups with the same voltage on the X-ray tube (p = 0.55), in the group with a three-zone protocol, the scanning time was significantly lower (p < 0.001) and amounted to 9.4 ± 0.5 sec/10.24 ± 0.9 sec (80/100kV), which made it possible to significantly reduce radiation exposure up to 40% and the amount of injected contrast agent by 20%. Conclusions . The use of a three-zone CT-angiography of the aorta protocol with individual selection of voltage of the X-ray tube is justified and allows a significant reduction of radiation and iodine exposure compared to twozone scanning while maintaining the high images quality.