Effect Of Exposure Parameters Research Articles

Effects of Exposure Parameters and Voxel Size for Cone-Beam Computed Tomography on the Image Matching Accuracy with an Optical Dental Scan Image: An In Vitro Study

This study is aimed at assessing the effects of exposure parameters and voxel size for cone-beam computed tomography (CBCT) on the image matching accuracy with an optical dental scan image. CBCT and optical scan images of a dry human mandible were obtained. Different CBCT settings were used: tube voltage, 60, 80, and 100 kVp; tube current, 6 and 8 mA; and voxel size, 100, 200, and 300 μm. Image matching between the CBCT and optical scan images was performed using implant planning software by dental professionals (n = 18). The image matching accuracy in each combination of CBCT settings was evaluated by assessing the linear discrepancy between the three-dimensionally reconstructed radiological image and the registered optical scan image using an image analysis software program. The Kruskal-Wallis test and a post hoc Mann–Whitney U test with Bonferroni correction were used to compare the accuracy of image registration between the groups (α = 0.05). Overall, the image matching accuracy was not significantly different between tube voltage and current settings; however, significantly higher image registration errors were found at the combination of 100 kVp tube voltage/8 mA tube current (F = 8.44, P < 0.001). Changes in voxel sizes did not significantly interfere with the image registration results. No interaction was found among voltage, current, and voxel size in terms of image registration accuracy (F = 2.022, P = 0.091). Different exposure parameter settings in tube voltage and tube current did not significantly influence the image matching accuracy between CBCT and optical dental scan images; however, a high radiation dose could be inappropriate. The image matching accuracy was not significantly affected by changing the voxel sizes of CBCT.

A review of the effects of exposure parameters on DAP and ESD on fluoroscopy X-rays systems

During fluoroscopic and interventional procedures, radiographers monitor and record patient DAP/ESD values, from which local DRLs can be established. DRLs are used as a guide for dose optimisation for different imaging modalities. However the relevance of DRLs in paediatric fluoroscopic procedures is questionable. Different factors, e.g. pulse rate, magnification, etc. enable radiographers to optimise the radiation dose received by the patient. This is especially important in paediatric radiology, were optimal exposure is of utmost importance. The fundamental aim of this work is to provide adequate information to radiographers of the effects different parameters have to the DAP and ESD values on the various fluoroscopy systems in the hospital. Two mobile and one fixed fluoroscopy system were studied. Results indicate that at higher pulse rates, the increase in DAP and ESD rates when going from one pulse rate to another vary across the different systems, with one system increasing by up to 160%. Results also showed a decrease in DAP values of up to 30% when changing from full field to higher magnification settings while the ESD rates increased by up to 16%. A comprehensive investigation is presented here of the effects the varying parameters have on DAP and ESD values. Information sheets are being developed for the respective unit to improve the radiographer’s understanding of the systems. This will subsequently provide more confidence in their decisions with real time dose optimisation during complex procedures, which will be in line with image gently protocols and the new BSS.

Celestial Object Imaging Model and Parameter Optimization for an Optical Navigation Sensor Based on the Well Capacity Adjusting Scheme.

The simultaneous extraction of optical navigation measurements from a target celestial body and star images is essential for autonomous optical navigation. Generally, a single optical navigation sensor cannot simultaneously image the target celestial body and stars well-exposed because their irradiance difference is generally large. Multi-sensor integration or complex image processing algorithms are commonly utilized to solve the said problem. This study analyzes and demonstrates the feasibility of simultaneously imaging the target celestial body and stars well-exposed within a single exposure through a single field of view (FOV) optical navigation sensor using the well capacity adjusting (WCA) scheme. First, the irradiance characteristics of the celestial body are analyzed. Then, the celestial body edge model and star spot imaging model are established when the WCA scheme is applied. Furthermore, the effect of exposure parameters on the accuracy of star centroiding and edge extraction is analyzed using the proposed model. Optimal exposure parameters are also derived by conducting Monte Carlo simulation to obtain the best performance of the navigation sensor. Finally, laboratorial and night sky experiments are performed to validate the correctness of the proposed model and optimal exposure parameters.

Effect of exposure parameters and annealing on the structure and morphological properties of nanopatterned sapphire substrates prepared by solid state reaction

Nanopatterned sapphire substrates were prepared by solid state reaction of patterned Al films obtained by E-Beam lithography of a PMMA/copolymer bilayer resist and lift-off. The effect of exposure parameters and annealing on the structure and morphological properties of nanopatterned sapphire substrates prepared by solid state reaction were investigated by a scanning electron microscope (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and Raman, respectively. The circular Al patterns with diameter/spacing being 500nm/1000nm were obtained by optimal exposure diameter/exposure dosage of 400nm/200μC/cm2. Patterned Al films were subsequently subjected to solid state reaction by dual stage annealing due to the melting temperature of Al thin films (660°C). The hillocks formation on Al films was minimized with an oxidation anneal at 450°C. Moreover, the little change in the morphology of Al patterns was observed after annealing at 450°C. The SEM and AFM results show the patterns were retained on sapphire substrates after high temperature annealing at less than 1200°C. The XRD and Raman results reveal that the composition and orientation of island patterns prepared by solid state reaction for 24h at 450°C, and 1h 1000°C were the same as that of the sapphire (0001) substrates.

Microbubble-enhanced high intensity focused ultrasound therapy: effect of exposure parameters on thermal lesion volume and temperature

Microbubble agents have been shown to increase therapeutic effect of HIFU (high intensity focused ultrasound). Here, the effects of treatment parameters on lesion volume and temperature are investigated. Ex vivo tissue was treated with a 2 MHz HIFU beam in absence and presence of the Artenga™ microbubbles at varying HIFU focal intensities (649-2316 W/cm2), microbubble concentrations, and exposure durations (3-10 s). The temperature was measured at 1 mm from focus using a K-type thermocouple. Thermal lesion volume was measured based on an ellipsoid model. Microbubbles increased the lesion volume and peak temperature achieved with HIFU. At the intensity of 2316 W/cm2, the lesion volume increased by 2-folds, and the peak temperature increased by 16° C with microbubbles. This effect depended on microbubble concentration, ultrasound intensity and exposure duration. Lower intensities and shorter time durations were required at higher microbubble concentrations to ablate the tissue. It was concluded that the efficacy of the HIFU therapy in combination with microbubbles can be controlled through ultrasound/microbubble exposure parameters

Preparation of Organic Soluble Polyimides and Their Applications in KrF Excimer Laser LIGA Process

In this study two organic soluble polyimides were successfully synthesized via polycondensation of a hexafluoropropyl group contained dianhydride with two kinds of diamines. These two polyimides (DMDB/6FDA, OT/6FDA) can be dissolved in most aprotic solvents (for example, NMP, DMAc) and many other common solvents (for example, THF, DMSO). The soluble polyimides also show good thermal stability and high absorption at the KrF excimer laser wavelength (λ = 248 nm). (The absorption coefficients of DMDB/6FDA and OT/6FDA were 1.26×105 cm–1 and 1.49×105 cm–1, respectively.) The photoablation properties of the polyimides were studied in detail. Due to incorporating the hexafluoropropyl group into the chemical structure, these two polyimides have higher etching rates than Kapton (a commercial PI film). The effects of exposure parameters on linewidth and taper-angle of polyimides with different chemical structure were also investigated here. Under the proper control of exposure conditions, good precision patterns with near-vertical side wall can be produced. The 300 mm thick comb-shape and Fresnel patterns with 10 mm linewidth have been made. Moreover, the complementary metallic microstructures have also been realized in the following electroforming procedure. The results showed that these two soluble polyimides were very suitable for KrF Laser LIGA process.

Treatment of implanted liver tumors with focused ultrasound

This article reports treatment of implanted liver tumors (HSN fibrosarcoma) with focused ultrasound (FUS). Experiments were carried out on implanted liver tumors in vivo. In order to determine the optimum treatment conditions, various combinations of exposure parameters were investigated. The results showed that it is possible to achieve total destruction of tumor cells in the treatment volume using an FUS system with a frequency of 1.7 MHz, with in situ I SAL of 261 W/cm 2, 5-s exposure duration, and 1.5-mm exposure separation, with an in situ I SAL of 266 W/cm 2, 10-s duration, and 2-mm separation, or with in situ I SAL of 213 W/cm 2, 8-s duration, and 1.5-mm separation. Fifteen selected tumors were treated with these experimentally determined “optimum” exposure conditions. All the tumors were destroyed completely. Assessment of tumor viability in the treated volume was performed using both histologic and tissue culture methods. The mechanism of tumor damage, the limitations of the tumor model, and the effect of exposure parameters and liver blood flow on the treatment are discussed.