Computed tomography simulator conversion curve dependence on scan parameters and phantom dimension

Introduction: Using computed tomography (CT) and treatment planning systems (TPS) in radiotherapy, due to the difference in photon beam energy on CT and linear accelerator, it is necessary to convert Hounsfield units (HU) to relative electron density (RED) values. The aim of this dosimetric study was to determine whether there is a significant effect of potential in the CT tube, field of view size (FOV), and phantom dimensions on the CT conversion curve CT-RED. The second aim is whether there are significant differences between the CT-RED obtained by the Computerized Imaging Reference Systems (CIRS) Thorax 002LFC phantom and the “reference” curve in the TPS, obtained by the CIRS 062M pelvis phantom, at the same CT conditions.Methods: Heterogeneous CIRS 062M and CIRS Thorax 002LFC phantoms were used, which anatomically and dimensionally represent the human pelvis, head, and thorax, with a set of known RED inserts. They were scanned on a CT LightSpeed GE simulator and obtained CT-RED.Results: The high voltage in the CT tube had a significant effect on the HU (t = 10.72, p < 0.001) for RED values >1.1, while FOV as a parameter did not show statistical significance for the 062M pelvis phantom. Comparing the slopes (062M pelvis and head) of the CT-RED for RED ≥ 1.1, the obtained value is t = 1.404 (p = 0.163). In the case of a 062M pelvis and a 002LFC phantom, we have seen a difference in RED values (for the same HU value) of 5 % in the RED region ≥ 1.1 (bone).Conclusion: Patients should be imaged on a CT simulator only at the potential of the CT tube on which the conversion curve was recorded. The influence of the FOV and scanned phantom dimensions is not statistically significant on the appearance of the calibration curve (RED ≥ 1.1).

Impact of typhoon Vongfong 2014 on the ionosphere and geomagnetic field according to Swarm satellite data: 1. Wave disturbances of ionospheric plasma

The article considers the influence of large atmospheric processes on the ionosphere by the example of tropical typhoon Vongfong 2014. We use data obtained from three SWARM satellite missions (450–500 km altitude). We discuss two possible mechanisms of transfer of atmospheric disturbances to ionospheric heights. The first mechanism is the generation of acoustic-gravity waves (AGWs); the second mechanism considers the excitation of electric fields in the atmosphere. We propose new techniques for detecting the ionospheric response to AGW, which rely on low-orbit satellite data. The first technique is based on determination of relative electron density variations in the frequency band from 15 to 150–180 s, corresponding to certain scales of AGW. The second technique estimates space-time derivatives of the electron density, measured by two nearby SWARM satellites. We present and estimate the characteristic magnitudes of ionospheric response effects, their localization and spatial-temporal characteristics for the large tropical cyclone under study.

Impact of typhoon Vongfong 2014 on the ionosphere and geomagnetic field according to Swarm satellite data: 1. Wave disturbances of ionospheric plasma

The article considers the influence of large atmospheric processes on the ionosphere by the example of tropical typhoon Vongfong 2014. We use data obtained from three SWARM satellite missions (450–500 km altitude). We discuss two possible mechanisms of transfer of atmospheric disturbances to ionospheric heights. The first mechanism is the generation of acoustic-gravity waves (AGWs); the second mechanism considers the excitation of electric fields in the atmosphere. We propose new techniques for detecting the ionospheric response to AGW, which rely on low-orbit satellite data. The first technique is based on determination of relative electron density variations in the frequency band from 15 to 150–180 s, corresponding to certain scales of AGW. The second technique estimates space-time derivatives of the electron density, measured by two nearby SWARM satellites. We present and estimate the characteristic magnitudes of ionospheric response effects, their localization and spatial-temporal characteristics for the large tropical cyclone under study.

Manufacture and Determination of Absorbent in Bolus Radiotherapy Based On Alginate Using of 8 MeV and 10 MeV Energy

Bolus radiotherapy have been created by using material of mixture a silicone rubber as matrix and alginate powder as a filler through chemical solution deposition methods with variation of composition silicone rubber: alginate powder: catalyst (99 : 0 : 1)%wt, (80: 19: 1)%wt, (80: 18: 2)%wt, (80: 17: 3)%wt, (80:16: 4)%wt and (80: 15: 5)%wt. The sample fabrication was done in two steps. The first step of alginate powder is mixed with a solution of rubber and catalyst silicon until homogeneous for 5 minutes with the wet mixing method. The second step of the powder which was homogeneously mixed was printed with glass mould measuring 11 x 11 x 1 cm3 with variations in thickness of 5 mm, 10 mm and 15 mm then dried at 300. Each bolus sample is already to be characterized which includes: physical properties (density, porosity, and water absorption), mechanical properties (tensile strength, elongation and modulus young) and performance (CT Number and absorbency dose). The characterization results showed that alginate powder: optimum rubber silicon ie (80: 19) wt% at a thickness of 15 mm resulted in a density value of 2.091 x 103 kg/m3, porosity of 9.82% and water absorption of 1.66%. Mechanical properties with tensile strength 3.37 MPa, elongation at 45.28% and modulus of elasticity of 0.816 MPa. Bolus radiotherapy performance properties relative electron density (RED) values or CT numbers of 1.25 resulted in surface absorbance doses of 8 MeV of 101% and 10 MeV of 108.01%. The results of bolus radiotherapy based on composite alginate powder reinforced by silicone rubber can be applied as a cancer therapy material to replace bolus from wax, and paraffin.

Characteristics of Bolus Using Silicone Rubber with Silica Composites for Electron Beam Radiotherapy

Bolus is a material that equal with the tissue and functions to increase the dose radiation in surface area in external radiotherapy, which uses electron beam. In this research, bolus was made using silicone rubber (SR) material, which was mixed with silicacomposites material. The bolus with a dimension of 12 x 12 x 0,5 cm3 was successfully made with a various amount of silica composite (2%, 4%, 6%). Bolus was then characterized using linear accelerator (LINAC) with an electron beam for percentage of surface dose (PSD) and using CT-Scan to measurement relative electron density (RED). The energy of electron beam used in this research was5 and 7 MeV. The result shows that RED value increased with increasing the amount of silica composite with higher RED value amounted to 1.186. PSD value increased with increasing the amount of silica composite, higher PSD value of energy in 5 and 7 MeV amounted 106.82% and 106.82% and 100.34%, respectively. The result certified that the silica composite material can increase the percentage of surface dose on electron beam radiotherapy.