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Objective:To evaluate the usability of Gafchromic HD-V2 film for dose dosimetry in the ultra-high dose-rate (UD) electron beam from a modified medical linac, and to investigate the response between the energy and dose-rate dependence to the film.Methods:The HD-V2 film was utilized to measure the average dose-rate of the UD electron beam. The measured result was compared with those by advanced Markus chamber and alanine pellets. And characteristics of the UD electron beam were also measured by HD-V2 film. Energy dependence of HD-V2 film at three beam energies (6 MV X-ray, 9 MeV and 16 MeV electron beam) was investigated by obtaining and comparing the calibration curves based on the clinical linear accelerator in the dose range of 10-300 Gy. The dose-rate dependence of HD-V2 film was also studied by varying the dose rate among 0.03 Gy/s, 0.06 Gy/s and 0.1 Gy/s, and range of 100-200 Gy/s.Results:The measured average maximum dose-rate of 9 MeV UD electron beam at source skin distance (SSD) 100 cm was approximately 121 Gy/s using HD-V2 film, consistent with the results by advanced Markus chamber and alanine pellets. The measured percentage depth dose (PDD) curve parameters of the UD electron beam were similar to the conventional 9 MeV beam. The off-axis dose distribution of the UD electron beam showed the highest central axis, and the dose was gradually decreased with the increase of off-axis distance. The energy dependence of HD-V2 film had no dependency of 6 MV and 9, 16 MeV while measuring the dose in the range from 20 to 300 Gy. The HD-V2 film had no significant dose-rate dependency at the dose rate of 0.03 Gy/s, 0.06 Gy/s and 0.1 Gy/s for the clinical linear accelerator. Likewise, there was also no dose-rate dependence in the range 100-200 Gy/s in the modified machine.Conclusion:HD-V2 film is suitable for measuring ultra-high dose rate electron beam, independent of energy and dose rate.
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@#<b>Objective</b> To calculate the energy dependence of absorbed dose in EBT3 film, and to reveal the error in the measurement of proton absorbed dose by EBT3 film. <b>Methods</b> Beam energy was gradually increased in the clinical photon and proton energy ranges. Geant4 was used to calculate the difference in absorbed dose between EBT3 film and the same volume of water. The results were compared with the theoretical values. <b>Results</b> For photons and protons, the thresholds for absorbed dose with energy dependence were 100 keV and 11 MeV, respectively. The energy dependence was consistent with the theoretical values when the photon and proton energies were higher than the corresponding thresholds, and irrelevant to the theoretical values when energies were lower than the thresholds. The differences between the proton Bragg peak and 50% dose point and the actual positions were less than 1%. <b>Conclusions</b> For protons and photons with high energy, the energy dependence of absorbed dose in EBT3 film is negligible. For protons and photons with low energy, EBT3 film shows very different energy dependence of absorbed dose, which should be taken into consideration. The proton Bragg peak and 50% dose point measured by EBT3 film are basically the same as the actual positions.
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Abstract We study the threshold anomaly displayed in the energy dependence of optical potentials describing elastic-scattering angular distributions of weakly bound nuclei with three different models: a) a semi-microscopic double folding potential with two free parameters, b) a phenomenological Wood-Saxon potential with six free parameters and c) an exponential potential with two free parameters. In this kind of nuclei, the coupling to the breakup channel is reflected as an increasing of the imaginary part of the potential as the bombarding energy decreases below the Coulomb barrier, while the real part of the potential (linked to the imaginary part by the dispersion relation) decreases in strength. This behavior is called breakup threshold anomaly (BTA). In this work, we apply this analysis to experimental data for the elastic scattering in the 9Be+80Se systemat eleven bombarding energies around the Coulomb barrier, obtained at the 20 MV tandem accelerator of the TANDAR Laboratory at Buenos Aires. Using the covariance-matrix method to estimate the uncertainties, the presence of the BTA in this system is unambiguously determined, independently of the model chosen for the nuclear potential.
Resumen Estudiamos la anomalía de umbral presente en la dependencia con la energía de potenciales ópticos que describen la dispersión elástica de núcleos débilmente ligados, usando tres tipos de potenciales ópticos para la descripción de las distribuciones angulares: a) un potencial semimicroscópico doblemente plegado con dos parámetros libres, b) un potencial fenomenológico tipo Wood-Saxon con seis parámetros libres y c) un potencial exponencial con dos parámetros libres. En este tipo de núcleos, el acoplamiento al canal de ruptura se refleja como un aumento de la parte imaginaria del potencial al decrecer la energía de bombardeo por debajo de la barrera de Coulomb, mientras que la parte real (vinculada a la parte imaginaria por la relación de dispersión) disminuye en intensidad. Este comportamiento se denomina anomalía de umbral de ruptura (BTA). En el presente trabajo, se aplica este análisis a datos experimentales concernientes a la dispersión elástica en el sistema 9Be + 80Se a 11 energías de bombardeo alrededor de la barrera de Coulomb, obtenidos con el acelerador de 20MV del Laboratorio TANDAR en Buenos Aires. Se utilizó el método de matriz de covarianza para estimar las incertidumbres, se determina inequívocamente la presencia de la BTA en este sistema, independientemente del modelo elegido para el potencial nuclear.
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As an important ABC transporter, breast cancer re-sistance protein ( BCRP) plays an important role in tumor multi-drug resistance. Many laboratories are focusing on BCRP to re-verse multidrug resistance. We summarize in the paper the re-search progress on the regulation of BCRP expression, subcellu-lar localization, ATP-dependence, inhibition or modulation of its transport activity and potential clinical treatment strategies in or-der to provide theoretical support and some new research ideas for the reverse of multidrug resistance in clinic.
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Objective To study the dosimetric characteristics of two different radiochromic films used to estimate peak skin dose(PSD) of patients.The characteristics of these two films were investigated and compared after exposure to ionizing radiation in the diagnostic energy range,including post-exposure gray growth,sensitivity,energy dependence and dose response.Methods GafChromic XR-RV3 film and KODAK EDR2 film were exposed to air kerma 800 mGy free-in-air using five X-ray beam qualities (60,80,100,120 and 140 kVp) in a SSDL.The measurement for each energy was normalized to 80 kV to analyze energy dependence of films.The films were calibrated to different dose level (0.025-10 Gy) onphantom by 80 kV X-rays.The response curve were plotted to analyze sensitivity and dose response.The films were scanned with Epson V750 commercial flatbed scanner.Color channel analysis was performed.Results The post-exposure gray growth of XR-RV3 film was found to be fairly stable.The change were 2％,4％,6％ at 24 h,72 h and 6 weeks after exposure respectively.EDR2 film was found to be more sensitivity than XR-RV3 film in low dose.The energy response of the XR-RV3 film and EDR2 film were within 9％ and 23％ over the clinical diagnostic x-ray energies,respectively.In the dose range of 0.025-10 Gy,for the XR-RV3 film,the red channel with the dose response curve was most obvious.For EDR2 film,the pixel value of three color channels was coincident.The EDR2 film appeared to be saturated when receiving doses greater than 500 mGy.Conclusions The XR-RV3 film is superior to EDR2 film in gray growth,energy dependence,dose-response and other aspects.This film is very suitable for measuring and analyzing PSD of patients in interventional radiology procedures.
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Objective To assess the feasibility of ESD measurements in the mammography by the comparative study of energy dependence of the three passive solid detectors on low energy X-ray.Methods Two thermoluminescent TL) detectors ( LiF(Mg,Ti) and LiF( Mg,Cu, P) and one optically stimulated luminescence (OSL) detector( Al2O3: C ) were irradiated for the same air kerma by ten kinds of beam quality between 25-40 kV in a Mo/Mo low energy X-ray generator,respectively. Results The energy dependences of TL and OSL were 25% and 11% between 25-40 kV, respectively. Conclusions considerable potential for OSL detector can be used in routine quality control and ESD measurements in the mammography.
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PURPOSE: An investigation has been carried out on the factors which affect the response reading of thermoluminescent dosimeters (TLD-100) loaded with thin material in high energy photon. The aim of the study was to assess the energy response of TLD-100 to the therapeutic ranges of photon beam. MATERIALS AND METHODS: In this technique, TLD-100 (abbreviated as TLD) chips and three different thin material (Tin, Gold, and Tissue equivalent plastic plate) which mounted on the TLD chip were used in the clinical photon beam. The thickness of each metal plates was 0.1 mm and TE plastic plate was 1 mm thick. These compared with the photon energy dependence of the sensitivities of TLD (normal chip), TLD loaded with Tin or Gold plate, for the photon energy range 6 MV to 15 MV, which was of interest in radiotherapy. RESULTS: The enhancement of surface dose in the TLD with metal plate was clearly detected. The TLD chips with a Gold plate was found to larger response by a factor of 1.83 in 10 MV photon beam with respect to normal chip. The sensitivity of TLD loaded with Tin was less than that for normal TLD and TLD loaded with Gold. The relative sensitivity of TLD loaded with metal has little energy dependence. CONCLUSION: The good stability and linearity with respect to monitor units of TLD loaded with metal were demonstrated by relative measurements in high energy photon (6~15 MV) beams. The TLD laminated with metals embedded system in solid water phantom is a suitable detector for relative dose measurements in a small beam size and surface dose.