Intercomparison of Gafchromic™ films,TL detectors and TL foils for the measurements of skin dose in interventional radiology

Several passive solid state dosemeters, such as Gafchromic™ films and thermoluminescence (TL) detectors, are used to estimate and monitor patient skin doses in interventional radiology. To determine the suitability of XR-TypeR Gafchromic™ films and of detectors based on TL materials: pellets, chips and foils to measure skin dose, an intercomparison exercise has been organized within European Dosimetry Radiation Group – Working Group 12 “European Medical ALARA Network” (EURADOS WG12). To test response detectors were exposed to X-ray beams of energies and qualities applied clinically. A blind test was also performed to investigate the accuracy of the dose estimate by detectors exposed to unknown doses. We found the response of films to be strongly dependent on beam quality and filtration (increasing by up to 80% with respect to reference beam quality). The response of TL detectors was found to be less dependent on beam quality (less than 25% variation), with TL foils showing less than 10% variation with respect to reference beam quality. To accurately estimate patient skin doses in interventional radiology it is important to choose the quality of the calibration beam to be as close as possible to the quality of beams actually applied in clinical work.     

Out-of-field dose measurements in radiotherapy – An overview of activity of EURADOS Working Group 9: Radiation protection in medicine

This review of dosimetry for second cancer risk estimation introduces work carried out by Working Group 9 (WG9: Radiation Protection Dosimetry in Medicine) of the European Radiation Dosimetry Group (EURADOS). The work concentrates on the measurement of out-of-field doses in water phantoms using a variety of dosimeters to measure photon and neutron doses. These include optically stimulated luminescence (OSL), radiophotoluminescence (RPL) and thermoluminescence (TLD) dosimeters for photon dosimetry (together with ion chambers for reference measurements) and track etch and superheated emulsion detectors for neutron measurements. The motivation of WG 9 was to assess undue, non-target patient doses in radiotherapy and the related risks of second malignancy. Improvements in cancer treatment have increased survival times and thus increased incidence of second cancer may be expected in the future. In addition, increased whole body exposure may result from some developments in radiotherapy. This means that radiotherapy clinics will need to simulate their treatments in order to estimate and minimise doses to healthy tissues and organs. The proposed work is designed to generate a robust dataset of out-of-field dose measurements which can be used for the development and validation of dose algorithms.     

Detection and tracking strategy for license plate detection in video

In this paper, we present a novel method to detect license plates in video sequences automatically. The framework mainly integrates the cascade detectors method and the Tracking Learning Detection (TLD) algorithm. The cascade detectors are used to detect license plates, and the TLD algorithm is adopted to track the license plate regions. The license plates in the first frame image are detected by the cascade detectors to build the original tracking list, the tracking results and the detection results in following frames will be compared, and the newly appearing license plate information will be added to the tracking list. Meanwhile, the tracking results existing in the current tracking list would be replaced by the corresponding detection results with higher degree of confidence. We demonstrate the effectiveness of our algorithm for license plate detection task on a road intersection dataset, and the experimental evaluation shows the detection performance has been greatly improved by synthetically using the detection and tracking strategy.     

Characterization of an in‐vacuum PILATUS 1M detector

A dedicated in‐vacuum X‐ray detector based on the hybrid pixel PILATUS 1M detector has been installed at the four‐crystal monochromator beamline of the PTB at the electron storage ring BESSY II in Berlin, Germany. Owing to its windowless operation, the detector can be used in the entire photon energy range of the beamline from 10 keV down to 1.75 keV for small‐angle X‐ray scattering (SAXS) experiments and anomalous SAXS at absorption edges of light elements. The radiometric and geometric properties of the detector such as quantum efficiency, pixel pitch and module alignment have been determined with low uncertainties. The first grazing‐incidence SAXS results demonstrate the superior resolution in momentum transfer achievable at low photon energies.     

中能质子注量率测量

质子是太空辐射环境中的主要粒子成分,随着半导体工艺向着小尺寸高集成度方向不断发展,质子单粒子效应不容忽视.通过加速器模拟空间辐射进行地面实验是评价质子单粒子效应最重要的手段,质子注量率的准确测量是器件考核评估过程中最关键的环节.本文基于原子能院100MeV质子单粒子效应辐照装置,突破了宽量程中能质子注量率测量技术,开发了法拉第筒、塑料闪烁体探测器和二次电子发射监督器等探测工具,可以对束流进行宽量程范围准确测量,解决了质子注量率在10~6—10~7 p·cm^-2·s^-1范围内难以测量的关键难题,并进行了注量率不确定度的分析研究,同一注量率下法拉第筒和塑料闪烁体探测器的实验测量误差与理论分析误差相符.对中能质子注量率测量达到了国际同类装置水平.该研究建立的中能质子注量率测量系统和不确定度分析方法,为准确评估元器件辐射效应奠定了基础.     

New experimental measurement of natSe(n, γ) cross section between 1 eV to 1 keV at the CSNS Back-n facility

The ⁷⁴Se is one of 35 p-nuclei, and ⁸²Se is a r-process only nucleus, and their (n, γ) cross sections are vital input parameters for nuclear astrophysics reaction network calculations. The neutron capture cross section in the resonance range of isotopes and even natural selenium samples has not been measured. Prompt γ-rays originating from neutron-induced capture events were detected by four C₆D₆ liquid scintillator detectors at the Back-n facility of China Spallation Neutron Source (CSNS). The pulse height weighting technique (PHWT) was used to analyze the data in the 1 eV to 100 keV region. The deduced neutron capture cross section was compared with ENDF/B-VIII.0, JEFF-3.2, and JENDL-4.0, and some differences were found. Resonance parameters were extracted by the R-matrix code SAMMY in the 1 eV-1 keV region. All the cross sections of ^natSe and resonance parameters are given in the datasets. The datasets are openly available at http://www.doi.org/10.11922/sciencedb.j00113.00019.     

Coherent phonon dynamics in short-period InAs/GaSb superlattices

We have performed ultrafast pump-probe spectroscopy studies on a series of InAs/GaSb-based short-period superlattice (SL) samples with periods ranging from 46 Å to 71 Å. We observe two types of oscillations in the differential reflectivity with fast (∼$\sim$1–2 ps) and slow (∼$\sim$24 ps) periods. The period of the fast oscillations changes with the SL period and can be explained as coherent acoustic phonons generated from carriers photoexcited within the SL. This mode provides an alternative method for determining the SL period. The period of the slow mode depends on the wavelength of the probe pulse and can be understood as a propagating coherent phonon wavepacket modulating the reflectivity of the probe pulse as it travels from the surface into the sample.     

微分吸收法测量二极管电压

给出了微分吸收法测量二极管电压的基本原理和实验结果。利用MCNP程序对轫致辐射-衰减-探测器系统建模,模拟得到了输出剂量与二极管工作电压关系拟合曲线。建立了微分吸收法测量二极管电压测量系统,通过在探测器前端放置不同厚度的吸收片,得到了衰减程度不同的波形。结合理论计算的拟合曲线和实验波形,利用迭代法计算得到了晨光号加速器二极管电压,电压峰值为0.58 MV。和传统方法所测得二极管工作电压进行了比较,结果较为一致。     

Comparison of Lu3Al5O12:Pr and Bi4Ge3O12 scintillators for gamma-ray detection

The scintillation properties of Lu₃Al₅O₁₂:Pr³⁺ (LuAG:Pr) single crystal grown by the Czochralski method with praseodymium concentration of 0.19 mol% were investigated. For a comparison, a good quality Bi₄Ge₃O₁₂ (BGO) single crystal grown by Bridgman method was also studied. The light yield and energy resolution were measured using photomultiplier tube (XP5200B PMT) readout. Moderate light yield of 15,900 photons per MeV was measured for the LuAG:Pr(0.19%) crystal. For 662 keV gamma rays (¹³⁷Cs source), an energy resolution of 6.5% obtained for LuAG:Pr(0.19%) is much better than that of 9.0% obtained for BGO. The light yield non-proportionality and energy resolution versus energy of gamma rays were measured and the intrinsic resolution of the crystals was determined after correcting the measured energy resolution for PMT statistics. The LuAG:Pr(0.19%) showed a good proportionality of the light yield within 5% over the energy range from 1274.5 keV down to 32 keV, which is much better than that of 14% for BGO. The photofraction was determined at 320 and 662 keV for both crystals and compared with the ratio of the cross-sections for the photoelectric effect to the total one calculated using WinXCOM program.     

组合透镜法测量透镜焦距方法研究及数值分析

为了解决神光系列装置所需长焦透镜焦距的检测问题,在现有斐索干涉仪的基础上,对常规组合透镜方法进行了拓展,提出了双探头光栅尺法。对两种方法的工作原理及检测方法进行了分析,同时计算分析了测量数据误差对测量结果的影响,得出测量数据测量误差的上限要求。这两种方法具有测量精度高、重复性好、测量过程简单的优点,对于各类透镜焦距的检测具有重要的实用价值。