Dose Rate Calculation in the Vicinity of the Tunisian Gamma Irradiation

Dose rates calculations, in PMMA dosimeters, placed in the vicinity of the Tunisian 60Co gamma ray irradiator, have been achieved using a pencil like model. The obtained results are in good agreement with recent experimental data. Moreover, in this work we determine also the conversion factor between the dose rate deposited in a PMMA dosimeter and the one deposited in a reel medium. This factor is used to determine the dose deposited in a real irradiated medium such as foodstuff products.

Comparison of Gamma Pass Rate between the Dose-to-Water and Dose-to-Medium Reporting Modes for Patient-Specific QA Using a Helical Diode Array Dosimeter with a Fixed Phantom Density

Introduction: To compare the measured dose distributions to calculated ones in dose-to-water (Dw) and dose-to-medium (Dm) reporting modes for simple plans and patient-specific intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) plans using ArcCHECK with a fixed phantom density. Methods: The recommended density value of 1.18 g/cm3 for Acuros XB and X-ray voxel Monte Carlo was assigned to ArcCHECK on CT images. A total of 45 simple plans, including a 1-field plan, a 3-field plan, a 4-field plan, a half-arc plan from 270° to 90°, and a full-arc plan, were assessed. Subsequently, the patient-specific 96 IMRT and VMAT plans were evaluated. Gamma analysis with a 3% normalized global dose error and a 3 mm distance-to-agreement criteria (γ3%G/3mm) was performed in the Dw and Dm. The change in γ3%G/3mm between Dw and Dm were statistically analyzed using JMPPro11 software. Results: The median values of γ3%G/3mm for all simple plans for Dw and Dm were 98.1% (range, 75.2% - 100%) and 95.5% (range, 23.7% - 100%), respectively (p 0.01). In the patient-specific IMRT and VMAT plans, the median values of γ3%G/3mm for Dw and Dm were 98.6% (range, 90.1% - 100%) and 90.5% (range, 38.5% - 97.2%), respectively (p 0.01). Conclusion: Our results showed that the calculated and measured dose distributions were in good agreement for Dw, but were not for Dm. From the viewpoint of the rationale of dosimetry, Dw shows better agreement with measured dose distribution when using the fixedphantom density recommended by the vendor.

Effect of ionizing radiation on dual 8-bit analog-to-digital converters (AD9058) with various dose rates and bias conditions

The radiation effects on several properties （reference voltage, digital output logic voltage, and supply current） of dual 8-bit analog-to-digital （A/D） converters （AD9058） under various biased conditions are investigated in this paper. Gamma ray and 10-MeV proton irradiation are selected for a detailed evaluation and comparison. Based on the measurement results induced by the gamma ray with various dose rates, the devices exhibit enhanced low dose rate sensitivity （ELDRS） under zero and working bias conditions. Meanwhile, it is obvious that the ELDRS is more severe under the working bias condition than under the zero bias condition. The degradation of AD9058 does not display obvious ELDRS during 10-MeV proton irradiation with the selected flux.

Natural background radiation dose rate levels and incidences of reproductive abnormalities in high radiation area in Abeokuta, Southwestern Nigeria

A 10 y (1999-2008) birth records from two public and most accessible maternity hospitals locally in the city of Abeokuta, Nigeria were used to investigate the possible association of high outdoor gamma radiation exposure on reproductive abnormalities in the city. From the delivery record of 11,923 births in the period under study, a total number of 485 incidences of reproductive abnormalities were recoded. These incidences comprise 228 multiple births, 190 still births and, 67 premature births. Using the available terrestrial gamma radiation exposure data for the city and different reproductive abnormalities, regression assessment was carried out using the Pearson Product Moment (PPM) correlation statistics. The correlation showed that the incidences of reproductive abnormalities and the radiation dose levels were negatively correlated and correlation coefficient values were very low for each of the reproductive abnormalities considered. Factors such as socio-economic potentials of patients, dietary and other environmental factors may have substantial influence on the reproductive defects in the area other than radiation. However, the present study has added to the radiometric information needed in understanding the relationship between natural outdoor radiation exposure and occurrences of reproductive abnormalities in areas of high radiation in the country.

Assessment of Natural Radioactivity Levels and Radiation Dose Rate in Some Soil Samples from Historical Area, AL-RAKKAH, Saudi Arabia

This study aims to determine the activity concentrations of naturally occurring, technically-enhanced levels of radiation and the gamma absorbed dose rates in soil samples collected across the land scape of historical area which discovered in east of Saudi Arabia at 2009 G, Called AL- RAKKAH. By using an HPGe detector gamma-ray spectrometer, the activity concentrations of 226Ra 232Th and 40K were found in surface soil samples ranged from 17. 4 ± 1.2 Bq/kg to 28.3 ± 2.3 Bq/kg with an average value of 23 ± 1.6 Bq/kg, ranging from 1.1 ± 1.8 Bq/kg to 81.0 ± 1.7 Bq/kg with the average value 20 ± 1.4 Bq/kg and from 218 ± 11 Bq/kg to 255 ± 18 Bq/kg, with the mean value of 233 ± 12 Bq/kg respectively. The mean radium equivalent (Raeq) and outdoor radiation hazard index (Hex) for the area under study were determined as 69.52 Bq/kg and 0.16 respectively. The total absorbed dose rate due to three primordial radionuclides lies in the range of 17.74 - 72.24 nGy·h-1 with a mean of 32.69 nGy·h-1, which yields total annual effective dose of 0.37 mSv·y-1. The measured values are comparable with other global radioactivity measurements and are found to be safe for public and environment. The baseline data of this type will almost certainly be of importance in making estimations of population exposure.

SiC探测器的中子和γ性能测试

第三代SiC半导体探测器具有体积小、响应时间快、中子/伽马(n/γ)甄别容易等优点,广泛应用于反应堆堆芯剂量监测。本文针对自研的第三代SiC半导体探测器,采用电子束蒸发真空镀膜的技术将中子转换层材料^(6)LiF(^(6)Li丰度为95%)喷镀到SiC基底上,厚度为25μm,实现了中子转换层厚度优化。利用^(241)Amα放射源(活度9.37×10^(3)Bq)开展α粒子响应信号幅度的测量,并在^(137)Csγ放射源(活度6.23×10^(7)Bq)环境下开展γ射线的响应测试。另外,在标准辐射场系统中进行了SiC探测器的中子注量率响应线性度测量、γ剂量率响应线性度测量以及中子注量率响应线性标定。结果表明:该探测器在1×10^(3)~1×10^(6)cm^(−2)·s^(−1)中子注量率范围内线性响应拟合R^(2)=0.9969,具有良好的线性响应,n/γ剂量响应范围为0.005~20 Gy∙h^(−1),可用于核电现场反应堆中子和γ剂量的实时、精确监测。

利用地面γ总量转换为空气吸收剂量率进行环境辐射水平评价——以桂阳县潘家村和永兴县土桥村实测数据为例

在长期的铀矿普查中,我国积累了海量的γ总量数据资料,但应用这些数据进行放射性环境评价的研究极少。本文从γ总量和空气吸收剂量率的测量原理出发,通过梳理γ总量、放射性核素含量与空气吸收剂量率之间的关系,建立起地面γ总量与空气吸收剂量率之间的联系,分析了仪器参数对测量误差的影响,认为γ总量仪器bK/bU=2.287、bTh/bU=0.430时,测量的γ总量与空气吸收剂量率满足严格线性关系,因此γ总量仪器的bK/bU、bTh/bU值越接近这两个数值,测得的γ总量转换为空气吸收剂量率越准确;利用湖南省电离辐射计量站模型进行了γ总量转换为空气吸收剂量率的系数求解,并分析了误差,推测了仪器参数中钾的铀当量值、钍的铀当量值的大致范围;在郴州市桂阳县潘家村岩体和郴州市永兴县土桥村灰岩地区进行了γ总量、γ能谱、空气吸收剂量率的同点位实测,结果显示,当核素含量比CK/CU均值小于1、CTh/CU均值小于3时,利用γ总量(FD3013仪器测得)估算的空气吸收剂量率与利用Beck公式根据能谱估算的空气吸收剂量率的误差基本处于同等水平,均方根误差均小于15%。根据国内核素的CK/CU、CTh/CU均值,认为国内大部分地区可以利用由FD3013仪器(或类似性能仪器)测得的γ总量数据估算空气吸收剂量率。利用已有铀矿普查资料中的γ总量数据转换计算有效空气吸收剂量率,为快速大面积评估环境天然放射性外照射水平提供了方法参考。

宫颈癌调强放射治疗三维在体剂量验证分析及最佳γ通过率阈值

目的:对宫颈癌调强放射治疗(IMRT)进行基于电子射野影像装置的三维在体剂量验证(EIVD)分析,研究测量剂量与计划剂量间的差异,并通过剂量学敏感性探讨EIVD质控中最佳γ通过率阈值。方法:回顾性分析浙江大学医学院附属妇产科医院行IMRT的45例宫颈癌患者,所有患者在治疗过程中行EIVD验证,获取测量剂量。采用2mm/2%、2mm/3%、3mm/3%的全局γ指标进行通过率分析,采用剂量体积直方图参数评估测量剂量和计划剂量之间的差异。通过皮尔逊(Pearson)相关性分析研究γ通过率与剂量学差异间的相关性,绘制受试者工作特征(ROC)曲线确定最佳γ通过率阈值。结果:3类γ指标2mm/2%、2mm/3%、3mm/3%的平均通过率分别为(83.07±5.25)%、(91.69±3.52)%、(95.02±2.46)%;EIVD测量剂量与计划剂量在计划靶区(PTV)的平均剂量(Dmean)偏差为2.43%(P=0.016),膀胱、直肠、小肠的Dmean偏差分别为0.35%、0.46%、0.30%(P>0.05)。Pearson分析显示3类γ指标与PTV的剂量偏差相关性较强(r>0.7),与危及器官相关性较弱(r<0.7);ROC分析显示2mm/2%、2mm/3%、3mm/3%最佳的γ通过率阈值分别为79.06%、90.04%、94.19%。结论:EIVD能够有效保证宫颈癌IMRT过程中PTV剂量传递的精准性,利用γ通过率阈值能够为下一步宫颈癌自适应IMRT提供一定的临床依据。

最小子野宽度对原发性肝癌IMRT计划的剂量分布和实施精度的影响

目的:通过对原发性肝癌调强放射治疗(IMRT)计划的最小子野宽度参数进行研究,评价不同最小子野宽度下治疗计划的剂量分布和实施精度,为肿瘤患者放疗计划制作提供参考。方法:选取30例原发性肝癌患者资料,保持其它优化条件不变,改变最小子野宽度,分别为0.6、0.8、1.0、1.2、1.5 cm,对每例患者制作5个IMRT计划,比较5个计划的剂量分布、执行效率和Gamma通过率。结果:这5个计划的机器跳数和出束时间随着最小子野宽度的增加而减少;3 mm/3%、2 mm/2%阈值下的Gamma通过率则呈现增加趋势,且具有统计学差异(P<0.05)。结论:研究所用的5个计划均能够用于临床治疗,在满足临床要求的同时,合理地设置IMRT计划中的最小子野宽度,可以降低机器跳数,缩短治疗时间,又可以提高治疗精度。

基于ArcCheck模体放疗计划的验证与分析

目的为了保证放疗剂量输出的准确性,对放疗患者的临床放疗计划进行了验证与分析。方法选取2023年7—10月南方医科大学珠江医院放疗患者的临床放疗计划,共217例计划,其中头颈部76例,胸部82例,腹盆部59例。采用美国SunNuclear公司的ArcCheck模体,比较临床放疗计划与验证计划的剂量学差异。采用T test分析在不同容许剂量差值和不同容许距离差值下的Gamma通过率,ANOVA test比较在相同条件下,不同放疗部位放疗计划的Gamma通过率。所有数据分析采用IBM公司的SPSS v27.0完成。结果在容许剂量差值为3%,容许距离差值为3.0mm和在容许剂量差值为2%,容许距离差值为2.0mm下的Gamma通过率比较,差异有统计学意义(P<0.05)。在相同容许剂量差值和容许距离差值下,不同放疗部位的Gamma通过率比较,差异无统计学意义(P>0.05)。结论在容许剂量差值为3%,容许距离差值为3.0mm的条件下,放疗计划的Gamma通过率显著高于容许剂量差值为2%,容许距离差值为2.0mm条件下的计划Gamma通过率,并且条件设置越严格,Gamma通过率越低。在相同容许剂量差值和容许距离差值下,不同放疗部位放疗计划的Gamma通过率不存在显著性差异。Gamma通过率受容许剂量差值和距离差值的影响,同时做好对直线加速器,计划系统等的日常的质量控制与保证也能提高Gamma通过率。

放疗计划参数对剂量验证计划γ通过率的相关性研究

目的 探讨头颈部放疗计划参数对剂量验证计划γ通过率的相关性。方法 选取2019年11月—2021年9月福建肿瘤医院放疗中心收治的184例放射治疗的头颈部肿瘤患者。其中85例采用调强放疗(intensity-modulated radio therapy,IMRT)计划,99例采用容积旋转调强放疗(volumetric modulated arc therapy,VMAT)计划,通过电子射野影像装置,使用ArcCHECK分别对IMRT和VMAT计划进行计量验证,并在不同的γ分析标准(选取1%/1 mm,2%/2 mm和3%/3 mm)下验证剂量通过率。分析不同放疗计划中射野复杂度指标,并判断其射野复杂度指标与γ通过率的相关性。结果 VMAT计划在1%/1 mm标准下γ通过率低于IMRT计划,差异有统计学意义(P <0.05);VMAT计划和IMRT计划在2%/2 mm标准下γ通过率分别为(90.72±2.84)%、(90.59±5.19)%,在3%/3 mm标准下γ通过率分别为(97.02±1.71)%、(98.64±1.00)%,2种计划在3%/3 mm标准下的平均γ通过率均较高,在2%/2 mm标准下的平均γ通过率均有所下降,2种计划比较差异无统计学意义(P> 0.05)。在不同射野复杂度指标中,VMAT计划的计划标准跳数(plan normalized MU,PMU)、计划平均射野不规则性(plan averaged beam irregularity,PI)、计划平均射野调制(plan averaged beam modulation,PM)均大于IMRT计划,VMAT计划的平均调制复杂度分数(modulation complexity score,MCS)、计划平均射野面积(plan averaged beam area,PA)小于IMRT计划,差异有统计学意义(P <0.05)。Spearman相关性检验结果表明,IMRT计划中,在2%/2 mm标准下,MCS、PM和γ通过率呈弱相关性(|r|<0.4,P <0.05),PMU和γ通过率呈中度相关性(0.4≤|r|≤0.7,P <0.05),在3%/3 mm标准下,PMU、MCS、PM和γ通过率呈中度相关性(0.4≤|r|≤0.7,P <0.05);PA、PI与γ通过率均无相关性(P> 0.05);VMAT计划中,在2%/2 mm标准下,PMU、MCS、PI、PM和γ通过率呈中度相关性(0.4≤|r|≤0.7,P <0.05),在3%/3 mm标准下,PMU、MCS、PM、PI和γ通过率呈中度相关性(0.4≤|r|≤≤0.7,P <0.05),PA与γ通过率均无相关性(P> 0.05)。结论射野复杂度指标与γ通过率具有不同程度的相关性,可在剂量验证前调整射野指标辅助设计放疗计划。

SRS MapCHECK与EDOSE在立体定向放疗计划剂量验证中的对比

目的:使用SRS MapCHECK和EDOSE对立体定向放疗(SRT)计划进行剂量验证,并比较它们的验证结果。方法:首先比较两种系统在不同方野(2 cm×2 cm、4 cm×4 cm、6 cm×6 cm、10 cm×10 cm)的γ通过率(3%/3 mm),然后选择29例SRT计划,分析两种系统在不同γ标准下的绝对剂量通过率,最后分析EDOSE建立的4种不同物理模型对SRT计划剂量验证的影响。结果:SRS MapCHECK在所有方野和29例SRT计划的绝对剂量γ通过率均高于EDOSE,两者的验证结果有统计学差异(P<0.05);SRS MapCHECK及EDOSE在29例SRT计划的γ通过率(2%/2 mm)分别是为98.60%±2.14%和96.53%±2.41%。基于EDOSE的不同物理模型验证结果有统计学差异,平均γ通过率(2%/2 mm)偏差为1.8%~5.1%。结论:SRS MapCHECK和EDOSE系统均满足SRT计划剂量验证的要求,且SRS MapCHECK的剂量验证通过率优于EDOSE;不同的EDOSE物理模型对SRT计划剂量验证有影响。

桂阳潘家庄地区地表γ辐射空气吸收剂量率估算与放射性环境评价

桂阳潘家庄地区花岗岩大面积出露,导致土壤中的放射性核素活度浓度普遍偏高。较高的γ辐射空气吸收剂量是否存在风险成为人们关心的问题。本文通过已有γ伽玛能谱测量数据估算出地表γ辐射空气吸收剂量率,根据地表γ辐射空气吸收剂量率与人居环境适宜性的关系,从而进行人居环境适宜性分区。得出γ辐射安全区197.90 km^(2),占全区面积的98.95%;风险区1.42 km^(2),占0.71%;管制区仅0.68 km^(2);表明潘家庄地区天然放射性人居环境优良。本文可为该地区人居环境选址、合理、有效地利用潘家庄地区的国土资源提供支持,也可对加速潘家庄地区乡村健康与可持续发展提供必要的参考。

γ射线探伤机表面漏射线防护装置的设计与应用

目前国内γ射线探伤机主机体(源容器)的屏蔽性能要求应符合GB/T 14058-2008标准,也就是γ射线探伤机主机体表面的辐射当量剂量率不能超出2000μGy/h,此数值比射线探伤作业场所控制区允许的辐射当量剂量率限值高出133倍。工作人员在操作γ射线探伤机时,不可避免要近距离接触γ射线探伤机,相比控制区增加了工作人员的受照剂量,给探伤工作人员造成一定伤害和心理压力。针对这种问题设计了一种可减小γ射线探伤机表面漏射线的防护装置,以减少工作人员受照剂量,从而增加接触时间,提高检验效率,减小对工作人员的伤害。试验结果表明:在TS-1A型铱-192γ射线探伤机和TS-1B型钴-60γ射线探伤机上安装屏蔽防护装置后,可以将主机体表面辐射当量剂量率减小约150倍和90倍。

Measurement of Gamma-Rays Using Smartphones

The CMOS (Complementary Metal Oxide Semiconductor) image sensor of a smartphone has been known for its sensitivity to gamma-rays. In this research, some smartphones were selected and tested for measurement of gamma-rays emitted from Cesium-137 and Iridium-192 sources. During measurements, the phones were set in video mode while the camera lenses were covered with black adhesive tape to prevent light exposure. Interaction of gamma-rays with the CMOS appeared as flashing bright spots on the image. The bright spots were then counted by using the freely available ImageJ software. Preliminary results indicated that the number of bright spots increased linearly with increase of gamma-ray dose rate. An in-house Android application software was then developed for real-time counting of the bright spots. The application software also allowed users to input a calibration equation so that the phones could simultaneously convert the count rate to display in dose rate. This research demonstrated that, after appropriate calibration, smartphones could be used as gamma-ray measuring devices for radiation safety control involving high activity sources such as in industrial radiography, gamma-ray irradiation facility and medical treatment.

Gamma radiation levels in the ambient environment of the QNPP Base

Monitoring results of gamma dose rate level in 1992～2004 in the ambient environment of the Qinshan Nuclear Power Plants(QNPP)Base,the northeast of Zhejiang Province,are reported in this paper.It is shown that the gamma dose rate of five monitoring sites of 2.5 km to QNPP Base is 84～113 nGy/h,with an average of 96 nGy/h in the 13 years.The average value is close to the background level of 93 nGy/h prior to operation of the QNPP Base,and is lower than the monitoring result of 101 nGy/h at the reference site in Hangzhou City.Within 50 km from the QNPP Base,the cumulative dose rate of the thermoluminescent dosimeter(TLD)is 90 nGy/h,which is lower than the back- ground level of 111 nGy/h.

Micro-Tuber Production in Diploid and Tetraploid Potato after Gamma Irradiation of in Vitro Cuttings for Mutation Induction

Micro-tubers are important propagules in potato breeding and potato production, and they are also dormant and easily transported and therefore good targets for mutation induction in potato mutation breeding. A prerequisite for mutation breeding is to determine optimal mutation treatments. Therefore, radio-sensitivity tests of a tetraploid and a diploid potato to gamma irradiation were undertaken. Effects of different gamma sources on radio-activity were also studied. In vitro potato cuttings were gamma irradiated using a wide dose range (0, 3, 6, 9, 12, 15 and 20 Gy). The irradiated cuttings were then cultured to induce micro-tubers directly in vitro. Micro-tuber morphotypes were assessed after irradiation of cuttings using three gamma sources with emission activities of 1.8, 7.07 and 139 Gy/min. The diploid species (Solanum verrucosum) was more radio-sensitive than the tetraploid cultivar Desirée (Solanum tuberosum). Gamma dose rates had significant influences on subsequent micro-tuber production at various mutant generations. Effects included reductions in the number, size and weight of micro-tubers produced. Gamma dose was more lethal for the diploid potato genotype and micro-tubers produced were small compared to those produced by the tetraploid genotype after irradiation. Different treatments are recommended for diploid and tetraploid potato irradiation in producing large mutant micro-tuber populations. The mutant micro-tuber populations may then be screened for interesting mutations/trait for both genetics and plant breeding purposes.

新疆伊犁盆地南缘天然放射性水平评价

本文根据新疆伊犁盆地南缘1∶2.5万地面γ能谱测量中的铀、钍、钾含量数据,对新疆伊犁盆地南缘地表介质的天然放射性进行了研究和评价。测量结果显示,该地区地表介质中放射性核素^(238)U、^(232)Th和^(40)K的比活度,分别为6.14~2584.64 Bq/kg、2.86~105.63 Bq/kg、11.58~2190.83 Bq/kg。γ射线空气吸收剂量率均值为75.56 nGy/h,低于全国(81.50 nGy/h)和世界(80.00 nGy/h)的平均值;内、外照射指数和年有效剂量都在国家限量标准控制范围内。研究区局部放射性水平相对偏高,与含铀地层露头受自然动力和人类活动等作用下铀元素扩散有关;由于含铀地层露头规模有限,其对放射性环境的影响具有强度小、范围小、不均匀特征。

受天然放射性核素污染场地土壤放射性调查工作内容及程序研究

本文参考建设用地土壤污染状况调查的工作内容及程序,结合放射性核素污染特征及其在环境介质中的迁移规律等,归纳总结了一套受天然放射性核素污染场地土壤放射性调查的工作内容及程序,为土壤放射性污染调查提供参考。将土壤放射性污染调查分为第一阶段土壤放射性污染调查和第二阶段土壤放射性污染调查,调查内容包括资料收集、现场踏勘、现场采样与监测、室内分析、报告编制等,监测项目包括地表环境γ辐射剂量率,土壤及地下水中^(238)U、^(232)Th、^(226)Ra核素浓度。根据工作内容及程序对两个可能受天然放射性核素污染的场地土壤进行调查,以评价工业过程对工矿企业场地土壤中放射性核素浓度的影响。调查结果表明该调查的工作内容及程序可行。

基于电子射野影像装置的肺部肿瘤立体定向体部放射治疗在体三维剂量验证模体研究及临床应用

目的:探讨基于电子射野影像装置的肺部肿瘤立体定向体部放射治疗在体三维剂量验证模体研究及临床应用。方法:通过电子射野影像装置在体三维剂量验证系统,在静态和动态模体上测试不同立体定向体部放射治疗照射技术计划(静态调强、滑窗调强、旋转调强及适形、动态适形旋转治疗),比较在体三维剂量分布5种剂量/距离一致性标准(5%/2 mm、3%/3 mm、3%/2 mm、3%/1 mm、2%/2 mm)的γ通过率,检测计划照射精度,并对临床肺立体定向体部放射治疗病例进行在体三维剂量验证靶区和危及器官剂量体积分析。结果:模体研究结果显示,在静态模体中静态调强、滑窗调强、旋转调强照射方式γ通过率差异无统计学意义(P均>0.05),在动态模体中静态调强计划γ通过率偏低,其他照射方式计划之间相近。临床应用结果显示,临床病例在体三维剂量验证3%/3 mm标准明显低于治疗前剂量验证结果,剂量体积直方图分析中体积变化大的危及器官存在较大剂量偏差。结论:基于电子射野影像装置的肺部肿瘤立体定向体部放射治疗在体三维剂量验证,能为肺部肿瘤立体定向体部放射治疗治疗期间剂量投照的准确性提供有效安全性检查,可应用于临床,为自适应治疗提供基础。