Repair of potentially lethal damage by total and quiescent cells in solid tumors following a neutron capture reaction

Purpose: We analyzed the time-course of changes in the sensitivity of total (proliferating + quiescent and quiescent (Q) cell populations within solid tumors in situ following a neutron capture reaction and compared it with that after γ-ray irradiation. Methods: After continuous labeling of proliferating cells with BrdU for 5 days, mice bearing SCC VII tumors received thermal neutron irradiation with or without a ¹⁰B-labeled compound (sodium [¹⁰B]borocaptate, BSH, or dl-p-[¹⁰B]boronophenylalanine, BPA), or γ-ray irradiation. From 5 min to 72 h after treatment, tumors were excised, minced, and trypsinized. Cell suspensions were incubated for 48 h with the cytokinesis blocker cytochalasin-B. The micronucleus frequency for BrdU-unlabeled cells, Q cells at treatment, was then determined by immunofluorescence staining for BrdU. The micronucleus frequency for total cells was obtained from tumors that had not been pretreated with BrdU labeling. The sensitivity was evaluated in terms of the frequency of induced micronuclei in binuclear tumor cells (micronucleus frequency). Results: Overall, Q cells showed greater repair capacities than total cells. γ-Ray irradiation and neutron irradiation with BPA induced larger repair capacities in each cell population. In contrast, thermal neutron irradiation without a ¹⁰B-labeled compound induced the smallest repair capacity in both cell populations. The use of a ¹⁰B-labeled compound, especially BPA, widened the difference in sensitivity between total and Q cells, resulted in an increase in repair capacity in both cell populations, and made the repair patterns of the two cell populations look like those induced by γ-ray irradiation. Conclusion: Differences in sensitivity and repair patterns following the neutron capture reaction were thought to depend on differences in the distribution of the ¹⁰B-labeled compound between the proliferating and Q cell populations. Received: 18 February 1999 / Accepted: 4 June 1999     

广西医用电子加速器验收检测泄漏辐射水平分析

目的：验收、检测广西地区医用电子加速器,分析其泄漏辐射水平,为估算放射职业人员、患者辐射防护剂量水平和制定放射防护控制策略提供依据,为医院的放射治疗质量控制提供指导。方法：对广西29台医用电子加速器进行验收、检测。使用热释光剂量计（TLD）测量加速器的泄漏辐射水平;使用中子测量仪测量中子的泄漏辐射水平,结合国家标准对其进行分析与评价。结果：加速器透过限束装置的辐射泄漏率最大值≤1.2%,平均值≤0.65%;距电子轨道1 m处辐射泄漏率最大值≤0.46%,有用线束中心轴2 m圆平面内辐射泄漏率最大值≤0.19%,平均值≤0.09%;标称能量≥10 MV的加速器,其电子轨道1 m处中子的辐射泄漏率最大值≤0.032%,有用线束中心轴2 m圆平面内中子的辐射泄漏率最大值≤0.028%,平均值≤0.014%。结论：所检测设备的泄漏辐射水平均在国家标准控制范围内,医用加速器的泄漏辐射水平是设备防护性能的重要指标,在其投入使用前必须通过验收,以确保医疗质量和安全。     

Image enhancement using MCNP5 code and MATLAB in neutron radiography

This work presents a method that can be used to enhance the neutron radiography (NR) image for objects with high scattering materials like hydrogen, carbon and other light materials. This method used Monte Carlo code, MCNP5, to simulate the NR process and get the flux distribution for each pixel of the image and determines the scattered neutron distribution that caused image blur, and then uses MATLAB to subtract this scattered neutron distribution from the initial image to improve its quality.This work was performed before the commissioning of digital NR system in Jan. 2013. The MATLAB enhancement method is quite a good technique in the case of static based film neutron radiography, while in neutron imaging (NI) technique, image enhancement and quantitative measurement were efficient by using ImageJ software. The enhanced image quality and quantitative measurements were presented in this work.     

The new facility for neutron tomography of IPEN-CNEN/SP and its potential to investigate hydrogenous substances

A new facility for neutron tomography has been installed at the IEA-R1 nuclear research reactor of IPEN-CNEN/SP. A tomography can be obtained in 400 s and the spatial resolution in the image is 263 μm. The neutron dose per tomography, in the video camera used for image capture, is only 21 μSv, assures very few damages in its CCD sensor. Some selected objects were investigated and the obtained 3D images demonstrate the capability of the facility to investigate hydrogenous substances.     

Measurements of isomeric cross sections for the (n,α) reaction on the 142Nd isotope at approximately 14 MeV neutrons

In this study, the activation cross sections were measured for ¹⁴²Nd(n,α)^139mCe reaction at four neutron energies between 13.57 and 14.83 MeV, which were produced by a neutron generator through ³H(²H,n)⁴He reaction. The production of short-lived activity and the spectra accumulation were performed by the cyclic activation technique. Induced gamma-ray activities were measured using a high resolution gamma ray spectrometer equipped with a high-purity Germanium (HpGe) detector. In the cross section measurements, corrections were made regarding the effects of the gamma-ray attenuation, the dead-time, the fluctuation of the neutron flux, and low energy neutrons. The measured cross sections were compared with the published literature and the results of the model calculation (TALYS 1.4).     

In-situ hydrogen in metal determination using a minimum neutron source strength and exposure time

Water is frequently present in the environment and is a source of hydrogen that can interact with many materials. Because of its small atomic size, a hydrogen atom can easily diffuse into a host metal, and though the metal may appear unchanged for a time, the metal will eventually abruptly lose its strength and ductility. Thus, measuring the hydrogen content in metals is important in many fields, such as in the nuclear industry, in automotive and aircraft fabrication, and particularly, in offshore oil and gas fields. It has been demonstrated that the use of nuclear methods to measure the hydrogen content in metals can achieve sensitivity levels on the order of parts per million. However, the use of nuclear methods in the field has not been conducted for two reasons. The first reason is due to exposure limitations. The second reason is due to the hi-tech instruments required for better accuracy. In this work, a new method using a low-strength portable neutron source is explored in conjunction with detectors based on plastic nuclear detection films. The following are the in-situ requirements: simplicity in setup, high reliability, minimal exposure dose, and acceptable accuracy at an acceptable cost. A computer model of the experimental setup is used to reproduce the results of a proof-of-concept experiment and to predict the sensitivity levels under optimised experimental conditions.     

Hiroshima survivors exposed to very low doses of A-bomb primary radiation showed a high risk for cancers

Objectives  The aim of this study was to compare the risk for cancers of A-bomb survivors in the ongoing life span study (LSS) with unexposed groups consisting of the entire populations of Hiroshima prefecture and neighboring Okayama prefecture. Methods  The subjects consisted of the Hiroshima group reported in LSS report 12 (LSS-H group) and a control group (the entire populations of Hiroshima and Okayama—HPCG and OPCG, respectively). We estimated the expected number of deaths due to all causes and to cancers of various causes among the exposed survivors of the Hiroshima bombing in the LSS report 12 who died in the follow-up interval at ages similar to those of people in Hiroshima and Okayama prefectures who were aged 0–34 years at the time of the bombing in 1945. We compared the standardized mortality ratio (SMR) of the LSS-H group to that of the HPCG and OPCG (SMR-H and SMR-O, respectively). Results  Even at low and very low dose categories, the SMR-H and SMR-O were significantly high for all deaths, all cancers, solid cancers, and liver cancers in male subjects, and for uterus and liver cancers in female subjects, respectively. The results show that, if the dose estimations of the dosimetry system 1986 (DS86) are correct, there are significantly increased risks of cancer among even survivors exposed to the very low dose level. Conclusions  The dose assumptions of DS86 have been criticized for underestimating doses in areas distant from the hypocenter. The contribution of residual radiation, ignored in LSS, and that of neutrons, underestimated by DS86, is suggested to be fairly high. An erratum to this article can be found at     

快中子治疗前列腺癌初报

目的观察快中子与光子混合射线治疗前列腺癌的效果及毒副作用。材料与方法北京市快中子治疗协作组于１９９２年１月～１９９６年６月共收治前列腺癌１９例。用快中子与光子混合射线治疗１６例，快中子剂量为６００～１１６０ｎｃＧｙ，Ｘ线剂量为３０００～６０００ｃＧｙ，前列腺局部剂量为６４８０～７８００ｃＧｙ。单纯快中子治疗组剂量１０００～１２００ｎｃＧｙ。中子治疗多用前后－后前（ＡＰ－ＰＡ）照射野，Ｘ线用４野“盒式”技术或５野照射盆腔。结果全组患者放疗后泌尿系统症状改善率９３．８％；８４．６％患者的卡氏行为状态评分（ＫＰＳ）值改进。全组７例死亡（５例死于本病，２例死于并发症）。２年生存率１０／１４（７１．４％），２年肿瘤专项生存率（ｃａｎｃｅｒ－ｓｐｅｃｉｆｉｃｓｕｒｖｉｖａｌ）１０／１２（８３．３％）；３年生存率６／７（８５．７％），３年肿瘤专项生存率６／６（１００．０％）。全组１３例（６８．４％）出现急性放射反应。长期生存患者１２例中，７例（５８．３％）出现晚期反应，３例（２５．０％）为Ⅰ～Ⅱ度，４例（３３．３％）Ⅲ～Ⅳ度。结论混合射线对前列腺癌有较好的疗效，但严重并发症发病率也较高。     

Soya foods and breast cancer risk: a prospective study in Hiroshima and Nagasaki, Japan

The association between soya foods and breast cancer risk was investigated in a prospective study of 34759 women in Hiroshima and Nagasaki, Japan. Women completed dietary questionnaires in 1969-1970 and/or in 1979-1981 and were followed for incident breast cancer until 1993. The analysis involved 427 cases of primary breast cancer in 488989 person-years of observation. The risk for breast cancer was not significantly associated with consumption of soya foods: for tofu, relative risks adjusted for attained age, calendar period, city, age at time of bombings and radiation dose to the breast were 0.99 (95% CI 0.80-1.24) for consumption two to four times per week and 1.07 (0.78-1.47) for consumption five or more times per week, relative to consumption once a week or less; for miso soup, relative risks were 1.03 (0.81-1.31) for consumption two to four times per week and 0.87 (0.68-1.12) for consumption five or more times per week, relative to consumption once a week or less. These results were not materially altered by further adjustments for reproductive variables and were similar in women diagnosed before age 50 and at ages 50 and above. Among 17 other foods and drinks examined only dried fish (decrease in relative risk with increasing consumption) and pickled vegetables (higher relative risk with higher consumption) were significantly related to breast cancer risk; these associations were not prior hypotheses and, because of the large number of comparisons made, they may be due to chance.