Effects of low level radiation-what's new?

A comprehensive review of the effects of exposure to low levels of ionizing radiation, BEIR VII-Phase 2: Health Risks From Exposure to Low Levels of Ionizing Radiation, was published in 2006. The BEIR (Biological Effects of Ionizing Radiation) reports are a series of publications by the National Academy of Sciences. The last BEIR report on the effects of low level radiation, BEIR V, was published in 1990. To update the risk estimates for exposure to low levels of ionizing radiation, the BEIR committee reviewed recent epidemiologic studies of the atomic bomb survivors, as well as recent studies of populations exposed to radiation from diagnostic and therapeutic medical studies, from occupational exposures and from exposure due to releases of radioactive materials into the environment. Additional increasingly sophisticated epidemiologic studies continue to be published. BEIR VII reconfirmed that the linear no threshold model is the most practical model to estimate radiation risks, especially for radiation protection purposes. The updated risk estimates have not changed significantly from the BEIR V estimates, but the confidence intervals have narrowed as the result of the availability of additional data. The effects of low doses of radiation should be of particular interest to medical professionals because radiation exposure from diagnostic medical studies is, by far, the largest source of radiation exposure from human activity. One recommendation of the BEIR VII report is to perform epidemiologic studies of patients, especially children, who have been exposed to radiation as part of their care. A large, sophisticated epidemiologic study will likely be able to detect an increase in cancer risk. The purpose of this article is to highlight the contents of this important publication with particular emphasis on what is new.     

1992 assessment of radiation risk from dental radiography.

Recent studies suggest that the lifetime cancer risks from exposure to low levels of ionizing radiation may be greater than previously estimated. This review first summarizes the findings of these studies as they pertain to dental radiology, then uses their concepts in combination with dosimetry from the dental literature to estimate the radiation risk from dental radiology. Estimation of risk from groups of exposed individuals requires use of mathematical models that fit the epidemiological data. The ICRP estimates that a single brief whole-body exposure of 1 Gy to 10,000 people results in about 500 additional cancer deaths over the lifetime of the exposed individuals, assuming a dose rate effectiveness factor of 2 for cancers other than leukaemia. Leukaemias are seen as a wave from 5 to 30 years following exposure. Cancers other than leukaemia typically start to appear about 10 years following exposure and remain in excess for as long as most exposed populations are followed, presumably for the lifetime of the exposed individuals. The gonadal dose is so small from dental radiography that the risk of heritable defects is negligible in comparison with the somatic risk. The dental literature contains several studies reporting sufficient dosimetric data for radiosensitive sites in the head and neck to allow estimation of the risk of fatal cancers from intra-oral and panoramic radiography. The highest estimated risks (using the ICRP data) are for leukaemia (bone marrow), thyroid and bone surface cancer. The total risk is estimated to be 2.5 fatal malignancies per 10(6) full-mouth examinations made with D-speed film and round collimation.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of diagnostic X-ray exposure on the human fetus: an examination of the evidence.

Epidemiological studies have demonstrated an increased incidence of morbidity and mortality among children exposed prenatally or preconceptually to diagnostic x-rays, as compared to nonirradiated controls. In those studies radiation exposure occurred on a selective basis, as the examination was always medically indicated. Comparisons of those studies and comparable ones in which radiation exposure occurred on a nonselective basis (from routine pelvimetry examinations or atomic bomb radiation) indicate that the latter studies do not confirm the former and a significant discrepancy is present in each instance. Thus, some doubt is cast on the validity of the former studies.     

Exposure to chronic noise and fractionated X-ray radiation elicits biochemical changes and disrupts body weight gain in rat

The aim was to assess the developmental and biochemical effects resulting from separate and combined exposures to radiation and noise in adult male Sprague-Dawley rats. For 21 days, animals were exposed daily (1) to whole-body 121 kVp X-ray exposure (cumulative dose=5 Gy), (2) to random intermittent noise band-limited between 0.4 and 20 kHz; 2 h day(-1) 86 decibels (dB) and (3) to combined exposures. Control animals were housed under ambient noise conditions 55 dB A-weighted (dBA) and sham-exposed to X-rays. Body weight gain was significantly reduced in animals exposed to either X-rays or noise, and the loss was more pronounced in animals exposed to both conditions. Neither plasma adrenocorticotropic hormone (ACTH) nor corticosterone was altered by the treatment conditions. This study corroborated previous reports that ionizing radiation exposure increased plasma levels of 8-hydroxy-2'-deoxyguanosine (8-OHDG), but no effect was observed in animals co-exposed to chronic noise. Plasma big-endothelin-1 (Big ET-1) was significantly reduced in animals exposed to a combination of noise and X-rays. The results indicated that (1) adaptation to chronic noise appeared to occur at the level of the hypothalamic pituitary adrenal (HPA) response, in spite of a compromise in overall body weight gain; and (2) ionizing radiation exposure might alter systems activated by stressor exposure and/or act independently to influence health outcomes.     

Chronic low-dose gamma-radiation exposure and the alteration of the distribution of lymphocyte subpopulations in residents of radioactive buildings

Purpose : To elucidate the immunological change incurred in a human population by protracted gamma-radiation exposure at home environment. Materials and methods : An examination on the CD3+, CD4+, CD8+ and HLA-DR+ lymphocyte subsets was arranged for 196 exposed subjects with mean excess cumulative dose of 169mSv during 2-13 years of exposure. Another 55 close relatives of the exposed subjects were recruited as the non-exposed reference population. Results : The mean percentages of CD4+ T-lymphocytes, HLA-DR+ lymphocytes and the CD4+/CD8+ ratios in the exposed subjects (35.5, 19.9 and 1.51 respectively) were significantly lower than those of reference individuals (38.0, 22.6 and 1.72; p 0.02, 0.003, and 0.03 respectively), while the CD8 in total counts of the exposed was moderately increased above that of the reference populations (p=0.1). By ANOVA analysis, the percentages of CD4+ and HLA-DR+ subsets were significantly associated with radiation dose (p =0.0046, 0.003), while CD4+/CD8+ ratios were moderately associated with dose (p=0.073). HLA-DR+ counts were significantly and positively associated with duration of relocation from radioactive apartments (p=0.029). Conclusions : Significant immunological effects were observed in those who had received chronic low-dose radiation exposure.     

Ornithine decarboxylase activity is affected in primary astrocytes but not in secondary cell lines exposed to 872 MHz RF radiation

PURPOSE: The effects of radiofrequency (RF) radiation on cellular ornithine decarboxylase (ODC) activity were studied in fibroblasts, two neural cell lines and primary astrocytes. Several exposure times and exposure levels were used, and the fields were either unmodulated or modulated according to the characteristics of the Global System for Mobile (GSM) communications. MATERIALS AND METHODS: Murine L929 fibroblasts, rat C6 glioblastoma cells, human SH-SY5Y neuroblastoma cells, and rat primary astrocytes were exposed to RF radiation at 872 MHz in a waveguide exposure chamber equipped with water cooling. Cells were exposed for 2, 8, or 24 hours to continuous wave (CW) RF radiation or to a GSM type signal pulse modulated at 217 Hz, at specific absorption rates of 1.5, 2.5, or 6.0 W/kg. Cellular ODC activities of cell samples were assayed. RESULTS: ODC activity in rat primary astrocytes was decreased statistically significantly (p values from 0.003 to <0.001) and consistently in all experiments performed at two exposure levels (1.5 and 6.0 W/kg) and using GSM modulated or CW radiation. In the secondary cell lines, ODC activity was generally not affected. CONCLUSIONS: ODC activity was affected by RF radiation in rat primary neural cells, but the secondary cells used in this study showed essentially no response to similar RF radiation. In contrast to some previous studies, no differences between the modulated and continuous wave signals were detected. Further studies with primary astrocytes are warranted to confirm the present findings and to explore the mechanisms of the effects.     

Estimation of radiation tolerance to high LET heavy ions in an anhydrobiotic insect, Polypedilum vanderplanki

PURPOSE: Anhydrobiotic larvae of Polypedilum vanderplanki are known to show an extremely high tolerance against a range of stresses. We have recently reported that this insect withstands exposure to high doses of gamma-rays (linear energy transfer [LET] 0.2 keV/microm). However, its tolerance against high LET radiation remains unknown. The aim of this study is to characterize the tolerance to high-LET radiations of P. vanderplanki. MATERIALS AND METHODS: Larval survival and subsequent metamorphoses were compared between anhydrobiotic (dry) and non-anhydrobiotic (wet) samples after exposure to 1 - 7000 Gy of three types of heavy ions delivered from the azimuthally varying field (AVF) cyclotron with LET values ranging from 16.2 - 321 keV/microm. The tolerance against 4He ions was also compared among three chironomid species. RESULTS: At all LET values measured, dry larvae consistently showed greater radiation tolerance than hydrated larvae, perhaps due to the presence of high concentrations of the disaccharide trehalose in anhydrobiotic animals, and the radiation-induced damage became evident at lower doses as development progressed. Relative biological effectiveness (RBE) values based on the median inhibitory doses reached a maximum at 116 keV/microm (12C), and the maximum RBE clearly increased as development progressed. Lower D0 (dose to reduce survival from relative value 1.00 - 0.37 on the exponential part of the survival curve), and higher Dq (quasi-threshold dose) were found in individuals exposed to 4He ions, compared to gamma-rays, and in P. vanderplanki larvae compared to non-anhydrobiotic chironomids. CONCLUSION: Anhydrobiosis potentiates radiation tolerance in terms of larval survival, pupation and adult emergence of P. vanderplanki exposed to high-LET radiations as well as to low-LET radiation. P. vanderplanki larvae might have more efficient DNA damage repair after radiation than other chironomid species.     

Retrospective cohort study and biobanking of patients treated for hemangioma in childhood – telomeres as biomarker of aging and radiation exposure

Abstract

Purpose: Cohorts allowing joint epidemiological and biological analyses are essential for radiation risk assessment. The French Hemangioma Cohort (FHC), studied within the European project EpiRadBio, is one of the rare cohorts suitable for studying the effect of low dose radiation exposure (<100 mGy at organs), with a long-term follow-up. This highly homogeneous cohort consists of healthy individuals belonging to a normal population, except for the presence of skin hemangioma (age at exposure: between 6 months and 3 years of age). Published epidemiological studies have demonstrated that the risk of developing cancer is three times higher in the exposed individuals than in the general population. Here, we present the biobanking of samples (nucleated blood cells, cytogenetic slides of T and B lymphocytes) from the FHC and a primary feasibility study of biomarker analysis focusing on mean telomere length (MTL). Telomeres act as an internal clock, regulating the lifetime of the cell by their shortening during cell division. MTL is thus a biomarker of age. Many in vitro studies have linked MTL and radiosensitivity. The FHC will make it possible to discriminate between the effects of aging and radiation on this biomarker.

Conclusion: The establishment of a biobank of essentially healthy individuals (369 in total), exposed 40–70 years before, during their early childhood, is a logistical challenge. Even among those who previously participated to a self-questionnaire based study, the response rate was only 30%. The first biomarker to be studied was the MTL to discriminate age effects from those of radiation exposure. MTL showed significant variation within age groups (4–11?kb) in both the exposed and non-exposed groups. MTL within the limited age window (i.e. 40–73 year) examined, showed age-dependent changes of 46?bp/year, consistent with the age-dependent decline of 41?bp/year previously reported. We observed no significant changes in MTL according to the average active bone marrow dose. However, we were able to demonstrate that exposure to radiation causes the loss of cells with, on average, shorter telomeres, by applying a model in which both the heterogeneity of the individual dose received at the bone marrow and the heterogeneity of the intercellular distribution of MTL were taken into account.     

A survey of annual radiation dose for radiation workers from occupational and medical exposures in Kyushu]

This study was carried out to determine annual dose equivalents of exposure in workers exposed to medical radiation and occupational radiation in an enterprise associated with nuclear power plants. The results indicated that medical exposure is much higher than occupational exposure. Average annual effective dose equivalents for medical and occupational exposure were 4.0-7.5 mSv and 2.4-3.6 mSv, respectively. Individual occupational exposure limits have been well controlled and maintained at one-fifth of the dose limit for radiation workers (50 mSv/yr). On the other hand, medical exposure in the older workers of this enterprise has been increasing as a result of X-ray diagnosis with barium meal.     

Chronic low-dose gamma-radiation exposure and the alteration of the distribution of lymphocyte subpopulations in residents of radioactive buildings.

PURPOSE: To elucidate the immunological change incurred in a human population by protracted gamma-radiation exposure at home environment. MATERIALS AND METHODS: An examination on the CD3+, CD4+, CD8+ and HLA-DR+ lymphocyte subsets was arranged for 196 exposed subjects with mean excess cumulative dose of 169 mSv during 2-13 years of exposure. Another 55 close relatives of the exposed subjects were recruited as the non-exposed reference population. RESULTS: The mean percentages of CD4+ T-lymphocytes, HLA-DR+ lymphocytes and the CD4+ /CD8+ ratios in the exposed subjects (35.5, 19.9 and 1.51 respectively) were significantly lower than those of reference individuals (38.0, 22.6 and 1.72; p= 0.02, 0.003, and 0.03 respectively), while the CD8+ in total counts of the exposed was moderately increased above that of the reference populations (p=0.1). By ANOVA analysis, the percentages of CD4+ and HLA-DR+ subsets were significantly associated with radiation dose (p=0.0046, 0.003), while CD4+/CD8+ ratios were moderately associated with dose (p=0.073). HLA-DR+ counts were significantly and positively associated with duration of relocation from radioactive apartments (p = 0.029). CONCLUSIONS: Significant immunological effects were observed in those who had received chronic low-dose radiation exposure.     

Risk of breast cancer following low-dose radiation exposure.

Risk of breast cancer following radiation exposure was studied, based on surveys of tuberculosis patients who had multiple fluoroscopic examinations of the chest, mastitis patients given radiotherapy, and atomic bomb survivors. Analysis suggests that the risk is greatest for persons exposed as adolescents, although exposure at all ages carries some risk. The dose-response relationship was consistent with linearity in all studies. Direct evidence of radiation risk at doses under 0.5 Gy (50 rad) is apparent among A-bomb survivors. Fractionation does not appear to diminish risk, nor does time since exposure (even after 45 years of observation). The interval between exposure and the clinical appearance of radiogenic breast cancer may be mediated by hormonal or other age-related factors but is unrelated to dose. Age-specific absolute risk estimates for all studies are remarkably similar. The best estimate of risk among American women exposed after age 20 is 6.6 excess cancers/10(4) WY-G-Y (10(6) WY-rad).     

Ultraviolet exposure in the Ironman triathlon

PURPOSE: Skin cancer is increasing worldwide and exposure to ultraviolet (UV) radiation is thought to be the most important environmental risk factor. People practicing outdoor sports are exposed to considerable amounts of UV radiation from the sun. METHODS: Three triathletes participated in the Ironman Triathlon World Championships 1999 in Hawaii (3.9-km swim, 180.2-km bike, 42.4-km run). They attached Bacillus subtilis spore film dosimeters (VioSpor) on the back between their shoulders. The dosimeter system measured cumulative biologically weighted erythemal UV exposure. UV exposure is given in minimal erythema doses (1 MED corresponds to 250 J x m(-2) at 298 nm). RESULTS: The mean personal UV exposure was 8.3 MED (6.9--9.7 MED) after 8:43 to 9:44 h of competition corresponding to 0.8 to 1.3 MED x h(-1) (bike and run). The athletes were sunburned despite the use of water-resistant sunscreen (SPF 25+) on sun exposed skin. CONCLUSION: The International Radiation Protection Agency has issued guidelines for professional UV exposure. Ironman triathletes considerably exceeded these limits of exposure similar to other outdoor sports. Professional and amateur athletes should be aware of hazards caused by UV radiation. Adequate protection by water-resistant sunscreens and clothing as well as training and competition schedules with low sun exposure seem to be a reasonable recommendation.     

Radiation exposure to operating room personnel during transperineal interstitial permanent prostate brachytherapy

PURPOSE: To identify factors associated with radiation exposure (RE) to operating room personnel during transperineal interstitial permanent prostate brachytherapy (TIPPB). METHODS AND MATERIALS: Between May 1998 and December 2000, 155 patients underwent TIPPB with fluoroscopic and ultrasound guidance. Data for each case included: operating room time (OT), anesthesia time (AT), fluoroscopy time (FT), number and type of seed implanted, total seed activity, and resident participation. RESULTS: Personnel RE per case, FT, OT, and AT decreased as case number increased. Whole body badge dose per case decreased from a mean of 0.15+/-0.01 mSv (15+/-1 mrem) in 1998 to 0.074+/-0.011 mSv (7+/-1 mrem) in 2000. Average FT per case decreased from a mean of 17:27 min (range, 10:40-28:23) in 1998 to 12:08 min (range, 6:40-31:00) in 2000. Resident participation was associated with increased FT. Mean whole body and ring badge doses for the treating radiation oncologist were 0.0076 mSv/min (0.76 mrem/min) and 0.05 mSv/min (5.26 mrem/min) of FT, respectively. CONCLUSIONS: FT was the predominant factor that related to RE during TIPPB. Treating radiation oncologists were exposed to less than 20 mSv per 100 cases, significantly less than other fluoroscopically guided procedures. Nonetheless, appropriate radiation exposure precautions during TIPPB should continue.     

Cumulative Radiation Dose in Patients With Hereditary Hemorrhagic Telangiectasia and Pulmonary Arteriovenous Malformations

Purpose

To determine the cumulative effective dose (CED) of radiation from medical imaging and intervention in patients with hereditary hemorrhagic telangiectasia (HHT) who have pulmonary arteriovenous malformations and to identify clinical factors associated with exposure to high levels of radiation.

Methods

All patients with at least 1 pulmonary arteriovenous malformation were identified from the dedicated patient database of a tertiary HHT referral centre. Computerized imaging and electronic patient records were systematically examined to identify all imaging studies performed from 1989-2010. The effective dose was determined for each study, and CED was calculated retrospectively.

Results

Among 246 patients (mean age, 53 years; 62.2% women) with a total of 2065 patient-years, 3309 procedures that involved ionizing radiation were performed. CED ranged from 0.2-307.6 mSv, with a mean of 51.7 mSv. CED exceeded 100 mSv in 26 patients (11%). Interventional procedures and computed tomography (CT) were the greatest contributors, which accounted for 51% and 46% of the total CED, respectively. Factors associated with high cumulative exposure were epistaxis (odds ratio 2.7 [95% confidence interval, 1.1-6.3]; P = .02), HHT-related gastrointestinal bleeding (odds ratio 2.0 [95% confidence interval, 1.0-3.8]; P = .04) and number of patient-years (P < .0001).

Conclusions

Patients with HHT are exposed to a significant cumulative radiation dose from diagnostic and therapeutic interventions. Identifiable subsets of patients are at increased risk. A proportion of patients receive doses at levels that are associated with harm. Imaging indications and doses should be optimized to reduce radiation exposure in this population.     

Analysis of Common Deletion (CD) and a novel deletion of mitochondrial DNA induced by ionizing radiation

PURPOSE: In order to identify supportive evidence of radiation exposure to cells, we analyzed the relationship between exposure to ionizing radiation and the induction of deletions in mitochondrial DNA (mtDNA). MATERIALS AND METHODS: Using human hepatoblastoma cell line, HepG2 and its derivatives, HepG2-A, -89 and -400, established after long term exposure to X-ray, mtDNA deletions were analyzed by polymerase chain reaction (PCR) and real-time PCR after cells were subjected to radiation and genotoxic treatments. RESULTS: Common Deletion (CD), the most extensively studied deletion of mtDNA, was induced within 24 h after exposure to 5 Gray (Gy) of X-rays and was associated with replication of mtDNA. CD became undetectable several days after the exposure due to the death of cells containing mitochondria within which CD had been induced. Furthermore, we found a novel mtDNA deletion that consisted of a 4934 base-pair deletion (4934del) between nucleotide position 8435 and 13,368. A lower dose of ionizing radiation was required to induce the 4934del than for CD and this was independent of the quality of radiation used and was not induced by treatments with hydrogen peroxide (H(2)O(2)) and other genotoxic reagents including bleomycin. CONCLUSION: CD is induced by ionizing radiation, however, the amount of CD detected at a certain point in time after radiation exposure is dependent on the initial frequency of CD induced and the death rate of cells with mtDNA containing CD. The novel mtDNA deletion found in this study, therefore, will be used to determine whether cells were exposed to ionizing radiation.     

Exposure to chronic noise and fractionated X-ray radiation elicits biochemical changes and disrupts body weight gain in rat

The aim was to assess the developmental and biochemical effects resulting from separate and combined exposures to radiation and noise in adult male Sprague?–?Dawley rats. For 21 days, animals were exposed daily (1) to whole-body 121?kVp X-ray exposure (cumulative dose?=?5?Gy), (2) to random intermittent noise band-limited between 0.4 and 20 kHz; 2?h day^?–?1 86 decibels (dB) and (3) to combined exposures. Control animals were housed under ambient noise conditions 55?dB A-weighted (dBA) and sham-exposed to X-rays. Body weight gain was significantly reduced in animals exposed to either X-rays or noise, and the loss was more pronounced in animals exposed to both conditions. Neither plasma adrenocorticotropic hormone (ACTH) nor corticosterone was altered by the treatment conditions. This study corroborated previous reports that ionizing radiation exposure increased plasma levels of 8-hydroxy-2’-deoxyguanosine (8-OHDG), but no effect was observed in animals co-exposed to chronic noise. Plasma big-endothelin-1 (Big ET-1) was significantly reduced in animals exposed to a combination of noise and X-rays. The results indicated that (1) adaptation to chronic noise appeared to occur at the level of the hypothalamic pituitary adrenal (HPA) response, in spite of a compromise in overall body weight gain; and (2) ionizing radiation exposure might alter systems activated by stressor exposure and/or act independently to influence health outcomes.     

Incorporation and distribution of tritium in rats after chronic exposure to various tritiated compounds.

Rats were chronically exposed to tritiated water (3HHO) and several tritiated organic compounds [( 3H]leucine, [3H]lysine, [3H]glucose, [3H]glucosamine, [3H]thymidine and [3H]uridine) dissolved in their drinking water. An analysis of tritium in wet and dry tissues of rats at the end of 22 days' chronic exposure showed that the chemical form of the ingested tritium was more important for tritium uptake in dry tissues than in wet tissues. The concentrations of tritium in dry tissues (organically bound tritium: OBT) after the exposure to tritiated organic compounds were consistently higher than after the exposure to 3HHO. The highest concentrations of OBT were found in rats exposed to tritiated amino acids [( 3H]lysine and [3H]leucine), which were 4-9 times higher than those in rats exposed to 3HHO. The next higher concentrations of OBT were found in rats exposed to [3H]uridine. The result of radiation dose estimations at the end of chronic exposure showed that the contribution of OBT to the total dose rate was higher in the tissues of rats exposed to tritiated organic compounds than that after the exposure to 3HHO. However, the differences between the total dose rates from 3HHO and those from tritiated organic compounds were within a factor of 2.     

Computed tomography and patient risk: Facts,perceptions and uncertainties

Since its introduction in the 1970s, computed tomography (CT) has revolutionized diagnostic decision-making. One of the major concerns associated with the widespread use of CT is the associated increased radiation exposure incurred by patients. The link between ionizing radiation and the subsequent development of neoplasia has been largely based on extrapolating data from studies of survivors of the atomic bombs dropped in Japan in 1945 and on assessments of the increased relative risk of neoplasia in those occupationally exposed to radiation within the nuclear industry. However, the association between exposure to low-dose radiation from diagnostic imaging examinations and oncogenesis remains unclear. With improved technology, significant advances have already been achieved with regards to radiation dose reduction. There are several dose optimization strategies available that may be readily employed including omitting unnecessary images at the ends of acquired series, minimizing the number of phases acquired, and the use of automated exposure control as opposed to fixed tube current techniques. In addition, new image reconstruction techniques that reduce radiation dose have been developed in recent years with promising results. These techniques use iterative reconstruction algorithms to attain diagnostic quality images with reduced image noise at lower radiation doses.     

The radiation dose to surgical personnel during intraoperative radioimmunoscintimetry.

To estimate the radiation exposure to surgical personnel caused by intraoperative radioimmunoscintimetry, we measured dose rates at different distances from patients who had been injected with 950 MBq technetium-99m-labelled intact carcinoembryonic antigen (CEA)-specific antibodies (Szintimun CEA, Behring AG Marburg, FRG) for immunoscintigraphy 24 h earlier. At 0.05 m (corresponding to working positions during surgery) we found 2.0-16.0 microSv h-1 (average 6.4), which is similar to results for nuclear medicine staff. Thus, if radioimmunoscintimetry is to become a routine procedure, according to national regulations in some countries of the European Communities surgical personnel might be regarded as professionally exposed to radiation.     

南京“5.7” 192Ir源放射事故患者的生物剂量估算

目的 用3种方法估算南京"5.7" ¹⁹²Ir源放射事故患者的生物剂量,为核与辐射事故受照者的临床救治提供剂量资料。方法 受照后第5天采集患者外周血,分别进行外周血淋巴细胞染色体"双着丝粒+环"("dic+r")畸变分析、胞质分裂阻滞微核(CBMN)分析、核质桥(NPB +FHC)分析,并估算生物剂量。用双着丝粒畸变在细胞间的泊松分布情况检验照射的均匀性。结果3种方法估算的该患者受到的一次全身等效剂量分别为"dic+r"畸变分析1.51 Gy (95% CI 1.40~1.61),CBMN 分析1.47 Gy (95% CI 1.36~1.60),NPB+FHC分析1.30 Gy(95% CI 1.00~1.60)。泊松分布检验结果显示,该患者"dic+r"畸变偏离泊松分布,受到了不均匀照射。结论 外周血淋巴细胞染色体"dic+r"畸变分析、CBMN分析、NPB+FHC分析均是有效的生物剂量估算手段,对本例急性局部不均匀照射患者估算的一次全身等效剂量与临床诊断结果相符。