Meta-analysis of non-tumour doses for radiation-induced cancer on the basis of dose-rate

Purpose: Quantitative analysis of cancer risk of ionising radiation as a function of dose-rate. Materials and methods: Non-tumour dose, D(nt), defined as the highest dose of radiation at which no statistically significant tumour increase was observed above the control level, was analysed as a function of dose-rate of radiation. Results: An inverse correlation was found between D(nt) and dose-rate of the radiation. D(nt) increased 20-fold with decreasing dose-rate from 1-10(-8) Gy/min for whole body irradiation with low linear energy transfer (LET) radiation. Partial body radiation also showed a dose-rate dependence with a 5- to 10-fold larger D(nt) as dose rate decreased. The dose-rate effect was also found for high LET radiation but at 10-fold lower D(nt) levels. Conclusions: The cancer risk of ionising radiation varies 1000-fold depending on the dose-rate of radiation and exposure conditions. This analysis explains the discrepancy of cancer risk between A-bomb survivors and radium dial painters.     

Risk of solid cancer in low dose-rate radiation epidemiological studies and the dose-rate effectiveness factor

Abstract

Purpose: Estimated radiation risks used for radiation protection purposes have been based primarily on the Life Span Study (LSS) of atomic bomb survivors who received brief exposures at high dose rates, many with high doses. Information is needed regarding radiation risks from low dose-rate (LDR) exposures to low linear-energy-transfer (low-LET) radiation. We conducted a meta-analysis of LDR epidemiologic studies that provide dose-response estimates of total solid cancer risk in adulthood in comparison to corresponding LSS risks, in order to estimate a dose rate effectiveness factor (DREF).

Materials and methods: We identified 22 LDR studies with dose-response risk estimates for solid cancer after minimizing information overlap. For each study, a parallel risk estimate was derived from the LSS risk model using matching values for sex, mean ages at first exposure and attained age, targeted cancer types, and accounting for type of dosimetric assessment. For each LDR study, a ratio of the excess relative risk per Gy (ERR Gy^?1) to the matching LSS ERR risk estimate (LDR/LSS) was calculated, and a meta-analysis of the risk ratios was conducted. The reciprocal of the resultant risk ratio provided an estimate of the DREF.

Results: The meta-analysis showed a LDR/LSS risk ratio of 0.36 (95% confidence interval [CI] 0.14, 0.57) for the 19 studies of solid cancer mortality and 0.33 (95% CI 0.13, 0.54) when three cohorts with only incidence data also were added, implying a DREF with values around 3, but statistically compatible with 2. However, the analyses were highly dominated by the Mayak worker study. When the Mayak study was excluded the LDR/LSS risk ratios increased: 1.12 (95% CI 0.40, 1.84) for mortality and 0.54 (95% CI 0.09, 0.99) for mortality?+?incidence, implying a lower DREF in the range of 1–2. Meta-analyses that included only cohorts in which the mean dose was <100 mGy yielded a risk ratio of 1.06 (95% CI 0.30, 1.83) for solid cancer mortality and 0.58 (95% CI 0.10, 1.06) for mortality?+?incidence data.

Conclusions: The interpretation of a best estimate for a value of the DREF depends on the appropriateness of including the Mayak study. This study indicates a range of uncertainty in the value of DREF between 1 and about 2 after protracted radiation exposure. The LDR data provide direct evidence regarding risk from exposures at low dose rates as an important complement to the LSS risk estimates used for radiation protection purposes.     

Impact of dosimetric parameters on local control for patients treated with three-dimensional pulsed dose-rate brachytherapy for cervical cancer

PurposeTo investigate the impact of dose-volume histograms parameters on local control of three-dimensional (3D) image-based pulsed dose-rate brachytherapy (BT).Methods and MaterialsWithin a French multicentric prospective study, the data of the 110 patients treated for cervical cancer with external beam radiotherapy followed by 3D image-based and optimized pulsed dose-rate BT were analyzed. Delineation procedures were performed on magnetic resonance imaging in a minority of cases and on CT for the majority of cases, adapted from the Gynaecological Groupe Européen de Curiethérapie—European Society for Therapeutic Radiology and Oncology recommendations. Optimization procedure was left to the discretion of the treating center.ResultsAt 2 years, local control rate reached 78%. Dose to Point A, total reference air kerma, and intermediate-risk clinical target volume (IR-CTV) V₆₀ were predictive factors for local control (p = 0.001, p = 0.001, and p = 0.013, respectively). Patients with IR-CTV V₆₀ <75% had a relative risk of local recurrence of 3.8 (95% confidence interval, 1.4–11.1). There was no correlation found between the high-risk clinical target volume dosimetric parameters and local control.ConclusionsThis multicentric study has shown that 3D image-based BT provides a high local control rate for cervical cancer patients. The V₆₀ for IR-CTV was identified as an important predictive factor for local control.     

Experimental studies on the biological effects of chronic low dose-rate radiation exposure in mice: overview of the studies at the Institute for Environmental Sciences

This review summarizes the results of experiments conducted in the Institute for Environmental Sciences for the past 21 years, focusing on the biological effects of long-term low dose-rate radiation exposure on mice. Mice were chronically exposed to gamma rays at dose-rates of 0.05, 1 or 20?mGy/day for 400 days to total doses of 20, 400 or 8000?mGy, respectively. The dose rate 0.05?mGy/day is comparable to the dose limit for radiation workers. The parameters examined were lifespan, neoplasm incidence, antineoplasm immunity, body weight, chromosome aberration(s), gene mutation(s), alterations in mRNA and protein levels and trans-generational effects. At 20?mGy/day, all biological endpoints were significantly altered except neoplasm incidence in the offspring of exposed males. Slight but statistically significant changes in lifespan, neoplasm incidences, chromosome abnormalities and gene expressions were observed at 1?mGy/day. Except for transient alterations in the mRNA levels of some genes and increased liver neoplasm incidence attributed to radiation exposure, the remaining biological endpoints were not influenced after exposure to 0.05?mGy/day. Results suggest that chronic low dose-rate exposure may induce small biological effects.     

Cancer risks in a population with prolonged low dose-rate γ-radiation exposure in radiocontaminated buildings, 1983 – 2002

Purpose: To assess cancer risks in a population that received prolonged low dose-rate γ-irradiation for about 10 years as a result of occupying buildings containing ⁶⁰Co-contaminated steel in Taiwan.

Materials and methods: The cancer risks were compared with those populations with the same temporal and geographic characteristics in Taiwan by standardized incidence ratios (SIR), adjusted for age and gender. The association of cancer risks with excess cumulative exposure was further evaluated for their relative risks by the Poisson multiple regression analysis.

Result: A total of 7271 people were registered as the exposed population, with 101,560 person-years at risk. The average excess cumulative exposure was approximately 47.8 mSv (range < 1 – 2,363 mSv). A total of 141 exposed subjects with various cancers were observed, while 95 developed leukemia or solid cancers after more than 2 or 10 years initial residence in contaminated buildings respectively. The SIR were significantly higher for all leukemia except chronic lymphocytic leukemia (n = 6, SIR = 3.6, 95% confidence interval [CI] 1.2 – 7.4) in men, and marginally significant for thyroid cancers (n = 6, SIR = 2.6, 95% CI 1.0 – 5.7) in women. On the other hand, all cancers combined, all solid cancers combined were shown to exhibit significant exposure-dependent increased risks in individuals with the initial exposure before the age of 30, but not beyond this age.

Conclusions: The results suggest that prolonged low dose-rate radiation exposure appeared to increase risks of developing certain cancers in specific subgroups of this population in Taiwan.     

Mechanisms of the elimination of low dose hyper-radiosensitivity in T-47D cells by low dose-rate priming

Purpose:?To investigate the mechanisms of elimination of low-dose hyper-radiosensitivity (HRS) in T-47D cells induced by 0.3?Gy low dose-rate (LDR) priming.

Materials and methods:?The mitotic ratio was measured using mitotic marker histone H3 phosphorylation in LDR primed as well as untreated T-47D cells. The HRS response in unprimed cells receiving medium which was irradiated after being harvested from unprimed cells was measured with or without serum present during cell conditioning. 4,6-benzylidene-D-glucose (BG) was used to inhibit protein synthesis during LDR priming.

Results:?LDR primed T-47D cells were HRS-deficient and showed a decrease in mitotic ratio with increasing dose while unprimed, i.e., HRS-competent T-47D cells, showed no decrease in mitotic ratio for doses in the HRS-range. HRS was eliminated in LDR primed cells, in cells receiving medium transfer from LDR primed cells, and in cells receiving LDR irradiated medium harvested from unprimed cells. The efficacy of the transferred medium depended on the presence of serum during cell conditioning. LDR priming eliminated HRS even in the presence of protein synthesis inhibitor BG.

Conclusions:?LDR priming of T-47D cells as well as LDR priming of medium conditioned on T-47D cells induce a factor in the medium which cause the early G₂-checkpoint to be activated in recipient cells by doses normally in the HRS dose-range.     

Estimating cancer induction risk from abdominopelvic scanning with 6- and 16-slice computed tomography

Purpose: The biological effects of ionizing radiation (BEIR VII) report estimates that the risk of getting cancer from radiation is increased by about a third from current regulation risk levels. The propose of this study was to estimate cancer induction risk from abdominopelvic computed tomography (CT) scanning of adult patients using 6- and 16-slice CT scanners.

Materials and methods: A cross-sectional study on 200 patients with abdominopelvic CT scan in 6- and 16-slice scanners was conducted. The dose-length product (DLP) and volume CT Dose Index (CTDI_vol) values from the scanners as well as the effective dose values from the ImPACT CT patient dosimetry calculator with the biological effects of ionizing radiation (BEIR VII) method were used to estimate the cancer induction risk.

Results: The mean (and standard deviation) values of CTDI_vol and DLP were 6.9 (±1.07) mGy and 306.44 (±?60.57) mGy.cm for 6-slice, and 5.19 (±0.91) mGy and 219.7 (±49.31) mGy.cm for 16-slice scanner, respectively. The range of effective dose in the 6-slice scanner was 2.61–8.15 mSv and, in the 16-slice scanner, it was 1.47–4.72 mSv. The mean and standard deviation values of total cancer induction risk in abdominopelvic examinations were 0.136?±?0.059% for men and 0.135?±?0.063% for women in the 6-slice CT scanner. The values were 0.126?±?0.051% for men and 0.127?±?0.056% for women in the 16-slice scanner.

Conclusions: The cancer induction risk of abdominopelvic scanning was noticeable. Therefore, radiation dose should be minimized by optimizing the protocols and applying appropriate methods.     

射线能量对子宫内膜癌调强放疗计划质量的影响

目的 研究射线能量对子宫内膜癌术后全盆腔调强放射治疗计划质量的影响.方法 选择10例子宫内膜癌术后患者,对每例患者分别设计6和18 MV的全盆腔调强放射治疗计划.所有计划均使用相同的布野方案和剂量体积约束.比较两组计划的靶区、危及器官和正常组织的剂量分布.结果 6和18 MV计划的平均PTV100分别是95.6%和95.3%(检验值P=0.26),Dmean分别是52.55 Gy和52.60 Gy(P=0.54),适形指数分别是0.87和0.88(P=0.03),均匀性指数均为1.10(P=0.38).18 MV计划较6 MV计划正常组织的平均积分剂量下降了2.4%(P=0.001),小肠和结肠的平均V30和V50分别下降了4.2%(P=0.006)和3.3%(P=0.046),其他危及器官的剂量分布间差异无统计学意义.结论 对于子宫内膜癌的术后全盆腔调强放射治疗,18 MV计划比6 MV计划剂量分布的适形度更好,能够更好地保护正常组织、小肠和结肠.两组计划靶区的覆盖度和剂量分布的均匀性,以及直肠、膀胱和盆腔骨的保护相当.     

The involvement of serum serotonin levels producing radiation-induced bystander effects for an in vivo assay with fractionated high dose-rate (HDR) brachytherapy

Abstract

Purpose: The primary goal of this investigation was to observe whether measurable levels of bystander factor(s) can be detected in esophageal carcinoma patients’ urine samples taken after undergoing high dose rate (HDR) intraluminal brachytherapy (ILBT). However, a small pilot study was developed to evaluate whether serotonin [5-Hydroxytryptamine (5-HT)] serum levels play an active role in the mechanisms of radiation-induced bystander effects (RIBE) at high doses.

Materials and methods: In the present study, a colony-forming in vivo assay was developed and used for the detection of non-targeted effects. Samples of urine were collected from five esophageal carcinoma patients undergoing fractionated HDR-ILBT. To observe whether 5-HT modulates the bystander effect at higher doses, different batches of foetal bovine serum (FBS) and 5-HT were tested on the same urine samples before and after brachytherapy.

Results: Some of our data suggests statistically significant evidence for serotonin playing an active role as a signalling molecule at higher doses when patients underwent HDR-ILBT.

Conclusion: However, a more thorough investigation, with a larger sample size, is warranted before serotonin can be known to play a role in bystander effects at this particular dose range and treatment regime.     

阳江高本底地区辐射致癌危险分析(1979-2002年)

目的 分析1999-2002年随访资料,并与既往1979-1998年资料合并分析,以期进一步提高辐射致癌危险估计的统计效能;调整个体吸烟因素,重新估计高本底地区小剂量电离辐射的致癌危险。 方法 高本底地区和对照地区居民癌症研究采用队列研究方法,分阶段对研究对象进行随访。本研究阶段首先搜集1999-2002年的癌症死亡资料,并初步分析1999-2002年高本底地区居民癌症死亡危险;其次通过ID号连接记录,将1999-2002年研究数据与1979-1998年研究数据进行合并,分析1979-2002年高本底地区居民的癌症死亡危险及调整吸烟后高本底地区居民的辐射致癌死亡危险。用Epicure软件中的DATAB模块计算人年数,用AMFIT模块的Poisson回归模型估算高本底地区居民癌症死亡的相对危险(RR)、超额相对危险系数(ERR/Sv)和可信区间(CI)。 结果 高本底地区和对照地区队列研究1999-2002年共随访76 264人,累积观察300 523人年,期间共死亡2 267例,其中癌症死亡239例。1979-2002年合并资料共随访125 079人,累积观察2 293 463人年,死亡14 711例,其中癌症死亡1 441例。1979-2002年癌症死亡分析结果显示,经性别、年龄调整后,高本底地区全癌症死亡的相对危险RR=0.99 (95%CI:0.89~1.11),高本底地区和对照地区相比癌症死亡,结果差异无统计学意义(P>0.05);1979-2002年高本底地区全部癌症死亡的超额相对危险系数(ERR/Sv)为-0.01(95%CI:-0.50~0.64)。调整吸烟后,1987-2002年高本底地区全癌症死亡相对危险RR=1.00(95%CI:0.87~1.15),差异无统计学意义(P>0.05);高本底地区全部癌症死亡的ERR/Sv为0.01(95%CI:-0.56~0.81)。 结论 未发现高本底地区小剂量电离辐射引起居民癌症死亡危险的增加。调整吸烟后,高本底地区全部癌症死亡与对照地区相比,差异仍无统计学意义,但超额相对危险(ERR)较调整前稍增大。     

Biological basis of radiation protection needs rejuvenation

Abstract

Purpose: Human beings encounter radiation in many different situations – from proximity to radioactive waste sites to participation in medical procedures using X-rays etc. Limits for radiation exposures are legally regulated; however, current radiation protection policy does not explicitly acknowledge that biological, cellular and molecular effects of low doses and low dose rates of radiation differ from effects induced by medium and high dose radiation exposures. Recent technical developments in biology and medicine, from single cell techniques to big data computational research, have enabled new approaches for study of biology of low doses of radiation. Results of the work done so far support the idea that low doses of radiation have effects that differ from those associated with high dose exposures; this work, however, is far from sufficient for the development of a new theoretical framework needed for the understanding of low dose radiation exposures.

Conclusions: Mechanistic understanding of radiation effects at low doses is necessary in order to develop better radiation protection policy.     

头、胸部CT扫描所致儿童甲状腺剂量估算及其癌症风险预测

目的 估算儿童接受头部、胸部CT扫描所致其甲状腺剂量及其癌症风险。方法 通过医院影像归档和通信系统(PACS)提取某医院2012年接受头部、胸部CT扫描儿童DCIOM文件,利用DCMTK软件获取患者CT扫描参数,使用CT-Expo剂量估算软件估算CT扫描所致患者甲状腺剂量,利用美国电离辐射生物效应委员会(BEIR)Ⅶ风险模型结合中国2008年癌症发病率及寿命表预测单次头部、胸部CT扫描所致儿童甲状腺癌的风险。结果 不同年龄段儿童CT扫描参数大致相同,单次头部CT扫描所致儿童(男、女)甲状腺剂量范围为1.2~2.0 mGy,其甲状腺癌风险最高的为新生儿(女)9.6/10万人口;单次胸部CT扫描所致儿童(男、女)甲状腺剂量范围约为8.1~38.0 mGy,其甲状腺癌风险最高为新生儿(女)244.7/10万人;CT所致儿童甲状腺剂量与癌症风险均随其年龄的增加而逐渐减小。结论 胸部CT扫描所致儿童甲状腺剂量较高,尤其是对于新生儿患者,应注意儿童接受胸部CT扫描时对甲状腺及其他辐射敏感器官的防护。     

射线能量对子宫内膜癌调强放疗计划质量的影响

目的 研究射线能量对子宫内膜癌术后全盆腔调强放射治疗计划质量的影响。方法 选择10例子宫内膜癌术后患者,对每例患者分别设计6和18 MV的全盆腔调强放射治疗计划。所有计划均使用相同的布野方案和剂量体积约束。比较两组计划的靶区、危及器官和正常组织的剂量分布。结果 6和18 MV计划的平均PTV₁₀₀分别是95.6%和95.3% (检验值P=0.26), D_mean分别是52.55 Gy和52.60 Gy(P=0.54),适形指数分别是0.87 和 0.88 (P=0.03),均匀性指数均为1.10 (P=0.38)。18 MV计划较6 MV计划正常组织的平均积分剂量下降了2.4% (P=0.001),小肠和结肠的平均V₃₀和V₅₀分别下降了4.2% (P=0.006)和3.3% (P=0.046),其他危及器官的剂量分布间差异无统计学意义。结论 对于子宫内膜癌的术后全盆腔调强放射治疗,18 MV计划比6 MV计划剂量分布的适形度更好,能够更好地保护正常组织、小肠和结肠。两组计划靶区的覆盖度和剂量分布的均匀性,以及直肠、膀胱和盆腔骨的保护相当。     

Interfractional fluctuation of rectal dose in high dose rate brachytherapy for prostate cancer

Purpose The aim of the study was to explore the cause of the difference in the maximal rectal dose between the first and second high dose rate (HDR) brachytherapy applications by comparing the thickness of the anterior rectal wall. Materials and methods The rectal dose and the thickness of the anterior rectal wall were analyzed in 26 patients with prostate cancer. After undergoing external beam radiation treatment with a total isocenter dose of 50 Gy, they were treated with HDR brachytherapy of 7.5 Gy/fraction, two fractions daily. The interval between the first HDR brachytherapy session and the second was 5 h. The rectal doses were directly surveyed during irradiation of the HDR brachytherapy. Thickening of the anterior rectal wall was measured at the same level by axial computed tomography scans obtained before the first and second HDR brachytherapy applications. Results The maximal surveyed rectal doses during the first and second HDR brachytherapy applications were 188 ± 51 cGy and 220 ± 35 cGy, respectively (P < 0.01). The fluctuation ratio exceeded 1 in each case. The thickness of the anterior rectal wall before the first and second HDR brachytherapy applications was 18.78 ± 4.34 mm and 14.95 ± 4.09 mm (P < 0.01), respectively. The fluctuation difference exceeded 0 in each case. Conclusion The different rectal dose is attributable to thinning of the anterior rectal wall. The total rectal dose is within the range of doses at risk of exerting a toxic effect on the rectum.     

宫颈癌二维近距离后装治疗中危及器官参考点剂量与三维体积剂量的相关性研究

目的 利用宫颈癌二维近距离后装治疗中危及器官（OARs）点剂量预测其三维体积剂量,评估在特定条件下,二维计划OARs体积剂量能否满足三维后装剂量限值要求。方法 回顾性分析基于CT图像的10例宫颈癌患者近距离后装治疗计划,将处方参考点剂量定为600 cGy,膀胱和直肠参考点剂量<360 cGy,设计并优化得到二维后装治疗计划。采用Pearson相关分析法对膀胱、直肠参考点剂量及OARs体积受量做相关性分析,利用线性回归方法得出膀胱、直肠参考点与其体积剂量的线性方程。结果 膀胱、直肠参考点剂量分别与其D_{1 cm³}、D_{2 cm³}、D_{5 cm³}和平均剂量显著正相关（r=0.559~0.668,P<0.05）;膀胱、直肠参考点剂量分别是其D_{2 cm³}的1.404和1.181倍;内外照射完成后膀胱、直肠D_{2 cm³}的相当于200 cGy分次等效生物剂量（EQD2）分别为8 410.0和6 827.0 cGy,均低于二者体积剂量限值。结论 利用膀胱、直肠参考点剂量能在一定程度上预测其体积剂量,对于满足膀胱、直肠参考点剂量低于处方剂量60%二维近距离后装计划,可将膀胱、直肠体积受量控制在相对安全的剂量范围内。而由于缺乏对小肠、乙状结肠剂量检测,二维后装计划在临床使用上仍然具有很大局限性。     

单侧乳腺癌放疗中健侧乳腺受照剂量及其诱发癌症风险预测

目的 分析单侧乳腺癌放疗所致健侧乳腺的剂量,并估算放疗诱发健侧乳腺癌的风险。方法 在同一医院调查49例接受单侧乳腺放疗患者的基本情况,从治疗计划系统上获取其健侧乳腺的辐射剂量并进行统计分析;利用美国电离辐射生物效应委员会报告Ⅶ第2部分（BEIR Ⅶ phase 2）推荐的风险模型,结合我国人口寿命表,预测不同年龄段单侧乳腺癌患者接受放疗诱发健侧乳腺癌的风险。结果 患者的处方剂量均为50 Gy,健侧乳腺的平均剂量为（1.21±0.89）Gy （0.14~3.59 Gy）,最大点剂量平均为（17.42±13.20）Gy （0.98~45.27 Gy）;健侧乳腺的最大点剂量和平均剂量变化幅度大,且有显著相关性（R=0.527,P=0.000）,不同年龄段患者的健侧乳腺平均剂量差异无统计学意义（P>0.05）。基于健侧乳腺的平均剂量,估算出受照年龄为35、40、50、60、70和80岁患者的健侧乳腺癌终生归因风险分别为2 449/10万人、1 857/10万人、994/10万人、446/10万人、173/10万人和55/10万人。结论 患者接受单侧乳腺癌放疗过程中,其健侧乳腺剂量可达1 Gy水平,可能增加健侧乳腺癌发生风险对年轻患者不容忽视,在制定放射治疗计划时应尽可能控制对患者健侧乳腺的照射。     

河南省8台加速器调强放疗靶体积和危及器官剂量及二维剂量分布验证方法研究

目的研究用热释光剂量计(TLD)和免冲洗胶片(film)测量调强放疗(IMRT)计划靶区(PTV)、危及器官(OAR)处方剂量和二维剂量分布验证方法。方法选择河南省的8台不同型号医用直线加速器,国际原子能机构(IAEA)提供聚苯乙烯专用模体,经CT模拟定位机扫描,影像传输至治疗计划系统(TPS),分别勾画PTV和OAR的处方剂量,能量6 MV X射线。对模体实施IMRT照射,照射后的TLD和胶片邮寄至中国疾病预防控制中心辐射防护与核安全医学所二级标准剂量学实验室测量和估算。结果按IAEA要求,对PTV和OAR处方剂量,TLD测量剂量与TPS计划处方剂量的相对偏差为±7.0%。对PTV的剂量验证结果表明,8台加速器的相对偏差在-0.3%~6.9%范围内,符合要求。对OAR剂量验证结果表明,6台加速器的相对偏差在-7.0%~0.3%范围内,符合要求,2台加速器的相对偏差在-10.8%^-8.4%范围内,不符合要求。按IAEA要求,二维剂量分布3 mm/3%通过率≥90%。7台加速器通过率在90.2%~99.9%范围内,符合要求,1台加速器通过率为70.0%,不符合要求。结论免冲洗胶片和热释光剂量计验证调强放疗靶体积和危及器官处方剂量及二维剂量分布,方法简单可靠,是开展调强放射治疗质量控制的重要步骤,可为医疗机构或第三方服务机构核查临床处方剂量提供有力支撑。     

四川省7台加速器调强放疗靶体积和危及器官剂量及二维剂量分布验证方法研究

目的研究用放射性免冲洗胶片(film)和热释光剂量计(TLD)测量调强放射治疗(IMRT)靶体积(PTV)、危及器官(OAR)剂量和二维剂量分布验证方法。方法选择7台医用直线加速器(瓦里安、医科达、西门子),国际原子能机构(IAEA)提供的聚苯乙烯专用模体,经CT扫描,影像传给放射治疗计划系统(TPS)制定治疗计划,能量6 MV X射线束,按治疗计划对模体实施照射。照射后的TLD和胶片邮寄到中国疾病预防控制中心辐射防护与核安全医学所二级标准剂量学实验室测量和估算。结果IAEA要求,对靶体积和危及器官剂量,TLD测量值与TPS计划剂量值的相对偏差应为±7.0%。靶体积结果:5台加速器的的相对偏差在-4.0%~3.4%范围内,符合要求,2台加速器的相对偏差在-7.0%~10.6%范围内,不符合要求。危及器官结果:4台加速器的相对偏差在-5.6%~3.3%范围内,符合要求,3台加速器的相对偏差在-20.8%~11.5%范围内,不符合要求。IAEA要求,二维剂量分布3 mm/3%通过率应≥90%。5台加速器的通过率在91.8%~98.5%范围内,符合要求,2台加速器的通过率分别为45.0%和77.0%,不符合要求。结论用TLD和放射性免冲洗胶片验证调强放射治疗靶体积、危及器官和二维剂量分布通过率,方法可行,可推广大范围运用到质量核查中,也可用于医院内部核查。     

江苏省8台加速器调强放疗靶体积和危及器官剂量及二维剂量分布验证方法研究

目的用热释光剂量计(TLD)及免冲洗胶片(film)测量调强放射治疗靶体积(TPV)、危及器官(OAR)剂量和二维剂量分布验证方法。方法选择8台医用直线加速器(瓦里安、医科达、西门子),国际原子能机构(IAEA)提供的聚苯乙烯专用模体,经CT扫描,影像传给放射治疗计划系统(TPS)制定治疗计划,勾画PTV,OAR的处方剂量,计算相应的监督单位(MU),能量6 MV X射线束,对模体实施调强放疗(IMRT)照射。照射后的TLD和胶片邮寄至中国疾病预防控制中心辐射防护与核安全医学所二级标准剂量学实验室测量和估算。结果按IAEA要求,对于靶体积和危及器官剂量,TLD测量剂量值与TPS计划剂量值的相对偏差为±7.0%。靶体积结果表明,8台加速器的TLD测量值与TPS计划值的相对偏差为0.6%~5.9%,符合要求。危及器官结果表明,8台加速器的TLD测量值与TPS计划值相对偏差为-0.6%~7.0%,符合要求。按IAEA要求,二维剂量分布3 mm/3%通过率为90%。8台加速器的胶片测量与TPS计划二维剂量分布通过率为90.2%~100.0%,符合要求。结论用TLD和放射性免冲洗胶片验证调强放射治疗靶体积、危及器官和二维剂量分布通过率,方法可行,可推广大范围运用到质量核查中,也可用于医院内部核查。     

湖北省7台加速器调强放疗靶体积和危及器官剂量及二维剂量分布验证方法研究

目的研究用热释光剂量计(TLD)和胶片(film)测量调强放疗(IMRT)靶体积(PTV)、危及器官(OAR)和二维剂量分布方法。方法选择湖北省7家三甲医院的7台不同型号医用直线加速器,国际原子能机构(IAEA)提供的聚苯乙烯专用模体,TLD和放射性免冲洗胶片(EPT3),经CT模拟定位机扫描模体,影像传输至治疗计划系统(TPS),分别勾画PTV、OAR处方剂量和相应的监督单位(MU),能量6 MV X射线束,对模体实施IMRT照射,照射后的TLD和胶片邮寄至中国疾病预防控制中心辐射防护与核安全医学所二级标准剂量学实验室测量和估算。结果按IAEA要求,OAR和PTV的TLD测量值与TPS计划处方剂量的相对偏差为±7.0%。7台加速器PTV的TLD测量值与TPS计划值相对偏差在-5.4%~6.5%范围内,均符合IAEA的要求;5台加速器的OAR的TLD测量值和TPS计划值相对偏差在-2.2%~6.7%范围内,2台加速器相对偏差为-8.6%和8.2%,超出IAEA的要求。按IAEA要求,二维剂量分布3 mm/3%通过率为90%。7台加速器的二维剂量分布通过率在90.3%~98.9%范围内,均符合IAEA要求。结论使用TLD和胶片做IMRT剂量验证,科学性强,操作简单,TLD和胶片便于邮件寄送,该方法可运用于今后对放疗机构调强放疗剂量大范围的质量核查。