肺部计数器测量肺内氡子体的可行性研究

目的 探讨利用肺部计数器对工作人员肺内氡子体测量的可行性。方法 应用活性炭吸附一定量的氡,结合躯干体模,对肺部计数器测量氡短寿命子体的探测效率进行刻度。结果 通过对测量数据进行处理分析和相关文献资料的调研,结合测量系统的性能,估算出了体外直接测量氡子体²¹⁴Bi的时机。结论 通过实验,得出了利用肺部计数器从体外直接测量氡的短寿命子体是可行的,但必须保证工作人员从现场离开后短时间内进行监测。     

用两种效率刻度方法测量比对土壤介质放射性核素

目的 为了检验和提高γ谱仪测量准确性。方法 本实验室参加了由IAEA组织的土壤介质放射性核素测量比对活动。结果 分别采用由标准源刻度的和无源模拟刻度的效率曲线法,使用低本底高纯锗γ谱仪对土壤样品进行测量,通过相对偏差、Z检验、U检验、准确度和精确度等综合检验方法对测量结果进行了比对测试。结论 此次比对数据结果为"可以接受",从而验证了效率曲线刻度来源(包括无源模拟)的可靠性。     

屏蔽室内氡对全身和肺部计数器测量性能的影响

目的 测定铅屏蔽室内氡对全身和肺部计数器测量¹³⁷Cs和²⁴¹Am的最小可探测活度的影响程度。方法 通过对屏蔽室进行通室外空气降氡。用测氡仪对屏蔽室内的氡浓度进行连续测量,同时测量全身和肺部计数器的本底谱。结果 通过实验数据分析表明,通风降氡可以降低全身和肺部计数器测量¹³⁷Cs和²⁴¹Am的最小可探测活度14%至23%。结论 对屏蔽室通风降氡,能有效地提高全身和肺部计数器的探测性能。     

一种基于蒙卡解析耦合的无源效率刻度方法

目的 将蒙卡模拟与解析计算相结合,建立一种无源效率刻度方法。方法 通过蒙卡模拟对所需型号的探测器进行点对点探测效率计算,建立探测效率网格;从探测效率网格中插值,并使用数值积分方法对常用的点源、圆盘、圆柱、烧杯、球形、U型管、马林杯样品的探测效率进行解析。结果 使用上述耦合方法进行无源效率刻度计算,结果表明：0.2～3 MeV能量范围内的刻度结果与使用蒙卡模拟的刻度结果相对偏差大部分在10%以内,最大相对偏差为18.06%,计算时间缩短了至少86%。应用上述耦合方法对ORTEC公司产的某型号HPGe探测器进行点源无源效率刻度,与实验刻度结果吻合很好,相对偏差均在10%以内。结论 该方法可以推广到HPGe、LaBr₃、NaI等多种探测器的无源效率刻度实际应用中。     

便携式γ谱仪ISOCS无源效率刻度方法的研究

目的 通过对便携式HPGe γ谱仪无源效率刻度结果的准确性验证为核事故现场应急测量结果的可靠性提供依据。方法 采用ISOCS无源效率刻度系统方法对三种环境标准源样品,气溶胶滤膜、液体样和生物样进行验证实验。结果 便携式HPGe γ谱仪对人工核素的测量结果是可接受的,尤其对高能核素的测量准确度较高。结论 无源效率刻度法可用于核事故应急现场对简单体源模型的活度测量。     

用标准样品刻度γ能谱仪效率值的变化比较

目的 比较γ能谱仪刻度用标准样品探测效率的差别,为样品测量分析中的效率校正提供参考。方法 利用水、鱼肉灰、蔬菜灰和大米灰四个标准样品,在同一台HPGe γ能谱仪进行测量分析,比较效率值的相对偏差。结果 水样品与生物灰样品由于样品的几何形状和样品介质不同,导致各个能量点的效率值都有较大差别。三个生物灰样品仅装样密度不同,各个能量点的效率值略有差别。结论 γ能谱仪刻度时应首先保障被测样品与效率刻度用样品在几何形状和介质上一致,其次是样品装样密度应尽量一致,当密度不一致时效率的偏差在低能部分表现较大,应注意样品中低能区的自吸收校正问题。     

加速器吸收剂量测量的国标法与IAEA法的比较

目的 介绍推广IAEA方法。方法 将国标法与IAEA法进行比较。结果 国标法误差较大,IAEA法测量精确。结论 对光子和电子吸收剂量测量时IAEA法简捷、易于执行,其准确度达到国际上可以接受的一致性。     

核事故应急条件下放射性碘内污染快速判断方法的研究

目的 探讨核事故应急条件下放射性碘内污染快速判断方法。方法 用8192道HPGγ谱仪直接测量法,探测8种相同浓度不同体积(25ml~200ml)的¹³¹I标准溶液的效率;测量39名核医学门诊接受甲状腺功能检查而结果正常者以及39名无甲状腺疾患正常健康人员的24h尿样中¹³¹I放射性活度。结果 对于不同容积的¹³¹I样品,容积越小探测效率越高;正常健康人群测量系统给出的尿样的水平为(0.52±0.26)Bq/d;甲状腺功能正常服碘者24h的摄入排出率为28.2%±14.4%。结论 HPGEγ谱仪测量不小于25ml小容积尿样中¹³¹I活度的方法,适用于核事故应急条件下放射性碘内污染快速判断;利用甲状腺功能正常服碘者的摄入排泄函数值快速估算受污人员的内污染程度。     

铱-192后装机放射源的刻度

目的 为了治疗的准确性,对放射源进行刻度。方法 通过测量照射量率来刻度放射源。结果 误差在临床许可范围内。结论 测量结果可用于指导临床应用。     

一种便携式应急甲状腺辐射监测仪的研制

目的 为满足放射性事故情况下的应急准备和响应的要求,需要对相关人员进行甲状腺的辐射测量,快速估算人员受照射剂量,尽快确定污染水平及核素种类以便进行相应处理。方法 本文研制了一种便携式的甲状腺辐射监测仪,用于应急状态下实现快速医学响应。本文利用蒙特卡罗方法模拟计算了不同尺寸NaI晶体的探测效率;并重点考虑了轻便性和可移动性的功能设计。本文还开发了甲状腺剂量评价软件,实现对放射性碘的摄入量和待积剂量当量的准确估算。结果 设备实现稳定可靠运行,其中能量分辨率为7%（662 keV时）,探测下限小于15 Bq（对于¹³¹I）,探测速度达到每小时不小于20人,总重30 kg,满足轻便、可快速移动的要求。结论 在核事故情况下,设备能快速运送到事故现场,满足应急救援队伍现场开展甲状腺的辐射监测和评估的要求,填补了技术空白。     

Measurement of dose in radionuclide therapy by using Cerenkov radiation

This work aims to determine the relationship between Cerenkov photon emission and radiation dose from internal radionuclide irradiation. Water and thyroid phantoms were used to simulate the distribution of Cerenkov photon emission and dose deposition through Monte Carlo method. The relationship between Cerenkov photon emission and dose deposition was quantitatively analyzed. A neck phantom was also used to verify Cerenkov photon detection for thyroid radionuclide therapy. Results show that Cerenkov photon emission and dose deposition exhibit the same distribution pattern in water phantom, and this relative distribution relationship also existed in the thyroid phantom. Moreover, Cerenkov photon emission exhibits a specific quantitative relation to dose deposition. For thyroid radionuclide therapy, only a part of Cerenkov photon produced by thyroid could penetrate the body for detection; therefore, the use of Cerenkov radiation for measurement of radionuclide therapy dose may be more suitable for superficial tumors. This study demonstrated that Cerenkov radiation has the potential to be used for measuring radiation dose for radionuclide therapy.     

射波刀脊柱追踪仰卧与俯卧位照射精度的对比

目的 利用头颈、仿真人和肺部模体检测射波刀IGRT治疗脊柱追踪时仰卧与俯卧位照射精度并进行对比分析,为俯卧位脊柱追踪的应用提供参考数据。方法 用CT对装有胶片的头颈、仿真人和肺部模体分别进行仰卧和俯卧位扫描,然后利用治疗计划系统分别设计仰卧和俯卧位模体计划,执行模体计划。利用E2E软件分析照射精度,对比这种两种卧姿的照射精度。结果 仰卧与俯卧位精度检测结果,颈椎的追踪精度分别为0.77和0.87 mm,胸椎的为0.78和0.76 mm,腰椎的为0.89和0.80 mm,骶椎的为1.90和2.27 mm,4个不同椎体仰卧与俯卧位精度偏差分别为:0.01、0.02、0.09和0.37 mm。结论 对于这三种静态模体,颈椎、胸椎、腰椎和骶椎仰卧与俯卧位脊柱追踪精度偏差很小,可以认为具有同等的照射精度。     

自制TOMO模体与Cheese模体在螺旋断层放疗系统剂量测量的比较研究

目的 本文通过自制TOMO模体与Cheese模体在TOMO中剂量测量的差异比较，初步验证自制TOMO模体用于临床的可行性。方法 在TOMO固定照射野下，模体中心轴上取5个不同测试深度，用A1SL型电离室及TomoElectrometer静电计分别测量各位置的电荷量，依据美国医学物理家协会（AAPM） TG-148号报告和TG-51号报告，计算相应位置的吸收剂量，并比较两种模体的剂量差异。结果 自制TOMO模体和Cheese模体中5个不同深度剂量的相对偏差分别为0.35%、0.3%、0.3%、0.34%和0.0%。结论 两种模体剂量测量相对偏差均小于0.35%，表明自制TOMO模体与Cheese模体在剂量性能上具有一致性，自制TOMO模体可用于TOMO的剂量测量。     

In-vivo thyroid 125I monitoring method using imaging plate

A new in vivo thyroid monitoring system was devised with radioluminography using an imaging plate. The counting features of the system were investigated by using a neck-thyroid phantom. A clear thyroid image was obtained at thin prethyroid tissue thicknesses and short distances between IP and neck surface. The characteristic 125I thyroid image made it possible to visually confirm that the thyroid definitely accumulated 125I. The counting efficiency in 100xcps Bq(-1) of the imaging plate system was determined by setting a region of interest on the thyroid image resulting in a maximum efficiency of 0.5%. The higher efficiency was obtained for thinner tissue thickness overlaying the thyroid, smaller thyroids, and shorter distances between the imaging plate and neck surface. The imaging plate thyroid monitoring system was sensitive to thyroid 125I. Its minimum detection limit of 23 Bq for a 10-min measurement was considerably lower than the annual thyroid burden limit of 300 kBq.     

New in-vivo calibration phantoms and their performance

New in-vivo calibration phantoms (anthropometric phantoms) were developed to meet the needs for Japanese standard phantoms. Two important characteristics of these phantoms were that (1) they were designed using Japanese body size survey data, and (2) they were designed so that they can be adapted to various positions or geometries. The performance of these phantoms was tested with respect to body size, activity distribution along the axis, and counting efficiency. The actual dimensions of the anthropometric phantoms were compared with the survey data. Most items (31 of 47) indicated good agreement between the actual values and the survey data for the adult anthropometric phantom. The activity distribution for the anthropometric phantoms was compared with that for block phantoms that simulate a uniform activity distribution. The anthropometric phantoms have some gaps in their joints. The measurement results, however, indicated that these gaps did not significantly affect the overall accuracy of the measurements. Differences in counting efficiency between the block phantoms and the anthropometric phantoms for the same age were no more than 6%.     

模拟后装放射源卡源处置时放射工作人员受照剂量研究

目的 估算放疗技师在应急处理后装放射源卡源过程中的受照剂量。方法 使用仿真人体盆腔模型替代宫颈癌患者,填充石蜡的假人替代放疗技师,模拟放射源在患者的子宫口位置发生卡源事故的场景,采用热释光剂量仪测量假人的4个敏感器官（晶体、甲状腺、乳腺、睾丸）表面不同时长内的受照剂量,并计算穿戴0.35 mm铅当量的防护用品的防护效果。结果 按¹⁹²Ir源强370 GBq计,无防护情况下各敏感器官在不同处理时间的受照剂量均小于0.12 mGy。在穿戴防护用品之后,各敏感器官的受照剂量减少1.7%~19.8%。结论 放疗技师在没有穿戴防护用品,¹⁹²Ir源强为370 GBq,应急处理时间35 s内的入射体表剂量不超过0.12 mGy,只相当于做一次X线摄影检查的受照剂量。     

自制AQA模体应用于射波刀质控的可行性分析

目的 探讨自制AQA模体应用于射波刀自动质量保证检测中的可行性。方法 在射波刀治疗计划系统中设计相同的自动质量保证检测治疗计划,分别在第四代（G4）射波刀和第五代（VSI）射波刀模式下使用自制AQA模体和AQA模体在相同条件下执行检测,各重复测量5次,分析比较2种模体检测结果的差异。结果 自制AQA模体与AQA模体在G4射波刀下自动质量保证检测总偏差结果分别为（0.28±0.12） mm和（0.28±0.15） mm,在VSI射波刀下检测结果分别为（0.46±0.19） mm和（0.50±0.07） mm,差异均无统计学意义（P> 0.05）;总偏差检测结果均小于1.0 mm,符合WS 667—2019 《机械臂放射治疗装置质量控制检测规范》。结论 自制AQA模体与AQA模体在自动质量保证检测中结果具有一致性,自制AQA模体可用于射波刀质量控制。     

非均匀自制模体的临床可应用性实验分析

目的 对自制等效于人体多种组织密度模体,进行临床质控可应用性实验分析。方法 自制密度接近骨骼、肺、空腔及软组织的模体材料,并组合制作非均匀验证模体,然后对器官等效材料的电子密度进行比较。选用本科收治的10例肺癌患者,分别在该自制模体和固体水模体上进行调强计划剂量验证,比较2种模体在剂量验证领域的特点,并分析自制模体在TPS上的计算值与实测值的剂量学差异,采用SPSS 21.0软件进行统计分析。结果 使用自制模体和固体水模体进行剂量验证,γ通过率（3 mm/3%）均在90%以上。应用自制模体进行剂量验证的测量值,比使用固体水模体时偏大,测量值最大偏差为11.5%。2种模体间的剂量验证γ通过率AD组和RD组差异无统计学意义（P> 0.05）。结论 自制模体符合临床应用的精度要求,可应用在放射治疗计划验证。     

Voxel phantoms: the new ICRP computational phantoms: how do they compare?

Two new voxel phantoms, ICRP Adult Female (AF) and ICRP Adult Male (AM), have been compared with BOMAB (BOttle Mannikin ABsorber) phantoms and other voxel phantoms of similar size (NORMAN and VIP-Man) using Monte Carlo simulations to assess their counting efficiencies in a whole body counter. The results show that the ICRP phantoms, compared with NORMAN and VIP-Man, had counting efficiencies that ranged from 3% to 59% higher over the energy range 122 keV to 1,836 keV, a trend that is also exhibited by the comparable BOMAB phantoms. A comparison of all the voxel phantoms' results to those of the BOMAB phantom corresponding to reference man shows that the NORMAN and VIP-Man have mostly lower counting efficiencies, whereas the ICRP phantoms have higher counting efficiencies than the PM (Phantom Male) BOMAB phantom. This could be due to differences in the internal structure of each of the voxel phantoms. As expected, the ICRP AF (female voxel) had the highest efficiency due to being the smallest of all the phantoms.     

The sliced bomab phantom: a new variant for intercomparison

Previously, this laboratory conceptualized a new phantom for calibration or performance testing of whole body counters using Monte Carlo simulations. This paper describes the physical reality that was created from the Monte Carlo design project and compares its counting efficiency to that of a conventional BOMAB phantom using two whole body counters. In one counter (NaI based) the agreement between the two phantoms was +/-8% and in the second counter (Ge based) the agreement was +/-5% at all the energies measured (126 keV, 661 keV, 1172 keV, 1330 keV). The advantage of the sliced phantom is that the sources are solid, sealed, and cannot leak activity thereby simplifying packing for shipment if the phantom is classified as a Dangerous Good. The new phantom is, therefore, ideal for uses that involve shipment, such as an intercomparison exercise. The phantom is also re-usable as the sources can be changed.