用Sievert法结合实验测量计算60Co射线的体模散射修正系数

目的：用Sievert剂量计算公式结合实验测量的数据计算60Co产生的射线在等效体模中的散射修正系数。方法：采用四川成都体模和TLD法测量体模的吸收剂量，并用MATLAB应用程序来拟合修正系数，结果：给出了等效体模的散射修正系数，并计算了两种模拟事故情况下的重要器官的剂量，和它们与TLD法测出的剂量值间相对偏差。结论：在两种事故情况下，用理论公式计算的剂量与测量值相关不大，说明拟合出的系数在一定的范围内是适用的。     

TLD质量核查调强放射治疗非均匀野剂量方法

目的核查放射治疗计划系统(TPS)计算病人治疗剂量的非均匀野剂量校正。方法将插有TLD的聚苯乙烯固体模体,聚苯乙烯/肺固体模体,聚苯乙烯/骨固体模体分别经CT扫描,影像分别传入TPS并计算高能X射线下监督单位数,使传递给中心束轴TLD剂量为2 Gy。在高能X射线下完成TLD照射,照射后的TLD经测量、剂量计算,D(TLD)与D(TPS)剂量比值在0.95~1.05范围为可接受范围。结果核查结果表明,光子线束均匀模体轴上(P)剂量和非均匀骨模体轴上(BP)剂量核查结果较好。非均匀肺模体轴上(LP)和离轴(LL)剂量核查结果误差很大。结论光子线束非均匀性剂量校正在放射治疗中是非常重要,尤其是肺组织。校正不当,对于肺组织剂量误差也可达到11.1%,离轴情况下更多达18.4%。对于骨组织剂量误差较小。     

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。     

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。     

自制肺部模体用于射波刀肺追踪E2E验证分析

目的 通过比较自制肺部模体与CIRS动态模体在射波刀肺追踪E2E测试中的测量结果,验证自制肺部模体用于射波刀质量控制检测的可行性。方法 模拟患者治疗流程,分别对自制肺部模体与CIRS模体进行CT定位、计划设计、实施照射、扫描胶片并进行分析,上述两种模体在S7代射波刀上使用MLC各重复测量5次,在M6代射波刀上使用Iris也分别重复测量5次,对实验结果使用独立样本t检验分析方法分析两种模体测量结果的差异。结果 对于S7代射波刀,两种模体在X轴、Y轴、Z轴和总偏差上的检测值统计学分析结果分别为：P=0.236、0.175、0.289、0.668;对于M6代射波刀,所得分析结果分别为：P=0.880、0.891、0.573、0.433。以上P值均> 0.05。因此自制肺部模体与CIRS模体在S7代射波刀与M6代射波刀上的检测结果差异均无统计学意义;总偏差值均<1.5 mm。结论 自制肺部模体与CIRS模体在射波刀肺追踪的E2E实验中,测量结果具有一致性,满足AAPM TG-135报告和WS 667—2019标准中的要求,具有用于射波刀临床质控的可行性。     

一种磁共振成像装置质量控制测试体模的研制

目的：设计一种功能全面、结构简单及测量精度高的磁共振成像（MRI）质量控制测试体模。方法：通过对MRI原理以及影响MRI图像质量的技术参数进行深入研究,提出体模应具备的性能指标,确定材料、加工工艺、加工精度等技术方案,采用数字控制机械加工的方式试制出MRI测试体模1套;将其与同类进口体模进行比对实验,分析其测试结果是否具有一致性。结果：自制体模的各项技术参数的测试结果与同类进口体模的测试结果一致性较好,测试组件更全面,低对比度分辨力等技术指标优于进口体模。结论：设计研制的测试体模能够满足医院MRI日常质量控制工作的需要。     

医用超声成像系统调制传递函数的探讨

本文采用两种方法，利用超声多组织体模计算超声成像系统的调制传递函数(MTF)。首先，根据超声成像及体模内部结构的特点，将体模内的分辨目标群视作条形输入，提出对比度法求得系统的MTF；其次，利用体模内相同深度处的目标群构造系统的线扩散函数，经过傅里叶变换得到系统的MTF，并对两种方法取得的结果进行了分析。     

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。     

不同磁共振层厚测试体模与测试方法的比较研究

目的：研究不同层厚测试体模和不同层厚测试方法对磁共振（MR）层厚测量结果的影响。方法：依据国际标准和国家标准研制4种不同的MR层厚测试体模，采用2种不同的测试方法分析其测量结果；将测量结果与进口体模进行比较分析。结果：通过Matlab程序分析得到测量结果，确定了MR层厚测试的影响因素，与理论分析结果基本一致。结论：4种层厚测试体模均满足MR层厚测试要求，使用斜板的测量方法更加简单易行，测量结果与进口体模更接近；通过倾斜校正方法可显著提高MR层厚测量精度。     

AAPM与CATPHAN500CT体模的比对测试

目的 了解AAPM与CATPHAN500 CT体模在医用CT检测中各项性能指标的存在差异,了解两种体模检测结果的可比性,力求对CT评价的公证与统一。方法 用相同型号的CT分别对两种体模进行扫描,分别对扫描图像进行测试,进行结果的比较。结果 两体模外观结构和介质不同,指标的检测结果存在差异,但差异不大,完全在可接受范围之内。结论 两体模的检测结果虽然存在差异,但都符合自身的设计要求,结果相近,具有可比性。     

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%.     

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 BRMD BOMAB phantom family

The Human Monitoring Laboratory (HML) has used the International Commission on Radiological Protection's Report on Reference Man and Canadian anthropomorphic data as guidance to design and construct a family of phantoms corresponding to Reference Man (PM), Reference Woman (PF), Reference Ten-Year-Old (P10), Reference Four-Year-Old (P4), Ninety-five Percentile Man (PM95), and Five Percentile Man (PM5). The PM series also has an accessory chest section (PMacc) to better simulate lung depositions. The phantoms are constructed from high-density polyethylene and fitted with end-recessed filling caps to minimize leakage problems. This paper describes the methodology of construction and presents data so that the phantoms can be reproduced. The phantoms have been used in Canada's National in-vivo Intercomparison Program, and results show that all Canadian in-vivo counting facilities have size-dependent calibrations. Selected data are presented to exemplify this dependence.     

BOMAB phantom variability: do small dimensional changes matter?

The Human Monitoring Laboratory (HML) has had a number of BOMAB phantoms built over the years. Upon characterization, it has been found that the dimensions of the phantoms are always slightly different. This study has looked at the effect of these small variances in dimensions of the phantoms and compared the results to what is required in the industry standard using Monte Carlo simulations for three counting geometries: the HML's scanning detector whole body counter, the StandFast whole body counter, and the W-chair whole body counter. It has been found that the effect of these small variations on the performance of these phantoms is very minor (<5%). It is reassuring to find that small variations in manufacturing, even if individual sections are non-compliant, have such a minor effect on performance as to be considered a negligible effect for any counting system's geometry.     

Hybrid computational phantoms representing the reference adult male and adult female: construction and applications for retrospective dosimetry

Currently, two classes of computational phantoms have been developed for dosimetry calculation: (1) stylized (or mathematical) and (2) voxel (or tomographic) phantoms describing human anatomy through mathematical surface equations and 3D voxel matrices, respectively. Mathematical surface equations in stylized phantoms are flexible, but the resulting anatomy is not as realistic. Voxel phantoms display far better anatomical realism, but they are limited in terms of their ability to alter organ shape, position, and depth, as well as body posture. A new class of computational phantoms called hybrid phantoms takes advantage of the best features of stylized and voxel phantoms-flexibility and anatomical realism, respectively. In the current study, hybrid computational phantoms representing the adult male and female reference anatomy and anthropometry are presented. These phantoms serve as the starting framework for creating patient or worker sculpted whole-body phantoms for retrospective dose reconstruction. Contours of major organs and tissues were converted or segmented from computed tomography images of a 36-y-old Korean volunteer and a 25-y-old U.S. female patient, respectively, with supplemental high-resolution CT images of the cranium. Polygon mesh models for the major organs and tissues were reconstructed and imported into Rhinoceros? for non-uniform rational B-spline (NURBS) surface modeling. The resulting NURBS/polygon mesh models representing body contour and internal anatomy were matched to anthropometric data and reference organ mass data provided by Centers for Disease Control and Prevention and International Commission on Radiation Protection, respectively. Finally, two hybrid adult male and female phantoms were completed where a total of eight anthropometric data categories were matched to standard values within 4% and organ volumes matched to ICRP data within 1% with the exception of total skin. The hybrid phantoms were voxelized from the NURBS phantoms at resolutions of 0.158 × 0.158 × 0.158 cm and 0.126 × 0.126 × 0.126 cm for the male and female, respectively. To highlight the flexibility of the hybrid phantoms, graphical displays are given of (1) underweight and overweight adult male phantoms, (2) a sitting position for the adult female phantom, and (3) extraction and higher-resolution voxelization of the small intestine for localized dosimetry of mucosal and stem cell layers. These phantoms are used to model radioactively contaminated individuals and to then assess time-dependent detector count rate thresholds corresponding to 50, 250, and 500 mSv effective dose, as might be needed during in-field radiological triage by first responders or first receivers.     

Application of Gafchromic film in the study of dosimetry methods in CT phantoms

Gafchromic film has been used for measurement of computed tomography (CT) dose distributions within phantoms. The film was calibrated in the beam from a superficial therapy unit and the accuracy confirmed by comparison with measurements with a 20 mm long ionisation chamber. The results have been used to investigate approaches to CT dosimetry. Dose profiles were recorded within standard CT head and body phantoms and scatter tail data fitted to exponential functions and extrapolated to predict dose levels in longer phantoms. The data have been used to simulate both CT dose index (CTDI) measurements with ionisation chambers of differing length and measurements of cumulative doses with a 20 mm chamber for scans of varying length. The results show that the length of a pencil ionisation chamber is the most significant factor affecting measurements of weighted CTDI (CTDI(w)) and a 100 mm chamber would record 50-61% of the dose measured with a 450 mm one. The cumulative dose measured at the centre of a 150 mm long body phantom records over 70% of the equilibrium dose from a helical scan of a longer phantom. For routine CT dosimetry tests, the determination of correction factors could allow measurements with a 100 mm chamber to be used to derive the CTDI that would be recorded with a longer chamber, and cumulative doses measured with a 20 mm chamber in shorter phantoms to be used to calculate equilibrium doses for helical scans.     

Dose estimations for Iranian 11-year-old pediatric phantoms undergoing computed tomography examinations

In order to establish an organ and effective dose database for Iranian children undergoing computed tomography (CT) examinations, in the first step, two Iranian 11-year-old phantoms were constructed from image series obtained from CT and magnetic resonance imaging (MRI). Organ and effective doses for these phantoms were calculated for head, chest, abdomen–pelvis and chest–abdomen–pelvis (CAP) scans at tube voltages of 80, 100 and 120 kVp, and then they were compared with those of the University of Florida (UF) 11-year-old male phantom. Depth distributions of the organs and the mass of the surrounding tissues located in the beam path, which shield the internal organs, were determined for all phantoms. From the results, it was determined that the main organs of the UF phantom receive smaller doses than the two Iranian phantoms, except for the urinary bladder of the Iranian girl phantom. In addition, the relationship between the anatomical differences and the size of the dose delivered was also investigated and the discrepancies between the results were examined and justified.     

Determination of photon conversion factors relating exposure and dose for several extremity phantom designs

Dosimetric measurements were performed to determine the exposure-to-dose conversion factors (Cx) for simple extremity phantoms suitable for extremity dosimeter performance testing. The phantoms studied represented the forearm or lower leg and the finger. Measurements were performed for solid plastic phantoms and for phantoms containing simulated bone material to determine the effect of backscattered radiations from the simulated bone to the phantom surface. Photon beam energies used for the measurements ranged from 16 keV to 1.25 MeV (average). The Cx factors for the finger phantoms did not vary significantly with phantom composition. The Cx factors in the arm/leg phantoms with the bone simulant material differed significantly from those for the solid plastic phantom over the energy range of 40-100 keV. This effect was attributed to the preferential absorption of the lower energy backscattered photons by the higher atomic number material that was contained in the bone-simulant insert. The position of the bone-simulating material below the surface of the phantom was more important than its size or level of bone equivalency. For calibrations and dosimeter testing, Al was found adequate as a bone-simulating material.     

不同CT性能模体低对比分辨力检测结果探讨

目的：寻找两种低对比度分辨力模体在同一台CT装置上以相同扫描条件测试产生低对比度分辨力误差的原因。方法：按国家标准中规定的低对比分辨力检测和评价方法,以常用的两种性能模体进行比对测试。结果：所测低对比度分辨力结果相差1.62～2.01。结论：低对比度分辨力测试应选择Catphan500性能测试模体组件为宜。