便携式NaI (Tl)γ谱仪对甲状腺内131 I的探测效率模拟计算

目的 计算不同甲状腺-颈部刻度模体和测量位置对便携式γ谱仪的全能峰探测效率影响,为更加准确开展人体甲状腺内¹³¹I活度现场测量提供指导。方法 在对4种典型的甲状腺-颈部模体和用于甲状腺内¹³¹I活度测量的便携式3英寸NaI （TI）γ谱仪进行建模的基础上,结合可能的现场测量情景,利用蒙特卡罗方法模拟计算便携式NaI （TI）γ谱仪在不同测量距离、不同甲状腺深度、不同甲状腺体积等条件下的全能峰（364.5 keV）探测效率。结果 NaI （TI）γ谱仪的探测效率随探测器与颈部表面距离增加而显著递减,紧贴颈部表面的探测效率约为距颈部表面15 cm的15倍;探测效率随甲状腺深度增加而明显降低,在颈部表面测量时,深度为2 mm的探测效率约为30 mm的3.6倍;探测效率随甲状腺体积增大而减小,在颈部表面测量时,体积为1 ml的探测效率是30 ml的1.71倍;探测效率随探测器中心偏移而降低,尤其是在颈部表面测量时,中心偏离2 cm会导致探测效率下降约15%。结论 利用便携式NaI （TI）γ谱仪开展人体甲状腺内¹³¹I活度准确测量,不仅需要掌握探测效率刻度时的测量距离,还需了解所用刻度模体内的甲状腺深度与体积。     

3种常见介入诊疗中放射工作人员有效剂量的估算

目的 选取介入放射学中较常见的脑血管、心血管和肝脏介入诊疗,估算以上3种介入诊疗中放射工作人员的有效剂量.方法 通过仿真人体模型实验,了解脑血管、心血管、肝脏介入诊疗中仿真体模内组织、器官的吸收剂量,并根据ICRP 103号出版物中规定的组织权重因子估算3种介入诊疗中放射工作人员的有效剂量.结果 脑血管介入诊疗时,介入放射工作人员的有效剂量分别为高剂量组24.0μSv、中剂量组9.7μSv、低剂量组6.8 μSv;心血管介入诊疗时,放射工作人员的有效剂量分别为高剂量组36.3 μSv、中剂量组29.3 μSv、低剂量组17.8μSv;肝脏介入诊疗时,放射工作人员的有效剂量分别为高剂量组23.9 μSv、中剂量组11.3μSv、低剂量组5.5μSv.结论 心血管介入诊疗中放射工作人员高、中、低3个剂量组的有效剂量分别高于脑血管和肝脏介入诊疗时相应剂量组的有效剂量.

Abstract：

Objective To study and estimate the effective dose of interventional employees in the common cerebralvascular, cardiovascular and liver interventional diagnosis and treatment.Methods The absorbed doses of tissue or organ of anthropomorphic phantom in these three procedures were estimated by the anthropomorphic phantom experiment.The effective doses were calculated by the tissue weight factor which was given by International Commission on Radiological Protection publication 103.Results The effective doses to high, medium and low group were 24.0, 9.7,6.8 μSv for cerebralvascular interventional diagnosis and treatment, and 36.3, 29.3, 17.8 μSv for cardiovascular interventional diagnosis and treatment, and 23.9, 11.3, 5.5 μ Sv for liver interventional diagnosis and treatment, respectively.Conclusions The effective doses of high, medium and low group of interventional employees in cardiovascular interventional procedure are higher than those of cerebralvascular and liver interventional procedures.     

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。     

乳腺摄影剂量与低对比模体影像质量分析

目的以物理形式测量,分析乳腺自动摄影模式的剂量参数的设置与低对比度影像质量[1]和受检者的乳腺平均腺体剂量[2]的关联性。方法先使用3种自动摄影模式（CNT对比模式、STD标准模式、Dose剂量模式）分别对18-220和18-222模体照射,再使用3种自动摄影模式分别对加3块和4块亚克力板（1cm）的低对比性能模体（CDMAM）照射;按CDMAM测试要求分别选取3种自动摄影模式下剂量设置的下限和上限进行照射,获取低对比性能模体影像分析数据。结果选择3块亚克力板配合CDMAM进行采样与18-220模体剂量参数基本一致;采用3块亚克力板配合CDMAM自动摄影,CNT模式较STD模式的平均腺体剂量（AGD）增加1倍,IQFinv增加5%~7%;STD模式较Dose模式的AGD增加15%,IQFinv增加8%~13%。结论①辐射剂量的过度上升并不会带来相对应的低对比性能效果;②CNT模式和Dose模式不适宜用作常规检查,只有特定情况下才可使用;③先参考临床其它检查数据,再确定摄影模式,是在保障影像质量的前提下,减少受检者辐射剂量的有效方案之一。     

Feasibility of a method for low contrast CT image quality assessment using difference detail curves for abdominal scans

This work describes a measurement method for assessing dose-related image-quality of CT scans based on the difference detail curve (DDC) method, and showcases its use in a low contrast setting. The method is based on a phantom consisting of elliptical slices of different sizes into which contrast object modules can be inserted. These modules contain contrast objects based on (synthetic) resin mixtures with sucrose (native) or sodium iodine (contrast medium). Mixing ratios are provided to achieve a range of clinically relevant CT-numbers with these materials. The phantom is characterized in terms of contrast accuracy, energy dependency and long-term drift with satisfying results. Contrast accuracy and energy dependency are similar to that of water or soft tissue. Image quality of 655 scans of the phantom acquired at 30 different clinical institutions and with 16 different CT scanner models from 4 manufacturers was assessed by calculating a difference detail curve (DDC) from evaluation of up to 5 human observers using a custom-made software (RadiVates) described in this work. Based on these measurements, inter-observer variability was quantified using a bootstrap method and was shown to be a large contributor to the overall variability. This work demonstrates that assessment of CT image quality is feasible with the aforementioned phantom and DDC method.     

Attenuation Coefficient Estimation of Normal Placentas

Attenuation coefficient estimation has the potential to be a useful tool for placental tissue characterization. A current challenge is the presence of inhomogeneities in biological tissue that result in a large variance in the attenuation coefficient estimate (ACE), restricting its clinical utility. In this work, we propose a new Attenuation Estimation Region Of Interest (AEROI) selection method for computing the ACE based on the (i) envelope signal-to-noise ratio deviation and (ii) coefficient of variation of the transmit pulse bandwidth. The method was first validated on a tissue-mimicking phantom, for which an 18%–21% reduction in the standard deviation of ACE and a 14%–24% reduction in the ACE error, expressed as a percentage of reported ACE, were obtained. A study on 59 post-delivery clinically normal placentas was then performed. The proposed AEROI selection method reduced the intra-subject standard deviation of ACE from 0.72 to 0.39 dB/cm/MHz. The measured ACE of 59 placentas was 0.77 ± 0.37 dB/cm/MHz, which establishes a baseline for future studies on placental tissue characterization.     

Design,performance characteristics and application examples of a new 4D motion platform

In this publication, a three-dimensionally movable motion phantom is described and its performance characteristics are evaluated. The intended primary fields of application for the phantom are the quality assurance (QA) of respiratory motion management devices in radiation therapy (RT) like gating or tumour tracking systems, training for clinical use of these techniques, and related 4DRT research. Considering especially the QA aspect, the phantom was designed as a motion platform that can be equipped with an appropriate add-on like standard QA phantoms for dosimetric measurements. The platform is driven by three computer-controlled independent linear motors (motion range: 40 × 50 × 50 mm in anterior-posterior/superior-inferior/lateral direction; max. velocity: 3.9 m/s; max. acceleration: 10 m/s²), which allow the simulation of normal breathing patterns as well as arbitrary trajectories and anomalous events like coughing or baseline drift. For normal breathing patterns (here: sinusoidal curves with an amplitude of 20 mm and a period of 3 s/6 s), the accuracy of the simulated motion paths was measured to be within 0,521 mm even for the ArcCHECK^® (weight: 20 kg) as a platform load – values that we consider to be sufficient for the intended fields of application. The respective use of the motion phantom is illustrated.