多排螺旋CT几何效率影响因素初步研究

目的：研究多排螺旋CT几何效率与准直宽度及管电压的关系。方法：使用长杆电离室测量不同准值宽度以及管电压下体模内剂量分布曲线并计算其几何效率。结果：多排螺旋CT的几何效率为11%～68%,其中中心位置的几何效率为11%～49%,边缘4个位置的几何效率为16%～68%,加权几何效率为17%～58%。随准直宽度的增加,几何效率明显增高,而管电压对几何效率的影响不明显。结论：多排螺旋CT几何效率受准直宽度影响较大,因此在实际临床操作中应选择适当的准直宽度进行扫描以减小患者的辐射剂量负担。     

多排螺旋CT胸部扫描人体剂量分布

目的：研究多排螺旋CT胸部扫描人体剂量分布。方法：采用临床常规扫描条件扫描模拟人体体模;采用热释光片测量体模所受辐射剂量和分布。结果：通过绘制二维／三维剂量分布图和剂量等高线图可以显示出人体不同的器官和组织所受辐射剂量的差异。结论：多排螺旋CT扫描所致受检者辐射剂量的分布研究可以为多排螺旋CT临床应用和风险评估提供较为客观和准确的技术依据。     

浅谈螺旋CT辐射剂量的测量

随着多排螺旋CT成像技术的不断发展,CT对患者的辐射风险越来越受到人们的关注.本文对当今螺旋CT辐射剂量的测量方法进行总结归纳,并对多排螺旋CT与轴向CT在剂量测量方法上存在的差异进行初步探讨.     

多排螺旋CT剂量效率的体模研究

目的：研究CTDI100表征CT检查所致辐射剂量的准确性。方法使用长杆电离室测量不同准值宽度、螺距以及管电压下体模内剂量分布曲线并计算CT剂量效率。结果 CT剂量效率范围为79%～94%,其中,中心位置的CT剂量效率范围为79%~87%,边缘4个位置的CT剂量效率范围为79%～94%,加权CT剂量效率范围为82%～90%。准直宽度与螺距越大,CT剂量效率越低;CT剂量效率受管电压影响不明显。结论CTDI100与CTDI∞之间存在一定差异,CTDI100、CTDIw表征CT检查所致辐射剂量的准确度随准直宽度和螺距的增大而降低。     

不同螺距多排螺旋CT扫描在胸部疾病筛查的应用研究

目的分析多排螺旋CT大螺距扫描在胸部筛查的辐射剂量。方法选择150例行多排螺旋CT胸部扫描的患者,随机分为三组,分别用螺距为0.562(A组)、0.938(B组)1.75(C组)行胸部平扫并记录CT容积剂量指数CTDIvol、剂量长度乘积DLP值、有效剂量ED,使用独立样本t检验比较3组扫描模式的辐射剂量间差异,另对扫描所得图像进行评估分析。结果①三组病例中,在肺尖和下肺,三组的图像噪声有统计学差异(P<0.05),A组SD值低于B、C组;在中肺,三组图像的SD值差异无统计学意义(P>0.05)。②在肺尖,三组图像的IQS评分的差异有统计学意义(P<0.05),A组的图像质量优于B、C组;在中、下肺及全肺,三组图像的IQS评分的差异无统计学意义(P均>0.05),即三组图像和全肺图像质量无明显差异;③三组病例的CTDIvol值、DLP值、ED值差异均有统计学意义(P<0.05),且A组的辐射剂量为B、C组的65.3%、47.9%。结论多排螺旋CT大螺距扫描能够显著降低辐射剂量,在满足临床诊断的前提下,为胸部筛查提供一种新的模式。     

螺距对多层螺旋CT下肢CTV图像质量和辐射剂量影响的研究

目的探讨多层螺旋CT的扫描参数螺距的改变对下肢CTV图像质量和辐射剂量的影响,为优化扫描方案提供理论依据。方法螺距分别为0.562:1,1.375:1。病人按使用不同的螺距分为A、B两组,病人都是随机分组,每组40人。机器自带软件客观评价图像噪声及信噪比,由两个放射科医生独立完成图像噪声和信噪比的主观评价。选用不同的螺距进行扫描同时记录设备自带的剂量记录数据CDTIvol。结果 light Speed 16层螺旋CT中,轴扫图像噪声为4.39±0.29,螺距为0.562、1.375时,A、B两组的图像噪声分别为3.24±0.25和5.27±0.25。螺距为0.562的A组MPR图像未见明显变形,B的图像比A组无较明显的变形。螺距为0.562时,扫描的辐射剂量远大于B组;螺距为1.375时,扫描的辐射剂量较小,图像信噪比客观上小于A组。结论下肢静脉CT检查中,在其他扫描参数不变的情况下,采用螺距优化扫描方案,1.375的扫描参数可作为常规选择,可以有效地降低辐射剂量,获得满意的、可以满足临床诊断需求的CT图像。     

数字冠脉造影与多排螺旋CT冠脉成像辐射剂量对比

随着多排螺旋CT技术的发展,CT冠脉成像在临床上的应用日益广泛。该成像技术与传统数字冠脉造影在辐射剂量方面的异同也愈加受到关注。本文主要介绍两种成像技术在辐射剂量测量方面的异同及其两种技术所致辐射剂量的差别。     

腰椎椎间盘多层螺旋CT低剂量扫描方式的改进

目的：探讨多层螺旋CT低剂量扫描在腰椎中的应用及其适宜的低剂量扫描条件。方法：选择60例30-65岁腰椎椎间盘退行性病变患者,随机分成A、B、C、D、E、F 6组,每组10例,采用不同的多层螺旋CT扫描参数进行扫描,并记录随机的容积CT剂量指数（volume CT dose index,CTDIvol）及剂量长度乘积（dose-length product,DLP）。采用自定标准盲式评估方法,对6组获得容积再现（volume rendering,VR）重组及Batch重组图像进行图像质量评分,由2位高年资主治医师依据空间分辨率、噪声、伪影及辐射剂量将图像分为好、中、差3级。结果：通过改变管电流（m A）、螺距及机架旋转速度,各组CTDIvol值、DLP值均存在明显统计学差异（P〈0.05）。相对于A组,B组CTDIvol值下降了14.29%,DLP值下降了12.64%;C组CTDIvol值下降了67.87%,DLP值下降了65%;D组CTDIvol值下降了62.49%,DLP值下降了58.45%;E组CTDIvol值下降了50%,DLP值下降了48%;F组CTDIvol值增加了24.86%,DLP值增加了29.7%。结论：正确调节管电流、螺距,可以在确保图像质量的同时,降低受检者所受辐射剂量。采用管电流350 m A、管电压120 k V、螺距1.375∶1,可降低58.45%的辐射剂量。     

影响螺旋CT辐射剂量的因素

目的 研究不同准直宽度、床速和螺距对CT辐射剂量的影响。方法 用热释光剂量计(TLDs)和标准剂量监测头模在Somatom plus 4.Siemens CT机上测量了准直宽度为5、8、10 mm,床速为5、8、10、12、15、16 mm/1.5 s,螺距为0.5、1、1.5、2扫描时,模体中心孔和离表面10 mm的边缘孔处的平均辐射剂量。结果 当管压和旋转速度一定时,剂量随管流、准直宽度的增加而增加;随床速、螺距的增加面减小。模体中心孔剂量与边缘孔的剂量基本相同,经统计检验无显著差异。结论 当管压、管流、旋转速度一定时,中心孔处的平均剂量与边缘孔处的平均剂量均与螺距成反比。准直宽度对辐射剂量的影响极小。     

河北省多排探测器CT辐射剂量调查研究

目的通过了解河北省多排探测器CT（MDCT）扫描患者辐射剂量现状,为做好患者剂量控制和管理工作提供科学依据。方法按照国家标准GB 17589-2011、GBZ 165-2005规定的方法,对该省MDCT患者头颅、胸部、腹部、腰椎等典型部位的辐射剂量进行调查研究。结果有12台设备头颅CD加权剂量指数（CTDIW）超过了50 mGy,占总数的13.3%。腹部的最大CTDIW超过了诊断参考水平近2倍。各部位CTDIW最大和最小值相差很大,腰椎相差近20倍。头颅的剂量长度乘积（DLP）最高达1 455 mGy/cm,是国际原子能机构（IAEA）研究数据的2.8倍,是欧洲MDCT诊断参考水平的4.3倍。64排及以上机型剂量指数整体比16排要低。在其他扫描条件不变时,CT容积剂量指数（CTDIVOL）随m As变化呈正比,随电压增加而增大,随准直宽度的增大而减小,随螺距的增大呈反比下降。结论应按辐射防护正当化和最优化的原则,加强MDCT患者辐射剂量控制及相关人员的技术培训和继续教育。     

Evaluation of coronary artery calcification by multi-detector row computed tomography for the detection of coronary artery stenosis in Japanese patients

BACKGROUND: The development of an efficient noninvasive examination to detect coronary atherosclerosis is needed as a strategy to prevent coronary heart disease. To evaluate the usefulness of calcium score measured by multi-detector row computed tomography (MDCT), we compared calcium score derived from MDCT with findings of coronary artery stenosis assessed by coronary angiography (CAG). METHODS: In 108 patients (94 men, 14 women; average age, 65.7 years), we performed unenhanced CT scans and calculated coronary artery calcium score in 259 vessels without previous intervention and severe motion artifact to determine the correlation with the degree of coronary stenosis by CAG. RESULTS: The sensitivity and the specificity of calcification (calcium score 0.1+) for severe stenosis (75+%) were 89% and 43%, respectively. All four vessels with calcium score 1000+ had a severe stenosis. The areas under the receiver operating characteristics curve of calcium score for severe stenosis were 0.80 +/- 0.04, indicating the efficacy of this technique. CONCLUSIONS: Coronary artery calcification and calcium score determined by MDCT were associated with coronary arteries with severe stenosis. This technique appears to be useful for the evaluation of coronary atherosclerosis.     

Pediatric dose reduction in computed tomography

An appropriate balance between risk (radiation dose) and benefit (based on image quality) for computed tomography (CT) in children is essential. This balance comes through an understanding of CT dose, why we do pediatric CT, and how we do pediatric CT. The following material, then, will approach radiation dose in the context of a larger safety program, and address the challenges with determining radiation dose in contemporary CT technology. Unique considerations with respect to study quality, those factors which influence CT use, and strategies for dose reduction (that is, optimization) will also be reviewed.     

Radiation dose in computed tomography: why it's a concern and what you can do about it

Computed tomography (CT) has become an invaluable and even life-saving diagnostic tool. But its great benefits come at a price: Because it uses ionizing radiation, CT can cause cancer. In fact, in the United States alone, it is estimated that CT accounts for around 6,000 additional cancers per year, with about half of those proving fatal. Unfortunately, this risk is not as widely recognized as it should be. In particular, both clinicians and patients tend to lack a clear understanding of the radiation doses involved in CT studies, which are higher than those used in other common x-ray studies. Given the swiftly growing use of CT, there's the real possibility that patients' exposure to radiation will grow as well. Thus, it's vital that clinicians understand the doses involved in CT, that those doses be kept as low as possible, and that CT be used only when the clinical benefits justify it. In this article, we explain the radiation risks of CT and discuss how they compare with other risks in and out of healthcare. We also discuss ways in which the doses delivered to patients can be kept to the necessary minimum. The approaches we cover include eliminating unnecessary CT use, raising referring physicians' awareness of the problem, considering alternative technologies, using good quality assurance, and optimizing imaging protocols.     

多排螺旋CT及后处理技术在复杂型髋臼骨折中的应用

目的:探讨多排螺旋CT(MDCT)及其后处理技术在复杂型髋臼骨折中的临床应用价值。方法:回顾性分析X线、MDCT证实的复杂型髋臼骨折患者36例影像资料。结果:MDCT及后处理技术能发现X光片不能发现的隐匿性骨折和脱位,它能整体、直观的显示骨折的部位、受累的范围、骨折线的走行方向、碎骨片及股骨头移位情况,虽然在敏感性上和X光片无显著差异(P0.05),但是在分型上明显优于X线片,能准确的进行骨折分型,差异具有统计学意义(P0.05)。结论:MDCT及后处理技术对术前充分了解损伤情况、骨折的分型,对临床手术计划的制定具有重要的意义,成为复杂髋臼骨折术前诊断的首选检查方法。     

A survey of patient dose and image quality for computed tomography scanners in Wales.

The main aim of the study was to assess the current level of radiation dose from computed tomography scanning in the NHS in Wales and to compare these results with previous studies in Wales and the UK. In addition, the relationship between patient dose and image quality was investigated by comparing mean patient dose calculations with image noise using two quality assurance (QA) phantoms. The results show that although the introduction of spiral scanners has reduced the dose per examination, the collective dose per scanner has actually increased. The results also highlight the potential for relating dose and objective measures of image quality to assist in the selection of scanning parameters to optimise dose without compromising image quality.     

Results from a phantom based multi-centre paediatric computed tomography dose survey

A computed tomography radiation dose survey was performed within our enterprise using three age-based paediatric phantoms representing a 1, 5 and 10 years old. Twenty-seven scanners were surveyed with volume computed tomography dose index and dose length product data collected for head, chest and abdomen-pelvis protocols at each age. Reconstruction method e.g. filtered back projection (FBP) or iterative (IR) was also recorded. About two-thirds of the 1 year old FBP chest scans exceeded the national Baby diagnostic reference level (DRL). A small number of scanners also exceeded the national Child DRL for the 1 and 5 years old phantoms. Only about half of the phantom protocols showed a difference of statistical significance between FBP and IR scanners. The results suggested the need for optimisation work at a number of sites. It was determined that the proposed local (i.e. enterprise-wide) DRLs are presented best in terms of weight or girth rather than age.     

Monte Carlo estimation of absorbed dose to organs in computed tomography.

This paper proposes a method to estimate absorbed doses to organs in explorations using computed tomography. This Monte Carlo-based method is a generalization of a previous method applied to conventional diagnostic radiology and is also applicable to radiotherapy techniques using photons or electrons. This study is applied to the estimation of absorbed doses to different parts of the head in a simple head CT examination. Simulation was performed for different arrangements (monoenergetic beam, spectrum, different number of histories, etc.). Comparison of the results with experimental doses measured in a human phantom by thermoluminescent dosimeters indicates that the method is capable of adequately estimating doses to organs in computed tomography.