婴儿头颅CT中铋屏蔽对辐射剂量和影像质量的影响

目的 研究婴儿头颅CT检查中使用铋屏蔽材料降低眼晶状体受照剂量的效果及对图像质量的影响。方法 使用适合患儿使用的自制铋屏蔽防护眼罩、婴儿体模,采用热释光探测器测量受照剂量。CT扫描条件选择120 kV、130 mA轴位扫描,分别进行铋屏蔽和无屏蔽两组模体测试,比较模体内相当于晶状体位置的受照剂量;应用同样CT扫描参数,对临床疑为颅内出血的99例患儿佩戴铋屏蔽眼罩后进行头部扫描,由2名高年资医生分别进行图像质量评估,并比较评分的一致性。结果 体模实验显示,无屏蔽时眼罩后方区域吸收剂量为25 mGy,经铋防护眼罩屏蔽后眼罩后方的吸收剂量为17 mGy,降低辐射剂量32%。佩戴铋屏蔽眼罩对患儿头部CT图像质量无明显影响。结论 在婴儿头颅CT扫描中使用铋屏蔽防护眼罩,可明显降低眼晶状体放射吸收剂量,同时对CT图像质量的影响是可接受的。     

双源CT扫描模式对头颈部辐射剂量和影像质量的影响

目的 探讨头颈部CT扫描中,不同扫描模式对辐射剂量和影像质量的影响程度。方法 利用头颈部仿真模体和双源CT,分别使用固定扫描条件120 kV和200 mAs,以及自动管电流调制技术（CARE Dose 4D）、自动管电压调制技术（CARE kV）和部分角度扫描模式（X-CARE）的组合进行成像,分别为120 kV+200 mAs、120 kV+200 mAs+X-CARE、CARE Dose 4D+120 kV、CARE Dose 4D+120 kV+X-CARE、CARE Dose 4D+CARE kV、CARE Dose 4D+CARE kV+X-CARE 6种扫描模式。每次扫描均使用两片热释光剂量片（TLD）分别测量眼晶状体和甲状腺的剂量,两片TLD所测数值取均值。记录以上各种扫描时的容积CT剂量指数（CTDI_vol）和剂量长度乘积（DLP）,测量眼晶状体层面和甲状腺层面影像的对比度噪声比（CNR）。结果 120 kV+200 mAs扫描时,眼晶状体和甲状腺的器官剂量分别为19.8和26.0 mGy,使用120 kV+200 mAs+X-CARE可降低剂量至13.3和22.2 mGy;与CARE Dose 4D+120 kV相比,CARE Dose 4D+CARE kV可使CTDI_vol由13.1降至10.1 mGy,眼晶状体剂量和甲状腺剂量由20.8和23.7 mGy分别降至16.6和19.9 mGy,而使用CARE Dose 4D+CARE kV+X-CARE时,器官剂量又进一步分别降至6.3和11.0 mGy,但影像质量显著降低;与CARE Dose 4D+120 kV相比,使用CARE Dose 4D+120 kV+X-CARE,眼晶状体和甲状腺剂量分别由20.8和23.7 mGy降至9.6和15.1 mGy,同时CTDI_vol由13.1 mGy降至9.3 mGy。使用CARE Dose 4D+CARE kV+X-CARE时,CTDI_vol和器官剂量降至最低,但头颅和颈部CNR也降至最低。结论 颅脑扫描时CARE Dose 4D+120 kV+X-CARE模式、颈部扫描时CARE Dose 4D+CARE kV模式在保持影像质量较好的同时可有效降低辐射剂量。当对影像质量要求不高时可选用CARE Dose 4D+CARE kV+X-CARE模式,从而显著降低辐射剂量。     

头颈部多层螺旋CT辐射剂量调查

目的 了解我国头颈部多层螺旋CT扫描剂量.资料与方法 发出头颈部CT扫描参数剂量调查表到国内7家东芝64层螺旋CT用户.查阅2002年1月至2007年7月期间中华放射学杂志、临床放射学杂志和实用放射学杂志三大杂志有关头颈部多层螺旋CT论文并测算其剂量.结果 东芝64层螺旋CT扫描:头部平均毫安秒为189.4 mAs、CT剂量指数(CTDIvol)为47 mGy;鼻窦95 mAs、22.5 mGy,眼眶为74.3 mAs、17.9 mGy,颌面部为100 mAs、22.5 mGy,颞骨144.6 mAs、44.7 mGy,颈部131.3 mAs、16.3 mGy.其他螺旋CT为头部平均毫安秒为280 mAs;鼻窦为100 mAs,眼眶200 mAs,颌面部为200 mAs,颞骨196.7 mAs,颈部220 mAs.结论 我国头颈部多层螺旋CT检查条件剂量不规范、不统一,有待优化.     

螺旋CT机辐射剂量的评价

自 1 98 9年引入螺旋ＣＴ技术后 ,极大地缩短了ＣＴ的扫描时间 ,如不严格使用将给病人带来较高辐射危害。笔者在给出头部和体部体模扫描条件下 ,对 8台螺旋ＣＴ机的剂量学和可能导致病人的有效剂量进行了估算。一、材料和方法8台螺旋ＣＴ机均为进口机器 ,分布在北京、广州、哈尔滨、石家庄等 4个城市的 8家医院中。测量所使用的仪器分别为 :美国Ｖｉｃｔｏｒｅｅｎ公司 660 1型静电计和 660 6笔型电离室 (长 1 0 0ｍｍ) ;瑞典ＲＴＩ公司Ｓｏｌｉｄｏｓｅ 40 0型剂量计和ＷＤＣＴ1 0ＬＥＭＯ笔型电离室 (长 1 0 0ｍｍ)。电离室分别放在 1个…     

应警惕介入手术操作时眼晶状体所受的辐射剂量

目的评估放射介入从业人员眼晶状体在使用放射防护和未使用放射防护状态下所接受的辐射剂量。材料和方法采用模拟模具测量7种放射介入透视系统的散射辐射     

多层螺旋CT在胸部扫描中减少辐射剂量的技术探讨

目的:探讨多层螺旋CT在胸部扫描过程中调整了扫描的参数减少患者的辐射剂量.材料和方法:将120例胸部多层面CT检查患者随机分为对照组及实验组2组,对照组63例,实验组57例.CT扫描采用GE lightspeedQX/I多层螺旋CT机,对照组扫描参数为管球电压120kV,电流300mA;实验组扫描参数为管球电压120kV,电流30～50mA,并分别测量两组患者所接受的辐射剂量.结果:实验组与对照组CT图像质量无显著差异,均达到诊断要求.对照组与实验组CT剂量加权指数(CTDI)平均值分别为9.8 mGy,1.1 mGy,实验组辐射剂量低于对照组(P＜0.05).结论:采用低剂量扫描技术可减少对患者的照射剂量,且能达到诊断要求.     

基于256层螺旋CT头颈部扫描的最优辐射剂量节省模式的实验研究

目的探讨在保证影像质量前提下的头颈部256层CT最优低剂量节省模式。方法应用组织等效头颈部模型置于Philips Brilliance256层CT机以标准模式(400mAs)和低剂量节省模式进行分别扫描,其中低剂量节省模式包括自动管电流选择(ACS)、螺旋剂量节省(Helical Dose Saving)、X-Y平面动态电流调节(D-DOM)、Z轴动态电流调节技术(Z-DOM)等进行组合,测量、记录模型蝶鞍、下颌骨和胸骨柄各部位CT值、CT值噪声标准差(SD),分别行方差分析。结果共有8种组合模式可降低辐射剂量。即:①ACS;②ACS+Helical;③ACS+(D-DOM);④ACS+(Z-DOM);⑤ACS+Helical+(D-DOM);⑥ACS+(D-DOM)+(Z-DOM);⑦ACS+Helical+(Z-DOM);⑧ACS+Helical+(D-DOM)+(Z-DOM)。与标准剂量CTDI26.5mGy,DLP1276.8mGy*cm相比,CT不同剂量节省方式扫描时,在保证图像质量的同时,辐射剂量可节省11.21%～68.12%。采用最优剂量节省模式ACS+Helical+(D-DOM)+(Z-DOM),CTDI从26mGy降低到11.8mGy,DLP从1134.6mGy*cm降低到504.9mGy*cm。蝶鞍、下颌骨和胸骨柄水平相同部位软组织和骨骼的CT值在各组间差异均无统计学意义(P≥0.05)。蝶鞍、下颌骨水平骨骼结构测量的SD值有统计学差别(P<0.01),而胸骨柄水平骨骼SD值和蝶鞍、下颌骨、胸骨柄水平相同部位软组织SD值间差异均无统计学意义(P>0.05)。结论在头颈部螺旋CT扫描中,恰当运用螺旋CT剂量节省模式,辐射剂量可大大降低。     

降低螺旋CT辐射剂量策略

使用CT诊断一个临床指征其益处远多于潜在风险,但CT曝光辐射的潜在风险仍是近年来人们关注的焦点。因此有必要提醒放射医生在保证影像诊断质量的同时必须将辐射剂量降低到尽可能低水平（ALARA）。为达到ALARA标准,必须合理使用CT,并根据具体的诊断任务而进行调整。就CT辐射输出测量的概况、辐射剂量的合理使用和优化以及降低辐射剂量的策略予以综述。     

降低儿童16层螺旋CT检查辐射剂量的研究

目的论证CT扫描参数kVp和mAs与剂量和图像噪声的关系,在不影响临床诊断的基础上,修正并验证一种基于成人扫描参数的安全可行的儿童16层螺旋CT检查的扫描参数。方法利用16层螺旋CT,采用标准CT剂量指数(CTDI)测试仪、100mm笔型电离室,分别测量16cm和32cm直径模体在2mm×5mm准直宽度时不同kVp和mAs的CTDI;采用20cm标准水模,测量单一感兴趣区域(ROI)标准偏差值SD代表噪声水平。以成人扫描参数的不同百分比修正为不同年龄段儿童CT扫描的参数供临床验证。结果随着kVp和mAs的增加,CTDI随之增加,并与mAs呈线性关系;16cm直径模体的表面CTDI要高于32cm模体58%;实际的加权CTDIw值高于CT扫描仪显示的CTDIw;mAs相同时,kVp越高,图像噪声SD值越低,在kVp固定时,随着mAs的增加,图像噪声SD随之减少,当mAs增加到一定程度后,图像噪声趋向平稳。结论在不影响临床诊断的图像噪声水平下,根据年龄和体型特点,儿童16层CT检查mAs可以比成人降低10%～85%。     

多层CT螺距与辐射剂量的关系探讨

目的 探讨多层螺旋CT的扫描参数螺距的变化对辐射剂量的影响.方法 对于LightSpeed 16层螺旋CT和Sensation 16层和64层螺旋CT,将长杆电离室分别置于16 mm剂量体模的5个孔中,选用不同的螺距进行扫描并测量辐射剂量.结果 3种机型轴扫和螺旋扫描的CTDIvol分别为：（1）对于lightSpeed 16层螺旋CT,在轴扫及螺距分别为0.562、0.938,1.75时,分别等于28.9、51.4、30.8,16.5;（2）对于Sensation16层螺旋CT,在轴扫及螺距分别为0.5,1、1.5时,分别等于41.2、40.3、41.5,43.2;（3）对于Sensation64层螺旋CT,在轴扫及螺距分别为0.5,1.1.5时,分别等于41.2、40.3、41.5,43.2.结论 对于LightSpeed 16层螺旋CT,随着螺距的增加,辐射剂量降低,为保持恒定的图像质量,必须增大mAs作为补偿;Sensation 16层和64层螺旋CT,因采用了mAs自动调整技术,在不同的螺距下辐射剂量相同,图像质量稳定.日常操作中当螺距改变时,应根据不同机型来确定调整管电流的方法.     

Radiation dose to the lens in sequential and spiral CT of the facial bones and sinuses

A tendency for over-utilization of the radiological examinations of facial bones and sinuses has been observed. The radiosensitive lens is exposed to radiation during such examination. Comparison of routine roentgenography and spiral axial and coronal CT in sequential and spiral acquisition modes with different mAs values was undertaken using Alderson Rando Phantom. The spiral-CT technique with pitch 1.5 performed in the coronal plane gave the lowest radiation dose to the lens as compared with other CT methods and only seven times higher than routine sinus roentgenography. Received: 27 March 2000 Revised: 13 July 2000 Accepted: 13 July 2000     

铋屏蔽联合器官管电流调制技术在颅脑CT检查中应用的体模研究

目的:通过测量敏感器官的辐射剂量,评价铋屏蔽联合器官-管电流调制(X-care)技术在颅脑CT扫描中的应用价值。方法:使用德国德国西门子公司炫速双源CT对头颈体模进行相同容积CT剂量指数(CTDI vol)下的X-care、铋屏蔽和X-care联合铋屏蔽3种方式扫描颅脑,及无铋屏蔽和铋屏蔽2种方式扫描双能量...     

Efficacy of breast shielding during CT of the head

In light of increasing frequency of CT examinations in the past decades, the aims of this prospective study were to investigate scatter radiation breast exposure in head CT and its dependence upon body constitution, and to assess the efficacy of lead shielding as a means of breast dose reduction. In 49 women referred to head CT for objective medical reasons one breast was covered with lead apron during CT scanning. Radiation doses were measured by use of thermoluminescent dosimeters, at skin of both breasts and over the apron. The doses were then compared as well as correlated to body mass index and meatus acusticus externus-to-dosimeter distance, respectively. Average exposure at the skin of the unshielded breast was 0.28 mGy (range 0.15–0.41 mGy), compared with 0.13 mGy (range 0.05–0.29 mGy) at the shielded breast. The doses showed a mean reduction by 57% due to lead shielding. At least half of breast exposure was imparted to the breast from outside, whereas the remainder results from internal scatter. The higher the body mass index, the higher the percentage of internal scatter in total breast dose. Although the level of scatter radiation to the breast is generally low during head CT examination, the use of lead cover enables recognizable further reduction of the exposure, and is recommended as a feasible and effective procedure of breast protection during CT of the head.     

Would thyroid and breast shielding be beneficial in CT of the head?

Contrary to common perception, the advent of third- and fourth-generation scanners has lead to a significant increase in radiation dose to the patient per computed tomography (CT) head scan. With that in mind, a pilot study was designed with the objective of assessing the effectiveness of a dental-style protective bib in reducing the dose to the radiosensitive organs of the neck and thorax. Radiation doses over the thyroid gland and breast were measured with thermoluminenscent dosemeters and an ionization chamber respectively in 110 patients undergoing routine head scans. Half the patients wore the protective bib and collar. With lead protection, the thyroid measurements were reduced by an average of 45 % and the breast measurements by an average of 76 %. Similar results were seen in phantom measurements. Received 23 May 1997; Revision received 22 August 1997; Accepted 19 September 1997     

The effect of dose reduction and feasibility of edge-preserving noise reduction on the detection of liver lesions using MSCT

The purpose of this study was to assess the effect of dose reduction and the potential of noise reduction filters on image quality and the detection of liver lesions using MSCT. Twenty-nine patients with a total of 40 liver lesions underwent 16-slice CT (120 kV; 180 mAs). Virtual noise was added to CT raw datasets simulating effective mAs levels of 155, 130, 105, 80, 55, 30 and 10 mAs. All datasets were post-processed with an edge-preserving noise-reduction filter (ANR-3D), yielding a total of 15 datasets per patient. Ten radiologists performed independent evaluations of image quality, the presence of liver lesions and diagnostic confidence. Quantitative noise and contrast-to-noise ratios (CNR) were obtained. Superior image quality (P < 0.02), reduction of image noise (P < 0.001) and the increase of lesion-to-liver CNR (P < 0.001) were observed in images processed with the ANR-3D filter. Sensitivity for lesion detection remained unchanged down to 105 mAs (CTDI_w 6.6 mGy) without filter and 80 mAs (CTDI_w 5.1 mGy) with ANR-3D. Confidence was rated significantly higher for datasets reconstructed with ANR-3D. The use of a noise-reducing, but edge-preserving filter (ANR-3D) is a promising option to reduce further the radiation dose in liver CT.     

Radiation dose reduction in chest CT—Review of available options

Computed tomography currently accounts for the majority of radiation exposure related to medical imaging. Although technological improvement of CT scanners has reduced the radiation dose of individual examinations, the benefit was overshadowed by the rapid increase in the number of CT examinations. Radiation exposure from CT examination should be kept as low as reasonably possible for patient safety. Measures to avoid inappropriate CT examinations are needed. Principles and information on radiation dose reduction in chest CT are reviewed in this article.     

移动CT头部扫描辐射剂量场的空间分布

目的 初步探究移动CT在进行头部扫描时产生的杂散辐射在空间中的分布,以期为移动CT的辐射防护提供科学依据。方法 选择CareTom移动式多排CT头部序列进行单次扫描,用TLD（LiF：Mg,Cu,P）型热释光探测器测得辐射剂量值,并用Matlab软件绘制出辐射剂量场的空间分布。结果 移动CT前方的辐射剂量稍高于后方,周围空间辐射剂量场则大致呈从前向后的“倒三角”形分布。最大数值出现在中心水平层面,移动CT正前方距离扫描孔中心最近的测量点（距中心0.5 m）,为0.255 mGy。结论 移动CT头部扫描产生的杂散辐射剂量较低,但为了避免长期低剂量辐射的损伤,检查技师和其他医护人员应尽量站在移动CT机的侧面和后方2 m以外的地方,并在扫描时尽可能地配置放射防护装备。     

颈部恶性肿瘤侵犯颈动脉的多层螺旋CT评价

目的评价多层螺旋CT(MSCT)横断面及多平面重建(MPR)在颈部恶性肿瘤侵犯颈动脉方面的应用价值。方法对39个与颈动脉贴邻肿物均行MSCT扫描。2位医生进行盲法阅片,在横断面扫描图像上测量肿瘤包绕颈动脉的角度并分组(≥45°组、≥90°组和≥180°组);在MPR图像上测量肿瘤与颈动脉的最大交角并分组(≥45°组和≥90°组),测量肿瘤与动脉交界面长度、肿瘤最大纵径,计算交界面长度与最大纵径的比值并分组(≥05组、≥08组和=10组)。对比手术及病理结果,比较受侵动脉与未受侵动脉在以上方面的组间差异,并进行统计学分析。结果在横断面扫描图像上,≥90°组和≥180°组对颈动脉受侵判断的准确度高于≥45°组(P<005),≥90°组可兼顾敏感度和特异度。MPR上肿瘤和动脉交界面长径与肿瘤最大纵径的比值,≥08组和=10组对颈动脉受侵判断的准确度高于≥05组(P<005),≥08组的敏感度高于=10组(P<005)且特异度与后者相仿(P>005)。MPR上肿瘤与动脉交界面角度≥45°组和≥90°组对颈动脉受侵判断的准确度差异无统计学意义(P>005),而≥90°组可兼顾敏感度和特异度;MPR显示肿瘤与动脉交界面角度≥90°时,受侵动脉明显多于未受侵动脉(P<005)。结论对于颈动脉受侵的判断,横断面上肿瘤包绕颈动脉角度≥90°,在MPR上肿瘤和动脉交界面长