基于辐射剂量结构化报告的未成年人胸部CT检查体型特异性剂量分析

目的 通过辐射剂量结构化报告（RDSR）及关键影像的自动收集,比较不同年龄段未成年人在胸部CT检查中的体型特异性剂量估计（SSDE）的差别。方法 应用Teamplay软件通过影像归档和通信系统（PACS）自动抓取了404例年龄在0~18岁的胸部CT检查的辐射剂量结构化报告,并通过CT断面影像计算出水等效直径（WED）及SSDE。应用方差分析比较SSDE等剂量参数在不同年龄段的差异,应用Pearson相关分析探讨SSDE与容积CT剂量指数（CTDI_vol）的关系。结果 所有研究对象的SSDE平均值为（4.70±3.29）mGy,且随着年龄增长而增加,在各年龄段之间差异有统计学意义（F=46.11,P<0.01）。SSDE与CTDI_vol在1岁至18岁年龄段呈高度线性相关（｜r｜≥0.92,P<0.01）。结论 在日常工作中应用SSDE进行扫描质量控制,部分年龄段的SSDE水平可以用CTDI_vol线性转换而成,转换因子随年龄段不同而变化。随着年龄的增加,SSDE与CTDI_vol差别逐渐减小,因此SSDE比较适合评估未成年人CT检查辐射剂量。     

不同年龄段儿童与成人肺部CT扫描体型特异性剂量估计

目的 使用常规辐射剂量评估参数与体型特异性剂量估计方法比较不同年龄段儿童和成人肺部CT扫描时所受辐射剂量的差异。方法 回顾性连续抽样华中科技大学同济医学院附属协和医院2017年1月至2018年7月肺部CT扫描患者,共406例,按照年龄分为6组（0~2岁、3~6岁、7~10岁、11~14岁、15~18岁、18岁以上）。基于MATLAB平台开发的dicom数据处理软件,抽取每例患者的容积CT剂量指数（CTDI_vol）值、剂量长度乘积（DLP）值,同时根据美国医学物理师学会（AAPM）220报告提出的体型特异性剂量估计（SSDE）方法,计算每例患者的水当量直径D_w及SSDE值。分析分别使用两种方法时,不同年龄段儿童和成人肺部CT扫描时所受辐射剂量的差异。结果 各年龄组CTDI_vol值均显著低于SSDE值,差异有统计学意义（t=-36.36、-32.83、-30.36、-28.74、-23.89,P<0.05）,不同年龄组SSDE值较CTDI_vol值分别增加137%、94%、79%、57%、42%。成人组的CTDI_vol值同样低于SSDE值,差异有统计学意义（t=-21.92,P<0.05）,SSDE值较CTDI_vol值增加41%。随着年龄的升高,各年龄组儿童患者CTDI_vol值、DLP值、D_w值、SSDE值逐渐升高,并均明显小于成人组,差异有统计学意义（F=63.39、203.28、89.27、103.44,P<0.05）。各年龄组的转换系数f随着年龄的增加显著降低,均明显高于成人组,差异有统计学意义（F=109.83,P<0.05）。结论 在肺部扫描中,相比于成人,CTDI_vol会严重地低估儿童所受的辐射剂量,年龄越小的患者,被低估得越严重,而SSDE方法考虑到受检者体型差异,能够更准确地反映不同患者所受的辐射剂量。     

基于体型特异性剂量估算值推算冠状动脉CT血管成像中患者器官剂量和个体有效剂量的可行性研究

目的 探讨将体型特异性剂量估算值（SSDE）用于估算冠状动脉CT血管成像（CTA）中患者器官剂量和个体有效剂量的可行性。方法 回顾性连续纳入冠状动脉CTA患者421例,均于第3代双源Force型CT采用前瞻性心电门控触发轴扫协议检查。通过Radimetrics计算患者水当量直径以计算每位患者的SSDE;使用Monte Carlo模拟估算患者扫描范围内器官的吸收剂量包括心脏、肺、肝和乳腺。使用国际放射防护委员会（ICRP）103报告的器官敏感加权系数,将患者主要敏感器官的剂量加权求和计算个体有效剂量。使用线性相关分析验证SSDE与器官剂量及个体有效剂量的相关性,并推导基于SSDE估算器官剂量和个体有效剂量的转换系数。使用平均差值比评价该估算方法的准确性。结果 容积CT剂量指数（CTDI_vol）为（16.8±8.7） mGy,SSDE为（20.8±8.8） mGy,个体有效剂量为（4.4±2.9） mSv。基于SSDE估算器官剂量的线性拟合公式为：心脏Y=1.2X-6.4（R²=0.91,P<0.05,平均误差0.1%）;乳腺Y=1.4X-7.4（R²=0.91,P<0.05,平均误差7.9%）;肺脏Y=0.89X-4.6（R²=0.86,P<0.05,平均误差8.3%）;肝脏Y=0.36X-1.8（R²=0.64,P<0.05,平均误差-17.9%）。基于SSDE估算个体有效剂量的线性拟合公式为：男Y=0.21X-1.2（R²=0.92,P<0.05,平均误差0.2%）;女Y=0.39X-2.2（R²=0.93,P<0.05,平均误差1.7%）。结论 在冠状动脉CTA检查中通过SSDE和相应的转换系数可估算被照射器官吸收剂量和个体有效剂量,将有助于在临床工作中实现患者辐射剂量及风险的个性化评估和精准管理。     

两种剂量估算方法在成人胸部CT辐射剂量评估中的应用价值

目的 探讨容积CT剂量指数（CTDI_vol）与体型特异性剂量估算（SSDE）两种辐射剂量估算方法在评估成人胸部CT扫描辐射剂量中的应用价值。方法 回顾性分析2017年3月至4月浙江中医药大学附属第一医院128例进行胸部CT平扫且所有图像均能满足诊断要求的受检者的CTDI_vol与SSDE。将受检者按照不同体质量指数（BMI）分为3组：A组,16 ≤ BMI<21.1 kg/m²,38例;B组,21.1 ≤ BMI<23.9 kg/m²,53例;C组,23.9 ≤ BMI<34.1 kg/m²,37例。在两乳头层面测量每例受检者的前后径（AP）、左右径（LAT）,记录每例受检者的CTDI_vol值,计算每例受检者的有效直径（ED）、转换因子（f_size）和SSDE。同时,比较不同体质量指数组CTDI_vol与SSDE之间的差异。结果 3组受检者的SSDE均高于CTDI_vol,A、B、C组分别增加了50.13%、42.83%、33.68%。CTDI_vol和SSDE估算方法3组辐射剂量比较差异均有统计学意义（t=-48.873、-57.001、-32.651,P<0.05）。3组受检者间的ED、f_size、CTDI_vol和SSDE差异均有统计学意义（F=51.456、47.749、113.916、106.449,P<0.05）。结论 SSDE能够评估不同体型的受检者在胸部CT扫描中所受到的辐射剂量,而CTDI_vol过低地估计了受检者受到的辐射剂量,且BMI越小的受检者被低估的剂量值越大,实际受到的辐射剂量越多。     

本院CT辐射剂量参考水平与警示值的建立及其在胸部CT剂量优化中的运用尝试

目的 通过建立本医疗机构胸部CT辐射剂量参考水平与警示值,并以此指导本院进行胸部CT扫描方案与检查流程的优化,控制CT受检者所受剂量水平。方法 连续调取浙江大学医学院附属第二医院2018年1月1日至2019年12月31日进行胸部CT扫描的205 511例受检者资料,根据检查时间将受检者分为改进前和改进后两组。改进前组为2018年度进行胸部CT检查的受检者,共90 507例,改进后组为2019年度进行检查的受检者,共115 004例。设定2018年度胸部CT辐射剂量分布的均值为本院胸部CT辐射剂量指导水平（DRL）,第75个百分位数和第25个百分位数为本院辐射剂量诊断参考范围（diagnostic reference range,DRR）的上限和下限,第97.5个百分位数为本院CT辐射剂量警示值,超过DRR上限则认为辐射剂量偏高,超过警示值则认为辐射剂量超高。根据2018年度胸部CT超高剂量扫描的原因分析结果,对2019年度受检者的胸部CT的扫描方案与检查流程进行改进。统计改进前后行胸部平扫CT、胸部增强CT、肺癌筛查低剂量CT的受检者人次、偏高剂量扫描人次、超高剂量扫描人次、单次扫描剂量;统计改进前后因不同原因造成剂量超高的人次、占比。将改进前后两组受检者各项参数进行统计学比较。结果 改进后本院胸部平扫CT受检者的平均扫描剂量下降8.67%,两组比较差异有统计学意义（t=55.71,P<0.05）,胸部低剂量CT受检者的平均扫描剂量下降20.13%,差异有统计学意义（t=81.99,P<0.05）;改进后胸部增强CT受检者的平均扫描剂量与改进前差异无统计学意义（P>0.05）;改进后辐射剂量偏高的胸部CT受检者比率较改进前减少9.18%,其中胸部平扫CT、胸部低剂量CT受检者比率分别减少3.66%、17.15%,改进后辐射剂量偏高的胸部增强CT受检者比率增加1.7%;改进后辐射剂量超高的胸部平扫CT、胸部增强CT、胸部低剂量CT受检者比率较改进前分别减少0.55%、1.06%、1.74%;超高剂量扫描的受检者中,改进后剂量可优化的受检者比率较改进前分别减少4.72%、31.49%、19.18%。结论 建立本院胸部CT辐射剂量参考水平及剂量警示值有助于推动剂量优化,降低受检者平均剂量,避免高剂量扫描。     

宁夏儿童头颅、胸部CT辐射剂量状况分析

目的 评估宁夏地区儿童头颅、胸部CT检查的辐射剂量水平,为不同年龄段儿童的CT辐射剂量优化提供基础。方法 采用分层整群抽样的方法,实地采集宁夏地区不同市、县、区不同规模医院1~2周内儿童（≤15岁）头颅、胸部CT的扫描参数、容积CT剂量指数（CTDI_vol）及剂量长度乘积（DLP）,计算患者有效剂量（E）值;并将CTDI_vol、DLP的第75百分位数（P₇₅）与其他国家推荐的DRL值进行比较;所有儿童分4个年龄组：<1岁、1~5岁、6~10岁、11~15岁。结果 走访调查39家医院,调查CT设备47台,采集头颅断层扫描1 134例,胸部平扫636例。头颅CTDI_vol、DLP的P₇₅分别为：<1岁：44.2 mGy、456.2 mGy·cm;1~5岁：57.2 mGy、659.6 mGy·cm;6~10岁：61.1 mGy、668.7 mGy·cm;11~15岁：63.6 mGy、849.3 mGy·cm。胸部CTDI_vol、DLP的P₇₅分别为：<1岁：5.0 mGy、89.2 mGy·cm;1~5岁：5.9 mGy、124.8 mGy·cm;6~10岁：6.0 mGy、167.9 mGy·cm;11~15岁：7.1 mGy、235.0 mGy·cm。结论 宁夏地区儿童胸部CT的辐射剂量与其他报道相近,但头颅CT的辐射剂量相对偏高,且各年龄段均存在偏高现象,尤以婴儿患者较著;应加强宁夏地区儿童头颅CT的辐射剂量优化与监管,增强儿科医生、放射科医生的剂量控制意识,提高对辐射相关风险的认识。     

器官剂量调制技术在女性胸部CT成像中对乳腺的保护作用

目的 探讨器官剂量调制（organ dose modulation,ODM）技术在女性胸部CT扫描中对乳腺区辐射剂量和图像质量的影响。方法 前瞻性收集临床需要行胸部CT检查的女性患者112例,按照检查的先后顺序将患者分为两组：对照组56例,采用常规平扫;试验组56例,平扫采用ODM技术。分析两组患者乳腺区域前、左、后、右4个方向的管电流分布情况,评价ODM对乳腺区域图像质量和辐射剂量的影响。结果 对照组患者前、后方向上管电流均为（128±43）mA,而试验组患者前方向上管电流较后方向管电流低（t=-18.701,P < 0.01）。试验组4个方向管电流均较对照组降低（t=11.71~20.22,P < 0.01）。试验组患者的容积CT剂量指数和有效剂量均较对照组降低（t=3.58、3.55,P < 0.05）。两组患者间图像质量的客观和主观评价指标差异均无统计学意义（P > 0.05）。结论 在女性胸部CT扫描时应用ODM技术,可以在不改变图像质量的前提下,降低乳腺区辐射剂量,保护敏感器官。     

儿童CT检查中扫描参数的优化

目的 了解儿童CT检查扫描条件选择及其所致辐射剂量的相关性,以期通过适当调节mAs、扫描长度等参数,降低儿童CT检查患者受照剂量。方法 比较江苏省7家医院不同年龄组（<1岁、1~5岁、6~10岁和11~15岁）儿童头颅、胸部、腹部多排螺旋CT检查主要扫描参数的差异。选用相同的检查参数在TM160剂量模体上测量CTDI₁₀₀,计算DLP,并通过经验加权因子,估算出不同部位检查的有效剂量（E）。对mAs、扫描长度和DLP进行多元线性回归分析,比较两家典型医院由于选择扫描条件不同所导致的剂量差异。结果 儿童头颅、胸部、腹部CT检查所致患者的有效剂量均值分别为2.46、5.69、11.86 mSv,各部位检查DLP与mAs、扫描长度均呈正相关（r=0.81、0.81、0.92,P<0.05）。较高的mAs选择,致使本研究各年龄组儿童胸腹部CT检查有效剂量是德国Galanski等研究的1.2~3.0倍;B医院各年龄组腹部检查选择了较高的扫描长度,以致其所致有效剂量均高于本研究均值。结论 建议通过合理优化儿童不同部位CT检查mAs、扫描长度等扫描参数,降低受检者所受辐射风险。     

单侧乳腺癌放疗中健侧乳腺受照剂量及其诱发癌症风险预测

目的 分析单侧乳腺癌放疗所致健侧乳腺的剂量,并估算放疗诱发健侧乳腺癌的风险。方法 在同一医院调查49例接受单侧乳腺放疗患者的基本情况,从治疗计划系统上获取其健侧乳腺的辐射剂量并进行统计分析;利用美国电离辐射生物效应委员会报告Ⅶ第2部分（BEIR Ⅶ phase 2）推荐的风险模型,结合我国人口寿命表,预测不同年龄段单侧乳腺癌患者接受放疗诱发健侧乳腺癌的风险。结果 患者的处方剂量均为50 Gy,健侧乳腺的平均剂量为（1.21±0.89）Gy （0.14~3.59 Gy）,最大点剂量平均为（17.42±13.20）Gy （0.98~45.27 Gy）;健侧乳腺的最大点剂量和平均剂量变化幅度大,且有显著相关性（R=0.527,P=0.000）,不同年龄段患者的健侧乳腺平均剂量差异无统计学意义（P>0.05）。基于健侧乳腺的平均剂量,估算出受照年龄为35、40、50、60、70和80岁患者的健侧乳腺癌终生归因风险分别为2 449/10万人、1 857/10万人、994/10万人、446/10万人、173/10万人和55/10万人。结论 患者接受单侧乳腺癌放疗过程中,其健侧乳腺剂量可达1 Gy水平,可能增加健侧乳腺癌发生风险对年轻患者不容忽视,在制定放射治疗计划时应尽可能控制对患者健侧乳腺的照射。     

头、胸部CT扫描所致儿童甲状腺剂量估算及其癌症风险预测

目的 估算儿童接受头部、胸部CT扫描所致其甲状腺剂量及其癌症风险。方法 通过医院影像归档和通信系统(PACS)提取某医院2012年接受头部、胸部CT扫描儿童DCIOM文件,利用DCMTK软件获取患者CT扫描参数,使用CT-Expo剂量估算软件估算CT扫描所致患者甲状腺剂量,利用美国电离辐射生物效应委员会(BEIR)Ⅶ风险模型结合中国2008年癌症发病率及寿命表预测单次头部、胸部CT扫描所致儿童甲状腺癌的风险。结果 不同年龄段儿童CT扫描参数大致相同,单次头部CT扫描所致儿童(男、女)甲状腺剂量范围为1.2~2.0 mGy,其甲状腺癌风险最高的为新生儿(女)9.6/10万人口;单次胸部CT扫描所致儿童(男、女)甲状腺剂量范围约为8.1~38.0 mGy,其甲状腺癌风险最高为新生儿(女)244.7/10万人;CT所致儿童甲状腺剂量与癌症风险均随其年龄的增加而逐渐减小。结论 胸部CT扫描所致儿童甲状腺剂量较高,尤其是对于新生儿患者,应注意儿童接受胸部CT扫描时对甲状腺及其他辐射敏感器官的防护。     

有效剂量与有效剂量当量的异同

本文作者主要讨论ＩＣＲＰ６０号出版物中提出的有效剂量，与ＩＣＲＰ２６号出版物中的有效剂量当量，在概念和使用上比较它们的异同。     

多层螺旋CT肺部低剂量与常规剂量检查的放射剂量评估

目的比较多层螺旋CT肺部低剂量与常规剂量检查的X线辐射剂量,为低剂量多层螺旋CT普查早期肺癌提供剂量参数. 资料与方法肺部低剂量与常规剂量多层螺旋CT扫描共54例.其中,低剂量扫描24例,扫描参数为:120 kV,20 mAs,准直器4×5 mm,重建层厚8 mm,床速30 mm/周,螺距为7,扫描时间0.5 s/周;常规剂量扫描30例,扫描参数为:120 kV,90 mAs,准直器4×5 mm,重建层厚8 mm,床速30 mm/周,螺距为7,扫描时间0.5 s/周.观察并计算两种扫描剂量的权重CT剂量指数(CTDIw),有效mAs,总mAs,剂量长度乘积(DLP)及有效辐射剂量. 结果肺部低剂量扫描的CTDIw为1.38 mGy,是常规剂量扫描(6.21 mGy)的22.2%;低剂量扫描的DLP为44 mGy*cm,明显低于常规剂量扫描的189 mGy*cm(P＜0.01);低剂量扫描的总mAs为459,是常规剂量扫描(1 308)的35.1%;低剂量扫描的X线最大有效辐射剂量为0.9 mSv,明显低于常规剂量扫描的4.2 mSv(P＜0.01). 结论多层螺旋CT肺部低剂量扫描(20 mAs)的有效辐射剂量为常规剂量扫描的21.4%,适用于高危人群普查早期肺癌.     

Radiation exposure to premature infants in a neonatal intensive care unit in Turkey

OBJECTIVE: The aim of this work was to determine the radiation dose received by infants from radiographic exposure and the contribution from scatter radiation due to radiographic exposure of other infants in the same room. MATERIALS AND METHODS: We retrospectively evaluated the entrance skin doses (ESDs) and effective doses of 23 infants with a gestational age as low as 28 weeks. ESDs were determined from tube output measurements (ESD(TO)) (n = 23) and from the use of thermoluminescent dosimetry (ESD(TLD)) (n = 16). Scattered radiation was evaluated using a 5 cm Perspex phantom. Effective doses were estimated from ESD(TO) by Monte Carlo computed software and radiation risks were estimated from the effective dose. ESD(TO) and ESD(TLD) were correlated using linear regression analysis. RESULTS: The mean ESD(TO) for the chest and abdomen were 67 microGy and 65 microGy per procedure, respectively. The mean ESD(TLD) per radiograph was 70 microGy. The measured scattered radiation range at a 2 m distance from the neonatal intensive care unit (NICU) was (11-17 microGy) per radiograph. Mean effective doses were 16 and 27 microSv per procedure for the chest and abdomen, respectively. ESD(TLD) was well correlated with ESD(TO) obtained from the total chest and abdomen radiographs for each infant (R(2) = 0.86). The radiation risks for childhood cancer estimated from the effective dose were 0.4 x 10(-6) to 2 x 10(-6) and 0.6 x 10(-6) to 2.9 x 10(-6) for chest and abdomen radiographs, respectively. CONCLUSION: The results of our study show that neonates received acceptable doses from common radiological examinations. Although the contribution of scatter radiation to the neonatal dose is low, considering the sensitivity of the neonates to radiation, further protective action was performed by increasing the distance of the infants from each other.     

Size-specific dose estimates: Localizer or transverse abdominal computed tomography images?

AIM: To investigate effect of body dimensions obtained from localizer radiograph and transverse abdominal computed tomography (CT) images on Size Specific Dose Estimate.METHODS: This study was approved by Institutional Review Board and was compliant with Health Insurance Portability and Accountability Act. Fifty patients with abdominal CT examinations (58 ± 13 years, Male:Female 28:22) were included in this study. Anterior-posterior (AP) and lateral (Lat) diameters were measured at 5 cm intervals from the CT exam localizer radiograph (simple X-ray image acquired for planning the CT exam before starting the scan) and transverse CT images. Average of measured AP and Lat diameters, as well as maximum, minimum and mid location AP and Lat were measured on both image sets. In addition, off centering of patients from the gantry iso-center was calculated from the localizers. Conversion factors from American Association of Physicists in Medicine (AAPM) report 204 were obtained for AP, Lat, AP + Lat, and effective diameter (√ AP * Lat) to determine size specific dose estimate (SSDE) from the CT dose index volume (CTDI_vol) recorded from the dose reports. Data were analyzed using SPSS v19.RESULTS: Total number of 5376 measurements was done. In some patients entire body circumference was not covered on either projection radiograph or transverse CT images; hence accurate measurement of AP and Lat diameters was not possible in 11% (278/2488) of locations. Forty one patients were off-centered with mean of 1.9 ± 1.8 cm (range: 0.4-7 cm). Conversion factors for attained diameters were not listed on AAPM look-up tables in 3% (80/2488) of measurements. SSDE values were significantly different compared to CTDI_vol, ranging from 32% lower to 74% greater than CTDI_vol.CONCLUSION: There is underestimation and overestimation of dose comparing SSDE values to CTDI_vol. Localizer radiographs are associated with overestimation of patient size and therefore underestimation of SSDE.     

A review of dosimetry used in epidemiological studies considered to evaluate the linear no-threshold (LNT) dose-response model for radiation protection

Abstract

Background: Accurate dosimetry is key to deriving the dose response from radiation exposure in an epidemiological study. It becomes increasingly important to estimate dose as accurately as possible when evaluating low dose and low dose rate as the calculation of excess relative risk per Gray (ERR/Gy) is very sensitive to the number of excess cancers observed, and this can lead to significant errors if the dosimetry is of poor quality. By including an analysis of the dosimetry, we gain a far better appreciation of the robustness of the work from the standpoint of its value in supporting the shape of the dose response curve at low doses and low dose rates. This article summarizes a review of dosimetry supporting epidemiological studies currently being considered for a re-evaluation of the linear no-threshold assumption as a basis for radiation protection. The dosimetry for each study was evaluated based on important attributes from a dosimetry perspective. Our dosimetry review consisted of dosimetry supporting epidemiological studies published in the literature during the past 15 years. Based on our review, it is clear there is wide variation in the quality of the dosimetry underlying each study. Every study has strengths and weaknesses. The article describes the results of our review, explaining which studies clearly stand out for their strengths as well as common weaknesses among all investigations.

Purpose: To summarize a review of dosimetry used in epidemiological studies being considered by the National Council on Radiation Protection and Measurements (NCRP) in an evaluation of the linear no-threshold dose-response model that underpins the current framework of radiation protection.

Materials and methods: The authors evaluated each study using criteria considered important from a dosimetry perspective. The dosimetry analysis was divided into the following categories: (1) general study characteristics, (2) dose assignment, (3) uncertainty, (4) dose confounders (5) dose validation, and (6) strengths and weaknesses of the dosimetry. Our review focused on approximately 20 studies published in the literature primarily during the past 15 years.

Results: Based on the review, it is clear there is wide variation in the quality of the dosimetry underlying each study. Every study has strengths and weaknesses. This paper describes the results of our review, identifies common weaknesses among all investigations, and recognizes studies that clearly stand out for their overall strengths.

Conclusions: The paper concludes by offering recommendations to investigators on possible ways in which dosimetry could be improved in future epidemiological studies.     

大剂量增强MR检查对脑部病变的诊断价值

探讨大剂量增强ＭＲ检查对显示脑部隐匿性小病灶以及改善病灶的显示和诊断的准确性。材料与方法：７４例脑部病变包括肺癌脑转移,乳腺癌脑转移,爱滋病脑弓形体病,胶质母细胞瘤,脑膜瘤,分别进行标准剂量和大剂量增强ＭＲ检查,两次查间隔时间不超过３天。     

CT Radiation Dose Optimization and Estimation: an Update for Radiologists

In keeping with the increasing utilization of CT examinations, the greater concern about radiation hazards from examinations has been addressed. In this regard, CT radiation dose optimization has been given a great deal of attention by radiologists, referring physicians, technologists, and physicists. Dose-saving strategies are continuously evolving in terms of imaging techniques as well as dose management. Consequently, regular updates of this issue are necessary especially for radiologists who play a pivotal role in this activity. This review article will provide an update on how we can optimize CT dose in order to maximize the benefit-to-risk ratio of this clinically useful diagnostic imaging method.     

Strategies for reduction of radiation dose in cardiac multislice CT

Because cardiac computed tomography (CT) (mainly coronary CT angiography) is a very promising technique, used more and more for coronary artery evaluation, the benefits and risks of this new low-invasive technique must be balanced. Radiation dose is a major concern for coronary CT angiography, especially in case of repeated examinations or in particular subgroups of patients (for example young female patients). Radiation dose to patient tends to increase from 16- to 64-slice CT. Radiation exposure in ECG-gated acquisitions may reach up to 40 mSv; considerable differences are attributable to the performance of CT machines, to technical dose-sparing tools, but also to radiological habits. Setting radiation dose at the lowest level possible should be a constant goal for the radiologist. Current technological tools are detailed in regard to their efficiency. Optimisation is necessary, by a judicious use of technological tools and also by individual adaptation of kV or mAs. This paper reviews the different current strategies for radiation dose reduction, keeping image quality constant. Data from the literature are discussed, and future technological developments are considered in regards to radiation dose reduction. The particular case of paediatric patients with congenital heart disease is also addressed.     

加速器机载kV锥形束CT有效剂量的分析

目的 分析医用直线加速器机载kV锥形束CT扫描过程中患者的有效剂量随扫描条件的变化.方法 用PTW TM30009电离室分别在T40017头模和T40016躯干模体中,改变XVI锥形柬CT的管电压、毫安秒、准直器以及机架旋转范围等参数测量加权CT剂鼍指数,计算相应的剂量长度乘积和有效剂量.结果 kV锥形束CT的加权剂量指数和有效剂量随管电压呈二次方变化,随毫安秒线性变化,与准直器以及机架旋转范围密切相关.临床常用条件下,kV锥形束CT单次扫描的剂最长度乘积和有效剂量低于参考剂量水平.结论 锥形束CT扫描过程中患者接受的有效剂量与扫描条件密切相关.锥形束CT扫描时,应该根据患者的解剖部位合理选择成像参数,最大限度减少患者接受剂量.     

加速器机载kV锥形束CT有效剂量的分析

目的 分析医用直线加速器机载kV锥形束CT扫描过程中患者的有效剂量随扫描条件的变化.方法 用PTW TM30009电离室分别在T40017头模和T40016躯干模体中,改变XVI锥形柬CT的管电压、毫安秒、准直器以及机架旋转范围等参数测量加权CT剂鼍指数,计算相应的剂量长度乘积和有效剂量.结果 kV锥形束CT的加权剂量指数和有效剂量随管电压呈二次方变化,随毫安秒线性变化,与准直器以及机架旋转范围密切相关.临床常用条件下,kV锥形束CT单次扫描的剂最长度乘积和有效剂量低于参考剂量水平.结论 锥形束CT扫描过程中患者接受的有效剂量与扫描条件密切相关.锥形束CT扫描时,应该根据患者的解剖部位合理选择成像参数,最大限度减少患者接受剂量.