CT扫描所致受检者器官剂量的体模实验研究

目的 了解不同部位X射线CT扫描所致受检者器官或组织的吸收剂量及其分布。方法 实测体模中重要组织器官的CT值,并转换成线性吸收系数与人体正常值进行比较;在体模中 布放光致辐射发光玻璃剂量计,分别模拟测量头部、胸部、腹部和盆腔CT扫描所致受检者主要器官或组织的吸收剂量。结果 实验用仿真人体模具有良好的组织等效性。头部扫描吸收剂量最大的器官是大脑,胸部扫描吸收剂量较大的器官是甲状腺、乳腺、肺和食道,腹部扫描吸收剂量较大的器官是肝、胃、结肠和肺,单次盆腔扫描体所致骨表面和结肠的吸收剂量可达50 mGy以上。结论 X射线CT扫描所致受检者的器官剂量及其分布随扫描部位的不同而异。盆腔扫描时结肠、红骨髓、性腺和膀胱等主要器官的吸收剂量较大,应引起注意。     

苏州市数字X射线摄影和CT医疗照射所致公众剂量负担的研究

目的 估算2017年苏州市医用数字X射线摄影（DR）和CT所致全市公众有效剂量负担。方法 利用分层随机抽样方法,通过医学影像存档与通信系统（PACS）和放射科信息系统（RIS）,采集苏州市27家医疗机构2017年DR和CT诊疗频度数据。对于DR,使用剂量面积乘积测量仪测量受检者常见投照部位的剂量面积乘积（DAP）,估算出有效剂量;对于CT,测量头部、胸部和腹部扫描时的加权CT剂量指数（CTDI_w）,结合扫描参数,估算出有效剂量。根据各部位的扫描人次和有效剂量,估算苏州市DR和CT医疗照射所致公众剂量负担。结果 DR检查中,腹部前后位、骨盆前后位、头颅侧位和后前位、胸部侧位和后前位、胸椎侧位和后前位、腰椎侧位和后前位一次检查所致受检者有效剂量分别为0.565、0.280、0.016、0.012、0.111、0.060、0.100、0.102、0.307和0.152 mSv。CT检查中,头部、胸部、腹部一次检查所致受检者有效剂量分别为1.33、5.75和7.31 mSv。2017年苏州市DR和CT医疗照射所致公众剂量为9 593.07人·Sv,人均年有效剂量为0.898 mSv。结论 CT医疗照射对公众剂量的贡献量远大于DR照射的贡献量。苏州市DR和CT医疗照射所致公众剂量负担处于高水平,需要引起相关卫生行政部门的重视。     

三种双剂量计法估算介入术者有效剂量比较

目的 比较3种双剂量计算法估算介入术者有效剂量的优劣。方法 在仿真人体模内布放热释光剂量片并将体模置于介入术者位置,在体模外穿戴铅防护衣、铅围脖和铅帽,并在铅衣内左前胸和铅围脖外左侧放置个人剂量计,在手术台上放置散射模体,分别为CIRS放疗调强体模和CT剂量检测模体,模拟介入手术曝光条件曝光一定时间,通过器官组织吸收剂量估算有效剂量;以3种双剂量计法计算有效剂量并与体模法结果进行比较。结果 得到两组各4个有效剂量结果,即使用CIRS放疗调强体模时,体模法、NCRP法、Niklason法和Boetticher法分别为0.138、0.097、0.161和0.173 mSv;使用CT剂量检测模体时分别为0.018、0.013、0.019和0.026 mSv。其中,Niklason法与体模法最为接近。结论 对于估算介入术者的有效剂量,Niklason法更为准确和实用。     

基于中国参考人的典型CT扫描患者剂量模拟与分析

目的 基于中国参考人体模,对典型CT患者剂量进行模拟与分析。开发一款在线评估CT扫描所致受检者器官吸收剂量和有效剂量的软件,为快速评估CT扫描辐射剂量提供工具。方法 采用蒙特卡罗方法,对GE LightSpeed 16型号CT进行建模,基于中国参考人体模计算中国成年男性、女性和1岁儿童受CT扫描照射后各组织器官的剂量,建立单层轴扫器官剂量数据库。开发基于web的CT剂量评估软件,根据用户输入的CT扫描参数,从器官剂量数据库中读取数据并快速计算器官吸收剂量和有效剂量。结果 开发了一款新的CT扫描剂量评估软件,可用于评估中国成年男女和1岁儿童在不同型号CT检查中,不同管电压、管电流、准直器宽度等CT参数下的器官剂量。CT扫描剂量评估软件的计算结果与两个文献数据进行对比,对于完全包含在扫描范围内的器官剂量差异较小,相对差异分别在15%和25%以内。结论 CT扫描剂量评估软件为简单快速评估CT扫描辐射剂量提供了有力的工具。     

兆伏级锥形束CT图像引导放疗所致鼻咽癌患者剂量的探讨

目的 评价和估算兆伏级锥形束CT(MV CBCT)成像系统在图像引导放疗中所致鼻咽癌患者的辐射剂量。方法 选择MV CBCT系统头颈部8 MU扫描预案,利用0.65 cm³指型电离室和CT头部剂量体模测量出体模不同位置的吸收剂量。并利用XiO治疗计划系统模拟MV CBCT扫描过程,计算体模电离室测量点的吸收剂量和鼻咽癌患者肿瘤靶区及危及器官的吸收剂量。结果 体模不同位置吸收剂量的测量值和计算值具有很好的一致性,相对误差均小于3.5%。MV CBCT图像引导放疗所致鼻咽癌患者肿瘤靶区平均剂量为6.43 cGy,脑干、脊髓和视交叉的平均剂量分别为6.36 、6.83和6.90 cGy,左、右视神经平均剂量分别为7.70和7.53 cGy,左、右腮腺平均剂量分别为6.86和6.43 cGy。结论 使用治疗计划系统模拟MV CBCT图像采集过程估算剂量准确、可靠。在设计患者治疗计划时,要充分考虑MV CBCT图像采集过程所致患者剂量。     

CT头颈部检查所致婴幼儿眼晶状体吸收剂量估算方法的模体研究

目的 探讨CT不同扫描方案检查所致婴幼儿眼晶状体吸收剂量估算方法,并寻求快速估算眼晶状体吸收剂量的实用方法。方法 通过设置7种临床标准扫描方案,对1岁年龄组仿真模体进行扫描,利用布放在模体不同位置的热释光探测器（TLD）测量剂量,最后测量结果分别用组织因子转换和个人剂量当量转换两种方法来估算眼晶状体吸收剂量,同时将眼晶状体吸收剂量与CT剂量指数（CTDI）建立线性回归方程。结果 7种临床标准儿童扫描方案CT检查所致的婴幼儿眼晶状体吸收剂量分别为（9.96±0.69）mGy（头部轴向）、（7.01±0.42）mGy（头部螺旋）、（12.60±0.97）mGy（副鼻窦）、（12.97±0.42）mGy（内耳高分辨）、（0.63±0.03）mGy（颈部软组织）、（8.89±0.44）mGy（颈部颈椎）和（0.34±0.01）mGy（胸部常规）,不同组之间剂量差异有统计学意义（F=846.826,P<0.05）。不同扫描部位,CTDI值与眼晶状体吸收剂量之间均存在线性关系（r=0.986~0.999,P<0.05）。结论 采用儿童CT扫描条件,婴幼儿眼晶状体吸收剂量单次剂量范围一般不会超过阈剂量。另外,通过读取CTDI值,利用线性关系,可快速估算眼晶状体吸收剂量。     

5岁儿童仿真模体千伏锥束CT模拟剂量测量

目的 利用热释光探测器（TLD）在CIRS 5岁仿真儿童模体内测量瓦里安千伏锥束CT（kV-CBCT）标准扫描参数下各重要器官剂量,并以此计算有效剂量。方法 挑选一致性在2%以内的TLD并退火。首先基于相同骨盆扫描模式分别用CT电离室和TLD测量CIRS骨盆仿真模体相同体积内的剂量和读数,二者比值即为TLD转换系数;将夹在组织等效插件中的TLD放入儿童模体器官内预留的插孔,在头部、胸部和骨盆3种标准扫描条件模式下,测量器官剂量,并计算有效剂量。结果 TLD转换系数是3.91 mGy/每读数;在头部、胸部和骨盆3种标准扫描条件下,得出全身有效剂量分别是0.63、6.85和19.3 mSv。结论 用CT电离室刻度过的TLD测量kV-CBCT给儿童仿真模体带来的辐射剂量的方法具有可行性。本研究中骨盆扫描条件的有效剂量高于胸部和头部,即该条件预期产生的辐射危害较大,诱发继发性癌症风险较高。     

一名工业γ射线探伤意外受照人员物理剂量估算

目的 对1名工业探伤过量受照人员物理剂量进行估算。方法 获取了主要照射参数,照射时间为8 min,照射方式为各向同性点源体外照射,放射源活度为2.183 TBq,采用中国参考人体素体模,利用基于Geant4二次开发的程序进行蒙特卡罗计算,得到各部位的吸收剂量。结果 给出了受照者手部剂量分布图,其中手掌大部分区域受照剂量在2~10 Gy,手指部分为10~20 Gy;估算了受照者体内23个组织或器官的吸收剂量,数值范围为0.012~0.207 Gy。结论 物理剂量估算方法可以快速评估伤者重点受照部位的局部剂量分布,为医疗救治提供重要参考。     

单层与多层螺旋CT所致儿童受检者辐射剂量研究

目的 研究和评价儿童受检者在单层与多层螺旋CT扫描中所受到的辐射剂量。方法 测试21台CT机的头部和体部剂量指数,并结合0～1岁组、5岁组、10岁组儿童和成年人的头部和胸部常规扫描条件,计算CTDI_w、CTDI_vol、DLP值,再由DLP与有效剂量转换系数计算头部和胸部常规扫描所致各年龄组儿童和成年人的有效剂量。 结果 单位mAs的头部CTDI大于体部CTDI;在头部常规扫描中,0～1岁组、5岁组、10岁组儿童受到的有效剂量分别为2.2、1.3、1.1 mSv;在胸部常规扫描中,0～1岁组、5岁组、10岁组儿童受到的有效剂量分别为5.3、3.1、3.4 mSv;每单位mAs所致儿童有效剂量平均比成人高1.8倍;多层CT的儿童头部CTDI_vol、DLP、有效剂量值均大于单层与双层CT,多层与双层CT的儿童胸部CTDI_vol、DLP、有效剂量值均小于单层CT。 结论 与成年人相比,儿童在CT检查中可能受到更大辐射危害,应严格遵循儿童CT检查适应证,并合理选择CT扫描参数,尽可能降低儿童受到的辐射剂量。     

Implagraphy牙颌面锥形束CT不同扫描体位的辐射剂量对比研究

目的 测算Implagraphy牙颌面锥形束CT(CBCT)体模不同扫描体位的组织器官吸收剂量、当量剂量及有效剂量,为相应的防护措施提供客观依据。方法 使用仿真成年男性头颈部体模及热释光剂量计,分别测量Implagraphy CBCT下颌、上颌及颞下颌关节(TMJ)扫描时脑垂体、眼晶状体、腮腺、颌下腺、舌下腺、颅骨板障、下颌松质骨、颈椎松质骨、颊部皮肤、颈部皮肤、甲状腺、食管及口腔黏膜等组织器官的吸收剂量,计算眼晶状体、皮肤的当量剂量,及Implagraphy CBCT不同扫描体位的有效剂量E₁₉₉₀及E₂₀₀₇。结果 Implagraphy CBCT各扫描体位的吸收剂量分别为:下颌扫描(0.99±0.09)~(12.85±0.09)mGy,上颌扫描(0.93±0.01)~(13.07±0.02)mGy,TMJ扫描(0.68±0.01)~(10.18±0.04)mGy,相同组织器官在不同扫描体位的吸收剂量的差异具有统计学意义(F=19.61~30992.27,P<0.05)。在不同扫描体位,眼晶状体及皮肤的当量剂量分别为(1.11±0.07)~(5.76±0.06)mSv和(6.96±0.06)~(10.64±0.07)mSv,差异具有统计学意义(F=4473.02、9385.50,P<0.05)。有效剂量E₁₉₉₀及E₂₀₀₇分别为:下颌扫描(191.35±1.53)和(325.17±2.58)μSv,上颌扫描(106.62±2.17)和(226.28±2.81)μSv,TMJ扫描(104.21±1.02)和(142.36±1.90)μSv。结论 在牙颌面CBCT检查过程中,采用尽可能小的扫描视野、准确地扫描体位,正确使用铅胶帽、围领及防护镜等屏蔽措施,使X射线辐射照射保持在可以合理达到的尽可能低的水平。     

Lifetime attributable risk of cancer incidence and mortality in routine digital radiology procedures

PurposeDigital radiography has the potential to improve the practice of radiography but it also has the potential to significantly increase patient doses. Considering rapidly growing digital radiography in many centers, concerns rise about increasing the collective dose of the human population and following health effects. This study aimed to estimate organ and effective doses and calculate the lifetime attributable risk (LAR) of cancer incidence and mortality in digital radiography procedures in Iran.MethodsOrgan and effective doses of 12 routine digital radiography examinations including the skull, cervical spine, chest, thoracic spine, lumbar spine, pelvic and abdomen were estimated using PCXMC software based on Monte Carlo simulation method. Then, LARs of cancer incidence and mortality were estimated using the BEIR VII method.ResultsOrgan doses ranged from 0.01 to a maximum of 2.5 mGy while effective doses ranged from 0.01 to 0.7 mSv. Radiation risk showed dependence on the X-ray examination type and the patient's sex and age. In skull and cervical X-rays, the thyroid; in the chest and thoracic spine X-rays, the lung, and breast; and in the lumbar spine, pelvic and abdominal X-rays, the colon and bladder had the highest LAR of cancer incidence and mortality. Furthermore, younger patients and also females were at higher radiation risk.ConclusionThe lifetime attributable risk of cancer incidence and mortality due to radiation exposure is not trivial. Therefore efforts should be made to reduce patient doses while maintaining image quality.     

Dose reduction in maxillofacial imaging using low dose Cone Beam CT

Objectives(a) To measure the absorbed dose at certain anatomical sites of a RANDO phantom and to estimate the effective dose in radiographic imaging of the jaws using low dose Cone Beam computed tomography (CBCT) and (b) to compare the absorbed and the effective doses between thyroid and cervical spine shielding and non-shielding techniques.Study designThermoluminescent dosimeters (TLD-100) were placed at 14 sites in a RANDO phantom, using a Cone Beam CT device (Newtom, Model QR-DVT 9000, Verona, Italy). Dosimetry was carried out applying two techniques: in the first, there was no shielding device used while in the second one, a shielding device (EUREKA!, TRIX) was applied for protection of the thyroid gland and the cervical spine. Effective dose was estimated according to ICRP₆₀ report (E_ICRP). An additional estimation of the effective dose was accomplished including the doses of the salivary glands (E_SAL). A Wilcoxon Signed Ranks Test was used for statistical analysis.ResultsIn the non-shielding technique the absorbed doses ranged from 0.16 to 1.67 mGy, while 0.32 and 1.28 mGy were the doses to the thyroid and the cervical spine, respectively. The effective dose, E_ICRP, was 0.035 mSv and the E_SAL was 0.064 mSv. In the shielding technique, the absorbed doses ranged from 0.09 to 1.64 mGy, while 0.18 and 0.95 mGy were the respective values for the thyroid and the cervical spine. The effective dose, E_ICRP, was 0.023 mSv and E_SAL was 0.052 mSv.ConclusionsThe use of CBCT for maxillofacial imaging results in a reduced absorbed and effective dose. The use of lead shielding leads to a further reduction of the absorbed doses of thyroid and cervical spine, as well as the effective dose.     

Analysis of effective and organ dose estimation in CT when using mA modulation: A single scanner pilot study

IntroductionEffective dose (ED) estimation in CT examinations can be obtained by combining dose length product (DLP) with published ED per DLP coefficients or performed using software. These methods do not account for tube current (mA) modulation which is influenced by patient size. The aim of the work was to compare different methods of organ and ED estimation to measured values when using mA modulation in CT chest, abdomen and pelvis examinations.MethodOrgan doses from CT of the chest, abdomen and pelvis were measured using digital dosimeters and a dosimetry phantom. ED was calculated. Six methods of estimating ED accounting for mA modulation were performed using ImPACT CTDosimetry and Dose Length Product to ED coefficients. Corrections for the phantom mass were applied resulting in 12 estimation methods. Estimated organ doses from ImPACT CTDosimtery were compared to measured values.ResultsCalculated EDs were; chest 12.35 mSv (±1.48 mSv); abdomen 8.74 mSv (±1.36 mSv) and pelvis 4.68 mSv (±0.75 mSv). There was over estimation in all three anatomical regions. Correcting for phantom mass improved agreement between measured and estimated ED. Organ doses showed overestimation of dose inside the scan range and underestimation outside the scan range.ConclusionReasonable estimation of effective dose for CT of the chest and abdomen can be obtained using ImPACT CTDosimetry software or k-coefficients. Further work is required to improve the accuracy of ED estimation from CT of the pelvis. Accuracy of organ dose estimation has been shown to depend on the inclusion or exclusion of the organ from the scan range.     

Tomosynthesis of the thoracic spine: added value in diagnosing vertebral fractures in the elderly

Objectives

Thoracic spine radiography becomes more difficult with age. Tomosynthesis is a low-dose tomographic extension of radiography which may facilitate thoracic spine evaluation. This study assessed the added value of tomosynthesis in imaging of the thoracic spine in the elderly.

Methods

Four observers compared the image quality of 50 consecutive thoracic spine radiography and tomosynthesis data sets from 48 patients (median age 67 years, range 55–92 years) on a number of image quality criteria. Observer variation was determined by free-marginal multirater kappa. The conversion factor and effective dose were determined from the dose–area product values.

Results

For all observers significantly more vertebrae were seen with tomosynthesis than with radiography (mean 12.4/9.3, P?<?0.001) as well as significantly more fractures (mean 0.9/0.7, P?=?0.017). The image quality score for tomosynthesis was significantly higher than for radiography, for all evaluated structures. Tomosynthesis took longer to evaluate than radiography. Despite this, all observers scored a clear preference for tomosynthesis. Observer agreement was substantial (mean κ?=?0.73, range 0.51–0.94). The calibration or conversion factor was 0.11 mSv/(Gy cm²) for the combined examination. The resulting effective dose was 0.87 mSv.

Conclusion

Tomosynthesis can increase the detection rate of thoracic vertebral fractures in the elderly, at low added radiation dose.

Key Points

? Tomosynthesis helps evaluate the thoracic spine in the elderly. ? Observer agreement for thoracic spine tomosynthesis was substantial (mean κ?=?0.73). ? Significantly more vertebrae and significantly more fractures were seen with tomosynthesis. ? Tomosynthesis took longer to evaluate than radiography. ? There was a clear preference among all observers for tomosynthesis over radiography.

     

XperSwing技术与常规冠状动脉造影的辐射剂量对比模体研究

目的 研究常规冠状动脉造影(CCA)与采用XperSwing技术冠状动脉造影的辐射剂量差异.方法 应用中国人仿真胸部体模,采用XperSwing和CCA2种检查技术,将热释光个人剂量计(TLD)布放于仿真胸部体模的主要组织器官,测量各组织器官的吸收剂量并读取设备的剂量面积乘积(DAP)值.实际测量有效剂量等于组织器官吸收剂量乘以相应组织权重因子后的总和;设备读取的有效剂量等于DAP乘以转换因子(0.185 mSv/ Gy·cm2).结果 采用XperSwing技术造影的组织器官平均吸收剂量低于CCA检查;CCA和XperSwing技术造影的设备读取平均有效剂量分别为3.88和3.13 mSv,低于实际测量的平均有效剂量(5.57和4.94 mSv).结论 采用XperSwing技术的辐射剂量低于CCA,设备读取的有效剂量有可能低估了患者实际接受的有效剂量水平.     

Effective Dose of CT- and Fluoroscopy-Guided Perineural/Epidural Injections of the Lumbar Spine: A Comparative Study

The objective of this study was to compare the effective radiation dose of perineural and epidural injections of the lumbar spine under computed tomography (CT) or fluoroscopic guidance with respect to dose-reduced protocols. We assessed the radiation dose with an Alderson Rando phantom at the lumbar segment L4/5 using 29 thermoluminescence dosimeters. Based on our clinical experience, 4–10 CT scans and 1-min fluoroscopy are appropriate. Effective doses were calculated for CT for a routine lumbar spine protocol and for maximum dose reduction; as well as for fluoroscopy in a continuous and a pulsed mode (3–15 pulses/s). Effective doses under CT guidance were 1.51 mSv for 4 scans and 3.53 mSv for 10 scans using a standard protocol and 0.22 mSv and 0.43 mSv for the low-dose protocol. In continuous mode, the effective doses ranged from 0.43 to 1.25 mSv for 1–3 min of fluoroscopy. Using 1 min of pulsed fluoroscopy, the effective dose was less than 0.1 mSv for 3 pulses/s. A consequent low-dose CT protocol reduces the effective dose compared to a standard lumbar spine protocol by more than 85%. The latter dose might be expected when applying about 1 min of continuous fluoroscopy for guidance. A pulsed mode further reduces the effective dose of fluoroscopy by 80–90%.     

数字摄影受检者辐射剂量调查

目的 了解数字摄影（DR）检查中受检者的辐射剂量水平,为数字放射摄影受检者指导水平的制定提供基础数据。方法 使用热释光剂量计TLD测量受检者不同部位、不同投照方向的入射体表剂量（ESD）;使用剂量面积乘积仪测量受检者不同部位、不同投照方向的剂量面积乘积（DAP）,并利用测量的DAP值,估算出有效剂量（E）。结果 同类检查中,kV和mAs的变化范围较大,不同部位DR检查中ESD、DAP和E的差别均具有统计学意义（F=33.47、24.68、43.19,P<0.05）。其中,ESD和DAP均以腰椎（LAT）最高,均数为4.62mGy/次和2.26Gy·cm²/次;E以腹部（AP）最高,均数为0.59mSv,高于腰椎（LAT）的0.31mSv。结论 DR在加强受检者放射防护最优化方面很有潜力,应尽快建立适合我国国民体质特征的数字放射摄影受检者辐射剂量的指导水平。     

我国X射线摄影程序受检者入射体表剂量调查结果与分析

目的 通过调查全国15个省市不同级别医疗机构使用数字和屏片设备开展X射线摄影时受检者的入射体表剂量（ESD）,为制定适合我国国民体质特征的X射线摄影诊断参考水平提供数据。方法 按照《医用辐射危害评价与控制技术研究》实施方案的要求,选择年龄在20~70岁的受检者,男性体重在55~80 kg,女性体重在50~70 kg;采用热释光探测器（TLD）测量不同X射线摄影程序中成人受检者ESD,每台设备同一体位患者应不少于10名受检者;测量部位包含头颅、胸部的后前位（PA）和侧位（LAT）,腹部、骨盆、腰椎、胸椎的前后位（AP）和腰椎、胸椎的LAT等。结果 共在全国15个省的342家医院调查了19 975例X射线摄影受检者,1 813台不同类型X射线摄影设备,包括屏片X射线摄影、计算机X射线摄影（CR）和直接数字化X射线摄影（DR）设备,对于这3种类型的设备,不同摄影体位时受检者ESD的平均值分别为头颅PA：1.75、1.90、1.15 mGy;头颅LAT：1.69、1.46、1.03 mGy;胸部PA：0.75、0.65、0.36 mGy;胸部LAT：1.81、1.26、0.88 mGy;腹部AP：4.37、3.77、2.15 mGy;骨盆AP：3.73、3.56、2.75 mGy;腰椎AP：5.49、5.84、4.17 mGy;腰椎LAT：12.01、9.37、6.82 mGy;胸椎AP：4.53、3.65、2.49 mGy;胸椎LAT：6.91、6.43、4.15 mGy。结论 不同照射部位X射线摄影致受检者ESD有较大的差异。DR设备致受检者的ESD均低于屏片设备;除胸椎AP外,DR设备致受检者ESD均低于CR设备。在所有检查部位中,CR和屏片设备所致受检者ESD的差异均无统计学意义。