Patient dose increase caused by posteroanterior CT localizer radiographs

IntroductionThe aim of this study was to compare the output dose (volume CT dose index [ CTDI_vol], and dose length product [DLP]) of automatic tube current modulation (ATCM) determined by localizer radiographs obtained in the anteroposterior (AP) and posteroanterior (PA) directions.MethodsOne hundred and twenty-four patients who underwent upper abdomen and/or chest–to–pelvis computed tomography (CT) were included. Patients underwent two series of CT examinations, and localizer radiographs were obtained in the AP and PA directions. The horizontal diameter of the localizer radiograph, scan length, CTDI_vol, and DLP were measured.ResultsThere was no significant difference in the scan length; however, all the other values were significantly higher in the PA direction. The mean horizontal diameter was 33.1 ± 2.6 cm and 35.4 ± 2.9 cm in the AP and PA directions of the localizer radiographs, respectively. The CTDI_vol and DLP in the PA direction increased by approximately 7–8%.Bland-Altman plots between AP and PA localizer directions in upper abdominal CT showed a positive bias of 1.1 mGy and 30.0 mGy cm for CTDI_vol and DLP, respectively. Correspondingly, chest–to–pelvic CT showed a positive bias of 0.93 mGy and 69.3 mGy cm for CTDI_vol and DLP, respectively.ConclusionThe output dose of ATCM determined by localizer radiographs obtained in the PA direction was increased compared to the AP direction. Localizer radiographs obtained in the AP direction should be preferred for optimizing the output dose using ATCM.Implications for practiceBased on the evidence of this study, localizer radiographs obtained in the AP direction should be preferred for optimizing the output dose in CT examinations.     

Assessment of computed tomography radiation doses for paediatric head and chest examinations using paediatric phantoms of three different ages

IntroductionWith the rapid development of computed tomography (CT) scanners, the assessment of the radiation dose received by the patient has become a heavily researched topic and may result in a reduction in radiation exposure risk. In this study, radiation doses were measured using three paediatric phantoms for head and chest CT examinations in Najran, Saudi Arabia.MethodsThirteen scanners were included in the study to estimate the CT radiation doses using three phantoms representing three age groups (1-, 5-, and 10-year-old patients).ResultsThe volume CT dose index (CTDI_vol) estimated for each phantom ranged from 6.56 to 41.12 mGy and 0.292 to 11.10 mGy for the head and chest examinations, respectively. The estimation of lifetime attributable risk (LAR) indicated that the cancer risk could reach approximately 0.02–0.16% per 500 children undergoing head and chest CT examinations.ConclusionThe comparison with the published data of the European Commission (EC) and countries reported in this study revealed that the mean CTDI_vol for the head examinations was within the recommended dose reference levels (DRLs). Meanwhile, chest results exceeded the international DRLs for the one-year-old phantoms, suggesting that optimisation work is required at a number of sites.Implications for practiceThe variation among CT doses reported in this study showed that substantial standardisation is needed.     

Pregnancy and diagnostic X-rays

Diagnostic X-ray examinations are carried out in pregnant patients in clinical practice either accidentally or because of clinical urgency. In these cases, estimation of the risk to the conceptus is of paramount importance. The risk is dependent on the gestational age and the amount of radiation dose absorbed by the conceptus. Under normal operating conditions, conceptus doses from extra-abdominal examinations are lower than 1 mGy. In the case of examinations involving the abdomen or pelvis, doses to the embryo may be considerably higher in comparison with extra-abdominal examinations. In such cases, detailed assessment of dose to the conceptus is necessary. Doses to the unborn child below 100 mGy should not be considered a reason for termination of pregnancy. Counselling the pregnant patient regarding the risks of the diagnostic X-ray examination is essential. Deterministic effects have a threshold of 100 mGy or higher. This dose is higher than that expected from the overwhelming majority of the diagnostic X-ray examinations. As a result of radiation exposure, the conceptus is assumed to be at risk for stochastic effects, mainly childhood cancer, leukaemia and hereditary effects. The risk for radiation-induced childhood fatal cancer is about 6% per Gy. Risk estimates for genetic effects have been estimated to be about 1% per Gy. Pregnant workers are also exposed to diagnostic X-rays. The protection provided for the conceptus of the worker should be comparable to that of the general public (1 mGy) during the declared pregnancy. A radiation protection program for pregnant staff working at diagnostic radiology departments should be implemented to control conceptus exposure and assist the pregnant woman in obtaining the information necessary to continue her job safely.     

不同扫描中心结合自动管电流调制技术和自动管电压调制技术在CT扫描中对辐射剂量影响的模体研究

目的 探讨在应用自动管电流调制技术（ATCM）和自动管电压调制技术（CARE kV）行头颈部和胸部CT螺旋扫描时,不同扫描中心对辐射剂量的影响。方法 联合ATCM和CARE kV技术,对头颈部和胸部模体行CT螺旋扫描。头颈部模体选取眼球中心向上4 cm、眼球、眼球与外耳孔连线中点、外耳孔、外耳孔向下5 cm 5种不同的扫描中心（即不同检查床高度）,胸部模体选取乳腺向上5 cm和4 cm、乳腺、腋前线、腋中线、腋后线6种不同的扫描中心。每种扫描中心时定位像扫描3次,然后1次螺旋扫描。头颈部模体在眼眶中心及第5颈椎（C5）椎体上缘层面选取感兴趣区（ROI）,胸部模体在肺尖及气管分叉层面选取ROI,测量记录对比噪声比（CNR）。用热释光剂量计（TLD）测量每次扫描时眼晶状体和乳腺的器官剂量。记录每次扫描的容积CT剂量指数（CTDI_vol）。结果 头颈部模体5种不同扫描中心时,眼晶状体累积辐射剂量最高在眼球与外耳孔连线中点为中心（8.851 mGy）,CTDI_vol最高在外耳孔向下5 cm为中心（15.850 mGy）。眼晶状体累积辐射剂量最低在外耳孔向下5 cm为中心（7.096 mGy）,CTDI_vol最低在眼球、眼球与外耳孔连线中点、外耳孔为中心（均为15.380 mGy）。胸部模体6种不同扫描中心时,乳腺累积辐射剂量最高在乳腺为中心（6.467 mGy）,CTDI_vol最高在腋前线为中心（4.120 mGy）。腋后线为中心上述值最低（分别为4.794和3.540 mGy）。头颈部模体眼眶中心层面、C5椎体上缘层面的CNR分别为87.22~108.88和136.13~175.57;胸部模体肺尖层面、气管分叉处层面的CNR分别为75.19~116.92和42.85~86.78。结论 CT扫描中心的选择对CT扫描部位的辐射剂量,特别是对射线敏感的组织和器官的辐射剂量有很大影响。     

Dose reduction in CT while maintaining diagnostic confidence: diagnostic reference levels at routine head, chest, and abdominal CT--IAEA-coordinated research project

PURPOSE: To measure radiation doses for computed tomography (CT) of the head, chest, and abdomen and compare them with the diagnostic reference levels, as part of the International Atomic Energy Agency Research coordination project. MATERIALS AND METHODS: The local ethics committees of all participating institutions approved the study protocol. Written informed consent was obtained from all patients. All scanners were helical single-section or multi-detector row CT systems. Six hundred thirty-three patients undergoing head (n = 97), chest (n = 243), or abdominal (n = 293) CT were included. Collected data included patient height, weight, sex, and age; tube voltage and tube current-time product settings; pitch; section thickness; number of sections; weighted or volumetric CT dose index; and dose-length product (DLP). The effective dose was also estimated and served as collective dose estimation data. RESULTS: Mean volumetric CT dose index and DLP values were below the European diagnostic reference levels: 39 mGy and 544 mGy . cm, respectively, at head CT; 9.3 mGy and 348 mGy . cm, respectively, at chest CT; and 10.4 mGy and 549 mGy . cm, respectively, at abdominal CT. Estimated effective doses were 1.2, 5.9, and 8.2 mSv, respectively. CONCLUSION: Comparison of CT results with diagnostic reference levels revealed the need for revisions, partly because the newer scanners have improved technology that facilitates lower patient doses.     

Absorbed radiation dose of the female breast during diagnostic multidetector chest CT and dose reduction with a tungsten-antimony composite breast shield: preliminary results

AIM: To determine the absorbed radiation dose to the female breast during chest computed tomography (CT), and whether a custom-designed breast shield can reduce that dose. MATERIALS AND METHODS: Bilateral breast phantoms were combined with an anthropomorphic torso phantom. Each breast phantom contained 20 thermoluminescent dosimeter (TLD) cavities. Eight cavities were used per phantom. Absorbed radiation was measured using TLD 100 s. Three-stacked TLDs comprised a set. Three sets of three TLDs were positioned at eight designated locations and three depths (surface; 1 cm; 4 cm). One set of three TLDs was positioned at eight additional designations, 1cm deep. Each breast was divided anatomically into quadrants. In total, 32 TLD sets/96 TLDs were deployed. The breast-torso phantom was consecutively imaged using a 16-detector array CT machine. Subsequently, 32 new TLD sets were similarly placed, the phantom re-imaged in a likewise manner, but with the application of a tungsten-antimony composite breast shield. TLD readings were averaged and calculated. RESULTS: Average absorbed radiation doses for unshielded right and left breast phantoms ranged from 13.83-19.36 mGy, and 14-20.47 mGy, respectively. The absorbed dose in the shielded right and left breast was reduced to 6.64-8.12 mGy, and 6.7-8.03 mGy, respectively. Average absorbed radiation doses based on the depth for the unshielded breasts ranged from 15.4-18.3 mGy. Shielding reduced this dose to 7-7.9 mGy. Unshielded absorbed radiation doses based on anatomic quadrants ranged from 17.5-18.9 mGy. Shielding reduced this dose to 7-7.5 mGy. CONCLUSIONS: The average absorbed radiation dose to the unshielded female breast phantom is approximately 14-20 mGy. An externally applied shield can reduce this absorbed dose by 56-61%.     

儿童CT检查诊断参考水平典型值的初步探讨

目的统计以容积CT剂量指数(CTDI_(vol))、基于水当量直径(WD)的体型特异性剂量估算值(SSDEWD)及剂量长度乘积(DLP)为衡量指标的儿童头颅、胸部及腹盆部CT检查诊断参考水平(DRL)典型值,衡量本医疗机构CT检查辐射水平。方法回顾性收集2021年1月至2021年12月间南京医科大学附属儿童医院收治的头颅1391例,胸部1386例及腹盆部1035例患者CT影像资料,分别记录其年龄、CTDI_(vol)、DLP,手动测量最中间扫描图像的前后径(AP)、左右径(LAT)、兴趣区面积(AROI)及面积内CT值(CTROI),按照美国医学物理学家学会(AAPM)报告方法,计算有效直径(d)、WD、转换因子(f16/32XSIZE)及SSDEWD;将各检查部位分别按照年龄及体型进行分组:按照年龄分为<1、1~、5~、10~、15~岁5组,各分组患儿数分别为:头颅252、320、400、380及39例;胸部188、320、399、398及81例;腹盆部75、310、310、300及40例。头颅基于LAT分为<12.5、12.5~、14~、15~、16~cm 5组,每组患儿分别为151、222、319、399及300例;胸部、腹盆部基于d分为<15、15~、20~、25~、30~cm 5组,每组患儿分别为胸部275、527、400、165及19例;腹盆部403、410、184、34及4例。统计各分组内CTDI_(vol)、SSDEWD和DLP的第75百分位数,将其作为DRL典型值;并比较CTDI_(vol)和SSDEWD在衡量辐射剂量上的差异。结果按年龄分组,以CTDI_(vol)为衡量指标的头颅、胸部、腹盆部DRL典型值分别为14.9~24.1、1.8~4.5和2.0~7.5 mGy;以SSDEWD为衡量指标的DRL典型值分别为14.7~18.9、4.2~6.9和4.7~11.8 mGy;以DLP为衡量指标的DRL典型值分别为260~505、40~185和65~435 mGy·cm。按d分组,以CTDI_(vol)为衡量指标的胸部、腹盆部DRL典型值分别为1.8~6.8和2.2~9.2 mGy;以SSDEWD为衡量指标的DRL典型值分别为4.2~9.1和4.9~13.0 mGy;以DLP为衡量指标的DRL典型值分别为40~255和85~545 mGy·cm。头颅按LAT分组,以CTDI_(vol)为衡量指标的DRL典型值为14.1~23.1 mGy;以SSDEWD为衡量指标的DRL典型值为14.3~18.5 mGy;以DLP为衡量指标的DRL典型值为240~475 mGy·cm。头颅除年龄<1岁、LAT<12.5 cm分组外,CTDI_(vol)均大于SSDEWD,头颅CTDI_(vol)为(18.63±3.24)mGy,SSDEWD为(16.38±1.81)mGy,差异有统计学意义(t=48.78,P<0.001);胸部、腹盆部各分组CTDI_(vol)均小于SSDEWD,胸部CTDI_(vol)为(2.77±1.02)mGy,SSDEWD为(5.22±1.26)mGy,差异有统计学意义(t=-210.89,P<0.001);腹盆部CTDI_(vol)为(3.36±1.82)mGy,SSDEWD为(6.27±2.44)mGy,差异亦有统计学意义(t=-115.16,P<0.001)。结论本医疗机构DRL典型值与其他国家相比处于合理且较低水平,SSDEWD较CTDI_(vol)能更准确反映辐射剂量,亟需建立基于SSDEWD的DRLs。     

Brain radiotherapy during pregnancy: an analysis of conceptus dose using anthropomorphic phantoms.

The aims of this study were: (a) to determine conceptus dose resulting from brain radiotherapy; (b) to investigate the necessity of using shielding devices over patient's abdomen during treatment; and (c) to estimate the components of conceptus dose. Radiation doses received by conceptus were measured using anthropomorphic phantoms simulating pregnancy at 4, 12 and 24 weeks gestation and thermoluminescent dosemeters. All irradiations were performed with two lateral and opposed fields approximating the minimum, medium and maximum field size used during treatment of brain malignancies. For a treatment course delivering 65 Gy to tumour without using shielding equipment, conceptus dose never exceeded 100 mGy. Appropriate positioning of 5.1 cm of lead over the phantom's abdomen provided reduction of conceptus dose from 26% to 71%, depending upon gestational age, field size and distance from the field isocentre. The contribution of scatter arising from within the phantom to the conceptus dose was small compared with that from head leakage and collimator scatter. Our dosimetric results indicate that the construction of special shielding equipment is not a prerequisite for treating brain malignancies during pregnancy. However, based on the concept that exposures in women of childbearing age should be kept as low as reasonably achievable, we suggest that shielding devices should be used whenever possible.     

Bone marrow dose in chest radiography: the posteroanterior vs. anteroposterior projection.

The dose to active bone marrow resulting from anteroposterior (AP) and posteroanterior (PA) chest examinations was estimated using an Alderson Rando phantom and extruded lithium fluoride dosimeters. The AP projections resulted in a mean marrow dose range of 1.9-2.6 mrad (0.019-0.026 mGy) as compared to doses for PA projections of 3.4-3.8 mrad (0.034-0.038 mGy) for optimally diagnostic exposure taken at 70, 90, and 120 kVp.     

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。     

Impact of the introduction of 16-row MDCT on image quality and patient dose: phantom study and multi-centre survey

The purpose was to compare the image quality and patient dose between 4- and 16-row MDCT units and to evaluate the dispersion of the dose delivered for common clinical examinations. Four 4- and 16-row MDCT units were used in the study. Image noise levels from images of a CatPhan phantom were compared for all units using a given CTDI_vol of 15.0±1.0 mGy. Standard acquisition protocols from ten centres, shifted from 4- to 16-row MDCT (plus one additional centre for 16-row MDCT), were compared for cerebral angiography and standard chest and abdomen examinations. In addition, the protocols used with 16-row MDCT units for diagnosis of the unstable shoulder and for cardiac examinations were also compared. The introduction of 16-MSCT units did not reduce the performance of the detectors. Concerning the acquisition protocols, a wide range in practice was observed for standard examinations; DLP varied from 800 to 5,120 mGy.cm, 130 to 860 mGy.cm, 410 to 1,790 mGy.cm and 850 to 2,500 mGy.cm for cerebral angiography, standard chest, standard abdomen and heart examinations, respectively.The introduction of 16-row MDCT did not, on average, increase the patient dose for standard chest and abdominal examinations. However, a significant dose increase has been observed for cerebral angiography. There is a wide dispersion in the doses delivered, especially for cardiac imaging.     

Establishment of CT diagnostic reference levels (DRLs) for a Singapore healthcare cluster

IntroductionThe use of computed tomography (CT) in healthcare institutions has increased rapidly in recent years. The Singapore Health Services (SingHealth) cluster of healthcare institutions has taken the first step in establishing a local cluster-wide CT Diagnostic Reference Levels (DRL) in Singapore. CT dose data from each institution were collected through two primary dosimetry metrics: volume CT dose index (CTDI_vol measured in mGy) and dose-length product (DLP measured in mGy.cm).MethodsData from 19 CT scanners in seven institutions under one of Singapore healthcare cluster were retrospectively collected and analysed. The five common adult CT examinations analysed were CT Brain (non-contrast enhanced), CT Chest (IV contrast enhanced), CT Kidney-Ureter-Bladder (CT KUB, non-contrast enhanced), CT Pulmonary Angiogram (CT PA, IV contrast enhanced) and CT Abdomen-Pelvis (CT AP, IV contrast enhanced, single phase). Median CTDI_vol and DLP values for the five CT examinations from each institution were derived, with the cluster DRLs determined as the 75th percentile of the distribution of the institution median dose values.ResultsA total of 2413 dose data points were collected over a six-month period from June to November 2020. The cluster CT DRLs for the five CT examinations were determined to be 47 mGy and 820 mGy.cm for CT Brain, 5.4 mGy and 225 mGy.cm for CT Chest, 6.7 mGy and 248 mGy.cm for CT PA, 4.6 mGy and 190 mGy.cm for CT KUB and 6.9 mGy and 349 mGy.cm for CT AP.ConclusionThe establishment of the cluster CT DRLs provided individual institutions with a better understanding if their CT doses are unusually high or low, while emphasising that these DRLs are not meant as hard dose limits or constraints to follow strictly.     

Area beam equalization: optimization and performance of an automated prototype system for chest radiography

RATIONALE AND OBJECTIVES: To evaluate the feasibility and performance of an x-ray beam equalization system for chest radiography using anthropomorphic phantoms. MATERIALS AND METHODS: Area beam equalization involves the process of the initial unequalized image acquisition, attenuator thickness calculation, mask generation using a 16 x 16 piston array, and final equalized image acquisition. Chest radiographs of three different anthropomorphic phantoms were acquired with no beam equalization and equalization levels of 4.8, 11.3, and 21. Six radiologists evaluated the images by scoring them from 1-5 using 13 different criteria. The dose was calculated using the known attenuator material thickness and the mAs of the x-ray tube. RESULTS: The visibility of anatomic structures in the under-penetrated regions of the chest radiographs was shown to be significantly (P < .01) improved after beam equalization. An equalization level of 4.8 provided most of the improvements with moderate increases in patient dose and tube loading. Higher levels of beam equalization did not show much improvement in the visibility of anatomic structures in the under-penetrated regions. CONCLUSION: A moderate level of x-ray beam equalization in chest radiography is superior to both conventional radiographs and radiographs with high levels of beam equalization. X-ray beam equalization can significantly improve the visibility of anatomic structures in the under-penetrated regions while maintaining good image quality in the lung region.     

Estimation of fetal radiation dose from computed tomography scanning in late pregnancy: depth-dose data from routine examinations

RATIONALE AND OBJECTIVES: To provide depth-dose data for estimating fetal radiation dose from routine computed tomography (CT) examinations of the trunk. METHODS: Doses were measured during CT examinations of the thorax, upper abdomen, abdomen, and pelvis in two anthropomorphic phantoms simulating pregnant women in the second and third trimesters. Thermoluminescent dose meters were used for dose measurements. RESULTS: In CT examinations of the abdomen, doses of 30.0 to 43.6 mGy and of 29.1 to 42.0 mGy were measured at the measuring points in the phantom simulating pregnancy in the second and third trimesters, respectively. In CT examinations of the upper abdomen, pelvis, and thorax, both phantoms received lower doses of radiation. Knowledge of the normalized weighted dose index of the CT scanner and of the kVp and mAs settings of the protocol used for examination of the pregnant woman is needed to adjust the dose data found in the present study to modified protocols and different CT equipment. CONCLUSIONS: These dosimetric data may be used to guide the management of pregnant patients undergoing CT examinations of the trunk.     

成人胸部适当高电压数字X线摄影试验研究

目的 探讨成人胸部不同厚度高千伏DR的适当电压千伏值.方法 用不同厚度的聚甲基丙烯酸甲酯(PMMA)模拟不同成人胸部厚度,用不同电压、自动曝光控制(AEC)摄影,记录入射体表剂量(ESD)、获取模体影像并计算影像质量因子(IQF),绘制ESD和IQF之间的曲线.将一块厚度为1.8 cm(5 cm×5 cm)的PMMA作为对比物放在上述不同厚度PMMA上,用上述摄影方式和条件对其曝光,记录ESD,获取PMMA组合影像并计算信噪比(SNR)及影像质量因子倒数(IQFinv).结果 不同胸厚的ESD均随着摄影电压的上升而下降,不同胸厚影像的IQFinv和SNR也都随着摄影电压的上升而下降.当摄影电压分别是70、100、140 kV时,胸厚为17.5 cm的ESD分别为0.22、0.09、0.06 mGy,IQF分别为43.3、58.8、72.0,SNR分别为7.5、6.2、5.0;胸厚为22.5 cm的ESD分别为0.37、0.12、0.06 mGy,IQF分别为56.0、61.4、65.3,SNR分别为6.4、5.2、3.8;胸厚为27.0 cm的ESD分别为0.52、0.20、0.09 mGy,IQF分别为54.2、64.3、91.0,SNR分别为6.0、4.8、3.5;胸厚为31.5 cm的ESD分别为0.53、0.24、0.10 mGy,IQF分别为53.2、66.8、95.3,SNR分别为5.7、4.5、3.0.结论 胸部数字高千伏X线摄影对于不同体质、胸厚的受检者不应使用一个固定千伏值进行摄影,应根据具体情况选择不同的千伏值.     

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。     

宁夏成年人常见CT检查项目的辐射剂量状况调查研究

目的 调查宁夏地区成年人常见CT检查项目的辐射剂量现状,为建立宁夏成年人患者CT检查的第一个诊断参考水平提供依据。方法 采用分层整群抽样的方法,对宁夏地区不同规模医疗机构的不同品牌及型号CT扫描设备的使用情况及辐射状况进行调查,采用间隔抽样,获取被调查单位每日不同检查项目的扫描参数及辐射剂量值。登记医院、CT设备、检查项目、检查类型及患者的基本信息,记录各检查项目的CT扫描参数、CT剂量指数（CTDI_vol）和剂量长度乘积（DLP）值,计算患者的有效剂量E值;对所得数据按检查项目分组统计分析,并与其他国家推荐的诊断参考水平（DRL）值和辐射剂量状况进行比较。结果 调查宁夏地区45家医疗机构（公立三甲10家、公立三乙5家、公立二甲23家、民营医院5家、体检中心2家）6个生产品牌的58台CT设备,成年人患者4 952名。常见检查项目的CTDI_vol、DLP值及患者E值的第75百分位数值（P₇₅）为：头颅65.67 mGy、860.74 mGy ·cm、1.64 mSv;颈部29.32 mGy、490.00 mGy ·cm、2.83 mSv,颈部增强36.92 mGy、954.42 mGy ·cm、4.87 mSv;胸部11.50 mGy、382.06 mGy ·cm、5.68 mSv,胸部增强45.8 mGy、1 713.22 mGy ·cm、25.01 mSv;上腹部20.1 mGy、506.59 mGy ·cm、7.75 mSv,上腹部增强50.07 mGy、1 434.19 mGy ·cm、21.94 mSv;腹盆部14.33 mGy、670.78 mGy ·cm、10.26 mSv,腹盆部增强48 mGy、2 294 mGy ·cm、35.10 mSv;盆腔16.1 mGy、471.58 mGy ·cm、6.08 mSv,盆腔增强31.04 mGy、1 138.78 mGy ·cm、14.69 mSv。结论 宁夏地区头颅、颈部、胸部及盆腔CT辐射剂量较其他国家偏低或相差不大,而腹部CT辐射剂量明显高于其他国家,迫切需要对宁夏腹部CT扫描方案进行优化。     

CT radiation dose in children: a survey to establish age-based diagnostic reference levels in Switzerland

This work aimed at assessing the doses delivered in Switzerland to paediatric patients during computed tomography (CT) examinations of the brain, chest and abdomen, and at establishing diagnostic reference levels (DRLs) for various age groups. Forms were sent to the ten centres performing CT on children, addressing the demographics, the indication and the scanning parameters: number of series, kilovoltage, tube current, rotation time, reconstruction slice thickness and pitch, volume CT dose index (CTDI(vol)) and dose length product (DLP). Per age group, the proposed DRLs for brain, chest and abdomen are, respectively, in terms of CTDI(vol): 20, 30, 40, 60 mGy; 5, 8, 10, 12 mGy; 7, 9, 13, 16 mGy; and in terms of DLP: 270, 420, 560, 1,000 mGy cm; 110, 200, 220, 460 mGy cm; 130, 300, 380, 500 mGy cm. An optimisation process should be initiated to reduce the spread in dose recorded in this study. A major element of this process should be the use of DRLs.     

Application of European Commission reference dose levels in CT examinations in Crete, Greece

The purpose of this study was to apply European Commission reference dose levels (EC RDLs) to routine CT examinations. The dosimetric quantities proposed in the European Guidelines (EG) for CT are weighted computed tomography dose index (CTDI(w)) for a single slice and dose-length product (DLP) for a complete examination. Patient-related data as well as technical parameters for brain, chest, abdomen and pelvis examinations were collected for four CT scanners in the Euromedica Medical Center. Computed tomography dose index (CTDI) measurements were performed on each scanner and CTDI(w), DLP and effective dose E were estimated for each type of examination for a random sample of 10 typical patients. Mean values of CTDI(w) had a range of 27.0-52.0 mGy for brain and 13.9-26.9 mGy for chest, abdomen and pelvis examinations. Mean values of DLP had a range of 430-758 mGy cm for brain, 348-807 mGy cm for chest, 278-582 mGy cm for abdomen and 306-592 mGy cm for pelvis examinations. Mean values of E were 1.4 mSv for brain, 10.9 mSv for chest, 7.1 mSv for abdomen and 9.3 mSv for pelvis examinations. Results confirm that the Euromedica Medical Center meets EC RDLs for brain, abdomen and pelvis examinations, in terms of radiation dose and examination technique. As far as chest examination is concerned, although CTDI(w) of each scanner is within proposed values, the DLP is consistently exceeded, probably because of the large irradiation volume length L. It is anticipated that a reduction of L, or product mAs, or their combination, will reduce DLP without affecting image quality.