新生儿头颅多层螺旋CT低剂量扫描的临床应用

目的：评价新生儿头颅多层螺旋CT低剂量扫描的临床价值。方法：选取头颅CT检查的新生儿80例,随机等分成2组,分别使用120kV、90mAs及120kV、260mAs各扫描40例。其余扫描参数为：准直1．5mm,层厚6mm,重建间隔6mm,床速11．7mm／r,扫描时间0．75s。分别比较2种扫描剂量产生的总mAs、CT权重剂量指数（CTDIw）及剂量长度乘积（DLP）,并作t检验。由3名医师采用盲法评价CT图像。按正常图像、图像有少许伪影、图像有严重伪影的等级对每帧图像进行质量评价,并进行统计学处理。结果：90mAs、260mAs组扫描的CTDIw分别为17．28mGy、49．85mGy,DPL分别为245mGy·cm、711mGy·cm。经t检验,90mAs组的CTDIw、DLP明显低于260mAs组（P〈0．01）。满足诊断需要的低剂量扫描图像所占比例（98．6％）与常规剂量扫描（99．9％）相比无显著差异（P〉0．05）。结论：新生儿头颅多层螺旋CT低剂量扫描的辐射剂量为常规剂量扫描的35％,而且图像不影响诊断,低剂量扫描适用于新生儿头颅CT检查。     

小儿头部多层螺旋CT检查的放射剂量评价

目的　评价小儿头部低剂量与常规剂量多层螺旋CT检查的放射剂量 ,为小儿头部多层螺旋CT检查提供扫描剂量参数。资料与方法　 (1)按年龄把 12 0例 0～ 6岁小儿分成 2组 ,患儿 <6个月 ,12 0kVp、90mAs扫描 30例 ;6个月～ 6岁 ,12 0kVp ,15 0mAs扫描 30例 ;常规扫描剂量为 12 0kVp、2 6 0mAs,依照上述年龄段各扫描 30例。其余扫描参数为 :准直 1.5mm ,层厚 6mm ,重建间隔 6mm ,床速 11.7mm/r,扫描时间 0 .75s。分别比较 2种扫描剂量产生的有效mAs、CT权重剂量指数 (weightedCTdoseindex ,CTDIw)及剂量长度乘积 (dose lengthproduct,DLP) ,并作 χ2检验。 (2 )由 3名医师盲法评价CT图像。按正常图像、图像有少许伪影、图像有严重伪影的等级对每帧图像进行质量评判 ,并进行统计学处理。结果　 (1)小儿各年龄段低剂量 (90mAs、15 0mAs)扫描的CTDIw为 17.2 8mGy、2 8.8mGy ,分别是常规剂量 (2 6 0mAs)扫描的 34.6 %、5 7.8% ;前者的DLP分别为 2 37mGy·cm、4 2 3mGy·cm ,明显低于后者的 6 83mGy·cm、731mGy·cm(P <0 .0 1)。 (2 ) 98%以上小儿头部低剂量CT图像可满足临床影像诊断需要 ,与常规剂量小儿头部图像相比无显著差异 (P >0 .0 5 )。结论　小儿头部低剂量多层螺旋CT扫描的辐射剂量为常规剂量扫描的 35     

肺部低剂量螺旋CT扫描的放射剂量评估

目的 :评价肺部低剂量与常规剂量螺旋CT扫描的X线放射剂量比 ,为低剂量螺旋CT普查早期肺癌提供扫描参数。方法 :将 80例的健康者自愿随机等分成 2组 ,40例行肺部低剂量螺旋CT扫描 ;40例行常规剂量螺旋CT扫描 ;扫描范围从肺尖至肺底。从CT扫描序列设定栏上 ,分别记录 2种扫描方式的权重CT剂量指数 (CTDIw )、扫描长度、总扫描时间 ;最后计算出 2种扫描方法的平均剂量长度乘积 (DLP)、毫安秒及X线放射剂量。结果 :肺部低剂量扫描的权重剂量指数为 2 .9mGY ,是常规剂量扫描 ( 11.7mGY)的 2 5 % ;低剂量扫描的剂量长度乘积 (DLP)为 63 .4mGY·cm明显低于常规剂量扫描 2 48mGY·cm(P <0 .0 0 1) ;低剂量扫描的毫安秒为 915mAs ,明显低于常规剂量扫描 3 5 2 1mAs(P <0 .0 0 1) ;低剂量扫描的放射剂量为 70 .8mGY ,是常规剂量扫描 ( 2 74.7mGY)的 2 6%。讨论 :肺低剂量螺旋CT扫描的放射剂量是常规剂量扫描的 2 6% ,适用于肺癌高危人群的早期普查。     

肺部低剂量螺旋CT放射剂量的研究

目的 :评价低剂量与常规剂量螺旋CT扫描的X线放射剂量比。方法 :对肺内结节用 2 0 0mAs行常规剂量螺旋CT扫描 ,扫描参数为 :12 0kV ,层厚 10mm ,扫描间隔 10mm ,螺距 1 5。选取不同层厚 (5mm、10mm)分别用 2 0 0mA、4 0mA、30mA、2 0mA、10mA扫描 ,记录各组每次扫描的单次CT剂量加权指数CTDIw(mGy)及mAs。对所有数据进行统计学处理 ,P <0 0 5时差异有统计学意义。结果 :2 0 0mA常规剂量组之CTDIW及毫安秒值与低剂量各组 (40mA、30mA、2 0、10mA)值比较差异有统计学意义 (P <0 0 5 ) ;以 2 0 0mAs常规剂量为标准 ,其余低剂量组 4 0mA ,30mA ,2 0mA ,10mA毫安秒及CTDIw分别降低了 80 %、90 %、95 %。结论 :用 2 0mAs低剂量螺旋CT扫描毫安秒及CTDIW仅仅相当于用 2 0 0mAs的 1/10 ,辐射剂量降低了 90 %。 2 0mA是肺部扫描的最佳剂量 ,具有辐射量小、敏感性强、性价比高的特点 ,值得推广应用。     

颞骨CT扫描方案对晶体剂量影响的研究

目的 探讨颞骨CT的不同扫描方式对眼晶体剂量的影响。方法 在相同管电压和有效mAs下,对成人离体头颅标本分别行横断位和冠状位的标准单层连续扫描、常规多层螺旋扫描以及改良的多层螺旋扫描。分析各种扫描方式的CT容积剂量指数(CTDI_vol)和剂量长度乘积(DLP),计算被检体有效剂量,并使用热释光剂量片测量晶体的器官剂量。结果 单层连续扫描时总体有效剂量为1.21 mSv,横断位扫描的晶体剂量为50.96 mGy,冠状位晶体剂量为1.73 mGy;常规多层螺旋扫描的有效剂量为0.803 mSv,晶体剂量为40.17 mGy;改良的多层螺旋扫描的有效剂量为0.803 mSv,晶体剂量为10.33 mGy。结论 相同管电压和有效mAs下,单层连续横断位和冠状位扫描的总体有效剂量和晶体剂量分别是常规螺旋扫描的1.51和1.31倍。改良的多层螺旋CT扫描方式可将螺旋扫描时的晶体剂量降低74.3%,可作为临床颞骨CT扫描的选择方式。     

低剂量CT扫描在肺部穿刺活检术中的应用价值

目的:讨论低剂量CT扫描在胸部穿刺活检术中应用的可行性及局限性.方法:回顾分析了2009年8月至2010年9月在16排CT引导下行胸部穿刺活检术患者共80例,其中常规剂量扫描A组(200mA,重建层厚2.0mm,螺距16mm/rot)和低剂量扫描B组(10mA,重建层厚2.0mm,螺距23mm/rot)的患者各40例,比较两组穿刺CT扫描剂量、图像质量和穿刺结果成功率以及并发症之间的关系.结果:常规剂量扫描组CT吸收剂量加权指数CTDIw和平均剂量长度乘积DLP分别为(23.64± 2.41) mGy和(172.37-± 17.63)mGy·cm,穿刺成功率为90％;低剂量扫描组CT吸收剂量加权指数CTDIw和平均剂量长度乘积DLP分别为(1.22±0.12)mGy和(8.56±0.88)mGy·cm,穿刺成功率为85％.两组的辐射剂量差异有统计学意义(P＜0.01),而穿刺成功率差异无统计学意义(P＞0.05),图像质量分级均能满足穿刺活检的需要,均未发现严重并发症.结论:采用低剂量CT扫描引导胸部穿刺活检是一种值得推荐的技术,可以大大降低辐射剂量.     

新生儿颅脑低剂量CT扫描参数研究

目的探讨新生儿颅脑低剂量CT扫描的最佳参数,降低扫描辐射剂量。方法选取颅脑CT检查的新生儿150例,随机等分成5组。扫描参数:管电压120kV,层厚、层间距6mm,管电流分别使用250、200、150、100、50mAs行全颅脑CT扫描,统一于左基底节层面测量各组CT值及标准差(SD)。对5组剂量扫描的CT剂量加权指数(CTDIw)、全头颅扫描剂量长度乘积(DLP)、噪声及图像质量对比分析。结果(1)随着扫描剂量的降低,CTDIw(mGy)及DLP值明显下降,50mAs组仅为常规剂量组的20%;(2)50mAs组扫描图像质量等级以较好和一般为主,100mAs及以上各组以好、较好为主,mAs降低,图像质量也下降;(3)50mAs组图像噪声较大,但颅内正常结构及病变组织显示尚清,且可通过调整窗宽和窗位,使图像质量得到提高,基本不影响诊断。结论50mAs低剂量新生儿颅脑扫描的图像质量有所下降,但不影响诊断,且由于辐射剂量显著降低,有效地保护了新生儿。     

16层螺旋CT低剂量扫描技术在儿童腺样体肥大中的应用

目的:探讨16层螺旋CT低剂量扫描技术在儿童腺样体肥大的临床应用。方法:对46例临床疑似腺样体肥大儿童行16层螺旋CT低剂量和常规剂量扫描,将其随机分为两组,对比两种剂量扫描的图像质量与患者的辐射剂量。结果:16层螺旋CT低剂量扫描与常规剂量扫描对显示鼻咽部的解剖结构及病变差异无显著性意义(P=0.381)。对低剂量组/常规剂量组两组腺样体CT值平均值之间无统计学差异(P=0.256)。CT值标准偏差之间无统计学差异(P=0.313)。低剂量CT扫描显示儿童鼻咽部扫描参数中CTDIvol为4.35mGy、DLP为40.62mGy.cm,常规剂量CTDIvol为8.65mGy、DLP为81.23mGy.cm。低剂量与常规剂量相比,其CTDIvol和DLP降低了约50%的辐射剂量。结论:16层螺旋CT低剂量扫描对腺样体肥大的诊断结果与常规剂量均相同,故16层螺旋CT低剂量扫描临床疑似腺样体肥大的患者,完全能替代常规剂量的16层螺旋CT扫描。     

64层螺旋CT低剂量扫描检测肺小结节敏感性的实验研究

目的 探讨64层螺旋CT胸部低剂量扫描对大小、密度不同肺小结节的检测敏感性及最优扫描参数. 方法 制作3组不同密度(软组织密度、较低密度、磨玻璃密度)、直径13～2.5 mm的人工肺结节,置于组织等效胸部模型中,使用Philips Brilliance 64层CT机以常规剂量(管电压120 kV,管电流250 mAs)和低剂量(管电压120 kV,管电流50、30 mAs和21 mAs)分别扫描.测量、记录剂量指标(CTDIw和DLP)、模型各部位CT值、CT值标准差,评估各组结节的可见度. 结果 64层螺旋CT采用低剂量扫描(21～50 mAs)的辐射剂量为常规剂量(250 mAs)的8%～20%.不同扫描剂量条件下模型各部位CT值差异无统计学意义(P>0.05);而CT值标准差差异有统计学意义(P<0.001)且随电流降低而增加.各组结节中仅2.5 mm和4 mm磨玻璃密度(-600 HU左右)结节在管电流21 mAs扫描时出现不可见情况. 结论 64层螺旋CT实验条件下30 mAs低剂量扫描最小直径2.5 mm磨玻璃密度结节,是最优扫描参数.     

CT引导肺部穿刺活检的低剂量参数优选及应用

目的:评价肺部不同扫描参数下的辐射剂量和图像质量,探讨低剂量扫描在CT引导下肺部穿刺活检中的应用价值。方法:①CT引导下肺部穿刺活检的患者30例(肺穿组),扫描参数为10 mA,120 kV,层厚5 mm,螺距1.5,床速15 mm/s;30例患者(对照组)行胸部常规智能自动毫安扫描,参数为30~175 mA,平均(82.0±13.5)mA,120 kV,层厚10 mm,螺距1.5,床速30 mm/s;②分别比较两种扫描参数下的CT权重剂量指数(CTDIw)和剂量长度乘积(DLP)、图像质量及总扫描帧数。结果:30例肺穿患者在10 mA低剂量扫描参数下全部穿刺成功。肺穿组的CTDIw和DLP分别为(15.9±8.4)mGy和(2.9±2.3)Gy.cm,明显低于对照组(P<0.01)。结论:采用10 mA低剂量扫描参数,不仅可以保证CT引导下肺部穿刺活检成功,而且能减少患者的受线量。     

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。     

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.     

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.     

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.     

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.     

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.     

数字乳腺X射线摄影中管电流量优化的实验研究

目的:探讨数字乳腺X射线摄影中不同靶/滤过组合时降低管电流量(mAs)对图像质量与辐射剂量的影响。方法:不同靶/滤过组合时,以自动曝光模式(AEC)的mAs为基础,分别降低10%、20%、30%、40%、50%时对厚度为4.4 cm的模体进行曝光,测量所得图像的对比噪声比(CNR)、信噪比(SNR)、品质因子(FOM)...