自动与固定管电压两种扫描方案对睾丸癌病人行标准胸腹部CT检查的对比研究

目的在降低放射剂量及满足影像质量前提下,对行胸腹部CT检查的睾丸癌病人进行前瞻性研究,以期确定最佳扫描方案。方法对40例睾丸癌病人进行胸部动静脉及腹部门静脉对比增强CT成像,在同一64层CT设备条件下采用两种扫描方案:A方案采用规定管电压(120kV)扫描。B方案采用自动化管电压(管电压80～140kV)。评估影像质量,记录放射剂量信息(CTDIvol)。结果 A方案在肝脏和脾影像噪声和衰减方面明显高于B方案(P<0.05),而在三角肌和竖脊肌影像方面两者相似。B扫描方案中,18例病人行胸部扫描,33例病人行腹部扫描,管电压降低到100kV,5例腹部扫描管电压降低至80kV;1例增加至140kV。两种CT扫描方案所得影像均满足诊断要求。同时使用CT协议。B方案放射剂量(CTDIvol)明显低于A方案(降低12%,P<0.01)。结论睾丸癌病人,采用自动管电压技术行胸腹部CT扫描能降低辐射剂量,同时保证影像质量。     

纤瘦成人256排探测器CT肝脏动态扫描的低对比剂和低辐射剂量方案:低管电压和混合迭代重建算法对影像质量的影响

摘要目的评估利用低管电压、混合迭代重建算法和256排探测器的腹部动态CT扫描低对比剂剂量和低辐射剂量方案与对影像质量的影响。方法本前瞻性研究获得机构审查委员会批准,且所有病人在实验前签署知情同意书。74例行肝动态CT扫描病人随机分配到以下两个方案之一中:39例病人行常规的120kV管电压扫描,而其他35例病人行80kV管电压和降低40%的对比剂剂量的扫描。80kV获得的影像通过混合迭代重建算法进行后处理。     

利用自动衰减为基础的管电压选择在心血管CT血管成像中降低辐射剂量和提高影像质量:个体内比较

目的评估自动管电压选择在心血管CT血管成像(CTA)检查中对辐射剂量和影像质量的影响。方法对72例病人[男41例,(60.5±16.5)岁]采用自动X线管电压选择算     

不同曝光模式对数字乳腺X线摄影影像质量和辐射剂量的影响

目的探讨数字乳腺X线摄影中不同曝光模式对影像质量及辐射剂量的影响,便于实际工作中在保证影像质量的前提下,通过对曝光模式及曝光条件选择有效降低病人的辐射损伤。方法先采用自动曝光模式(28kV、60mAs)对乳腺模体进行曝光,然后采用相同的压迫厚度和压力,根据自动曝光模式的摄影条件,在手动曝光模式下,分别固定管电压和管电流量,依次改变相应的管电流量及管电压对模体进行曝光,记录各曝光条件下入射剂量(ESD)、平均腺体剂量(AGD)和美国放射学会(ACR)标准的影像评分值。采用SPSS17.0软件中KruskalWallis检验对自动和手动曝光模式产生的各值进行统计学处理。结果手动曝光模式下,当管电压固定为28kV,管电流量由60mAs升至70mAs时,ESD和AGD分别增加了15.4%;当管电流量降至45mAs时,ESD和AGD分别降低了26.1%。当管电流量固定为60mAs,管电压由28kV升至32kV时,ESD和AGD分别增加了47.0%和62.7%;当管电压降至26kV时,ESD和AGD分别降低了22.6%和28.2%。不同曝光模式下影像的整体质量均无明显差别(P>0.05)。结论自动曝光模式下所得到的ESD与AGD均不是最低剂量。以自动曝光模式为基础,分别固定管电压或管电流量,在一定范围内分别手动降低管电流量或管电压值,在不影响影像质量的前提下,可降低辐射剂量。同时,影像质量达到一定水平后,不再随摄影条件增加而提高。     

对标准体型病人行低管电压CT肺动脉成像的可行性研究

目的通过对比低管电压CT肺动脉成像(CTPA)与常规CTPA的影像质量与辐射剂量,从而评价低管电压CTPA应用于标准体型病人的临床价值。方法前瞻性选取我院2013年2月—2014年8月标准体型(体质量指数≤25 kg/m2,体质量≤80 kg)病人60例,并随机分为2组。A、B两组管电压分别设置为80 k V和120 k V。管电流设置基于循环时间测试峰值。评价并对比A、B两组影像质量与辐射剂量,选取肺动脉干影像质量参数与辐射剂量进行Pearson相关性分析。结果 A组总体肺动脉CT值与噪声值高于B组,差异具有统计学意义(P=0.000)。A组总体肺动脉SNR和CNR与B组相比差异无统计学意义(分别P=0.187,P=0.309)。A组有效剂量显著低于B组[(1.69±0.43)m Sv∶(5.63±1.84)m Sv,P=0.000]。有效剂量与CT值和噪声值呈负相关。结论低管电压CTPA应用于标准体型病人可以有效减低辐射剂量,同时保证影像质量,具有临床应用价值。     

数字化胸部X线摄影在不同管电压下效果与其对受检者的影响

目的观察不同管电压下胸部数字X线摄影影像效果与其对受检者的影响。方法选择一种成人胸部模体为研究对象,用三种胸部数字X线的管电压80k V、100k V及120k V进行曝光。然后测量每种管电压下模体入射剂量、相对噪音值、对比度噪音比及有效剂量。结果自动曝光控制档位保持不动时,有效剂量及模体入射剂量均随着管电压的增加而逐渐减少。模体入射剂量与有效剂量呈正相关性。自动曝光控制档位保持不动时,相对噪音值会随着管电压的增加而逐渐减少,对比度噪音比会随着管电压的增加而逐渐增大。结论胸部数字X射线摄影时,在不影响影像质量的前提下为了减少受检患者的辐射剂量应尽量使用较高的管电压。     

评估腹部CT影像质量:采用基于模型的迭代重建可能减少的剂量

目的旨在通过对比滤过反投影法(FBP)和以3和5的特定强度为模型的基础算法(MBIR)重建的影像的视觉比较,估计腹部CT中可能减少的剂量。方法使用双能CT扫描获得3个分别来自50例招募病人的数据集,管电压分别为30%、70%和100%(平均CTDI_(vol)为1.9、3.4和6.2 m Gy)。5名放射科医师独立评估6个影像标准。可能减少的剂量采用视觉分级回归(VGR)估计。结果比较30%和70%管电压发现,在MBIR强度为3,使用强有效的管电压和图像重建方法且相对于FBP剂量减少24%~47%时,可以观察到影像质量显著改善(P0.001)。在MBIR强度为5时,对于影像标准1(肝实质),剂量无法减少,但是对于其他标准,剂量可以减少34%~74%。观察者间可信度显示71%~76%(κw0.201~0.286)的一致性,观察者内部可信度为82%~96%(κw0.525~0.783)的一致性。结论与FBP相比,MBIR能改善影像质量,除了其中一个影像标准外,其改善能力与MBIR强度、剂量减低的潜在可能性增加呈正相关。     

行肝脏对比增强CT时根据密度自动调整管电压和管电流调制以减少辐射剂量

目的回顾性分析联合应用自动调整管电压和自动管电流调制技术,与单独使用自动管电流调制比较,是否可在可接受的影像质量情况下降低肝脏对比增强CT的辐射剂量。材料与方法本研究经单位伦理委员会批准,无需知情同意书。怀疑肝脏疾病的314例病人,分成3组。其中2组应用自动调整管电压和自动管电流调制技术(A1组,n=97;A2组,n=101),但两组之间采用不同的对比增益设定;第3组,在固定管电压120kV条件下采用自动管电流调制技术(B组,n=116)。评价容积加权CT剂量指数与辐射距离乘积、对比噪声比和平均影像噪声。影像分析由2名具职业执照的放射科医师和1名放射科住院医师完成。统计分析采用单因素方差分析、双尾配对t检验、秩和检验和非劣效性检验。结果 A1和A2组较B组辐射剂量明显降低(P<0.0001)。A1组的辐射剂量平均降低20%,A2组降低31%。此外,A1和A2组的对比噪声比明显高于B组(P<0.0001)。尽管A1和A2组的影像噪声较高,但影像质量总体还是可以接受的。结论与单独采用自动管电流调制技术相比,联合应用自动调整管电压和自动管电流调制技术可在保证影像质量情况下,降低肝脏对比增强CT的检查辐射剂量。     

评价正弦波图形法迭代重建超低剂量胸部CT的影像质量

正摘要目的与低剂量CT(RDCT)对照,评价正弦波图形法迭代算法(SAFIRE)的超低剂量CT(ULDCT)的影像质量。方法 81例连续病人行ULDCT平扫,管电压80 kV、管电流     

自动管电压的选择对辐射剂量、影像质量及小儿腹部CT和CTA病灶检出率的影响的实验研究

正摘要目的探讨自动管电压选择对辐射剂量、影像质量及小儿腹部CT和CTA病灶检出的影响。方法儿科实验方法是使用常规螺距(1.4)和大螺距(3.0),应用标准的腹部CT扫描方法固定电压120 k V和自动管电压选择的变量电压、在非对比增强、对比增强及CTA模式检查方面进行对比。对于标准扫描方法和自动管电压选择检查方法在CT剂量、信     

Investigation of beam quality for digital chest radiography with RbBr:Tl(+) photostimulable storage phosphors

Beam quality for digital chest radiography in digital radiography systems (DR systems) with RbBr:Tl(+) photostimulable storage phosphors was investigated. Measurements of overall Wiener spectrum (overall WS) and observer performance experiments by means of Scheffé's method of paired comparisons were performed under the same exposure (5.16x10(-7)C/kg) at the X-ray detector of DR systems (sampling distance: 175 micro m, 2,048x2,048 pixels, 12 bits, look-up table: THX2) with a phantom lung and metacryl plates. Overall WS values were indicated to be inferior at higher tube voltages. All of the overall WS values were greater than those of screen film systems (HGM/UR1:S/F) at radiographic density 0.50, which was considered the density of the mediastinum and the area below the diaphragm (low density area), and at radiographic densities 1.00 and 1.50, considered as lung, WS values of S/F were located between the overall WS values of 80 kV and 100 kV, and 120 kV and 140 kV, respectively. Evaluation of visibility including mediastinum, lung, and total were indicated to be superior at the lower tube voltages. In evaluation of the mediastinum, the base image, which was obtained by 100 kV tube voltage (effective energy: 46.0 kV) in this study, was not significant from 90 kV to 110 kV tube voltages (range, +/-10 kV), and in-lung and total evaluations were not significant from 90 kV to 120 kV (range, -10 kV to +20 kV), and from 80 kV to 120 kV (range, +/-20 kV) tube voltages by 99% confidence interval. In conclusion, optimal beam quality for digital chest radiography with RbBr:Tl(+) photostimulable storage phosphors was considered to be less than 110 kV tube voltage (effective energy, 47.9 keV) in 0.1 mm copper and 3.8 mm aluminum total filtration. In this case, the granularity in low-density areas were inferior to those of S/F systems but nearly equal to the middle and high-density areas of chest images, and exposure dose was 14.3% lower than that of the base image obtained by 100 kV (effective energy, 46.0 keV) tube voltage in this study.     

Low-voltage digital selenium radiography: detection of simulated interstitial lung disease, nodules, and catheters--a phantom study

PURPOSE: To compare three tube voltages in digital selenium radiography for the detection of simulated interstitial lung disease, nodules, and catheters. MATERIALS AND METHODS: Simulated catheters, nodules, and ground-glass, linear, miliary, and reticular patterns were superimposed over an anthropomorphic chest phantom. Digital selenium radiography was performed with different tube voltages (70, 90, and 150 kVp). Hard-copy images were generated. Detection performance of five radiologists was compared by using receiver operating characteristic (ROC) analysis involving 54,000 observations. RESULTS: The detection of ground-glass, linear, miliary, and reticular patterns over lucent lung and of nodules equal to, smaller than, and larger than 10 mm increased when 70 kVp and/or 90 kVp was used. However, only the reticular pattern was significantly better detected at lower peak voltage (P <.05). Simulated catheters and nodules over the mediastinum showed smaller areas under the ROC curve at lower peak voltage. These results were not statistically significant (P >.05). CONCLUSION: The diagnostic performance of digital selenium radiography at lower peak voltage is at least as good as that at higher peak voltage for interstitial lung disease over lucent lung. Performance is equivalent for nodules and catheters over obscured chest regions at lower peak voltages compared with that at 150 kVp. Our results implicate that the use of high-voltage technique in digital selenium radiography should be reassessed.     

Investigation of optimum X-ray beam tube voltage and filtration for chest radiography with a computed radiography system

The purpose of this study was to determine the optimum tube voltage and amount of added copper (Cu) filtration for processed chest radiographs obtained with an Agfa 75.0 Computed Radiography (CR) system. The contrast-to-noise ratio (CNR) was measured in the lung, heart/spine and diaphragm compartments of a validated chest phantom using various tube voltages and amounts of Cu filtration. The CNR was derived as a function of air kerma at the CR plate and with the effective dose. As rib contrast can interfere with detection of nodules in chest radiography, a tissue-to-rib ratio (TRR) was derived to investigate which tube voltages suppress the contrast of rib. Although processing algorithms affect the signal and noise in a way that is hard to predict, we found that, for a given set of processing parameters, the CNR was related to the plate air kerma and effective dose in a logarithmic manner (all R(2) >or=0.97). For imaging of the lung region, a low voltage (60 kVp) produced the highest CNR, whereas a high voltage (125 kVp) produced the highest TRR. In the heart/spine region, 80-125 kVp produced the highest CNR, while in the diaphragm region 60-90 kVp produced the highest CNR. For chest radiography with this CR system, the optimal tube voltage depends upon the region of interest. Of the filters tested, a 0.1 mm Cu thickness was found to provide a statistically significant increase in the CNR in the diaphragm region with tube potentials of 60 kVp and 80 kVp, without affecting the CNR in the other anatomical compartments.     

Detector for dual-energy digital radiography

A detection scheme is described that allows one to accomplish dual-energy scanned projection digital radiography without switching the x-ray tube voltage. The method employs a high/low atomic number detector sandwich that simultaneously separates the x-ray beam transmitted by the patient into low and high energy components. To test the method, the response of a scanning linear array of energy-sensitive detectors was simulated, and bone and soft tissue images of an anthropomorphic chest phantom were obtained at 140 kVp. These were compared with similar images obtained by switching the x-ray tube voltage from 80 kVp to a heavily filtered 140 kVp. For comparable entrance skin exposures, the dual-energy detector images required a lower tube load and resulted in higher noise levels. The latter is attributable to the fact that the separation in energy between the high and low energy components is smaller with the dual-energy detector than with the voltage switching technique, and to misregistration problems associated with the simulation methodology. A detector design is also discussed that would result in improved energy separation and lower noise levels. In view of this possibility and the tube loading advantage, the method looks promising for digital scanned projection radiography.     

Experimental and theoretical assessment of the performance of Gd2O2S:Tb and La2O2S:Tb phosphors and Gd2O2S:Tb–La2O2S:Tb mixtures for X-ray imaging

The purpose of this work was to investigate and compare the imaging performance of Gd2O2S:Tb and La2O2S:Tb phosphors as well as of Gd2O2S:Tb and La2O2S:Tb mixtures for use in X-ray imaging detectors (intensifying screens). Phosphors were supplied in powder form and were used to prepare test screens. Three types of screens were prepared: Gd2O2S:Tb; (Gd50La50)O2S:Tb; and La2O2S:Tb. Screens were excited by X-rays with tube voltages from 40 to 120 kV and their efficiency (light intensity or light energy flux over exposure) was measured with a photomultiplier and a dosimeter. The light spectrum was also measured with a monochromator. From these measurements, the number of emitted photons per incident X-ray (NEP) and the zero frequency detective quantum efficiency (DQE(0)) of the screens were determined. Additionally, modulation transfer function (MTF) was measured by the square wave response function (SWRF) method. A theoretical model calculating NEP and DQE was also developed to fit experimental data and predict the performance of Gd2O2S:Tb-La2O2S:Tb mixtures by weight from 10-90% to 90-10%. Gd2O2S:Tb screens exhibited highest NEP, DQE, and MTF at tube voltages higher than 55 kV and lower than 45 kV, whereas La2O2S:Tb screens had better NEP, DQE, and MTF within the 45- to 55-kV range. Maximum NEP values were higher than 700 at 100-120 kV while maximum DQE(0) was 0.314 at 80 kV. Gd2O2S:Tb screens are more efficient for high X-ray tube voltage applications (e.g., abdominal imaging, chest radiography, lumbar spine radiography, CT) and for very low voltage applications (e.g., mammography). La2O2S:Tb screens are useful for medium-range X-ray voltages (e.g., pediatric radiography).     

上气道DR管电压与辐射剂量和图像质量的关系

目的 探讨成人上气道DR管电压选择与辐射剂量和图像质量的关系.方法 用聚甲基丙烯酸甲酯( PM MA)模拟成人上气道厚度和对比度细节体模(CDRAD2.O)组合,以不同管电压自动曝光控制系统(AEC)摄影,记录入射体表剂量(ESD)、剂量面积乘积(DAP)和曝光量(mAs),计算体模图像质量因子(IQF值),选定适宜管电压.结果 ESD、DAP、mAs随着管电压升高而下降,IQF值却增大,其间差异有统计学意义(F =45.15、26.41、29.26、56.53,P＜0.05).75 kV以下ESD、DAP、mAs明显增大,75 kV以上逐渐降低,75～80 kV趋于平衡.50～75 kV之间IQF值差异无统计学意义,75～90 kV之间IQF值差异有统计学意义(F=11.35,P＜0.05).不同管电压的正常人体上气道的图像质量无明显差异.结论 成人上气道DR的适宜管电压范围为75～80 kV,用IQF值对照图像质量评分可为临床评价图像质量提供依据.     

Dose-image quality study in digital chest radiography using Monte Carlo simulation.

One of the main preoccupations of diagnostic radiology is to guarantee a good image-sparing dose to the patient. In the present study, Monte Carlo simulations, with MCNPX code, coupled with an adult voxel female model (FAX) were performed to investigate how image quality and dose in digital chest radiography vary with tube voltage (80-150 kV) using air-gap technique and a computed radiography system. Calculated quantities were normalized to a fixed value of entrance skin exposure (ESE) of 0.0136 R. The results of the present analysis show that the image quality for chest radiography with imaging plate is improved and the dose reduced at lower tube voltage.     

碘化铯/非晶硅数字摄影系统拍摄胸片的适宜管电压:高千伏摄影是否适用于间接DR

目的探索碘化铯/非晶硅数字摄影系统(间接DR)拍摄胸片的适宜管电压。方法(1)分别对60名正常成人拍摄80、100、150 kV正位胸片,由5位放射科医师对比每人的3张图像质量,对多个解剖部位的显示情况和图像总体印象进行评分;(2)分别固定表面入射剂量和出射剂量,对人胸部体模拍摄80、100、120、150 kV正位胸片,对肺内模拟病变进行评分。结果成人胸片和肺内模拟病变的显示均随管电压增高,图像质量降低;80 kV对比度最好,但外观略接近低千伏摄影胸片。结论间接DR拍摄正位胸片的适宜管电压为80~100 kV,高千伏摄影不再适用于DR。     

Ambient dose during intraoral radiography with current techniques: part 3: effect of tube voltage

Objectives:This study was conducted to assess the impact of tube voltage on ambient dose during intraoral radiography, specifically remnant-beam transmission and scattered radiation.Methods and materials:Remnant-beam and scattered radiation doses were recorded using a phantom at tube voltages of 60, 63, 66 and 70 kV. Mathematical equations depicting their relations were then formulated, and reference values were calculated at the various voltages tested. Total ambient doses per exposure at 60 kV and at 70 kV were compared.Results:Both remnant-beam transmission and scattered radiation increased ~40% by increasing tube voltage from 60 kV to 70 kV, and the relation was linear. A remnant beam transmission reference value of 7.5% was established at 70 kV, as well as a conversion factor of 0.035 µSv/mAs at 1 m for scattered radiation at 60 kV. Given longer exposure times at 60 kV, total ambient dose proved higher at 60 kV than at 70 kV.Conclusion:Higher tube voltage results in higher remnant-beam transmission and more scattered radiation per workload. The relation is linear in the range between 60kV and 70 kV. Remnant-beam transmission at 70 kV is safely assessed at 7.5%. A conversion factor at 60 kV of 0.035 µSv/mAs at 1 m for the scattered radiation dose can be proposed. Total ambient dose per exposure was higher at 60kV than at 70 kV.     

Must radiation dose for CT of the maxilla and mandible be higher than that for conventional panoramic radiography?

We evaluated the feasibility of performing preoperative spiral CT of the maxilla and mandible with a radiation dose similar to that used for conventional panoramic radiography. The skin entrance doses of radiation used for spiral CT (collimation, 1 mm; pitch, 2; tube voltage, 80 kV; tube current, 40 mA) and for panoramic radiography (75 kV, 8 mA, 15 seconds) were measured in one patient by using thermoluminescent dosimeter chips. Results were 0.56 +/- 0.06 mGy for CT and 0.59 +/- 0.04 mGy for radiography. Image quality was adequate for preoperative implant planning. Spiral CT of the mandible and maxilla may therefore be feasible with a radiation dose of similar magnitude as that used for conventional panoramic radiography.