Optimisation of radiation dose and image quality in mobile neonatal chest radiography

PurposeTo optimise the radiation dose and image quality for chest radiography in the neonatal intensive care unit (NICU) by increasing the mean beam energy.MethodsTwo techniques for the acquisition of NICU AP chest X-ray images were compared for image quality and radiation dose. 73 images were acquired using a standard technique (56 kV, 3.2 mAs and no additional filtration) and 90 images with a new technique (62 kV, 2 mAs and 2 mm Al filtration). The entrance surface air kerma (ESAK) was measured using a phantom and compared between the techniques and against established diagnostic reference levels (DRL). Images were evaluated using seven image quality criteria independently by three radiologists. Images quality and radiation dose were compared statistically between the standard and new techniques.ResultsThe maximum ESAK for the new technique was 40.20 μGy, 43.7% of the ESAK of the standard technique. Statistical evaluation demonstrated no significant differences in image quality between the two acquisition techniques.ConclusionsBased on the techniques and acquisition factors investigated within this study, it is possible to lower the radiation dose without any significant effects on image quality by adding filtration (2 mm Al) and increasing the tube potential. Such steps are relatively simple to undertake and as such, other departments should consider testing and implementing this dose reduction strategy within clinical practice where appropriate.     

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。     

Direct detector radiography versus dual reading computed radiography: feasibility of dose reduction in chest radiography

The image quality of dual-reading computed radiography and dose-reduced direct radiography of the chest was compared in a clinical setting. The study group consisted of 50 patients that underwent three posteroanterior chest radiographs within minutes, one image obtained with a dual read-out computed radiography system (CR; Fuji 5501) at regular dose and two images with a flat panel direct detector unit (DR; Diagnost, Philips). The DR images were obtained with the same and with 50% of the dose used for the CR images. Images were evaluated in a blinded side-by-side comparison. Eight radiologists ranked the visually perceivable difference in image quality using a three-point scale. Then, three radiologists scored the visibility of anatomic landmarks in low and high attenuation areas and image noise. Statistical analysis was based on Friedman tests and Wilcoxon rank sum tests at a significance level of P<0.05. DR was judged superior to CR for the delineation of structures in high attenuation areas of the mediastinum even when obtained with 50% less dose (P<0.001). The visibility of most pulmonary structures was judged equivalent with both techniques, regardless of acquisition dose and speed level. Scores for image noise were lower for DR compared with CR, with the exception of DR obtained at a reduced dose. Thus, in this clinical preference study, DR was equivalent or even superior to the most modern dual read-out CR, even when obtained with 50% dose. A further dose reduction does not appear to be feasible for DR without significant loss of image quality.     

非晶硒平板探测器DR与CR模拟病变描述和剂量降低的对比研究

目的 比较非晶硒平板探测器DR与CR对模拟肺部病变的描述,并对剂量降低情况进行评价。方法 模拟线状、网状和结节病变结构置入仿真胸部体模内,应用DR和CR分别对不同mAs设置的体模曝光,记录体模的入射体表剂量。收集不同剂量的硬拷贝照片,由4位放射医师随机地实施模拟肺部病变显示度评价。采用秩和(Wilcoxon)检验进行统计学分析。结果 用2.0、3.2 mAs曝光时,DR与CR对模拟线状、网状病变的显示度差异有统计学意义(模拟线状病变:Z=-2.032,P=0.042;Z=-2.375, P=0.018。模拟网状病变: Z=-2.680, P=0.007;Z=-2.670, P=0.008)。用5.0、6.3 mAs曝光时,两者对模拟线状、网状病变的显示度差异无统计学意义(P＞0.05)。2.0、3.2、5.0、6.3 mAs曝光档,对于小结节(直径小于10 mm)的检测DR均优于CR(Z=-2.237, P=0.018; Z=-2.384, P=0.017; Z=-2.388, P=0.017; Z=-2.366, P=0.018)。当3种模拟肺部病变都显示清楚时,用非晶硒DR系统的入射体表剂量降低约65%。结论 对微小低对比病变的描述,非晶硒平板探测器DR优于CR且明显地降低曝光剂量。     

Dose and perceived image quality in chest radiography

Chest radiography is the most commonly performed diagnostic X-ray examination. The radiation dose to the patient for this examination is relatively low but because of its frequent use, the contribution to the collective dose is considerable. Consequently, optimization of dose and image quality offers a challenging area of research. In this article studies on dose reduction, different detector technologies, optimization of image acquisition and new technical developments in image acquisition and post processing will be reviewed.Studies indicate that dose reduction in PA chest images to at least 50% of commonly applied dose levels does not affect diagnosis in the lung fields; however, dose reduction in the mediastinum, upper abdomen and retrocardiac areas appears to directly deteriorate diagnosis. In addition to patient dose, also the design of the various digital detectors seems to have an effect on image quality. With respect to image acquisition, studies showed that using a lower tube voltage improves visibility of anatomical structures and lesions in digital chest radiographs but also increases the disturbing appearance of ribs.New techniques that are currently being evaluated are dual energy, tomosynthesis, temporal subtraction and rib suppression. These technologies may improve diagnostic chest X-ray further. They may for example reduce the negative influence of over projection of ribs, referred to as anatomic noise. In chest X-ray this type of noise may be the dominating factor in the detection of nodules. In conclusion, optimization and new developments will enlarge the value of chest X-ray as a mainstay in the diagnosis of chest diseases.     

Neonatal chest radiography: Influence of standard clinical protocols and radiographic equipment on pathology visibility and radiation dose using a neonatal chest phantom

IntroductionLittle is known about the variations in pathology visibility (PV) and their corresponding radiation dose values for neonatal chest radiography, between and within hospitals. Large variations in PV could influence the diagnostic outcome and the variations in radiation dose could affect the risk to patients. The aim of this study is to compare the PV and radiation dose for standard neonatal chest radiography protocols among a series of public hospitals.MethodsA Gammex 610 neonatal chest phantom was used to simulate the chest region of neonates. Radiographic acquisitions were conducted on 17 X-ray machines located in eight hospitals, utilising their current neonatal chest radiography protocols. Six qualified radiographers assessed PV visually using a relative visual grading analysis (VGA). Signal to noise ratios (SNR) and contrast to noise ratios (CNR) were measured as a measure of image quality (IQ). Incident air kerma (IAK) was measured using a solid-state dosimeter.ResultsPV and radiation dose varied substantially between and within hospitals. For PV, the mean (range) VGA scores, between and within the hospitals, were 2.69 (2.00–3.50) and 2.73 (2.33–3.33), respectively. For IAK, the mean (range), between and within the hospitals, were 24.45 (8.11–49.94) μGy and 34.86 (22.26–49.94) μGy, respectively.ConclusionBetween and within participating hospitals there was wide variation in the visibility of simulated pathology and radiation dose (IAK).Implications for practiceX-ray units with lower PV and higher doses require optimisation of their standard clinical protocols. Institutions which can offer acceptable levels of PV but with lower radiation doses should help facilitate national optimisation processes.     

双定位像结合Care Dose 4D和Care kV技术在降低肺部CT辐射剂量的临床应用价值

目的 探讨双定位像结合Care Dose 4D和Care kV技术在肺部CT检查中的可行性及其临床应用价值。方法 连续纳入临床确诊为肺部肿瘤行肺部CT扫描的患者60例,按随机数表法分为对照组和试验组,每组各30例,对照组行单定位像（AP）结合Care Dose 4D和Care kV技术扫描,试验组行双定位像（AP和lat）结合Care Dose 4D和Care kV技术扫描。由2位高年资医师采用双盲法对两组图像和病变组织的信噪比（SNR）、对比噪声比（CNR）,及整体图像质量进行综合分析和评价,同时计算有效辐射剂量。结果 60例患者均成功完成肺部CT检查,试验组整体图像质量评分为4.57±0.45,与对照组的4.73±0.45相比差异无统计学意义（P>0.05）。对照组图像SNR、CNR、病变组织SNR、CNR与试验组相比差异均无统计学意义（P>0.05）。试验组和对照组的容积CT剂量指数CTDI_vol、剂量长度乘积（DLP）、有效剂量（E）,差异有统计学意义（t=8.514、8.464、8.464,P<0.001）。与对照组相比,试验组有效剂量降低了33.3%。结论 较单定位像（AP）肺部CT检查,双定位像（AP和lat）结合Care Dose 4D和Care kV技术肺部CT检查可获得满足诊断及临床需求图像,同时明显降低辐射剂量,可成为肺部CT常规检查方式。     

Digital radiography: The balance between image quality and required radiation dose

Although the transition from conventional screen-film imaging to digital image acquisition has been almost completed during the last couple of years, examination parameters, such as tube voltage, tube current, and filtration have been adopted from screen-film technology without further adjustments.Digital systems, however, are characterised by their flexibility: the acquisition dose can be reduced at the expense of image quality and vice versa. The imaging parameters must be optimised according to the best performance of a particular system. The traditional means of dose containment, such as positioning and collimation, are as valid for digital techniques as they were for conventional techniques. Digital techniques increasingly offer options for dose reduction. At the same time, there is a risk of substantially increasing the patient dose, possibly unawares, due to the lack of visual control. Therefore, implementation of dose indicators and dose monitoring is mandatory for digital radiography. The use of image quality classes according to the dose requirements of given clinical indications are a further step toward modern radiation protection.     

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。     

Digital chest radiography: an update on modern technology,dose containment and control of image quality

The introduction of digital radiography not only has revolutionized communication between radiologists and clinicians, but also has improved image quality and allowed for further reduction of patient exposure. However, digital radiography also poses risks, such as unnoticed increases in patient dose and suboptimum image processing that may lead to suppression of diagnostic information. Advanced processing techniques, such as temporal subtraction, dual-energy subtraction and computer-aided detection (CAD) will play an increasing role in the future and are all targeted to decrease the influence of distracting anatomic background structures and to ease the detection of focal and subtle lesions. This review summarizes the most recent technical developments with regard to new detector techniques, options for dose reduction and optimized image processing. It explains the meaning of the exposure indicator or the dose reference level as tools for the radiologist to control the dose. It also provides an overview over the multitude of studies conducted in recent years to evaluate the options of these new developments to realize the principle of ALARA. The focus of the review is hereby on adult applications, the relationship between dose and image quality and the differences between the various detector systems.     

探讨胸部正侧位定位像在CT CARE Dose 4D技术中降低成人患者辐射剂量的临床价值

目的 探讨胸部正侧位定位像在CT CARE Dose 4D技术中进一步降低成人患者辐射剂量的应用价值和意义。方法 选取胸部CT平扫病例120例,按随机数字表法分为两组,每组60例;试验组使用胸部正侧位定位像定位,对照组使用正位定位像定位,两组均使用CARE Dose 4D技术扫描;记录两组病例的CTDI_vol、DLP及图像噪声,同时由2位医师按双盲法对两组病例图像质量行5分制评分;比较两组病例的CTDI_vol、DLP、图像噪声的差异,对两位医师主观评分进行χ²检验,并用Kappa检验,检验两位医生主观评价结果上的一致性。结果 试验组和对照组病例的平均CTDI_vol和DLP分别为(5.11±0.87)、(6.56±1.74)mGy和(159.58±30.65)、(211.5±65.89)mGy·cm,差异有统计学意义(t=-5.75、-5.88,P<0.05);胸锁关节、气管分叉、左心室水平图像平均噪声值:试验组为12.6±1.8、10.9±1.4、11.1±1.8,对照组为11.5±1.7、10.5±1.6、10.9±1.9,其中在胸锁关节水平两组图噪声值差异有统计学意义(t=5.03,P<0.05),气管分叉、左心室水平噪声差异无统计学意义(P>0.05)。两组病例主观图像质量评分均达到临床诊断要求,2名医师的评估结果一致(χ²=1.37,P>0.05)。结论 成人胸部CT扫描在CARE Dose 4D技术下,通过使用正侧位定位像可以在保证图像质量的同时,进一步降低患者辐射剂量,对临床有一定的应用价值。     

Assessment of the efficiency of new bismuth composite shields in radiation dose decline to breast during chest CT

Background

Bismuth shield has been recently introduced for radiation protection of patient radiosensitive organs such as breast during chest CT with image diagnosis capability. The purpose of this study was to evaluate the dose reduction and image quality conserve using new bismuth-silicon composite shields during chest CT.

A comparison of effective dose and risk for different collimation options used in AP shoulder radiography

IntroductionRadiography forms the cornerstone of the evaluation of shoulder disorders. While the benefits of radiography exceed the risks, there continues to be a compelling case for reduction of radiation exposure from diagnostic radiography. The aim of this project was to evaluate the radiation dose and risk for a variety of collimation settings used during anteroposterior (AP) shoulder radiography.MethodsThis was a phantom based study where an ATOM adult dosimetry phantom was loaded with 272 thermoluminescent dosimeters (TLDs). Following loading, the phantom was setup for an AP shoulder X-ray projection with standard 25 × 30 cm rectangular collimation. The phantom was exposed three times and then the TLDs were removed and read. The experiment was repeated using a diamond shaped collimation and rectangular collimation with a minimum field of view to portray only relevant anatomy. Using the TLD dose measurements the effective doses and radiation risks were determined and compared.ResultsAs expected, organs neighbouring the shoulder experienced the highest absorbed doses (greater than 0.01 mGy); these organs included breast, lung and thyroid gland. The effective doses for standard rectangular, small rectangular and diamond collimation were 0.011, 0.008 and 0.016 mSv, respectively. When compared to standard collimation, a small field of view reduced effective dose by 27.3% and when moving to a diamond shape there was a 45.5% increase. The differences are likely driven by differences in the coverage of the radiosensitive lung and breast tissue.ConclusionBy utilising a variety of different collimation settings, effective dose can be reduced. Reducing the radiation dose is both financially beneficial and results in a lower stochastic risk for patients. Image quality must also be considered when choosing different collimation settings. It stands to reason that by reducing the field size, dose will be reduced, and our study has served to quantify the effects in a practical situation.Implications for practiceThe utilisation of smaller/tight collimation is recommended as it offers the lowest dose when compared with other types of collimations. Although well-known this study serves to remind practitioners of the practical importance of collimation and is associated effect on effective dose and risk.     

对儿童X线体检中减少照射剂量的探讨

目的:探讨儿童在X线体检中减少照射剂量的方法。方法:应用东芝500mA遥控X线机、FJ-427型热释光剂量仪等设备,对100名3~5岁儿童体检时,随机分成两个对照组、每组50名,分别接受胸透或平片检查,对检查测得数据均进行统计学处理。结果:胸透时胸部接受的照射剂量是平片的22倍多,其它部位接受的X线散射剂量平均值之比亦在20~30倍之间。结论:在儿童X线体检中应采用常规胸片替代胸透,可以有效地降低其辐射危害。     

智能最佳管电压技术降低胸部CT辐射剂量的前瞻性研究

目的 探讨智能最佳kV（CARE kV）技术在成人胸部CT成像的应用及其对降低辐射剂量的价值。方法 将69例患者按随机数字表法分成A、B两组,A组39例,行CARE kV技术扫描;B组30例,行标准120 kV技术扫描。比较两组CT剂量指数（CTDI_vol）、剂量长度乘积（DLP）和有效剂量（E）以及分析A组管电压的选择与体重指数（BMI）关系。结果 A组平均CTDI_vol（11.00±3.89）mGy、DLP（294.05±91.17）mGy·cm及E（4.12±1.28）mSv分别低于B组（16.64±1.20）mGy、（475.99±41.16）mGy·cm、（6.66±0.58）mSv（t=-7.653、-10.151、-10.150,P<0.05）,与B组比较,A组总体E降低了38.14%。A组实际使用电压范围80~140 kV,管电压的选择与患者BMI呈正相关（r=0.627,P<0.05）。A组中非肥胖组患者E较肥胖组（BMI≥28 kg/m²）减少了31.74%（t=4.322,P<0.05）,而B组中非肥胖组患者E与肥胖组患者差异无统计学意义。结论 胸部CT成像中,CARE kV技术能够根据患者体型和解剖部位的不同而自动地选择管电压和调整管电流,从而能够在保证图像诊断质量的同时显著降低总体辐射剂量。     

不同摄影源像距对小儿胸部数字X线技术辐射剂量图像质量的影响

目的不同摄影源像距对小儿胸部数字X线技术(DR)辐射剂量、图像质量的影响。方法选取我院2017至2018年收治的60例行胸部X线(DR)检查的患儿为研究对象开展回顾性分析,首先进行体模预实验曝光,采用同一管电压和不同摄影源像距(SID)(80~150 cm),其中10 cm为1组,记录每次曝光的毫安秒和入射体表剂量(ESD)。选取体模预实验中ESD相对低剂量和剂量适中的2组(90 cm和110 cm)开展临床试验。所有患儿住院期间采用同一X线机对同一患儿进行胸部DR的初查和复查,并分为初查组和复查组,初查组采用SID=110 cm,复查组采用SID=90 cm,由3位影像学专家采用5分法对图像质量进行打分。结果通过影像学专家评判,80~150 cm的DR曝光图像质量无差异,且不同的SID下实施胸部体模DR,得到的毫安秒与辐射剂量不相同,同一体模在相同曝光指数下,随着SID的增大,毫安秒与辐射剂量均逐渐增大;初查组的图像质量评分为(4.9±1.0)分,复查组的图像质量评分为(4.9±1.0),2组的图像质量评分比较差异无统计学意义(P>0.05)。结论患儿DR胸部摄影中不同SID,其体表辐射剂量具有明显差异,SID为90 cm时能够大幅度地降低X线管的输出剂量,减少体表辐射剂量,延长X线管的使用寿命。     

Towards image quality, beam energy and effective dose optimisation in digital thoracic radiography

This paper outlines how objective measurements of both image quality, in terms of signal-to-noise ratio, and effective dose may be used as tools to find the optimum kVp range for a digital chest radiography system. Measurements were made with Thoravision, an amorphous selenium-based digital chest X-ray system. The entrance surface dose and the effective dose to an anthropomorphic chest phantom were determined demonstrating how effective dose is related to beam quality. The image quality was measured using detective quantum efficiency, threshold contrast and a radiologist preference trial involving 100 patients. The results show that, despite the fact that the entrance surface dose decreases as the kVp increases, the effective dose, a better measure of the risk, reaches a minimum value between 90 and 110 kVp; however, the image quality decreases as the kVp increases. In this study the optimum kVp for chest radiography, using a selenium-based radiography system, is in the range 90–110 kVp. This is contrary to the 120- to 150-kVp range that is commonly used. Also, this study shows how objective measurements can be used to optimise radiographic technique without prolonged patient trials. Received: 4 November 1999 Revised: 10 May 2000 Accepted: 11 May 2000     

A multi institutional comparison of imaging dose and technique protocols for neonatal chest radiography

IntroductionThe focus on paediatric radiation dose reduction supports reevaluation of paediatric imaging protocols. This is particularly important in the neonates where chest radiographs are frequently requested to assess respiratory illness and line placement. This study aims to assess the impact of neonatal chest radiographic protocols on patient dose in four hospitals in different countries.MethodsExposure parameters, collimation, focus to skin distance (FSD) and radiation dose from 200 neonatal chest radiographs were registered prospectively. Inclusion criteria consisted of both premature and full-term neonates weighing between 1000 and 5000 g. Only data from the examinations meeting diagnostic criteria and approved for the clinical use were included. Radiation dose was assessed using dose area product (DAP).ResultsThe lowest DAP value (4.58 mGy cm²) was recorded in the Norwegian hospital, employing a high kVp, low mAs protocol using a DR system. The Canadian hospital recorded the highest DAP (9.48), using lower kVp and higher mAs with a CR system, including the addition of a lateral projection. The difference in the mean DAP, weight, field of view (FOV) and kVp between the hospitals is statistically significant (p < 0.001).ConclusionUse of non-standardised imaging protocols in neonatal chest radiography results in differences in patient dose across hospitals included in the study. Using higher kVp, lower mAs and reducing the number of lateral projections to clinically relevant indications result in a lower DAP measured in the infant sample studied. Further studies to examine image quality based on exposure factors and added filtration are recommended.Implications for practiceReevaluation of paediatric imaging protocols presents an opportunity to reduce patient dose in a population with increased sensitivity to ionising radiation.