Image quality for five modern chest radiography techniques: a modified FROC study with an anthropomorphic chest phantom

The purpose of the study was to compare the image quality for one conventional and four digital chest radiography techniques. Three storage phosphor systems, one selenium drum system, and one film-screen system were compared using a modified receiver-operating-characteristics method. Simulated pathology was randomly positioned over the parenchymal regions and the mediastinum of an anthropomorphic phantom. Eight observers (four chest radiologists, one specialist in general radiology, one hospital physicist, and two radiographers) evaluated 60 images for each technique. The selenium drum system (Philips, Eindhoven, The Netherlands) rated best for the detection of parenchymal nodules. Together with the storage phosphor system of generation IIIN (Philips/Fuji), the selenium drum system also rated best for detection of thin linear structures. The storage phosphor system of generation V (Fuji) rated best for the detection of mediastinal nodules. The first generation of the storage phosphor system from Agfa (Mortsel, Belgium) rated worst for the detection of parenchymal nodules and thin linear structures. These differences were significant (p < 0.0001). Averaging the results for all test objects, the selenium drum system and the storage phosphor system of generation V were significantly better than the other systems tested. The film/screen system performed significantly better than the first-generation storage phosphor system from Agfa, equal to the generation IIIN storage phosphor system (Philips/Fuji) and significantly worse than the selenium drum system (Philips) and the generation-V storage phosphor system (Fuji). The conclusion is therefore that the image quality of selenium-based digital technique and of the more recent generations of storage phosphor systems is superior to both conventional technique and storage phosphor systems using image plates of older types. Received: 11 September 1997; Revised: 25 June 1998; Accepted: 18 February 1999     

A phantom approach to find the optimal technical parameters for plain chest radiography

A simple approach based on phantom measurements is proposed in this study to find the filtration, tube potential and antiscatter device that are optimal in respect of patient dose and image quality, at constant film-screen combination, film processing and viewing conditions. An original quasi-anthropomorphic chest phantom was exposed with 18 different beam qualities and three antiscatter devices. The entrance surface dose, organ doses and effective dose were estimated for each radiograph. The image quality was compared using two objective quality indexes, a contrast index and a scatter fraction, as well as two subjective indexes, a low contrast visualization index and a high contrast visualization index. It was found that for this X-ray unit, routinely using a 7:1 antiscatter grid, the optimal imaging technique is added filtration of 0.1 mm Cu+1 mm Al at a tube potential 100 kVp. Using a 25 cm air gap instead of the grid allows the tube potential to be increased to the upper limit of 120 kVp for this unit. The entrance surface dose of 0.075 mGy at 120 kVp with an air gap is less than half the value of the same quantity with a grid at 100 kVp and is significantly below the European reference level of 0.3 mGy. This phantom method, comprising both objective measurements and subjective estimation, is suitable for dose-image quality optimization in a clinical environment.     

Contrast-detail phantom study for x-ray spectrum optimization regarding chest radiography using a cesium iodide-amorphous silicon flat-panel detector

RATIONALE AND OBJECTIVES: The purpose of this study evaluating a cesium iodide-amorphous silicon-based flat-panel detector was to optimize the x-ray spectrum for chest radiography combining excellent contrast-detail visibility with reduced patient exposure. MATERIALS AND METHODS: A Lucite plate with 36 drilled holes of varying diameter and depth was used as contrast-detail phantom. For 3 scatter body thicknesses (7.5 cm, 12.5 cm, 21.5 cm Lucite) images were obtained at 113 kVp, 117 kVp, and 125 kVp with additional copper filter of 0.2 and 0.3 mm, respectively. For each setting, radiographs acquired with 125 kVp and no copper filter were taken as standard of reference. On soft-copy displays, 3 observers blinded to the exposure technique evaluated the detectability of each aperture in each image according to a 5-point scale. The number of points given to all 36 holes per image was added. The scores of images acquired with filtration were compared with the standard images by means of a multivariate analysis of variance. Radiation burden was approximated by referring to the entrance dose and calculated using Monte Carlo method. RESULTS: All 6 evaluated x-ray spectra resulted in a statistically equivalent contrast-detail performance when compared with the standard of reference. The combination 125 kVp with 0.3 mm copper was most favorable in terms of dose reduction (approximately 33%). CONCLUSION: Within the constraints of the presented contrast-detail phantom study simulating chest radiography, the CsI/a-Si system enables an addition of up to 0.3 mm copper filtration without the need for compensatory reduction of the tube voltage for providing constant image quality. Beam filtration reduces radiation burden by about 33%.     

胸部DR摄影中管电压对影像质量和辐射剂量影响的模体研究

目的 研究胸部数字X射线摄影(DR)中,不同管电压对影像质量以及受检者辐射剂量的影响。方法 管电压在80~130 kV范围内间隔10 kV变化,每种管电压设置下自动曝光控制(AEC)范围在-4~4对成人胸部模体进行曝光。测量模体表面的皮肤入射剂量,计算相对噪声值和对比度噪声比(CNR),并估算每次曝光时受检者的有效剂量。结果 皮肤入射剂量为(0.062 9±0.027 4)mGy,有效剂量为(0.012 7±0.004 5)mSv,有效剂量随着皮肤入射剂量的增加而呈线性增加,两者呈正相关关系(r=0.912,P<0.01)。随着有效剂量的增加,相同管电压下,相对噪声与有效剂量呈负相关关系(r=-0.967、-0.969、-0.968、-0.969、-0.968、-0.970, P<0.01);CNR与有效剂量呈正相关关系(r=0.987、0.987、0.986、0.987、0.988、0.989,P<0.01)。AEC不变时,随着kV值增加,皮肤入射剂量和有效剂量均降低,最大可降低50%和20%;相对噪声值降低,最大可降低23%;CNR增加,最大可增加8%。结论 胸部DR摄影中,在满足影像质量要求的前提下,高kV值可有效降低受检者辐射剂量。     

胸部数字摄影参数的最优化探索

目的探索胸部X线数字化摄影优化条件。方法应用柯尼卡Regins350(直接数字转换器350型)CR、柯达DirectviewCR-900、柯达DirectviewDR5000;西门子-MultixX光机;胸部X线摄影质量控制体模;EBM-上海岱嘉公司PACS系统-医学图像诊断工作站软件:Unisight;Barco1K显示器,采用不同摄影条件对专用测试体模进行摄影,同时,还对12名正常成人志愿者进行胸部X线摄影试验,分别对所获60幅体模图像和人体胸部图像的质量进行分析。结果通过对采集的60幅体模图像的肺野、心脏后缘及膈下的3个点测试表明获得最佳空间分辨率的摄影参数,对于柯尼卡Regins350为10mAs、109kV和20mAs、99kV,柯达CR-900和柯达DR5000均为10mAs、109kV和20mAs、109kV。结论DR图像显示胸部结构的清晰度和信息量均明显优于CR图像,胸部数字化摄影的最优化摄影条件为90kV～110kV,10mAs～(20±5)mAs。     

数字化X线胸部摄影参数优化的探讨

目的 探讨数字化X线胸部摄影参数的优化,以确保影像质量和降低X线曝光量.方法 用碘化色-非晶硅平板探测器数字化X线摄影系统对30例患者(志愿者)用90 kV和125 kV行胸部后前站立位数字化X线摄影,评价影像质量和X线曝光量的大小.结果 胸部125 kV数字化X线摄影比90 kV数字化X线摄影可减少X线曝光量约68%,影像层次更丰富.结论 数字化X线胸部摄影应以高千伏(125 kV)摄影为宜.     

Application of a simple phantom in assessing the effects of dose reduction on image quality in chest radiography

PurposeFirstly, to evaluate a commercial chest phantom incorporating a quasi anthropomorphic insert by comparing exposure measurements on the phantom with those of actual patients and, secondly, to assess the value of the phantom for image quality and dose optimisation.MethodsIn the first part of the study entrance surface doses (ESD), Beam transmission (BT), and optical density (OD) were obtained for 77 chest radiography patients and compared with measurements made from exposures of the phantom using the respective patient exposure factors from chest examination. Differences were assessed with a student t-test, while the Pearson's linear correlation coefficient was used to test for any linear relationship. The second part assessed the applicability of the phantom to image quality studies by investigating the effect, on the clarity and detectability of lung lesions made from gelatine, of reducing patient dose below current dose levels. Clarity of linear objects of different dimensions was also studied. Lesion detectability and clarity was assessed by four observers. The possibility of extending dose reduction below current dose levels (D_ref) was assessed from comparison of doses that produced statistically significant differences in image quality from D_ref.ResultsResults show that, with the exception of entrance doses and beam transmission through the diaphragm (P > 0.05), differences in OD and beam transmission between patients and phantom were statistically significant (P < 0.05). A Pearson's correlation test showed good positive correlation in ESD (r = 0.9) and beam transmission (r = 0.8) for all regions and a weaker positive correlation (r = 0.3) for OD in all areas. In both cases the correlation was statistically significant (P < 0.05). Extending dose reduction by between 41 and 65% below D_ref produced significant changes in both clarity and detectability.ConclusionWithin limits posed by the observed differences, the phantom can be applied to image quality studies in diagnostic radiology.     

Effects of optimization and image processing in digital chest radiography: an ROC study with an anthropomorphic phantom.

A digital system for chest radiography based on a large image intensifier was compared to a conventional film-screen system. The digital system was optimized with regard to spatial and contrast resolution and dose. The images were digitally processed for contrast and edge enhancement. A simulated pneumothorax and two simulated nodules were positioned over the lungs and the mediastinum of an anthropomorphic phantom. Observer performance was evaluated with ROC analysis. Five observers assessed the processed digital images and the conventional full-size radiographs. The time spent viewing the full-size radiographs and the digital images was recorded. For the simulated pneumothorax, the results showed perfect performance for the full-size radiographs and detectability was high also for the processed digital images. No significant difference in the detectability of the simulated nodules was seen between the two imaging systems. The results for the digital images showed a significantly improved detectability for the nodules in the mediastinum as compared to a previous ROC study where no optimization and image processing was available. No significant difference in detectability was seen between the former and the present ROC study for small nodules in the lung. No difference was seen in the time spent assessing the conventional full-size radiographs and the digital images. The study indicates that processed digital images produced by a large image intensifier are equal in image quality to conventional full-size radiographs for low-contrast objects such as nodules.     

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.     

Mobile chest radiography: improving image quality

Mobile examinations present special challenges yet require the same diagnostic quality as exams performed in the radiology department. This article describes a study designed to identify common errors in mobile chest radiography. The authors identify 3 areas of particular concern: rotation, anatomy not centered to the film and distortion. Possible solutions are suggested and discussed.     

床旁DR与CR胸部摄影质量的对比研究

目的通过床旁数字化X线摄影(digitalradiography,DR)系统与计算机X线摄影(computedradiography,CR)系统胸部摄影图像质量的对比分析,探讨床旁DR摄影的优势。方法随机抽取2010年拍摄的DR床旁X线胸片1000份和既往CR床旁X线胸片1000份进行对比分析。结果床旁DR摄影的应用提供了更加优良的图像质量,明显减少了放射技师的工作量,同时还降低了患者接受的辐射剂量。结论床旁DR胸部摄影比CR胸部摄影有着明显的优势,对手术患者和危重患者的诊治起到了积极作用。     

Comparing image quality of flat-panel chest radiography with storage phosphor radiography and film-screen radiography

OBJECTIVE: To evaluate image quality of a large-area direct-readout flat-panel detector system in chest radiography, we conducted an observer preference study. A clinical comparative study was conducted of the flat-panel system versus the storage phosphor and standard film-screen systems. MATERIALS AND METHODS: Routine chest radiographs (posteroanterior) of 30 patients that were obtained using flat-panel, storage phosphor, and film screen systems were compared. The visibility of 10 anatomic regions and the overall image quality criteria were rated independently by three radiologists using a 5-point scale. The significance of the differences in diagnostic performance was tested with a Wilcoxon's signed rank test. Dose measurements for the three modalities were performed. RESULTS: The flat-panel radiography system showed an improved visibility in most anatomic structures when compared with a state-of-the-art conventional film-screen system and an equal visibility when compared with a storage phosphor system. The flat-panel system showed the greatest enhancement in the depiction of small detailed structures (p < 0.05) and achieved this with a reduction in overall radiation dose of more than 50%. CONCLUSION: The visibility of anatomic structures provided by this flat-panel detector system is as good as if not better than that provided by conventional or storage phosphor systems while emitting a reduced radiation dose.     

胸片影像质量综合评价

影像质量综合评价是评价胸片影像质量常用而有效的一种方法。胸片影像质量综合评价分为视读评价、物理评价、摄影技术评价及入射剂量评价四方面,总体分为综合评价分数分配、综合评价内容分类及读片评价等级三大内容。本文根据影像质量综合评价要求和具备的条件,结合临床实际情况,对胸片影像质量综合评价进行了综述。     

骨盆数字化X射线摄影曝光剂量的优化研究

目的研究直接数字化X射线摄影照射剂量与成像质量的关系，确定骨盆X射线摄影的最佳摄影条件。方法以对比度一细节体模CDRAD2．0在不同照射剂量下所获取的影像的图像质量因子IQF，进行ANOVA及SNK统计学分析，确定最佳照射条件。应用X射线摄影模拟人拍摄骨盆X射线影像，按照欧共体（CEC）图像质量标准验证最佳摄影条件与常规摄影条件下照射剂量与成像质量的差别。结果不同照射剂量条件下，对比度一细节体模影像质量因子IQF有显著性差别（P=0．0001），照射剂量大于0．61mGy时，不同剂量组间IQF差异无统计学意义。对以最佳照射条件和常规照射条件所拍摄的X射线摄影模拟人影像按照CEC标准评判，两者影像质量的差异无统计学意义。结论直接数字化X射线摄影时通过增大照射剂量可以提高影像质量，但是当曝光剂量达到足够大时，再增大曝光剂量并不能显著改善图像质量，影像质量与曝光剂量间存在一个优化剂量。标准体模骨盆X射线摄影的优化剂量为0．61mGy。     

Dose and image quality optimization in neonatal radiography

In a special care baby unit, neonates, mainly premature, encounter serious to life-threatening diseases, the timely diagnosis and treatment of which may require a large number of radiographs. Increased neonatal radiosensitivity and longer life expectancy increase the risk of radiation-induced cancer, which emphasizes the importance of minimizing dose while maintaining clinically satisfactory image quality. An optimization study on radiation dose and image quality in neonatal radiography is presented. Neonates were categorized into four groups depending on birthweight. For a total of 378 chest and chest-abdomen radiographs, exposure parameters were recorded. Entrance surface dose (ESD) was estimated and dose-area product (DAP) was measured. Image quality evaluation was performed by two observers and was based on the visibility of certain anatomical features and catheters placed during treatment using a five-grade scale. ESD values increased with neonatal weight and demonstrated wide variation (16.4-76.9 microGy, mean 38.2 microGy). A wide variation was also observed in DAP values (1.2-15.0 mGycm2, mean 7.2 mGycm2). Image quality evaluation revealed the feasibility of achieving a diagnostically satisfactory image (score >70%) using both low and high tube voltage techniques, with the latter resulting in reduced ESDs. The majority of estimated ESDs are in accordance with the reference level of 50 microGy recommended by the National Radiological Protection Board for neonatal radiography. The results suggest that the use of high tube voltage techniques could result in further reductions in neonatal dose, without image quality degradation, underlying the requirement for establishing standard examination protocols for neonatal radiography with respect to neonatal weight.     

Dose reduction in digital chest radiography and perceived image quality

The aim of the study was to investigate whether radiologists can rank the image quality of digital radiographs with different doses; a preliminary study investigated whether reduced dose images provide sufficient diagnostic quality. Raw data of 40 chest radiographs (posteroanterior (PA) and lateral) obtained with a full-field slot-scan charge-coupled device system in 20 patients with chest pathology were used. Noise was added to simulate reduced dose levels to 50%, 25% and 12%. Four observers ranked the quality of the corresponding images and judged the diagnostic quality. Linear regression analysis was performed. Differences were found in image quality at the different dose levels for both PA (p相似文献   

Optimization of image quality and patient exposure in chest radiography

Chest radiography using an automatic exposure device gives an acceptable reproducible standard. However, the standard radiograph tends to be the preferred way of working and is comparable in terms of dose and quality.