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.     

双能量减影数字X线摄影技术的应用

目的:用双能量减影数字X线摄影提高肺部小结节病变的检出率。方法:双能量减影摄影可以用两次曝光法和一次曝光法来完成。结果:双能量减影数字化胸部摄影技术作为胸部X线检查的一种辅助手段,它能有效的提高肺部小结节病变的检出率,并能增加鉴别诊断的依据。结论:直接数字化X线摄影(DR)的使用,使两次曝光法得以实行。由于两次曝光法能量差大,它产生的双能量减影图像上组织对比良好,图像信噪比高,比一次曝光法具有更明显的优势。     

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.     

Contrast-detail evaluation and dose assessment of eight digital chest radiography systems in clinical practice

The purpose of this study was to assess contrast-detail performance and effective dose of eight different digital chest radiography systems. Digital chest radiography systems from different manufacturers were included: one storage phosphor system, one selenium-coated drum system, and six direct readout systems including four thin-film transistor (TFT) systems and two charge-coupled device (CCD) systems. For measuring image quality, a contrast-detail test object was used in combination with a phantom that simulates the primary and scatter transmission through lung fields (LucAl). Six observers judged phantom images of each modality by soft-copy reading in a four-alternative-forced-choice experiment. The entrance dose was also measured, and the effective dose was calculated for an average patient. Contrast-detail curves were constructed from the observer data. The blocked two-way ANOVA test was used for statistical analysis. Significant difference in contrast-detail performance was found between the systems. Best contrast-detail performance was shown by a CCD system with slot-scan technology, and the selenium-coated drum system was compared to the other six systems (p values 0.003). Calculated effective dose varied between 0.010 mSv and 0.032 mSv. Significant differences in contrast-detail performance and effective dose levels were found between different digital chest radiography systems in clinical practice.     

A detailed study of radiation dose and radiographic technique during chest radiography

The radiation dose to a series of patients referred for chest radiography has been monitored using thermoluminescent dosimetry. The postero-anterior projection was employed throughout the study. Measurements were made in two rooms of the same general hospital. Each room was equipped with automatic exposure control of the air ionisation chamber type. The effect of this equipment on patient exposure was investigated and compared with manual exposure control. In all cases the tube potential (kVp) was selected by the radiographer but tube current (mA) was determined by the generator. Anterior and posterior radiation doses were measured using sachets of lithium fluoride. For each group of patients the anterior exit dose, and therefore all of the radiation dose, was lower when automatic control was used. The standard deviation on the anterior patient dose was lower under automatic control, which resulted in fewer films needing to be repeated due to incorrect film density. Film densities were also investigated using a densitometer, to provide a further comparison between the two types of exposure control.     

Image quality of supine chest radiographs: intra-individual comparison of computed radiography and low-dose linear-slit digital radiography

The purpose of this retrospective study was to intra-individually compare the image quality of computed radiography (CR) and low-dose linear-slit digital radiography (LSDR) for supine chest radiographs. A total of 90 patients (28 female, 62 male; mean age, 55.1 years) imaged with CR and LSDR within a mean time interval of 2.8 days ± 3.0 were included in this study. Two independent readers evaluated the image quality of CR and LSDR based on modified European Guidelines for Quality Criteria for chest X-ray. The Wilcoxon test was used to analyse differences between the techniques. The overall image quality of LSDR was significantly better than the quality of CR (9.75 vs 8.16 of a maximum score of 10; p < 0.001). LSDR performed significantly better than CR for delineation of anatomical structures in the mediastinum and the retrocardiac lung (p < 0.001). CR was superior to LSDR for visually sharp delineation of the lung vessels and the thin linear structures in the lungs. We conclude that LSDR yields better image quality and may be more suitable for excluding significant pathological features of the chest in areas with high attenuation compared with CR.     

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.     

Optimization of chest radiographic imaging parameters: a comparison of image quality and entrance skin dose for digital chest radiography systems

We studied the performance of three computed radiography and three direct radiography systems with regard to the image noise and entrance skin dose based on a chest phantom. Images were obtained with kVp of 100, 110, and 120 and mA settings of 1, 2, 4, 8, and 10. Significant differences of image noise were found in these digital chest radiography systems (P<.0001). Standard deviation was significantly different when the mAs were changed (P<.001), but it was independent of the kVp values (P=.08-.85). Up to 44% of radiation dose could be saved when kVp was reduced from 120 to 100 kVp without compromising image quality.     

Optimisation of radiological protocols for chest imaging using computed radiography and flat-panel X-ray detectors

Purpose

Digital radiography technology has replaced conventional screen-film systems in many hospitals. Despite the different characteristics of new detector materials, frequently, the same radiological protocols previously optimised for screen film are still used with digital equipment without any critical review. This study addressed optimisation of exposure settings for chest examinations with digital systems, considering both image quality and patient dose.

Materials and methods

Images acquired with direct digital radiography equipment and a computed radiography system were analysed with specially developed commercial software with a four-alternative forced-choice method: the most promising protocols were then scored by two senior radiologists.

Results

Digital technology offers a wide dynamic range and the ability to postprocess images, allowing use of lower tube potentials in chest examinations. The computed radiography system showed both better image quality and lower dose at lower energies (85 kVp and 95 kVp) than those currently used (125 kVp). Direct digital radiography equipment confirmed both its superior image quality and lower dose requirements compared with the storage phosphor plate system.

Conclusions

Generally, lowering tube potentials in chest examinations seems to allow better image quality/effective dose ratio when using digital equipment.     

Radiation dose optimization research: Exposure technique approaches in CR imaging – A literature review

The purpose of this paper is to review the literature on exposure technique approaches in Computed Radiography (CR) imaging as a means of radiation dose optimization in CR imaging. Specifically the review assessed three approaches: optimization of kVp; optimization of mAs; and optimization of the Exposure Indicator (EI) in practice. Only papers dating back to 2005 were described in this review.The major themes, patterns, and common findings from the literature reviewed showed that important features are related to radiation dose management strategies for digital radiography include identification of the EI as a dose control mechanism and as a “surrogate for dose management”. In addition the use of the EI has been viewed as an opportunity for dose optimization. Furthermore optimization research has focussed mainly on optimizing the kVp in CR imaging as a means of implementing the ALARA philosophy, and studies have concentrated on mainly chest imaging using different CR systems such as those commercially available from Fuji, Agfa, Kodak, and Konica-Minolta. These studies have produced “conflicting results”. In addition, a common pattern was the use of automatic exposure control (AEC) and the measurement of constant effective dose, and the use of a dose-area product (DAP) meter.     

Pediatric digital chest radiography, comparison of grid versus non-grid techniques

Introduction

The usefulness of anti-scatter grid in digital pediatric chest radiography was investigated by a phantom study assessing image quality using subjective evaluations and dose measurements.

Method

A contrast detail study was undertaken. Images were taken with and without anti-scatter grids (grid ratio 15:1), for PMMA phantom thickness ranging from 1 to 15 cm. Fourteen radiographers, experienced in digital pediatric and/or skeletal radiography, read 96 images. At each thickness, the image with and without grid technique was read three times, and in random order. Correct Observation Ratio (COR) and Image Quality Figures (IQF) were calculated. Dose Area Products were measured with DAP-meter.

Results

The COR and IQF values indicated statistically significant (p < 0.05) enhanced image quality when using anti-scatter grid for all thicknesses 5 cm and more. The DAP values increased significantly by grid techniques (p = 0.01).

Conclusions

Grid techniques may be beneficial to image quality for PMMA objects over 5 cm, but this leads to a higher dose. Although the magnitude of dose may be low, the dose should be kept at a minimum. In conclusion, improving image quality should be based on optimizing post-processing settings and image evaluation conditions.     

Image quality evaluation of dual-layer spectral detector CT of the chest and comparison with conventional CT imaging

ObjectivesTo evaluate image quality parameters of virtual mono-energetic (MonoE) and conventional (CR) imaging derived from a dual-layer spectral detector CT (DLCT) in oncological follow-up venous phase imaging of the chest and comparison with conventional multi-detector CT (CR_MDCT) imaging.Materials and methodsA total of 55 patients who had oncologic staging with conventional CT and DLCT of the chest in venous phase were included in this study. Established image quality parameters were derived from all datasets in defined thoracic landmarks. Attenuation, image noise, and signal-/contrast- to noise ratios (SNR, CNR) were compared between CR_DLCT and MonoE as well as CR_MDCT imaging. Two readers performed subjective image analysis.ResultsCR_MDCT showed significant lower attenuation values compared to CR_DLCT and MonoE at 40–70 keV (p ≤ 0.05). Moreover, MonoE at 40–70 keV revealed significantly higher attenuations values compared to CR_DLCT (p < 0.001). Noise was statistically lower in CR_MDCT compared with CR_DLCT and MonoE at 40 keV (11.4 ± 2.3 HU vs. 12.0 ± 3.1 HU vs. 11.7 ± 5.2 HU; p < 0.001). In contrast, all MonoE levels showed significantly lower noise levels compared to CR_DLCT (p < 0.001). SNR was not significantly different between CR_MDCT and CR_DLCT (13.5 ± 3.7 vs. 14.4 ± 5.3; p > 0.99). SNR values were significantly increased for MonoE at 40–80 keV compared to CR_MDCT and CR_DLCT (p < 0.001). CR_DLCT and MonoE (40–70 keV) from DLCT revealed significantly higher CNR values than CR_MDCT (p < 0.001). In subjective analysis, MonoE at 40 keV surpassed all other image reconstructions except for noise in MonoE at 70 keV.ConclusionIn dual-layer spectral detector CT, MonoE at low keV showed superior image quality compared to conventional images derived from the same system and may therefore be added to clinical routine imaging protocols. Whether MonoE reconstructions yield additional diagnostic information is still unknown.     

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。     

CR与非晶体硅DR胸部摄影曝光剂量优化的探讨

目的 比较CR与非晶体硅DR在胸部摄影中入射剂量的差异,探讨两者最优化曝光剂量。方法 应用CR、DR分别对胸部模体行不同入射剂量曝光成像,记录模体表面入射剂量,用CDRAD2.0评估软件计算模体影像图像质量因子反数值IQFinv。CR组、DR组图像IQFinv差异用两独立样本t 检验;CR组、DR组各自图像IQFinv与入射剂量的关系应用pearson相关;应用ROC曲线分析获取两组最佳图像IQFinv值,并换算曝光剂量。结果 CR和DR组入射剂量和图像质量IQFinv值之间呈明显的正相关(r =0.893、0.848, P<0.01),并存在线性回归。CR和DR组IQFinv值差异有统计学意义(t =5.455, P<0.05)。ROC曲线分析(曲线下面积AUC＝0.893, P<0.001),最佳IQFinv值为3.55。结论 CR、DR系统对于低对比度细节的检测能力均随着入射剂量的增加而增加。入射剂量相同时,DR系统对于低对比度细节的检测能力优于CR;在获得相同的图像质量时,与CR相比应用DR可大大降低被检者辐射剂量。     

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。     

Fetal chest ultrasound and magnetic resonance imaging: recent advances and current clinical applications

Advances in high-resolution prenatal ultrasound and fetal magnetic resonance (MR) imaging have changed the practice of obstetrics by allowing better visualization of intrathoracic and neck structures and better estimation of lung volumes. More accurate prenatal diagnosis has increased options for pregnancy management and treatment, delivery planning, and postnatal care. Anyone who is interested in the fascinating field of fetology should become familiar with the current state of fetal imaging of the chest as well as potential advances in technology and research.     

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.     

两种平板探测器X线摄影系统的成像剂量与成像质量的比较研究

目的 定量分析、比较非晶硅平板探测器X射线摄影系统与非晶硒平板探测器X射线摄影系统在不同成像剂量条件下成像质量的差别。方法 以非晶硅平板探测器系统和非晶硒平板探测器系统分别摄取对比度-细节体模CDRAD2.0在相近曝光剂量条件下的X射线影像,由4位独立观察者分别阅读影像,并计算所对应的曝光剂量下图像质量因子（image quality figure,IQF）,应用ANOVA分析两成像系统对比度及细节检测能力。使用X射线摄影统计学体模（TRG）测量两系统在不同曝光剂量条件下操作者特性曲线（receive operating characteristics,ROC）,应用Wilcoxon检验分析、比较两种成像技术的影像信息检测能力的差别。结果 在低曝光剂量条件下,两系统CDRAD体模影像IQF值及ROC曲线AZ值差别有显著意义,在对比度、组织细节检测能力上非晶硅平板探测器系统优于非晶硒平板探测器系统。在高曝光剂量条件下,两系统差异无统计学意义。结论 在低曝光剂量条件下,成像质量非晶硅平板探测器系统优于非晶硒系统。在获得相同的影像质量的前提下,使用前者进行X射线摄影可以降低被检者受照剂量。