A study of optimum radiographic conditions on chest examinations with computed radiology (CR) in conjunction with the offset balance of patient dose and image quality]

In a report of a nationwide survey on radiographic conditions of chest radiography in Japan, it was pointed out that the average entrance surface dose (ESD) of the computed radiography (CR) system was higher than that of the film-screen system. It seemed important that an objective index and criteria be established for dose reduction without a loss of image quality that would interfere with diagnostic observation. For this purpose, we investigated the properties of root of mean square (RMS) granularity, since it is a dominant factor in CR image quality and strongly depends on dose. The results indicated that RMS granularity showed little dependence on tube voltage when relative exposure was kept constant and that it decreased with the increment of exposure and approached a finite minimum value in a very high exposure region. For the most frequently used radiographic conditions in Japan (120 kV, 2.5 mmAl, 200 cm SID, 10: 1 grid), the decrement in RMS granularity from 6 to 16 mAs was 0.0276 to 0.0253 (9.1%). This finding suggested that exposure exceeding 6 mAs did not improve image quality, i.e., exposure reduction down to 6 mAs would not cause a significant loss of image quality. It was therefore concluded that RMS granularity was a useful objective index by which to determine the upper limit of exposure. Use of the most frequent conditions with 6 mAs seemed to be recommendable as an initial condition for the technical optimization of CR chest radiography, since ESD under this condition was 0.265 mGy, which was approximately equal to the value of the ESD distribution of a total chest radiogram in Japan.     

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.     

Diagnostic capability of digital radiography of the chest using scanning laser stimulated luminescence

Diagnostic capability of Fuji Computed Radiography (FCR) of the chest was compared to the conventional radiography (CoR) using regular film-screen system. FCR utilizes imaging plates of scanning laser stimulated luminescence. Visibility of 14 structures of the chest radiography was evaluated by 3 radiologists in 100 pairs of FCR and CoR which were taken at the same time with the same exposure factors. FCR was superior to CoR especially in observation of the mediastinum and areas behind the heart and diaphragm. The minor fissure was better seen on CoR. Superiority of FCR to CoR was thought to be mainly due to the processed image of FCR, and the so-called normal image of FCR had little diagnostic advantage. Simulated abnormal densities: nodular, alveolar, and interstitial densities with a chest phantom, were made, and detectability of alteration of these densities on FCR and CoR was evaluated by 19 radiologist, using ROC curve analysis. FCR and CoR revealed the similar diagnostic capability in nodular and interstitial densities. In alveolar densities, however, FCR was statistically inferior to CoR. Nineteen radiologists were divided into 3 groups by their experience in radiology, and comparison was made as to their diagnostic capability with FCR and CoR in the same manner as described above. There was no significant difference among the groups with FCR in either density pattern.     

计算机X线摄影中优化摄影条件的测试探讨

目的：探讨计算机X线摄影(computed radiography，CR)条件的优化，提高CR摄影图像质量的影响。方法：应用CR系统获取铝梯影像，在相同像素值条件下：①改变kV，求所需mAs；②在相同光条件下求各阶铝梯影像间的像素值平均偏差及平均偏差减量。结果：①kV值分别为50、60、70、80、90、100、110、120时，所需mAs分别为80、22、9、4．5、2．5、1．8、1．2、1．0；②在相同光条件下，对应于各阶铝梯影像间的像素值平均偏差依次为73．1、57．6、50．4、44，4、39．6、36．0、33．6、32．04。像素平均偏差减量依次为15．5、7．2、6．0、4．8、3．6、2．4、1．2。结论：在相同影像像素值情况下，随kV增加，CR摄影所需mAs降低，阶铝梯影像间的像素值平均偏差及平均偏差减量影像降低。影像对比度下降。     

DR系统中平板探测器能量响应特性的研究

目的 研究平板探测器(FPD)对kV、mAs的响应特性。方法使用HOLOGIC公司生产的DR系统，变换摄影条件，通过系统软件功能测出设定各点的原始灰度值，通过比较发现其变化规律，为摄影条件的选择提供指导。结果在100kV内，影像的原始灰度值随着kV值的增加而近乎呈线性增加，而大于100kV后，影像的灰度值随着kV增加而增加的幅度明显下降；FPD对mA和曝光时间的响应特性几近线性。结论胸部数字X射线摄影的最佳kV值在100kV左右。在kV满足穿透力的前提下，不要只通过增加kV值来提高影像的灰度值(高kV摄影除外)；要配合mA和曝光时间的变化来增加或降低影像的灰度值，合理化选择摄影条件的搭配，避免不必要的辐射损伤。     

Digital radiography of the chest: state of the art

Digital image acquisition possesses a number of advantages over conventional systems in radiographic examination of the chest, the most important of which is its greater dynamic range. In addition, one digital images are acquired, they can be processed by computer in ways that cannot be rivalled by conventional analog techniques. Finally, digital images can be stored, retrieved and transmitted to local or remote sites. Here the status of the different digital systems employed in chest radiology and commonly used image processing techniques are reviewed. Also discussed are the current clinical applications of integrating digital chest radiography with a picture archiving and communication system (PACS) along with the difficulties typically encountered. Studies with a variety of digital techniques have been carried out on several fronts. Computer radiography based on photostimulabe phosphor (CR) has replaced screen-film imaging in certain applications (i.e. bedside imaging). However, CR has limitations, namely its poor X-ray utilisation efficiency at high X-ray tube voltages and sensitivity to scatter; therefore, it is not ideal for all applications. Recently, a dedicated digital chest unit with excellent X-ray utilisation efficiency at high X-ray tube potentials has been introduced. On the basis during the past decade, recommendations are made regarding the most desirable equipment specifications for dedicated and bedside digital chest radiography.     

X射线胸部摄影曝光剂量与图像质量相关性研究

目的 研究数字化X射线胸部高千伏摄影曝光剂量与图像质量的关系,确定数字化X射线摄影最佳曝光剂量。方法 选择胸部高千伏摄影管电压120 kV,摄影mAs从1 mAs逐档增加至25 mAs,对模拟人体胸部厚度摄影体模与CDRAD 2.0对比度细节体模进行摄影,测量体模表面X射线入射剂量,由5位观察者独立阅读体模影像,比较任意两曝光条件组之间的图像质量因子（IQF）,确定高千伏胸部摄影最佳条件。比较4和10 mAs条件下正常人体胸部摄影图像质量评分。结果 胸部高千伏摄影体模曝光条件从1 mAs增加到25 mAs,体模表面X射线入射剂量从0.067 mGy增加至1.468 mGy。随着X射线入射剂量的增加,影像质量影响因子IQF值不断减小,观察者阅读体模信号的IQF差异有统计学意义（F=31.00,P<0.05）,曝光剂量条件选择在1~4 mAs时所对应的IQF均值差异有统计学意义（F=15.3,P<0.05）,4~10 mAs时所对应的IQF差异无统计学意义,10~25 mAs时所对应的IQF均值差异有统计学意义（F=9.74,P<0.05）。曝光剂量条件选择4和10 mAs所对应的体模表面入射剂量为0.250和0.606 mGy,两种条件下胸部图像质量的综合评分分别为（24.8±1.64）、（25.8±2.05）分,差异无统计学意义。结论 随着数字化X射线摄影剂量的增加所获得图像信息量增加。满足临床诊断的标准人体胸部高千伏数字化X摄影最佳剂量为0.250 mGy左右。     

The effect of X-ray tube potential on the image quality of PA chest radiographs when using digital image acquisition devices

The rapid development in digital acquisition technology in radiography has not been accompanied by information regarding optimum radiographic technique for use with newly developed systems. Three of the most common technologies for digital radiographic examinations of the chest are flat panel amorphous Silicon Caesium Iodide systems (FPD), amorphous Selenium drums (DSD) and photostimulable storage phosphor computed radiography (CR). Published data on the effect of X-ray beam energy on image quality and patient dose when using these digital image acquisition devices are reviewed. It is important that radiographers are aware of optimum kVp selection for these systems, particularly for the commonly performed chest examination.     

General equations for optimal selection of diagnostic image acquisition parameters in clinical X-ray imaging

The purpose of this work was to examine the effects of relationship functions between diagnostic image quality and radiation dose on the governing equations for image acquisition parameter variations in X-ray imaging. Various equations were derived for the optimal selection of peak kilovoltage (kVp) and exposure parameter (milliAmpere second, mAs) in computed tomography (CT), computed radiography (CR), and direct digital radiography. Logistic, logarithmic, and linear functions were employed to establish the relationship between radiation dose and diagnostic image quality. The radiation dose to the patient, as a function of image acquisition parameters (kVp, mAs) and patient size (d), was used in radiation dose and image quality optimization. Both logistic and logarithmic functions resulted in the same governing equation for optimal selection of image acquisition parameters using a dose efficiency index. For image quality as a linear function of radiation dose, the same governing equation was derived from the linear relationship. The general equations should be used in guiding clinical X-ray imaging through optimal selection of image acquisition parameters. The radiation dose to the patient could be reduced from current levels in medical X-ray imaging.     

Radiation exposure and image quality in chest CT examinations.

OBJECTIVE: The purpose of this study was to determine how changes in radiographic tube current affect patient dose and image quality in unenhanced chest CT examinations. SUBJECTS AND METHODS: Ten sets of CT images were obtained from patients undergoing CT-guided chest biopsies. For each patient, six images of the same region were obtained at settings between 40 and 280 mAs. CT data were used to reconstruct tomographic sections with a field of view limited to the normal contralateral lung. Images were printed using lung and mediastinal image display settings. Image quality was determined by asking radiologists to assess the perceived level of mottle in CT images. Five chest radiologists ranked the relative image quality of six images. Patient effective doses were computed for chest CT examinations performed at each milliampere-second setting. Radiologists indicated whether any perceived improvement of image quality at the higher radiation exposures was worth the additional radiation dose. RESULTS: The differences in quality of chest CT images generated at greater than or equal to 160 mAs were negligible. Reducing the radiographic technique factor below 160 mAs resulted in a perceptible reduction in image quality. Differences in CT image quality for radiographic techniques between 120 and 280 mAs were deemed to be insufficient to justify any additional patient exposure. However, the use of 40 mAs results in an inferior image quality that would justify increased patient exposure. CONCLUSION: Radiographic techniques for unenhanced chest CT examinations can be reduced from 280 to 120 mAs without compromising image quality.     

Modifications to mobile chest radiography technique during the COVID-19 pandemic – implications of X-raying through side room windows

IntroductionModifications to common radiographic techniques have resulted from the challenges presented by the COVID-19 pandemic. Reports exist regarding the potential benefits of undertaking mobile radiography through side room windows. The aim of this study was to evaluate the impact on image quality and exposure factors when undertaking such examinations.MethodsA phantom based study was undertaken using a digital X-ray room. Control acquisitions, using a commercially available image quality test tool, were performed using standard mobile chest radiography acquisition factors. Image quality (physical and visual), incidence surface air kerma (ISAK), Exposure Index (EI) and Deviation Index (DI) were recorded. Image quality and radiation dose were further assessed for two additional (experimental) scenarios, where a side room window was located immediately adjacent to the exit port of the light beam diaphragm. The goal of experimental scenario one was to modify exposure factors to maintain the control ISAK. The goal of experimental scenario two was to modify exposure factors to maintain the control EI and DI. Dose and image quality data were compared between the three scenarios.ResultsTo maintain the pre-window (control) ISAK (76 μGy), tube output needed a three-fold increase (90 kV/4 mAs versus 90 kV/11.25 mAs). To maintain EI/DI a more modest increase in tube output was required (90 kV/8 mAs/ISAK 54 μGy). Physical and visual assessments of spatial resolution and signal-to-noise ratio were indifferent between the three scenarios. There was a slight statistically significant reduction in contrast-to-noise ratio when imaging through the glass window (2.3 versus 1.4 and 1.2; P = 0.005).ConclusionUndertaking mobile X-ray examinations through side room windows is potentially feasible but does require an increase in tube output and is likely to be limited by minor reductions in image quality.Implications for practiceMobile examinations performed through side room windows should only be used in limited circumstances and future clinical evaluation of this technique is warranted.     

胸部摄影附加滤过对辐射剂量的影响

目的 探讨不同附加滤过对成人胸部高电压X射线摄影的图像质量、辐射剂量和X射线管负荷的影响,筛选合适附加滤过厚度,优化临床摄影参数.资料与方法 分析心脏手术前后进行检查的32例患者采用0、0.1、0.2、0.3mm铜附加滤过胸部摄影图像的质量,并进行患者皮肤入射剂量和散射线剂量率标准水模实验测试.结果 随着附加滤过板厚度的增加,患者皮肤入射剂量下降约30％,管负荷增加,室内散射线剂量率明显减少.32例患者不同厚度滤过板的各图像质量均具有一致性(P＜ 0.01).结论 摄影时选用一定厚度的附加滤过板可以减少患者表面剂量,同时不会造成X射线图像质量下降.进行成人胸部高仟伏摄影时,宜添加0.1～0.2mm的铜附加滤过,以达到防护最优化要求.     

Quantitative assessment of mineral content in metacarpal bone with Fuji computed radiography

A new microdensitometry method for quantitative assessment of bone mineral content using Fuji computed radiography (FCR) was developed and the results were compared with those obtained by the conventional film-screen method. Using both methods, X-ray pictures of the 2nd metacarpal bone were taken with a reference aluminum step wedge in nine normal subjects and nine parameters representing the width and density of bone marrow and cortex were calculated in the middle of the bone shaft. Interobserver reproducibility assessed for three parameters was significantly higher in the FCR method than the conventional one. The value of sigma GS computed by the FCR method, that is equivalent to the net bone density of the transverse section of the shaft, showed higher correlation with the one obtained by computed tomography in comparison with the conventional method. In our FCR method, moreover, interobserver reproducibility and accuracy was improved by employing automatic manipulation as much as possible in the process of calculation. The exposure dose in the FCR method could be reduced to half of the one in the conventional method without deteriorating the accuracy. In conclusion, our new microdensitometry method with FCR provides high accuracy and good reproducibility for the measurement of bone mineral content with small exposure dose and is likely to be useful for the long-term follow-up of the osteoporotic patients from the variety of causes.     

降低X线照射量与投照条件最优化的探讨

Investigation and measurement of the radiation dose level of routine X-ray diagnostic examinations were carried out on the spot, the results were as follows: Radiation dose of routine radiography: chest 0.258-1.032 x 10(-4) c/kg (0.1-0.4R); spinal and abdomen 0.774-1.806 x 10(-4) c/kg (0.3-0.7R); skull 0.774-1.032 x 10(-4) c/kg (0.3-0.4R) and gastrointestinal study 2.58-7.74 x 10(-4) c/kg (1-3R). Experiments employing different kV and mAs, and radiation exposure on 12-18 mm A1 phantoms while measuring the radiation dose and film density showed that radiation dose can be substantially reduced by improving the quality of X-ray beam for instance with the routine radiographic parameters for the chest, if the voltage is increased by 20 kV, radiation dose can be reduced to 65% or an additional 2 mm A1 filter can also reduce the dose to 60-65%.     

Investigating the use of an antiscatter grid in chest radiography for average adults with a computed radiography imaging system

Objective:

The aim of this study was to investigate via simulation a proposed change to clinical practice for chest radiography. The validity of using a scatter rejection grid across the diagnostic energy range (60–125 kVp), in conjunction with appropriate tube current–time product (mAs) for imaging with a computed radiography (CR) system was investigated.

Methods:

A digitally reconstructed radiograph algorithm was used, which was capable of simulating CR chest radiographs with various tube voltages, receptor doses and scatter rejection methods. Four experienced image evaluators graded images with a grid (n = 80) at tube voltages across the diagnostic energy range and varying detector air kermas. These were scored against corresponding images reconstructed without a grid, as per current clinical protocol.

Results:

For all patients, diagnostic image quality improved with the use of a grid, without the need to increase tube mAs (and therefore patient dose), irrespective of the tube voltage used. Increasing tube mAs by an amount determined by the Bucky factor made little difference to image quality.

Conclusion:

A virtual clinical trial has been performed with simulated chest CR images. Results indicate that the use of a grid improves diagnostic image quality for average adults, without the need to increase tube mAs, even at low tube voltages.

Advances in knowledge:

Validated with images containing realistic anatomical noise, it is possible to improve image quality by utilizing grids for chest radiography with CR systems without increasing patient exposure. Increasing tube mAs by an amount determined by the Bucky factor is not justified.Radiography of the chest is one of the most frequently performed diagnostic radiographic examinations in the UK. In 2010, the Health Protection Agency (now Public Health England) reported¹ that chest radiographs represented 19.6% of all radiographic examinations in 2008 (although the contribution to collective dose was small at about 0.5%), so optimization of radiation dose (i.e. ensuring dose is as low as reasonably practicable) and image quality (i.e. ensuring all required clinical structures are visible to the reporting healthcare professional so that an acceptable diagnosis is possible) in chest radiography is an important research area, especially since digital imaging has all but replaced its film-screen counterpart. It is also a legal requirement in the UK under the Ionising Radiation (Medical Exposure) Regulations 2000² to optimize all medical exposures, consistent with the intended purpose.One such technique to optimize image quality in chest radiography is to use a scatter rejection grid. They work by preferentially removing radiation scattered by the body prior to reaching the detector, and their improvement of image quality in film-screen imaging has been recognized for decades.^3–6 This improvement was described by the contrast improvement factor⁷ but came with a cost. Film requires a given level of incident exposure to ensure adequate optical density (OD), and because a grid attenuates most of the scattered radiation (as well as some primary radiation), this necessitates an increase in tube current–time product (mAs). The Bucky factor describes the necessary multiplication by which exposure parameters must be increased, and for film-screen can be anything between 2–6 times the “non-gridded” exposure.^8,9 Regardless of this, there are clear guidelines recommending the use of scatter rejection grids with film-screen systems for adult chest radiography,¹⁰ but none for digital imaging modalities, although Fritz and Jones¹¹ have recently published guidelines for scatter rejection techniques in paediatric digital radiology.Digital image detectors, such as computed radiography (CR) photostimulable powder phosphors, have a larger dynamic range than does film,¹² and grey levels in the resulting image are usually adjusted, irrespective of incident detector dose, to match the output of the display monitor. Therefore, unlike film, digital imaging is not contrast (OD) limited. At doses used clinically (e.g. air kerma of approximately 2–15 µGy at the receptor), digital images are dominated by quantum noise (i.e. other noise sources such as electronic and structural are typically ≤2% of the total noise as consistently demonstrated through in-house routine quality assurance testing of this CR system), which depends on the level of air kerma incident on the detector (signal) and the detector''s detective quantum efficiency. Therefore, when a scatter rejection grid is used, appropriate exposure factors (tube''s peak kilo-voltage and/or mAs) are required to maintain a level of image signal-to-noise ratio (SNR)^13,14 acceptable to the image evaluator, although there is no agreement as to what these appropriate exposure factors should be. A common school of thought, described in a considerable resource by Carlton and Adler,¹⁵ suggests that the lower limit on the increase in mAs should be the reciprocal of the primary transmission (T_p) of the grid and the upper limit, the Bucky factor. The reciprocal of T_p for modern grids is typically 1.2–1.4, which suggests that an increase in mAs of at least 20% is required. However, Tanaka et al¹⁶ have recently demonstrated that the use of grids (grid ratios 5 : 1 to 14 : 1) without increasing exposure factors (compared with “non-gridded” exposures), actually improved the effective noise equivalent quanta (eNEQ) when acquiring images of 20 cm of polymethylmethacrylate (PMMA). They concluded that the improvement to image quality owing to removal of scatter outweighs the increase in quantum noise when a grid is used, although they acknowledged that their work did not use any images with anatomical structure. Similarly, Fetterly and Schueler¹⁷ studied numerous grids with different thicknesses of uniform solid water and suggested that a scatter rejection grid can provide improvement in SNR without increasing exposure for large patients.Given the scarcity of evidence/guidelines in the literature, the aim of this study was two-fold: firstly, to investigate the validity of using a scatter rejection grid for chest radiography of average adults with an Agfa CR imaging system (Agfa, Peissenberg, Germany) across the diagnostic energy range (60–125 kVp); and secondly, to investigate appropriate tube mAs to identify what increase in patient dose (if any) there needs to be. Many recent studies have demonstrated that anatomical noise (the influence of projected anatomy on the image evaluator’s ability to detect potential abnormalities and provide an accurate diagnosis) is the limiting factor in chest radiography,^18–27 so it was felt that the inclusion of realistic anatomy in the images used in this study was of particular importance, rather than using uniform PMMA or solid water only. Therefore, computer-simulated chest radiographs (each containing realistic projected anatomical noise and lung abnormalities/nodules), reconstructed with a scatter rejection grid, were compared by expert image evaluators with images reconstructed without a grid (as per current clinical protocol in our radiology department).     

Digital chest radiology.

With an increasing number of storage phosphor computed radiography units being installed worldwide, the evaluation of digital chest radiology is no longer being confined to experimental determinations of adequate imaging variables. There has been a substantial increase in the number of clinically based studies that have compared computed radiography with conventional film radiography. The applications of computed radiography are widening and further developments in dual-energy imaging and scanning equalization radiography have become possible through the use of phosphor storage computed radiography. Computer-assisted diagnosis applied to chest radiography may shortly be revolutionized by artificial intelligence, which is capable of assimilating both radiographic and clinical data.     

Patient absorbed doses in digital grey-scale fluorography

This article describes a preliminary comparison between the levels of patient dose used in digital grey-scale fluorography (DGF) and screen-film radiography. Patient doses were measured in three common radiographic examinations, postero-anterior chest, antero-posterior lumbar spine and lateral lumbo-sacral junction, using thermoluminescent dose-meters and an anthropomorphic phantom. Within the limitations of the image quality currently available in DGF, the findings indicate that digital radiography with the large-field X-ray image intensifier promises significant savings in patient dose compared with conventional radiography.     

Stomach and duodenum: radiographic magnification using computed radiography (CR)

We performed direct radiographic magnification (X3) using a 0.1-mm microfocal tube and computed radiography (CR) in air-barium double-contrast studies of the stomach and duodenum. To eliminate blurring of the image due to motion, we used the maximum kilovolt peak rate possible (102 kVp), the maximum milliampere second rate possible (64 mAs), the shortest possible exposure time (0.1 second), and a horizontal x-ray beam. With the patients in the supine position, CR provided the wide image reproduction range required to obtain satisfactory radiographs. Image processing in the CR system produced radiographs with increased radiographic contrast and enhanced edge definition of anatomic borders or pathologic processes. The duodenal villi were clearly visible in 45% of the cases.     

Characteristic evaluation and clinical usefulness of dose area product meter at radiography

Philips DigitalDiagnost, a digital radiographic system mounting flat panel detector (FPD), can display dose area data (DiDi dose) calculated by examination parameters. We evaluated its fundamental characteristics and compared the values of DiDi dose andactual measured data obtained by the area dose product meter (PD-4100L). Tendency of varied values of mAs, X-ray tube values and exposure area from both the area dose product meter and the DiDi dose were coincided. Further, in clinical images of chest PA 100 cases, chest lateral 50 cases and abdomen stand 25 cases, the determination coefficient was overly high as R(2)=0.99. Based on these results, it is clear that the DiDi dose can be treated the same as the area dose product meter. Under increasing of patient X-ray exposure dose is a concern in digital general radiography, this research indicates that maximum values of histogram obtained by DiDi dose contributes dose awareness for radiographer.     

Advances in neutron radiographic techniques and applications: a method for nondestructive testing.

A brief history of neutron radiography is presented to set the stage for a discussion of significant neutron radiographic developments and an assessment of future directions for neutron radiography. Specific advances are seen in the use of modern, high dynamic range imaging methods (image plates and flat panels) and for high contrast techniques such as phase contrast, and phase-sensitive imaging. Competition for neutron radiographic inspection may develop as these techniques offer application prospects for X-ray methods.