Advances in computed radiography systems and their physical imaging characteristics

Contribución de la radiología digital al mejoramiento de la calidad en el servicio de imagenología

Objetivo. El presente estudio documental evalúa las estrategias óptimas de la radiología digital (DR) en los servicios de Radiología en los hospitales de baja y mediana complejidad en Colombia. Método. Revisión bibliográfica exhaustiva donde se identificó los beneficios y se hizo comparación con la radiología análoga, se desarrolló basado en una muestra de 32 artículos científicos en diferentes revistas como Dialnet, SciELO, Scopus, Springer Open, IOP Science. Resultado. La imagen por rayos X es una tecnología poderosa y de bajo costo que se ha utilizado ampliamente en el diagnóstico médico. La importancia tecnológica de las imágenes de rayos X ha llevado al rápido desarrollo de detectores de rayos X de alto rendimiento y las aplicaciones de imágenes asociadas. Por lo tanto, los servicios de imágenes médicas proponen estrategias efectivas en la funcionalidad de la radiología digital, factores que interfieren con el proceso del sistema informático. Conclusión. Teniendo en cuenta los avances técnicos y fundamentales de los detectores de rayos X, el surgimiento de la radiografía computarizada (CR) (DR) ha llevado a la evolución tecnológica para la obtención de imágenes de rayos X digitales con información más precisa e instantánea, mientras que su mecanismode lectura separado adolece de limitaciones técnicas, como una alta dosis de radiación y una imagen no dinámica, esto permite a los prestadores de servicio de imagenología se motiven a invertir en una tecnología adecuada para generar un aprovechamiento más óptimo de los recursos y el servicio sea prestado al paciente con alta calidad.

Recent Development in X-Ray Imaging Technology: Future and Challenges

X-ray imaging is a low-cost, powerful technology that has been extensively used in medical diagnosis and industrial nondestructive inspection. The ability of X-rays to penetrate through the body presents great advances for noninvasive imaging of its internal structure. In particular, the technological importance of X-ray imaging has led to the rapid development of high-performance X-ray detectors and the associated imaging applications. Here, we present an overview of the recent development of X-ray imaging-related technologies since the discovery of X-rays in the 1890s and discuss the fundamental mechanism of diverse X-ray imaging instruments, as well as their advantages and disadvantages on X-ray imaging performance. We also highlight various applications of advanced X-ray imaging in a diversity of fields. We further discuss future research directions and challenges in developing advanced next-generation materials that are crucial to the fabrication of flexible, low-dose, high-resolution X-ray imaging detectors.

Image Quality Evaluation of a Digital Radiography System Made in Thailand

Background

The National Science and Technology Development Agency (NSTDA) in Thailand researched and prototyped digital radiography systems under the brand name BodiiRay aiming for sustainable development and affordability of medical imaging technology. The image restoration and enhancement were implemented for the systems.

Purpose

The image quality of the systems was evaluated using images from phantoms and from healthy volunteers.

Methods

The survey phantom images from BodiiRay and other two commercial systems using the exposure settings for the chest, the abdomen, and the extremity were evaluated by three experience observers in terms of the high-contrast image resolution, the low-contrast image detectability, and the grayscale differentiation. The volunteer images of the chests, the abdomens, and the extremities from BodiiRay were evaluated by three specialized radiologists based on visual grading on 5-point scaled questionnaires for the anatomy visibility, the image quality satisfaction, and the diagnosis confidence in using the images.

Results

BodiiRay phantom results were similar to those from the commercial systems. The overall performance averaged across the exposure settings showed that BodiiRay was slightly better than Fujifilm FDR Go in the low-contrast detectability (p = 0.033) and in the grayscale differentiation (p = 0.004). It was also slightly better than Siemens YSIO Max in the high-contrast resolution (p = 0.018). The images of chest, pelvis, and hand phantoms illustrated comparable visual quality. For volunteer images, the percentage of the images scored ≥4 ranged from 61% to 99%, 23% to 92%, and 96% to 99% for the chest, abdomen, and extremity images, respectively. The average score ranged from 3.63 to 4.46, 3.18 to 4.21, and 4.41 to 4.51 for the chest, abdomen, and extremity images, respectively.

Conclusion

The phantom image results showed the comparability of these systems. The clinical evaluation showed BodiiRay images provided sufficient image qualities for digital radiography of these body parts.

XAOM: A method for automatic alignment and orientation of radiographs for computer-aided medical diagnosis

BACKGROUND AND OBJECTIVES

Computer-aided diagnosis relies on machine learning algorithms that require filtered and preprocessed data as the input. Aligning the image in the desired direction is an additional manual step in post-processing, commonly overlooked due to workload issues. Several state-of-the-art approaches for fracture detection and disease-struck region segmentation benefit from correctly oriented images, thus requiring such preprocessing of X-ray images. Furthermore, it is desirable to have archived studies in a standardized format. Radiograph hanging protocols also differ from case to case, which means that images are not always aligned and oriented correctly. As a solution, the paper proposes XAOM, an X-ray Alignment and Orientation Method for images from 21 different body regions.

METHODS

Typically, other methods are crafted for this purpose to suit a specific body region and form of usage. In contrast, the method proposed in this paper is comprehensive and easily tuned to align and orient X-ray images of any body region. XAOM consists of two stages. For the first stage of the method, aligning X-ray images, we experimented with the following approaches: Hough transform, Fast line detection algorithm, and Principal Component Analysis method. For the second stage, we have experimented with the adaptations of several well known convolutional neural network topologies for correctly predicting image orientation: LeNet5, AlexNet, VGG16, VGG19, and ResNet50.

RESULTS

In the first stage, the PCA-based approach performed best. The average difference between the angle detected by the algorithm and the angle marked by the experts on the test set containing 200 pediatric X-ray images was 1.65^∘, while the median value was 0.11^∘. In the second stage, the VGG16-based network topology achieved the best accuracy of 0.993 on a test set containing 4,221 images.

CONCLUSION

XAOM is highly accurate at aligning and orienting pediatric X-ray images of 21 common body regions according to a set standard. The proposed method is also robust and can be easily adjusted to the different alignment and rotation criteria.

AVAILABILITY

The Python source code of the best performing implementation of XAOM is publicly available at https://github.com/fhrzic/XAOM.

Chimera of digital radiography in spine surgery: False diagnosis of implant failure

BACKGROUND

Digital radiographs of the whole spine are made using marginally superimposed imaging plates exposed simultaneously to be combined by interpolation of the overlapping area. Post-processing artefacts in these radiographs leading to the misdiagnosis of implant breakage have not yet been described in the literature.

METHODS

An erroneous fusion of a digital spine x-ray after scoliosis surgery created an image showing two broken rods, whereas both rods proved complete continuity intraoperatively. Following an interdisciplinary error analysis, the chain of errors was systematically reconstructed. Using the digital imaging material of patients operatively treated the same way; the reproducibility of the error was analyzed. Erroneous image fusions were produced by slight displacement of existing, not yet combined x-ray images of these patients.

RESULTS

Under certain requirements, the false impression of implant breakage could be reproduced. Especially in the case of missing or malpositioned radiopaque markers, the hazard to overlook an erroneous image fusion is present. Within the post-processing step performed by qualified staff, control is indispensable and manual correction can be crucial.

CONCLUSIONS

This experimental study and causal analysis show the clinical relevance of post-processing artefacts in digital radiography. To prevent false diagnosis and maltreatment, the knowledge of possible sources of error is indispensable.

An Experimental Study for Minimum Level of Decalcification to Detect the Osteolytic Bone Metastasis of Long Bone on Plain Radiography

Background

In 1951, Ardran reported that metastatic bone lesions could be detectable on plain radiography with 30% to 50% of decalcification. Authors performed experimental study for minimum level of decalcification to detect the osteolytic bone metastasis of long bone with recent technique of radiographs.

Methods

One pair of fibula and humerus from two cadavers was cut into specimen 1 inch in length. Distal half of specimen was dipped into hydrochloride (HCl) with 15 min interval. All 16 specimens were checked by film-type radiography (FR), computed radiography (CR), digital radiography (DR). To exclude inter-observer's variance, 3 radiologists evaluated images. Calcium amount before and after decalcification was measured and expressed in percentage of decalcification.

Results

Osteolytic changes were detectable with 11% to 16% of decalcification for fibula and 3% to 8% for humerus on plain radiography with FR, CR, and DR.

Conclusions

Our study showed that minimum of 3% and maximum of 16% of decalcification is necessary when osteolytic metastatic bone lesions of long bone could be detected on plain radiography.

Bedside Lung Ultrasound During Acute Chest Syndrome in Sickle Cell Disease

Lung ultrasound (LU) is increasingly used to assess pleural and lung disease in intensive care unit (ICU) and emergency unit at the bedside. We assessed the performance of bedside chest radiograph (CR) and LU during severe acute chest syndrome (ACS), using computed tomography (CT) as the reference standard. We prospectively explored 44 ACS episodes (in 41 patients) admitted to the medical ICU. Three imaging findings were evaluated (consolidation, ground-glass opacities, and pleural effusion). A score was used to quantify and compare loss of lung aeration with each technique and assess its association with outcome. A total number of 496, 507, and 519 lung regions could be assessed by CT scan, bedside CR, and bedside LU, respectively. Consolidations were the most common pattern and prevailed in lung bases (especially postero-inferior regions). The agreement with CT scan patterns was significantly higher for LU as compared to CR (κ coefficients of 0.45 ± 0.03 vs 0.30 ± 0.03, P < 0.01 for the parenchyma, and 0.73 ± 0.08 vs 0.06 ± 0.09, P < 0.001 for pleural effusion). The Bland and Altman analysis showed a nonfixed bias of -1.0 (P = 0.12) between LU score and CT score whereas CR score underestimated CT score with a fixed bias of -5.8 (P < 0.001). The specificity for the detection of consolidated regions or pleural effusion (using CT scan as the reference standard) was high for LU and CR, whereas the sensitivity was high for LU but low for CR. As compared to others, ACS patients with an LU score above the median value of 11 had a larger volume of transfused and exsanguinated blood, greater oxygen requirements, more need for mechanical ventilation, and a longer ICU length of stay. LU outperformed CR for the diagnosis of consolidations and pleural effusion during ACS. Higher values of LU score identified patients at risk of worse outcome.

Pixel Bleeding Correction in Laser Scanning Luminescence Imaging Demonstrated Using Optically Stimulated Luminescence

This paper describes and investigates the performance of an algorithm to correct for "pixel bleeding" caused by slow luminescence centers in laser scanning imaging (e.g., X-ray imaging using photostimulable phosphors and 2D dosimetry using optically stimulated luminescence). The algorithm is based on a deconvolution procedure that takes into account the lifetime of the slow luminescence center and is further constrained by the detection of fast and slow luminescence centers and combining rows scanned in opposite directions. The algorithm was tested using simulated data and demonstrated experimentally by applying it to image reconstruction of two types of Al2O3 X-ray detector films ( Al2O3:C and Al2O3 :C,Mg), whose use in 2D dosimetry in conjunction with laser-scanning readout has so far been prevented by slow luminescence centers (F-centers, 35 ms lifetime). We show that the algorithm allows the readout of Al2O3 film detectors 300-500 times faster than generally allowed considering the lifetime of the main luminescence centers. By relaxing the stringent requirements on the detector's luminescence lifetime, the algorithm opens the possibility of using new materials in 2D dosimetry as well as other laser scanning applications, such as X-ray imaging using storage phosphors and scanning confocal microscopy, although the effect of the noise introduced must be investigated for each specific application.

Minimally invasive, maximal outcomes in breast surgery

The contemporary treatment of breast cancer has evolved in response to numerous randomised control trials which have aided in the development of guidelines for effective treatment. Breast cancer surgery has progressed thanks in part to the advances made in chemotherapy, radiation therapy and early detection. As these advances continue the field of surgery needs to progress in tandem to maximise survival outcomes but to also minimise morbidity.

Radiographic imaging for patients with contagious infectious diseases: how to acquire chest radiographs of patients infected with the Ebola virus

OBJECTIVE

Contagious infectious diseases add a new dimension to radiology and pose many unanswered questions. In particular, what is the safest way to image patients with contagious and potentially lethal infectious diseases? Here, we describe protocols used by Emory University to successfully acquire chest radiographs of patients with Ebola virus disease.

CONCLUSION

Radiology departments need to develop new protocols for various modalities used in imaging patients with contagious and potentially lethal infectious diseases.

[Detection of lung nodules. New opportunities in chest radiography]

BACKGROUND

Chest radiography still represents the most commonly performed X-ray examination because it is readily available, requires low radiation doses and is relatively inexpensive. However, as previously published, many initially undetected lung nodules are retrospectively visible in chest radiographs.

STANDARD RADIOLOGICAL METHODS

The great improvements in detector technology with the increasing dose efficiency and improved contrast resolution provide a better image quality and reduced dose needs.

METHODICAL INNOVATIONS

The dual energy acquisition technique and advanced image processing methods (e.g. digital bone subtraction and temporal subtraction) reduce the anatomical background noise by reduction of overlapping structures in chest radiography. Computer-aided detection (CAD) schemes increase the awareness of radiologists for suspicious areas.

RESULTS

The advanced image processing methods show clear improvements for the detection of pulmonary lung nodules in chest radiography and strengthen the role of this method in comparison to 3D acquisition techniques, such as computed tomography (CT).

ASSESSMENT

Many of these methods will probably be integrated into standard clinical treatment in the near future. Digital software solutions offer advantages as they can be easily incorporated into radiology departments and are often more affordable as compared to hardware solutions.

Exposure creep in computed radiography: a longitudinal study

PURPOSE

Exposure creep is the gradual increase in x-ray exposures over time that results in increased radiation dose to the patient. It has been theorized as being a phenomenon that results from the wide-exposure latitude of computed radiography (CR) and direct/indirect digital radiography (DR). This project evaluates radiographic exposures over 43 months to determine if exposure creep exists and if measures can be applied to halt or reverse exposure creep trends.

METHODS

Exposure indices were initially recorded over 29 months between August 2007 and December 2009 from the intensive and critical care unit (ICCU) and the emergency department (ED) departments where manual CR exposures were used. The data from this period were then assessed and the exposure indexes (EI) values from the radiographic images were compared to the radiology department criteria of EI values between 1400 to 1800 as being in the optimal exposure range. EI values below this were considered underexposed and over this as overexposed. An intervention was required to be used in ICCU and implemented in January 2010 to halt a noted trend of overexposure. The EI value for each chest x-ray (CXR) was recorded in the patients' ICCU records and was to be used by radiologic technologists/radiographers in determine exposure factors in subsequent CXR. After the intervention, EI values were recorded and evaluated for an additional 15 months between February 2010 and March 2011.

RESULTS

Between August 2007 and December 2009, 17,678 ICCU CXR images and 69,327 ED x-ray examinations were evaluated for over- and underexposure. A trend was noted in ICCU that showed a significant increase (P = .023) in EI values from the beginning to the end of the evaluation. No such trend was seen in the ED EI values (P = .120). After the intervention in ICCU, the overexposure trend was halted.

CONCLUSIONS

Exposure creep has been show to exist. It is surmised that this occurs where judgment to determine the correct radiographic exposure factors is needed when taking into account a large range of patient sizes. It has also been shown that providing radiologic technologists/radiographers with previous EI values for the same x-ray examination can halt a trend of exposure creep.

Investigation into Factors Influencing Fuji S-Value Using an Extremity Phantom

Exposure indices are provided by manufacturers to give an indication of exposure for computed radiography (CR). Although there are recommended ranges for exposure index values for various examinations, they may be affected by a number of other factors in addition to exposure. This study using an extremity phantom found collimation to be the most important factor influencing the S-value for a Fuji CR system. It is therefore essential that collimation is kept as tight as possible without excluding relevant anatomy. CR imaging plates should be processed rapidly after exposure to prevent loss of information stored in the latent image. The reliability of the S-value exposure index as an indicator of exposures can be increased with better understanding of how it works, and by practical application of this knowledge to radiography.

Modeling the performance characteristics of computed radiography (CR) systems

Computed radiography (CR) using storage phosphors is widely used in digital radiography and mammography. A cascaded linear systems approach wherein several parameter values were estimated using Monte Carlo methods was used to model the image formation process of a single-side read ;;flying spot'' CR system using a granular phosphor. Objective image quality metrics such as modulation transfer function and detective quantum efficiency were determined using this model and show good agreement with published empirical data. A model such as that addressed in this work could allow for improved understanding of the effect of storage phosphor physical properties and CR reader parameters on objective image quality metrics for existing and evolving CR systems.

Development of an online automatic computed radiography dose data mining program: a preliminary study

Recent studies have reported the computed radiography (CR) dose creep problem and therefore the need to have monitoring processes in place in clinical departments. The objective of this study is to provide a better technological solution to implement a regular CR dose monitoring process. An online automatic CR dose data mining program which can be applied to different systems was developed based on freeware and existing softwares in the Picture Archiving and Communication System (PACS) server. The program was tested with 69 CR images. This preliminary study shows that the program addresses the major weaknesses of some existing studies including involvement of manual procedures in the monitoring process and being only applicable to a single manufacturer's CR images. The proposed method provides an efficient and effective solution to implement a CR dose monitoring program regularly in busy clinical departments to regulate the dose creep problem so as to reinforce the 'As Low As Reasonably Achievable' (ALARA) principle.

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.

Solid-state, flat-panel, digital radiography detectors and their physical imaging characteristics

Solid-state, digital radiography (DR) detectors, designed specifically for standard projection radiography, emerged just before the turn of the millennium. This new generation of digital image detector comprises a thin layer of x-ray absorptive material combined with an electronic active matrix array fabricated in a thin film of hydrogenated amorphous silicon (a-Si:H). DR detectors can offer both efficient (low-dose) x-ray image acquisition plus on-line readout of the latent image as electronic data. To date, solid-state, flat-panel, DR detectors have come in two principal designs, the indirect-conversion (x-ray scintillator-based) and the direct-conversion (x-ray photoconductor-based) types. This review describes the underlying principles and enabling technologies exploited by these designs of detector, and evaluates their physical imaging characteristics, comparing performance both against each other and computed radiography (CR). In standard projection radiography indirect conversion DR detectors currently offer superior physical image quality and dose efficiency compared with direct conversion DR and modern point-scan CR. These conclusions have been confirmed in the findings of clinical evaluations of DR detectors. Future trends in solid-state DR detector technologies are also briefly considered. Salient innovations include WiFi-enabled, portable DR detectors, improvements in x-ray absorber layers and developments in alternative electronic media to a-Si:H.