Digital Chest Radiography Research Articles

Effect of tube voltage on digital chest radiograph for phantom and occupational exposed workers

To explore the image quality of different tube voltage on digital chest radiograph for contrast detail phantom (CDRAD2.0) and occupational exposed workers. The CDRAD2.0 phantom DR images of high KV and different tube voltages were analyzed by 3 readers, image quality figure (IQF) were calculated and compared; at the same time 136 exposed workers were examined with high-kV and DR chest radiograph of different tube voltages. Contrast to high-KV images, 10 anatomic sites were scored .The image differences were compared between DR and high-kV. On CDRAD2.0 phantom, the IQF value of DR images in 3 readers were minimum in the condition of 120 kV, average value was 22.25. The analysis of variance in model with random effects, the mean IQF value of different tube voltage DR image had a significant difference (F = 13.775, P<0.01); By Dunnett t-tests analysis, the mean IQF value of DR image in 120 kV and high kilovoltage had no difference (t = -0.58, P = 0.979); On clinical cases, the DR image of 120 kV showed the closest anatomy to the high KV, the mean had no significant difference with 0 (P > 0.05) with single sample t test. On the CDRAD2.0 phantom or clinical exposed workers, the DR image quality of 120 kV tube voltage equals to high-KV basically.

Support Vector Machine Model for Diagnosing Pneumoconiosis Based on Wavelet Texture Features of Digital Chest Radiographs

This study aims to explore the classification ability of decision trees (DTs) and support vector machines (SVMs) to discriminate between the digital chest radiographs (DRs) of pneumoconiosis patients and control subjects. Twenty-eight wavelet-based energy texture features were calculated at the lung fields on DRs of 85 healthy controls and 40 patients with stage I and stage II pneumoconiosis. DTs with algorithm C5.0 and SVMs with four different kernels were trained by samples with two combinations of the texture features to classify a DR as of a healthy subject or of a patient with pneumoconiosis. All of the models were developed with fivefold cross-validation, and the final performances of each model were compared by the area under receiver operating characteristic (ROC) curve. For both SVM (with a radial basis function kernel) and DT (with algorithm C5.0), areas under ROC curves (AUCs) were 0.94 ± 0.02 and 0.86 ± 0.04 (P = 0.02) when using the full feature set and 0.95 ± 0.02 and 0.88 ± 0.04 (P = 0.05) when using the selected feature set, respectively. When built on the selected texture features, the SVM with a polynomial kernel showed a higher diagnostic performance with an AUC value of 0.97 ± 0.02 than SVMs with a linear kernel, a radial basis function kernel and a sigmoid kernel with AUC values of 0.96 ± 0.02 (P = 0.37), 0.95 ± 0.02 (P = 0.24), and 0.90 ± 0.03 (P = 0.01), respectively. The SVM model with a polynomial kernel built on the selected feature set showed the highest diagnostic performance among all tested models when using either all the wavelet texture features or the selected ones. The model has a good potential in diagnosing pneumoconiosis based on digital chest radiographs.

Effect of digital radiography processing parameters on digital chest radiograph for occupational exposed workers

To investigate the effect of different processing parameters of digital radiography (DR) on the image quality of digital chest radiograph in dust-exposed workers. One hundred and five dust-exposed workers underwent both high-KV radiography and DR to obtain chest radiographs; the image processing parameters were set by the conventional processing method for digital chest radiograph (method A) and the processing method based on the special requirements of occupational diseases (method B). With the high-KV chest radiograph as the reference, the image qualities at 10 anatomic sites of DR image were graded. The images acquired by DR and high-KV radiography were compared, and the DR images acquired by methods A and B were also compared. For method A, the scores at the 10 anatomic sites of DR image were mostly 0 and +1, accounting for over 88%, and the mean score was 0.23 ∼ 0.65, there was a significant difference between the mean score of DR image and the score of high-KV image (P < 0.001). For method B, the scores at the 10 anatomic sites of DR image were mostly 0, accounting for over 65%, and the mean score was -0.01∼ +0.02 except at the pleura and chest wall; there was no significant difference between the mean score of DR image and the score of high-KV image (P > 0.05). There were significant differences in the scores at the 10 anatomic sites between the DR images acquired by methods A and B (P < 0.01). The DR images acquired based on different processing parameters are different. The quality of DR image acquired by the processing method based on the special requirements of occupational diseases is similar to that of high-KV image at the anatomic sites.

Letter to the Editor Re: the iPad Tablet Computer for Mobile On-Call Radiology Diagnosis? Auditing Discrepancy in CT and MRI Reporting

Letter to the Editor Re: the iPad Tablet Computer for Mobile On-Call Radiology Diagnosis? Auditing Discrepancy in CT and MRI Reporting

Commentary on: Comparison of chest digital tomosynthesis and chest radiography for detection of asbestos-related pleuropulmonary disease

For UK readers of Clinical Radiology that have become accustomed to the solitary frontal chest radiograph, seldom now accompanied by its partnered lateral radiograph, a potentially alarming sea of change may be coming. The article by Lee et al., which appears in the current issue of the Journal, highlights the potential utility of a relatively new digital chest radiographic technique using chest digital tomosynthesis (DTS).1 With this technique the simple single chest radiograph may suddenly expand to a virtual plethora of constituent images.

胸部単純X線画像におけるピクセルマッチング法を用いた経時的差分画像法の開発

A temporal subtraction image, which is obtained by subtraction of a previous image from a current one, can enhance interval changes on a chest radiograph by removal of most normal structures. However, subtraction artifacts, which tend to reduce its effectiveness in the detection of interval changes, were still included in the conventional method. In this study, we have developed a pixel matching technique to reduce artifacts in the temporal subtraction images. With this technique, the pixel value in a nonlinearly warped previous image is replaced by a pixel value within a kernel, which is closest to the pixel value on a current image. For evaluation of the proposed method, one hundred temporal subtraction images with a simulated nodule were used. When the kernel size of 3×3 was employed in the pixel matching technique, the misregistration artifacts decreased by 72%, and the contrast-to-noise ratio of the simulated lung nodules was increased by 5% in comparison with the conventional method. However, the area of the simulated nodule on the subtraction image decreased by 6%. Our results indicated that the pixel matching technique can enhance simulated nodules, with a substantial reduction of misregistration artifacts in comparison with conventional subtraction images. Therefore, we believe that the temporal subtraction method with the pixel matching technique would assist radiologists' diagnoses for detection of lung nodules in digital chest radiography.

Interpretation of Digital Chest Radiographs: Comparison of Light Emitting Diode versus Cold Cathode Fluorescent Lamp Backlit Monitors

ObjectiveTo compare the diagnostic performance of light emitting diode (LED) backlight monitors and cold cathode fluorescent lamp (CCFL) monitors for the interpretation of digital chest radiographs.Materials and MethodsWe selected 130 chest radiographs from health screening patients. The soft copy image data were randomly sorted and displayed on a 3.5 M LED (2560 × 1440 pixels) monitor and a 3 M CCFL (2048 × 1536 pixels) monitor. Eight radiologists rated their confidence in detecting nodules and abnormal interstitial lung markings (ILD). Low dose chest CT images were used as a reference standard. The performance of the monitor systems was assessed by analyzing 2080 observations and comparing them by multi-reader, multi-case receiver operating characteristic analysis. The observers reported visual fatigue and a sense of heat. Radiant heat and brightness of the monitors were measured.ResultsMeasured brightness was 291 cd/m2 for the LED and 354 cd/m2 for the CCFL monitor. Area under curves for nodule detection were 0.721 ± 0.072 and 0.764 ± 0.098 for LED and CCFL (p = 0.173), whereas those for ILD were 0.871 ± 0.073 and 0.844 ± 0.068 (p = 0.145), respectively. There were no significant differences in interpretation time (p = 0.446) or fatigue score (p = 0.102) between the two monitors. Sense of heat was lower for the LED monitor (p = 0.024). The temperature elevation was 6.7℃ for LED and 12.4℃ for the CCFL monitor.ConclusionAlthough the LED monitor had lower maximum brightness compared with the CCFL monitor, soft copy reading of the digital chest radiographs on LED and CCFL showed no difference in terms of diagnostic performance. In addition, LED emitted less heat.

Optimizing Imaging Quality and Radiation Dose by the Age-Dependent Setting of Tube Voltage in Pediatric Chest Digital Radiography

ObjectiveThe quality and radiation dose of different tube voltage sets for chest digital radiography (DR) were compared in a series of pediatric age groups.Materials and MethodsForty-five hundred children aged 0-14 years (yr) were randomly divided into four groups according to the tube voltage protocols for chest DR: lower kilovoltage potential (kVp) (A), intermediate kVp (B), and higher kVp (C) groups, and the fixed high kVp group (controls). The results were analyzed among five different age groups (0-1 yr, 1-3 yr, 3-7 yr, 7-11 yr and 11-14 yr). The dose area product (DAP) and visual grading analysis score (VGAS) were determined and compared by using one-way analysis of variance.ResultsThe mean DAP of protocol C was significantly lower as compared with protocols A, B and controls (p < 0.05). DAP was higher in protocol A than the controls (p <0.001), but it was not statistically significantly different between B and the controls (p = 0.976). Mean VGAS was lower in the controls than all three protocols (p < 0.001 for all). Mean VGAS did not differ between protocols A and B (p = 0.334), but was lower in protocol C than A (p = 0.008) and B (p = 0.049).ConclusionProtocol C (higher kVp) may help optimize the trade-off between radiation dose and image quality, and it may be acceptable for use in a pediatric age group from these results.

Morphological Reconstruction Based Segmentation of Lung Fields on Digital Radiographs

Objective To segment lung fields on digital chest radiographs automatically. Methods A morphological reconstruction filter was first applied to the original image to eliminate the local grey level extremes. Then, the Otsu-threshold method was used to segment the whole image into several connected regions, contours of which were then extracted by using a connected components labelling technique. Finally, a morphological closing operator was employed to smooth any small gaps or burrs of the lung field contours. Results Lung fields were segmented for 40 digital chest radiographs, resulting in an accurate segmentation and extraction of their lung fields for most images. Conclusion Integrating a series of algorithms, including morphological reconstruction filtering, Otsu-threshold segmentation, connected components labelling, and morphological operations for smoothing the outlines can effectively segment the lung fields on digital radiographs.

Computer-Aided Diagnosis for Pneumoconiosis Based on Texture Analysis on Digital Chest Radiographs

In this paper, texture analysis was used to discriminate digital chest radiographs of pneumoconiosis patients from normal ones. First, lung fields in each chest radiograph were segmented by using the morphological reconstruction and Otsu-thresholding. Second, several texture features based on the histogram and co-occurrence matrix of grey levels were extracted. Finally, a neural network based classifier was trained with features extracted from 66 chest images to distinguish pneumoconiosis patients from normal cases. Another 29 images were used to assess the diagnosis performance of the classifier, giving an overall accuracy of 79.3%.

Comparison of chest digital tomosynthesis and chest radiography for detection of asbestos-related pleuropulmonary disease

To compare chest digital tomosynthesis (DTS) with digital radiography for the detection of asbestos-related pleuropulmonary disease. The institutional review board approved this study and all participants gave informed consent. Forty-five participants with a history of asbestos exposure were examined with DTS and radiography. Low-dose multidetector computed tomography (CT) in the prone position served as the reference. Two observers evaluated all images for the presence of pleural abnormalities and asbestosis. Interobserver agreement was analysed by using the k statistic. Diagnostic performance of the two imaging methods was compared using McNemar's test. Interobserver agreement regarding DTS findings was moderate to very good (k=0.544-0.846) and superior to the radiographic findings (k=0.236-1.000). Overall, the diagnostic accuracy of DTS for the lesion detection was significantly better than with radiography (all p<0.05, except that for the comparison of diagnostic accuracy of DTS versus radiographic detection of left diaphragmatic plaques and asbestosis). DTS was more sensitive than radiography for the detection of asbestosis (82% versus 27%, p=0.031). DTS is more accurate than radiography in the detection of pleural plaques and more sensitive than radiography in the detection of asbestosis. Interobserver agreements with respect to the DTS findings were superior to the radiographic findings.

P125 Digital Measurement Strategy is Robust in Non-Expert Hands in Measuring Clinically Relevant Effusions on Chest Radiograph

IntroductionThe primary outcome of most studies investigating pleural infection treatment is the pleural effusion volume change between two defined time points. This may be performed using thoracic computed tomography (CT)...

P124 Effusion Size on the Chest Radiograph at Day 7 Post-Pleural Drainage is a Good Predictor of Size at 3 Months, Regardless of Initial Intrapleural Therapy

IntroductionDrainage of infection pleural fluid is essential in improving patient outcomes. The MIST-2 Trial (NEJM 2011) demonstrated intrapleural tissue plasminogen activator (t-PA) and DNase therapy improves drainage in patients with...

An image‐based technique to assess the perceptual quality of clinical chest radiographs

Current clinical image quality assessment techniques mainly analyze image quality for the imaging system in terms of factors such as the capture system modulation transfer function, noise power spectrum, detective quantum efficiency, and the exposure technique. While these elements form the basic underlying components of image quality, when assessing a clinical image, radiologists seldom refer to these factors, but rather examine several specific regions of the displayed patient images, further impacted by a particular image processing method applied, to see whether the image is suitable for diagnosis. In this paper, the authors developed a novel strategy to simulate radiologists' perceptual evaluation process on actual clinical chest images. Ten regional based perceptual attributes of chest radiographs were determined through an observer study. Those included lung grey level, lung detail, lung noise, rib-lung contrast, rib sharpness, mediastinum detail, mediastinum noise, mediastinum alignment, subdiaphragm-lung contrast, and subdiaphragm area. Each attribute was characterized in terms of a physical quantity measured from the image algorithmically using an automated process. A pilot observer study was performed on 333 digital chest radiographs, which included 179 PA images with 10:1 ratio grids (set 1) and 154 AP images without grids (set 2), to ascertain the correlation between image perceptual attributes and physical quantitative measurements. To determine the acceptable range of each perceptual attribute, a preliminary quality consistency range was defined based on the preferred 80% of images in set 1. Mean value difference (μ(1) - μ(2)) and variance ratio (σ(1) (2)/σ(2) (2)) were investigated to further quantify the differences between the selected two image sets. The pilot observer study demonstrated that our regional based physical quantity metrics of chest radiographs correlated very well with their corresponding perceptual attributes. The distribution comparisons, mean value difference estimations, and variance ratio estimations of each physical quantity between sets of images from two different techniques matched our expectation that the image quality of set 1 should be better than that of set 2. The measured physical quantities provide a robust reflection of perceptual image quality in clinical images. The methodology can be readily applied for automated evaluation of perceptual image quality in clinical chest radiographs.

Unbiased Review of Digital Diagnostic Images in Practice: Informatics Prototype and Pilot Study

Clinical and contextual information associated with images may influence how radiologists draw diagnostic inferences, highlighting the need to control multiple sources of bias in the methodologic design of investigations involving radiologic interpretation. In the past, manual control methods to mask review films presented in practice have been used to reduce potential interpretive bias associated with differences between viewing images for patient care and reviewing images for the purposes of research, education, and quality improvement. These manual precedents from the film era raise the question whether similar methods to reduce bias can be implemented in the modern digital environment.A prototype application, CreateAPatient, was built for masking review case presentations within one institution's production radiology information system and picture archiving and communication system. To test whether CreateAPatient could be used to mask review images presented in practice, six board-certified radiologists participated in a pilot study. During pilot testing, seven digital chest radiographs, known to contain lung nodules and associated with fictitious patient identifiers, were mixed into the routine workloads of the participating radiologists while they covered general evening call shifts. The aim was to test whether it was possible to mask the presentation of these review cases, both by probing the interpreting radiologists to report detection and by conducting a forced-choice experiment on a separate cohort of 20 radiologists and information technology professionals.None of the participating radiologists reported awareness of review activity, and forced-choice detection was less than predicted at chance, suggesting that radiologists were effectively blinded. In addition, no evidence was identified of review reports unsafely propagating beyond their intended scope or otherwise interfering with patient care, despite integration of these records within production electronic work flow systems.Information technology can facilitate the design of unbiased methods involving professional review of digital diagnostic images.

Active case finding for pulmonary tuberculosis using mobile digital chest radiography: an observational study

Mobile digital chest radiography (CXR) is used routinely to screen for pulmonary tuberculosis (PTB) in London among homeless populations, persons accessing drug treatment services and prisoners. 1) To establish the sensitivity and specificity of mobile digital CXR, and 2) to test the hypothesis that actively identified cases have reduced odds of sputum smear positivity vs. those presenting passively to health care services from the same populations. Sensitivity and specificity were calculated using a gold standard comparator of culture-confirmed cases of PTB reported to the national surveillance system within 90 days of screening. Logistic regression was used to determine whether actively detected cases had reduced odds of smear positivity compared to passively detected cases after adjustment for confounding. The intervention had a sensitivity of 81.8% (95%CI 64.5-93.0) and a specificity of 99.2% (95%CI 99.1-99.3). After adjusting for confounding, there was evidence that cases identified through screening were less likely to be smear-positive than passively identified cases (OR 0.34, 95%CI 0.14-0.85; likelihood ratio test P = 0.022). Digital CXR achieves a high level of sensitivity and specificity in an operational setting; targeted mobile radiographic screening can reduce the risk of onward transmission by identifying cases before they become infectious.

Dose Optimization for Different Medical Imaging Tasks From Exposure Index, Exposure Control Factor, and mAs in Digital Radiography

In radiographic examination, not all medical imaging tasks require the same level of image quality or diagnostic information. Criteria should be established for different imaging tasks to avoid excessive doses where there is no clear net benefit in the diagnosis or the image quality. An exposure index provided by manufacturers would be a useful tool for this purpose. This study aims to establish an optimum exposure index to be used as a guideline for clinical imaging tasks to minimize radiation exposure for chest digital radiography. A three-level classification of image quality (high, medium, and low) for chest imaging tasks was carried out. An anthropomorphic phantom was employed to establish minimum exposure index and exposure (mAs) for clinical imaging task type I (corresponding to high image quality). The exposures of medium and low quality images derived from it. Thirty patients were exposed consecutively with these optimized exposure factors, and clinical tasks were considered, while another 30 patients were exposed with the exposure factors routinely used in practice. Image quality was assessed objectively by a consensus panel. The optimized exposure provided a significant reduction of the mean exposure index from 1,556 to 1,207 (p < 0.0001) and mean patient's entrance surface dose from 0.168 mGy to 0.092 mGy (p < 0.0001). The results show that a clinical-task-determined radiographic procedure is more conducive to radiation protection of patients. In this study, the posteroanterior chest imaging examination was chosen as an example. This procedure can also apply to other body parts and views.

Investigation of the Variability in the Assessment of Digital Chest X-ray Image Quality

A large database of digital chest radiographs was developed over a 14-month period. Ten radiographic technologists and five radiologists independently evaluated a stratified subset of images from the database for quality deficiencies and decided whether each image should be rejected. The evaluation results showed that the radiographic technologists and radiologists agreed only moderately in their assessments. When compared against each other, radiologist and technologist reader groups were found to have even less agreement than the inter-reader agreement within each group. Radiologists were found to be more accepting of limited-quality studies than technologists. Evidence from the study suggests that the technologists weighted their reject decisions more heavily on objective technical attributes, while the radiologists weighted their decisions more heavily on diagnostic interpretability relative to the image indication. A suite of reject-detection algorithms was independently run on the images in the database. The algorithms detected 4 % of postero-anterior chest exams that were accepted by the technologist who originally captured the image but which would have been rejected by the technologist peer group. When algorithm results were made available to the technologists during the study, there was no improvement in inter-reader agreement in deciding whether to reject an image. The algorithm results do, however, provide new quality information that could be captured within a site-wide, reject-tracking database and leveraged as part of a site-wide QA program.

How reliable and safe is full-body low-dose radiography (LODOX Statscan) in detecting foreign bodies ingested by adults?

ObjectiveForeign body ingestion is common and potentially lethal. This study evaluates the use of low-dose Statscans (LODOX) in emergency departments.DesignThis comparative cross-sectional study retrospectively assessed 28 289 digital chest x-rays...

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.