CsI-detector-based dual-exposure dual energy in chest radiography for lung nodule detection: results of an international multicenter trial

To assess both sensitivity and specificity of digital chest radiography alone and in conjunction with dual-exposure dual-energy chest radiography for the detection and classification of pulmonary nodules. One hundred patients with a total of 149 lung nodules (3-45 mm; median, 11 mm) confirmed by CT were included in this study. Dual-exposure dual-energy chest radiographies of each patient were obtained using a CsI detector system. Experienced board-certified chest radiologists from four different medical centers in Europe reviewed standard chest radiographs alone and in conjunction with dual-energy images blinded and in random order. The reviewers rated the probability of presence, calcification and malignancy of all lung nodules on a five-point rating scale. Lesions detected were identified by applying a specific coordinate system to enable precise verification by the study leader. A receiver-operating characteristic (ROC) analysis was performed. In addition to the 149 true-positive CT proven lesions, 236 false-positive lung nodules were described in digital chest radiographies in conjunction with dual-energy chest radiographies. The cumulative sensitivity of chest radiography in conjunction with dual energy was 43%, specificity was 55%. For digital radiography alone, sensitivity was 35% and specifity was 83%. For the dual energy system, positive predictive value was 58%, and negative predictive value was 66% compared to the digital radiography with a positive predictive value of 59% and a negative predictive value of 65%. Areas under the curve in a ROC analysis resulted in 0.631 (95% confidence interval =0.61 to 0.65) for radiography with dual energy and 0.602 (95% confidence interval =0.58 to 0.63) for digital radiography alone. This difference was not statistically significant. For the detection of lesion calcification or the determination of malignancy, ROC analysis also failed to show significant differences. CsI-based flat-panel dual-exposure dual-energy imaging added to standard chest radiography did not show statistically significant improvement for the detection of pulmonary nodules, nor the identification of calcifications, nor the determination of malignancy.     

Simulated pulmonary nodules: detection with dual-energy digital versus conventional radiography

Performance of a prototype dual-energy digital chest radiography unit in detecting calcified and noncalcified simulated pulmonary nodules was compared with that of a highly optimized, conventional system. Nodules ranging in size (0.5, 1.0, and 1.6 cm), in number (five to 11), and in calcium content (0-25 mg) were superimposed over the lungs of a frozen, unembalmed, human chest phantom. For each technique, six observers examined 50 posteroanterior projections with different randomized nodule locations. Detection consisted of locating and assigning a level of confidence to each perceived nodular opacity. The resulting plots of the true-positive fraction versus the mean number of false-positive calls per projection indicate that for both calcified and noncalcified nodules, the digital unit performed significantly better (P less than .01).     

Digital imaging and picture archiving and communication systems

Great progress has been made in digital imaging of the chest. Most studies are dealing with computed radiography. Chest radiography in the intensive care unit may, in most cases, be performed using computed radiography. However, subtle pulmonary interstitial disease can be demonstrated less confidently using computed radiography. Significantly better detection of calcified lung nodules can be obtained by using simplified single-exposure dual-energy technique that uses storage phosphor. The wide latitude of computed radiography permits images of high quality in areas other than chest radiography. Encouraging results are presented especially in the diagnostic evaluation of scoliosis and other musculoskeletal abnormalities. An important technical innovation in digital radiography is an improved method for single-exposure dual-energy digital imaging using prefiltration with gadolinium, a cassette consisting of four photostimulable phosphor plates, spatially dependent scatter and beam hardening corrections, and noise reduction algorithm. Other groups tested algorithms for enhancement of digital images that allowed significant data compression. The implementation of picture archiving and communication systems (PACS) is inevitable; the question concerning PACS implementation is not why, but when. A comparison of the cost-effectiveness of PACS with conventional film archiving and communication systems shows that PACS should provide indirect savings when regarding the hidden costs of conventional systems. Much more experience will be needed before there is general agreement on the best design for the radiologist's workstation. Teleradiology should contribute to radiologic consultation for remote locations, because it improves the efficacy of management of patients in such locations.     

Detectability of lung nodules using flat panel detector with dual energy subtraction by two shot method: evaluation by ROC method

The aim of this study was to evaluate the effectiveness of dual-exposure dual energy subtraction technique in flat-panel chest radiography for lung nodules detection. Chest radiographs were acquired in 100 patients (57 men and 43 women; mean age, 60.2 years; range, 18-89 years) using a flat-panel digital chest system. These images were evaluated by seven radiologists. A continuous rating scale of 0-100 was used to represent each observer's confidence level regarding the presence or absence of lung nodules. Observer performance for detection of lung nodules with subtraction images was tested by using receiver operating characteristic (ROC) analysis of individual and averaged reader data. The average area under the ROC curve (Az value) significantly increased with subtraction images (Az=0.79 in standard radiographs versus Az=0.84 with subtraction images, p<0.05). In conclusion, the two-exposure dual-energy subtraction chest radiography significantly would improve detection of lung nodules.     

Clinical evaluation of pulmonary nodules with dual-exposure dual-energy subtraction chest radiography

PURPOSE: The purpose of this study was to assess the effect of dual-exposure dual-energy (DE) subtraction chest radiography with flat-panel detector. MATERIALS AND METHODS: One hundred patients underwent dual-exposure DE subtraction chest radiography and chest CT for evaluation of pulmonary nodules. Fifty-two patients with pulmonary nodules and 48 patients with normal lungs were selected for receiver operating characteristic (ROC) curve analysis. Ten radiologists who were unaware of the CT results evaluated chest radiography alone and chest radiography with DE subtraction images in the detection of pulmonary nodules. For each radiologist, we calculated the areas under the ROC curve (Az) for chest radiography alone and chest radiography with DE subtraction images. RESULTS: The average detectability of dual-exposure DE subtraction chest radiography was statistically significantly higher than that of chest radiography without subtraction images (mean Az value increased from 0.784 to 0.815, p<0.001). CONCLUSION: Dual-exposure DE subtraction chest radiography improves diagnostic accuracy of pulmonary nodules.     

High frequency edge enhancement in the detection of fine pulmonary lines. Parity between storage phosphor digital images and conventional chest radiography

Fine linear structures represent a severe test of the minimum spatial resolution that is needed for digital chest imaging. We studied the comparative observer performance of storage phosphor digital imaging (1760 X 2140 pixel matrix, 10 bits deep), and conventional radiography (Lanex medium screen, Ortho C film) in the detection of simulated fine pulmonary lines superimposed on the normal chest when exposure factors were identical (20mR skin entrance dose at 141 kVp). Receiver operating characteristics analysis of 2160 observations by six readers found that high frequency edge-enhanced digital images (ROC area: 0.78 +/- 0.06) performed better than unenhanced digital images (ROC area: 0.70 +/- 0.07) (P less than 0.01 for paired t-test), and that edge enhanced digital images performed on a par with conventional radiography (ROC area: 0.78 +/- 0.09). We conclude that for the detection of fine linear structures, storage phosphor digital images can perform on a par with higher resolution conventional chest radiographs when a high frequency edge-enhancement algorithm is employed.     

Screening for asbestos-related pleural disease with digital storage phosphor radiography

Digital storage phosphor radiography (SR) has a wide dynamic range and unique postprocessing capabilities that may improve the performance of screening studies for asbestos-related pleural disease compared with conventional film radiography (FR). In a group of 32 asbestos-exposed and nine control subjects with established pleural data, we compared the screening performance of FR and SR obtained with a single isoexposure, dual-energy technique (system resolution 0.2 mm, 10 bits). Performance was evaluated for 7320 observations by eight readers using a paired t test (P less than .02 with Bonferroni correction) of averaged receiver operating characteristic curve (ROC) areas (Az +/- standard error). We found that SR alone and SR supplemented by dual-energy soft-tissue and calcium images (SRde) were superior to FR in the overall detection of pleural abnormalities (Az = 0.90 +/- 0.01, 0.90 +/- 0.01, and 0.88 +/- 0.01, respectively). In the specific detection of pleural calcification, SRde was superior to FR (Az = 0.91 +/- 0.01 and 0.87 +/- 0.01, respectively; P less than 0.01). Analysis of variance indicated that SRde most closely reproduced an established pleural score based on the International Labor Organization (ILO) classification of the pneumoconioses (P less than 0.05, Scheffé's multiple comparison test). We conclude that isodose SR performs at least as well as FR in screening for asbestos-related pleural disease. SR supplemented by dual-energy images might improve the specific detection of pleural calcifications compared with FR.     

Detection of simulated pulmonary nodules by single-exposure dual-energy computed radiography of the chest: effect of a computer-aided diagnosis system (Part 2)

OBJECTIVE: To evaluate the performance of the computer-aided diagnosis (CAD) scheme on the detection of pulmonary nodules (PNs) in single-exposure dual-energy subtraction computed radiography (CR) images of the chest, and to evaluate the effect of this CAD scheme on radiologists' detectibilaties. METHODS AND MATERIAL: We compared the detectability by the CAD scheme with the detectability by 12 observers by using conventional CR (C-CR) and bone-subtracted CR (BS-CR) images of 25 chest phantoms with a low-contrast nylon nodule. RESULTS: Both in the CAD scheme and for the observers, the detectability of BS-CR images was superior to that of C-CR images (P<0.005). The detection performance of the CAD scheme was equal to that of the observers. The nodules detected by the CAD did not necessarily coincide with those by the observers. Thus, if observers can use the results of the CAD system as a 'second opinion', their detectabilities increase. CONCLUSION: The CAD system for detection of PNs in the single-exposure dual-energy subtraction method is promising for improving radiologists' detectabilities of PNs.     

双能量数字减影胸片对于不同肺野区域内结节性病变的检出差异(ROC分析)

目的　评价双能量数字减影胸片和常规DR胸片对于不同肺野区域内结节性病变的检出差异。方法　 2 0名正常成年志愿者前胸粘贴模拟结节 ,拍摄双能量数字减影正位胸片 ,应用ROC分析比较常规DR胸片与减影后软组织图像的诊断结果。结果　在双上、中肺野 ,软组织图像的曲线下面积大于常规DR胸片 ;在双上肺野、双中肺野外带 2种方法具有显著性差异。结论　双能量数字减影技术对双上肺野及双中肺野外带胸部结节性病变的检出具有优势 ,故应结合减影及常规胸片 ,以助诊断。     

Evaluation of improvement of the detection of interstitial lung diseases by using the dual-energy subtraction radiography method of a flat-panel detector system

We investigated and evaluated the detection of simulated lesions in various interstitial lung diseases using the dual-energy subtraction radiography method and flat-panel detector (FPD) images. We obtained a FPD system (GE Revolution XR/d), and employed dual-energy 60 kV and 130 kV exposure techniques. Three types of lung lesions, namely, micro-nodule, ground-glass, and honeycomb patterns were simulated with interstitial lung disease on a chest phantom. Chest images with and without simulated lesions were exposed and compared with standard images and subtraction images. We carried out evaluations with and without subtraction images and performed the analysis by using receiver operating characteristic (ROC) analysis of detection. Results showed that the detection of interstitial lung diseases was significantly improved by the use of subtraction images. The area under the ROC curve (AUC) values of micro-nodule images obtained with and without subtraction images were 0.768 and 0.963, ground-glass images 0.670 and 0.917, and honeycomb images 0.768 and 0.996, respectively. A significant difference of p<0.05 was accepted. The use of dual-energy subtraction radiography with a FPD improved diagnostic accuracy in detecting cases of multiple interstitial lung diseases and was considered useful.     

Advanced multiple beam equalization radiography (AMBER) in the detection of diffuse lung disease

To evaluate the effects of scanning equalization radiography (SER) on the detection of diffuse lung disease a clinical comparison between an Advanced Multiple Beam Equalization Radiography (AMBER) unit and conventional chest radiography was performed. Even though the overall detection of focal pulmonary lesions with the AMBER unit has been shown to be significantly higher than with conventional radiography because of the improved demonstration of the costophrenic and retrocardiac regions, the utility of AMBER in the demonstration of diffuse lung disease has not been established. Twenty-one patients with diffuse lung disease (fibrosing alveolitis or sarcoidosis) and six patients with no pulmonary disease had high kVp frontal and lateral chest radiographs on both an AMBER unit and a conventional chest stand. The pooled results of five observers using Receiver Operating Characteristic (ROC) analysis indicate that there is a slight improvement but no statistically significant difference in observer performance between AMBER (Area under the ROC curve AZ = 0.934) and conventional radiography (AZ = 0.868) in the task of detecting diffuse lung disease.     

双能减影与数字X线成像诊断肺内孤立性结节ROC曲线评价

目的　比较双能减影 (DES)与数字X线成像 (DR)对肺内孤立性结节及结节内钙化的诊断价值。资料与方法　对 4 0例肺内有孤立性结节和 4 0例肺内无孤立性结节的病例行CT、DR及DES检查。 4位医师分别对两组影像学资料进行评价 ,结果采用受试者操作特征 (ROC)曲线进行统计分析。结果　在发现肺内孤立性结节方面 ,DES组的ROC曲线下面积 (Az =0 .94 0 )大于DR组 (Az =0 .891) ,两者统计学具有显著性差异 (P <0 .0 5 ) ;在发现肺内孤立性结节内钙化方面 ,DES组的ROC曲线下面积 (Az=0 .90 2 )大于DR组 (Az=0 .82 8) ,两者统计学具有显著性差异 (P <0 .0 5 )。结论　DES在发现肺内孤立性结节及钙化方面优于DR ,是对DR检查的有利补充     

Screening for tracheobronchial diseases with digital storage phosphor radiography]

Digital storage phosphor radiography (FCR: Fuji computed radiography) has a wide dynamic range and unique postprocessing capabilities. This study was designed to test whether chest imaging with FCR and its image processing would increase the accuracy of and confidence in the diagnosis of tracheobronchial abnormalities. In a phantom study, the performance of digital images having the appearance of a conventional chest radiograph was compared with that of a conventional system in detecting simulated tracheobronchial nodules. The digital images of lower kilovoltage (ROC area = 0.647 +/- 0.035) were equivalent to the conventional radiographs (ROC area = 0.620 +/- 0.028). On the other hand, nodule detectability was significantly improved in the digital images of higher kilovoltage (ROC area = 0.826 +/- 0.020). The author also compared the impact of five postprocessing algorithms (standard image, wide latitude image, enhanced image, reversed image, and subtraction image). ROC analysis indicated that the default standard image (ROC area = 0.826 +/- 0.020) was as good as an image with a linear rather than a sigmoid gradation curve (ROC area = 0.843 +/- 0.020), an image with strong enhancement of high frequencies (ROC area = 0.804 +/- 0.020), and an image with reversed gray scale polarity (ROC area = 0.775 +/- 0.015). Therefore these specific algorithms had no effect on the detection of tracheobronchial nodules. However, digital subtraction soft tissue images (ROC area = 0.961 +/- 0.030) were significantly better than the control images. Clinical study also indicated that subtraction images improve diagnostic accuracy in tracheobronchial diseases.     

A comparison of dual-energy digital radiography and screen-film imaging in the detection of subtle interstitial pulmonary disease

An ROC study is described which compares the performance of three types of images--conventional screen-film, single-energy digital and dual energy bone cancelled (soft tissue) digital--in detecting subtle interstitial pulmonary disease. Marginally detectable nodular and reticulonodular patterns (12 different patterns of each) were superimposed over the lungs of a frozen human chest phantom to simulate the clinical situation. The digital images were formatted on film at full size (ie, 35 cm X 43 cm). A total of 156 images (52 of each type, of which 28 were normal and 24 had simulated pathology) were used in the study and read by five experienced chest radiologists. Using a paired t-test, the areas under the individual ROC curves were compared for three combinations of images--single-energy digital and conventional, soft tissue digital and conventional, and soft tissue and single-energy digital. No statistically significant difference was observed between the conventional and single-energy digital images. The readers performed better with both conventional and single-energy digital images than with the soft tissue digital images at statistically significant levels (P = 0.05 for conventional vs. soft tissue digital and P = 0.02 for single-energy digital vs. soft tissue digital). The results suggest that there is no advantage in employing dual-energy soft tissue images to assist in diagnosing interstitial disease in the clinical setting. They also suggest that spatial resolution requirements are less demanding in digital chest systems that obtain scatter-free images than in digital systems utilizing conventional scatter control techniques.     

Metastatic calcification of the heart and lungs in end-stage renal disease: detection and quantification by dual-energy digital chest radiography

Metastatic calcification of the lung and heart can cause severe cardiopulmonary compromise and death. Although it is found in most end-stage renal disease patients at autopsy, it is only rarely detected during life. Using a prototype dual-energy digital chest radiographic unit, we measured calcium content (mg/cm2) over the lung and heart in 32 hemodialysis patients. Pulmonary calcium content was significantly greater in these patients than in sex-matched control subjects (men, 230 +/- 43 [mean +/- standard error] vs 166 +/- 7, p less than .05; women, 168 +/- 19 vs 110 +/- 7.5, p less than .001). Abnormal values were detected by dual-energy radiography in 44% of patients (vs 9% of patients studied by conventional radiography). Cardiac calcium content was also significantly greater in the hemodialysis patients than in the control subjects (259 +/- 14 vs 184 +/- 8, p less than .05). Metastatic calcification was significantly correlated with elevated phosphate and calcium-phosphate product levels. Patients with significantly elevated pulmonary calcium content had evidence of restrictive lung disease by functional testing. There was an inverse correlation between elevated cardiac calcium content and ejection fraction. We conclude that dual-energy digital radiography allows premortem diagnosis of metastatic visceral calcification and is more sensitive than current techniques.     

Low-voltage digital selenium radiography: detection of simulated interstitial lung disease, nodules, and catheters--a phantom study

PURPOSE: To compare three tube voltages in digital selenium radiography for the detection of simulated interstitial lung disease, nodules, and catheters. MATERIALS AND METHODS: Simulated catheters, nodules, and ground-glass, linear, miliary, and reticular patterns were superimposed over an anthropomorphic chest phantom. Digital selenium radiography was performed with different tube voltages (70, 90, and 150 kVp). Hard-copy images were generated. Detection performance of five radiologists was compared by using receiver operating characteristic (ROC) analysis involving 54,000 observations. RESULTS: The detection of ground-glass, linear, miliary, and reticular patterns over lucent lung and of nodules equal to, smaller than, and larger than 10 mm increased when 70 kVp and/or 90 kVp was used. However, only the reticular pattern was significantly better detected at lower peak voltage (P <.05). Simulated catheters and nodules over the mediastinum showed smaller areas under the ROC curve at lower peak voltage. These results were not statistically significant (P >.05). CONCLUSION: The diagnostic performance of digital selenium radiography at lower peak voltage is at least as good as that at higher peak voltage for interstitial lung disease over lucent lung. Performance is equivalent for nodules and catheters over obscured chest regions at lower peak voltages compared with that at 150 kVp. Our results implicate that the use of high-voltage technique in digital selenium radiography should be reassessed.     

仰卧位DR双能量减影投照法对阻塞性睡眠呼吸暂停低通气综合征的辅助诊断价值

 目的 探讨仰卧位DR双能量减影投照方法对阻塞性睡眠呼吸暂停低通气综合征(obstructive sleep apnea hypopnea syndrome,OSAHS)辅助诊断价值。方法 收集33例经临床及多导睡眠呼吸监测确诊为OSAHS的患者,所有病例均排除小颌畸形;分别行鼻咽部常规DR摄片和DR双能量减影(DES)摄片,其中DES摄片采用仰卧位。由3位放射诊断医师分别对两组影像学资料中的软腭、悬雍垂及舌根软组织形态,以及导致气道狭窄的情况进行观察和评价,结果采用ROC曲线进行统计分析。结果 在检出软腭后区及舌根后区气道狭窄方面,DES组的ROC曲线下面积分别为医师1(0.921/0.974)、医师2(0.950/0.942)、医师3(0.913/ 0.977),常规DR组为医师1(0.798/0.716)、医师2(0.771/0.583)、医师3(0.632/0.697),DES组均大于常规DR组,差异有统计学意义(P<0.05);在对软腭松弛后坠和舌根后坠的检出率方面,仰卧位DES组也明显高于常规DR组。结论 仰卧位DR双能量减影投照法应用于OSAHS的病因诊断,无论在图像清晰度还是诊断准确性上较常规方法均明显提高,有明确的辅助诊断价值。     

Visual detection and localization of radiographic images.

In conventional receiver-operating-characteristic (ROC) curve analysis of visual detection performance, the observer is credited with a true-positive response if a visual signal is present somewhere in a radiograph called "positive" by the observer; however, the measured true-positive rate can be different for a given false-positive rate if the observer is required to identify the correct location of the visual signal in order to receive credit for a true-positive response. The authors describe and have confirmed experimentally a model which can be used to predict observer performance in an experiment requiring both detection and localization on the basis of the conventional ROC curve determined in a detection experiment. Implications for the use of signal detection theory in the assessment of radiographic image quality are discussed.     

Computerized detection of pulmonary nodules by single-exposure dual-energy computed radiography of the chest (part 1)

OBJECTIVE: To clarify the usefulness of computerized detection of pulmonary nodules (PNs) in single-exposure dual-energy subtraction computed radiography (CR) images of the chest. METHODS AND MATERIAL: Our scheme uses bone-subtracted CR (BS-CR) images, and consists of a contrast-adaptive filter for detection of the candidates for PNs and a vessel-enhancing filter for elimination of vessel opacities in the candidates for PNs. For the evaluation, 12 clinical cases with multiple PNs were used, and four radiologists participated in this study. RESULTS: The detectability of our computer-aided diagnosis (CAD) was compared with detectabilities of radiologists. The mean true-positive (TP) number of four radiologists was 1.60+/-1.03, and that of the CAD was 1.83+/-1.34. There was no significant difference in the nodule detectabilities between the radiologists and CAD (P=0.18). However, the false-positive (FP) rate of the CAD was 9.42+/-2.54 per image, whereas the mean FP rate of the radiologists was 1.40+/-0.64 per image. CONCLUSION: Computerized detection of PNs is considered to be useful in the determination of radiological diagnoses. However, reducing the number of FP findings remains an important problem to be solved.     

Image-intensifier photofluorography and conventional chest radiography: comparison of diagnostic efficacy

Photofluorography with a large image intensifier, which provides an image field of 40 x 40 cm, reduces both the radiation dose and the imaging costs in chest radiography as compared with the film-screen technique. The two techniques were evaluated in a clinical study of 135 patients with suspected chest abnormalities. Photofluorographs and film-screen chest radiographs were interpreted independently by three radiologists. The diagnoses were confirmed by CT, follow-up radiographs, and clinical records. Among the 135 patients, 75 had primary lung cancer, 39 had pulmonary nodules, 52 had hilar or mediastinal abnormalities, 17 had pleural fluid, and 45 had pneumonic or atelectatic changes. Twenty-three normal subjects were included. Differences in diagnostic accuracy, measured by sensitivity and specificity, were not statistically significant. A larger number of true-positive cases (65%) with peripheral lung nodules were found by photofluorography than by film-screen radiography (54%) (p less than .05). The results suggest that the diagnostic accuracy of chest images made by photofluorography is sufficient to warrant using it instead of the film-screen technique in routine chest radiography, especially to detect lung tumors and metastases.