移动CR与移动DR在床旁胸部摄影中的应用比较

目的对比研究移动计算机X射线摄影（CR）与移动数字化X射线摄影（DR）在床旁胸部摄影中的临床应用价值。方法随机抽取移动CR与移动DR床旁胸部摄影胸片各200张,对2种摄影方式所摄胸片的图像质量及胸内各结构的显示进行对比研究。移动CR和移动DR各200张床旁胸部摄影胸片,以其CT检查为＂金标准＂进行对照,将两组床旁胸片显示的病灶清晰程度分为清晰、可见、模糊、隐约可见、未见5类。统计2组的例数,绘制接受者操作特征（ROC）曲线。结果图像质量：移动CR床旁胸部摄影所得胸片的甲级片率69.0%,乙级片率24.5%,丙级片率5.0%,废片率1.5%。移动DR床旁胸部摄影所得胸片的甲级片率83%,乙级片率16%,丙级片率1%,废片率0。对胸内各结构的显示：移动CR与移动DR床旁胸部摄影所得胸片对胸内各结构的显示率移动CR低于移动DR。对病灶的显示能力：200张移动CR胸片中,126例行CT检查,67例CT所显示的病灶中,移动CR能显示64例,3例未见病灶。200张移动DR胸片中,108例行CT检查,53例CT所显示的病灶中,移动DR能显示52例,1例未见病灶。移动CR与移动DR床旁胸部摄影ROC曲线下的面积分别为0.833和0.918。结论移动CR与移动DR床旁胸部摄影,移动DR摄影的影像质量、对胸内结构的显示及对病灶的显示能力均优于移动CR,在床旁胸部摄影中移动DR具有更高的应用价值。     

Sensitivity of Thoracic Digital Tomosynthesis (DTS) for the Identification of Lung Nodules

Thoracic computed tomography (CT) is considered the gold standard for detection lung pathology, yet its efficacy as a screening tool in regards to cost and radiation dose continues to evolve. Chest radiography (CXR) remains a useful and ubiquitous tool for detection and characterization of pulmonary pathology, but reduced sensitivity and specificity compared to CT. This prospective, blinded study compares the sensitivity of digital tomosynthesis (DTS), to that of CT and CXR for the identification and characterization of lung nodules. Ninety-five outpatients received a posteroanterior (PA) and lateral CXR, DTS, and chest CT at one care episode. The CXR and DTS studies were independently interpreted by three thoracic radiologists. The CT studies were used as the gold standard and read by a fourth thoracic radiologist. Nodules were characterized by presence, location, size, and composition. The agreement between observers and the effective radiation dose for each modality was objectively calculated. One hundred forty-five nodules of greatest diameter larger than 4 mm and 215 nodules less than 4 mm were identified by CT. DTS identified significantly more >4 mm nodules than CXR (DTS 32 % vs. CXR 17 %). CXR and DTS showed no significant difference in the ability to identify the smaller nodules or central nodules within 3 cm of the hilum. DTS outperformed CXR in identifying pleural nodules and those nodules located greater than 3 cm from the hilum. Average radiation dose for CXR, DTS, and CT were 0.10, 0.21, and 6.8 mSv, respectively. Thoracic digital tomosynthesis requires significantly less radiation dose than CT and nearly doubles the sensitivity of that of CXR for the identification of lung nodules greater than 4 mm. However, sensitivity and specificity for detection and characterization of lung nodules remains substantially less than CT. The apparent benefits over CXR, low cost, rapid acquisition, and minimal radiation dose of thoracic DTS suggest that it may be a useful procedure. Work-up of a newly diagnosed nodule will likely require CT, given its superior cross-sectional characterization. Further investigation of DTS as a diagnostic, screening, and surveillance tool is warranted.     

Interpretation of subtle interstitial chest abnormalities: Conventional radiography versus high-resolution storage-phosphor radiography—A preliminary study

To evaluate the reliability of digital chest radiography in diagnosing subtle interstitial lung abnormalities, we performed several clinical studies including a comparison of conventional screen-film radiography and storage-phosphor radiography (2 K × 2 K pixels, 10 bit), and a comparison of conventional screen-film radiography and film-digitized radiography (2 K × 2 K pixels, 10 bit). From these previous studies, a spatial resolution of 0.2-mm pixel size was considered inadequate to diagnose subtle interstitial lung diseases. Under these circumstances, the newly developed Fuji Computed Radiography system (FCR 9000; Fuji Photo Film, Tokyo, Japan) has recently become available. This system provides 0.1-mm pixel size (4 K × 5 K pixels, 10-bit depth) and life-size hard copies (14×17 inches). To evaluate the reliability of new high-resolution storagephosphor radiography (FCR 9000) in diagnosing simulated subtle interstitial abnormalities (including simulated lines, micronodules, and groundglass opacities), the differences among radiologists in interpreting conventional screen-film radiographs and life-size high-resolution storage-phosphor radiographs were studied. Observation was made by eight experienced chest radiologists, and receiver-operating characteristic (ROC) analysis was performed. There was no significant difference in detecting in subtle simulated interstitial abnormalities between conventional film-screen radiography and high-resolution storage-phosphor radiography. For all three types of abnormalities, there was no significant difference between conventional and storage-phosphor radiography. In conclusion, the high-resolution storage-phosphor chest radiography (0.1-mm pixel size, 10-bit depth) may be substituted for conventional chest radiography in the detection of subtle interstitial abnormalities.     

Impact of resolution and noise characteristics of digital radiographic detectors on the detectability of lung nodules

One of the unanswered questions in digital radiography is the connection between physical image quality metrics and clinical detection performance. In this paper, we examine the impact of two physical metrics, resolution and noise, on the detectability of nodules in a pulmonary background for specific digital radiographic detectors. A detection experiment was performed on a simulated image set using anatomical backgrounds from a high-quality lung radiograph and three different simulated nodule sizes (2-3.5 mm). The resolution and noise of the resulting images were modified using existing routines to simulate a selenium-based and a cesium iodide-based flat-panel detector at comparable exposures. A location-known-exactly (LKE) observer performance experiment was performed in which four experienced chest radiologists and three physicists specializing in chest radiology scored the images. The data from the observer experiment were analyzed by receiver operating characteristic (ROC) methodology. The detectability, as measured by the parameter Az, was higher for the selenium detector than the cesium iodide detector for all nodule sizes by an average of 8.5%. For one nodule size (2.75 mm), the difference between detectors was statistically significant (p < 0.01). The findings indicate that for the particular task studied, the superior resolution performance of the selenium-based detector provided better detectability of subtle lung nodules even though the images had greater noise than images obtained with the cesium iodide detector.     

Quantitative Kinetic Analysis of Lung Nodules Using the Temporal Subtraction Technique in Dynamic Chest Radiographies Performed with a Flat Panel Detector

Early detection and treatment of lung cancer is one of the most effective means of reducing cancer mortality, and to this end, chest X-ray radiography has been widely used as a screening method. A related technique based on the development of computer analysis and a flat panel detector (FPD) has enabled the functional evaluation of respiratory kinetics in the chest and is expected to be introduced into clinical practice in the near future. In this study, we developed a computer analysis algorithm to detect lung nodules and to evaluate quantitative kinetics. Breathing chest radiographs obtained by modified FPD and breath synchronization utilizing diaphragmatic analysis of vector movement were converted into four static images by sequential temporal subtraction processing, morphological enhancement processing, kinetic visualization processing, and lung region detection processing. An artificial neural network analyzed these density patterns to detect the true nodules and draw their kinetic tracks. Both the algorithm performance and the evaluation of clinical effectiveness of seven normal patients and simulated nodules showed sufficient detecting capability and kinetic imaging function without significant differences. Our technique can quantitatively evaluate the kinetic range of nodules and is effective in detecting a nodule on a breathing chest radiograph. Moreover, the application of this technique is expected to extend computer-aided diagnosis systems and facilitate the development of an automatic planning system for radiation therapy.     

Detection of lung nodules in digital chest radiographs using artificial neural networks: A pilot study

Radiologists can fail to detect up to 30% of pulmonary nodules in chest radiographs. A back-propagation neural network was used to detect lung nodules in digital chest radiographs to assist radiologists in the diagnosis of lung cancer. Regions of interest (ROIs) that cantained nodules and normal tissues in the lung were selected from digitized chest radiographs by a previously developed computer-aided diagnosis (CAD) scheme. Different preprocessing techniques were used to produce input data to the neural network. The performance of the neural network was evaluated by receiver operating characteristic (ROC) analysis. We found that subsampling of original 64- × 64-pixel ROIs to smaller 8- × 8-pixel ROIs provides the optimal preprocessing for the neural network to distinguish ROIs containing nodules from false-positive ROIs containing normal regions. The neural network was able to detect obvious nodules very well with an A_z value (area under ROC curve) of 0.93, but was unable to detect subtle nodules. However, with a training method that uses different orientations of the original ROIs, we were able to improve the performance of the neural network to detect subtle nodules. Artificial neural networks have the potential to serve as a useful classifier to help to eliminate the false-positive detections of the CAD scheme.     

A computerized method for automated identification of erect posteroanterior and supine anteroposterior chest radiographs

A computerized scheme was developed for automated identification of erect posteroanterior (PA) and supine anteroposterior (AP) chest radiographs. The method was based on three features, the tilt angle of the scapula superior border, the tilt angle of the clavicle and the extent of radiolucence in lung fields, to identify the view of a chest radiograph. The three indices A(scapula), A(clavicle) and C(lung) were determined from a chest image for the three features. Linear discriminant analysis was used to classify PA and AP chest images based on the three indices. The performance of the method was evaluated by receiver operating characteristic analysis. The proposed method was evaluated using a database of 600 PA and 600 AP chest radiographs. The discriminant performances Az of A(scapula), A(clavicle) and C(lung) were 0.878 ± 0.010, 0.683 ± 0.015 and 0.962 ± 0.006, respectively. The combination of the three indices obtained an Az value of 0.979 ± 0.004. The results indicate that the combination of the three indices could yield high discriminant performance. The proposed method could provide radiologists with information about the view of chest radiographs for interpretation or could be used as a preprocessing step for analyzing chest images.     

Computer-Aided Nodule Detection on Digital Chest Radiography: Validation Test on Consecutive T1 Cases of Resectable Lung Cancer

Purpose To evaluate the usefulness of a commercially available computer-assisted diagnosis (CAD) system on operable T1 cases of lung cancer by use of digital chest radiography equipment. Materials and Methods Fifty consecutive patients underwent surgery for primary lung cancer, and 50 normal cases were selected. All cancer cases were histopathologically confirmed T1 cases. All normal individuals were selected on the basis of chest computed tomography (CT) confirmation and were matched with cancer cases in terms of age and gender distributions. All chest radiographs were obtained with one computed radiography or two flat-panel detector systems. Eight radiologists (four chest radiologists and four residents) participated in observer tests and interpreted soft copy images by using an exclusive display system without and with CAD output. When radiologists diagnosed cases as positives, the locations of lesions were recorded on hard copies. The observers’ performance was evaluated by receiver operating characteristic analysis. Results The overall detectability of lung cancer cases with CAD system was 74% (37/50), and the false-positive rate was 2.28 (114/50) false positives per case for normal cases. The mean A_z value increased significantly from 0.896 without CAD output to 0.923 with CAD output (P = 0.018). The main cause of the improvement in performance is attributable to changes from false negatives without CAD to true positives with CAD (19/31, 61%). Moreover, improvement in the location of the tumor was observed in 1.5 cases, on average, for radiology residents. Conclusion This CAD system for digital chest radiographs is useful in assisting radiologists in the detection of early resectable lung cancer.     

Pulmonary manifestations in Proteus syndrome: pulmonary varicosities and bullous lung disease

We report on two patients with Proteus syndrome (PS), with emphasis on its pulmonary manifestations. The first patient was a 6‐year‐old girl diagnosed with PS at 5 years of age. The pulmonary abnormalities first observed at age 3 years and included streaky densities with accentuated vascular markings detected by chest radiography. The patient had persistent abnormalities on follow‐up chest radiographs. Chest computed tomography (CT) scans showed diffuse pulmonary venous dilatations. The second patient was a 10‐year‐old boy diagnosed with PS at age 4 years. Chest radiography and CT scans showed patchy and streaky densities intermixed with small bullae, which were interpreted as pneumonia with post‐inflammatory pneumatoceles. The patient developed diffuse enlargement of air spaces of the lungs at age 10 years with severe respiratory compromise. Although pulmonary manifestations in PS are uncommon, recognition of pulmonary vein malformation and the presentation of enlarged air spaces in the lungs at an earlier age are important for accurate diagnosis. The plain radiograph findings of accentuated vascular markings seen in patients with PS may appear similar to interstitial or chronic pneumonia. This report emphasizes the features of lung involvement in children with PS and suggests that specific attention be paid to pulmonary manifestations using chest CT scans. © 2011 Wiley‐Liss, Inc.     

Contralateral subtraction: a novel technique for detection of asymmetric abnormalities on digital chest radiographs

A novel contralateral subtraction technique has been developed to assist radiologists in the detection of asymmetric abnormalities on a single chest radiograph. With this method, the lateral inclination is first corrected by rotating and shifting the original chest image so that the midline of the thorax is aligned with the vertical centerline of the original chest image. The rotated image is then flipped laterally to produce a reversed "mirror" image. Finally, the mirror image is warped and subtracted from the original image for derivation of the contralateral subtraction image. The three key techniques which are employed in this study are applied successively to the initial contralateral subtraction technique for acquisition of improved subtraction images. One hundred PA chest radiographs, including 50 normals and 50 abnormals, were used as the database for this study. The percentage of chest images, which were rated as being adequate, good, or excellent quality of subtraction images by employing a subjective evaluation method, was improved from 73% to 91% by use of the three key techniques. The contralateral subtraction technique can be used for detection of any asymmetric abnormalities, such as lung nodules, pneumothorax, pneumonia, and emphysema, on a single chest radiograph, and therefore has potential utility in a high proportion of abnormal cases.     

Digital tomosynthesis of hand joints for arthritis assessment

The two principal forms of hand arthritis, rheumatoid arthritis (RA) and osteoarthritis (OA) have large clinical and economic costs. Radiography has been shown to be a useful tool to assess the condition of the disease. A hand radiograph, however, is a two-dimensional projection of a three-dimensional object. In this report we present the results of a study that applied digital tomosynthesis to hand radiography in order to extract three-dimensional outcome measures that should be more sensitive to arthritis progression. The study was performed using simulated projection radiographs created using micro computed tomography (microCT) and a set of five dry-bone hand skeletons. These simulated projection images were then reconstructed into tomographic slices using the matrix inversion tomosynthesis (MITS) algorithm. The accuracy of the tomosynthesis reconstruction was evaluated by comparing the reconstructed images to a gold standard created using the microCT data. A parameter from image registration science, normalized mutual information, provided a quantifiable figure of merit. This study examined the effects of source displacement, number of reconstructed planes, number of acquisitions, noise added to the gray scale images, and errors in the location of a fiducial marker. We also optimized the reconstruction as a function of two variables k and alpha, that controlled the mixing of MITS with conventional shift-and-add tomosynthesis. A study using hand delineated joint margins demonstrated that MITS images provided a better measurement of average joint space width. We found good agreement between the MITS slices and the true planes. Both joint margins and trabecular structure were visible and the reconstructed slices showed additional structures not visible with the standard projection image. Using hand-delineated joint margins we compared the average joint space width of the gold standard slices to the MITS and projection images. A root-mean square deviation (RMSD), calculated for this comparison, gave RMSDproj = 0.18 mm and RMSDMITS = 0.14 mm for the projection and MITS images, respectively. We have demonstrated the potential of digital tomosynthesis for imaging of the hand to assess arthritic changes. We have also developed a methodology that can be used to optimize the technique and have studied the issues that will control the feasibility of clinical implementation.     

隐蔽的肺部小结节病灶的X线诊断传统与数字化摄影的ROC评价

目的 :对比研究数字化X线摄影和传统X线摄影对发现与正常解剖结构重叠的肺部小结节病灶的诊断价值。方法 :选取 3 0例经手术病理证实的肺部结节病例和 3 0例经CT证实无肺部结节的病例 ,分别摄取传统胸片 (A组 )和数字化胸片 (B组 ) ,由 4位高年资医生和 4位低年资医生分别对以上 60对胸片进行观察 ,结果采用ROC曲线统计法进行统计。结果 :对高年资医生来说 ,数字化胸片 (B组 )得到的ROC曲线下面积 (Az =0 .83 7)大于传统胸片 (Az =0 .82 3 ) ,两者有统计学显著性差异 (P <0 .0 5 ) ;对低年资医生来说 ,数字化胸片 (B组 )得到的ROC曲线下面积 (Az =0 .842 )大于传统胸片 (Az =0 .717) ,两者有统计学显著性差异 (P <0 .0 5 ) ;对所有医生来说 ,数字化胸片 (B组 )得到的ROC曲线下面积 (Az =0 .840 )大于传统胸片 (Az =0 .770 ) ,两者有统计学显著性差异 (P〈0 .0 5 )。结论 :数字化胸片对于发现与正常解剖结构重叠的肺内单发结节病灶优于传统胸片。     

Sensitivity and Specificity of a CAD Solution for Lung Nodule Detection on Chest Radiograph with CTA Correlation

The objective of this research was to determine the sensitivity and specificity of a commercially available computer-aided detection (CAD) system for detection of lung nodule on posterior–anterior (PA) chest radiograph in a varied patient population who are referred to computed tomographic angiogram (CTA) of the chest as a reference standard. Patients who had a PA chest radiograph with concomitant CTA of the chest were included in this retrospective study. The PA chest radiograph was analyzed by a CAD device, and results were recorded. A qualitative assessment of the CAD results was performed using a 5-point Likert scale. The CTA was then reviewed to determine if there were correlative nodules. The presence of a correlative nodule between 0.5 cm and 1.5 cm was considered a positive result. The baseline sensitivity of the system was determined to be 0.707 (95% CI = 0.52–0.86), with a specificity of 0.50 (95% CI = 0.38–0.76). Positive predictive value was 0.30 (95% CI = 0.24–0.49), with a negative predictive value of 0.858 (95% CI = 0.82–0.95), and accuracy of 0.555 (95% CI = 0.40–0.66). When excluding nodules that were qualitatively determined by a thoracic radiologist to be false positives, the specificity was 0.781 (95% CI = 0.764–0.839), the positive predictive value was 0.564 (95% CI = 0.491–0.654), the negative predictive value was 0.829 (95% CI = 0.819–0.878), and the accuracy was 0.737 (95% CI = 0.721–0.801). The use of CAD for lung nodule detection on chest radiograph, when used in conjunction with an experienced radiologist, has a very good sensitivity, specificity, and accuracy.     

A comparison of conventional screen-film radiography and hard copy of computed radiography in full and two-thirds sizes in detection of interstitial lung disease

This study examined whether hard-copy radiographs produced from computed radiography (CR) images show the subtle interstitial pulmonary disease equally well to conventional screen-film radiographs, because a digital radiography should be chosen for introduction of the digital picture archiving and communication system (PACS) for the new Osaka University Hospital.^1,2 Eleven radiologists examined 20 abnormal and 20 control chest radiographs presented in each of three groups: conventional screen-film radiographs and two sizes of hard-copy radiographs made from CR images. This study of digital image quality of chest examinations found that some findings on conventional screen-film radiography images are not reproduced by current CR (2,000×2,000×10 bits in matrix), especially when the experienced radiologists were observed. This finding suggested improvements are needed in CR before CR of chest should fully replace conventional screen-film radiography.     

Leydig cell tumor with lung metastasis diagnosed by lung biopsy

Leydig cell tumors are very rare and account for only 3% of testicular tumors and are generally benign. Only less than 0.2% of all testicular cancers were evidenced by metastatic spread. We report a 34-year-old man visited hospital because of coughing sputum mixed with blood. His chest CT showed bilateral patch clouding opacity. He was suspected with allergic alveolitis and treated with methylprednisolone. However, his symptoms and general condition deteriorated, and he visited our hospital. He had no abnormal findings on physical examination. A chest radiograph showed pneumonia in whole lung and CT showed multiple nodules and diffused ground glass opacities in both lung fields. Lung biopsy confirmed a diagnosis of Leydig cell tumor with lung metastasis. The diagnosis is based on the histopathology and immunohistochemistry.     

Extraction of the Two-Dimensional Cardiothoracic Ratio from Digital PA Chest Radiographs: Correlation with Cardiac Function and the Traditional Cardiothoracic Ratio

The purpose of our study was to extract the two-dimensional (2D) cardiothoracic ratio from digital chest radiographs using image analysis software on a Magic View 300 system. We also wanted to investigate its correlation with cardiac function, as defined by left ventricular ejection fraction from MUGA scanning, and with the traditional one-dimensional cardiothoracic ratio. One hundred patients undergoing radionuclide ventriculography and concurrent digital PA chest radiography using a commercial selenium detector system were studied. The 2D cardiothoracic ratio was extracted by defining a region of interest around the cardiac and thoracic areas and calculating a ratio of the two pixel counts obtained. The one-dimensional cardiothoracic ratio was calculated in the traditional manner. Regression analysis was used to study the association between these ratios and the ejection fraction. The 2D ratio could be achieved on all radiographs after image manipulation. The traditional linear cardiothoracic ratio showed an inverse correlation with left ventricular ejection fraction (r = –0.45). The 2D cardiothoracic ratio showed an improved correlation (r = –0.52). Assuming that a left ventricular ejection fraction of 55% or more indicates normal cardiac function, the normal 2D cardiothoracic ratio is 0.23 or less and a ratio of 1:4 is suggested. The ratio of cardiac and thoracic area correlates better with cardiac function as assessed by left ventricular ejection fraction than the traditional linear cardiothoracic ratio. Two-dimensional cardiothoracic ratio is easily extracted and improves the data yield from digital PA chest radiographs on PACS systems.     

Comparison of an amorphous silicon/cesium iodide flat-panel digital chest radiography system with screen/film and computed radiography systems--a contrast-detail phantom study.

Flat-panel (FP) based digital radiography systems have recently been introduced as a new and improved digital radiography technology; it is important to evaluate and compare this new technology with currently widely used conventional screen/film (SF) and computed radiography (CR) techniques. In this study, the low-contrast performance of an amorphous silicon/cesium iodide (aSi/Csl)-based flat-panel digital chest radiography system is compared to those of a screen/film and a computed radiography system by measuring their contrast-detail curves. Also studied were the effects of image enhancement in printing the digital images and dependence on kVp and incident exposure. It was found that the FP system demonstrated significantly better low-contrast performance than the SF or CR systems. It was estimated that a dose savings of 70%-90% could be achieved to match the low-contrast performance of the FP images to that of the SF images. This dose saving was also found to increase with the object size. No significant difference was observed in low-contrast performances between the SF and CR systems. The use of clinical enhancement protocols for printing digital images was found to be essential and result in better low-contrast performance. No significant effects were observed for different kVps. From the results of this contrast-detail phantom study, the aSi/CsI-based flat-panel digital chest system should perform better under clinical situations for detection of low-contrast objects such as lung nodules. However, proper processing prior to printing would be essential to realizing this better performance.     

Pulmonary air cysts in cystic fibrosis: relation of pathologic features to radiologic findings and history of pneumothorax

One lung obtained from each of 21 consecutive autopsies in adolescents and young adults with cystic fibrosis was studied prospectively by macroscopic morphometry and light microscopy to determine the prevalence, morphology, and radiographic appearance of subpleural air cysts, which potentially contribute to spontaneous pneumothorax. In 15 lungs, 41 cysts of three anatomic types were identified: bronchiectatic cysts (23), interstitial cysts (13), and emphysematous bullae (5). All cysts were significantly more numerous in the upper lobe. Bronchiectatic cysts had the largest mean diameter, occupied from less than 1 per cent to 47.7 per cent of upper lobe volume in nine patients, and produced large multiloculated hyperlucencies on chest radiographs in five cases. All six lungs with prior pneumothorax contained at least one cyst, but no significant difference was found in the type or proportion of lung volume occupied by cysts between lungs with and without pneumothorax. Patients with large cysts had significantly lower chest radiograph scores, but there was no correlation between the proportion of lung volume occupied by cysts and patient age or duration of either symptomatic lung disease or colonization by bacteria. On chest radiographs only bronchiectatic cysts with conglomerate diameters of greater than 3 cm were visible. Smaller lesions could not be separated from ring shadows produced by bronchiectasis.     

Computerized analysis of abnormal asymmetry in digital chest radiographs: Evaluation of potential utility

The purpose of this study was to develop and test a computerized method for the fully automated analysis of abnormal asymmetry in digital posteroanterior (PA) chest radiographs. An automated lung segmentation method was used to identify the aerated lung regions in 600 chest radiographs. Minimal a priori lung morphology information was required for this gray-level thresholding-based segmentation. Consequently, segmentation was applicable to grossly abnormal cases. The relative areas of segmented right and left lung regions in each image were compared with the corresponding area distributions of normal images to determine the presence of abnormal asymmetry. Computerized diagnoses were compared with image ratings assigned by a radiologist. The ability of the automated method to distinguish normal from asymmetrically abnormal cases was evaluated by using receiver operating characteristic (ROC) analysis, which yielded an area under the ROC curve of 0.84. This automated method demonstrated promising performance in its ability to detect abnormal asymmetry in PA chest images. We believe this method could play a role in a picture archiving and communications (PACS) environment to immediately identify abnormal cases and to function as one component of a multifaceted computer-aided diagnostic scheme.