Detection of subtle lung nodules: relative influence of quantum and anatomic noise on chest radiographs

PURPOSE: To assess the relative influence of quantum mottle and structured lung patterns (anatomic noise) on the detection of subtle lung nodules on chest radiographs. MATERIALS AND METHODS: Sixty 8 x 8-cm lung pattern images were extracted from digital chest radiographs in healthy individuals. Sixty quantum mottle images of the same size and quantum noise level were extracted from uniformly exposed digital radiographs. Simulated nodules with various peak contrast-diameter products (CD) that emulated subtle tissue-equivalent lung nodules were numerically superimposed at the center on three-fourths of the images. Printouts were independently viewed and scored by five experienced radiologists. The area under the receiver operating characteristic curve (Az) was estimated as a measure of the detectability of the nodules. RESULTS: At a fixed observer performance level (e.g., Az = 0.8), much smaller and lower-contrast nodules were detected on quantum mottle images (1-mm diameter, CD = 0.01 mm), compared with those on anatomic images (4.5-mm diameter, CD = 0.20 mm). The findings generally agreed with the signal-to-noise ratio calculations based on statistical observer models. CONCLUSION: The detection of subtle lung nodules on chest radiographs is limited by anatomic noise.     

Nonpulmonary abnormalities recognizable in pediatric chest radiographs

Systemic disorders can often be recognized or suspected from chest radiographs. This is often true in pediatric radiology. In this article, the author presents a sampling of metabolic, hematologic, and endocrine diseases as well as malformations that are recognizable on pediatric chest radiographs.     

Detection of pleural effusions on supine chest radiographs

A prospective analysis of anteroposterior supine radiographs in 34 patients was undertaken to determine the detectability of pleural effusions on supine radiographs. The presence of pleural effusions and quantity of fluid (small, moderate, or large) were evaluated by using the following radiographic signs: increased homogeneous density superimposed over the lung, loss of the hemidiaphragm silhouette, blunted costophrenic angle, apical capping, elevation of the hemidiaphragm, decreased visibility of lower-lobe vasculature, and accentuation of the minor fissure. Decubitus radiographs were performed to identify and to estimate the quantity of pleural fluid. Sixty-two hemithoraces were evaluated by three observers. From a total of 36 pleural effusions shown on decubitus views, 24 were correctly identified on supine radiographs (sensitivity of 67%, specificity of 70%, and accuracy of 67%). The most frequent but least specific criterion for detecting pleural effusions on supine radiographs is blunting of the costophrenic angle. Other helpful signs include loss of the hemidiaphragm and increased density of the hemithorax. A normal supine radiograph does not exclude a pleural effusion. Our results show that supine radiographs are only moderately sensitive and specific for the evaluation of pleural effusions.     

Using edge enhancement to identify subtle findings on soft-copy neonatal chest radiographs.

OBJECTIVE: The purpose of this study was to evaluate whether edge enhancement could improve the visibility of subtle findings on soft copies of neonatal chest radiographs. MATERIALS AND METHODS: Two radiologists reviewed 82 soft-copy neonatal chest radiographs before and after the application of edge enhancement on our picture archiving and communication system (PACS). The visibility of a pneumothorax (n = 22), central venous catheter (n = 32), umbilical arterial catheter (n = 36), endotracheal tube (n = 40), and normal anatomic structures (the minor fissure, anterior segmental bronchus of the right upper lobe, and aortic arch, n = 57) was evaluated. Six of 22 soft-copy images depicting a pneumothorax were excluded from the evaluation of image quality either because of the large size of the pneumothorax itself (n = 7) or because of the lack of confirmatory evidence that would have been provided by an additional lateral decubitus (n = 6) or cross-table lateral radiograph (n = 3). Image quality was evaluated by visual grading analysis. RESULTS: The visibility of a pneumothorax (p < 0.01), vascular catheters (p < 0.001), the minor fissure (p < 0.001), and the anterior segmental bronchus of the right upper lobe (p < 0.001) improved significantly after applying edge enhancement to soft copies of neonatal chest radiographs, whereas the visibility of the aortic arch did not improve. Evaluations of the improvements in the visibility of the endotracheal tube were inconsistent. CONCLUSION: Application of edge enhancement to soft copies of neonatal chest radiographs helps radiologists to identify small pneumothoraces, vascular catheters, and delicate normal structures, thereby improving the detection of subtle chest findings in the neonatal intensive care unit.     

Detection of incidental vertebral fractures on routine lateral chest radiographs

Purpose

This study sought to assess the usefulness of routine lateral chest radiographs for detecting unrecognised vertebral compression fractures.

Materials and methods

We prospectively selected outpatients without symptoms or risk factors for osteoporosis who underwent chest radiography for different clinical indications. Two independent reviewers with different levels of experience assessed the radiographs for vertebral deformities and graded them as mild, moderate and severe according to the semiquantitative Genant Index. The kappa statistic was used to evaluate interobserver agreement and verify the reproducibility of this method. The prevalence of vertebral fractures observed was compared with that recorded in the official radiology reports.

Results

Our study involved 145 patients (73 men, 72 women; age range 50–86 years, mean age 67.5). Clinically relevant vertebral fractures were seen in 18/145 patients (12.4%). These were moderate in 13 patients and severe in five, and single in 12 patients and multiple in six. Interobserver agreement was very high (κ=0.9). Only 11% of these fractures were recorded in the official reports.

Conclusions

Lateral chest radiographs could be effective for assessing previously unknown vertebral compression fractures in individuals without clinical evidence or risk factors for osteoporosis.     

Detection of discrete white matter lesions after irreversible compression of MR images.

PURPOSETo validate the use of techniques of irreversible compression of images, which can be performed using a block-based discrete cosine transform technique as defined by the Joint Photographic Experts Group, before they can be used in clinical applications, by evaluating the effect of compression on the ability of observers to detect discrete white matter lesions on MR images of the brain.METHODSSixty T2- and intermediate-weighted spin-echo images were compressed with varying degrees of coefficient quantization with compression ratios from 1:1 to more than 40:1, randomized, and evaluated by three observers blinded to the degree of compression.RESULTSNo significant difference in the number of lesions detected was apparent until compression ratios reached 40:1, despite a significant subjective loss in perceived image quality at 20:1. Only small (< or = 5 mm) lesions were missed at the highest degree of compression. No significant differences were observed in the detection of confluent periventricular white matter disease at any degree of compression tested.CONCLUSIONSThe use of high degrees of irreversible compression of MR images may be acceptable for diagnostic tasks.     

Importance of radiology clerkships in teaching medical students life-threatening abnormalities on conventional chest radiographs

RATIONALE AND OBJECTIVES: The purpose of this study was to investigate the ability of medical students who had already completed medicine and surgery clerkships to identify life-threatening abnormalities on conventional chest radiographs. MATERIALS AND METHODS: From May 2000 to August 2001, 72 consecutive 3rd- and 4th-year medical students enrolled in the radiology clerkship at Rhode Island Hospital completed examinations before and after the radiology clerkship. During the examination, they were asked to identify acute abnormalities on five conventional chest radiographs. Only students who had already completed both medicine and surgery clerkships were included in this prospective study. RESULTS: Before the radiology clerkship, the frequency of correct diagnoses of pneumothorax, pneumoperitoneum, congestive heart failure, misplaced endotracheal tube, and misplaced feeding tube were 40%, 61%, 57%, 6%, and 6%, respectively. After the radiology clerkship, these findings were correctly identified more than 94% of the time (P < .001). CONCLUSION: Learning to identify life-threatening abnormalities on conventional chest radiographs through medicine and surgery clerkships is insufficient. The radiology clerkship provides a unique educational experience that significantly improves these abilities.     

Comparison of radiologist and CAD performance in the detection of CT-confirmed subtle pulmonary nodules on digital chest radiographs

OBJECTIVES: Detection of subtle pulmonary nodules on digital radiography is a challenging task for radiologists. The aim of this study was to evaluate the performance of a newly approved computer aided detection (CAD) system. MATERIALS AND METHODS: The sensitivity of 3 radiologists and of a CAD system for the detection of pulmonary nodules from 5 to 15 mm in size on digital chest radiography of 117 patients was compared. The reference standard was established by consensus reading of computed tomography scans by 2 experienced radiologists. Computed tomography scans and chest radiographs were performed within 4 weeks. Sixty-six pulmonary nodules from 42 patients, with a mean nodule diameter of 7.5 mm (standard deviation: 2.2 mm), were included in the statistical analysis. Seventy-five of the 117 patients did not have nodules from 5 to 15 mm of size. RESULTS: Two hundred and eighty-eight false-positive detections of the CAD system were found with an average of 2.5 false-positives per image. Sensitivity of the CAD system was 39.4% (95% confidence interval: 11.8%), when compared with 18.2% to 30.3% (95% confidence interval 9.3% to 11.1%) of the 3 radiologists. Substantial agreement for nodule detection ([kappa]N: 0.64-0.73) was found among the 3 radiologists, whereas only moderate agreement was found between the radiologists and the CAD performance ([kappa]N: 0.45-0.52). CONCLUSIONS: The CAD system's diagnostic sensitivity in detecting pulmonary nodules of 5 to 15 mm of size was superior to the 1 of radiologists. The CAD system may be used for assisting the radiologist in the detection of lung nodules on digital chest radiographs.     

Apparatus seen on chest radiographs after cardiac surgery in adults

The authors review the purpose, radiographic appearance, and possible complications of various tubes, catheters, and wires seen on chest radiographs after cardiac surgery. Drainage tubes, temporary epicardial wire electrodes, surgical clips, intraaortic counterpulsation balloon, atrial pressure monitor catheters, and sternal wires are reviewed. Because recent articles have discussed the Swan-Ganz catheter and automatic implantable cardioverter defibrillator, these are not covered in depth.     

Influence of monitor luminance change on observer performance for detection of abnormalities depicted on chest radiographs

RATIONALE AND OBJECTIVES: To investigate how changes in luminance affect the detection accuracy of radiologists viewing chest radiograph images on high-resolution CRT monitors. MATERIALS AND METHODS: Thirteen radiologists performed a detection task for 11 chest radiograph images with simulated nodules on a monitor with 11 luminance conditions (the maximum luminance ranges from 157.4-369.0 candela/m2) simulating CRT degraded by long-term usage, under the ambient illumination of 200 lux; the observation order was always from the darkest to the brightest. RESULTS: There was a statistically reliable effect of the 11 monitor display conditions on the detection of nodules (P < 0.001). In the conditions in which the maximum luminance of the CRT was 60.7% or below that of the standard display luminance, the correctly detected nodule number reliably deteriorated. CONCLUSIONS: The luminance change in CRT monitor display under long-term usage will have a detrimental effect on nodule detection performance in chest radiograph images.     

Need for chest radiographs during and after lymphography.

Retrospective review of 100 lymphograms showed that routine chest radiography after injection of the lymphographic contrast medium and follow-up films 24-48 hr later yielded no clinically useful information. It was concluded that routine postlymphography chest radiography is not necessary and should be reserved for patients in whom complications are suspected.     

Findings on chest radiographs after prophylactic pulmonary surfactant treatment of premature infants

Clinical trials are underway that use pulmonary surfactant replacement therapy in an attempt to prevent respiratory distress syndrome (RDS) in premature infants. This study was undertaken to determine the relationship between the clinical course of infants receiving prophylactic "first-breath" endotracheal surfactant and their initial posttreatment radiographs. The study population consisted of 80 premature infants of 24-32 weeks gestational age. All received 3 ml of calf-lung surfactant extract via endotracheal tube at birth. Anteroposterior chest radiographs taken within 1 hr of treatment were reviewed and correlated with gestational age, birth weight, days of endotracheal intubation, mean airway pressure, and days of oxygen requirement greater than 30%. Three distinct patterns of radiographic abnormality were encountered: typical RDS with hypoinflation, diffuse granularity, and air bronchograms (30%); central clearing of RDS (14%); and disproportionate clearing of RDS in the right lung (8%). No significant differences in ventilator requirements or clinical course were seen among these three groups. A fourth group (49%), whose posttreatment radiographs showed no evidence of RDS, required significantly less ventilatory support. Prophylactic first-breath surfactant treatment of premature infants occasionally results in radiographic patterns that are atypical for RDS. Familiarity with these patterns and their clinical significance will be important if surfactant augmentation becomes prevalent.     

Tilted air-fluid interfaces on chest radiographs

Three patients had hydropneumothoraces in which the air-fluid interfaces were tilted from the horizontal. One was examined fluoroscopically, and the interface "seesawed" synchronously with the heartbeat. Displacement of the fluid by cardiac pulsation is the most likely usual cause of tilted air-fluid interfaces in the chest.     

Clinical evaluation of irreversible image compression: analysis of chest imaging with computed radiography

To implement a picture archiving and communication system, clinical evaluation of irreversible image compression with a newly developed modified two-dimensional discrete cosine transform (DCT) and bit-allocation technique was performed for chest images with computed radiography (CR). CR images were observed on a cathode-ray-tube monitor in a 1,024 X 1,536 matrix. One original and five reconstructed versions of the same images with compression ratios of 3:1, 6:1, 13:1, 19:1, and 31:1 were ranked according to quality. Test images with higher spatial frequency were ranked better than those with lower spatial frequency and the acceptable upper limit of the compression ratio was 19:1. In studies of receiver operating characteristics for scoring the presence or absence of nodules and linear shadows, the images with a compression ratio of 25:1 showed a statistical difference as compared with the other images with a compression ratio of 20:1 or less. Both studies show that plain CR chest images with a compression ratio of 10:1 are acceptable and, with use of an improved DCT technique, the upper limit of the compression ratio is 20:1.     

Computerized classification of interstitial lung abnormalities on chest radiographs with normalized radiographic index and normalized fractal dimension

OBJECTIVE: To evaluate the performance of two kinds of physical measures, the normalized radiographic index (R) and the normalized fractal dimension (F), for computerized classification of interstitial lung abnormalities on chest radiographs. METHODS AND MATERIAL: The values of R were obtained as the normalized percent area of extracted opacities in selected regions of interest (ROIs). The values of F were calculated with a box-counting algorithm and then normalized. To extract linear opacities on chest radiographs selectively, we processed ROIs by four-directional Laplacian-Gaussian filtering and binarization (4LG/B), linear opacity judgment (LOJ), and linear opacity subtraction (LOS). We used the ROIs of 50 mild and 50 severe interstitial lung abnormalities. In both groups, all cases were divided into H (n=21, honeycombing opacities were found to be dominant) and Non-H (n=79, abnormal opacities were found, but these were excluded from H). We obtained three types of normalized physical measures of R and F in one ROI from 4LG/B, LOJ, and LOS images, and the combined indices, R(COM) and F(COM) were calculated. RESULTS: The values of F(LOJ) could differentiate H from Non-H in the mild-and the severe-abnormality group. However, all Rs could not differentiate H from Non-H in the severe-abnormality group. The combined indices of both R and F could differentiate H from Non-H in the mild-abnormality group; however, these could not differentiate H from Non-H in the severe-abnormality group. CONCLUSION: The values of F(LOJ) seem to be useful in the classification of interstitial lung abnormalities on chest radiographs.     

Evaluation of cardiopulmonary devices on chest radiographs: digital vs analog radiographs

We compared digital and analog radiographs of the chest for use in detecting and evaluating a variety of cardiopulmonary devices in 40 patients. The devices included 23 endotracheal tubes, 21 Swan-Ganz catheters, 14 central venous pressure catheters, 11 prosthetic valves, 10 chest tubes, six pacemaker wires, and five intraaortic balloon pumps. Each patient had at least one device, with a maximum of five devices (average, 2.3). Forty digital/analog film pairs were compared by five radiologists, who assigned confidence levels for various judgments about each device. The results showed that there were no statistically significant differences in the identification of the devices except for prosthetic valves (all valves were detected on digital radiographs, compared with 62% on analog radiographs). The devices were detected on 96% of the digital radiographs and 90% of the analog radiographs. Although digital and analog radiographs were comparable for detection of most devices, the digital radiographs allowed greater confidence in the identification of the devices and in the identification of the tip and course of Swan-Ganz and central venous pressure catheters.