Bedside chest radiography: diagnostic efficacy

In order to evaluate the efficacy of bedside chest radiography, a prospective study was completed of 140 patients admitted to the surgical and medical intensive care units over a two-month period. A total of 1132 consecutive bedside radiographs was analyzed for malposition of tubes and lines and interval changes in the cardiopulmonary findings. The median number of bedside radiographs per patient was 0.7 per day. Endotracheal or tracheostomy tubes were present in 54% of all examinations; among these 12% were malpositioned. Central venous catheters were present in 47%; among these 9% were malpositioned. Interval changes regarding cardiopulmonary findings (pneumothorax, collapse, diffuse or focal infiltrate, effusion, and congestive heart failure) were present in 44% of the radiographs after the admission one. Overall there were new findings or changes affecting the patient's management present in 65% of the radiographs. The use of bedside radiography appeared to be appropriate.     

Image processing in digital chest radiography: effect on diagnostic efficacy.

The usefulness of digital image processing of chest radiographs was evaluated in a clinical study. In 54 patients, chest radiographs in the posteroanterior projection were obtained by both 14 inch digital image intensifier equipment and the conventional screen-film technique. The digital radiographs (512 x 512 image format) viewed on a 625 line monitor were processed in three different ways: (1) standard display; (2) digital edge enhancement for the standard display; and (3) inverse intensity display. The radiographs were interpreted independently by three radiologists. The diagnoses were confirmed by CT, follow-up radiographs and clinical records. Chest abnormalities of the films analyzed included 21 primary lung tumors, 44 pulmonary nodules, 16 cases with mediastinal disease and 17 cases with pneumonia/atelectasis. Interstitial lung disease, pleural plaques, and pulmonary emphysema were found in 30, 18 and 19 cases, respectively. The sensitivity of conventional radiography when averaged overall findings was better than that of the digital techniques (P less than 0.001). The differences in diagnostic accuracy measured by sensitivity and specificity between the three digital display modes were small. Standard image display showed better sensitivity for pulmonary nodules (0.74 vs 0.66; P less than 0.05) but poorer specificity for pulmonary emphysema (0.85 vs. 0.93; P less than 0.05) compared with inverse intensity display. We conclude that when using 512 x 512 image format, the routine use of digital edge enhancement and tone reversal at digital chest radiographs is not warranted.     

床旁数字X线胸部高千伏摄影在重症监护病房的应用

目的探讨床旁数字化X线摄影（digital radiography,DR）胸部高千伏摄影在重症监护病房（ICU）患者的应用价值。方法在ICU患者床旁DR胸部正位摄影中,把研究对象随机分为对照组和实验组．对照组摄片条件为管电压80kv,曝光量10～16mAs;实验组摄片条件为管电压125kV,曝光量1．8-2．0mAs．评价影像质量及患者辐射剂量。结果经计算实验组甲级片、乙级片百分率均高于对照组,影像质量实验组比对照组好。实验组患者所受辐射剂量明显小于对照组,差异有统计学意义（P〈0．05）。结论在ICU病房中用DR行胸部摄影,采用高千伏技术在提高影像质量,降低曝光量,减少受检者辐射剂量等方面有明显优势。     

Computer-aided diagnosis in chest radiography.

We have developed computer-aided diagnosis (CAD) schemes for the detection of lung nodules, interstitial lung diseases, interval changes, and asymmetric opacities, and also for the differential diagnosis of lung nodules and interstitial lung diseases on chest radiographs. Observer performance studies indicate clearly that radiologists' diagnostic accuracy was improved significantly when radiologists used a computer output in their interpretations of chest radiographs. In addition, the automated recognition methods for the patient and the projection view by use of chest radiographs were useful for integrating the chest CAD schemes into the picture-archiving and communication system (PACS).     

Detection accuracy in chest radiography.

The detection accuracy of the diagnostic radiologist is important in everyday medical decision making. However, little work has been done relating the detection accuracy of the radiologist to the quality of the image. This study, using a thorax and lung phantom, simulated tissue-equivalent 6.4 mm lesions, and a 183 cm source-to-image distance, shows that the detection accuracy is not dependent on the focal spot size (over a range of 0.3-2.0 mm). However, the false positive rate increases when using small focal spots. In addition, the detection accuracy decreases with increasing root-mean-square (RMS) noise (a measure of the amount of quantum mottle in the image), while the false positive rate and intraobserver disagreement increase with increasing RMS noise. It is also shown that the nonradiologist responds to changes in noise in exactly the same way as the radiologist.     

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.     

Digital radiography of the chest

Digital radiography is an appropriate method for both bedside and in-department chest radiographs. Its major advantage in bedside chest radiography is its control of the displayed optical density of these radiographs. With dynamic range control processing, it improves the visibility of tubes and lines superimposed on the mediastinal tissues. When used for in-department chest radiography, it may offer slight advantages in the evaluation of disease in the mediastinum, but in general is equivalent to film-screen chest radiography. The main reasons for using digital chest radiography for in-department chest radiographs relate mainly to its use as a data entry point method of projection radiography for high-quality teleradiology or for its use in a picture archiving and communication system. Apart from these advantages, there is no reason to change from conventional to digital chest radiographs. Digital radiographs are, with certain systems, printed at smaller than life size. Because of this, there is a necessary period of learning as radiologists adjust to the new image size. The most important change in radiologists' work pattern appears to be the need to sit closer to the film. Findings of disease are smaller, but, with experience, just as easy to see.     

Digital projection radiography of the chest

Direct and film-based radiographic systems are undergoing evaluation by observer performance studies for use in digital imaging of the chest. Many issues intrinsic to digital imaging are not settled, including the minimal pixel size necessary for images of accurate diagnostic quality, the characteristics of the display console, and the usefulness of digital imaging processing techniques. The chest is a particularly difficult anatomic region for examination by digital radiography because of the broad spectrum of disease findings encountered. These issues are discussed in reference to four reports that use observer performance tests for evaluating various facets of chest diagnosis using digital radiography.     

Recent advances in chest radiography

There have been many remarkable advances in conventional thoracic imaging over the past decade. Perhaps the most remarkable is the rapid conversion from film-based to digital radiographic systems. Computed radiography is now the preferred imaging modality for bedside chest imaging. Direct radiography is rapidly replacing film-based chest units for in-department posteroanterior and lateral examinations. An exciting aspect of the conversion to digital radiography is the ability to enhance the diagnostic capabilities and influence of chest radiography. Opportunities for direct computer-aided detection of various lesions may enhance the radiologist's accuracy and improve efficiency. Newer techniques such as dual-energy and temporal subtraction radiography show promise for improved detection of subtle and often obscured or overlooked lung lesions. Digital tomosynthesis is a particularly promising technique that allows reconstruction of multisection images from a short acquisition at very low patient dose. Preliminary data suggest that, compared with conventional radiography, tomosynthesis may also improve detection of subtle lung lesions. The ultimate influence of these new technologies will, of course, depend on the outcome of rigorous scientific validation.     

Measuring performance in chest radiography

PURPOSE: To use a standardized set of chest radiographs to quantify interobserver differences and to provide a basis for comparing the diagnostic performance of physicians. MATERIALS AND METHODS: A standardized set of 60 chest radiographs was presented to 162 study participants. Each participant reviewed the radiographs and recorded his or her diagnostic impression by using a fixed five-point scale. These response data were used to generate receiver operating characteristic curves and to establish performance benchmarks. The variations in performance were tested for statistical significance. RESULTS: Significant interobserver variability was identified during these assessments. The composite group of board-certified radiologists demonstrated performance superior to that of the radiology residents and nonradiologist physicians. CONCLUSION: By using a receiver operating characteristic approach and a standardized set of chest radiographs, observer accuracy and variability are easily quantified. This approach provides a basis for comparing the diagnostic performance of physicians. When value is measured as a diminution in uncertainty, board-certified radiologists contribute substantial value to the diagnostic imaging system.     

Diagnosis of tracheal carcinoma at chest radiography.

All of the 95 primary tracheal carcinomas registered in Finland during 1967 to 1985 were reviewed. Chest radiographs of 44 patients were available. A tracheal tumor was detected in 8 cases (18%) in the primary examination and according to the review all the detected tumors were larger than 15 mm. However, when the same radiographs were reexamined by a senior radiologist, the tumor was identified in the correct site in 66%. This percentage parallels the results of high kV tracheal radiography (69%) performed on 32 patients. Tumors involving anterior or posterior wall and tumors near the bifurcation were the most difficult to detect.     

Standard radiography of the chest in heart transplantation. Our experience

In the cardiovascular Surgery Department of the University of Padua, where the first heart transplant operation in Italy took place in November, 14, 1985, in a period of six months, nine heart transplants have been performed. The post-operative follow-up of these patients included, among other tests, a chest X-ray, which has given us many morphological and functional data concerning both the circulatory and the pulmonary systems.     

Temporal subtraction chest radiography

Radiologist are commonly required to compare a sequence of two or more chest radiographs of a given patient obtained over a period of time, which may range from a few hours to many years. In such cases, the task is one of detecting interval change. In the case of patients who have had a previous chest radiograph, an opportunity exists to enhance selectively areas of interval change, including regions with new or altered pathology, by using the previous radiographs as a subtraction mask. With temporal subtraction, the previous image is superimposed and registered with the current image, using automated two-dimensional warping to compensate for any differences in positioning. A “difference image” is then created, by subtracting the previous from the current radiograph. In this temporal subtraction image, areas that are unchanged appear as uniform gray, while regions of new opacity, such as due to pneumonia or cancer, appear as prominent dark foci on a lighter background. By cancelling out the complex anatomical background, temporal subtraction can provide dramatically enhanced visibility of new areas of disease.     

Clinical evaluation of the 350-kV chest radiography system.

A chest radiography unit employing 350 kV was evaluated and found to be superior to conventional low-kV systems. Visualization of air/soft-tissue boundaries, mediastinal structures, the retrocardiac area, and lung apices was improved. Other benefits of the high-kV system include reproducibility, reliability, rapid installation, and economy of operation.