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.     

Digital radiography of the chest: state of the art

Digital image acquisition possesses a number of advantages over conventional systems in radiographic examination of the chest, the most important of which is its greater dynamic range. In addition, one digital images are acquired, they can be processed by computer in ways that cannot be rivalled by conventional analog techniques. Finally, digital images can be stored, retrieved and transmitted to local or remote sites. Here the status of the different digital systems employed in chest radiology and commonly used image processing techniques are reviewed. Also discussed are the current clinical applications of integrating digital chest radiography with a picture archiving and communication system (PACS) along with the difficulties typically encountered. Studies with a variety of digital techniques have been carried out on several fronts. Computer radiography based on photostimulabe phosphor (CR) has replaced screen-film imaging in certain applications (i.e. bedside imaging). However, CR has limitations, namely its poor X-ray utilisation efficiency at high X-ray tube voltages and sensitivity to scatter; therefore, it is not ideal for all applications. Recently, a dedicated digital chest unit with excellent X-ray utilisation efficiency at high X-ray tube potentials has been introduced. On the basis during the past decade, recommendations are made regarding the most desirable equipment specifications for dedicated and bedside digital chest radiography.     

Computed radiography in musculoskeletal imaging

In conclusion, CR offers many advantages in comparison with conventional radiography. Musculoskeletal radiology particularly benefits from the wide dynamic range and image-processing capabilities of CR. Most studies have not shown a statistically significant difference in observer performance (diagnostic accuracy) of CR in comparison with conventional radiography in musculoskeletal applications. In addition, dose reduction in the range of 25% to 50% is possible with many musculoskeletal images. However, disadvantages are also apparent and include reduced spatial resolution, increased noise, and change in image size and format. Overall, the advantages of CR and digital technology outweigh its limitations and for these reasons continue to promote the conversion from conventional radiography.     

Thoracic aortic rupture: advantages of intraarterial digital subtraction angiography

Sixty-one consecutive patients with blunt thoracic trauma underwent intraarterial digital subtraction angiography (IA-DSA) of the thoracic aorta because of obscuration of the aortic knob or mediastinal widening on chest radiographs. Ten of these patients had aortic ruptures diagnosed by IA-DSA. Digital subtraction aortography proved 100% accurate as indicated by results of surgery, conventional arteriography, serial chest radiography, and clinical follow-up. The method was 50% faster compared with conventional aortography and saved significantly on film costs. The potential for use of smaller caliber catheters and a decrease in contrast requirements also make this method safer than conventional arteriography. We recommend IA-DSA as the procedure of choice when emergency aortography is warranted.     

1991 RSNA special focus session: current controversies in the management of ductal carcinoma in situ of the breast.

To determine the impact of reduced hard-copy size on diagnostic performance of digital radiography, screen-film chest radiographs were compared with isodose digital storage phosphor radiographs in the detection of simulated nodules, fine pulmonary lines, and micronodular opacities superimposed on the chests of 10 healthy volunteers. Digital radiographs were laser-printed in a full-size conventional format and in image lengths of two-thirds, one-half, and five-elevenths of the conventional format. Eighteen thousand observations by eight radiologists were analyzed by use of receiver operating characteristics. The detectability of lines and micronodular opacities decreased with declining image format size. In the detection of micronodular opacities, only the nearly full-size digital images were equivalent to conventional images. In the detection of linear opacities, reduction of image length by one-half or more reduced performance (analysis of variance, P less than .05). Only for the detection of nodules was no major difference found.     

双能量数字减影胸片对肺内小结节检出的意义

目的探讨双能量数字减影胸片对肺内小结节检出的意义。方法27例病理证实恶性肿瘤伴肺内转移的患者,分别行增强CT扫描、双能量数字减影胸片与常规DR胸片。使用柯达质量控制检测仪比较双能量数字减影DR与常规DR胸片的图像质量。再以CT扫描结果为金标准,由2位高年资放射科医师采用双盲法对双能量数字减影胸片与常规DR胸片进行分析,比较两者对肺内转移瘤的检出有无显著差异。结果双能量数字减影DR与常规DR图像在噪声上(均匀度)无差异,但清晰度稍差。双能量数字化减影的胸片对肺内小结节的检出率为91.2%;而常规DR胸片对肺转移瘤的检出率为85.0%,两者之间有显著差异(P<0.05)。结论双能量数字减影技术可减少肺野内骨骼及其它钙化影响,对肺内结节的检出能力高于常规DR胸片。     

Efficacy of daily bedside chest radiography as visualized by digital luminescence radiography

To determine the diagnostic impact of daily bedside chest radiography in comparison with digital luminescence technique (DLR; storage phosphor radiography) and conventional film screen radiography, a prospective randomized study was completed in 210 mechanically ventilated patients with a total of 420 analysed radiographs. The patients were allocated to two groups: 150 patients underwent DLR, and 60 patients underwent conventional film screen radiography. Radiological analysis was performed consensually and therapeutic efficacy was assessed by the clinicians. There was no statistical significant difference between the frequency of abnormal findings seen on DLR and conventional film screen radiography. In total, 448 abnormal findings were present in 249 of 300 DLR and 97 of 120 conventional film screen radiographs. The most common findings were signs of overhydration (41%), pleural effusion (31%), partial collapse of the lung (11%) and pneumothorax (2%). One hundred and twenty-three of 448 (27%) of these abnormal findings were thought to have a considerable impact on patient management. The high rate of abnormal findings with significant impact on patient management suggests that the use of daily bedside chest radiography may be reasonable.     

Improved control of image optical density with low-dose digital and conventional radiography in bedside imaging

The technical and diagnostic performance of simultaneously acquired low-dose (44% of standard dose) storage-phosphor digital radiographs (system resolution = 0.2 mm, 10 bits) were compared with those of standard-dose conventional bedside radiographs of the chest in 32 patients. The mean optical density (OD) of the lungs (800 measurements) was closer to the ideal density with digital radiography (1.45 OD +/- 0.20 [standard deviation] vs 1.75 OD +/- 0.53) and was less often outside the usable range (2.5% vs 42.5%). Receiver operating characteristic analysis for detection of simulated nodules and monitoring devices (nine readers, 4,608 observations) showed that digital radiography was superior to conventional radiography (P less than .05) for four of the nine readers and equivalent to conventional radiography for five readers. The authors concluded that digital radiography produces more consistent and ideal image density and performs at least as well as conventional radiography under phantom test conditions.     

Thoracic CT in detecting occult disease in critically ill patients

Bedside chest radiography is important in the detection of thoracic disease in critically ill patients. Unfortunately these studies are often of poor technical quality and are frequently difficult to interpret. Eighty-seven bedside chest radiographs and concurrent thoracic CT scans obtained in 56 critically ill patients over a 20-month period were interpreted retrospectively and independently. In most cases, the studies were obtained to search for a source of sepsis, fever, or unexplained clinical deterioration. In this series, thoracic CT added significantly more diagnostic information in 61 (70%) of these studies than was available from the corresponding bedside radiographs. Despite the difficulties of transporting critically ill patients for CT and the significant cost, our results suggest that the improved rate of detection of unsuspected thoracic disease justifies the use of CT when bedside radiographic examinations fail to adequately explain the clinical findings.     

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.     

CR床边胸部摄影吸收剂量的相关性研究

目的：评价CR床边胸部摄影对于患者的吸收剂量。方法：68例胸部X线摄影分别采用CR病房床边胸部摄影和DR在影像科进行胸部摄影两种不同的方式拍摄。CR床边胸部摄影采用68~76kVp进行前后位摄影。DR胸部摄影采用110~140kVp后前位进行摄影。用统计学方法对其X线吸收剂量进行评价。结果：在吸收剂量方面几种方法各不相同,CR床边胸部摄影与DR胸部摄影患者的随机吸收剂量无统计学差异。CR床边胸部摄影被检者与其邻近患者之间其吸收剂量有显著性差异。结论：DR胸部摄影患者的随机吸收剂量低于CR床边胸部摄影。     

Assessment of digital chest radiography using stimulable phosphor

In this pilot study, conventional and digital radiography of the chest was compared in 170 patients. Two digitized radiographs, one frequency modified and one simulating the conventional film-screen combination, and the conventional films were reviewed independently by 5 radiologists with different experience. In spite of the smaller size and lower spatial resolution of the digitized compared with the conventional radiograph, only slight differences were revealed in the observation of different pulmonary and mediastinal changes. Digitized radiography is therefore considered suitable for chest examinations.     

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.     

床旁DR与床旁CR胸部摄影质量对比分析

目的 通过对床旁数字化X线摄影系统(DR)与计算机X线摄影系统(CR)拍摄胸片图像的质量分析总结,探讨床旁DR摄影的优势.方法 应用床旁DR系统拍摄床旁胸片900张,与随机抽取的既往床旁CR胸片900张进行对比.结果 床旁DR的应用进一步减少了重拍率,降低了辐射剂量,可提供更加优良的影像信息.结论 床旁DR胸部摄影较CR胸部摄影有着明显的优势,在危重患者和手术患者的诊治中起到了积极作用.

Abstract：

Objective To explore the advantages of the bedside DR,taking the quality analysis of the chest image taken from the bedside digital radiography systems (DR) and computed radiography system (CR).Method All of the 900 pieces chest image taken by bedside DR,compared with the 900 pieces CR image randomly chosen.Results Bedside DR could further reduce the rate of the remake and the radiation dose,and provided more excellent image information.Conclusion The chest image taken by bedside DR has obviously advantage than CR.It can play a positive role in the diagnosis and treatment of the critical patient and surgical patient.     

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.     

Computed radiography in musculoskeletal imaging: state of the art.

Computed radiography is a 2K x 2K x 10 bit digital radiographic system that replaces the film-screen combination with a photo-stimulable phosphor plate. The advantages of this relatively new technology include linear detector response, improved detector efficiency, and digital processing capabilities. Musculoskeletal applications benefit significantly from these attributes, which result clinically in the ability to reduce both radiation dose and number of exposures. Studies of observers' performance have shown no statistically significant difference in diagnostic accuracy between film-screen and computed radiographic musculoskeletal images. Computed radiography is particularly useful in the evaluation of the musculoskeletal system in traumatized patients with portable radiographs, spine radiographs, scoliosis studies, and depiction of soft-tissue abnormalities. Limitations include change in image format and size, high cost, decreased spatial resolution, restricted throughput, increased perception of noise, and new artifacts that must be recognized. Spatial resolution limitations of computed radiography in identification of fine detail information can be improved by using magnification techniques. Radiation dose reduction with an exposure decrease of 25-50% can be achieved without loss of diagnostic accuracy, although this depends on the examination and the abnormality. An interactive workstation is important in the use of a computed radiographic system with capabilities to adjust display parameters to best depict images and disease. We conclude that computed radiography is an alternative to film-screen radiography without significant differences in diagnostic quality in the evaluation of musculoskeletal images.     

数字化体层融合在肺结节探查中的初步应用

目的 探讨数字化体层融合在肺结节探查中的应用价值.方法 30例疑有肺内结节的患者,均先后行胸部X线平片、体层融合和CT检查.将上述影像资料传至后处理工作站,由2名具有3年以上胸部影像诊断经验的医师分别进行双盲法阅片,观察每例患者肺部结节的数量,每个肺结节的部位、大小.然后,2名阅片者再共同阅片,使单独阅片不一致的结果得到统一.以CT结果作为标准,分别计算胸部X线平片和体层融合探查肺结节的敏感性.采用配对四格表资料的X~2检验比较两者的差异性.结果 30例患者,胸部X线平片检查9例阴性,21例阳性,共发现肺结节40个.体层融合检查4例阴性,26例阳性,共发现肺结节89个.CT检查3例阴性,27例阳性,共发现肺结节102个.以CT作为标准对照,胸部X线平片探查肺结节的敏感性为27.4%(28/102),体层融合的敏感性为87.2%(89/102),差异有统计学意义(X~2=4.35,P<0.05).结论 数字化体层融合可显著提高肺结节探查的敏感性,可以作为胸部X线平片良好和必要的补充.     

Clinical results of CsI-detector-based dual-exposure dual energy in chest radiography

The aim of this study was to compare the sensitivity and specificity of digital chest radiography alone with digital chest radiography combined with dual-energy chest radiography in the detection of small non-calcified pulmonary nodules. Standard and dual-energy radiographs were obtained with a flat-panel digital chest system. Four radiologists reviewed digital posteroanterior chest radiographs in random order either alone or in conjunction with dual-energy soft tissue and bone images. Twenty patients with a total of 59 pulmonary nodules (median 0.5 cm, range 0.3 – 2.5 cm) confirmed by computed tomography (HU 100) were included. A level of confidence for each diagnosis was documented using a rating scale of 1–5. Brunner and Langer's test was performed for statistical analysis. Subgroup analysis was performed for nodules greater than 1 cm, 1–0.5 cm, and <0.5 cm. For posteroanterior chest radiography, sensitivity was 33%, positive predictive value 83%, specificity 81%, and negative predictive value 30%. Review in conjunction with dual-energy images resulted in a sensitivity of 42%, positive predictive value 88%, specificity 85%, and negative predictive value 34%. The increase of nodule detection overall as well as for different size categories was significant (p<0.05). The increase of the confidence level rating was also significant (p<0.001). Dual energy added to standard posteroanterior chest radiography significantly improves the sensitivity, specificity, and confidence in detection of small non-calcified pulmonary nodules.     

Optimisation of radiological protocols for chest imaging using computed radiography and flat-panel X-ray detectors

Purpose

Digital radiography technology has replaced conventional screen-film systems in many hospitals. Despite the different characteristics of new detector materials, frequently, the same radiological protocols previously optimised for screen film are still used with digital equipment without any critical review. This study addressed optimisation of exposure settings for chest examinations with digital systems, considering both image quality and patient dose.

Materials and methods

Images acquired with direct digital radiography equipment and a computed radiography system were analysed with specially developed commercial software with a four-alternative forced-choice method: the most promising protocols were then scored by two senior radiologists.

Results

Digital technology offers a wide dynamic range and the ability to postprocess images, allowing use of lower tube potentials in chest examinations. The computed radiography system showed both better image quality and lower dose at lower energies (85 kVp and 95 kVp) than those currently used (125 kVp). Direct digital radiography equipment confirmed both its superior image quality and lower dose requirements compared with the storage phosphor plate system.

Conclusions

Generally, lowering tube potentials in chest examinations seems to allow better image quality/effective dose ratio when using digital equipment.     

Digital panoramic radiography: a clinical survey

The application of digital panoramic radiography with photostimulable phosphors to dental diagnosis was evaluated in 500 patients. Comparative intraoral films of selected groups of teeth and electronic magnifications of the same portion of the arches were obtained in 63 cases. Digital images improved the quality of dental examinations compared with film radiographs. The possibility of contrast modulation was helpful to compensate for the different radiographic densities of the arches and to improve the visibility of gingival soft tissues. In addition, digital radiography reduced the radiation dose administered to the patient. The use of digital panoramic radiography is proposed as a substitute for film studies in all hospitals where a central unit for digital radiology is available. Correspondence to: R. Nessi