Measurement of scatter fractions in clinical bedside radiography.

The authors present measurements of scatter fraction (SF), the ratio of scattered to total imaged photons, from clinical bedside radiographs of 102 patients. These measurements were obtained by using a new posterior beam-stop technique that does not alter the diagnostic image but that simultaneously provides SF measurements at 224 locations in the image. The SF values in the lung were found to be consistent with previous measurements, while the SF values in the mediastinal and retrocardiac areas were larger than previously reported. SFs in diseased lung were significantly larger than SFs in normal lung. The range of SF values was large for all anatomic locations. For applications in which accurate scatter estimation is required, this wide range of values suggests that SFs should be measured in each individual image.     

Efficacy of the scatter correction algorithm in portable chest radiography

Emergency Radiology - Portable chest radiographs (CXRs) continue to be a vital diagnostic tool for emergency and critical care medicine. The scatter correction algorithm (SCA) is a post-processing...     

Survey of posteroanterior chest radiography in The Netherlands: patient dose and image quality

Council Directive 97/43/Euratom (Medical Exposure Directive) states that member States of the European Union shall promote the establishment and use of diagnostic reference levels for radio-diagnostic examinations. Dose surveys can form the basis for the establishment of diagnostic reference levels. In view of the implementation of the Medical Exposure Directive in the Netherlands, a survey of dose and image quality has been performed for posteroanterior (PA) chest radiography in 2001. In this survey, 25 participants were selected from a list of 175 Dutch hospitals, whereas in a previous PA chest survey (about 10 years ago) participation was voluntary and participants came predominantly from the south-western part of the Netherlands. For conventional screen-film PA chest radiography, the present results for patient dose and image quality are quite similar to those results from the previous survey. The fraction of conventional X-ray systems utilizing lung compensation filters has remained approximately the same. For dedicated digital chest radiography systems, image quality is better than for conventional systems, but doses vary and can assume relatively high values. The results indicate that there are still possibilities for dose reduction, without loss of image quality. The 75 percentile value of the entrance surface dose distribution is approximately 0.13 mGy.     

Bone marrow dose in chest radiography: the posteroanterior vs. anteroposterior projection.

The dose to active bone marrow resulting from anteroposterior (AP) and posteroanterior (PA) chest examinations was estimated using an Alderson Rando phantom and extruded lithium fluoride dosimeters. The AP projections resulted in a mean marrow dose range of 1.9-2.6 mrad (0.019-0.026 mGy) as compared to doses for PA projections of 3.4-3.8 mrad (0.034-0.038 mGy) for optimally diagnostic exposure taken at 70, 90, and 120 kVp.     

Comparative scatter and dose performance of slot-scan and full-field digital chest radiography systems

PURPOSE: To evaluate the scatter, dose, and effective detective quantum efficiency (DQE) performance of a slot-scan digital chest radiography system compared with that of a full-field digital radiography system. MATERIALS AND METHODS: Scatter fraction of a slot-scan system was measured for an anthropomorphic and a geometric phantom by using a posterior beam-stop technique at 117 and 140 kVp. Measurements were repeated with a full-field digital radiography system with and without a 13:1 antiscatter grid at 120 and 140 kVp. For both systems, the effective dose was measured on posteroanterior and lateral views for standard clinical techniques by using dosimeters embedded in a female phantom. The effective DQEs of the two systems were assessed by taking into account the scatter performance and the DQE of each system. The statistical significance of all the comparative differences was ascertained by means of t test analysis. RESULTS: The slot-scan system and the full-field system with grid yielded scatter fractions of 0.13-0.14 and 0.42-0.48 in the lungs and 0.30-0.43 and 0.69-0.78 in the mediastinum, respectively. The sum of the effective doses for posteroanterior and lateral views for the slot-scan system (0.057 mSv +/- 0.003 [+/- standard deviation]) was 34% lower than that for the full-field system (0.086 mSv +/- 0.001, P < .05) at their respective clinical peak voltages (140 and 120 kVp, respectively). The effective DQE of the slot-scan system was equivalent to that of the full-field system in the lung region but was 37% higher in the dense regions (P < .05). CONCLUSION: The slot-scan design leads to marked scatter reduction compared with the more conventional full-field geometries with a grid. The improved scatter performance of a slot-scan geometry can effectively compensate for low DQE and lead to improved image quality.     

Detection of simulated nodules on clinical radiographs: dose reduction at digital posteroanterior chest radiography

PURPOSE: To determine to what extent dose reduction results in decreased detection of simulated nodules on patient digital posteroanterior (PA) chest radiographs. MATERIALS AND METHODS: Raw data from 20 clinical digital PA chest images that were reported as having normal findings and that were obtained with a slot-scan charge-coupled device system were used. For research protocol that concerns data with patient identities concealed, institutional review board approval is not required. One hundred twenty nodules varying in size and signal intensity were digitally simulated and added to the chest images. Hard copies were printed to represent a 100% dose and, by adding noise, to represent simulated patient doses of 50%, 25%, and 12%. Four radiologists reviewed images. Each lesion was registered as "detected" or "not detected." A semiparametric logistic regression model was used for statistical analysis. RESULTS: The decrease in radiation dose from 100% to 50%, 25%, or 12% had no effect on lesion detection in the lungs. The decrease in radiation dose had an effect on lesion detection in the mediastinum, as probabilities deteriorated from the 100% dose to the 50%, 25%, and 12% dose with each step. Probabilities of smaller detection rates when compared with that of the reference category (100% dose) were 0.97 (95% confidence interval [CI]: -0.86, 0.012) for the 50% dose, 1 (CI: -0.59, -0.61) for the 25% dose, and 1 (CI: -2.41, -1.22) for the 12% dose. CIs for the effects were on the log(odds). Detection probability decreased with smaller and lower signal intensity lesions. CONCLUSION: At clinical digital radiography, dose reduction resulted in decreased observer detection of simulated nodules in the mediastinum but not in the lungs.     

The posteroanterior chest radiograph in depressed sternum

The posteroanterior and lateral chest radiographs of 72 consecutive patients with sternal depression, together with 72 age- and sex-matched controls, have been reviewed. We assessed size and position of the cardiac silhouette, mediastinal contour, radio-opacity in the right lower zone and rib configuration. The degree of depression was determined from the lateral radiograph. The most significant signs of sternal depression on the posteroanterior chest radiograph are a straight left heart border, displacement of the cardiac silhouette to the left and an indistinct right heart border. These three signs have a high specificity for sternal depression and are significantly more commonly seen with increasing severity of depression. The presence of any three, or of more than three, of the described signs was 95.5% specific. However, despite this high specificity, the sensitivity and positive predictive value even for a combination of signs are low. Sternal depression is a relatively common chest deformity and the radiologist should be aware of the changes on the posteroanterior chest radiograph to avoid pitfalls in diagnosis.     

胸侧位像椎体压缩骨折诊断忽视原因浅析

目的 试分析常规X线胸像椎体压缩骨折诊断忽视的原因.方法 回顾分析1638例住院治疗患者的X线胸正侧位影像.年龄范围从50～91岁,平均(64±9)岁,其中男871例,女767例.所有患者的主诉或申请X线胸像检查的原因均与骨质疏松症和骨折无关.椎体压缩及分度的判定及分度方法选用Genant半定量(semiquantitative)目测法,椎体压缩骨折Ⅰ、Ⅱ、Ⅲ度的标准分别为椎体高度约减低20%～25%(Ⅰ度)、26%～40%(Ⅱ度)及41%以上(Ⅲ度),将椎体压缩骨折的影像评阅的结果与其既往X线报告结果和相应出院后病历记录进行比较分析.结果 1638例胸侧位影像评阅结果显示,椎体压缩骨折患者84例,压缩骨折的椎体总数为100个,其中X线影像报告已诊断为压缩骨折者共30例,X线影像报告未诊断的患者有54例.30例已诊断为椎体压缩骨折的X线影像报告中均未进行椎体压缩骨折的分度诊断.54例患者X线报告未诊断椎体压缩骨折63个,其中单发椎体压缩骨折47个,占X线报告未诊断椎体压缩骨折的75%;X线报告未诊断的Ⅰ度椎体压缩骨折34个(54%),Ⅱ度骨折21个(33%),而Ⅲ度骨折仅8个(13%).84例椎体压缩骨折患者中,行双能X线骨密度测量者仅有5例(6%),出院诊断椎体压缩骨折者仅有5例(6%),而出院带治疗骨质疏松症药物者也仅有15例(18%).15例带药患者所带与骨质疏松症治疗有关的药物均为钙类制剂.结论 无论影像科还是其他科室的医师均应增强对骨质疏松症的全面认识,对患者X线胸像侧位片所示的椎体骨质疏松性压缩骨折应做出及时、完整的影像诊断,并予规范化的防治和干预.     

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.