High-resolution CT: normal anatomy, techniques, and pitfalls.

High-resolution CT (HRCT) as a technique has shown an increasing role in the evaluation of known or suspected lung disease. To accurately interpret HRCT, an awareness of normal lung and pleural anatomy is essential. Knowledge of optimal HRCT technique is necessary to avoid misinterpretation and increase diagnostic accuracy. In addition, the potential technical and patient-related pitfalls are many. This article discusses normal lung and pleural anatomy, the technique of HRCT, and potential technical and patient-related pitfalls of HRCT.

Thoracic manifestations of systemic autoimmune diseases: radiographic and high-resolution CT findings.

The systemic autoimmune diseases include collagen vascular diseases, the systemic vasculitides, Wegener granulomatosis, and Churg-Strauss syndrome. They can cause a variety of thoracic abnormalities that are influenced by the pathophysiologic characteristics of the underlying disease process. Although many of the abnormalities can be detected at chest radiography, high-resolution computed tomography (CT) has been shown to be superior in depicting parenchymal, airway, and pleural abnormalities. Thoracic manifestations of collagen vascular diseases include pleural disease, pulmonary fibrosis, diaphragm weakness, aspiration pneumonia, bronchiolitis obliterans organizing pneumonia, bronchiolitis obliterans, and bronchiectasis. Wegener granulomatosis may be associated with multiple nodules or masses with irregular margins that are frequently cavitated. Patients with Churg-Strauss syndrome often have consolidation or ground-glass attenuation at chest radiography and CT. Goodpasture syndrome is associated with extensive bilateral air-space consolidation.

Radiographic and CT findings in blunt chest trauma.

Injuries of the thorax are a major cause of morbidity and mortality in blunt trauma patients. Radiologic imaging plays an important role in the workup of the patient with thoracic trauma. The chest radiograph is the initial imaging study obtained, but computed tomography (CT) is now used frequently in the evaluation of chest trauma. The primary role of chest CT has been to assess for aortic injuries, but CT has been shown to be useful for the evaluation of pulmonary, airway, skeletal, and diaphragmatic injuries as well. Magnetic resonance imaging (MRI) has a limited role in the initial evaluation of the trauma patient, but may be of use for the evaluation of the spine and diaphragm in patients who are hemodynamically stable.

Chest radiology case exchange program: a paradigm for resident teaching and independent resident learning.

RATIONALE AND OBJECTIVES: The purpose of this study was to test the effectiveness of resident-prepared, independent learning cases in teaching residents chest radiology. MATERIALS AND METHODS: Three 2nd-year residents (one each from the University of Wisconsin, the Oregon Health Sciences University, and the University of Michigan) prepared four chest radiology teaching cases each (total, 12 cases). Radiology residents from each institution were randomly divided into control (n = 30) and experimental (n = 35) groups. Residents from both groups took a pretest of 36 multiple-choice questions covering the material from the 12 teaching cases. Residents in the experimental group reviewed these cases independently, and both groups took the same test (posttest) immediately after the teaching cases had been reviewed and again 3 months later (final test). RESULTS: Test scores were similar across institutions (P > .05) but differed across time and treatment groups (experimental vs control) (P < .0001). Mean differences in test scores between the experimental and control groups at pretest, posttest, and final test were -0.4, +9.0, +4.0, respectively, demonstrating increased performance at posttesting that was still present (though somewhat attenuated) 3 months later at final testing. CONCLUSION: Independent study of resident-prepared chest radiology teaching cases increases the resident's knowledge for as long as 3 months after instruction.

Effectiveness of resident-prepared conferences in teaching imaging utilization guidelines to radiology residents.

RATIONALE AND OBJECTIVES: The authors evaluated the effectiveness of a resident-prepared conference series for teaching imaging utilization guidelines to radiology residents. MATERIALS AND METHODS: Brown University radiology residents (n = 17) gave 61 presentations on imaging utilization to their colleagues during 16 1-hour conferences. The residents were later examined on the topics presented and surveyed about their familiarity with the American College of Radiology appropriateness criteria, their exposure to issues of cost-effectiveness, and their degree of confidence in providing imaging consultation. The same examination and survey were administered to control residents from the University of Wisconsin (n = 14) and the Oregon Health Sciences University (n = 14). Scores were compared by using linear regression and Wilcoxon rank sum tests. RESULTS: Controlling for years in radiology residency, residents at Brown scored on average 16.0% (standard error = 2.2%) higher than residents at the other universities (P < .001). Controlling for institution, 3rd- and 4th-year residents scored on average 7.4% (standard error = 2.1%) higher than 1st- and 2nd-year residents (P = .001). Brown residents expressed more familiarity with American College of Radiology appropriateness criteria and appeared to have more exposure to cost-effectiveness issues in conferences than residents at Wisconsin or Oregon Health Sciences University (P < .005). Residents from the three universities did not differ in their level of confidence in providing imaging consultation. CONCLUSION: Resident-prepared conferences are an effective means of teaching imaging utilization guidelines to residents, but they do not affect the residents' perception of their ability to provide imaging consultation.

Medical students and radiology residents: can they learn as effectively with the same educational materials?

RATIONALE AND OBJECTIVES: The purpose of this study was to evaluate the effectiveness of resident-prepared, independent-learning materials for teaching chest radiology to medical students. MATERIALS AND METHODS: Students from three U.S. medical schools enrolled in radiology clerkships between March 1998 and June 1998 were randomly divided into control (n = 27) and experimental (n = 31) groups. The experimental group studied 12 chest radiology independent-learning cases (intervention) used to teach radiology residents in a previous study. Both groups took a 36-item, multiple-choice test (previously used to test radiology residents) on three occasions (before intervention [pretest], 1 day after intervention [posttest], and 2-4 weeks after intervention [final examination]). Student scores were then compared with resident scores. RESULTS: Mean scores were similar across institutions at pretest, but increases at posttest and final examination scores differed across time, school, and group (P < .005). Mean differences in scores between experimental and control groups at pretest, posttest, and 2-4-week final examination were -0.22, 9.79, and 9.14, respectively, demonstrating increased performance at posttesting that remained present (though slightly attenuated) 2-4 weeks later. Comparing performance, residents had mean pretest scores of 19.2 and students of 14.1, a five-point difference attributable to the residents' greater experience. Both residents and students gained approximately nine points at posttest. At final examination, the difference between residents and students was only 1.4 points, suggesting the experimental program (teaching materials) brought students close to the long-term retention shown by residents. CONCLUSION: Independent study of resident-prepared chest radiology teaching cases increased medical student knowledge for at least 2 or 4 weeks after instruction. Although starting at lower knowledge levels, students experienced gains in knowledge comparable to those of residents, suggesting the same materials can be used to teach both students and residents.

CT in blunt chest trauma: indications and limitations.

Computed tomography (CT) is the imaging modality of choice in the assessment of patients with clinical or radiographic findings suggestive of aortic injury, bone fracture, or diaphragmatic tear following blunt chest trauma. Contrast material-enhanced spiral CT allows detection of both subtle and more obvious aortic tears. CT has overall greater sensitivity than radiography in the detection of pulmonary lacerations and pneumothoraces. CT may be indicated in cases of suspected tracheobronchial injury. CT is of limited use in the assessment of rib fractures because such injuries are of limited clinical significance and can usually be identified at radiography; however, CT provides optimal visualization of thoracic spine fractures and superior assessment of suspected sternal fractures or sternoclavicular dislocation. Targeted spiral CT with sagittal and coronal reformatted images has increased sensitivity and specificity over that provided by conventional axial CT in the detection of diaphragmatic injury. Optimal CT assessment requires careful attention to technique, including the use of intravenously administered contrast material and multiplanar reconstructed images, as well as an awareness of potential pitfalls. Although in many cases diagnosis can be made with confidence on the basis of CT findings, further investigation is often needed to confirm the diagnosis.

Radiologic manifestations of the systemic autoimmune diseases.

Advances in thoracic imaging during the past two decades, such as CT scans and MR imaging, have enhanced our understanding of the pleuropulmonary abnormalities that develop in the systemic autoimmune diseases. In this article, the thoracic radiologic manifestations of several connective tissue diseases (systemic lupus erythematosus, rheumatoid arthritis, Sjögren's syndrome, polymyositis/dermatomyositis, progressive systemic sclerosis, and anklyosing spondylitis), two granulomatous vasculitides, (Wegener's Granulomatosis and Churg-Strauss syndrome), and antiglomerular basement membrane disease are reviewed.

Bronchioloalveolar carcinoma: clinical, histopathologic, and radiologic findings.

Bronchioloalveolar carcinoma is characterized pathologically by a pulmonary neoplasm showing lepidic growth. More than half of all patients with bronchioloalveolar carcinoma are asymptomatic. The most frequent symptoms and signs are cough, sputum, shortness of breath, weight loss, hemoptysis, and fever. Bronchorrhea is unusual and a late manifestation. Nonmucinous bronchioloalveolar carcinoma tends to be more localized and has a lower frequency of bronchogenic spread than mucinous bronchioloalveolar carcinoma. Bronchioloalveolar carcinoma appears radiographically as a single nodule, segmental or lobar consolidation, or diffuse nodules. At computed tomography (CT), the single nodular form appears as a peripheral nodule or localized ground-glass attenuation with or without consolidation, frequently associated with bubblelike areas of low attenuation and open bronchus signs. The lobar consolidative form may demonstrate the CT angiogram and open bronchus signs. The diffuse nodular form appears as multiple nodules or areas of ground-glass attenuation or consolidation. The single nodular form has a better prognosis than the others but may show false-negative results for malignancy at 2-(fluorine-18) fluoro-2-deoxy-D-glucose positron emission tomography.

The spectrum of eosinophilic lung disease: radiologic findings.

PURPOSE: Eosinophilic lung disease includes various disease entities. Each disease manifests different radiologic findings. The purpose of this review is to present the radiologic findings of the spectrum of eosinophilic lung disease. METHOD: We reviewed the radiologic, histologic, and clinical findings of the spectrum of eosinophilic lung disease from the previous reports and our experiences. RESULTS: Simple pulmonary eosinophilia is characterized by transient and migrating opacities on chest radiography. Acute eosinophilic pneumonia is characterized by acute clinical symptoms and signs and rapid changes of radiographic diffuse reticular lesions. Chronic eosinophilic pneumonia, with more prolonged symptom duration, history of asthma, occurrence of relapse, and radiologic features of subpleural consolidation, can be differentiated from acute eosinophilic pneumonia. Allergic bronchopulmonary aspergillosis presents with bilateral central bronchiectasis with or without mucoid impaction. Although these diseases show specific radiographic findings, some show overlapping radiographic features. High-resolution CT enables characterization of parenchymal lesions further by showing internal and marginal features and the exact extent of the lesions. Extrapulmonary organs are involved in Churg-Strauss syndrome and idiopathic hypereosinophilic syndrome. Asthma is associated with Churg-Strauss syndrome, allergic bronchopulmonary aspergillosis, chronic eosinophilic pneumonia, and bronchocentric granulomatosis. CONCLUSION: Integration of clinical, laboratory, and radiologic findings enables initial and differential diagnoses of various eosinophilic lung diseases.

Simulated dose reduction in conventional chest CT: validation study.

PURPOSE: To validate a technique of computer-simulated dose reduction for conventional chest computed tomography (CT). MATERIALS AND METHODS: In 27 patients, CT scans were obtained at 200, 100, and 40 mAs at two levels. The raw data from the 200-mAs scan were modified on a computer workstation to simulate the increased noise present on 100- and 40-mAs scans. Real and simulated 100- and 40-mAs images were independently assessed in random order for overall image quality and radiologic findings by four subspecialty-trained chest radiologists who were blinded to the technique. The four observers were given paired real and simulated images. They were asked to identify the real image and note any difference in diagnostic quality. RESULTS: No difference was seen in overall image quality or radiologic findings between real and simulated images (P > .05). In the paired comparison, 433 of 864 (50.1%) real images were correctly identified. CONCLUSION: Computer modification of 200-mAs raw scan data to simulate 100- and 40-mAs noise levels produces reconstructed images indistinguishable from real 100- and 40-mAs scans. This technique provides realistic reduced-dose images without patient radiation exposure and with identical image registration and motion artifact.

Neofissure after lobectomy of the right lung: radiographic and CT findings.

PURPOSE: To document the postlobectomy radiographic and computed tomographic (CT) appearance of neofissures of the right lung. MATERIALS AND METHODS: Chest radiographs and CT scans from 25 patients who had undergone right lobectomy were assessed by two chest radiologists, and decisions on the findings were reached by consensus. Analyses included orientation of the neofissure and lobar reorientation of the remaining lobes. RESULTS: Neofissure location after right upper lobectomy (n = 13) was superior and anterior compared with the location of the left major fissure on both lateral radiographs and CT scans. After right middle lobectomy (n = 4), the neofissure had less vertical orientation than the left major fissure (the highest posterior portion was lower and the lowest anterior portion was higher than the left major fissure) on both lateral radiographs and CT scans. After right lower lobectomy (n = 8), two types of lobar reorientation and, accordingly, two types of neofissure were observed in the right lower lung zone (posteriorly and anteriorly high, respectively, on lateral radiographs). CONCLUSION: Analyses of neofissures on lateral radiographs and CT scans enable differentiation among various kinds of lobectomy.

Diagnosis of diaphragmatic trauma with helical CT in a swine model.

OBJECTIVE: The purpose of this study was to determine whether diaphragmatic injury can be accurately diagnosed with helical CT in a swine model. The hypothesis of our study was that thin-section helical CT with sagittal and coronal reformations can reliably detect injury of the diaphragm. MATERIALS AND METHODS: The study was performed in a swine model because of the similarity of the swine thorax to the human thorax. Ten swine had a limited abdominal helical CT (enteral contrast; 3-mm collimation; pitch, 1) before and after surgical creation of a 6-cm posterolateral laceration in the left hemidiaphragm. A repeat scan was obtained after 5 cm of gastric fundus was sutured through the laceration. The gastric fundus was used because it is the most commonly herniated viscus in human diaphragmatic injury. No IV contrast was used. Control, laceration, and herniation scans were reconstructed with 1.0-mm overlap and reformated in axial, sagittal, and coronal planes. Three observers scored each reformation as control or injury (defined as laceration or herniation) in a blinded and randomized fashion. RESULTS: Using helical CT, the observers were able to distinguish diaphragmatic injury from controls (p < .0001). The sensitivity and specificity were 92% and 87%, respectively, for sagittal reformations; 85% and 87%, respectively, for coronal reformations; and 73% and 80%, respectively, for axial reformations. Sagittal reformations proved superior to coronal or axial reformations (p = .01). The results were independent of individual observers: We found no significant difference in accuracy among the three observers. CONCLUSION: Helical CT can accurately detect diaphragmatic injury in a swine model.

Disease progression in usual interstitial pneumonia compared with desquamative interstitial pneumonia. Assessment with serial CT.

OBJECTIVE: To determine the outcome of areas of ground-glass attenuation and assess disease progression on serial high-resolution CT (HRCT) scans of patients with biopsy specimen-proved usual interstitial pneumonia (UIP) and desquamative interstitial pneumonia (DIP). MATERIALS AND METHODS: Twelve patients with biopsy specimen-proved UIP and 11 patients with biopsy specimen-proved DIP who had initial and follow-up HRCT scans (median interval, 10 months) were reviewed. Eleven patients with UIP and 11 with DIP received treatment between the initial and follow-up CT scans. The scans were evaluated for the presence and extent of ground-glass attenuation, irregular linear opacities and honeycombing, and overall extent of parenchymal involvement. RESULTS: On initial CT scans, all 12 patients with UIP had areas of ground-glass attenuation (mean +/- SD extent, 30 +/- 16%) and irregular lines (mean +/- SD extent, 17 +/- 7%) and 10 patients had honeycombing (mean +/- SD extent, 10 +/- 6%). All 11 patients with DIP had areas of ground-glass attenuation on initial HRCT scans (mean +/- SD extent, 51 +/- 26%), 5 patients had irregular linear opacities (mean +/- SD extent, 5 +/- 5%), and 1 patient had honeycombing. Nine of the 12 patients with UIP showed increase in the extent of ground-glass attenuation (n = 6) or progression to irregular lines (n = 2) or honeycombing (n = 4) on follow-up as compared with only 2 patients with DIP who showed progression to irregular lines (n = 1) or honeycombing (n = 1) (p < 0.01 chi 2 test). CONCLUSION: In patients with UIP, areas of ground-glass attenuation usually increase in extent or progress to fibrosis despite treatment. Areas of ground-glass attenuation in most patients with DIP remain stable or improve with treatment.

Detection and differential diagnosis of pulmonary infections and tumors in patients with AIDS: value of chest radiography versus CT.

OBJECTIVE: The purpose of this study was to compare the sensitivity and specificity of chest radiography with those of CT in the detection of pulmonary infections and tumors in patients with AIDS. MATERIALS AND METHODS: The study was retrospective and included the radiographs and CT scans of 139 patients. Eighty-nine had one proven thoracic complication, 17 had two proven thoracic complications, and 33 had no active intrathoracic disease at the time of the examinations. The radiographs and CT scans were interpreted blindly by two independent observers from different institutions. The observers assessed for the presence or absence of intrathoracic disease and recorded the most likely diagnosis and the degree of confidence in that diagnosis. RESULTS: The patients were more commonly correctly identified as having or not having intrathoracic disease on the basis of CT findings than on the basis of radiographic findings ( p < .01, chi-square test). Of the 106 patients with intrathoracic complications, 90% (191 of 212 interpretations) were correctly identified by the two observers on the radiograph and 96% (204 of 212 interpretations) at CT. Of 33 patients without intrathoracic disease, 73% (48 of 66 interpretations) were correctly identified at radiography and 86% (57 of 66 interpretations) at CT. Of 89 patients with one proved thoracic complication, the observers confident in their first-choice diagnosis in 34% of the cases (61 of 178 interpretations) at chest radiography and in 47% (83 of 178 interpretations) at CT. This diagnosis was correct in 67% (41 of 61) of confident radiographic interpretations as compared with 87% (72 of 83) of interpretations at CT (p < .01, chi-square test). CONCLUSION: CT is superior to chest radiography in allowing identification of patients with and without thoracic disease and in the differential diagnosis of pulmonary complications of patients with AIDS. However, the improvement in differential diagnosis is modest. Because in most cases the radiographs and CT scans were obtained as part of the clinical evaluation, the study is probably biased toward problematic clinical cases. In the majority of patients, the chest radiograph provides adequate information and CT is not warranted.