A Quantitative Approach to Distinguish Pneumonia From Atelectasis Using Computed Tomography Attenuation.

OBJECTIVE: It is known that atelectasis demonstrates greater contrast enhancement than pneumonia on computed tomography (CT). However, the effectiveness of using a Hounsfield unit (HU) threshold to distinguish pneumonia from atelectasis has never been shown. The objective of the study is to demonstrate that an HU threshold can be quantitatively used to effectively distinguish pneumonia from atelectasis. METHODS: Retrospectively identified CT pulmonary angiogram examinations that did not show pulmonary embolism but contained nonaerated lungs were classified as atelectasis or pneumonia based on established clinical criteria. The HU attenuation was measured in these nonaerated lungs. Receiver operating characteristic (ROC) analysis was performed to determine the area under the ROC curve, sensitivity, and specificity of using the attenuation to distinguish pneumonia from atelectasis. RESULTS: Sixty-eight nonaerated lungs were measured in 55 patients. The mean (SD) enhancement was 62 (18) HU in pneumonia and 119 (24) HU in atelectasis (P < 0.001). A threshold of 92 HU diagnosed pneumonia with 97% sensitivity (confidence interval [CI], 80%-99%) and 85% specificity (CI, 70-93). Accuracy, measured as area under the ROC curve, was 0.97 (CI, 0.89-0.99). CONCLUSIONS: We have established that a threshold HU value can be used to confidently distinguish pneumonia from atelectasis with our standard CT pulmonary angiogram imaging protocol and patient population. This suggests that a similar threshold HU value may be determined for other scanning protocols, and application of this threshold may facilitate a more confident diagnosis of pneumonia and thus speed treatment.

Histiocytic disorders of the chest: imaging findings.

Histiocytic disorders of the chest comprise a broad spectrum of diseases. The lungs may be involved in isolation or as part of systemic disease. Some of these disorders are primary and have unknown etiology, and others result from a histiocytic response to a known cause. Among primary histiocytic disorders, pulmonary Langerhans cell histiocytosis (PLCH) is the most common; others include Erdheim-Chester disease and Rosai-Dorfman disease. Adult PLCH occurs almost exclusively in adults aged 20-40 years who smoke. Pediatric PLCH is extremely rare and typically occurs as part of multisystemic disease. Erdheim-Chester disease affects middle-aged and older adults; thoracic involvement usually occurs as part of systemic disease. Rosai-Dorfman disease affects children and young adults and manifests as painless cervical lymphadenopathy. Examples of secondary histiocytic disorders are storage diseases such as Gaucher disease, Niemann-Pick disease, and Fabry disease; pneumoconiosis such as silicosis and coal workers' pneumoconiosis; and infections such as Whipple disease and malakoplakia. These disorders are characterized at histopathologic examination on the basis of infiltration of alveoli or the pulmonary interstitium by histiocytes, which are a group of cells that includes macrophages and dendritic cells. Dendritic cells are a heterogeneous group of nonphagocytic antigen-presenting immune cells. Immunohistochemical markers help to distinguish among various primary histiocytic disorders. Characteristic radiologic findings in the appropriate clinical context may obviate biopsy to establish a correct diagnosis. However, in the absence of these findings, integration of clinical, pathologic, and radiologic features is required to establish a diagnosis.

Pulmonary effects of i.v. injection of crushed oral tablets: "excipient lung disease".

OBJECTIVE: When crushed oral tablets are injected i.v., their filler material (excipient) can induce a potentially fatal foreign-body reaction in pulmonary arterioles, presenting as dyspnea and pulmonary hypertension with centrilobular nodules on CT. We will describe the imaging and pathologic features of "excipient lung disease." CONCLUSION: The radiologist has a critical role in recognizing and reporting excipient lung disease because the referring clinician may be unaware of the patient's i.v. drug abuse.

Thoracic diseases associated with HIV infection in the era of antiretroviral therapy: clinical and imaging findings.

The human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS) pandemic has entered its 4th decade. Since the introduction of combination antiretroviral therapy (ART) in 1996, the number of AIDS-related deaths has plateaued worldwide. Today, owing to the effectiveness of ART, the HIV-infected population is aging and HIV infection has become a chronic illness. Non-AIDS comorbidities are increasing, and the spectrum of HIV-related thoracic diseases is evolving. In developed countries, bacterial pneumonia has become more common than Pneumocystis pneumonia. Its imaging appearance depends on the responsible organism, most commonly Streptococcus pneumoniae. Mycobacterium tuberculosis continues to be a major threat. Its imaging patterns vary depending on CD4 count. Primary lung cancer and Hodgkin lymphoma are two important non-AIDS-defining malignancies that are increasingly encountered at chest imaging. Human herpesvirus 8, also known as Kaposi sarcoma-associated herpesvirus (KSHV), is strongly linked to HIV-related diseases, including Kaposi sarcoma, multicentric Castleman disease, KSHV inflammatory cytokine syndrome, and primary effusion lymphoma. Immune reconstitution inflammatory syndrome is a direct complication of ART whose manifestations vary with the underlying disease. Given the high rate of smoking among HIV-infected patients, chronic obstructive pulmonary disease is another important cause of morbidity and mortality. A high degree of suspicion is required for the early diagnosis of pulmonary arterial hypertension and lymphocytic interstitial pneumonia, given their nonspecific manifestations. Finally, multilocular thymic cyst manifests as a cystic anterior mediastinal mass. Recognition of the clinical and radiologic manifestations of these less traditional HIV-related diseases can expedite diagnosis and treatment in the ART era.

Tumors and tumorlike conditions of the large airways.

OBJECTIVE: Large-airway tumors and tumorlike conditions are uncommon, but a systematic approach aids in narrowing the differential diagnosis. In this article, we describe an approach to dealing with large-airway lesions and discuss their imaging characteristics and clinical presentations. CONCLUSION: We have found it useful to separate these entities into groups on the basis of the distribution pattern (focal vs diffuse) and location (trachea vs bronchi).

Imaging of granulomatous fibrosing mediastinitis.

OBJECTIVE: The purpose of this article is to review and illustrate the pathogenesis, natural history, imaging features, and treatment of granulomatous fibrosing mediastinitis. CONCLUSION: Granulomatous fibrosing mediastinitis is an infiltrative disorder characterized by encasement of the mediastinal viscera; in most cases in the United States, it represents an idiosyncratic immune response to histoplasma. Familiarity with the various imaging features of fibrosing mediastinitis is important for prompt and accurate diagnosis as well as for planning and guiding surgical and less-invasive treatments.

Imaging of the diaphragm: anatomy and function.

The diaphragm is the primary muscle of ventilation. Dysfunction of the diaphragm is an underappreciated cause of respiratory difficulties and may be due to a wide variety of entities, including surgery, trauma, tumor, and infection. Diaphragmatic disease usually manifests as elevation at chest radiography. Functional imaging with fluoroscopy (or ultrasonography or magnetic resonance imaging) is a simple and effective method of diagnosing diaphragmatic dysfunction, which can be classified as paralysis, weakness, or eventration. Diaphragmatic paralysis is indicated by absence of orthograde excursion on quiet and deep breathing, with paradoxical motion on sniffing. Diaphragmatic weakness is indicated by reduced or delayed orthograde excursion on deep breathing, with or without paradoxical motion on sniffing. Eventration is congenital thinning of a segment of diaphragmatic muscle and manifests as focal weakness. Treatment of diaphragmatic paralysis depends on the cause of the dysfunction and the severity of the symptoms. Treatment options include plication and phrenic nerve stimulation. Supplemental material available at http://radiographics.rsna.org/lookup/suppl/doi:10.1148/rg.322115127/-/DC1.

Tumorlike conditions of the pleura.

Tumorlike conditions of the pleura are rare, but diagnosis is facilitated by recognizing certain imaging patterns and interpreting them in the clinical context. A tumorlike condition of the pleura is any nonneoplastic lesion of the pleura itself, or within the pleural space, that resembles a tumor. An approach to diagnosis of the tumorlike conditions of the pleura is provided, and these conditions are grouped into focal or diffuse conditions, with an emphasis on specific imaging features. Focal tumorlike conditions of the pleura include pleural plaque, thoracic splenosis, thoracic endometriosis causing catamenial pneumothorax, and pseudotumor caused by pleural effusion. Thoracic splenosis should be considered in a patient who has a healed left lower rib fracture, an absent spleen, and left lower pleural nodules. Thoracic endometriosis with catamenial pneumothorax should be considered in a woman of childbearing age who presents with right scapular pain and recurrent pneumothorax occurring at or around the onset of menses. Extrapleural hematoma is a nonpleural mimic of pleural tumor and shares some imaging features with focal tumorlike conditions of the pleura, despite residing in the extrapleural space. Diffuse tumorlike conditions of the pleura include diffuse pleural thickening and rare conditions such as Erdheim-Chester disease and diffuse pulmonary lymphangiomatosis. Erdheim-Chester disease should be considered when diffuse pleural thickening occurs with a perirenal soft-tissue halo or distal femoral sclerosis. Diffuse pulmonary lymphangiomatosis should be considered when findings include diffuse pleural thickening, interlobular septal and peribronchovascular interstitial thickening, and mediastinal fat infiltration limited to the thorax and when these findings persist despite diuretic therapy.

Organizing pneumonia in recipients of hematopoietic stem cell transplantation: CT features in 16 patients.

PURPOSE: To evaluate computed tomographic (CT) scans of patients with organizing pneumonia (OP) complicating hematopoietic stem cell transplantation (HSCT). MATERIALS AND METHODS: A review of patients who underwent HSCT at our institution identified 16 patients who had documented OP on biopsy. Computed tomographic scans were reviewed by 2 thoracic radiologists. RESULTS: Ground glass opacities (GGO) were seen in 15 patients, consolidation in 8 patients, linear opacities in 8 patients, traction bronchiectasis in 2 patients, and septal thickening in 2 patients. Ground glass opacity was the dominant abnormality in 7 patients, consolidation in 4 patients, and linear opacities in 5 patients. Peribronchovascular distribution was found in 4 patients, peripheral in 2 patients, diffuse in 3 patients; upper lung predominance was found in 10 patients, and lower lung predominance in 5 patients. CONCLUSION: The principal computed tomographic features of OP after HSCT are ground glass opacities, consolidation and linear opacities, with upper lung predominance. Allowing for a possible sampling bias, these findings differ from those reported in cryptogenic OP and OP from other causes.

Peer Learning Through Multi-Institutional Web-based Case Conferences: Perceived Value (and Challenges) From Abdominal, Cardiothoracic, and Musculoskeletal Radiology Case Conference Participants.

RATIONALE AND OBJECTIVES: Peer learning is a case-based group-learning model intended to improve performance. In this descriptive paper, we describe multi-institutional, multi-subspecialty, web-based radiology case conferences and summarize the participants' experiences. MATERIALS AND METHODS: A semi-structured, 27-question survey was administered to radiologists participating in abdominal, cardiothoracic, and musculoskeletal case conferences. Survey questions included demographics, perceived educational value and challenges experienced. Survey question formats were continuous, binary, five-point Likert scale or text-based. The measures of central tendencies, proportions of responses and patterns were tabulated. RESULTS: From 57 responders, 12/57 (21.1%) were abdominal, 16/57 (28.1%) were cardiothoracic, and 29/57 (50.8%) were musculoskeletal conference participants; 50/56 (89.3%) represented academic practice. Median age was 45 years (range 35-74); 43/57 (75.4%) were male. Geographically, 16/52 (30.8%) of participants were from the East Coast, 16/52 (30.8%) Midwest, 18/52 (34.6%) West Coast, and 2/52 (3.8%) International. The median reported educational value was 5/5 (interquartile range 5-5). Benefits of the case conference included education (50/95, 52.6%) and networking (39/95, 41.1%). Participants reported presenting the following cases: "great call" 32/48 (66.7%), learning opportunity 32/48 (66.7%), new knowledge 41/49 (83.7%), "zebras" 46/49 (93.9%), and procedural-based 16/46 (34.8%). All 51/51 (100%) of responders reportedly gained new knowledge, 49/51 (96.1%) became more open to group discussion, 34/51 (66.7%) changed search patterns, and 50/51 (98%) would continue to participate. Reported challenges included time zone differences and support from departments for a protected time to participate. CONCLUSION: Peer learning through multi-institutional case conferences provides educational and networking opportunities. Current challenges and desires include having department-supported protected time and ability to receive continuing medical education credit.

Imaging of thoracic lymphatic diseases.

OBJECTIVE: This review will focus on radiographic description of lymphangiomas, lymphangiohemangiomas, pulmonary lymphangiomatosis, lymphangiectasis, lymphangioleiomyomatosis, lymphatic dysplasia, and traumatic lymphatic injury. CONCLUSION: Diseases of the thoracic lymphatic system have a wide variety of unique radiographic manifestations, all of which can be explained by the underlying pathophysiology and relationship to the normal distribution of lymphatics in the chest.

Hypersensitivity pneumonitis: a historical, clinical, and radiologic review.

Most cases of hypersensitivity pneumonitis develop only after many years of inhaling allergens, which include microbes, animal or plant proteins, and certain chemicals that form haptens. The initial clinical presentation is either episodes of acute illness with dyspnea and prominent constitutional symptoms, such as fever, or an insidious onset of dyspnea, coughing, and weight loss, sometimes with superimposed acute episodes. The histopathologic process consists of chronic inflammation of the bronchi and peribronchiolar tissue, often with poorly defined granulomas and giant cells in the interstitium or alveoli. Fibrosis and emphysema may develop. The radiologic findings include diffuse ground-glass opacification, centrilobular ground-glass opacities, air trapping, fibrosis, lung cysts, and emphysema. The histologic and radiologic features in some cases may resemble those of usual interstitial pneumonia or nonspecific interstitial pneumonia. The diagnosis usually rests on a variable combination of findings from history, serology, radiography, lung biopsy, and bronchoalveolar lavage, which characteristically reveals a lymphocyte content of more than 30%, often with an increased CD4-to-CD8 ratio of T cells. Treatment includes avoiding the allergen, if possible, and, in severe cases, systemic corticosteroids. The long-term prognosis is usually good, but some patients develop severe respiratory insufficiency, and a few die of the disease.

18F FDG-PET/CT findings in recurrent respiratory papillomatosis.

Recurrent respiratory papillomatosis (RRP) is an indolent and primary disease of the larynx and the trachea and rarely extends to smaller airways. F-18 fluoro-2-deoxy-D-glucose positron emission tomography and computed tomography (FDG-PET/CT) evaluation in this condition has not been reported earlier. We report FDG-PET/CT findings in a case of RRP that included a large papillomatous lung mass resembling cancer.

Radiologic computed tomography features of Mycobacterium abscessus in cystic fibrosis.

INTRODUCTION: Mycobacterium abscessus infection in cystic fibrosis (CF) patients can lead to poor outcomes. Early diagnosis is important, but there are no studies outlining specific imaging features of M. abscessus in CF. OBJECTIVES: To describe the computed tomography (CT) findings of early M. abscessus infection in our CF population. METHODS: Thirteen CF patients with sputum cultures positive for M. abscessus from 2006 to 2013 were identified at our institution. Clinical characteristics including culture dates and lung function were reviewed. Positive cultures were classified as "disease" versus "colonization" based on published criteria. Chest CT scans were reviewed at times closest to initial infection, and features including bronchiectasis, mucous plugging, consolidation, ground glass opacities, nodules, and cavitation were evaluated. Brody scores were calculated to evaluate extent of CF lung disease. RESULTS: All patients had bronchiectasis and mucous plugging, with 10 of 13 (76.9%) in an upper lobe distribution. Consolidation was seen in 12 of 13 (92.3%) patients, 8 (61.5%) patients had nodules, and 5 (38.5%) with cavitation. The average Brody score was 59.5, which was no different than previously described CF cohorts without M. abscessus. There were no significant differences between subjects with disease versus colonization. CONCLUSION: The most common CT features of early M. abscessus in our CF population include bronchiectasis, mucus plugging, and consolidation, but the findings did not reveal a unique radiologic signature. CT at this initial time point may not distinguish early M. abscessus infection from background lung disease or mycobacterial colonization in CF patients.

Viral pneumonia after hematopoietic stem cell transplantation: high-resolution CT findings.

Hematopoietic stem cell transplantation (HSCT) is the treatment of choice for many hematologic malignancies and nonmalignant disorders of bone marrow function. Pulmonary infections from bacterial, fungal, and viral organisms are a major cause of morbidity and mortality in patients after HSCT. The radiographic and high-resolution computed tomography (HRCT) findings of the different lower respiratory tract viral infections are quite similar. Findings of viral pneumonia on HRCT include small poorly defined centrilobular nodules and patchy, often bilateral, areas of peribronchial ground-glass opacity and consolidation. Air trapping may be present because of associated bronchiolitis. Interlobular septal thickening, bronchial wall thickening, and tree-in-bud opacities may also be present. Advanced viral pneumonia with diffuse alveolar damage is characterized by patchy or confluent consolidation and ground-glass opacities. Although nonspecific, in the correct clinical setting, these HRCT findings can help suggest the diagnosis of viral pneumonia in recipients of HSCT.

Crus Atrophy: Accuracy of Computed Tomography in Diagnosis of Diaphragmatic Paralysis.

PURPOSE: The aim of this study was to measure the association between crus atrophy as depicted by computed tomography (CT) and fluoroscopic diagnosis of hemidiaphragmatic paralysis in patients with suspected diaphragmatic dysfunction. MATERIALS AND METHODS: A retrospective review of patient data was approved by our institutional review board and was HIPPA-compliant. We reviewed 90 patients who had undergone diaphragmatic fluoroscopy; 72 had CT scans available for measurement of crus thickness at the levels of the celiac and superior mesenteric arteries and the L1 vertebral body. Receiver operating characteristic analysis was used to determine the threshold of crus thinning that best distinguished a paralyzed hemidiaphragm from a nonparalyzed one. RESULTS: Hemidiaphragmatic paralysis caused significant crus thinning at the celiac artery level (mean±SD, 1.7±0.6 vs. 3.6±1.3 mm, P=0.017, on the right; 1.1±0.4 vs. 3.0±1.4 mm, P=0.001, on the left) and the L1 vertebral level (mean±SD, 1.5±0.7 vs. 4.4±1.6 mm, P=0.018, on the right; 1.5±0.6 vs. 3.6+1.7 mm, P=0.017, on the left). On axial CT, thinning to ≤2.5 mm at the celiac artery level identified paralysis of the hemidiaphragm with a sensitivity of 100% and a specificity of 86% on the right and with a sensitivity of 100% and a specificity of 64% on the left. On coronal CT, thinning to ≤2.5 mm at the L1 vertebral level identified paralysis of the hemidiaphragm with a sensitivity of 100% and a specificity of 88% on the right and with a sensitivity of 100% and a specificity of 77% on the left. CONCLUSIONS: Atrophy of the crus assessed by CT is a good discriminator of paralyzed versus nonparalyzed hemidiaphragm in patients with suspected diaphragmatic dysfunction.

Imaging of Pulmonary Manifestations of Connective Tissue Diseases.

Connective tissue diseases (CTDs) are a heterogeneous group of conditions characterized by circulating autoantibodies and autoimmune-mediated organ damage. Common CTDs with lung manifestations are rheumatoid arthritis, scleroderma or systemic sclerosis, Sjögren syndrome, polymyositis/dermatomyositis, systemic lupus erythematosis, mixed connective tissue disease, and undifferentiated connective tissue disease. The most common histopathologic patterns of CTD-related interstitial lung disease are nonspecific interstitial pneumonia, usual interstitial pneumonia, organizing pneumonia, and lymphoid interstitial pneumonia. Drug treatment of CTDs can cause complications, including opportunistic infection.