Managing Incidental Findings on Thoracic CT: Lung Findings. A White Paper of the ACR Incidental Findings Committee.

The ACR Incidental Findings Committee presents recommendations for managing incidentally detected lung findings on thoracic CT. The Chest Subcommittee is composed of thoracic radiologists who endorsed and developed the provided guidance. These recommendations represent a combination of current published evidence and expert opinion and were finalized by informal iterative consensus. The recommendations address commonly encountered incidental findings in the lungs and are not intended to be a comprehensive review of all pulmonary incidental findings. The goal is to improve the quality of care by providing guidance on management of incidentally detected thoracic findings.

CT for Evaluation of Hemoptysis.

Hemoptysis, which is defined as expectoration of blood from the alveoli or airways of the lower respiratory tract, is an alarming clinical symptom with an extensive differential diagnosis. CT has emerged as an important noninvasive tool in the evaluation of patients with hemoptysis, and the authors present a systematic but flexible approach to CT interpretation. The first step in this approach involves identifying findings of parenchymal and airway hemorrhage. The second step is aimed at determining the mechanism of hemoptysis and whether a specific vascular supply can be implicated. Hemoptysis can have primary vascular and secondary vascular causes. Primary vascular mechanisms include chronic systemic vascular hypertrophy, focally damaged vessels, a dysplastic lung parenchyma with systemic arterial supply, arteriovenous malformations and fistulas, and bleeding at the capillary level. Evaluating vascular mechanisms of hemoptysis at CT also entails determining if a specific vascular source can be implicated. Although the bronchial arteries are responsible for most cases of hemoptysis, nonbronchial systemic arteries and the pulmonary arteries are important potential sources of hemoptysis that must be recognized. Secondary vascular mechanisms of hemoptysis include processes that directly destroy the lung parenchyma and processes that directly invade the airway. Understanding and employing this approach allow the diagnostic radiologist to interpret CT examinations accurately in patients with hemoptysis and provide information that is best suited to directing subsequent treatment. ©RSNA, 2021.

Managing Incidental Findings on Thoracic CT: Mediastinal and Cardiovascular Findings. A White Paper of the ACR Incidental Findings Committee.

The ACR Incidental Findings Committee presents recommendations for managing incidentally detected mediastinal and cardiovascular findings found on CT. The Chest Subcommittee was composed of thoracic radiologists who developed the provided guidance. These recommendations represent a combination of current published evidence and expert opinion and were finalized by informal iterative consensus. The recommendations address the most commonly encountered mediastinal and cardiovascular incidental findings and are not intended to be a comprehensive review of all incidental findings associated with these compartments. Our goal is to improve the quality of care by providing guidance on how to manage incidentally detected thoracic findings.

Malignancy risk estimation of pulmonary nodules in screening CTs: Comparison between a computer model and human observers.

PURPOSE: To compare human observers to a mathematically derived computer model for differentiation between malignant and benign pulmonary nodules detected on baseline screening computed tomography (CT) scans. METHODS: A case-cohort study design was chosen. The study group consisted of 300 chest CT scans from the Danish Lung Cancer Screening Trial (DLCST). It included all scans with proven malignancies (n = 62) and two subsets of randomly selected baseline scans with benign nodules of all sizes (n = 120) and matched in size to the cancers, respectively (n = 118). Eleven observers and the computer model (PanCan) assigned a malignancy probability score to each nodule. Performances were expressed by area under the ROC curve (AUC). Performance differences were tested using the Dorfman, Berbaum and Metz method. Seven observers assessed morphological nodule characteristics using a predefined list. Differences in morphological features between malignant and size-matched benign nodules were analyzed using chi-square analysis with Bonferroni correction. A significant difference was defined at p < 0.004. RESULTS: Performances of the model and observers were equivalent (AUC 0.932 versus 0.910, p = 0.184) for risk-assessment of malignant and benign nodules of all sizes. However, human readers performed superior to the computer model for differentiating malignant nodules from size-matched benign nodules (AUC 0.819 versus 0.706, p < 0.001). Large variations between observers were seen for ROC areas and ranges of risk scores. Morphological findings indicative of malignancy referred to border characteristics (spiculation, p < 0.001) and perinodular architectural deformation (distortion of surrounding lung parenchyma architecture, p < 0.001; pleural retraction, p = 0.002). CONCLUSIONS: Computer model and human observers perform equivalent for differentiating malignant from randomly selected benign nodules, confirming the high potential of computer models for nodule risk estimation in population based screening studies. However, computer models highly rely on size as discriminator. Incorporation of other morphological criteria used by human observers to superiorly discriminate size-matched malignant from benign nodules, will further improve computer performance.

Update in the evaluation of the solitary pulmonary nodule.

A solitary pulmonary nodule (SPN) is defined as a round opacity that is smaller than 3 cm. It may be solid or subsolid in attenuation. Semisolid nodules may have purely ground-glass attenuation or be partly solid (mixed solid and ground-glass attenuation). The widespread use of multidetector computed tomography (CT) has increased the detection of SPNs. Although clinical assessment of patients' risk factors for malignancy--such as age, smoking history, and history of malignancy--is important to determine appropriate treatment, in the recently published Fleischner guidelines for subsolid nodules, smoking history does not factor into their recommendations for management because there is an increasing incidence of lung adenocarcinoma in younger and nonsmoking patients. At imaging evaluation, obtaining prior chest radiographs or CT images is useful to assess nodule growth. Further imaging evaluation, including CT enhancement studies and positron emission tomography (PET), helps determine the malignant potential of solid SPNs. For subsolid nodules, initial follow-up CT is performed at 3 months to determine persistence, because lesions with an infectious or inflammatory cause can resolve in the interval. CT enhancement studies are not applicable for subsolid nodules, and PET is of limited utility because of the low metabolic activity of these lesions. Because of the likelihood that persistent subsolid nodules represent adenocarcinoma with indolent growth, serial imaging reassessment for a minimum of 3 years and/or obtaining tissue samples for histologic analysis are recommended. In the follow-up of subsolid SPNs, imaging features that indicate an increased risk for malignancy include an increase in size, an increase in attenuation, and development of a solid component.

Nonsurgical extracardiac vascular shunts in the thorax: clinical and imaging characteristics.

Extracardiac nonsurgical vascular shunts in the thorax are a group of well-recognized heterogeneous conditions, frequently symptomatic, in which there is diversion of blood flow from one vessel to another or from a vessel to a cardiac chamber. The authors describe and classify many of these nonsurgical extracardiac shunts or fistulas according to their source and endpoint (eg, systemic-to-systemic, systemic-to-pulmonic, pulmonic-to-systemic, and pulmonic-to-pulmonic) and to whether the oxygenated blood mixes with deoxygenated systemic venous flow (left-to-right shunts), deoxygenated blood bypasses the pulmonary capillary bed (right-to-left shunts), or oxygenated blood recirculates (left-to-left shunts). Clinical manifestations and imaging appearances of these conditions are highlighted.

Lipoid pneumonia: spectrum of clinical and radiologic manifestations.

OBJECTIVE: Lipoid pneumonia results from accumulation of lipids in the alveoli and can be either exogenous or endogenous in cause based on the source of the lipid. Exogenous lipoid pneumonia is caused by inhalation or aspiration of animal fat or vegetable or mineral oil. Endogenous lipoid pneumonia is usually associated with bronchial obstruction. The purpose of this article is to review the pathogenesis and clinical and radiologic manifestations of exogenous and endogenous lipoid pneumonia. CONCLUSION: The ability to recognize the radiologic manifestations of lipoid pneumonia is important because, in the appropriate clinical setting, these findings can be diagnostic.

Imaging of small airways disease.

Small airways disease includes a spectrum of inflammatory and fibrotic pulmonary diseases centered on the small conducting airways. High-resolution computed tomography plays a key role in the detection and classification of small airways disease and, when combined with relevant clinical and pathologic findings, leads to a more accurate diagnosis. The imaging manifestations of small airways disease on high-resolution computed tomography may be direct or indirect signs of small airway involvement and include centrilobular nodules and branching nodular (tree-in-bud) opacities, or the demonstration of mosaic attenuation that is typically exaggerated on expiratory computed tomography. This article reviews the normal anatomy and histology of bronchioles and the clinical, pathologic, and imaging features of small airways diseases.

Silicone pulmonary embolism: report of 10 cases and review of the literature.

OBJECTIVE: To assess patient outcome and imaging findings of patients with pulmonary embolism of fluid silicone. METHODS: Medical records and imaging examinations of 10 patients with respiratory distress after illicit injection of fluid silicone were reviewed. Population consisted of 8 male (6 male-to-female transsexuals) and 2 female subjects. RESULTS: Average age was 29 years. Most common injection sites were gluteal and trochanteric. Respiratory symptoms developed between 15 minutes and 2 days after silicone injection. Five referred fever, 6 developed adult respiratory distress syndrome, and 2 subsequently died. Alveolar hemorrhage was demonstrated on pathological examination in 6, with silicone vacuoles in the lung parenchyma in 3. Computed tomography demonstrated peripheral ground glass opacities with interlobular septal thickening in all and peripheral airspace disease in 7. CONCLUSIONS: Illicit injection of large volumes of fluid silicone for cosmetic purposes is associated with pulmonary embolism and acute alveolar hemorrhage and is associated with a significant mortality.

Mucoid impactions: finger-in-glove sign and other CT and radiographic features.

Mucoid impaction is a relatively common finding at chest radiography and computed tomography (CT). Both congenital and acquired abnormalities may cause mucoid impaction of the large airways that often manifests as tubular opacities known as the finger-in-glove sign. The congenital conditions in which this sign most often appears are segmental bronchial atresia and cystic fibrosis. The sign also may be observed in many acquired conditions, include inflammatory and infectious diseases (allergic bronchopulmonary aspergillosis, broncholithiasis, and foreign body aspiration), benign neoplastic processes (bronchial hamartoma, lipoma, and papillomatosis), and malignancies (bronchogenic carcinoma, carcinoid tumor, and metastases). To point to the correct diagnosis, the radiologist must be familiar with the key radiographic and CT features that enable differentiation among the various likely causes. CT is more useful than chest radiography for differentiating between mucoid impaction and other disease processes, such as arteriovenous malformation, and for directing further diagnostic evaluation. In addition, knowledge of the patient's medical history, clinical symptoms and signs, and predisposing factors is important.

"Crazy-paving" pattern at thin-section CT of the lungs: radiologic-pathologic overview.

The "crazy-paving" pattern is a common finding at thin-section computed tomography (CT) of the lungs. It consists of scattered or diffuse ground-glass attenuation with superimposed interlobular septal thickening and intralobular lines. This finding has a variety of causes, including infectious, neoplastic, idiopathic, inhalational, and sanguineous disorders. Specific disorders that can cause the crazy-paving pattern include Pneumocystis carinii pneumonia, mucinous bronchioloalveolar carcinoma, pulmonary alveolar proteinosis, sarcoidosis, nonspecific interstitial pneumonia, organizing pneumonia, exogenous lipoid pneumonia, adult respiratory distress syndrome, and pulmonary hemorrhage syndromes. Knowledge of the many causes of this pattern can be useful in preventing diagnostic errors. In addition, although the causes of this pattern are frequently indistinguishable at radiologic evaluation, differences in the location of the characteristic attenuation in the lungs, as well as the presence of additional radiologic findings, the patient's history, and the clinical presentation, can often be useful in suggesting the appropriate diagnosis.

Bronchiolitis obliterans syndrome in lung transplant recipients: correlation of computed tomography findings with bronchiolitis obliterans syndrome stage.

The purpose of this study was to correlate the extent of computed tomographic (CT) findings with the severity of respiratory dysfunction in lung transplant recipients with bronchiolitis obliterans syndrome (BOS). Eighty-nine conventional and 61 thin-section CT scans performed in 44 transplant recipients (17 bilateral, 27 single) with BOS were reviewed for mosaic attenuation, degree of bronchial dilation, bronchial thickening, central and peripheral bronchiectasis, mucus plugging, and air trapping. Findings on conventional and thin-section CT scans were correlated with BOS stage for bilateral and single-lung transplant recipients. In bilateral-lung recipients, a significant correlation existed, although weak, between BOS stage and findings of degree of bronchial dilation (P < 0.01), bronchial wall thickening (P = 0.01), peripheral bronchiectasis (P = 0.01), and mosaic attenuation (P = 0.01) on conventional CT; and bronchial wall thickening (P = 0.01) and mosaic attenuation (P = 0.03) on thin-section CT. In single-lung recipients, BOS stage correlated only with the finding of central bronchiectasis (P = 0.02) on conventional CT scans. No correlation was found between the extent of air trapping and BOS stage in either single- or bilateral-lung transplant recipients. CT findings are relatively poor indices of airflow obstruction in lung transplant recipients with BOS, particularly in those with single-lung transplants for emphysema.

Drug-induced lung injury.

Lung injury is an increasing cause of morbidity and mortality in patients treated with cytotoxic and noncytotoxic drugs. Prompt diagnosis is important because early drug-induced lung injury will often regress with the cessation of therapy. Diagnosis requires a high index of suspicion because infection, radiation pneumonitis, and recurrence of the underlying disease can manifest clinically and radiologically in a similar manner. Because the lungs have only a limited number of histopathologic responses to injury, including pulmonary edema/diffuse alveolar damage, NSIP, BOOP, EP, and pulmonary hemorrhage, knowledge of these manifestations and the corresponding radiologic manifestations can often be useful in suggesting a diagnosis of drug-induced lung injury. An understanding of the drugs most commonly associated with lung injury can also facilitate diagnosis.

High-resolution CT of drug-induced lung disease.

Drug-induced pulmonary toxicity is increasing and early diagnosis is important because of the associated morbidity and mortality. Diagnosis is often difficult and is usually based on a history of drug therapy and exclusion of infection, radiation pneumonitis, and recurrence of the underlying disease. Although HRCT findings are frequently nonspecific, diagnosis can be facilitated by an understanding of the most common histopathologic and radiologic manifestations of drug-induced lung injury and knowledge of the drugs usually involved.

Linfangiomatosis musculoesquelética / Skeletal lymphangiomatosis

La linfangiomatosis musculoesquéletica ha sido descripta esporádicamente en la bibliografía radiológica y ortopédica. Este caso documenta el espectro imagenológico de una enfermedad poco frecuente y ayuda a identificar un potencial patrón diagnóstico. Se presenta una paciente de 35 años de edad que consulta por dolor dorsolumbar inespecífico, es estudiada mediante Rx simple, Tomografía Computada (TC) y Resonancia Magnética (RM). Los hallazgos radiológicos evidenciados permitieron confirmar la naturaleza benigna de la enfermedad. La linfangiomatosis musculoesquelética es una entidad benigna poco frecuente de etiología desconocida, que compromete a los vasos sanguíneos y linfáticos, produce lesiones quísticas difusas a nivel del esqueleto axial y apendicular y se acompaña de afectación visceral. El empleo de los distintos métodos de imágenes permite realizar el diagnóstico correcto

Linfangiomatosis musculoesquelética / Skeletal lymphangiomatosis

La linfangiomatosis musculoesquéletica ha sido descripta esporádicamente en la bibliografía radiológica y ortopédica. Este caso documenta el espectro imagenológico de una enfermedad poco frecuente y ayuda a identificar un potencial patrón diagnóstico. Se presenta una paciente de 35 años de edad que consulta por dolor dorsolumbar inespecífico, es estudiada mediante Rx simple, Tomografía Computada (TC) y Resonancia Magnética (RM). Los hallazgos radiológicos evidenciados permitieron confirmar la naturaleza benigna de la enfermedad. La linfangiomatosis musculoesquelética es una entidad benigna poco frecuente de etiología desconocida, que compromete a los vasos sanguíneos y linfáticos, produce lesiones quísticas difusas a nivel del esqueleto axial y apendicular y se acompaña de afectación visceral. El empleo de los distintos métodos de imágenes permite realizar el diagnóstico correcto (AU)