Spatial Resolution Fidelity Comparison Between Energy Integrating and Deep Silicon Photon Counting CT: Implications for Pulmonary Imaging.

PURPOSE: We investigated spatial resolution loss away from isocenter for a prototype deep silicon photon-counting detector (PCD) CT scanner and compare with a clinical energy-integrating detector (EID) CT scanner. MATERIALS AND METHODS: We performed three scans on a wire phantom at four positions (isocenter, 6.7, 11.8, and 17.1 cm off isocenter). The acquisition modes were 120 kV EID CT, 120 kV high-definition (HD) EID CT, and 120 kV PCD CT. HD mode used double the projection view angles per rotation as the "regular" EID scan mode. The diameter of the wire was calculated by taking the full width of half max (FWHM) of a profile drawn over the radial and azimuthal directions of the wire. Change in wire diameter appearance was assessed by calculating the ratio of the radial and azimuthal diameter relative to isocenter. t tests were used to make pairwise comparisons of the wire diameter ratio with each acquisition and mean ratios' difference from unity. RESULTS: Deep silicon PCD CT had statistically smaller (P<0.05) changes in diameter ratio for both radial and azimuthal directions compared with both regular and HD EID modes and was not statistically different from unity (P<0.05). Maximum increases in FWMH relative to isocenter were 36%, 12%, and 1% for regular EID, HD EID, and deep silicon PCD, respectively. CONCLUSION: Deep silicon PCD CT exhibits less change in spatial resolution in both the radial and azimuthal directions compared with EID CT.

Update on Interstitial Pneumonias.

The American Thoracic Society/European Respiratory Society/Japanese Respiratory Society/Asociación Latinoamericana de Tórax 2018 clinical practice guideline and 2022 update provide recommendations to define and diagnose idiopathic pulmonary fibrosis (IPF) in patients with newly diagnosed interstitial lung disease. The guideline emphasizes recognition of usual interstitial pneumonia (UIP) and probable UIP patterns of fibrosis on high-resolution CT, which can obviate the need for surgical lung biopsy and allow timely initiation of antifibrotic pharmacotherapy citing a high correlation with UIP on histopathology. This article reviews the recent 2022 IPF clinical practice guideline with a focus on the imaging updates.

Progressive Pulmonary Fibrosis and Interstitial Lung Abnormalities: AJR Expert Panel Narrative Review.

Progressive pulmonary fibrosis (PPF) and interstitial lung abnormalities (ILA) are relatively new concepts in interstitial lung disease (ILD) imaging and clinical management. Recognition of signs of PPF, as well as identification and classification of ILA, are important tasks during chest high-resolution CT interpretation, to optimize management of patients with ILD and those at risk of developing ILD. However, following professional society guidance, the role of imaging surveillance remains unclear in stable patients with ILD, asymptomatic patients with ILA who are at risk of progression, and asymptomatic patients at risk of developing ILD without imaging abnormalities. In this AJR Expert Panel Narrative Review, we summarize the current knowledge regarding PPF and ILA and describe the range of clinical practice with respect to imaging patients with ILD, those with ILA, and those at risk of developing ILD. In addition, we offer suggestions to help guide surveillance imaging in areas with an absence of published guidelines, where such decisions are currently driven primarily by local pulmonologists' preference.

RadioGraphics Update: Lung-RADS 2022.

Editor's Note.-RadioGraphics Update articles supplement or update information found in full-length articles previously published in RadioGraphics. These updates, written by at least one author of the previous article, provide a brief synopsis that emphasizes important new information such as technological advances, revised imaging protocols, new clinical guidelines involving imaging, or updated classification schemes.

One hundred cases of primary spontaneous pneumomediastinum: leukocytosis is common, pleural effusions and age over 40 are rare.

Background: Primary spontaneous pneumomediastinum (PSPM) is a benign condition, but it can be difficult to discriminate from Boerhaave syndrome. The diagnostic difficulty is attributable to a shared constellation of history, signs, and symptoms combined with a poor understanding of the basic vital signs, labs, and diagnostic findings characterizing PSPM. These challenges likely contribute to high resource utilization for diagnosis and management of a benign process. Methods: Patients aged 18 years or older with PSPM were identified from our radiology department's database. A retrospective chart review was performed. Results: Exactly 100 patients with PSPM were identified between March 2001 and November 2019. Demographics and histories correlated well with prior studies: mean age (25 years); male predominance (70%); association with cough (34%), asthma (27%), retching or emesis (24%), tobacco abuse (11%), and physical activity (11%); acute chest pain (75%), and dyspnea (57%) as the first and second most frequent symptoms and subcutaneous emphysema (33%) as the most common sign. We provide the first robust data on presenting vital signs and laboratory values of PSPM, showing that tachycardia (31%) and leukocytosis (30%) were common. No pleural effusion was found in the 66 patients who underwent computed tomography (CT) of the chest. We provide the first data on inter-hospital transfer rates (27%). 79% of transfers were due to concern for esophageal perforation. Most patients were admitted (57%), with an average length of stay (LOS) of 2.3 days, and 25% received antibiotics. Conclusions: PSPM patients frequently present in their twenties with chest pain, subcutaneous emphysema, tachycardia, and leukocytosis. Approximately 25% have a history of retching or emesis and it is this population that must be discriminated from those with Boerhaave syndrome. An esophagram is rarely indicated and observation alone is appropriate in patients under age 40 with a known precipitating event or risk factors for PSPM (e.g., asthma, smoking) if they have no history of retching or emesis. Fever, pleural effusion, and age over 40 are rare in PSPM and should raise concern for esophageal perforation in a patient with a history of retching, emesis, or both.

CT without borders: Comparison of diagnoses for abdominal pain from a teaching hospital in rural Kenya and a US academic medical center.

PURPOSE: Radiology global health opportunities are expanding as more hospitals in low- and middle-income countries utilize CT. This creates opportunities for global health program building, education, service, and research. This study determines the diagnostic yield and variety of abdominopelvic CT diagnoses for abdominal pain in a US academic medical center (UW) compared to a rural Kenyan teaching hospital (Tenwek). METHODS: A retrospective, cross-sectional sequential sample of 750 adults from both hospitals who underwent abdominopelvic CT for abdominal pain from February 2019 through July 2020 was obtained. Exclusion criteria were trauma, cancer staging, and recent hospitalization or surgery. Patient age, sex, comparison studies, use of contrast, known cancer diagnosis, and CT diagnoses were compared. Negative exam rate, acute abdomen diagnosis, and new cancer diagnosis were recorded. Statistical analysis was performed using R. RESULTS: 750 UW patients met inclusion criteria (mean age 53.3 ± 20 years; 442 women) and 750 Tenwek patients met inclusion criteria (mean age 52.5 ± 18 years; 394 women). 72% of UW patients had comparison imaging compared to 6% of Tenwek patients. 11% (83/750) of UW patients had a known cancer diagnosis compared to 1% (10/750) of Tenwek patients. 39% of UW patients had a negative exam compared to 23% of Tenwek patients (p < 0.001). 58% of UW patients had an acute abdomen diagnosis compared to 38% of Tenwek patients (p < 0.001). 10 of the 15 top acute abdomen diagnoses were shared, but in different order of frequency. Diagnoses unique to UW were diverticulitis, constipation, stercoral colitis, and epiploic appendagitis. Diagnoses unique to Tenwek were tuberculosis and hydatidosis. 3% of UW patients received a new cancer diagnosis (7/19 metastatic), compared to 40% of Tenwek patients (153/303 metastatic) (p < 0.001). CONCLUSION: For adults undergoing CT for abdominal pain, there are differences in the prevalence of abdominal pain diagnoses, new cancer diagnosis, and negative exam rate between the rural Kenyan teaching hospital and the US academic medical center.

A Quick Reference Guide for Incidental Findings on Lung Cancer Screening CT Examinations.

PURPOSE: The US Preventive Services Task Force has recommended lung cancer screening (LCS) with low-dose CT (LDCT) in high-risk individuals since 2013. Because LDCT encompasses the lower neck, chest, and upper abdomen, many incidental findings (IFs) are detected. The authors created a quick reference guide to describe common IFs in LCS to assist LCS program navigators and ordering providers in managing the care continuum in LCS. METHODS: The ACR IF white papers were reviewed for findings on LDCT that were age appropriate for LCS. A draft guide was created on the basis of recommendations in the IF white papers, the medical literature, and input from subspecialty content experts. The draft was piloted with LCS program navigators recruited through contacts by the ACR LCS Steering Committee. The navigators completed a survey on overall usefulness, clarity, adequacy of content, and user experience with the guide. RESULTS: Seven anatomic regions including 15 discrete organs with 45 management recommendations were identified as relevant to the age of individuals eligible for LCS. The draft was piloted by 49 LCS program navigators from 32 facilities. The guide was rated as useful and clear by 95% of users. No unexpected or adverse experiences were reported in using the guide. On the basis of feedback, relevant sections were reviewed and edited. CONCLUSIONS: The ACR Lung Cancer Screening CT Incidental Findings Quick Reference Guide outlines the common IFs in LCS and can serve as an easy-to-use resource for ordering providers and LCS program navigators to help guide management.

Long-term Lung Abnormalities Associated with COVID-19 Pneumonia.

In the 3rd year of the SARS-CoV-2 pandemic, much has been learned about the long-term effects of COVID-19 pneumonia on the lungs. Approximately one-third of patients with moderate-to-severe pneumonia, especially those requiring intensive care therapy or mechanical ventilation, have residual abnormalities at chest CT 1 year after presentation. Abnormalities range from parenchymal bands to bronchial dilation to frank fibrosis. Less is known about the long-term pulmonary vascular sequelae, but there appears to be a persistent, increased risk of venothromboembolic events in a small cohort of patients. Finally, the associated histologic abnormalities resulting from SARS-CoV-2 infection are similar to those seen in patients with other causes of acute lung injury.

Imaging of Occupational and Environmental Lung Disease.

The respiratory tract is continuously exposed to and filters toxins from the home and work environments. Certain occupations and environmental exposures can cause unique injuries to the upper and lower respiratory system. Despite increasing federal regulations in the workplace, occupation-associated lung disease is still a major cause of lung disease and disability and continues to evolve with changes in industry, regulation, and new emerging exposures and toxins. Establishing a diagnosis can be difficult, often due to long latency between exposure and clinical disease, insufficient patient history, and nonspecific or varying imaging appearance. Identifying key imaging features of occupational lung disease along with a multidisciplinary approach can aid in accurate and timely diagnosis. In this review, we will discuss the importance of a comprehensive patient history, multidisciplinary approach to diagnosis, and key imaging features of occupation-related lung injuries. Radiographic and computed tomographic findings will be described and illustrated.

North American Endemic Fungal Infections.

Histoplasmosis, blastomycosis, and coccidioidomycosis are endemic fungal infections in North America. Many infections are subclinical, and many symptomatic infections are mild. Pneumonia is the most common clinical manifestation. All can occur in immunocompetent and immunocompromised patients, with the latter at greater risk for disseminated and more severe disease. As with other acute respiratory illness, imaging can play a role in diagnosis. Knowledge of the acute and chronic imaging findings of endemic fungal infections is important for radiologists so that they can assist in establishing these often-elusive diagnoses, recognize normal evolution of imaging findings of infection, and identify complications.

Blastomycosis: The Great Pretender.

Blastomycosis is an endemic fungal infection caused by Blastomyces, a soil-dwelling dimorphic fungus found predominantly in North America. In this pictorial essay, we illustrate the varied imaging features of blastomycosis along with a brief description of the epidemiology, clinical aspects, and differential diagnosis, emphasizing clues that can help radiologists arrive at this diagnosis.

Medication-induced Pulmonary Injury: A Scenario- and Pattern-based Approach to a Perplexing Problem.

Medication-induced pulmonary injury (MIPI) is a complex medical condition that has become increasingly common yet remains stubbornly difficult to diagnose. Diagnosis can be aided by combining knowledge of the most common imaging patterns caused by MIPI with awareness of which medications a patient may be exposed to in specific clinical settings. The authors describe six imaging patterns commonly associated with MIPI: sarcoidosis-like, diffuse ground-glass opacities, organizing pneumonia, centrilobular ground-glass nodules, linear-septal, and fibrotic. Subsequently, the occurrence of these patterns is discussed in the context of five different clinical scenarios and the medications and medication classes typically used in those scenarios. These scenarios and medication classes include the rheumatology or gastrointestinal clinic (disease-modifying antirheumatic agents), cardiology clinic (antiarrhythmics), hematology clinic (cytotoxic agents, tyrosine kinase inhibitors, retinoids), oncology clinic (immune modulators, tyrosine kinase inhibitors, monoclonal antibodies), and inpatient service (antibiotics, blood products). Additionally, the article draws comparisons between the appearance of MIPI and the alternative causes of lung disease typically seen in those clinical scenarios (eg, connective tissue disease-related interstitial lung disease in the rheumatology clinic and hydrostatic pulmonary edema in the cardiology clinic). Familiarity with the most common imaging patterns associated with frequently administered medications can help insert MIPI into the differential diagnosis of acquired lung disease in these scenarios. However, confident diagnosis is often thwarted by absence of specific diagnostic tests for MIPI. Instead, a working diagnosis typically relies on multidisciplinary consensus. ©RSNA, 2021.

ACR Appropriateness Criteria® Chronic Cough.

Chronic cough is defined by a duration lasting at least 8 weeks. The most common causes of chronic cough include smoking-related lung disease, upper airway cough syndrome, asthma, gastroesophageal reflux disease, and nonasthmatic eosinophilic bronchitis. The etiology of chronic cough in some patients may be difficult to localize to an isolated source and is often multifactorial. The complex pathophysiology, clinical presentation, and variable manifestations of chronic cough underscore the challenges faced by clinicians in the evaluation and management of these patients. Imaging plays a role in the initial evaluation, although there is a lack of high-quality evidence guiding which modalities are useful and at what point in time the clinical evaluation should be performed. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

ACR Appropriateness Criteria® Diffuse Lung Disease.

Diffuse lung disease, frequently referred to as interstitial lung disease, encompasses numerous disorders affecting the lung parenchyma. The potential etiologies of diffuse lung disease are broad with several hundred established clinical syndromes and pathologies currently identified. Imaging plays a critical role in diagnosis and follow-up of many of these diseases, although multidisciplinary discussion is the current standard for diagnosis of several DLDs. This document aims to establish guidelines for evaluation of diffuse lung diseases for 1) initial imaging of suspected diffuse lung disease, 2) initial imaging of suspected acute exacerbation or acute deterioration in cases of confirmed diffuse lung disease, and 3) clinically indicated routine follow-up of confirmed diffuse lung disease without acute deterioration. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

ACR Appropriateness Criteria® Nontraumatic Chest Wall Pain.

Chest pain is a common reason that patients may present for evaluation in both ambulatory and emergency department settings, and is often of musculoskeletal origin in the former. Chest wall syndrome collectively describes the various entities that can contribute to chest wall pain of musculoskeletal origin and may affect any chest wall structure. Various imaging modalities may be employed for the diagnosis of nontraumatic chest wall conditions, each with variable utility depending on the clinical scenario. We review the evidence for or against use of various imaging modalities for the diagnosis of nontraumatic chest wall pain. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.