Pulmonary Infection.

Pneumonia is a significant cause of morbidity and mortality in the community and hospital settings. Bacterial, viral, mycobacterial, and fungal pathogens are all potential causative agents of pulmonary infection. Chest radiographs and computed tomography are frequently utilized in the assessment of pneumonia. Learning the imaging patterns of different potential organisms allows the radiologist to formulate an appropriate differential diagnosis. An organism-based approach is used to discuss the imaging findings of different etiologies of pulmonary infection.

Viral Pneumonias.

Viral pneumonia is usually community acquired and caused by influenza, parainfluenza, respiratory syncytial virus, human metapneumovirus, and adenovirus. Many of these infections are airway centric and chest imaging demonstrates bronchiolitis and bronchopneumonia, With the exception of adenovirus infections, the presence of lobar consolidation usually suggests bacterial coinfection. Community-acquired viral pathogens can cause more severe pneumonia in immunocompromised hosts, who are also susceptible to CMV and varicella infection. These latter 2 pathogens are less likely to manifest the striking airway-centric pattern. Airway-centric pattern is distinctly uncommon in Hantavirus pulmonary syndrome, a rare environmentally acquired infection with high mortality.

Myocarditis Presenting as ST-Elevation Myocardial Infarction.

When evaluating a patient with ST-segment elevation on ECG and acute chest pain, providers often rapidly arrive at the diagnosis of ST-elevation myocardial infarction (STEMI). As myocardial infarction is deadly and time is of the essence in establishing reperfusion, it is reasonable to place it at the top of the differential. However, doing so should not come at the expense of conducting a thorough clinical evaluation, considering all causes of ST-segment elevation, and creating a comprehensive differential. Myocarditis, in particular, can present similarly to myocardial infarction and misdiagnosis can lead to unnecessary and sometimes harmful interventions such as thrombolytic therapy, vasodilator therapy, or coronary angiography. We present a case of myocarditis mimicking STEMI and discuss diagnosis and treatment of myocarditis.

Mitral Annular Disjunction: Review of an Increasingly Recognized Mitral Valve Entity.

Mitral annular disjunction (MAD) refers to atrial displacement of the hinge point of the mitral valve annulus from the ventricular myocardium. MAD leads to paradoxical expansion of the annulus in systole and may often be associated with mitral valve prolapse (MVP), leaflet degeneration, myocardial and papillary muscle fibrosis, and, potentially, malignant cardiac arrhythmias. Patients with MAD and MVP may present similarly, and MAD is potentially the missing link in explaining why some patients with MVP experience adverse outcomes. Patients with a 5 mm or longer MAD distance have an elevated risk of malignant cardiac arrhythmia compared with those with a shorter MAD distance. Evaluation for MAD is an important component of cardiac imaging, especially in patients with MVP and unexplained cardiac arrhythmias. Cardiac MRI is an important diagnostic tool that aids in recognizing and quantifying MAD, MVP, and fibrosis in the papillary muscle and myocardium, which may predict and help improve outcomes following electrophysiology procedures and mitral valve surgery. This article reviews the history, pathophysiology, controversy, prevalence, clinical implications, and imaging considerations of MAD, focusing on cardiac MRI. Keywords: MR-Dynamic Contrast Enhanced, Cardiac, Mitral Valve, Mitral Annular Disjunction, Mitral Valve Prolapse, Floppy Mitral Valve, Cardiac MRI, Arrhythmia, Sudden Cardiac Death, Barlow Valve © RSNA, 2023.

Community-Acquired Pneumonia: Postpandemic, Not Post-COVID-19.

The coronavirus disease 2019 (COVID-19) pandemic upended our approach to imaging community-acquired pneumonia, and this will alter our diagnostic algorithms for years to come. In light of these changes, it is worthwhile to consider several postpandemic scenarios of community-acquired pneumonia: (1) patient with pneumonia and recent positive COVID-19 testing; (2) patient with air space opacities and history of prior COVID-19 pneumonia (weeks earlier); (3) multifocal pneumonia with negative or unknown COVID-19 status; and (4) lobar or sublobar pneumonia with negative or unknown COVID-19 status. In the setting of positive COVID-19 testing and typical radiologic findings, the diagnosis of COVID-19 pneumonia is generally secure. The diagnosis prompts vigilance for thromboembolic disease acutely and, in severely ill patients, for invasive fungal disease. Persistent or recurrent air space opacities following COVID-19 infection may more often represent organizing pneumonia than secondary infection. When COVID-19 status is unknown or negative, widespread airway-centric disease suggests infection with mycoplasma, Haemophilus influenzae, or several respiratory viruses. Necrotizing pneumonia favors infection with pneumococcus, Staphylococcus, Klebsiella, and anaerobes. Lobar or sublobar pneumonia will continue to suggest the diagnosis of pneumococcus or consideration of other pathogens in the setting of local outbreaks. A positive COVID-19 test accompanied by these imaging patterns may suggest coinfection with one of the above pathogens, or when the prevalence of COVID-19 is very low, a false positive COVID-19 test. Clinicians may still proceed with testing for COVID-19 when radiologic patterns are atypical for COVID-19, dependent on the patient's exposure history and the local epidemiology of the virus.

Pitfalls and pearls in the imaging of cardiac ischemia.

Coronary artery disease is the most common cause of cardiac ischemia and a leading cause of death globally. There are multiple imaging modalities which can assess cardiac ischemia, in particular coronary CT calcium score, coronary CT angiography, and cardiac MRI. Each of these modalities offers insight into the overall patient picture. However, coronary CT and cardiac MRI are not free from limitations. This article will review the roles of CT and MRI in cardiac imaging, mimics, technical limitations, and potential pitfalls that may be encountered.

Viral Pneumonias.

Viral pneumonia is usually community acquired and caused by influenza, parainfluenza, respiratory syncytial virus, human metapneumovirus, and adenovirus. Many of these infections are airway centric and chest imaging demonstrates bronchiolitis and bronchopneumonia, With the exception of adenovirus infections, the presence of lobar consolidation usually suggests bacterial coinfection. Community-acquired viral pathogens can cause more severe pneumonia in immunocompromised hosts, who are also susceptible to CMV and varicella infection. These latter 2 pathogens are less likely to manifest the striking airway-centric pattern. Airway-centric pattern is distinctly uncommon in Hantavirus pulmonary syndrome, a rare environmentally acquired infection with high mortality.

Pneumonia in the Immunocompromised Host.

Pneumonia in the immunocompromised host can be devastating and can result from both common and opportunistic organisms. This paper examines the imaging findings in mostly opportunistic organisms which cause pneumonia in the immunocompromised host. Some organisms, such as tuberculosis, non-tuberculous mycobacteria, and influenza will also be discussed because although they are not specifically opportunistic, they can result in extensive and devastating disease in immunocompromised patients. It is important for the radiologist to recognize unique imaging findings in pneumonia in the immunocompromised patient and raise the possibility of certain organisms to direct appropriate therapy.

The role of CT in planning percutaneous structural heart interventions: Where to measure and why.

As research continues to demonstrate successes in the use of percutaneous trans-vascular techniques in structural heart intervention, both the subspecialty trained and non-subspecialty trained cardiac imager find themselves performing and reporting larger amounts of information regarding cardiovascular findings. It is therefore imperative that the imager gains understanding and appreciation for how these various measurements are obtained, as well as their implication in a patient's care. Cardiac gated computed tomography (CT) has solidified its role and ability at providing high resolution images that can be used to obtain the key measurements used in structural heart intervention planning. This manuscript aims to provide an overview of what measurements are necessary to report when interpreting CT examinations purposed for structural heart intervention. This includes a review on indications and brief discussion on complications related to these procedures.

Comparison of Chest CT Findings of COVID-19, Influenza, and Organizing Pneumonia: A Multireader Study.

BACKGROUND. Previous studies compared CT findings of COVID-19 pneumonia with those of other infections; however, to our knowledge, no studies to date have included noninfectious organizing pneumonia (OP) for comparison. OBJECTIVE. The objectives of this study were to compare chest CT features of COVID-19, influenza, and OP using a multireader design and to assess the performance of radiologists in distinguishing between these conditions. METHODS. This retrospective study included 150 chest CT examinations in 150 patients (mean [± SD] age, 58 ± 16 years) with a diagnosis of COVID-19, influenza, or non-infectious OP (50 randomly selected abnormal CT examinations per diagnosis). Six thoracic radiologists independently assessed CT examinations for 14 individual CT findings and for Radiological Society of North America (RSNA) COVID-19 category and recorded a favored diagnosis. The CT characteristics of the three diagnoses were compared using random-effects models; the diagnostic performance of the readers was assessed. RESULTS. COVID-19 pneumonia was significantly different (p < .05) from influenza pneumonia for seven of 14 chest CT findings, although it was different (p < .05) from OP for four of 14 findings (central or diffuse distribution was seen in 10% and 7% of COVID-19 cases, respectively, vs 20% and 21% of OP cases, respectively; unilateral distribution was seen in 1% of COVID-19 cases vs 7% of OP cases; non-tree-in-bud nodules was seen in 32% of COVID-19 cases vs 53% of OP cases; tree-in-bud nodules were seen in 6% of COVID-19 cases vs 14% of OP cases). A total of 70% of cases of COVID-19, 33% of influenza cases, and 47% of OP cases had typical findings according to RSNA COVID-19 category assessment (p < .001). The mean percentage of correct favored diagnoses compared with actual diagnoses was 44% for COVID-19, 29% for influenza, and 39% for OP. The mean diagnostic accuracy of favored diagnoses was 70% for COVID-19 pneumonia and 68% for both influenza and OP. CONCLUSION. CT findings of COVID-19 substantially overlap with those of influenza and, to a greater extent, those of OP. The diagnostic accuracy of the radiologists was low in a study sample that contained equal proportions of these three types of pneumonia. CLINICAL IMPACT. Recognized challenges in diagnosing COVID-19 by CT are furthered by the strong overlap observed between the appearances of COVID-19 and OP on CT. This challenge may be particularly evident in clinical settings in which there are substantial proportions of patients with potential causes of OP such as ongoing cancer therapy or autoimmune conditions.

Case 287: Intrathoracic Migration of a Breast Implant after Video-assisted Thoracoscopic Surgery for Right Upper Lobectomy.

History A 60-year-old woman was diagnosed with a new right upper lobe stage I lung adenocarcinoma and underwent video-assisted thoracoscopic surgery (VATS) for right upper lobectomy. Her postoperative course was complicated by a large pneumothorax after chest tube removal on postoperative day 3. This was managed with repeat right-sided chest tube placement on the same day. The second chest tube was removed on postoperative day 8 without complications. A 2-week postoperative clinic visit was unremarkable. Postoperative chest radiographs on postoperative days 1, 3, and 8 are provided. Subsequently, chest CT scanning was performed as part of routine 6-month postsurgical lung cancer surveillance follow-up. The patient had no clinical complaints at routine follow-up. Physical examination revealed well-healed VATS scars in the chest wall. Laboratory results were within normal limits, including a normal white blood cell count of 6400/mL. Her surgical history included prior left upper lobectomy for remote left upper lobe stage IIIA adenocarcinoma and prior bilateral breast implantation for cosmesis. On the basis of chest CT findings, the patient was transferred from an outside institution.

Comparison of Baseline, Bone-Subtracted, and Enhanced Chest Radiographs for Detection of Pneumothorax.

PURPOSE: To assess and compare detectability of pneumothorax on unprocessed baseline, single-energy, bone-subtracted, and enhanced frontal chest radiographs (chest X-ray, CXR). METHOD AND MATERIALS: Our retrospective institutional review board-approved study included 202 patients (mean age 53 ± 24 years; 132 men, 70 women) who underwent frontal CXR and had trace, moderate, large, or tension pneumothorax. All patients (except those with tension pneumothorax) had concurrent chest computed tomography (CT). Two radiologists reviewed the CXR and chest CT for pneumothorax on baseline CXR (ground truth). All baseline CXR were processed to generate bone-subtracted and enhanced images (ClearRead X-ray). Four radiologists (R1-R4) assessed the baseline, bone-subtracted, and enhanced images and recorded the presence of pneumothorax (side, size, and confidence for detection) for each image type. Area under the curve (AUC) was calculated with receiver operating characteristic analyses to determine the accuracy of pneumothorax detection. RESULTS: Bone-subtracted images (AUC: 0.89-0.97) had the lowest accuracy for detection of pneumothorax compared to the baseline (AUC: 0.94-0.97) and enhanced (AUC: 0.96-0.99) radiographs (P < .01). Most false-positive and false-negative pneumothoraces were detected on the bone-subtracted images and the least numbers on the enhanced radiographs. Highest detection rates and confidence were noted for the enhanced images (empiric AUC for R1-R4 0.96-0.99). CONCLUSION: Enhanced CXRs are superior to bone-subtracted and unprocessed radiographs for detection of pneumothorax. CLINICAL RELEVANCE/APPLICATION: Enhanced CXRs improve detection of pneumothorax over unprocessed images; bone-subtracted images must be cautiously reviewed to avoid false negatives.

Imaging Adult ECMO.

Adult extracorporal membrane oxygenation utilization in the ICU has rapidly increased. Newer technology and cannulation strategies and the complex hemodynamics make imaging interpretation challenging. There is also a high rate of complications. This review details the common indications, cannulation strategies, relevant hemodynamics and complications which impact imaging interpretation. Recommendations for modifying computed tomography protocols and techniques to obtain diagnostic images and some of the imaging pitfalls are also discussed.

Case 287.

History A 60-year-old woman was diagnosed with a new right upper lobe stage I lung adenocarcinoma and underwent video-assisted thoracoscopic surgery (VATS) for right upper lobectomy. Her postoperative course was complicated by a large pneumothorax after chest tube removal on postoperative day 3. This was managed with repeat right-sided chest tube placement on the same day. The second chest tube was removed on postoperative day 8 without complications. A 2-week postoperative clinic visit was unremarkable. Postoperative chest radiographs on postoperative days 1, 3, and 8 (Fig 1a-1c) are provided. Subsequently, chest CT scanning was performed as part of routine 6-month postsurgical lung cancer surveillance follow-up (Figs 2, 3). The patient had no clinical complaints at routine follow-up. Physical examination revealed well-healed VATS scars in the chest wall. Laboratory results were within normal limits, including a normal white blood cell count of 6400/µL. Her surgical history included prior left upper lobectomy for remote left upper lobe stage IIIA adenocarcinoma and prior bilateral breast implantation for cosmesis. On the basis of chest CT findings, the patient was transferred from an outside institution.

Simultaneous pulmonary artery and Stanford type B aortic dissections via the ductus arteriosus.

Pulmonary artery dissection is an exceedingly rare and highly lethal diagnosis that can result in arterial rupture; hence, it is most often identified postmortem. Moreover, pulmonary artery complications resulting from aortic dissection are uncommon occurrences that have seemingly only been reported in cases of Stanford type A aortic dissections. Due to the rarity of pulmonary artery dissections, there is no current established algorithm for treatment of these patients, unlike aortic dissections. We herein present a case of a 40-year-old male with history of uncontrolled hypertension who developed acute back and leg pain that was subsequently diagnosed with a Stanford type B aortic dissection that extended into the main pulmonary artery by way of the ductus arteriosus. Although the patient received appropriate care for his aortic dissection and hypertensive emergency, he eventually died due to development of extensive additional vascular insults: cerebrovascular accidents, compartment syndrome, and myocardial infarction. To our knowledge, this is the first case of combined pulmonary artery dissection and Stanford type B dissection in the literature, which unfortunately adds to the understanding that cases of pulmonary artery dissection tend to have a grim prognosis.

Analysis of Out-of-Pocket Cost of Lung Cancer Screening for Uninsured Patients Among ACR-Accredited Imaging Centers.

PURPOSE: To determine the variability in out-of-pocket costs of lung cancer screening (LCS) for uninsured patients and assess accessibility of this information by telephone or Internet. METHODS: LCS centers from the ACR's LCS database were randomly selected. Centers were called between July and August 2019 to determine out-of-pocket cost. Telephone call variables, accessibility of cost information on screening centers' websites, screening centers' chargemasters, and publicly available facility and state insurance coverage variables were obtained. Cost information was summarized using descriptive analyses. Multiple variable linear regression analyses were conducted to evaluate effects of facility and state-level characteristics on out-of-pocket costs. RESULTS: Fifty-five ACR-accredited LCS centers were included with 78% (43 of 55) willing to provide out-of-pocket cost. Average out-of-pocket cost was $583 ± $607 (mean ± standard deviation), range $49 to $2,409. Average telephone call length 6 ± 3.8 min. Two of fifty-five screening centers' websites provided out-of-pocket cost information, and one matched cost given over the telephone. A chargemaster was found for 30 of 55 screening centers. No statistically significant differences in out-of-pocket costs were found by geographic region, state percentages of uninsured residents, state percentages of residents with public insurance, or facility safety net hospital affiliation. DISCUSSION: Out-of-pocket LCS costs for uninsured patients and availability of this information is highly variable. Radiology practices should be aware of this variability that may influence participation rates among uninsured patients.

Stereotactic Body Radiation Therapy for Early-Stage Non-Small Cell Lung Cancer: A Primer for Radiologists.

The past 2 decades have seen a rapid growth in use of stereotactic body radiation therapy (SBRT) for the management of non-small cell lung cancer (NSCLC). Not only is SBRT the reference standard for treatment of early-stage node-negative NSCLC in medically inoperable patients, it is also currently challenging the role of surgery for early-stage operable disease. SBRT is also used to treat recurrent disease and has a role in the management of multiple synchronous lung cancers. Imaging changes after SBRT differ from the changes after conventional radiation therapy in many ways, the knowledge of which is pertinent for accurate image interpretation. Posttreatment response assessment and detection of recurrent disease are heavily reliant on radiologic assessment, and often the decision to treat recurrent disease is based on the imaging findings themselves. This article provides a comprehensive review of the concepts of SBRT and the current indications for its use in the treatment of early-stage NSCLC, as well as a discussion of the CT findings seen after SBRT compared with the changes after conventional radiation therapy. Radiologic findings that are suggestive of recurrent disease and the imaging pitfalls are also highlighted. Finally, the rare complications after SBRT are described. SBRT is a major component of the changing treatment paradigms for early- and late-stage NSCLC. The imaging findings after SBRT often determine the next steps in a patient's clinical management. Therefore, radiologists must be familiar with the uses of this therapy and its radiologic appearance to be able to effectively contribute to the care of patients with NSCLC. ©RSNA, 2018.