Added Value of Magnetic Resonance Over Computed Tomography in Distinguishing Nonneoplastic Complex Thymic Cysts From Malignant Cystic Thymic Neoplasms.

PURPOSE: The aim of the study was to evaluate cystic thymic masses by using computed tomography (CT) and magnetic resonance (MR) scoring systems to differentiate nonneoplastic thymic cysts from cystic thymic neoplasms. METHODS: This retrospective multisite study included adult patients who underwent CT and MR imaging of the chest between 2007 and 2020 with any of the following impressions on cross-sectional imaging studies: "thymic mass with cystic component," "unilocular or multilocular cystic thymic lesion," "complex thymic cyst," "thymic cyst with hemorrhage." Two blinded radiologists reviewed and recorded specific imaging features as well as overall impressions on both CT and MR using a Likert scale scoring system. Data were analyzed, and diagnostic accuracy of CT and MR was compared using areas under the receiver operating characteristic curves (AUC). RESULTS: Fifty-six patients were included, of which 45 (80%) had benign masses. Total of 21 patients (38%) had indeterminate scores on CT of which 3 (14%) were malignant, while only 6 (11%) had indeterminate scores on MR and 1 was malignant. Magnetic resonance scoring system (AUC, 0.95) performed better than CT scoring system (AUC, 0.86) in distinguishing benign versus malignant lesions (P = 0.06). Lack of enhancement within the mass was completely predictive of benign etiology (P < 0.001). Wall thickness of an enhancing cyst was predictive of malignancy, with AUC 0.93. CONCLUSIONS: Magnetic resonance yielded higher specificity allowing a larger number of lesions to be confidently assigned a benign diagnosis. This could help in averting unnecessary follow-up, biopsies, or surgery. The authors recommend follow-up imaging with MR for prevascular masses, even those appearing "solid" on CT.

A pictorial review of lung torsion using 3D CT cinematic rendering.

Lung torsion is the abnormal rotation of a lobe or lung around its bronchovascular pedicle. It most commonly occurs in the setting of pulmonary resection, though it has also been described after large-volume thoracentesis and video-assisted thoracic surgery, as well as spontaneously. Resulting ischemia can lead to infarction, making this an emergent diagnosis. As findings are often nonspecific, a high index of suspicion is required, especially in the postsurgical setting. 2D CT angiography findings are subtle and include direct signs of pedicle rotation on CT as well as indirect findings including loss of normal parenchymal enhancement, atelectasis of torsed lobe/lung, and abnormal fissure position. These direct and indirect findings are often appreciated on different window presets and upon review of images in multiple planes, with need to collate the information subsequently. 3D cinematic rendering (CR) using multi-planar light sources can readily highlight spatial relationships of vasculature in the chest and may be able to assist in the confident diagnosis of this sometimes subtle but life-threatening pathology. We have provided the first characterization of common lung torsion findings on 3D CR.

Image Quality and Lesion Detection on Deep Learning Reconstruction and Iterative Reconstruction of Submillisievert Chest and Abdominal CT.

OBJECTIVE. The objective of this study was to compare image quality and clinically significant lesion detection on deep learning reconstruction (DLR) and iterative reconstruction (IR) images of submillisievert chest and abdominopelvic CT. MATERIALS AND METHODS. Our prospective multiinstitutional study included 59 adult patients (33 women, 26 men; mean age ± SD, 65 ± 12 years old; mean body mass index [weight in kilograms divided by the square of height in meters] = 27 ± 5) who underwent routine chest (n = 22; 16 women, six men) and abdominopelvic (n = 37; 17 women, 20 men) CT on a 640-MDCT scanner (Aquilion ONE, Canon Medical Systems). All patients gave written informed consent for the acquisition of low-dose (LD) CT (LDCT) after a clinically indicated standard-dose (SD) CT (SDCT). The SDCT series (120 kVp, 164-644 mA) were reconstructed with interactive reconstruction (IR) (adaptive iterative dose reduction [AIDR] 3D, Canon Medical Systems), and the LDCT (100 kVp, 120 kVp; 30-50 mA) were reconstructed with filtered back-projection (FBP), IR (AIDR 3D and forward-projected model-based iterative reconstruction solution [FIRST], Canon Medical Systems), and deep learning reconstruction (DLR) (Advanced Intelligent Clear-IQ Engine [AiCE], Canon Medical Systems). Four subspecialty-trained radiologists first read all LD image sets and then compared them side-by-side with SD AIDR 3D images in an independent, randomized, and blinded fashion. Subspecialty radiologists assessed image quality of LDCT images on a 3-point scale (1 = unacceptable, 2 = suboptimal, 3 = optimal). Descriptive statistics were obtained, and the Wilcoxon sign rank test was performed. RESULTS. Mean volume CT dose index and dose-length product for LDCT (2.1 ± 0.8 mGy, 49 ± 13mGy·cm) were lower than those for SDCT (13 ± 4.4 mGy, 567 ± 249 mGy·cm) (p < 0.0001). All 31 clinically significant abdominal lesions were seen on SD AIDR 3D and LD DLR images. Twenty-five, 18, and seven lesions were detected on LD AIDR 3D, LD FIRST, and LD FBP images, respectively. All 39 pulmonary nodules detected on SD AIDR 3D images were also noted on LD DLR images. LD DLR images were deemed acceptable for interpretation in 97% (35/37) of abdominal and 95-100% (21-22/22) of chest LDCT studies (p = 0.2-0.99). The LD FIRST, LD AIDR 3D, and LD FBP images had inferior image quality compared with SD AIDR 3D images (p < 0.0001). CONCLUSION. At submillisievert chest and abdominopelvic CT doses, DLR enables image quality and lesion detection superior to commercial IR and FBP images.

Significance of the Reverse Halo Sign in Immunocompromised Patients.

OBJECTIVE. The purpose of this study is to assess the most common causes of the reverse halo sign (RHS) in immunocompromised patients and to identify clinicoradiologic features that help in achieving a specific diagnosis. MATERIALS AND METHODS. This retrospective study included 70 patients with hematologic malignancy, neutropenia, or history of solid organ transplant or stem cell transplant who had the RHS at chest CT. Absolute neutrophil count, imaging features of the RHS, and presence of pleural effusions were noted and correlated with the specific diagnosis. A decision tree was constructed from predictive imaging features and compared with radiologist assessment for infectious versus noninfectious cause. RESULTS. Infection, including fungal and bacterial pneumonia, was the most common cause of the RHS (66%), followed by organizing pneumonia (26%). Noninfectious causes such as organizing pneumonia were more likely in the solid organ transplant group, whereas infections were more likely in patients with hematologic malignancy and stem cell transplant. Among fungal pneumonias, aspergillosis (20%) was as common as mucormycosis (19%). In univariate analysis, neutropenia, rim thickness, central ground-glass attenuation, and lesion diameter correlated with infectious cause. A decision tree using neutropenia, rim thickness, central ground-glass attenuation, and pleural effusion could differentiate infectious from noninfectious cause with accuracy of 78%, compared with radiologist accuracy of 81%. CONCLUSION. Infections are more likely to cause RHS than noninfectious processes in immunocompromised patients, and aspergillosis may be as likely overall as mucormycosis because of its higher frequency in these patients. A decision tree using clinical and imaging features can help differentiate infectious from noninfectious causes of RHS.

Predictive Features for Anterior Mediastinal Mass Diagnoses.

OBJECTIVE: We set out to evaluate a set of demographic and computed tomography imaging features for diagnosing anterior mediastinal masses. METHODS: We identified 223 patients with anterior mediastinal masses, which we divided into training and validation sets. One radiologist evaluated computed tomography imaging features on the training set. Then, predictive features were identified, and 3 radiologists evaluated these on the validation set. A naive Bayesian classifier based on the features was compared with the radiologists' first-choice diagnosis. RESULTS: Internal mammary lymphadenopathy and mediastinal encasement were strongly associated with lymphomas. Low attenuation and midline location were strongly associated with benign lesions, and older age was associated with thymic epithelial neoplasms. The average accuracy of the 3 radiologists' diagnoses was 78%, compared with 71% for the classifier. CONCLUSIONS: Nine demographic and imaging features were found to be helpful in diagnosing anterior mediastinal masses. By using these features, radiologists can suggest the diagnosis with fair accuracy.

Pulmonary Mucormycosis: Radiologic Features at Presentation and Over Time.

OBJECTIVE: Pulmonary mucormycosis is an aggressive opportunistic fungal infection. We set out to evaluate the CT and MRI features of pulmonary mucormycosis. MATERIALS AND METHODS: Through a search of the electronic medical record from 2007 to 2017, we identified 30 patients with definite or probable mucormycosis. Two radiologists reviewed the initial chest CT examinations for the presence of features including the "reverse halo" sign, large ground-glass halo, and peripheral lesion distribution. Additional CT and MRI studies were reviewed to evaluate evolution over time. RESULTS: The majority (67%) of patients had lesions with the reverse halo sign at some point in the disease course. A ground-glass halo larger than the lesion was seen in 53% of patients. Notably, lesions had a peripheral predominance in 87% of cases. Through careful review of images, a perivascular ground-glass precursor lesion was identified in 20% of patients 1-2 weeks before a consolidation developed. In five (17%) patients, CT showed a multifocal pneumonia appearance. Finally, MRI of two patients showed T2-hypointense rims and central nonenhancement, a finding we refer to as the "black hole" sign. CONCLUSION: Large nodules or consolidations with an associated reverse halo sign or large perilesional ground-glass halos are common in mucormycosis. Lesions tend to show a peripheral predominance, and a perivascular ground-glass focus preceded nodular lesions in some cases. In some patients with severe disease, imaging features evolved to show a multifocal pneumonia pattern, and this pattern was associated with a high mortality rate.

Motion Artifact Reduction From High-Pitch Dual-Source Computed Tomography Pulmonary Angiography.

PURPOSE: The purpose of this study was to compare quantitative and qualitative measures of aortic, cardiac, and respiratory motion artifact between high-pitch dual-source (DS) and single-source (SS) computed tomography pulmonary angiography (CTPA) protocols. METHODS: This institutional review board-approved, Health Insurance Portability and Accountability Act-compliant study retrospectively reviewed 80 non-electrocardiogram-gated CTPA examinations acquired with a second-generation DS system at 100 kVp following 50 mL iodinated contrast injection - 40 consecutive SS and 40 consecutive DS studies. Quantitative measures of aortic, left ventricular, and diaphragmatic motion were recorded as the maximal excursion of a structure's "double image," and 3 independent readers performed qualitative motion assessments. Pulmonary arterial contrast enhancement, image noise, and radiation dose metrics were recorded. Statistical analyses were performed with 1-way analysis of variance and Fisher exact test. RESULTS: Dual source outperformed SS technique in both quantitative and qualitative measures of motion. Mean distances between motion-artifact double images were reduced with DS protocol at each location (all P ≤ 0.004), and DS examinations were more likely to receive an assessment of no motion in all locations (all P < 0.0001). The DS protocol demonstrated increases in contrast enhancement, although increased image noise resulted in lower enhancement to noise ratio. Mean radiation dose was 60% lower using the DS protocol. CONCLUSION: High-pitch DS CTPA significantly reduces artifacts resulting from ascending aortic, cardiac, and diaphragmatic motion.

Clinical and imaging features in lung torsion and description of a novel imaging sign.

PURPOSE: We set out to identify the clinical and imaging features seen in lung torsion, a rare but emergent diagnosis leading to vascular compromise of a lobe or entire lung. METHODS: We retrospectively identified 10 patients with torsion who underwent chest CT. We evaluated each case for the presence of bronchial obstruction and abnormal fissure orientation. In seven patients who underwent contrast-enhanced CTs, we assessed for the presence of the antler sign, a novel sign seen on axial images demonstrating abnormal curvature of the artery and branches originating on one side. RESULTS: Five patients had right middle lobe (RML) torsion after right upper lobectomy, and the remaining occurred following thoracentesis, aortic surgery, or spontaneously. Chest CTs demonstrated bronchial obstruction in eight cases and presence of abnormal fissure orientation in four patients. The antler sign was present in three patients with whole-lung torsion and one patient with lobar torsion; vascular swirling was seen on 3-D images in all seven patients with contrast-enhanced CTs. CONCLUSIONS: Lung parenchymal imaging findings in lung torsion may be non-specific. Identification of the antler sign on contrast-enhanced chest CT, in combination with other signs such as bronchial obstruction and abnormal fissure orientation, indicates rotation of the bronchovascular pedicle. The presence of this sign should prompt further evaluation with 3-dimensional reconstructions.

A new diagnosis of Williams-Beuren syndrome in a 49-year-old man with severe bullous emphysema.

Williams-Beuren syndrome (WBS) is a chromosomal microdeletion syndrome typically presenting with intellectual disability, a unique personality, a characteristic facial appearance, and cardiovascular disease. Several clinical features of WBS are thought to be due to haploinsufficiency of elastin (ELN), as the ELN locus is included within the WBS critical region at 7q11.23. Emphysema, a disease attributed to destruction of pulmonary elastic fibers, has been reported in patients without WBS who have pathogenic variants in ELN but only once (in one patient) in WBS. Here we report a second adult WBS patient with emphysema where the diagnosis of WBS was established subsequent to the discovery of severe bullous emphysema. Haploinsufficiency of ELN likely contributed to this pulmonary manifestation of WBS. This case emphasizes the contribution of rare genetic variation in cases of severe emphysema and provides further evidence that emphysema should be considered in patients with WBS who have respiratory symptoms, as it may be under-recognized in this patient population.

ITMIG Classification of Mediastinal Compartments and Multidisciplinary Approach to Mediastinal Masses.

Division of the mediastinum into specific compartments is beneficial for a number of reasons, including generation of a focused differential diagnosis for mediastinal masses identified on imaging examinations, assistance in planning for biopsies and surgical procedures, and facilitation of communication between clinicians in a multidisciplinary setting. Several classification schemes for the mediastinum have been created and used to varying degrees in clinical practice. Most radiology classifications have been based on arbitrary landmarks outlined on the lateral chest radiograph. A new scheme based on cross-sectional imaging, principally multidetector computed tomography (CT), has been developed by the International Thymic Malignancy Interest Group (ITMIG) and accepted as a new standard. This clinical division scheme defines unique prevascular, visceral, and paravertebral compartments based on boundaries delineated by specific anatomic structures at multidetector CT. This new definition plays an important role in identification and characterization of mediastinal abnormalities, which, although uncommon and encompassing a wide variety of entities, can often be diagnosed with confidence based on location and imaging features alone. In other scenarios, a diagnosis may be suggested when radiologic features are combined with specific clinical information. In this article, the authors present the new multidetector CT-based classification of mediastinal compartments introduced by ITMIG and a structured approach to imaging evaluation of mediastinal abnormalities. ©RSNA, 2017.

IASLC/ITMIG Staging System and Lymph Node Map for Thymic Epithelial Neoplasms.

Thymic epithelial neoplasms are rare malignancies that arise from the thymus and include thymoma, thymic carcinoma, and thymic neuroendocrine tumors. At least 15 different stage classifications have been proposed for thymic epithelial neoplasms and used to varying degrees in clinical practice, many of which have been constructed from small groups of patients. Traditionally, the Masaoka and Masaoka-Koga staging systems have been the schemes most commonly employed, and the latter has been recommended for use by the International Thymic Malignancy Interest Group (ITMIG). An official, consistent stage classification system has recently been recognized by the American Joint Committee on Cancer (AJCC) and the Union for International Cancer Control (UICC), which are responsible for defining stage classifications for neoplasms. To establish this stage classification system, the International Association for the Study of Lung Cancer (IASLC) and ITMIG amassed a large retrospective database and evaluated this group of cases to develop proposals for the eighth edition of the stage classification manuals. For this endeavor, IASLC provided funding and statistical analysis and ITMIG provided the involvement of the clinicians and researchers actively participating in the study of thymic epithelial neoplasms. To accomplish this, a Thymic Domain of the Staging and Prognostic Factors Committee (TD-SPFC) was established to formulate the rationale, methodology, and definitions of this tumor-node-metastasis (TNM) staging system, which is presented in this article. © RSNA, 2017.

Frequency and Severity of Pulmonary Hemorrhage in Patients Undergoing Percutaneous CT-guided Transthoracic Lung Biopsy: Single-Institution Experience of 1175 Cases.

PURPOSE: To evaluate the frequency and severity of pulmonary hemorrhage after transthoracic needle lung biopsy (TTLB) and assess possible factors associated with pulmonary hemorrhage. MATERIALS AND METHODS: This retrospective study was approved by the institutional review board. The requirement to obtain informed consent was waived. Records from 1113 patients who underwent 1175 TTLBs between January 2008 and April 2013 were retrospectively reviewed. Primary outcomes were pulmonary hemorrhage, documented hemoptysis, and bleeding complications necessitating intervention. Pulmonary hemorrhage was graded as follows: 0, none; 1, less than or equal to 2 cm around the needle; 2, more than 2 cm and sublobar; 3, at least lobar; and 4, hemothorax. Patient, technique, and lesion-related variables were evaluated as predictors of pulmonary hemorrhage. Patient-related variables included main pulmonary artery diameter (mPAD) at computed tomography (CT), pulmonary artery pressures at echocardiography and right-sided heart catheterization, medications, chronic lung disease, bleeding diathesis, and immunodeficiency. Technique- and lesion-related variables included needle gauge, number of passes, pleura-needle angle, lesion size and morphologic characteristics, and distance to pleura. Univariate analysis was performed with χ(2), Fisher exact, and Student t tests. RESULTS: Pulmonary hemorrhage occurred in 483 of the 1175 TTLBs (41.1%); hemoptysis was documented in 21 of the 1175 TTLBs (1.8%). Higher-grade hemorrhage (grade 2 or higher) occurred in 201 of the 1175 TTLBs (17.1%); five of the 1175 TTLBs (0.4%) necessitated hemorrhage-related admission. Higher-grade hemorrhage was more likely to occur with female sex (P = .001), older age (P = .003), emphysema (P = .004), coaxial technique (P = .025), nonsubpleural location (P < .001), lesion size of 3 cm or smaller (P < .001), and subsolid lesions (P = .028). Enlarged mPAD at CT (≥2.95 cm) was not significantly associated with higher-grade hemorrhage (P = .430). CONCLUSION: Pulmonary hemorrhage after TTLB is common but rarely requires intervention. An enlarged mPAD at CT may not be a risk factor for higher-grade hemorrhage.

Demystifying NUT midline carcinoma: radiologic and pathologic correlations of an aggressive malignancy.

OBJECTIVE: NUT midline carcinoma is a rare poorly differentiated aggressive subtype of squamous cell carcinoma. To date, fewer than 100 total cases have been reported. CONCLUSION: Given the rarity of this disease process and lack of pathognomonic imaging findings, a definitive diagnosis based solely on imaging findings alone is untenable. Select cases are used to emphasize the particularly infiltrative and aggressive nature of NUT midline carcinoma, which shows a complete disregard for normal tissue boundaries and rapid progression during brief intervals.

Incidental detection of parathyroid adenomas on chest CT before clinical presentation of hyperparathyroidism.

RATIONALE AND OBJECTIVES: To evaluate whether parathyroid adenomas can be detected by thoracic radiologists on routine chest CT. MATERIALS/METHODS: This retrospective study included patients with hyperparathyroidism evaluated by parathyroid scans and a control group with normal calcium. All had enhanced chest CT within 36 months prior to parathyroid imaging. Chest CTs were reviewed by 3 blinded thoracic radiologists. We report diagnostic accuracy for all positive findings and findings > 8 mm. RESULTS: Our sample comprised 126 patients, 63 with confirmed hyperparathyroidism and 63 control patients; 6 parathyroid cases were excluded for being out of the field of view. Readers 1, 2, and 3 had sensitivity of 95%, 60%, and 35%, and specificity of 88%, 89%, and 97%, respectively. Specificity increased to 95%, 97%, and 98% when considering only findings larger than 8 mm. Review of false negative studies for reader 1 revealed 3 parathyroid adenomas visualized in retrospect. Review of the 7 false positive studies for reader 1 revealed candidate lesions in all of them attributed to exophytic thyroid nodules or lymph nodes. 90%, 67%, and 40% of the parathyroid adenoma patients had at least 1, 2, and 3 complications respectively. Most prevalent complications were nephrolithiasis (48%) and osteopenia (46%). CONCLUSIONS: Routine contrast-enhanced chest CT can detect the majority of parathyroid adenomas with high specificity. CLINICAL RELEVANCE/APPLICATION: Increasing awareness of parathyroid adenomas by chest radiologists allow for detection of enlarged parathyroid glands, diagnosing hyperparathyroidism before clinical presentation.

ACR Appropriateness Criteria® Sepsis.

Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection. A search for the underlying cause of infection typically includes radiological imaging as part of this investigation. This document focuses on thoracic and abdominopelvic causes of sepsis. In 2017, the global incidence of sepsis was estimated to be 48.9 million cases, with 11 million sepsis-related deaths (accounting for nearly 20% of all global deaths); therefore, understanding which imaging modalities and types of studies are acceptable or not acceptable is imperative. The 5 variants provided include the most commonly encountered scenarios in the setting of sepsis along with recommendations and data for each imaging study. 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 process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

The Pre-Radiology Internship: Room for Improvement?

BACKGROUND: A clinical internship is currently required by the American Board of Radiology prior to Radiology residency. The purpose of this investigation is to evaluate practicing radiologists' perspectives on the value of the internship and their recommendations for optimization. METHODS: A five-minute online survey was distributed via email to practicing radiologist members of the American College of Radiology. RESULTS: A total of 566 completed responses (11.3% response rate) were received. Most respondents agreed that their internship was essential for improving non-radiology clinical knowledge (84%) and affirming their decision to become a radiologist (74%). Most respondents (59%) disagree that the one-year internship before residency should be eliminated. Most (53%) of the radiologists in an academic practice agreed that internship should be integrated into Radiology residency. If radiologists were to redesign the internship ("PreRad Internship"), a majority of the respondents would include training in other medical specialties (71%), working along technologists (55%) and informatics/AI/computer science (54%). While the greatest proportion (50%) of interventional radiologists reported a Surgery internship would be the most beneficial for their primary subspecialty (50%), diagnostic radiologists most commonly (27%) reported the PreRad Internship would be the most beneficial. The greatest proportions of Abdominal-, Breast-, and Neuroradiology-trained respondents reported a PreRad Internship would be the most beneficial internship for their primary field of subspecialty Radiology practice (32%, 36%, and 33%, respectively). CONCLUSION: The internship before Radiology residency offers some benefits but could be further optimized. There is support from practicing radiologists for a redesigned, more Radiology-specific PreRad Internship.

ACR Appropriateness Criteria® Routine Chest Imaging.

Routine chest imaging has been used to identify unknown or subclinical cardiothoracic abnormalities in the absence of symptoms. Various imaging modalities have been suggested for routine chest imaging. We review the evidence for or against the use of routine chest imaging in different clinical scenarios. This document aims to determine guidelines for the use of routine chest imaging as initial imaging for hospital admission, initial imaging prior to noncardiothoracic surgery, and surveillance imaging for chronic cardiopulmonary disease. 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 process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Cardiac masses, part 1: imaging strategies and technical considerations.

OBJECTIVE: The objective of this article is to discuss optimal imaging strategies for the evaluation of cardiac masses. The advantages and disadvantages of echocardiography, cardiac MRI, gated cardiac CT, and nuclear imaging will be discussed and specific techniques presented. CONCLUSION: Multimodality imaging plays a pivotal role in the diagnosis and surgical planning of cardiac masses. Clinical features, such as patient age, location, and imaging characteristics of the mass will determine the likely differential diagnosis.