The Short and Long of COVID-19: A Review of Acute and Chronic Radiologic Pulmonary Manifestations of SARS-2-CoV and Their Clinical Significance.

Coronavirus disease 2019 (COVID-19) pneumonia has had catastrophic effects worldwide. Radiology, in particular computed tomography (CT) imaging, has proven to be valuable in the diagnosis, prognostication, and longitudinal assessment of those diagnosed with COVID-19 pneumonia. This article will review acute and chronic pulmonary radiologic manifestations of COVID-19 pneumonia with an emphasis on CT and also highlighting histopathology, relevant clinical details, and some notable challenges when interpreting the literature.

Photon-counting detector CT allows significant reduction in radiation dose while maintaining image quality and noise on non-contrast chest CT.

Purpose: To investigate if clinical non-contrast chest CT studies obtained with PCD CT using much lower radiation exposure can achieve the same image quality as with the currently established EID protocol. Materials/methods: A total of seventy-one patients were identified who had a non-contrast chest computed tomography (CT) done on PCD CT and EID CT scanners within a 4-month interval. Five fellowship trained chest radiologists, blinded to the scanner details were asked to review the cases side-by-side and record their preference for images from either the photon-counting-detector (PCD) CT or the energy-integrating detector (EID) CT scanner. Results: The median CTDIvol for PCD-CT system was 4.710 mGy and EID system was 7.80 mGy (p < 0.001). The median DLP with the PCD-CT was 182.0 mGy.cm and EID system was 262.60 mGy.cm (p < 0.001). The contrast to noise ratio (CNR) was superior on the PCD-CT system 59.2 compared to the EID-CT 53.3; (p < 0.001). Kappa-statistic showed that there was poor agreement between the readers over the image quality from the PCD and EID scanners (κ = 0.19; 95 % CI: 0.12 - 0.27; p < 0.001). Chi-square analysis revealed that 3 out of 5 readers showed a significant preference for images from the PCDCT (p ≤ 0.012). There was no significant difference in the preferences of two readers between EID-CT and PCD-CT images. Conclusion: The first clinical PCD-CT system allows a significant reduction in radiation exposure while maintaining image quality and image noise using a standardized non-contrast chest CT protocol.

Nocardia caishijiensis infection: a case report and review of the literature.

BACKGROUND: Nocardia caishijiensis is a rare soil actinomycete first described in Anhui province, China, in 2003. There has been only one reported instance of human infection caused by this species in the current literature. CASE PRESENTATION: We present a case of pulmonary nocardiosis caused by Nocardia caishijiensis in a fifty-two-year-old man with human immunodeficiency virus infection and concomitant use of high-dose dexamethasone for cervical myelopathy, treated successfully with amikacin and thrimetroprim-sulfametoxazole, antibiotic resistance pattern was obtained, although interpretation may be limited. CONCLUSION: To our knowledge, this is the first reported case of Nocardia caishijiensis infection in humans in North America and the second one in the literature, this pathogen should be recognized as a potentially rising etiology of nocardiosis, especially in solid organ transplant recipients. This has a rising importance as the survival for solid organ recipients continue to rise with advance in transplant medicine leading to increased life expectancy in this particularly susceptible group.

Comparative Evaluation of Choose Your Own Adventure and Traditional Linear Case Formats in Radiology Small Group Teaching.

RATIONALE AND OBJECTIVES: We aim to compare Choose Your Own Adventure (CYOA) presentation format with linear case format as educational methods for teaching a radiology small group session to medical students. MATERIALS AND METHODS: A radiology small group session was held for preclinical second-year medical students in the pulmonary course, whereby eight classrooms of students and eight radiology facilitators were each randomized to do either the linear case format or the nonlinear CYOA presentation format. All students in attendance were administered a survey at the end of the session, which assessed students' perceptions using five-point Likert-type questions. The survey also contained a four-question knowledge quiz on chest radiology. The facilitators were administered a qualitative survey as well. Between-group analyses were performed using Student's t-test. RESULTS: Of the 144 students who attended the small group sessions, 143 students completed the survey (99.3%). The CYOA format group reported significantly greater engagement in the cases (4.5 ± 0.7 vs. 3.8 ± 0.7, p < 0.001), satisfaction with the format (4.6 ± 0.6 vs. 3.7 ± 0.9, p < 0.001), and enhancement of clinical decision making skills (4.5 ± 0.6 vs. 3.5 ± 0.9, p < 0.001). The linear format group reported a greater role for the facilitator to add value (4.6 ± 0.5 vs. 4.3 ± 1.1, p = 0.033). There was no significant difference between groups in performance on the knowledge quiz. CONCLUSION: Medical students reported higher satisfaction, engagement, and enhanced clinical decision making skills with the CYOA presentation method compared to linear case format for radiology small group learning.

Severe Acute Cellular Rejection With High-Grade Lymphocytic Bronchiolitis Following Transition from Tacrolimus to Belatacept in a Lung Transplantation Recipient: A Case Report.

This case report describes a lung transplantation recipient who developed severe acute cellular rejection with high-grade lymphocytic bronchiolitis after transition to a calcineurin-free regimen using belatacept. A 53-year-old man who had undergone lung transplantation 3 years prior developed progressive chronic kidney disease related to tacrolimus. He was transitioned off tacrolimus to belatacept to prevent the need for dialysis. He was admitted 2 months later with acute hypoxemic respiratory failure. Video-assisted thoracic surgery biopsy showed acute fibrinous and organizing pneumonia and A4B2 rejection. He subsequently developed chronic lung allograft dysfunction. This case illustrates the potential increased risk of acute rejection associated with belatacept maintenance immunosuppression.

Management Strategies for Patients Presenting With Symptomatic Lymphadenopathy and Breast Edema After Recent COVID-19 Vaccination.

Ipsilateral axillary lymphadenopathy is a well-documented finding associated with COVID-19 vaccination. Varying guidelines have been published for the management of asymptomatic patients who have a history of recent vaccination and present with incidental lymphadenopathy at screening mammography. Some experts recommend follow-up imaging, and others suggest that clinical management, rather than repeat imaging or biopsy, is appropriate. Symptomatic patients with lymphadenopathy and/or additional abnormal imaging findings should be treated differently depending on risk factors and clinical scenarios. Although ipsilateral lymphadenopathy is well documented, ipsilateral breast edema after COVID-19 vaccination has been rarely reported. The combination of ipsilateral lymphadenopathy and diffuse breast edema after COVID-19 vaccination presents a clinical management challenge because edema can obscure underlying abnormalities at imaging. For symptomatic patients with lymphadenopathy and associated breast parenchymal abnormality, prompt action is appropriate, including diagnostic evaluation and consideration of tissue sampling. This approach may prevent delays in diagnosis and treatment of patients with malignancy masked by symptoms from the vaccination.

Harnessing Augmented Reality and CT to Teach First-Year Medical Students Head and Neck Anatomy.

RATIONALE AND OBJECTIVES: Three-dimensional (3D) visualization has been shown to benefit new generations of medical students and physicians-in-training in a variety of contexts. However, there is limited research directly comparing student performance after using 3D tools to those using two-dimensional (2D) screens. MATERIALS AND METHODS: A CT was performed on a donated cadaver and a 3D CT hologram was created. A total of 30 first-year medical students were randomly assigned into two groups to review head and neck anatomy in a teaching session that incorporated CT. The first group used an augmented reality headset, while the second group used a laptop screen. The students were administered a five-question anatomy test before and after the session. Two-tailed t-tests were used for statistical comparison of pretest and posttest performance within and between groups. A feedback survey was distributed for qualitative data. RESULTS: Pretest vs. posttest comparison of average percentage of questions answered correctly demonstrated both groups showing significant in-group improvement (p < 0.05), from 59% to 95% in the augmented reality group, and from 57% to 80% in the screen group. Between-group analysis indicated that posttest performance was significantly better in the augmented reality group (p = 0.022, effect size = 0.73). CONCLUSION: Immersive 3D visualization has the potential to improve short-term anatomic recall in the head and neck compared to traditional 2D screen-based review, as well as engage millennial learners to learn better in anatomy laboratory. Our findings may reflect additional benefit gained from the stereoscopic depth cues present in augmented reality-based visualization.

Delayed-Phase Enhancement for Evaluation of Malignant Pleural Mesothelioma on Computed Tomography: A Prospective Cohort Study.

BACKGROUND: Radiologic assessment of malignant pleural mesothelioma (MPM) on computed tomography (CT) imaging can be limited by similar attenuations of MPM and adjacent tissues. This can result in inaccuracies in defining the presence and extent of pleural tumor burden. We hypothesized that increasing the time delay for pleural enhancement will optimize discrimination between MPM and noncancerous tissues on CT. Here we conduct a prospective observational study to determine the optimal time delay for imaging MPM on CT. PATIENTS AND METHODS: Adult MPM patients (n = 15) were enrolled in this prospective exploratory imaging trial. Patients with < 1 cm MPM thickness, prior pleurectomy, pleurodesis, pleural radiotherapy, or antiangiogenic therapy were excluded. All patients underwent a dynamically-enhanced CT with multiple time delays (0 - 10 minutes) after intravenous contrast administration. Tumor tissue attenuation was measured at each phase of enhancement. A qualitative assessment of tumor enhancement kinetics was also performed. The optimal phase of enhancement based on qualitative lesion conspicuity and quantitative tumor enhancement was then compared. RESULTS: MPM tumor enhancement was quantitatively and qualitatively increased at time delays beyond the conventional time delay for thoracic CT imaging (40-60 seconds). Patient tumor enhancement kinetics, displayed as the fraction of maximal tumor tissue attenuation as a function of time, revealed an optimal time delay of 230 to 300 seconds after intravenous contrast administration. There was an association between degree of tumor enhancement and subjective lesion conspicuity. CONCLUSION: Optimal MPM contrast enhancement occurs at a later phase than typically acquired with conventional thoracic CT imaging.

The Role of Imaging in the Management of Suspected or Known COVID-19 Pneumonia: A Multidisciplinary Perspective.

COVID-19 is an illness caused by a novel coronavirus that has rapidly escalated into a global pandemic leading to an urgent medical effort to better characterize this disease biologically, clinically and by imaging. In this review, we present the current approach to imaging of COVID-19 pneumonia. We focus on the appropriate utilization of thoracic imaging modalities to guide clinical management. We will also describe radiologic findings that are considered typical, atypical and generally not compatible with of COVID-19 infection. Further, we review imaging examples of COVID-19 imaging mimics, such as organizing pneumonia, eosinophilic pneumonia and other viral infections.

The Role of Imaging in the Management of Suspected or Known COVID-19 Pneumonia. A Multidisciplinary Perspective.

Coronavirus disease (COVID-19) is an illness caused by a novel coronavirus that has rapidly escalated into a global pandemic leading to an urgent medical effort to better characterize this disease biologically, clinically, and by imaging. In this review, we present the current approach to imaging of COVID-19 pneumonia. We focus on the appropriate use of thoracic imaging modalities to guide clinical management. We also describe radiologic findings that are considered typical, atypical, and generally not compatible with COVID-19. Furthermore, we review imaging examples of COVID-19 imaging mimics, such as organizing pneumonia, eosinophilic pneumonia, and other viral infections.

First-Year Radiology Residents Teaching Anatomy to First-Year Medical Students: A Symbiotic Relationship.

OBJECTIVES: Our institution has developed an educational program in which first-year radiology residents teach first-year medical students during gross anatomy laboratory sessions. The purpose of this study is to assess the impact of this program on medical student knowledge and perceptions of radiology, and on resident attitudes toward teaching. MATERIALS AND METHODS: First-year resident pairs taught small groups of medical students during weekly 15-minute interactive sessions, and were evaluated on teaching skills by senior residents. A survey about attitudes toward radiology and a knowledge quiz were sent to the medical students, and a survey about attitudes toward teaching was sent to the first-year radiology residents, both pre-course and post-course. RESULTS: Students' radiology knowledge significantly increased between the pre-course and post-course survey across all categories tested (P < 0.001). Additionally, there were significant improvements in terms of students' confidence in radiologic anatomy skills, perceived importance of radiology for medical training, familiarity with the field of radiology, and perception that radiologists are friendly (P < 0.001). Radiology residents felt more confident in their teaching proficiency (P < 0.001) by the conclusion of the course. CONCLUSIONS: Resident-led small-group teaching sessions during anatomy laboratory are mutually beneficial for medical students and radiology residents. The program also allows radiology residents to be exposed early on in residency to teaching and academic medicine.

Diagnosing dysplasia in Barrett's oesophagus still requires Seattle protocol biopsy in the era of modern video endoscopy: results from a tertiary centre Barrett's dysplasia database.

Objectives: The role of random, four-quadrant biopsy (i.e. systematic biopsy) in Barrett's oesophagus surveillance has been questioned given its drawbacks and the emergence of high-resolution endoscopy and advanced imaging modalities. Our study aims to assess whether neoplastic pathology is typically diagnosed in routine clinical practice by random, four-quadrant or targeted biopsy whilst using high-resolution endoscopy.Methods: The Nottingham University Hospital Barrett's oesophagus dysplasia database was retrospectively analysed. Endoscopic and histopathologic data pertaining to the initial endoscopy in which pathology was diagnosed was extracted from the medical records. The most advanced histopathologic abnormality at initial diagnosis and within twelve months were noted. The corresponding endoscopic impression at initial diagnosis was used to group cases per type of biopsy - random, four-quadrant or targeted. Pearson's χ2 test of independence was used to analyse the relationship between the type of biopsy and diagnosis, indication for endoscopy, endoscopist level and advanced techniques used.Results: Of the 222 patients involved in the study - a higher proportion were diagnosed through random, four-quadrant biopsy (72.97%) than targeted biopsy (27.03%). 90.91% of low-grade dysplasia, 71.43% of high-grade dysplasia and 50% of intramucosal adenocarcinoma cases were diagnosed by random, four-quadrant biopsy. Across all grades of clinicians, patients were typically diagnosed through random, four-quadrant biopsy. However, amongst specialist consultant endoscopists (n = 10) the proportion was equal.Conclusions: Our findings strongly emphasize the importance of random, four-quadrant biopsy in the detection of not only low-grade dysplasia, but also high-grade dysplasia and early invasive carcinoma as part of Barrett's oesophagus surveillance.

Patient-Centered and Specialty-Specific Case Work-Up: An Effective Method for Teaching Appropriateness of Imaging to Medical Students.

RATIONALE AND OBJECTIVES: Our institution has developed a mini-course program within the diagnostic radiology elective curriculum that promotes active learning, using patient cases specifically tailored to students' future specialties. The purpose of this study is to evaluate the effectiveness of this mini-course on medical student knowledge of imaging appropriateness and attitude toward radiologist consultation. MATERIALS AND METHODS: During each month-long radiology elective course, students were divided into teams of up to four students based on their specialty interest and assigned recent patient cases with imaging findings relevant to their specialties. The students researched their customized patient cases, integrated pertinent clinical and imaging findings, and presented their findings in a final preceptor-led session. A five-point Likert-type item preprogram and postprogram survey assessing knowledge of imaging appropriateness and attitude toward radiologist consultation was sent to the enrolled medical students. RESULTS: Out of 36 medical students, 33 (92%) completed the preprogram survey and 31 (86%) completed the postprogram survey. Students reported improved confidence in knowledge of imaging appropriateness, such as indications for intravenous contrast (p < 0.0005) and oral contrast (p < 0.0005). Furthermore, students reported an improved understanding of how to utilize radiologists (p < 0.005) and how to provide pertinent clinical historical information when requesting a radiology exam (p < 0.0005). Students reported that researching the patient's historical and clinical information in conjunction with the radiology images made them more invested in the case. CONCLUSION: Assigning customized patient cases to medical students on diagnostic radiology elective, tailored to their future specialties, is an effective and active way to teach imaging appropriateness and to improve attitudes toward radiologist consultation.

Thoracic Imaging of Non-Small Cell Lung Cancer Treated With Anti-programmed Death Receptor-1 Therapy.

PURPOSE: Treatment with anti-programmed death receptor-1 (PD-1) therapeutics can lead to unconventional responses and side effect profiles due to their potentiating effects on the immune system. Here we evaluate the radiologic manifestations of anti-PD-1 therapy in the chest in patients with non-small cell lung cancer (NSCLC) receiving anti-PD-1 therapy. MATERIALS AND METHODS: A retrospective review of real-world clinical practice was conducted of all the patients with NSCLC receiving anti-PD-1 therapy at our institution between 2013 and 2016. All patients without adequate clinical or radiologic follow-up data in the electronic medical records were excluded. Imaging examinations for all patients deemed by their thoracic oncologists to have radiologic pseudoprogression or therapy-associated pneumonitis were reviewed by experienced thoracic radiologists. RESULTS: A total of 166 patients with NSCLC had available clinical and imaging data for retrospective review. Of these patients, 4 (2%) were considered to have radiologic pseudoprogression, 3 of which manifested as increased tumor size and 1 of which manifested with new lesions. A total of 5 patients (3%) were clinically deemed to have pneumonitis attributable to anti-PD-1 therapy, 4 of which had radiologic manifestations on computed tomography. CONCLUSION: Radiologic pseudoprogression and drug-induced pneumonitis are uncommon but important manifestations of anti-PD-1 therapy on thoracic imaging.

Impact of Early Radiology Research Experiences on Medical Student Perceptions of Radiology and Research.

RATIONALE AND OBJECTIVES: To promote opportunities for medical students to gain early exposure to radiology and research, our institution has initiated programs which fund summer radiology research projects for rising second-year medical students. This study assesses the impact of these faculty-mentored summer research experiences on medical student perceptions of radiology and research, in terms of both knowledge and interest. MATERIALS AND METHODS: A voluntary, anonymous survey was administered to students both before and after the summer research period. Both the pre-program survey and post-program survey included 7-point Likert-scale questions (1 = strongly disagree; 7 = strongly agree) to evaluate students' perceptions about research and students' perceptions about radiology as a specialty. Faculty mentors were sent an analogous post-program survey that included an evaluation of their student's research skills. RESULTS: The surveys were completed by 9 of 11 students and 10 of 11 mentors. Students' perceived knowledge of radiology as a specialty improved (P = 0.02) between the pre-program survey and post-program survey. Similarly, there was an increase in students' perceived knowledge of research skills (P = 0.02) between the pre-program survey and post-program survey, with student ratings of research skills consistent with those of mentors. High student interest in both radiology and research was maintained over the course of the program. CONCLUSION: Our pilot study suggests that summer research experiences can improve knowledge of radiology and research among medical students. Continued evaluation of this annual program will allow us to enhance the benefit to medical students and thereby bolster interest in academic radiology.

Determinants of new wavefront locations in cholinergic atrial fibrillation.

AIMS: Atrial fibrillation (AF) wavefront dynamics are complex and difficult to interpret, contributing to uncertainty about the mechanisms that maintain AF. We aimed to investigate the interplay between rotors, wavelets, and focal sources during fibrillation. METHODS AND RESULTS: Arrhythmia wavefront dynamics were analysed for four optically mapped canine cholinergic AF preparations. A bilayer computer model was tuned to experimental preparations, and varied to have (i) fibrosis in both layers or the epicardium only, (ii) different spatial acetylcholine distributions, (iii) different intrinsic action potential duration between layers, and (iv) varied interlayer connectivity. Phase singularities (PSs) were identified and tracked over time to identify rotational drivers. New focal wavefronts were identified using phase contours. Phase singularity density and new wavefront locations were calculated during AF. There was a single dominant mechanism for sustaining AF in each of the preparations, either a rotational driver or repetitive new focal wavefronts. High-density PS sites existed preferentially around the pulmonary vein junctions. Three of the four preparations exhibited stable preferential sites of new wavefronts. Computational simulations predict that only a small number of connections are functionally important in sustaining AF, with new wavefront locations determined by the interplay between fibrosis distribution, acetylcholine concentration, and heterogeneity in repolarization within layers. CONCLUSION: We were able to identify preferential sites of new wavefront initiation and rotational activity, in order to determine the mechanisms sustaining AF. Electrical measurements should be interpreted differently according to whether they are endocardial or epicardial recordings.

Radiologic Pseudoprogression during Anti-PD-1 Therapy for Advanced Non-Small Cell Lung Cancer.

INTRODUCTION: Anti-programmed cell death protein 1 (PD-1) therapy can lead to unconventional tumor responses, including radiologic pseudoprogression. Here we have determined the real-world incidence of radiologic pseudoprogression in advanced NSCLC and compared radiologic response criteria for assessment of disease response. METHODS: The electronic medical records of all patients with NSCLC who were receiving anti-PD-1 therapy at our institution over a 3-year period were retrospectively reviewed, and patients with clinically suspected radiologic pseudoprogression were identified. Patients without available follow-up imaging or clinical data were excluded. Imaging examinations were then analyzed to determine whether progression was confirmed on subsequent reimaging. Assessments of tumor response by the Response Evaluation Criteria in Solid Tumors (RECIST), version 1.1 (RECIST 1.1), the unidimensional immune-related response criteria (iRRC), and the iRECIST criteria for all patients were performed and compared. RESULTS: A total of 228 consecutive patients began receiving anti-PD-1 therapy over a 3-year period. Of the 166 of these patients who were evaluable, most (80%) received nivolumab. Fifteen patients (9%) were clinically suspected of having radiologic pseudoprogression on account of tumor enlargement and/or development of new lesions on computed tomography images during the first 4 to 6 weeks of therapy, and they continued receiving anti-PD-1 therapy. Three of these patients (2%) demonstrated evidence of radiologic pseudoprogression at first reimaging. The iRRC and immune RECIST criteria were more accurate in classifying radiologic pseudoprogression as nonprogression; none of the three cases were deemed progression by the iRRC or immune RECIST, whereas all three cases were determined to be progression according to the Response Evaluation Criteria in Solid Tumors, version 1.1. CONCLUSIONS: Radiologic pseudoprogression is a clinical challenge but an uncommon occurrence in patients with NSCLC who are receiving anti-PD-1 therapy.

Limited Utility of Pulmonary Nodule Risk Calculators for Managing Large Nodules.

RATIONALE AND OBJECTIVES: The optimal management of large pulmonary nodules, at higher risk for lung cancer, has not been determined, and it remains unclear as to which patients should undergo follow-up imaging vs invasive tissue diagnosis via biopsy or surgical resection. MATERIALS AND METHODS: Through search of radiology reports, 86 nodules from our institution were identified using the inclusion criterion of solid nodules measuring greater than 8mm. We evaluated these nodules with a number of risk prediction calculators, including the Brock University model, and compared these against the proven diagnosis. RESULTS: Of 86 nodules, 59 (69%) nodules were malignant. The most accurate predictive model, the Brock University calculator, underestimated the risk for this group at 33%. At its optimal threshold, this model had a positive predictive value of 81% and negative predictive value of 53%. Notwithstanding the low negative predictive value, the positive predictive value was no better than patients clinically selected for biopsy (86% of biopsies were malignant). CONCLUSION: Existing nodule risk prediction calculators are of limited usage in guiding the management of large pulmonary nodules. At present, the accuracy of these models in this setting is inferior to expert clinical judgment, and future work is needed to develop management algorithms for higher-risk nodules.

Imaging of Intrathoracic Paragangliomas.

Intrathoracic paragangliomas are uncommon and only represent 1%-2% of paragangliomas. They are most commonly found in mediastinal compartments (aortopulmonary window or posterior mediastinum). Computed tomography, magnetic resonance, and specific nuclear medicine radiotracers are routinely used to characterize these lesions and help exclude other more common conditions. Selective angiography is currently used for preoperative embolization and mapping of the vascular supply before surgical resection, rather than for diagnostic purposes alone.