Contents

Contributors, v

Magnetic resonance imaging is a valuable tool in abdominopelvic imaging as it provides high tissue contrast and functional imaging, but it requires long acquisition times limiting clinical applications and image quality. The modality has become clinically useful through advances in acquisition and reconstruction methods. In this review, we describe some of the current and future acceleration techniques and their applications in abdominopelvic imaging.

 Introduction,  2

 Parallel imaging,  2

 Simultaneous multi-slice imaging,  2

 Compressed sensing,  4

 View sharing,  4

 Deep learning-based acceleration reconstruction,  5

 Clinical applications,  5

 Static imaging,  5

 Dynamic contrast-enhanced imaging,  7

 Deep learning,  9

 Summary,  10

 Disclosure,  10

Advanced diagnostic testing often requires more cellular tissue, so choosing intermediate-sized lesions, targeting viable portions of tumor informed by contrast enhancement or metabolic activity, and sampling targets comprehensively may be helpful for improving sample adequacy. Lymph nodes and subcutaneous nodules may be the highest yield targets, with liver and lung lesions being somewhat lower yield, and bone targets being the least likely to be adequate for advanced testing. Taking more passes, using a core biopsy technique, and using a larger needle may also help optimize the result. A good rule of thumb is taking at least 3 passes with an 18-gauge needle, if deemed safe. This more aggressive approach is generally safe and the benefits of additional information likely outweigh any small added risk. Lung biopsy targets are the highest risk, so choosing extrapulmonary targets is optimal, but larger, more peripheral lesions in the lung are safer than smaller central ones.

 Introduction,  13

General Approach to Image-Guided Biopsy,  13

 Summary,  22

 Clinics care points,  22

 Disclosure,  23

Numerous abdominal manifestations have been reported in patients with coronavirus disease 2019 (COVID-19), including involvement of the luminal gastrointestinal (GI) tract, hepatobiliary system, pancreas, kidneys, spleen, and blood vessels. Although most of the associated radiological abnormalities are nonspecific without distinguishing imaging features to suggest COVID-19, unique presentations such as findings of bowel ischemia preceding gross findings of bowel necrosis have been reported. Awareness of the spectrum of abdominal manifestations of COVID-19 allows radiologists to optimize their search pattern and to raise the possibility of this etiology when appropriate. Awareness of the possible abdominal manifestations of COVID-19 should enhance detection by radiologists and improve patient care. This review provides a comprehensive overview with illustrative imaging examples of COVID-19 in the abdomen.

 Introduction,  25

 Discussion,  26

Luminal Gastrointestinal Tract,  26

Hepatobiliary,  27

Pancreas,  29

Kidneys,  29

Spleen,  30

Vasculature,  30

 Summary,  33

 Clinics care points,  33

 Disclosure,  33

The Bosniak Classification of Cystic Renal Masses version 2019 (v2019) is an update of the original Classification. Rigorous definitions of imaging features, terms and stringent criteria for individual class assignment have not, to date, improved inter-observer agreement. A higher proportion of malignant masses are classified as Bosniak v2019 class IIF and class III compared with the original classification. The highest proportion of malignant masses is found in class III masses with “irregularities” and class IV masses with “nodules.” Future improvements in the Bosniak classification may aim to include: simplification, stratification of malignant masses by their biological aggressiveness and incorporation of radiomic features and artificial intelligence to improve the agreement, system performance and add clinical value.

 Introduction,  37

Cystic renal massesâ epidemiology, improved understanding of disease, evolving treatment, and rationale for changing Bosniak classification,  38

Summary of changes from Bosniak original to v2019,  39

Emerging evidence inter-observer agreement and proportion of malignancy,  41

 Disclosure,  43

Radiologists play a central role in pancreatic ductal adenocarcinoma (PDAC) diagnosis, staging, and treatment planning. PDAC is often identified on computed tomography (CT) with tumor resectability defined based on imaging characteristics. Biphasic CT including a pancreatic parenchymal phase and a portal venous phase acquisition is recommended with dual-energy CT affording improved tumor conspicuity compared with conventional CT. Liver MRI is required before curative surgical resection of PDAC as MRI is more sensitive for liver metastases that are a contraindication for surgery. Given overall poor PDAC outcomes due to many patients presenting with advanced-stage disease, PDAC screening is an area of active research. Radiologists will likely encounter patients with earlier-stage disease in the future so familiarity with PDAC pathophysiology and early imaging characteristics is necessary. Neoadjuvant therapy is becoming increasingly common for patients with the borderline resectable disease and the impact of neoadjuvant therapy on CT assessment of resectability is reviewed.

 Introduction,  47

Primary Tumor Morphology and Pathophysiology,  48

Early Detection,  48

Imaging Technique,  49

Assessment for Resectability,  53

Local Staging Following Neoadjuvant Therapy,  54

Quantitative Imaging,  54

 Summary,  55

 Clinics care points,  55

 Disclosure,  55

This article focuses on pattern recognition in viral pneumonias. It discusses common imaging manifestations and approaches to them from a radiologist’s standpoint. It helps us understand imaging patterns and their subtypes and when to suggest the possibility of viral infection as its etiology. It also summarizes clinical and imaging manifestations of individual respiratory viruses. Tables and figures illustrate pathogenic mechanisms and imaging features.

 Introduction,  59

 Pulmonary viral infections and host immune status,  59

 Imaging of Viral Pneumonia,  59

CT patterns in viral pneumonia (Table 2 reference should appear here),  61

 Clinical indicators of viral pneumonia,  64

 Specific viruses and their manifestations,  64

 Disclosure,  70

The higher soft tissue contrast and more extensive tissue characterization properties of magnetic resonance imaging (MRI) than computed tomography (CT) makes it a valuable tool, not only for neurologic, musculoskeletal, abdominal, and cardiac indications but also for thoracic indications. Thoracic MRI can be used to diagnose indeterminate intrathoracic lesions on CT noninvasively and to delineate extent of disease and invasiveness of masses undergoing evaluation for surgical resectability and surgical planning. Awareness and employment of its capabilities will improve patient management and care.

 Beyond computed tomography—what thoracic magnetic resonance imaging brings to the table,  73

Introduction,  73

Mediastinum,  75

Lung,  77

Pleura, Diaphragm, Chest Wall,  81

 Summary,  81

 Disclosure,  81

Hybrid cardiac MR/PET imaging allows for simultaneous PET and MR cardiac evaluation, combining the molecular specificity of PET with anatomic information, tissue characterization, and functional cardiac data from MRI for a wide range of clinical indications and research applications. This article presents an overview of the current status and possible future directions of cardiac PET/MRI. Technical challenges of combined PET and MR scanner, specifically related to attenuation correction and motion artifacts, are discussed. The article concentrates on the current and future clinical applications of hybrid PET/MR, including ischemic heart diseases, inflammatory conditions, and nonischemic cardiomyopathies.

 Introduction,  87

 Hybrid PET/MR: technical aspects,  87

Coexistence of PET and MR,  87

Attenuation Correction,  87

Motion Correction,  88

Dose Reduction Advantages of Simultaneous PET/MR,  89

 PET/MR in ischemic heart disease,  89

Perfusion Imaging,  89

Viability,  90

Coronary Artery/Atherosclerosis Imaging,  90

Predictive Value After Myocardial Infarction,  92

Heart Failure and Remodeling Imaging,  92

 PET/MR in cardiac inflammation,  92

Sarcoidosis,  92

Myocarditis,  93

Novel Inflammation Radiopharmaceuticals,  94

 PET/MR in nonischemic cardiomyopathies,  95

 Amyloidosis,  95

Amyloidosis,  95

Other Nonischemic Cardiomyopathy,  95

 Additional indications,  97

Cardio-Oncology,  97

Cardiac Masses,  97

 Final comments: future of PET/MR: precision medicine and theranostics,  97

 Summary,  98

 Disclosure,  99

 Clinics care points,  99

 Appendix,  107

Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and mortality in the United States and worldwide. Common medical therapies used in COPD do not address the lung destruction, and resultant deleterious physiologic effects, inherent in emphysema. Lung volume reduction (LVR) procedures, such as surgery and bronchoscopic lung volume reduction (BLVR), specifically target emphysema and have shown significant positive therapeutic effects compared with medical therapy alone in select patient populations. Currently, endobronchial valve placement is the only approved method of BLVR. Imaging, particularly computed tomography, plays a critical role in preprocedural and postprocedural assessment of patients undergoing LVR.

 Introduction,  111

 Lung volume reduction procedures,  112

Lung Volume Reduction Surgery,  112

Bronchoscopic Lung Volume Reduction,  113

 Preprocedural lung volume reduction imaging,  114

High-Resolution Computed Tomography,  114

Perfusion Scintigraphy,  122

 Postprocedural lung volume reduction imaging,  122

Imaging Evaluation of Therapeutic Effectiveness,  122

Procedure Complications,  124

 Future directions,  128

Imaging,  128

Lung Volume Reduction,  129

 Summary,  131

 Clinics care points,  132

Histotripsy is a noninvasive, nonthermal, and nonionizing focused ultrasound method to treat cancer. Histotripsy is based on the creation of controlled acoustic cavitation from focused short-duration ultrasound pulses at high negative pressures to mechanically destroy tissue at the cellular level without damaging intervening tissue. Treatment zones are highly precise, acellular, involute rapidly, and have relative preservation of collagenous structures such as bile ducts and large vessels. The focus of this review is the development and current status of histotripsy for the treatment of liver tumors.

 Introduction,  137

 Mechanism of action,  138

 Tissue effect,  138

 Device design,  139

Histotripsy for Liver Tumor Treatment,  139

Histotripsy in Human-scale Animal Models,  140

Histotripsy in Tumor Models,  142

Clinical Application of Histotripsy,  142

 Future developments,  143

 Summary,  144

 Disclosure,  144

Portal vein thrombosis (PVT) may lead to considerable morbidity and mortality, including bowel ischemia, variceal bleeding, decompensation of liver disease, and poorer outcomes after liver transplantation compared with patients without PVT. Management of PVT centers on clot resolution and portal vein recanalization, and anticoagulation is considered first-line therapy for most patients. In patients who progress on anticoagulation or who have chronic thrombosis unresponsive to anticoagulation, endovascular management is considered. Patient risk factors, thrombus extent, acuity/chronicity of the PVT, and transplant eligibility are assessed to determine ideal treatment. A multidisciplinary approach is essential to optimize outcomes in patients diagnosed with PVT.

 Introduction,  147

 Cirrhotic portal vein thrombosis and risk factors,  148

 Noncirrhotic portal vein thrombosis and risk factors,  148

 Pharmacologic treatment of portal vein thrombosis,  149

 Use of transjugular intrahepatic portosystemic shunt and thrombectomy in the management of portal vein thrombosis,  151

 Summary,  153

 Clinics care points,  154

The article provides a review on the imaging evaluation of common upper extremity entrapment neuropathy. The nerves are vulnerable for compression at specific anatomic locations, especially superficial locations or during pass through bony or fibromuscular tunnels. Imaging primary relies on nerve ultrasound imaging and MRI neurography to evaluate for the presence of neuropathy, nerve interruption, or a space-occupying lesion along the nerve course. The use of dedicated neurography MRI sequence can provide better evaluation of the small nerves of the upper extremity by using high-resolution sequence and vascular signal suppression techniques.

 Background,  157

 Imaging appearance of the normal and pathologic nerves,  157

 Axillary nerve entrapment,  158

 Ulnar nerve entrapment,  160

 Radial nerve entrapment,  162

 Median nerve entrapment,  163

 Summary,  168

 Clinics care points,  168

 Disclosure,  168

Cervical injections can be safely performed with the use of conventional fluoroscopy while adhering to stringent guidelines. Cervical transforaminal injections are an effective treatment option for cervical radicular pain and have been shown to reduce the rate of surgery. It is recommended that dexamethasone be used for all cervical transforaminal steroid injections due to the theoretic reduction in risk of spinal cord injury, stroke, or death. Although radiation exposure theoretically increases 2 to 4 times when using DSA compared with conventional fluoroscopy, we strongly encourage its use in cervical transforaminal epidural steroid injections due to the statistically significant decrease in detecting intravascular flow and potentially preventing catastrophic complications. Cervical interlaminar epidural steroid injections are typically conducted at the C6-7 and C7-T1 levels and are not recommended above the C6-7 level due to the increasing risk of dural puncture or direct spinal cord injury when performed at higher levels. Most complications associated with cervical interlaminar epidural steroid injections are minor and self-limited and include dural puncture headache, increased neck pain, stiffness, intracranial hypotension, and vasovagal reactions. Major complications include spinal cord injury, epidural abscess, and epidural/subdural hematoma. Over sedation should be avoided while performing cervical interlaminar epidural steroid injections as excess sedation could result in patients being unable to respond to pain or paresthesias caused by spinal cord irritation. Cervical facet joints are the primary source of pain in 26% to 70% of patients with chronic neck pain. The C2-3 facet joint is commonly associated with cervicogenic headaches as the C2-3 facet joint is also innervated by the third occipital nerve. Cervical medial branch block volumes should be less than or equal to 0.3 mL and intraarticular facet joint injection volumes should not exceed 1 mL including the contrast to prevent capsule rupture and/or aberrant injectate spread to maximize the specificity of the block. Before cervical RFA, sensory and motor stimulation should be conducted to decrease the potential risk of ablating unintended spinal nerves. We support a more stringent threshold of diagnostic response (80% or greater) on two diagnostic median branch blocks to consider cervical median branch radiofrequency ablation to optimize outcomes.

 Overview of image-guided cervical injections with updated techniques and society recommendations,  171

Cervical Transforaminal Epidural Steroid Injections,  171

Cervical Interlaminar Epidural Steroid Injections,  173

Cervical Medial Branch Blocks, Intraarticular Facet Joint Injections, and Radiofrequency Ablation,  175

 Disclosure,  177

Deep learning has become one of the major approaches in artificial intelligence (AI). In this article, we demonstrate two exemplifying applications in musculoskeletal (MSK) radiology, which has unique challenges compared with other subfields of radiology. MSK encompasses a wide range of entities and presents several challenges in terms of routine workflow including high-quality images (such as in magnetic resonance imaging [MRI]) and tissue/pathologic condition measurements with high sensitivity and specificity. Herein, we demonstrate that AI enables automatic analysis of tissues and pathologic conditions in MSK radiology. We demonstrate qualitative and quantitative results for (1) tissue segmentation from thigh MR images and (2) cartilage segmentation from knee MRI. We demonstrate that deep learning is highly promising in MSK radiology applications. We conclude the article by discussing the current limitations and future trends of deep learning in MSK applications.

 Introduction,  179

Medical artificial intelligence,  180

Unique challenges for developing artificial intelligence in musculoskeletal,  180

 Preprocessing–data cleaning/curation,  180

Inhomogeneity correction,  181

Denoising,  181

Intensity standardization,  181

 Artificial intelligence applications in musculoskeletal radiology,  181

Musculoskeletal application #1: tissue quantification via segmentation,  183

Musculoskeletal application #2: cartilage quantification via segmentation,  184

 Discussion and concluding remarks,  186

 Disclosure,  187

The 2019 novel coronavirus (COVID-19) pandemic has posed unique, sudden challenges to health care systems. This is true particularly in the context of ultrasound logistics given the risks of inherent prolonged close contact of patients with sonographers and equipment during sonographic image acquisition. We describe the adaptations and modifications in scheduling, workflow, and imaging protocols implemented in our radiology department ultrasound division (a large urban academic center). The hierarchy of controls to minimize exposures to occupational hazards to protect workers, outlined by The National Institute for Occupational Safety and Health (NIOSH) are listed from most effective to least effective: elimination, substitution, engineering controls, administrative controls, and PPE (personal protective equipment (PPE)). Most of the mitigation techniques used in the ultrasound department to reduce hazards to workers involved administrative controls and PPE. We reduced preventable risks by using sterile precautions, imaging triage, and strategically minimizing image acquisition times. These implementations provide a modifiable framework for rapid adaptation during the evolving COVID-19 pandemic, including resurgences of variant strains. This framework ensures a level of preparedness for possible future pandemics or other widespread emergencies.

 Introduction,  189

 Institutional approach used to address the problem,  190

Triage and Scheduling of Patients,  190

Prescan Planning and Precaution While Scanning,  191

Infection Control Implementations,  191

Modification of Existing Protocols,  192

Technological Considerations,  192

Reactivation and Deactivation of Operations,  193

Reactivation Plans for Outpatient Diagnostic Operation,  193

 Discussion of future directions,  193

 Disclosure,  194

Head and neck paragangliomas (HNPGL) are neuroendocrine tumors that are closely associated with the parasympathetic nervous system and occur in 4 typical tumor locations: carotid body tumor, vagal paraganglioma, jugulare paraganglioma, and tympanic paraganglioma. Imaging plays a critical role in characterizing these lesions and guiding treatment. Knowledge of paraganglia anatomy and physiology is critical to understand the classic imaging appearance of these lesions particularly on CT and MRI. Additional advanced imaging and nuclear medicine modalities exist to further characterize these lesions. Recent advances in the genetic basis of paragangliomas have implications for the role of imaging in the workup and management of patients with HNPGL. These lesions can be treated with a combination of observation, surgery, radiation, as well as radionuclide therapy in some circumstances.

 Introduction,  195

 Anatomy, development, and physiology of paraganglia,  195

Anatomy of Head and Neck Paragangliomas,  196

 Epidemiology and clinical features,  196

 Genetics,  197

Conventional Imaging Appearance,  198

 Advanced magnetic resonance imaging techniques,  200

Molecular Imaging,  204

 General imaging approach,  207

Treatment,  208

 Summary,  211

 Disclosure,  211

Discoveries about the genetic and molecular underpinnings of neoplasms have revolutionized the classification of embryonal tumors of the central nervous system, eliminating some entities and introducing new ones. This overhaul has also led to a better understanding of the developmental neurobiological origins and biological features of embryonal tumors and how those may predict their clinical behavior, response to treatment, and outcomes. In view of these recent advances, the use and role of imaging in the initial diagnostic work-up and subsequent follow-up of these tumors during and after treatment have been revised. A need now exists for the updated description of the phenotypes of the new, molecularly defined entities and establishing new imaging-molecular-clinical correlations. In addition, imaging plays a key role in staging and has unique contributions to recent, revised risk-stratification schemes, providing critical information about metastatic status in these tumors that have considerable metastatic potential during any stage of the disease. Those caring for patients with embryonal tumors of the central nervous system need to be aware of the current challenges and opportunities of diagnostic imaging, which heavily relies on magnetic resonance imaging.

 Key points for other (non-medulloblastoma) central nervous system embryonal tumors,  215

 Introduction,  216

Embryonal Tumor Entities of the Central Nervous System,  217

 Summary,  228

 Disclosure,  228

Spontaneous intracranial hypotension (SIH) is an underrecognized and often debilitating condition with a wide variety of clinical presentations. Imaging plays a critical role in the diagnostic workup for SIH given the considerable variation in patient presentation. Knowledge of the pathophysiology of the condition and its imaging manifestations are imperative for accurate diagnosis and localization of the causative spinal pathologic condition. Several imaging modalities have been described for the identification of cerebrospinal fluid (CSF) leaks and CSF-venous fistulas, each with unique advantages and disadvantages. Treatment approaches for SIH include conservative therapy, epidural blood patching, and surgery as well as promising novel techniques, which justify continued investigation.

 Introduction,  231

 Clinical presentation and pathogenesis,  231

Clinical Presentation,  231

Pathogenesis,  232

Role of Imaging in Diagnosis,  233

Treatment,  236

Surgical Approach to Discogenic Tears,  237

Open Surgical Approach,  238

Embolization,  239

 Summary,  239

 Clinics care points,  240

Contrast-enhanced mammography (CEM) is a breast imaging tool that is becoming more commonplace as published results confirm its effectiveness in multiple clinical settings, including the evaluation of indeterminate findings on screening mammography, symptomatic breast disease, preoperative assessment of disease extent, determining cancer response to neoadjuvant chemotherapy, and screening patients at elevated risk for breast cancer. CEM also offers an alternative to MRI that is less expensive, potentially more available, and more convenient, while providing comparable sensitivity and specificity. Given the promising research to date, CEM likely will be more widely adopted into clinical practice, especially once positively affirming results from multicenter prospective studies (Contrast-Enhanced Mammography Imaging Screening Trial and Rapid Access to Contrast-Enhanced Spectral Mammography) are announced.

 Introduction,  243

 Current diagnostic indications,  244

Abnormal Screening Mammography,  244

Symptomatic Breast Disease,  245

Preoperative Determination of Disease Extent,  246

Monitoring Response to Neoadjuvant Chemotherapy,  247

 Potential screening applications,  247

Supplemental Screening of Women with Dense Breasts or Elevated Lifetime Risk,  247

 Implementation of contrast-enhanced mammography into clinical practice,  248

Potential Risks,  248

Logistics,  249

Limitations,  249

 Future directions,  250

 Disclosure,  250

Whole-body MRI (WB-MRI), a nonradiation technique, implies multiregional, contiguous imaging of the entire body in one scan. Recent hardware advances include continuous table movement with integrated in-table coil technology and multichannel, multielement phased-array surface coils. Incorporation of diffusion MRI into whole-body MR acquisitions provides additional valuable functional information. Integration with molecular imaging is now possible due to MR-compatible photon detector technology. In the future, pediatric-specific flexible surface coils, novel MR sequences, and machine learning tools will continue to address operational challenges and further expand the clinical scope of these examinations.

 Introduction,  253

Operational Aspects,  253

Technical Aspects,  256

Future Prospects,  261

 Summary,  262

 Clinics care points,  262

 Disclosure,  262