How we do it: Cardiac implantable devices are not a contraindication to MRI: time for a paradigm shift.

Magnetic resonance imaging (MRI) is now an indispensable diagnostic tool in medicine due to its outstanding contrast resolution and absence of radiation exposure, enabling detailed tissue characterization and three-dimensional anatomical representation. This is especially important when evaluating individuals with congenital heart disease (CHD) who frequently require cardiac implantable electrical devices (CIEDs). While MRI safety issues have previously limited its use in patients with CIEDs, new advances have called these limitations into question. However, difficulties persist in the pediatric population due to the continued lack of specific safety data both related to imaging young children and the specific CIED devices they often require. This paper discusses MRI safety considerations related to imaging patients with CIEDs, investigates pediatric-specific problems, and describes thorough methods for safe MRI access, highlighting the significance of specialized institutional guidelines.

Cardiac magnetic resonance predictors for successful primary biventricular repair of unbalanced complete common atrioventricular canal.

BACKGROUND: Patients with unbalanced common atrioventricular canal can be difficult to manage. Surgical planning often depends on pre-operative echocardiographic measurements. We aimed to determine the added utility of cardiac MRI in predicting successful biventricular repair in common atrioventricular canal. METHODS: We conducted a retrospective cohort study of children with common atrioventricular canal who underwent MRI prior to repair. Associations between MRI and echocardiographic measures and surgical outcome were tested using logistic regression, and models were compared using area under the receiver operator characteristic curve. RESULTS: We included 28 patients (median age at MRI: 5.2 months). The optimal MRI model included the novel end-diastolic volume index (using the ratio of left ventricular end-diastolic volume to total end-diastolic volume) and the left ventricle-right ventricle angle in diastole (area under the curve 0.83, p = 0.041). End-diastolic volume index ≤ 0.18 and left ventricle-right ventricle angle in diastole ≤ 72° yield a sensitivity of 83% and specificity of 81% for successful biventricular repair. The optimal multimodality model included the end-diastolic volume index and the echocardiographic atrioventricular valve index with an area under the curve of 0.87 (p = 0.026). CONCLUSIONS: Cardiac MRI can successfully predict successful biventricular repair in patients with unbalanced common atrioventricular canal utilising the end-diastolic volume index alone or in combination with the MRI left ventricle-right ventricle angle in diastole or the echocardiographic atrioventricular valve index. A prospective cardiac MRI study is warranted to better define the multimodality characteristic predictive of successful biventricular surgery.

Dual-Energy CT for Pediatric Thoracic Imaging: A Review.

Dual-energy CT has expanded the potential of thoracic imaging in both children and adults. Data processing allows material- and energy-specific reconstructions, which improve material differentiation and tissue characterization compared with single-energy CT. Material-specific reconstructions include iodine, virtual unenhanced, perfusion blood volume, and lung vessel images, which can improve assessment of vascular, mediastinal, and parenchymal abnormalities. The energy-specific reconstruction algorithm allows virtual monoenergetic reconstructions, including low-energy images to increase iodine conspicuity and high-energy images to reduce beam-hardening and metal artifacts. This review highlights dual-energy CT principles, hardware, and postprocessing algorithms; the clinical applications of dual-energy CT; and the potential benefits of photon counting (the most recently introduced iteration of spectral imaging) in pediatric thoracic imaging.

Cardiac and Pericardial Neoplasms in Children: Radiologic-Pathologic Correlation.

Primary cardiac and pericardial neoplasms are rare in the pediatric population and can include both benign and malignant lesions. Rhabdomyomas, teratomas, fibromas, and hemangiomas are the most common benign tumors. The most common primary cardiac malignancies are soft-tissue sarcomas, including undifferentiated sarcomas, rhabdomyosarcomas, and fibrosarcomas. However, metastatic lesions are more common than primary cardiac neoplasms. Children with primary cardiac and pericardial tumors may present with nonspecific cardiovascular symptoms, and their clinical presentation may mimic that of more common nonneoplastic cardiac disease. The diagnosis of cardiac tumors has recently been facilitated using noninvasive cardiac imaging. Echocardiography is generally the first-line modality for evaluation. Cardiac MRI and CT are used for tissue characterization and evaluation of tumor size, extension, and physiologic effect. The varied imaging appearances of primary cardiac neoplasms can be explained by their underlying abnormality. Treatment of these lesions varies from conservative management, with spontaneous regression of some lesions such as rhabdomyomas, to surgical resection, particularly in patients with associated heart failure. With adequate imaging techniques and knowledge of the pathologic basis of the neoplasm, it is often possible to differentiate benign from malignant tumors, which can greatly affect adequate and timely treatment. ©RSNA, 2023 Quiz questions for this article are available through the Online Learning Center.

Dual-source computed tomography protocols for the pediatric chest - scan optimization techniques.

The gold standard for pediatric chest imaging remains the CT scan. An ideal pediatric chest CT has the lowest radiation dose with the least motion degradation possible in a diagnostic scan. Because of the known inherent risks and costs of anesthesia, non-sedate options are preferred. Dual-source CTs are currently the fastest, lowest-dose CT scanners available, utilizing an ultra-high-pitch mode resulting in sub-second CTs. The dual-energy technique, available on dual-source CT scanners, gathers additional information such as pulmonary blood volume and includes relative contrast enhancement and metallic artifact reduction, features that are not available in high-pitch flash mode. In this article we discuss the benefits and tradeoffs of dual-source CT scan modes and tips on image optimization.

State-of-the-art imaging for lymphatic evaluation in children.

The lymphatic system has been poorly understood and its importance neglected for decades. Growing understanding of lymphatic flow pathophysiology through peripheral and central lymphatic flow imaging has improved diagnosis and treatment options in children with lymphatic diseases. Flow dynamics can now be visualized by different means including dynamic contrast-enhanced magnetic resonance lymphangiography (DCMRL), the current standard technique to depict central lymphatics. Novel imaging modalities including intranodal, intrahepatic and intramesenteric DCMRL are quickly evolving and have shown important advances in the understanding and guidance of interventional procedures in children with intestinal lymphatic leaks. Lymphatic imaging is gaining importance in the radiologic and clinical fields and new techniques are emerging to overcome its limitations.

Patients with Post-COVID-19 Vaccination Myocarditis Have More Favorable Strain in Cardiac Magnetic Resonance Than Those With Viral Myocarditis.

There have been reports of myocarditis following vaccination against COVID-19. We sought to describe cardiac magnetic resonance (CMR) findings among pediatric patients. Retrospective review at a large academic center of patients clinically diagnosed with post-vaccine myocarditis (PVM) undergoing CMR. Data collected included parametric mapping, ventricular function, and degree of late gadolinium enhancement (LGE). Post-processing strain analysis was performed using feature tracking. Strain values, T1/T2 values, and ventricular function were compared to age- and gender-matched controls with viral myocarditis using a Wilcoxon Signed Rank test. Among 12 patients with presumed PVM, 11 were male and 11 presented after the second vaccination dose, typically within 4 days. All presented with chest pain and elevated troponin. 10 met MRI criteria for acute myocarditis. All had LGE typically seen in the lateral and inferior walls; only five had prolonged T1 values. 10 met criteria for edema based on skeletal muscle to myocardium signal intensity ratio and only 5 had prolonged T2 mapping values. Patients with PVM had greater short-axis global circumferential and radial strain, right ventricle function, and cardiac output when compared to those with viral myocarditis. Patients with PVM have greater short-axis global circumferential and radial strains compared to those with viral myocarditis. LGE was universal in our cohort. Signal intensity ratios between skeletal muscle and myocardium may be more sensitive in identifying edema than T2 mapping. Overall, the impact on myocardial strain by CMR is less significant in PVM compared to more classic viral myocarditis.

Dynamic contrast-enhanced MR lymphangiography: feasibility of using ferumoxytol in patients with chronic kidney disease.

PURPOSE: To assess the feasibility of direct intra-lymphatic administration of diluted ferumoxytol as a T1-positive contrast agent for dynamic contrast-enhanced MR lymphangiography (DCMRL) imaging of the central lymphatics in children with renal disease. METHODS: In vitro scan of dilute ferumoxytol was initially performed using time-resolved and high-resolution 3D gradient echo (GRE) sequences with short TE values (1 to 1.5 ms). A ferumoxytol concentration of 0.25 to 0.40 mg/mL was found to retain high signal in the T1-weighted sequences. DCMRL was then performed in 4 children with renal disease with the same 3D GRE sequences administrating diluted ferumoxytol via intra-mesenteric (IM), intra-hepatic (IH), and intra-nodal (IN) routes (6 to 9 mL to each site; average total dose of 0.75 mg/kg) by slow hand injection (0.5 to 1.0 mL/min). The signal-to-noise ratio (SNR) of the lymphatics was measured for quantitative evaluation. RESULTS: Ferumoxytol-enhanced DCMRL was technically successful in all patients. Contrast conspicuity within the lymphatics was sufficient without subtraction. The mean SNR was significantly higher than the muscle (50.1 ± 12.2 vs 13.2 ± 2.8; t = 15.9; p < .001). There were no short-term complications attributed to the administration of ferumoxytol in any of the four patients. CONCLUSION: Magnetic resonance lymphangiography using ferumoxytol via IN, IH, and IM access is a new method to directly visualize the central lymphatic system and can be applied safely in patients with renal failure based on our preliminary report of four cases. Ferumoxytol-enhanced DCMRL shows diagnostic image quality by using 3D GRE sequences with short TE values and appropriate dilution of ferumoxytol. KEY POINTS: • MR lymphangiography using ferumoxytol via intra-nodal, intra-hepatic, and intra-mesenteric access is a new method to directly visualize the central lymphatic system from the groin to the venous angle. • FDCMRL can be applied safely in patients with renal failure based on our preliminary report of four cases. • FDCMRL shows diagnostic image quality by using 3D GRE sequences with short TE values and appropriate dilution of the ferumoxytol.

Liver lymphatic anatomy and role in systemic lymphatic disease.

OBJECTIVES: To characterize hepatic to systemic lymphatic connections in patients with systemic lymphatic disease using intra-hepatic lymphangiography and to compare outcomes after lymphatic intervention. METHODS: In this retrospective study, patients with intra-hepatic lymphangiography from May 2014 - April 2019 at our institution were included. Imaging review was performed and hepatic lymphatic connections and flow patterns were characterized. Clinical data were reviewed and comparisons between patients undergoing lymphatic intervention with or without abnormal hepatic lymphatics were performed. RESULTS: During the study period, 105 patients underwent intra-hepatic lymphangiography. Primary clinical presentation included ascites (19/105), chylothorax (27/105), plastic bronchitis (PB) (17/105), and protein losing enteropathy (PLE) (42/105). Five categories of hepatic lymphatic connections and flow patterns were identified (%): normal (25%, 26/105), hepatoperitoneal (12%, 13/105), hepatopulmonary (10.5%, 11/105), hepatomesenteric (7.5%, 8/105), and hepatoduodenal (41%, 43/105) with four patients having more than one abnormal pattern. A comparison between clinical presentation and imaging category revealed an increased likelihood of having ascites with hepatoperitoneal (p < .0001), chylothorax/PB with hepatopulmonary (p = .01), and PLE with hepatoduodenal (p < .001) connections. Seventy-six patients had a lymphatic intervention, 24% with normal, and 76% with abnormal liver lymphatics. There was no difference in length of hospital stay or mortality between the two groups, but there was a prolonged time to symptom resolution (p = .006) and persistent symptoms after 6 months (5% vs 44%, p = .002) in the group with abnormal liver lymphatics. CONCLUSION: We identified five liver lymphatic imaging categories with a substantial correlation to presenting lymphatic disease. Abnormal imaging patterns correlated with increased morbidity. Evaluation of liver lymphatics should be considered in patients with a systemic lymphatic disease if central lymphatic imaging is normal. KEY POINTS: • We identified five liver lymphatic imaging patterns: normal, hepatoperitoneal, hepatomesenteric, hepatopulmonary, and hepatoduodenal. • Imaging patterns were correlated with disease presentation (normal - chylothorax/PB, hepatoperitoneal - ascites/chylothorax, hepatopulmonary - chylothorax/PB, hepatoduodenal - PLE). • Abnormal imaging patterns correlated with increased morbidity.

Understanding Lymphatic Anatomy and Abnormalities at Imaging.

Lymphatic abnormalities encompass a wide range of disorders spanning solitary common cystic lymphatic malformations (LMs) to entities involving multiple organ systems such as lymphangioleiomyomatosis. Many of these disorders are rare, yet some, such as secondary lymphedema from the treatment of malignancy (radiation therapy and/or lymph node dissection), affect millions of patients worldwide. Owing to complex and variable anatomy, the lymphatics are not as well understood as other organ systems. Further complicating this is the variability in the description of lymphatic disease processes and their nomenclature in the medical literature. In recent years, medical imaging has begun to facilitate a deeper understanding of the physiology and pathologic processes that involve the lymphatic system. Radiology is playing an important and growing role in the diagnosis and treatment of many lymphatic conditions. The authors describe both normal and common variant lymphatic anatomy. Various imaging modalities including nuclear medicine lymphoscintigraphy, conventional lymphangiography, and MR lymphangiography used in the diagnosis and treatment of lymphatic disorders are highlighted. The authors discuss imaging many of the common and uncommon lymphatic disorders, including primary LMs described by the International Society for the Study of Vascular Anomalies 2018 classification system (microcystic, mixed, and macrocystic LMs; primary lymphedema). Secondary central lymphatic disorders are also detailed, including secondary lymphedema and chylous leaks, as well as lymphatic disorders not otherwise easily classified. The authors aim to provide the reader with an overview of the anatomy, pathology, imaging findings, and treatment of a wide variety of lymphatic conditions. ©RSNA, 2022.

Dynamic Contrast Magnetic Resonance Lymphangiography Localizes Lymphatic Leak to the Duodenum in Protein-Losing Enteropathy.

OBJECTIVES: Protein-losing enteropathy (PLE) is a disorder of intestinal lymphatic flow resulting in leakage of protein-rich lymph into the gut lumen. Our primary aim was to report the imaging findings of dynamic contrast magnetic resonance lymphangiography (DCMRL) in patients with PLE. Our secondary objective was to use these imaging findings to characterize lymphatic phenotypes. METHODS: Single-center retrospective cohort study of patients with PLE unrelated to single-ventricle circulation who underwent DCMRL. We report imaging findings of intranodal (IN), intrahepatic (IH), and intramesenteric (IM) access points for DCMRL. RESULTS: Nineteen patients 0.3-58 years of age (median 1.2 years) underwent 29 DCMRL studies. Primary intestinal lymphangiectasia (PIL) was the most common referring diagnosis (42%). Other etiologies included constrictive pericarditis, thoracic insufficiency syndrome, and genetic disorders. IN-DCMRL demonstrated a normal central lymphatic system in all patients with an intact thoracic duct and localized duodenal leak in one patient (1/19, 5%). IH-DCMRL detected a duodenal leak in 12 of 17 (71%), and IM-DCMRL detected duodenal leak in 5 of 6 (83%). Independent of etiology, lymphatic leak was only visualized in the duodenum. CONCLUSIONS: In patients with PLE, imaging via DCMRL reveals that leak is localized to the duodenum regardless of etiology. Comprehensive imaging evaluation with three access points can provide detailed information about the site of duodenal leak.

Determination of Contrast Timing by Time-Resolved Magnetic Resonance Angiography in Patients With Bidirectional Glenn and Hemi-Fontan Anastomoses.

PURPOSE: Children with single-ventricle congenital heart disease undergo a series of operations to maintain their pulmonary circulation including bidirectional Glenn (BDG) or hemi-Fontan in the second stage to create a superior cavopulmonary anastomosis. We aimed to optimize cardiovascular angiography protocols by determining optimal contrast timing of pulmonary and systemic circulation on magnetic resonance angiography (MRA) performed with the technique of time-resolved imaging with interleaved stochastic trajectories (TWIST). METHODS AND MATERIALS: Cardiac TWIST MRA with lower extremity (LE) contrast injection was analyzed in 92 consecutive patients with a BDG or hemi-Fontan anastomosis. Contrast arrival time to inferior vena cava was set to zero to determine the relative time-to-peak (TTP) of the target vessels. Time-to-peak of each vessel was compared by age (<2 or ≥2 y), ejection fraction (<54% or ≥54%), the median values of heart rate (<111 or ≥111 beats per minute), body surface area (BSA, <0.59 or ≥0.59), cardiac index (<6.04 or ≥6.04), and indexed ascending aorta flow (AscAo_i, <5.3 or ≥5.3). The TTP of the vessels was also correlated with the volumetric parameters. RESULTS: The mean age of 92 patients (32 female, 60 male) was 3.1 years (0.7-5.6 years). With LE injection, the first peak was depicted in AscAo. Time-to-peak of the pulmonary arteries was approximately 9 seconds later than AscAo. The TTP difference between pulmonary arteries and AscAo was shorter in high heart rate group (8.3 vs 10 seconds, P < 0.001). The TTP difference between AscAo and the mean of pulmonary arteries was significantly shorter in high cardiac index group (8.4 vs 9.9 seconds, P < 0.01) and high AscAo_i group (8.7 vs 9.7 seconds, P = 0.03). The TTP differences were not significant by age, ejection fraction, and BSA. Cardiac index and AscAo_i were negatively correlated with all TTPs except AscAo. The ejection fraction, stroke volume, and atrioventricular regurgitation fraction did not correlate with the TTP. CONCLUSIONS: In patients with BDG or hemi-Fontan anastomosis, TTP of the pulmonary arteries on TWIST MRA via LE intravenous injection is approximately 9 seconds later than AscAo, approximately 8 and 10 seconds later in high and low heart rate groups, respectively. Cardiac index and AscAo_i have less effect on the TTP than the heart rate. There was no TTP difference of the pulmonary arteries by age, BSA, and ejection fraction and no correlation with ejection fraction, stroke volume, and atrioventricular regurgitation fraction. These data can be used to guide timing of pulmonary arterial enhancement of single-ventricle patients after BDG or hemi-Fontan anastomosis.

Computed tomography of the airways and lungs in congenital heart disease.

The presence of airway and lung disease in children with congenital heart disease is commonly observed with both cardiac CT angiography and routine chest CT. In this review we discuss abnormalities encountered on CT imaging of the chest beyond the heart and central vasculature, focusing on the airways, lung parenchyma and peripheral vasculature. Preoperative and postoperative findings are reviewed as well.

Spectral imaging in the pediatric chest: past, present and future.

Computed tomography technology continues to undergo evolution and improvement with each passing decade. From its inception in 1971, to the advent of commercially available dual-energy CT just over a decade ago, and now to the latest innovation, photon-counting detector CT, CT's utility for resolving and discriminating tissue types improves. In this review we discuss the impact of spectral imaging, including dual-energy CT and the recently available photon-counting detector CT, on the imaging of the pediatric chest. We describe the current capabilities and future directions of CT imaging, encompassing both the lungs and the surrounding tissues.

Dynamic contrast-enhanced magnetic resonance lymphangiography.

Lymphatic flow disorders include a broad spectrum of abnormalities that can originate in the lymphatic or the venous system. The development of these disorders is multifactorial and is most commonly associated with congenital heart diseases and palliative surgeries that these patients undergo. Central lymphatic disorders might be secondary to traumatic leaks, lymphatic overproduction, conduction abnormalities or lymphedema, and they can progress to perfusion anomalies. Several imaging modalities have been used to visualize the lymphatic system. However, the imaging of central lymphatic flow has always been challenging. Dynamic contrast-enhanced magnetic resonance lymphangiography (DCMRL) allows for visualization of central lymphatic flow disorders and has been recently applied for the assessment of plastic bronchitis, protein-losing enteropathy, chylothorax and chylopericardium, among other lymphatic disorders. The hepatic and mesenteric accesses are innovative and promising techniques for better identification and understanding of these abnormalities. The main objectives of this review are to discuss the physiology and anatomy of the lymphatic system and review the current uses of DCMRL in the diagnosis and management of lymphatic flow disorders.

Lymphatic anomalies in congenital heart disease.

Congenital heart disease can lead to various lymphatic complications including traumatic leaks, lymphatic overproduction, conduction abnormalities or lymphedema. Advancements in the imaging of central lymphatics and guided interventions have improved outcomes in these children. Dynamic contrast-enhanced magnetic resonance (MR) lymphangiography allows for the assessment of abnormal lymphatic drainage. This technique is preferred for evaluating lymphatic conditions such as plastic bronchitis, chylothorax, chyloptysis, chylopericardium, protein-losing enteropathy and chylous ascites, among other lymphatic disorders. In this review, we discuss lymphatic abnormalities encountered on MRI in children with congenital heart disease. We also briefly review treatment options.

Optimizing neonatal cardiac imaging (magnetic resonance/computed tomography).

Magnetic resonance imaging (MRI) and CT perform an important role in the evaluation of neonates with congenital heart disease (CHD) when echocardiography is not sufficient for surgical planning or postoperative follow-up. Cardiac MRI and cardiac CT have complementary applications in the evaluation of cardiovascular disease in neonates. This review focuses on the indications and technical aspects of these modalities and special considerations for imaging neonates with CHD.

Mediastinal Masses in Children: Radiologic-Pathologic Correlation.

Most pediatric masses in the chest are located in the mediastinum. These masses are often initially detected incidentally on chest radiographs in asymptomatic children, although some patients may present with respiratory symptoms. At chest radiography, the mediastinum has been anatomically divided into anterior, middle, and posterior compartments. However, with the International Thymic Malignancy Interest Group classification scheme, which is based on cross-sectional imaging findings, the mediastinum is divided into prevascular, visceral, and paravertebral compartments. In the prevascular compartment, tumors of thymic origin, lymphomas, germ cell tumors, and vascular tumors are encountered. In the visceral compartment, lymphadenopathy and masses related to the foregut are seen. In the paravertebral compartment, neurogenic tumors are most common. Using the anatomic location in combination with knowledge of the imaging and pathologic features of pediatric mediastinal masses aids in accurate diagnosis of these masses to guide treatment and management decisions. An invited commentary by Lee and Winant is available online. ©RSNA, 2021.

Characterization of Disease Phenotype in Very Preterm Infants with Severe Bronchopulmonary Dysplasia.

Rationale: Bronchopulmonary dysplasia (BPD) is a heterogenous condition with poorly characterized disease subgroups.Objectives: To define the frequency of three disease components: moderate-severe parenchymal disease, pulmonary hypertension (PH), or large airway disease, in a referral cohort of preterm infants with severe BPD. The association between each component and a primary composite outcome of death before hospital discharge, tracheostomy, or home pulmonary vasodilator therapy was assessed.Methods: This was a retrospective, single-center cohort study of infants born at <32 weeks' gestation with severe BPD who underwent both chest computed tomography with angiography (CTA) and echocardiography between 40 and 50 weeks postmenstrual age between 2011 and 2015. Moderate-severe parenchymal lung disease was defined as an Ochiai score ≥8 on CTA. PH was diagnosed by echocardiogram using standard criteria. Large airway disease was defined as tracheomalacia or bronchomalacia on bronchoscopy and/or tracheoscopy or CTA.Measurements and Main Results: Of 76 evaluated infants, 73 (96%) were classifiable into phenotypic subgroups: 57 with moderate-severe parenchymal disease, 48 with PH, and 44 with large airway disease. The presence of all three disease components was most common (n = 23). Individually, PH and large airway disease, but not moderate-severe parenchymal disease, were associated with increased risk for the primary study outcome. Having more disease components was associated with an incremental increase in the risk for the primary outcome (2 vs. 1: odds ratio, 4.9; 95% confidence interval, 1.4-17.2 and 3 vs. 1: odds ratio, 12.8; 95% confidence interval, 2.4-70.0).Conclusions: Infants with severe BPD are variable in their predominant pathophysiology. Disease phenotyping may enable better risk stratification and targeted therapeutic intervention.

Contrast-enhanced ultrasound in pediatric echocardiography.

The safety and benefits of cardiac contrast-enhanced ultrasound (CEUS) have been demonstrated in children and adolescents for a variety of clinical indications, including congenital heart disease. Cardiac CEUS is performed with US and the intravenous administration of ultrasound contrast agents (UCAs). It improves transthoracic echocardiography, which can be challenging in children and adults with acoustic window limitations (e.g., from obesity) and alterations in chest wall and cardiac geometry (e.g., from prior surgical procedures). Cardiac CEUS is also used to evaluate ischemia in the follow-up of congenital and acquired heart disease. In 2019, the United States Food and Drug Administration (FDA) approved a UCA for pediatric echocardiography. This article focuses on the clinical applications of UCAs in pediatric and adult echocardiography, outlining its diagnostic value, safety and potential for future applications.