Malignant Rhabdoid Tumor and Related Pediatric Tumors: Multimodality Imaging Review with Pathologic Correlation.

Malignant rhabdoid tumors (MRTs) are rare but lethal solid neoplasms that overwhelmingly affect infants and young children. While the central nervous system is the most common site of occurrence, tumors can develop at other sites, including the kidneys and soft tissues throughout the body. The anatomic site of involvement dictates tumor nomenclature and nosology. While the clinical and imaging manifestations of MRTs and other more common entities may overlap, there are some site-specific distinctive imaging characteristics. Irrespective of the site of occurrence, somatic and germline mutations in SMARCB1, and rarely in SMARCA4, underlie the entire spectrum of rhabdoid tumors. MRTs have a simple and remarkably stable genome but can demonstrate considerable molecular and biologic heterogeneity. Related neoplasms encompass an expanding category of phenotypically dissimilar (nonrhabdoid tumors driven by SMARC-related alterations) entities. US, CT, MRI, and fluorodeoxyglucose PET/CT or PET/MRI facilitate diagnosis, initial staging, and follow-up, thus informing therapeutic decision making. Multifocal synchronous or metachronous rhabdoid tumors occur predominantly in the context of underlying rhabdoid tumor predisposition syndromes (RTPSs). These autosomal dominant disorders are driven in most cases by pathogenic variants in SMARCB1 (RTPS type 1) and rarely by pathogenic variants in SMARCA4 (RTPS type 2). Genetic testing and counseling are imperative in RTPS. Guidelines for imaging surveillance in cases of RTPS are based on age at diagnosis. ©RSNA, 2024 Supplemental material is available for this article.

Non-inferiority of a non-gadolinium-enhanced magnetic resonance imaging follow-up protocol for isolated optic pathway gliomas.

BACKGROUND: Pediatric patients with optic pathway gliomas (OPGs) typically undergo a large number of follow-up MRI brain exams with gadolinium-based contrast media (GBCM), which have been associated with gadolinium tissue retention. Therefore, careful consideration of GBCM use in these children is warranted. OBJECTIVE: To investigate whether GBCM is necessary for OPG MR imaging response assessment using a blinded, non-inferiority, multi-reader study. MATERIALS AND METHODS: We identified children with OPG and either stable disease or change in tumor size on MRI using a regional cancer registry serving the U.S. Pacific Northwest. For each child, the two relevant, consecutive MRI studies were anonymized and standardized into two imaging sets excluding or including GBCM-enhanced images. Exam pairs were compiled from 42 children with isolated OPG (19 with neurofibromatosis type 1), from a population of 106 children with OPG. We included 28 exam pairs in which there was a change in size between exams. Seven pediatric radiologists measured tumor sizes during three blinded sessions, spaced by at least 1 week. The first measuring session excluded GBCM-enhanced sequences; the others did not. The primary endpoint was intra-reader agreement for ≥ 25% change in axial cross-product measurement, using a 12% non-inferiority threshold. RESULTS: Analysis demonstrated an overall 1.2% difference (95% confidence interval, -3.2% to 5.5%) for intra-reader agreement using a non-GBCM-enhanced protocol and background variability. CONCLUSION: A non-GBCM-enhanced protocol was non-inferior to a GBCM-enhanced protocol for assessing change in size of isolated OPGs on follow-up MRI exams.

Clarifying radiology's role in safety events: a 5-year retrospective common cause analysis of safety events at a pediatric hospital.

BACKGROUND: Common cause analysis of hospital safety events that involve radiology can identify opportunities to improve quality of care and patient safety. OBJECTIVE: To study the most frequent system failures as well as key activities and processes identified in safety events in an academic children's hospital that underwent root cause analysis and in which radiology was determined to play a contributing role. MATERIALS AND METHODS: All safety events involving diagnostic or interventional radiology from April 2013 to November 2018, for which the hospital patient safety department conducted root cause analysis, were retrospectively analyzed. Pareto charts were constructed to identify the most frequent modalities, system failure modes, key processes and key activities. RESULTS: In 19 safety events, 64 sequential interactions were attributed to the radiology department by the patient safety department. Five of these safety events were secondary to diagnostic errors. Interventional radiology, radiography and diagnostic fluoroscopy accounted for 89.5% of the modalities in these safety events. Culture and process accounted for 55% of the system failure modes. The three most common key processes involved in these sequential interactions were diagnostic (39.1%) and procedural services (25%), followed by coordinating care and services (18.8%). The two most common key activities were interpreting/analyzing (21.9%) and coordinating activities (15.6%). CONCLUSION: Proposing and implementing solutions based on the analysis of a single safety event may not be a robust strategy for process improvement. Common cause analyses of safety events allow for a more robust understanding of system failures and have the potential to generate more specific process improvement strategies to prevent the reoccurrence of similar errors. Our analysis demonstrated that the most common system failure modes in safety events attributed to radiology were culture and process. However, the generalizability of these findings is limited given our small sample size. Aligning with other children's hospitals to use standard safety event terminology and shared databases will likely lead to greater clarity on radiology's direct and indirect contributions to patient harm.

Dual-Energy CT of Pediatric Abdominal Oncology Imaging: Private Tour of New Applications of CT Technology.

OBJECTIVE. Dual-energy CT is gaining increasing recognition as a valuable diagnostic tool for assessing abdominal neoplasms. Nevertheless, much of the literature has focused on its use in adults. This review article illustrates specific tools available with dual-energy CT in the evaluation of pediatric abdominal neoplasms. Additionally, common imaging artifacts and pitfalls in dual-energy CT of the pediatric abdomen are outlined. CONCLUSION. Dual-energy CT can augment diagnostic yield in the imaging evaluation of pediatric abdominal neoplasms.

Brain tissue gadolinium retention in pediatric patients after contrast-enhanced magnetic resonance exams: pathological confirmation.

BACKGROUND: Retained gadolinium from gadolinium-based contrast agents (GBCAs) used in MR exams has been inferred based on signal changes on serial brain MRI and subsequently demonstrated pathologically in adults. Retention has been similarly inferred in children but pathological demonstration in pediatric patients is limited. The long-term effects of retained gadolinium are unknown but are potentially of greater concern in children given their increased vulnerability from continuing development and their expected longer period of exposure. Several factors can influence gadolinium retention. In adults as well as in children, greater accumulation has been demonstrated based on MR signal changes with linear compared with macrocyclic gadolinium chelates, attributed to lower chelate affinity with linear agents. Effects of age at exposure on retention are unknown, while differences in GBCA washout rates are still under investigation and might affect gadolinium retention relative to time of GBCA administration. OBJECTIVE: The purpose of this study was to confirm whether gadolinium brain deposits are present in pediatric patients who received GBCAs and to quantify the amounts present. MATERIALS AND METHODS: Brain autopsy specimens from 10 pediatric patients between 1 year and 13 years of age who underwent at least one contrast-enhanced MR exam were analyzed for elemental gadolinium using inductively coupled plasma mass spectrometry. Brain samples included white matter, basal ganglia (putamen, globus pallidus), thalamus, dentate nucleus and tumor tissue as available. Type and dose of contrast agent, number and timing of contrast-enhanced MR exams and renal function (estimated glomerular filtration rate [eGFR]) were documented for each child. RESULTS: Patient exposures ranged from 1 dose to 20 doses of GBCAs including both macrocyclic and linear ionic agents. Gadolinium was found to be present in brain tissue in all children and was generally highest in the globus pallidus. Those who received only macrocyclic agents showed lower levels of gadolinium retention. CONCLUSION: This study demonstrates pathological confirmation of gadolinium retention in brain tissue of a series of pediatric patients exposed to GBCAs including not only linear ionic agents but also macrocyclic agents with both nonionic and ionic compounds. The distribution and deposition levels in this small pediatric population are comparable with the findings in adults. While the clinical significance of these deposits remains unknown, at this point it would be prudent to exert caution and avoid unnecessary use of GBCAs in pediatric patients.

Ovarian torsion: developing a machine-learned algorithm for diagnosis.

BACKGROUND: Ovarian torsion is a common concern in girls presenting to emergency care with pelvic or abdominal pain. The diagnosis is challenging to make accurately and quickly, relying on a combination of physical exam, history and radiologic evaluation. Failure to establish the diagnosis in a timely fashion can result in irreversible ovarian ischemia with implications for future fertility. Ultrasound is the mainstay of evaluation for ovarian torsion in the pediatric population. However, even with a high index of suspicion, imaging features are not pathognomonic. OBJECTIVE: We sought to develop an algorithm to aid radiologists in diagnosing ovarian torsion using machine learning from sonographic features and to evaluate the frequency of each sonographic element. MATERIALS AND METHODS: All pediatric patients treated for ovarian torsion at a quaternary pediatric hospital over an 11-year period were identified by both an internal radiology database and hospital-based International Statistical Classification of Diseases and Related Health Problems (ICD) code review. Inclusion criteria were surgical confirmation of ovarian torsion and available imaging. Patients were excluded if the diagnosis could not be confirmed, no imaging was available for review, the ovary was not identified by imaging, or torsion involved other adnexal structures but spared the ovary. Data collection included: patient age; laterality of torsion; bilateral ovarian volumes; torsed ovarian position, i.e. whether medialized with respect to the mid-uterine line; presence or absence of Doppler signal within the torsed ovary; visualization of peripheral follicles; and presence of a mass or cyst, and free peritoneal fluid. Subsequently, we evaluated a non-torsed control cohort from April 2015 to May 2016. This cohort consisted of sequential girls and young adults presenting to the emergency department with abdominopelvic symptoms concerning for ovarian torsion but who were ultimately diagnosed otherwise. These features were then fed into supervised machine learning systems to identify and develop viable decision algorithms. We divided data into training and validation sets and assessed algorithm performance using sub-sets of the validation set. RESULTS: We identified 119 torsion-confirmed cases and 331 torsion-absent cases. Of the torsion-confirmed cases, significant imaging differences were evident for girls younger than 1 year; these girls were then excluded from analysis, and 99 pediatric patients older than 1 year were included in our study. Among these 99, all variables demonstrated statistically significant differences between the torsion-confirmed and torsion-absent groups with P-values <0.005. Using any single variable to identify torsion provided only modest detection performance, with areas under the curve (AUC) for medialization, peripheral follicles, and absence of Doppler flow of 0.76±0.16, 0.66±0.14 and 0.82±0.14, respectively. The best decision tree using a combination of variables yielded an AUC of 0.96±0.07 and required knowledge of the presence of intra-ovarian flow, peripheral follicles, the volume of both ovaries, and the presence of cysts or masses. CONCLUSION: Based on the largest series of pediatric ovarian torsion in the literature to date, we quantified sonographic features and used machine learning to create an algorithm to identify the presence of ovarian torsion - an algorithm that performs better than simple approaches relying on single features. Although complex combinations using multiple-interaction models provide slightly better performance, a clinically pragmatic decision tree can be employed to detect torsion, providing sensitivity levels of 95±14% and specificity of 92±2%.

Pediatric Mediastinal Masses:: Role of MR Imaging as a Problem-Solving Tool.

Computed tomography (CT) is the imaging modality of choice for evaluating mediastinal masses detected by radiography or clinical presentation. However, CT results can often be indeterminate. Thoracic magnetic resonance (MR) imaging is a noninvasive way to characterize mediastinal lesions, site of origin, and involvement of adjacent structures by providing higher soft tissue contrast than CT, with superior tissue characterization and higher diagnostic specificity. Thoracic MR imaging of mediastinal masses can increase diagnostic certainty, reduce the number of surgical interventions, and improve clinical decision making. In this review article, current imaging techniques and clinical applications of MR imaging as a problem-solving tool for assessing mediastinal masses in pediatric patients are discussed.

Pediatric Renal Neoplasms:: MR Imaging-Based Practical Diagnostic Approach.

Pediatric renal tumors may be malignant or benign. Wilms tumor, the most common malignant pediatric renal tumor, arises sporadically or with various syndromes. Renal cell carcinoma typically presents in older children. Renal clear cell sarcoma and rhabdoid tumor are typically less common, more aggressive, and present in younger children. Benign renal tumors include mesoblastic nephroma, multilocular cystic renal tumor, angiomyolipoma, and metanephric adenoma. Lymphoma and leukemia may secondarily involve the kidney. Although there is overlap in the imaging appearance of several pediatric renal tumors, magnetic resonance characteristics and clinical data narrow the differential diagnosis and suggest a specific diagnosis. This article reviews current MR techniques, as well as the common MR imaging characteristics of malignant and benign pediatric renal neoplasms.

Diagnosis, histopathologic correlation and management of hepatoblastoma: What the radiologist needs to know.

Hepatoblastomas are complex pediatric tumors with several pathological subtypes, some of which demonstrate differing imaging features and portend varying prognosis. The radiologist plays a major role not only in the pre-surgical evaluation and baseline staging of the tumor, but also in guiding management and evaluating prognosis based on the PRETEXT (pretreatment extent of tumor) classification. We discuss the pathology, imaging features, and baseline evaluation, with a focus on the role of the radiologist in the management of these tumors.

Surveillance magnetic resonance imaging for isolated optic pathway gliomas: is gadolinium necessary?

BACKGROUND: Pediatric optic pathway gliomas are typically indolent but have a variable clinical course. Treatment is dictated by symptoms and changes on contrast-enhanced MRI examinations. Gadolinium retention in children has motivated parsimonious use of gadolinium-based contrast agents. OBJECTIVES: To determine surveillance MR factors that motivate changes in tumor-directed therapies and extrapolate cost-efficacy of a non-contrast follow-up protocol. MATERIALS AND METHODS: Using an imaging database search we identified children with isolated optic pathway gliomas and ≥3 follow-up contrast-enhanced MRIs. We reviewed medical records and imaging for: (1) coincident changes on contrast-enhanced MRI and tumor-directed therapy, (2) demographics and duration of follow-up, (3) motivations for intervention, (4) assessment of gadolinium-based contrast agents' utility and (5) health care utilization data. We assessed cost impact in terms of relative value unit (RVU) burden. RESULTS: We included 17 neurofibromatosis type 1 (NF1) and 21 non-NF1 patients who underwent a median 16.9 and 24.3 cumulative contrast-enhanced MR exams over 7.7 years and 8.1 years of follow-up, respectively. Eight children (one with NF1) had intervention based on contrast-enhanced MR findings alone. For these eight, increased tumor size was the only common feature, and it was apparent on non-contrast T2 sequences. For the median patient, a non-contrast follow-up protocol could result in 15.9 (NF1) and 23.3 (non-NF1) fewer gadolinium-based contrast agent administrations, and a 39% lower yearly RVU burden. CONCLUSION: Pediatric patients with isolated optic pathway gliomas undergo a large number of routine contrast-enhanced MR follow-up exams. Gadolinium might not be needed for these exams to inform management decisions. Secondary benefits of a non-contrast follow-up protocol include decreased cost and risk to the patient.

Nuclear Medicine Applications in Pediatric Musculoskeletal Diseases: The Added Value of Hybrid Imaging.

The introduction of diphosphonates in the 1970s revolutionized not only nuclear medicine but musculoskeletal imaging as well, providing functional assessment of entities such as osteomyelitis, trauma, and osseous metastatic disease. Although rarely the first-line imaging modality used today, nuclear medicine procedures continue to play a pivotal role in the evaluation of musculoskeletal diseases in children, providing whole-body assessment of disease involvement. More recently, the introduction of technologies such as single-photon emission computed tomography/computed tomography (SPECT/CT), as well as newer positron-emitting tracers such as 18fluorine-fluorodeoxyglucose and sodium 18F-fluorine, particularly when combined with CT (positron emission tomography/CT), have injected new life into the older established techniques and expanded the application of nuclear medicine imaging into new arenas. This article discusses the utility of standard nuclear medicine procedures as they apply to children with musculoskeletal disorders, focusing on the added value of and indications for SPECT/CT. Subsequently, we discuss the expanding role of positron-emitting agents in infection, trauma, and for the diagnosis, staging, and therapeutic response monitoring of children with malignant bone and soft tissue tumors. Differences between disease processes encountered in children as compared with adults are discussed; developmental variants that can, but should not, be confused with disease are illustrated. The need for pediatric-specific protocols is addressed.

Vaginal Ewing Sarcoma: An Uncommon Clinical Entity in Pediatric Patients.

Ewing sarcoma, including classical Ewing sarcoma of the bone and primitive neuroectodermal tumors arising in bone or extraosseous primary sites, is a highly aggressive childhood neoplasm. We present two cases of Ewing sarcoma arising from the vagina in young girls. Previously reported cases in literature focused on their pathologic rather than radiographic features. We describe the spectrum of multimodality imaging appearances of Ewing sarcoma at this unusual primary site. Awareness of vaginal Ewing tumors may facilitate prompt diagnosis and lead to a different surgical approach than the more commonly encountered vaginal rhabdomyosarcoma.

Unusual ultrasound appearance of small bowel intussusception and secondary bowel obstruction in a child with Peutz-Jeghers syndrome.

Small bowel intussusception (SBI) in pediatric patients resolves spontaneously in the majority of cases. Pathologic small bowel intussusception with a lead point is rare in children. Ultrasound (US) is the preferred initial imaging study for the diagnosis of intussusception. We report a case of long-segment SBI and secondary bowel obstruction caused by a large hamartomatous polyp. This case emphasizes unique, atypical ultrasound findings that may be encountered in small bowel intussusception, with correlative radiographic, CT (computed tomography) and intra-operative findings. Increased awareness of these atypical imaging features can lead to early diagnosis and decrease the risk of potential complications including mesenteric venous thrombosis, bowel ischemia and necrosis.

Pediatric Thoracic Organ Transplantation: Current Indications, Techniques, and Imaging Findings.

In the past decade, with improved surgical technique and knowledge of immunosuppression, pediatric lung and heart transplantation have been established as viable therapeutic interventions for pediatric patients with end-stage cardiopulmonary disease from various underlying congenital and acquired disorders. Although outcomes for pediatric patients are similar to those for adult patients, thoracic organ transplantation in this special age group carries unique challenges for preoperative and postoperative imaging evaluation. The article provides an up-to-date review of the postoperative transplant anatomy, imaging techniques, and complications of pediatric lung and heart transplantation.

Torsion of a giant mesocolic lipoma in a child with Bannayan-Riley-Ruvalcaba syndrome.

A 6-year-old boy with Bannayan-Riley-Ruvalcaba syndrome (BRRS) presented to the emergency department with periumbilical abdominal pain for 12 h. A contrast-enhanced abdominal and pelvis CT examination revealed significant interval change in the size and appearance of a previously seen hypoattenuating right mesocolic fatty mass suggestive for lipoma, first observed 5 months prior. This lesion demonstrated new enhancing internal septations, a thickened capsule, interval development of adjacent mesenteric fat stranding and engorgement of the mesenteric vessels. Given the short follow-up interval and acute clinical presentation, imaging findings were suggestive for torsion. We present this case for the unusual imaging findings as well as to highlight the differential diagnosis for abdominal fat containing lesions by imaging in patients with BRRS and other hamartomatous syndromes.