Unusual imaging findings associated with abdominal pediatric germ cell tumors.

Germ cell tumors of childhood are tumors arising from germline cells in gonadal or extragonadal locations. Extragonadal germ cell tumors are characteristically located in the midline, arising intracranially or in the mediastinum, retroperitoneum, or pelvis. These tumors are generally easily diagnosed due to typical sites of origin, characteristic imaging findings, and laboratory markers. However, germ cell tumors can be associated with unusual clinical syndromes or imaging features that can perplex the radiologist. This review will illustrate atypical imaging/clinical manifestations and complications of abdominal germ cell tumors in childhood. These features include unusual primary tumors such as multifocal primaries; local complications such as ovarian torsion or ruptured dermoid; atypical presentations of metastatic disease associated with burned-out primary tumor, growing teratoma syndrome, and gliomatosis peritonei; endocrine manifestations such as precocious puberty and hyperthyroidism; and antibody mediated paraneoplastic syndrome such as anti-N-methyl-D-aspartate-receptor antibody-mediated encephalitis. This review aims to illustrate unusual imaging features associated with the primary tumor, metastatic disease, or distant complications of abdominal germ cell tumors of childhood.

FDG-PET/MRI in the presurgical evaluation of pediatric epilepsy.

In patients with drug-resistant epilepsy, difficulties in identifying the epileptogenic zone are well known to correlate with poorer clinical outcomes post-surgery. The integration of PET and MRI in the presurgical assessment of pediatric patients likely improves diagnostic precision by confirming or widening treatment targets. PET and MRI together offer superior insights compared to either modality alone. For instance, PET highlights abnormal glucose metabolism, while MRI precisely localizes structural anomalies, providing a comprehensive understanding of the epileptogenic zone. Furthermore, both methodologies, whether utilized through simultaneous PET/MRI scanning or the co-registration of separately acquired PET and MRI data, present unique advantages, having complementary roles in lesional and non-lesional cases. Simultaneous FDG-PET/MRI provides precise co-registration of functional (PET) and structural (MR) imaging in a convenient one-stop-shop approach, which minimizes sedation time and reduces radiation exposure in children. Commercially available fusion software that allows retrospective co-registration of separately acquired PET and MRI images is a commonly used alternative. This review provides an overview and illustrative cases that highlight the role of combining 18F-FDG-PET and MRI imaging and shares the authors' decade-long experience utilizing simultaneous PET/MRI in the presurgical evaluation of pediatric epilepsy.

Added Value of FDG PET/MRI in Gynecologic Oncology: A Pictorial Review.

Fluorine 18-fluorodeoxyglucose (FDG) PET and MRI independently play a valuable role in the management of patients with gynecologic malignancies, particularly endometrial and cervical cancer. The PET/MRI hybrid imaging technique combines the metabolic information obtained from PET with the excellent soft-tissue resolution and anatomic details provided by MRI in a single examination. MRI is the modality of choice for assessment of local tumor extent in the pelvis, whereas PET is used to assess for local-regional spread and distant metastases. The authors discuss the added value of FDG PET/MRI in imaging gynecologic malignancies of the pelvis, with a focus on the role of FDG PET/MRI in diagnosis, staging, assessing treatment response, and characterizing complications. PET/MRI allows better localization and demarcation of the extent of disease, characterization of lesions and involvement of adjacent organs and lymph nodes, and improved differentiation of benign from malignant tissues, as well as detection of the presence of distant metastasis. It also has the advantages of decreased radiation dose and a higher signal-to-noise ratio of a prolonged PET examination of the pelvis contemporaneous with MRI. The authors provide a brief technical overview of PET/MRI, highlight how simultaneously performed PET/MRI can improve stand-alone MRI and PET/CT in gynecologic malignancies, provide an image-rich review to illustrate practical and clinically relevant applications of this imaging technique, and review common pitfalls encountered in clinical practice. ©RSNA, 2023 Quiz questions for this article are available in the supplemental material.

The Role of SPECT and PET in Epilepsy.

OBJECTIVE. The purpose of this article is to summarize the role of molecular imaging of the brain by use of SPECT, FDG PET, and non-FDG PET radiotracers in epilepsy. CONCLUSION. Quantitative image analysis with PET and SPECT has increased the diagnostic utility of these modalities in localizing epileptogenic onset zones. A multi-modal platform approach integrating the functional imaging of PET and SPECT with the morphologic information from MRI in presurgical evaluation of epilepsy can greatly improve outcomes.

Predictors of intracranial hypertension in children undergoing ICP monitoring after severe traumatic brain injury.

PURPOSE: Intracranial hypertension (ICH) is a common and treatable complication after severe traumatic brain injury (sTBI) in children. Describing the incidence and risk factors for developing ICH after sTBI could impact clinical practice. METHODS: Retrospective cohort study from 2006 to 2015 at two university-affiliated level I pediatric trauma centers of children admitted with accidental or abusive TBI, a post-resuscitation Glasgow Coma Score (GCS) of 8 or less, and an invasive intracranial pressure (ICP) monitor. Bivariate and multivariable logistic regression analysis were performed to identify demographic, injury, and imaging characteristics in patients who received ICP directed therapies for ICH (ICP > 20 mmHg). RESULTS: Eight to 5% (271/321) of monitored patients received ICP directed therapy for ICH during their PICU stay. Ninety-seven percent of patients had an abnormality on CT scan by either the Marshall or the Rotterdam score. Of the analyzed clinical and radiologic variables, only presence of hypoxia prior to PICU arrival, female sex, and a higher Injury Severity Score (ISS) were associated with increased risk of ICH (p < 0.05). CONCLUSIONS: In this retrospective study of clinical practice of ICP monitoring in children after sTBI, the vast majority of children had an abnormal CT scan and experienced ICH requiring clinical intervention. Commonly measured clinical variables and radiologic classification scores did not significantly add to the prediction for developing of ICH and further efforts are needed to define low-risk populations that would not develop ICH.

Children with sickle cell anemia with normal transcranial Doppler ultrasounds and without silent infarcts have a low incidence of new strokes.

In a prospective cohort study, we tested the hypothesis that children with sickle cell anemia (SCA) with normal transcranial Doppler ultrasound (TCD) velocities and without silent cerebral infarcts (SCIs) would have a lower incidence rate of new neurological events (strokes, seizures or transient ischemic attacks) compared to children with normal TCD measurements and SCIs, not receiving regular blood transfusions. Nonrandomized participants from the silent cerebral infarct transfusion (SIT) Trial who had screening magnetic resonance imaging (MRI) of the brain and normal TCD measurements were included. Follow-up ended at the time of first neurological event (stroke, seizure or transient ischemic attack), start of regular blood transfusion, or loss to follow-up, whichever came first. The primary endpoint was a new neurological event. Of 421 participants included, 68 had suspected SCIs. Mean follow-up was 3.6 years. Incidence rates of new neurological events in nontransfused participants with normal TCD values with SCIs and without SCIs were 1.71 and 0.47 neurological events per 100 patient-years, respectively, P = .065. The absence of SCI(s) at baseline was associated with a decreased risk of a new neurological event (hazard ratio 0.231, 95% CI 0.062-0.858; P = .029). Local pediatric neurologists examined 67 of 68 participants with suspected SCIs and identified 2 with overt strokes classified as SCIs by local hematologists; subsequently one had a seizure and the other an ischemic stroke. Children with SCA, without SCIs, and normal TCD measurements have a significantly lower rate of new neurological events when compared to those with SCIs and normal TCD measurements. Pediatric neurology assessment may assist risk stratification.

Gamma delta lymphoma: a pictorial review of F-18 fluorodeoxyglucose PET/CT findings and a brief review of the literature.

Gamma Delta (γδ) T-cell lymphomas are uncommon and aggressive neoplasms originating from the γδ receptor-bearing lymphocytes. The most frequent entities include primary hepatosplenic γδ T-cell lymphomas, primary cutaneous γδ lymphoma, and monomorphic epitheliotropic T-cell lymphoma. F-18 fluorodeoxyglucose (FDG) PET/CT is an important modality in the staging of Hodgkin's and various non-Hodgkin's lymphoma. However, literature is scare on imaging findings of γδ lymphoma on F-18 FDG PET/CT. In this review, we discuss briefly the clinical and biological features and present the spectrum of F-18 FDG PET/CT findings of γδ lymphoma.

PET/MRI: pictorial review of hepatobiliary and pancreatic applications.

PET and MRI both play valuable roles in the management of hepatobiliary and pancreatic (HBP) malignancies. Simultaneous PET/MRI combines the excellent soft-tissue resolution and anatomic details from MRI with functional information from PET in a single comprehensive examination. MRI is the main imaging modality in evaluating HCC, playing important roles in screening, characterization, local extent, and evaluating tumor response, whereas 18F-fluorodeoxyglucose (FDG) PET can help evaluate for lymph node involvement and metastatic disease. In cholangiocarcinoma and pancreatic malignancies, both PET and MRI have excellent utility in initial staging as well as assessing treatment response. In all HBP malignancies, FDG-PET/MRI is a unique problem-solving tool in complex cases and diagnostic challenges, especially after locoregional therapy and when differentiating residual or recurrent viable disease from inflammatory and other benign processes. In this manuscript, we review the role of PET/MRI in the diagnosis, staging, assessing treatment response, and characterizing post-treatment processes. With the introduction of multiple new tracers, the value of PET/MRI has not yet been fully realized, and more studies are needed to demonstrate the utility and efficacy of PET/MRI in improving patient care in hepatobiliary and pancreatic oncology.

Magnetic resonance angiography-defined intracranial vasculopathy is associated with silent cerebral infarcts and glucose-6-phosphate dehydrogenase mutation in children with sickle cell anaemia.

Silent cerebral infarct (SCI) is the most commonly recognized cause of neurological injury in sickle cell anaemia (SCA). We tested the hypothesis that magnetic resonance angiography (MRA)-defined vasculopathy is associated with SCI. Furthermore, we examined genetic variations in glucose-6-phosphate dehydrogenase (G6PD) and HBA (α-globin) genes to determine their association with intracranial vasculopathy in children with SCA. Magnetic resonance imaging (MRI) of the brain and MRA of the cerebral vasculature were available in 516 paediatric patients with SCA, enrolled in the Silent Infarct Transfusion (SIT) Trial. All patients were screened for G6PD mutations and HBA deletions. SCI were present in 41·5% (214 of 516) of SIT Trial children. The frequency of intracranial vasculopathy with and without SCI was 15·9% and 6·3%, respectively (P < 0·001). Using a multivariable logistic regression model, only the presence of a SCI was associated with increased odds of vasculopathy (P = 0·0007, odds ratio (OR) 2·84; 95% Confidence Interval (CI) = 1·55-5·21). Among male children with SCA, G6PD status was associated with vasculopathy (P = 0·04, OR 2·78; 95% CI = 1·04-7·42), while no significant association was noted for HBA deletions. Intracranial vasculopathy was observed in a minority of children with SCA, and when present, was associated with G6PD status in males and SCI.

Dynamic 18F-FDOPA-PET/MRI for the preoperative evaluation of gliomas: correlation with stereotactic histopathology.

BACKGROUND: MRI alone has limited accuracy for delineating tumor margins and poorly predicts the aggressiveness of gliomas, especially when tumors do not enhance. This study evaluated simultaneous 3,4-dihydroxy-6-[18F]fluoro-L-phenylalanine (FDOPA)-PET/MRI to define tumor volumes compared to MRI alone more accurately, assessed its role in patient management, and correlated PET findings with histopathology. METHODS: Ten patients with known or suspected gliomas underwent standard of care surgical resection and/or stereotactic biopsy. FDOPA-PET/MRI was performed prior to surgery, allowing for precise co-registration of PET, MR, and biopsies. The biopsy sites were modeled as 5-mm spheres, and the local FDOPA uptake at each site was determined. Correlations were performed between measures of tumor histopathology, and static and dynamic PET values: standardized uptake values (SUVs), tumor to brain ratios, metabolic tumor volumes, and tracer kinetics at volumes of interest (VOIs) and biopsy sites. RESULTS: Tumor FDOPA-PET uptake was visualized in 8 patients. In 2 patients, tracer uptake was similar to normal brain reference with no histological findings of malignancy. Eight biopsy sites confirmed for glioma had FDOPA uptake without T1 contrast enhancement. The PET parameters were highly correlated only with the cell proliferation marker, Ki-67 (SUVmax: r = 0.985, P = .002). In this study, no statistically significant difference between high-grade and low-grade tumors was demonstrated. The dynamic PET analysis of VOIs and biopsy sites showed decreasing time-activity curves patterns. FDOPA-PET imaging directly influenced patient management. CONCLUSIONS: Simultaneous FDOPA-PET/MRI allowed for more accurate visualization and delineation of gliomas, enabling more appropriate patient management and simplified validation of PET findings with histopathology.

In vivo [18F]-AV-1451 tau-PET imaging in sporadic Creutzfeldt-Jakob disease.

OBJECTIVE: To determine whether specific patterns of [18F]-AV-1451 tau-PET retention are observed in patients with autopsy-proven sporadic Creutzfeldt-Jakob disease (CJD). METHODS: In vivo [18F]-AV-1451 PET neuroimaging was performed in 5 patients with sporadic CJD (median age, 66 years [63-74]), and results were compared to cognitively normal (CN) persons (n = 44; median age, 68 years [63-74]) and to participants with very mild Alzheimer disease (AD) dementia (n = 8; median age, 77 years [63-90]). Autopsy was completed in all patients with CJD, confirming the clinical diagnosis and permitting characterization of AD neuropathologic change (ADNC). RESULTS: All patients with CJD presented with rapidly progressive dementia, typical magnetic resonance brain imaging changes, and elevated CSF total tau (median = 6,519; range = 1,528-13,240 pg/mL). Death occurred within 9 months of symptom onset, with a median 1 month (0.2-3.3) interval from [18F]-AV-1451 PET to autopsy. No unique pattern of [18F]-AV-1451 retention was observed on visual inspection. Summary standardized uptake value ratios in patients with CJD (1.17, 1.08-1.36) were indistinguishable from CN persons (1.14, 0.84-1.54; p = 0.6), and well below those of participants with AD (2.23, 1.60-3.04; p ≤ 0.01). [18F]-AV-1451 retention in patients with CJD and CN persons was similar in brain areas frequently affected in AD and CJD. Neuropathologic analysis confirmed the clinical diagnosis in all patients with CJD. Four patients with CJD also had low-level ADNC (A1B1C0); one patient had intermediate-level ADNC (A2B2C1/2). CONCLUSION: Increased [18F]-AV-1451 retention was not observed in patients with rapidly progressive dementia due to sporadic CJD. The [18F]-AV-1451 PET tracer maintains good specificity for paired helical tau filaments associated with AD dementia.