Comparison of diffusion-weighted MRI and [18F]FDG PET/MRI for treatment monitoring in pediatric Hodgkin and non-Hodgkin lymphoma.

OBJECTIVE: To compare tumor therapy response assessments with whole-body diffusion-weighted imaging (WB-DWI) and 18F-fluorodeoxyglucose ([18F]FDG) PET/MRI in pediatric patients with Hodgkin lymphoma and non-Hodgkin lymphoma. MATERIALS AND METHODS: In a retrospective, non-randomized single-center study, we reviewed serial simultaneous WB-DWI and [18F]FDG PET/MRI scans of 45 children and young adults (27 males; mean age, 13 years ± 5 [standard deviation]; age range, 1-21 years) with Hodgkin lymphoma (n = 20) and non-Hodgkin lymphoma (n = 25) between February 2018 and October 2022. We measured minimum tumor apparent diffusion coefficient (ADCmin) and maximum standardized uptake value (SUVmax) of up to six target lesions and assessed therapy response according to Lugano criteria and modified criteria for WB-DWI. We evaluated the agreement between WB-DWI- and [18F]FDG PET/MRI-based response classifications with Gwet's agreement coefficient (AC). RESULTS: After induction chemotherapy, 95% (19 of 20) of patients with Hodgkin lymphoma and 72% (18 of 25) of patients with non-Hodgkin lymphoma showed concordant response in tumor metabolism and proton diffusion. We found a high agreement between treatment response assessments on WB-DWI and [18F]FDG PET/MRI (Gwet's AC = 0.94; 95% confidence interval [CI]: 0.82, 1.00) in patients with Hodgkin lymphoma, and a lower agreement for patients with non-Hodgkin lymphoma (Gwet's AC = 0.66; 95% CI: 0.43, 0.90). After completion of therapy, there was an excellent agreement between WB-DWI and [18F]FDG PET/MRI response assessments (Gwet's AC = 0.97; 95% CI: 0.91, 1). CONCLUSION: Therapy response of Hodgkin lymphoma can be evaluated with either [18F]FDG PET or WB-DWI, whereas patients with non-Hodgkin lymphoma may benefit from a combined approach. CLINICAL RELEVANCE STATEMENT: Hodgkin lymphoma and non-Hodgkin lymphoma exhibit different patterns of tumor response to induction chemotherapy on diffusion-weighted MRI and PET/MRI. KEY POINTS: • Diffusion-weighted imaging has been proposed as an alternative imaging to assess tumor response without ionizing radiation. • After induction therapy, whole-body diffusion-weighted imaging and PET/MRI revealed a higher agreement in patients with Hodgkin lymphoma than in those with non-Hodgkin lymphoma. • At the end of therapy, whole-body diffusion-weighted imaging and PET/MRI revealed an excellent agreement for overall tumor therapy responses for all lymphoma types.

Increased Metabolic Activity of the Thymus and Lymph Nodes in Pediatric Oncology Patients After Coronavirus Disease 2019 Vaccination.

We hypothesized that 18F-FDG PET/MRI would reveal thymus activation in children after coronavirus disease 2019 (COVID-19) vaccination. Methods: We retrospectively analyzed the 18F-FDG PET/MRI scans of 6 children with extrathoracic cancer before and after COVID-19 vaccination. We compared pre- and postvaccination SUVmax, mean apparent diffusion coefficient, and size of the thymus and axillary lymph nodes using a paired t test. Results: All 6 patients showed increased 18F-FDG uptake in the axillary lymph nodes after vaccination (P = 0.03). In addition, these patients demonstrated increased 18F-FDG uptake in the thymus. When compared with baseline, the postvaccination scans of these patients demonstrated an increased mean thymic SUV (P = 0.02), increased thymic size (P = 0.13), and decreased thymic mean apparent diffusion coefficient (P = 0.08). Conclusion: 18F-FDG PET/MRI can reveal thymus activation in addition to local lymph node reactions in children after COVID-19 vaccination.

Tyrosine kinase inhibitor therapy in pediatric sarcoma: Prognostic implications of pulmonary metastatic cavitation.

PURPOSES: This study aims to ascertain the prevalence of cavitations in pulmonary metastases among pediatric and young adult patients with sarcoma undergoing tyrosine kinase inhibitor (TKI) therapy, and assess whether cavitation can predict clinical response and survival outcomes. METHODS: In a single-center retrospective analysis, we examined chest computed tomography (CT) scans of 17 patients (median age 16 years; age range: 4-25 years) with histopathologically confirmed bone (n = 10) or soft tissue (n = 7) sarcoma who underwent TKI treatment for lung metastases. The interval between TKI initiation and the onset of lung nodule cavitation and tumor regrowth were assessed. The combination of all imaging studies and clinical data served as the reference standard for clinical responses. Progression-free survival (PFS) was compared between patients with cavitating and solid nodules using Kaplan-Meier survival analysis and log-rank test. RESULTS: Five out of 17 patients (29%) exhibited cavitation of pulmonary nodules during TKI therapy. The median time from TKI initiation to the first observed cavitation was 79 days (range: 46-261 days). At the time of cavitation, all patients demonstrated stable disease. When the cavities began to fill with solid tumor, 60% (3/5) of patients exhibited progression in other pulmonary nodules. The median PFS for patients with cavitated pulmonary nodules after TKI treatment (6.7 months) was significantly longer compared to patients without cavitated nodules (3.8 months; log-rank p-value = .03). CONCLUSIONS: Cavitation of metastatic pulmonary nodules in sarcoma patients undergoing TKI treatment is indicative of non-progressive disease, and significantly correlates with PFS.

Measurement of Tumor T2* Relaxation Times after Iron Oxide Nanoparticle Administration.

T2* relaxometry is one of the established methods to measure the effect of superparamagnetic iron oxide nanoparticles on tumor tissues with magnetic resonance imaging (MRI). Iron oxide nanoparticles shorten the T1, T2, and T2* relaxation times of tumors. While the T1 effect is variable based on the size and composition of the nanoparticles, the T2 and T2* effects are usually predominant, and T2* measurements are the most time-efficient in a clinical context. Here, we present our approach to measuring tumor T2* relaxation times, using multi-echo gradient echo sequences, external software, and a standardized protocol for creating a T2* map with scanner-independent software. This facilitates the comparison of imaging data from different clinical scanners, different vendors, and co-clinical research work (i.e., tumor T2* data obtained in mouse models and patients). Once the software is installed, the T2 Fit Map plugin needs to be installed from the plugin manager. This protocol provides step-by-step procedural details, from importing the multi-echo gradient echo sequences into the software, to creating color-coded T2* maps and measuring tumor T2* relaxation times. The protocol can be applied to solid tumors in any body part and has been validated based on preclinical imaging data and clinical data in patients. This could facilitate tumor T2* measurements for multi-center clinical trials and improve the standardization and reproducibility of tumor T2* measurements in co-clinical and multi-center data analyses.

A comparison of the success rate of pneumatic reduction in intussusception between general anesthesia and deep sedation: a randomized controlled trial.

PURPOSE: This study was aimed to compare the success rate between patients who underwent general anesthesia and deep sedation. METHODS: Patients who were diagnosed with intussusception and had no contraindications would receive non-operative treatment first by undergoing pneumatic reduction. The patients were then split in to two groups: one group underwent general anesthesia (GA group), while the other underwent deep sedation (SD group). This study was a randomized controlled trial which compared success rate between two groups. RESULTS: A total of 49 episodes diagnosed with intussusception were random into 25 episodes in GA group and 24 episodes in SD group. There was no significant difference in baseline characteristic between the two groups. The success rates of GA group and SD group were equally 88.0% (p = 1.00). Sub-analysis of the success rate was lower in the patients with high-risk score for failed reduction. (Chiang Mai University Intussusception (CMUI) failed score in success VS failed = 6.9 ± 3.2 vs. 10.3 ± 3.0 p = 0.017). CONCLUSION: General anesthesia and deep sedation offered similar success rates. In cases of high risk of failure, general anesthesia should be considered to accommodate the switch to surgical management in the same setting if the non-operative approach fails. The appropriate treatment and sedative protocol also increase the success of reduction.

Ferumoxytol-Enhanced MRI in Children and Young Adults: State of the Art.

Ferumoxytol is an ultrasmall iron oxide nanoparticle that was originally approved by the FDA in 2009 for IV treatment of iron deficiency in adults with chronic kidney disease. Subsequently, its off-label use as an MRI contrast agent increased in clinical practice, particularly in pediatric patients in North America. Unlike conventional MRI contrast agents that are based on the rare earth metal gadolinium (gadolinium-based contrast agents), ferumoxytol is biodegradable and carries no potential risk of nephrogenic systemic fibrosis. At FDA-approved doses, ferumoxytol shows no long-term tissue retention in patients with intact iron metabolism. Ferumoxytol provides unique MRI properties, including long-lasting vascular retention (facilitating high-quality vascular imaging) and retention in reticuloendothelial system tissues, thereby supporting a variety of applications beyond those possible with gadolinium-based contrast agents (GBCAs). This Clinical Perspective describes clinical and early translational applications of ferumoxytol-enhanced MRI in children and young adults through off-label use in a variety of settings, including vascular, cardiac, and cancer imaging, drawing on the institutional experience of the authors. In addition, we describe current advances in pre-clinical and clinical research using ferumoxytol in cellular and molecular imaging as well as the use of ferumoxytol as a novel potential cancer therapeutic agent.

Diffuse neonatal hemangiomatosis with a single atypical cutaneous hemangioma.

Diffuse neonatal hemangiomatosis (DNH) is an extremely rare but deadly neonatal condition which presents as multiple cutaneous hemangiomas and hemangiomas in 3 or more visceral organs. DNH is usually suspected when multiple hemangiomas are found on the skin of the baby. We hereby present an interesting case in a newborn whose diagnosis was made from multiple intracranial, hepatic, and intramuscular hemangiomas, but with a single and unusual cutaneous manifestation over the right ankle. The patient was asymptomatic at the time of diagnosis. Due to the solitary nature of skin lesion, this report might contribute to a redefining of the term DNH.

Scurvy mimicking as systemic lupus erythematosus.

Scurvy is a disease caused by chronic vitamin C deficiency. The greater prevalence was found in the paediatric population with neurodevelopmental disorders such as autism spectrum disorders due to their restricted dietary intake. Our case reported a child with autism who presented with arthralgia and anaemia. Systemic lupus erythematosus was the first diagnostic impression, resulting in over investigation and delayed diagnosis of vitamin C deficiency. After the child was treated with ascorbic acid, the child's symptoms resolved. This case highlighted the importance of developmental and nutritional history taking in the paediatric population. Furthermore, parents and physicians should be concerned about nutritional status, especially in children with restrictive dietary intake.