Longitudinal evaluation of pediatric and young adult metabolic dysfunction-associated steatotic liver disease defined by MR elastography.

OBJECTIVES: To inform clinical monitoring of children and young adults with metabolic dysfunction-associated steatotic liver disease (MASLD) by characterizing the real-world natural history of MASLD and identifying baseline predictors of liver disease progression. MATERIALS AND METHODS: This retrospective study included consecutive patients ages < 23 years with MASLD who underwent serial MR elastography (MRE) and/or MR fat fraction (FF) examinations between 09/2009 and 11/2022. Outcomes of MASLD were defined based on maximum ratio values. A relative change ≥ 19% in liver stiffness measures (LSM) and an absolute change ≥ 5% for liver FF were considered clinically meaningful. Random intercept models characterized the yearly rate of change in LSM (kilopascals per year) and FF (percentage per year). RESULTS: One hundred twenty-one patients (87 males, mean age at baseline: 12 ± 3 [SD] years) underwent 297 MRE examinations. The mean interval between the first and last MRE was 34 (± 24) months (range: 1-120 months). Among the 114 patients with serial LSM, 33% (38/114) showed progression, 46% (53/114) remained stable, and 21% (23/114) showed regression. Among the 88 patients with serial FF measures, 57% (50/88) showed progression, 2% (2/88) remained stable, and 41% (36/88) showed regression. LSM progression was associated with Hispanic ethnicity, baseline BMI-for-age percentile, baseline mean liver FF, and GGT changes over time. Predictors for liver FF progression included ALT, AST, GGT, and LDL. CONCLUSION: In a real-world sample of children and young adults with MASLD who underwent serial liver MRI, a minority of patients demonstrated improvements in liver stiffness or FF over time. KEY POINTS: Question In children, there is scarce data regarding the natural history of MASLD. Findings In this retrospective study, most children and young adults with MASLD had either unchanged or worsening liver stiffness (n = 91/114, 79%) and liver fat (n = 52/88, 59%). Clinical relevance Our findings emphasize the need for optimized care in pediatric MASLD. The identified risk factors for the progression of liver fat and stiffness may help to identify children who require interventions beyond changes in lifestyle.

Reduced count pediatric whole-body 18F-FDG PET imaging reconstruction with a Bayesian penalized likelihood algorithm.

BACKGROUND: Advanced positron emission tomography (PET) image reconstruction methods promise to allow optimized PET/CT protocols with improved image quality, decreased administered activity and/or acquisition times. OBJECTIVE: To evaluate the impact of reducing counts (simulating reduced acquisition time) in block sequential regularized expectation maximization (BSREM) reconstructed pediatric whole-body 18F-fluorodeoxyglucose (FDG) PET images, and to compare BSERM with ordered-subset expectation maximization (OSEM) reconstructed reduced-count images. MATERIALS AND METHODS: Twenty children (16 male) underwent clinical whole-body 18F-FDG PET/CT examinations using a 25-cm axial field-of-view (FOV) digital PET/CT system at 90 s per bed (s/bed) with BSREM reconstruction (ß=700). Reduced count simulations with varied BSREM ß levels were generated from list-mode data: 60 s/bed, ß=800; 50 s/bed, ß=900; 40 s/bed, ß=1000; and 30 s/bed, ß=1300. In addition, a single OSEM reconstruction was created at 60 s/bed based on prior literature. Qualitative (Likert scores) and quantitative (standardized uptake value [SUV]) analyses were performed to evaluate image quality and quantitation across simulated reconstructions. RESULTS: The mean patient age was 9.0 ± 5.5 (SD) years, mean weight was 38.5 ± 24.5 kg, and mean administered 18F-FDG activity was 4.5 ± 0.7 (SD) MBq/kg. Between BSREM reconstructions, no qualitative measure showed a significant difference versus the 90 s/bed ß=700 standard (all P>0.05). SUVmax values for lesions were significantly lower from 90 s/bed, ß=700 only at a simulated acquisition time of 30 s/bed, ß=1300 (P=0.001). In a side-by-side comparison of BSREM versus OSEM reconstructions, 40 s/bed, ß=1000 images were generally preferred over 60 s/bed TOF OSEM images. CONCLUSION: In children who undergo whole-body 18F-FDG PET/CT on a 25-cm FOV digital PET/CT scanner, reductions in acquisition time or, by corollary, administered radiopharmaceutical activity of >50% from a clinical standard of 90 s/bed may be possible while maintaining diagnostic quality when a BSREM reconstruction algorithm is used.

Incidental Thalamic Lesions Identified on Brain MRI in Pediatric and Young Adult Patients: Imaging Features and Natural History.

BACKGROUND AND PURPOSE: Nonspecific, localized thalamic signal abnormalities of uncertain significance are occasionally found on pediatric brain MR imaging. The goal of this study is to describe the MR imaging appearance and natural history of these lesions in children and young adults. MATERIALS AND METHODS: This retrospective study evaluated clinically acquired brain MR imaging examinations obtained from February 1995 to March 2022 at a large, tertiary care pediatric hospital. Examinations with non-mass-like and nonenhancing thalamic lesions were identified based on term search of MR imaging reports. A total of 221 patients formed the initial group for imaging assessment. Additional exclusions during imaging review resulted in 171 patients. Imaging appearance and size changes were assessed at baseline and at follow-up examinations. RESULTS: A total of 171 patients (102 male) at a median age of 11 years (range: 1-23 years), 568 MR imaging examinations, and 180 thalamic lesions were included. Median time from baseline to the last follow-up MR imaging was 542 days (range: 46-5730 days). No lesion enhanced at any time point. On imaging follow-up, 11% of lesions (18/161) became smaller, 10% (16/161) resolved, 73% (118/161) remained stable, and 6% (9/161) increased in size at some point during evaluation. Median time interval from baseline to enlargement was 430 days (range: 136-1074 days). CONCLUSIONS: Most incidental, non-mass-like thalamic signal abnormalities were stable, decreased in size, or resolved on follow-up imaging and are likely of no clinical significance. Surveillance strategies with longer follow-up intervals may be adequate in the management of such findings.

Prospective characterization of intestinal MRI intravoxel incoherent motion in pediatric and young adult patients with newly diagnosed small bowel Crohn's disease.

BACKGROUND: MRI diffusion-weighted imaging (DWI) is commonly used in MR enterography protocols for assessment of intestinal inflammation in patients with Crohn's disease. The intravoxel incoherent motion (IVIM) approach to DWI has been proposed as a more objective approach, providing quantitative parameters that reflect water diffusivity (D), blood flow (D*), and perfusion fraction (f). PURPOSE: We aimed to determine if DWI-IVIM metrics from the terminal ileum in patients with newly diagnosed Crohn's disease differ from healthy participants and change in response to biologic medical therapy. METHODS: In this prospective case-control study, 20 consecutive pediatric patients (mean age = 14 years ± 2 [SD]; eight females) with newly diagnosed ileal Crohn's disease and 15 pediatric healthy participants (mean age = 18 years ± 4 [SD]; eight females) underwent research MRI examinations of the small bowel between 12/2018 and 10/2021. Participants with Crohn's disease underwent MR studies at baseline, 6 weeks, and 6 months following initiation of anti-TNF-alpha therapy, whereas control participants underwent one research MRI examination. The MRI protocol included a DWI-IVIM sequence with nine b-values and the IVIM parameters (D, D*, and f) were extracted. Unpaired t-tests and mixed-effects models were used for analyses. RESULTS: Mean IVIM D (P < 0.001), D* (P = 0.004), and f (P = 0.001) metrics were lower for Crohn's patients at the time of diagnosis compared to healthy participants. Mean IVIM f value increased over time in response to medical therapy (mean f at baseline, 22% ± 6%; 6 weeks, 25% ± 7%; 6 months, 29% ± 10%; P = 0.016). Mean IVIM D* value increased over time in response to treatment (mean D* at baseline, 10.9 ± 3.0 × 10-3 mm2/s; 6 weeks, 11.8 ± 2.8 × 10-3 mm2/s; 6 months, 13.3 ± 3.3 × 10-3 mm2/s; P = 0.047), while there was no significant change in mean IVIM D value (P = 0.10). CONCLUSION: MRI DWI-IVIM metrics in patients with ileal Crohn's disease change over time in response to biological therapy and help discriminate these patients from healthy participants.