RAVE-T2/T1 - Feasibility of a new hybrid MR-sequence for free-breathing abdominal MRI in children and adolescents.

BACKGROUND: The new radial volumetric encoding RAVE-T2/T1 hybrid sequence is a modern three-dimensional sequence with multiparametric approach, which includes T2- and T1-weighted contrasts obtained in identical slice position during one measurement. However, the RAVE-T2/T1 hybrid sequence is not yet being used in clinical routine. PURPOSE: The aim of this study was to evaluate the RAVE-T2/T1 hybrid sequence in a pediatric population with a clinical indication for an abdominal MRI examination to demonstrate that the hybrid imaging may be less challenging to perform on children. MATERIALS AND METHODS: Our retrospective observational study included pediatric patients of all age groups and required for an abdominal MRI examination. Non-contrast standard axial T1 DIXON and non-contrast RAVE-T2/T1 hybrid sequence were obtained at 3 T. MRI studies were analyzed independently by two pediatric radiologists using a 5-point Likert-type scale in five different categories. T1- and T2-weighted sequences were each compared with the RAVE-T2/T1-sequence using a Wilcoxon signed-rank test. RESULTS: The analysis included 15 children (mean age, 11 years and 4 months, 7 girls and 8 boys). The Cohens Kappa of interrater agreement measured 0.62. The T2 weighted part of the RAVE-T2/T1 sequence was significantly better than the standard T2 HASTE sequence in four of five image quality categories: overall image quality (2.2 ± 0.7 vs 1.8 ± 0,7, p = 0.03), respiratory motion artefacts (3.8 ± 0.4 vs 2.0 ± 0.7, p <= 0.01), portal vein clarity (3.3 ± 0.8 vs 2.2 ± 0.7, p <= 0.01), hepatic margin sharpness (2.4 ± 1,0 vs 1.8 ± 0.7, p <= 0.01). The T1 weighted part of the RAVE-T2/T1 sequence was significantly better than the standard T1 DIXON weighted sequence in three of five image quality categories: respiratory motion artefacts (4.0 ± 0.2 vs 3.6 ± 0.8, p = 0.01), portal vein clarity (2.7 ± 0.9 vs 2.1 ± 0.7, p <= 0.01), hepatic margin sharpness (3.2 ± 0.7 vs 2.6 ± 0.9, p <= 0.01). CONCLUSIONS: The RAVE-T2/T1 hybrid sequence is feasible and equal compared to standard T1- and T2-weighted sequences in the assessment of abdominal organs in a pediatric population. Due to non-inferiority to the current standard sequences for abdominal imaging, the RAVE-T2/T1 hybrid sequence is a good alternative for children who cannot be examined in breath-hold technique.

Function of von Willebrand factor in children with diarrhea-associated hemolytic-uremic syndrome (D+ HUS).

Reports on von Willebrand factor (vWF) in hemolytic-uremic syndrome (HUS) are not unequivocal. Because of potential pathogenic implications, we examined the ability of vWF to bind to collagen in vitro, which reflects its function. Plasma vWF antigen (vWF:Ag) and collagen-binding activity (vWF:CBA) were measured by enzyme-linked immunosorbent assay in children with (1) diarrhea-associated (D+) HUS (n = 27), (2) chronic renal insufficiency (CRI) (n = 8), (3) gastroenteritis (GE) not associated with HUS (n = 15), (4) immune thrombocytopenia (ITP) (n = 40) and from controls (n = 35). Structural vWF was evaluated by multimer analysis. Children with D+ HUS had vWF:Ag of 2.53 and vWF:CBA of 1.98 U/mL. The corresponding values for patients with ITP were 1.35 and 1.82 U/mL, with CRI 1.55 and 1.55 U/mL, and with GE 1.68 and 2.10 U/mL; all values were higher than in controls (1.04 and 1.16 U/mL). The mean ratio of vWF:CBA to vWF:Ag ratio in controls was 1.13; only children with HUS had a dysfunctional vWF, as indicated by a low ratio of 0.78; the ratio was elevated in children with ITP (1.36) and GE (1.27) and was normal in those with CRI (1.06). No ultralarge molecular multimers of vWF were detected in any group, including HUS. The very high concentration of plasma vWF:Ag in HUS probably reflects endothelial cell damage or irritation. In contrast to all other groups, only children with HUS had a dysfunctional vWF, caused either by a primary (due to enterohemorrhagic Escherichia coli) or secondary (due to consumption of functionally active vWF) process. This abnormality was not obvious as structural anomaly by multimer analysis.