Spleen stiffness in a healthy pediatric population undergoing liver magnetic resonance elastography.

Abstract

Background: Splenic stiffness is a potential imaging marker of portal hypertension. Normative spleen stiffness values are needed to define diagnostic thresholds.

Objective: To report stiffness measurements of the spleen in healthy children undergoing liver magnetic resonance (MR) elastography across MRI vendors and field strengths.

Materials and methods: This was a post-hoc analysis of data collected under a prospective multicenter cross-sectional study. Volunteers aged 7-17.9 years without a known history of liver or spleen disease were recruited for a research MRI between February 2018 and October 2019. Gradient recalled echo (GRE) or spin-echo-echo-planar imaging (SE-EPI) MR elastography was performed on a total of three vendor platforms and at two field strengths (1.5 T (T) and 3 T) with standard right upper quadrant passive driver placement (frequency of 60 Hz). Two independent reviewers measured spleen stiffness, length, and volume. Descriptive statistics, independent sample t-tests or Mann-Whitney test, and Pearson's or Spearman's correlation were used.

Results: From 101 study volunteers, 72 (34 female) had measurable splenic stiffness. Median age was 12 years (interquartile range [IQR], 9.9-14.9 years). Mean (± SD) spleen stiffness was 4.7 ± 0.9 kPa (IQR, 3.8-5.4 kPa) with 6.1 kPa reflecting the 95th percentile. Strong correlation was observed between reviewers (ICC = 0.89 [95%CI, 0.71-0.93; P < 0.001]). Male volunteers had slightly higher splenic stiffness compared to females: 4.9 ± 0.9 vs. 4.3 ± 0.8 kPa (P = 0.014). There was significant correlation between spleen stiffness and body mass index (r = 0.33 [95%CI, 0.06-0.56; P = 0.024]) but no other measure of patient size (r = 0.15-0.29). No significant difference in spleen stiffness was observed across vendors (P = 0.089) or field strengths (P = 0.236).

Conclusion: MR elastography-based spleen stiffness, measured as part of a liver MR elastography acquisition, is < 6.1 kPa in a healthy pediatric population and does not vary with MRI vendor or field strength.