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

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.