Hepatic shear wave elastography in children under free-breathing and breath-hold conditions

OBJECTIVES: To compare hepatic 2D shear wave elastography (2D SWE) in children between free-breathing and breath-hold conditions, in terms of measurement agreement and time expenditure.

METHODS: A cohort of 57 children (12.7±4.3 years) who underwent standardized 2D SWE between May and October 2015 were retrospectively evaluated. Liver elastograms were obtained under free-breathing and breath-hold conditions and time expenditure was measured. Median stiffness, interquartile range (IQR), and IQR/median ratio were calculated based on 12, six, and three elastograms. Results were compared using Pearson correlation coefficient, intraclass correlation coefficient (ICC), Bland-Altman analysis, and Student's t.

RESULTS: Median liver stiffness under free-breathing and breath-hold conditions correlated strongly (7.22±4.5kPa vs. 7.21±4.11kPa; r=0.97, P<0.001). Time to acquire 12 elastograms with free-breathing was lower than that with breath-holding (79.3±32.5sec vs. 143.7±51.8sec, P<0.001). Results for median liver stiffness based of 12, six, and three elastograms demonstrated very high agreement for free-breathing (ICC 0.993) and for breath-hold conditions (ICC 0.994).

CONCLUSIONS: Hepatic 2D SWE performed with free-breathing yields results similar to the breath-hold condition. With a substantially lower time requirement, which can be further reduced by lowering the number of elastograms, the free-breathing technique may be suitable for infants and less cooperative children not capable of breath-holding.

KEY POINTS: • Hepatic 2D SWE performed with free-breathing yields results similar to breath-hold condition. • Benefit of the free-breathing approach is the substantially lower time requirement. • Lowering the number of elastograms can further reduce time expenditure. • Free-breathing 2D SWE is suitable in children with suspected liver disease.