Prospective study of quantitative liver MRI in cystic fibrosis: feasibility and comparison to PUSH cohort ultrasound

BACKGROUND

Pediatric radiologists can identify a liver ultrasound (US) pattern predictive of progression to advanced liver disease. However, reliably discriminating these US patterns remains difficult. Quantitative magnetic resonance imaging (MRI) may provide an objective measure of liver disease in cystic fibrosis (CF).

OBJECTIVE

The purpose of this study was to determine if quantitative MRI, including MR elastography, is feasible in children with CF and to determine how quantitative MRI-derived metrics compared to a research US.

MATERIALS AND METHODS

A prospective, multi-institutional trial was performed evaluating CF participants who underwent a standardized MRI. At central review, liver stiffness, fat fraction, liver volume, and spleen volume were obtained. Participants whose MRI was performed within 1 year of US were classified by US pattern as normal, homogeneous hyperechoic, heterogeneous, or nodular. Each MRI measure was compared among US grade groups using the Kruskal-Wallis test.

RESULTS

Ninety-three participants (51 females [54.8%]; mean 15.6 years [range 8.1-21.7 years]) underwent MRI. MR elastography was feasible in 87 participants (93.5%). Fifty-eight participants had an US within 1 year of MRI. In these participants, a nodular liver had significantly higher stiffness (P<0.01) than normal or homogeneous hyperechoic livers. Participants with a homogeneous hyperechoic liver had a higher fat fraction (P<0.005) than others.

CONCLUSION

MR elastography is feasible in children with CF. Participants with a nodular pattern had higher liver stiffness supporting the US determination of advanced liver disease. Participants with a homogeneous hyperechoic pattern had higher fat fractions supporting the diagnosis of steatosis.

Association Between Transient Elastography and Controlled Attenuated Parameter and Liver Ultrasound in Children With Cystic Fibrosis

Methods to identify children with cystic fibrosis (CF) at risk for development of advanced liver disease are lacking. We aim to determine the association between liver stiffness measurement (LSM) by vibration-controlled transient elastography (VCTE) with research ultrasound (US) patterns and conventional hepatic markers as a potential means to follow liver disease progression in children with CF. ELASTIC (Longitudinal Assessment of Transient Elastography in CF) is a nested cohort of 141 patients, ages 7-21, enrolled in the Prediction by US of Risk of Hepatic Cirrhosis in CF (PUSH) Study. We studied the association between LSM with research-grade US patterns (normal [NL], heterogeneous [HTG], homogeneous [HMG], or nodular [NOD]) and conventional hepatic markers. In a subgroup (n = 79), the association between controlled attenuation parameter (CAP) and US pattern was explored. Among 133 subjects undergoing VCTE, NOD participants (n = 26) had a significantly higher median (interquartile range) LSM of 9.1 kPa (6.3, 15.8) versus NL (n = 72, 5.1 kPa [4.2, 7.0]; P < 0.0001), HMG (n = 17, 5.9 kPa [5.2, 7.8]; P = 0.0013), and HTG (n = 18, 6.1 kPa [4.7, 7.0]; P = 0.0008) participants. HMG participants (n = 14) had a significantly higher mean CAP (SD) (270.5 dB/m [61.1]) compared with NL (n = 40, 218.8 dB/m [46.5]; P = 0.0027), HTG (n = 10, 218.1 dB/m [60.7]; P = 0.044), and NOD (n = 15, 222.7 dB/m [56.4]; P = 0.041) participants. LSM had a negative correlation with platelet count (r_s =  - 0.28, P = 0.0071) and positive correlation with aspartate aminotransferase-to-platelet ratio index (r_s = 0.38, P = 0.0002), Fibrosis-4 index (r_s = 0.36, P = 0.0007), gamma-glutamyltransferase (GGT; r_s = 0.35, P = 0.0017), GGT-to-platelet ratio (r_s = 0.35, P = 0.003), and US spleen size z-score (r_s = 0.27, P = 0.0073). Conclusion: VCTE is associated with US patterns and conventional markers in patients with liver disease with CF.