This study will validate recently developed Magnetic Resonance Imaging (MRI) and Ultrasound (US) based methods for liver fat quantification in children with obesity and healthy range of body mass index (BMI).

The severity of the obesity epidemic in the U.S., particularly in Wisconsin, is alarming, with overall overweight or obesity rates of 35% in children. [Fryar 2020,] Obesity is a major risk factor for several comorbidities, one of the most common being non-alcoholic fatty liver disease (NAFLD, also denoted steatotic liver disease). The inflammatory state known as non-alcoholic steatohepatitis (NASH) may lead to fibrosis and, if left untreated, can lead to cirrhosis, liver failure, and cancer. For these reasons, there is enormous interest in effective interventions for weight loss and reversing NAFLD. A central challenge in the development of new interventions is the need for accurate and precise biomarkers to evaluate hepatic steatosis in children.

This pilot study focuses on demonstrating the feasibility of MRI and US based liver fat quantification in children and addresses technical challenges that may limit the performance of the proposed techniques in the population of interest through the following aims:

• Aim 1: Determine the bias and precision (repeatability) of emerging free-breathing MRI-based liver fat quantification in children with obesity and controls using current breath-held methods as a reference.
• Aim 2: Determine the precision (repeatability and reproducibility) of US-based biomarkers of liver steatosis with a focus on the impact of body wall thickness on the precision of the biomarkers.

Inclusion Criteria:

1. Age: 10 - 14years old
2. BMI: Case subjects: BMI>95th percentile for age and sex Healthy BMI volunteers: 5th ≤ BMI < 85th percentile for age and sex

Exclusion Criteria:

1. Children with contraindications to MRI.
2. Children who did not fast (verbally confirmed by children or guardian)
3. Pregnant