# In-vivo liver proton density fat fraction quantification at 0.55 T: a pilot study with comparison against 3 T MRI

## TL;DR

This study shows that 0.55T MRI can accurately measure liver fat levels in patients with metabolic liver disease, similar to the more common 3T MRI.

## Contribution

The study demonstrates the feasibility of using low-field 0.55T MRI for liver fat quantification in metabolic liver disease patients.

## Key findings

- 0.55T MRI showed excellent agreement with 3T MRI in phantom tests (R2 > 0.999).
- In vivo PDFF measurements at 0.55T and 3T MRI were highly correlated (r = 0.99).
- 0.55T MRI has potential as a screening and monitoring tool for metabolic dysfunction-associated steatotic liver disease.

## Abstract

Proton density fat fraction (PDFF)— the ratio of unconfounded fat signal to the sum of the unconfounded fat and water signals, is a valuable quantitative imaging biomarker of metabolic associated steatotic liver disease (MASLD) widely applied in clinical practice and clinical trials. PDFF of the liver is commonly measured using 3 T MRI systems. However, low-field systems are increasingly favored due to lower cost, improved safety profile, minimized artifacts around metallic implants, and enhanced patient comfort.

In this pilot study, we used knowledge of standardized and widely used 3 T liver PDFF protocols, and adapted parameters to be appropriate for the 0.55 T MRI. We evaluate a liver fat quantification protocol at 0.55 T compared to a standard clinical 3 T protocol to measure liver fat in patients with MASLD.

Eight adult patients (average age 53.6 ± 13.6 years, 5 females) with ≥ 5% PDFF on 3 T MRI underwent a 0.55 T MRI PDFF protocol within 90 days. To keep the acquisition time to be within a reasonable breath hold duration and with reasonable signal-to-noise ratio (SNR), four echoes were acquired at a lower resolution and fewer number of slices at 0.55 T compared to 3 T which uses a 6-echo multi-echo Dixon volumetric interpolated breath hold examination (VIBE) protocol. PDFF quantification accuracy of the 0.55 T approach was evaluated using a commercial PDFF phantom and in vivo.

In the phantom, there was excellent match (R2 > 0.999) between PDFF estimated by 0.55 T MRI and ground truth. Mean in vivo 3 T MRI-PDFF was 16.5%, compared to 16.3% 0.55 T MRI-PDFF (correlation coefficient r = 0.99). The Bland–Altman analysis showed good agreement of in vivo PDFF measurements across 0.55 T and 3 T estimating a bias or mean difference of − 0.25% and the limits of agreements (LoA) of − 3.98% and 3.48%.

Our data demonstrate that 0.55 T MRI is feasible and comparable to 3 T MRI in quantifying liver PDFF among patients with MASLD.

The online version contains supplementary material available at 10.1007/s10334-025-01277-9.

Evaluation of liver proton density fat fraction is feasible at 0.55T in clinically relevant populations.Liver proton density fat fractions using 0.55T MRI agrees well with measurements obtained from 3T MRI.Liver proton density fat fraction measured by 0.55T MRI shows potential as a screening and monitoring tool for patients with metabolic dysfunction-associated steatotic liver disease.

Evaluation of liver proton density fat fraction is feasible at 0.55T in clinically relevant populations.

Liver proton density fat fractions using 0.55T MRI agrees well with measurements obtained from 3T MRI.

Liver proton density fat fraction measured by 0.55T MRI shows potential as a screening and monitoring tool for patients with metabolic dysfunction-associated steatotic liver disease.

The online version contains supplementary material available at 10.1007/s10334-025-01277-9.