# Radial Hadamard-encoded 19F-MRI

## TL;DR

This paper introduces a new 19F-MRI method using Hadamard encoding to reduce chemical shift artifacts and improve imaging of the inflammation tracer PFOB in vivo.

## Contribution

A novel radial Hadamard-encoded 19F-MRI technique is proposed to suppress chemical shift artifacts and enhance PFOB signal quality.

## Key findings

- HE effectively suppressed chemical shift artifacts in PFOB 19F-MRI.
- An SNR > 100 was achieved in the spleen 2 days after PFOB injection.
- The PFOB signal decreased by 30% 7 days post-injection.

## Abstract

Developing a 19F imaging method to acquire images of the molecular inflammation tracer perfluorooctyl bromide (PFOB) without chemical shift artifacts.

PFOB is a molecular tracer that can be used to track the response of myeloid cells. However, imaging of PFOB with 19F-MRI is challenging due to its complex spectrum which leads to unwanted chemical shift artifacts. Spectral HE allows for separate reconstructions of each peak of the PFOB spectrum, which was combined into a single image after resonance shift correction. In this work, a Hadamard-encoded (HE) radial 3D UTE sequence was tested in phantoms and in vivo in a pig, measuring the 19F signal in the spleen at different times after injection.

Chemical shift artifacts were effectively suppressed with HE, and an SNR > 100 was observed for the 19F signal in the spleen 2 days after injection. The signal decreased over time, and 7 days after injection it was reduced by 30%.

Chemical shift artifact correction using HE allowed for in vivo 19F PFOB imaging of labeled monocytes with a high SNR. Compared to spectrally selective excitation, HE increased the PFOB 19F-MRI signal by 10%, and the simple HE-algorithm could be directly integrated into the image reconstruction of the MRI system.