# Single-shot frequency offset measurement with HASTE using the selective parity approach

## TL;DR

This paper introduces a new MRI technique for measuring frequency offset using a single-shot method that produces accurate and high-quality maps with minimal distortion.

## Contribution

The novel contribution is a single-shot turbo-spin-echo method using selective parity to measure frequency offset rapidly and accurately.

## Key findings

- The new method produced frequency offset maps with no systematic bias or offset compared to a gold-standard technique.
- The method maintained consistent precision and accuracy across a range of evolution times.
- The technique was successfully implemented at 3 Tesla and tested on a human volunteer.

## Abstract

Measurements of frequency offset are commonly required in MRI. The standard method measures the signal phase as a function of evolution time. Here we use a single shot turbo-spin-echo acquisition method to measure frequency offset at a single evolution time. After excitation the transverse magnetisation evolves during the evolution time, and is then repeatedly refocused. The phase is conjugated between alternate echoes. Using partial parallel acquisition techniques we obtain separate odd- and even- echo images. An iterative procedure ensures self-consistency between them. The difference in phase between the two images yields frequency offset maps. The technique was implemented at 3 Tesla and tested on a healthy human volunteer for a range of evolution times between 6 and 42 ms. A standard method using a similar readout train and multiple evolution times was used as a gold-standard measure. In a statistical comparison with the gold standard no evidence for bias or offset was found. There was no systematic variation in precision or accuracy as a function of evolution time. We conclude that the presented approach represents a viable method for the rapid generation of frequency offset maps with a high image quality and minimal distortion.