# Using PINS pulses to saturate inflow effects on fMRI data at 3 and 7 T

## TL;DR

This paper introduces a method using PINS pulses to reduce inflow effects in fMRI data at 3 and 7 Tesla, improving signal accuracy.

## Contribution

The novel PINS pulse technique saturates magnetization in slice gaps to suppress inflow effects during fMRI.

## Key findings

- PINS pulses effectively saturated magnetization in slice gaps without degrading imaging slice profiles.
- PINS reduced activated voxels by 25% at 3 T and 10% at 7 T, likely due to differences in blood T2.
- PINS outperformed no-gap acquisitions in suppressing through-plane inflow in flow phantom experiments.

## Abstract

To suppress inflow effects by saturating the magnetization within slice gaps.

Power independent of number of slices (PINS) pulses was designed to saturate the magnetization in all slice gaps at once. The PINS saturation module was played before every excitation. The saturation and excitation profiles were validated in simulation and phantom experiments. To demonstrate the efficacy of the method to suppress inflow, experiments were performed using a flow phantom. As an example use‐case, fMRI experiments with and without PINS inflow saturation were performed at 3 T and 7 T.

Simulations and phantom experiments showed that the PINS saturation module successfully saturated the magnetization in the slice gaps without degrading the slice profile of the imaging slices. Flow phantom experiments showed that the PINS saturation module suppresses through‐plane inflow better than no‐gap acquisitions. In vivo fMRI experiments demonstrated that the PINS saturation module can be used to modulate the spin‐echo BOLD signal. At 3 T application of PINS pulses to saturate the magnetization in the slice gaps resulted in approximately 25% fewer activated voxels (PINS‐ON vs. PINS‐OFF). Interestingly, at 7 T the activation patterns remained more similar and only approximately 10% fewer activated voxels were detected. The observed difference between 3 and 7 T may be linked to the relative shortening of the blood T2.

Using PINS pulses, inflow effects from slice gaps were effectively and efficiently saturated. The proposed PINS saturation module can be used to further study the contribution of inflow effects in fMRI data.