# Three-dimensional motion corrected free-breathing simultaneous multislice-balanced steady state free precession myocardium perfusion imaging

## TL;DR

This paper introduces a new 3D motion correction method for free-breathing heart imaging that improves motion correction and image quality.

## Contribution

The novel contribution is a 3D motion-corrected SMS-bSSFP acquisition using a fast respiratory navigator and inline registration for free-breathing myocardial perfusion.

## Key findings

- SMS-fastNAV reduced residual left ventricle motion compared to SMS-Ref, as shown by higher avDICE and lower avCOM.
- After non-rigid registration, SMS-fastNAV showed improved avDICE and tended to reduce through-plane motion.
- There were no significant differences in subjective image quality between SMS-fastNAV and SMS-Ref.

## Abstract

To develop a 3D motion-corrected simultaneous multislice-balanced steady state free precession (SMS)-bSSFP acquisition to enable free-breathing myocardial perfusion with high spatial resolution and coverage.

A fast diaphragmatic respiratory navigator (fastNAV) module (<15 ms) was implemented into an SMS-bSSFP sequence for prospective slice-tracking. The remaining 2D in-plane motion was corrected using inline image registration. This approach (SMS-fastNAV) was compared to a reference SMS perfusion with 2D in-plane motion correction only (SMS-Ref) in 10 patients at 1.5T. Each subject underwent both perfusion protocols (six slices, resolution: 1.9 × 1.9 mm2) in a random order. The residual motion of the left ventricule (LV) was assessed by measuring the average DICE coefficient of the LV (avDICE) and the average displacement of the LV center of mass location (avCOM). Subjective assessment of image quality was also performed.

SMS-fastNAV led to lower residual LV motion than SMS-Ref before non-rigid image registration as shown by a higher avDICE (0.93±0.02 vs. 0.89±0.04, p<0.002) and decreased avCOM (2.82±0.89 mm vs. 4.23±1.29 mm, p = 0.005). After non-rigid image registration, SMS-fastNAV also led to higher avDICE score (0.95±0.01 vs. 0.94±0.02, p<0.027) and tended to decrease avCOM (0.97±0.21 mm vs. 1.01±0.25 mm, p = 0.23) with respect to SMS-Ref, suggesting a reduction in through-plane motion. There were no statistical significant differences between both approaches in terms of image quality (SMS-fastNAV: 1.79±0.50 vs. SMS-Ref: 2.00±0.59, p = 0.172).

A 3D motion correction strategy was successfully developed for free-breathing SMS-bSSFP perfusion with high spatial coverage and resolution and provides improved motion correction with respect to standard in-plane image registration only.

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