K‐ CC ‐ MoCo : A Fast k ‐Space‐Based Respiratory Motion Correction for Highly Accelerated First‐Pass Perfusion Cardiovascular MR

PURPOSE: First-pass perfusion cardiovascular MR (FPP-CMR) enables the non-invasive diagnosis of microcirculation and coronary artery disease. In free-breathing FPP-CMR, motion correction is usually performed in the image domain, requiring an initial reconstruction. This fact hinders its use in model-based and deep learning reconstructions, which present remarkable performance in obtaining high-quality images from highly accelerated acquisitions. We address this challenge by estimating and correcting respiratory motion in free-breathing FPP-CMR directly in k-space. METHODS: We propose K-CC-MoCo, an inter-frame rigid motion correction approach formulated exclusively in k-space that handles dynamic contrast through a specifically targeted design of the normalized cross-correlation (CC) objective function to deal with the dynamic contrast. In addition, an ROI-based coil-compression approach was employed to focus the optimization on the heart region. The proposed method was compared to state-of-the-art image-based registration using a digital phantom and real free-breathing acquisitions with different accelerations. RESULTS: The proposed k-space-based method is approximately 2× faster and can correct respiratory motion even at high acceleration factors (up to 50×), where the image-based method fails due to severe undersampling artifacts. Notably, after K-CC-MoCo, the time-averaged images are visibly less blurred. Quantitative metrics (SSIM, etc.) support this conclusion. CONCLUSION: K-CC-MoCo outperforms image-based correction in free-breathing FPP-CMR acquisitions accelerated up to 50×. Respiratory motion is estimated and corrected in k-space, enabling its use for model-based and/or deep learning reconstructions from highly accelerated scans.