DCE‐MRI of the liver with sub‐second temporal resolution using GRASP‐Pro with navi‐stack‐of‐stars sampling

Abstract Respiratory motion‐induced image blurring and artifacts can compromise image quality in dynamic contrast‐enhanced MRI (DCE‐MRI) of the liver. Despite remarkable advances in respiratory motion detection and compensation in past years, these techniques have not yet seen widespread clinical adoption. The accuracy of image‐based motion detection can be especially compromised in the presence of contrast enhancement and/or in situations involving deep and/or irregular breathing patterns. This work proposes a framework that combines GRASP‐Pro (Golden‐angle RAdial Sparse Parallel MRI with imProved performance) MRI with a new radial sampling scheme called navi‐stack‐of‐stars for free‐breathing DCE‐MRI of the liver without the need for explicit respiratory motion compensation. A prototype 3D golden‐angle radial sequence with a navi‐stack‐of‐stars sampling scheme that intermittently acquires a 2D navigator was implemented. Free‐breathing DCE‐MRI of the liver was conducted in 24 subjects at 3T including 17 volunteers and 7 patients. GRASP‐Pro reconstruction was performed with a temporal resolution of 0.34–0.45 s per volume, whereas standard GRASP reconstruction was performed with a temporal resolution of 15 s per volume. Motion compensation was not performed in all image reconstruction tasks. Liver images in different contrast phases from both GRASP and GRASP‐Pro reconstructions were visually scored by two experienced abdominal radiologists for comparison. The nonparametric paired two‐tailed Wilcoxon signed‐rank test was used to compare image quality scores, and the Cohen's kappa coefficient was calculated to evaluate the inter‐reader agreement. GRASP‐Pro MRI with sub‐second temporal resolution consistently received significantly higher image quality scores ( P < 0.05) than standard GRASP MRI throughout all contrast enhancement phases and across all assessment categories. There was a substantial inter‐reader agreement for all assessment categories (ranging from 0.67 to 0.89). The proposed technique using GRASP‐Pro reconstruction with navi‐stack‐of‐stars sampling holds great promise for free‐breathing DCE‐MRI of the liver without respiratory motion compensation.