Practical considerations of gadoxetate disodium contrast in MRI-guided liver SBRT for primary and secondary liver tumors: optimizing image quality and patient throughput.

Abstract

Purpose/objectivesOptimal implementation of gadoxetate disodium injection (GDI) in liver-directed MR-guided online adaptive radiotherapy (MRgART) remains poorly characterized. Herein, we evaluated the impact of GDI on physician-reported imaging metrics and quantitative contouring variability during liver MRgART planning.Materials/methodsPatients were scanned using a 0.35T MRI onboard the MR-guided LINAC. Pre- and post-contrast TRUFI images were captured at multiple timepoints up to 30 minutes (5-10-minute intervals) following GDI. Four radiation oncologists independently scored each tumor on a 5-point scale (1: poor; 5: excellent) evaluating imaging metrics, such as tumor visualization, border delineation, and image degradation from artifacts. Responses were stratified into pre-contrast, "early" post-contrast (1-15 minutes), and "late" post-contrast (20-30 minutes). Physicians then contoured gross tumor volume (GTV) for 6 patients with either optimal or non-optimal image characteristics. Inter- and intra-observer variability was assessed using Sørensen-Dice coefficient (DICE), Hausdorff distance (HD), volume of tumor not treated (VTNT), and volume of healthy liver erroneously treated (VHL). Comparisons were performed using Mann-Whitney U-test or Wilcoxon Signed-Rank test, as applicable.ResultsTwenty-three patients with 37 total liver tumors were treated using MRgART (median 50 Gy; 3-5 fractions). Late post-contrast imaging significantly improved tumor visualization (4.45) compared to early post-contrast (3.73; pConclusionsGDI administration 20-30 minutes prior to MRgART planning significantly enhances both physician-reported image quality and quantitative contouring accuracy. Its use should be considered in MRgART workflows to minimize potential geographic miss and optimize treatment delivery.