3078 - Optimizing Image Quality and Workflow with Gadoxetate Disodium Contrast in MRI-Guided Stereotactic Body Radiotherapy for Liver Metastases

05:00pm - 06:00pm PT

Hall F

Screen: 16

POSTER

Presenter(s)

Ari Kassardjian, MD - City of Hope Comprehensive Cancer Center, Duarte, CA

A. Kassardjian¹, B. Maraghechi², C. Shi², H. Ai², E. Grant², A. L. Schwer², J. Weng², C. J. Ladbury^1,2, Y. Liu¹, H. M. McGee¹, Y. J. Chen¹, A. Amini¹, A. Liu¹, T. M. Williams¹, and P. Lee²; ¹Department of Radiation Oncology, City of Hope National Medical Center, Duarte, CA, ²Department of Radiation Oncology, Orange County Lennar Foundation Cancer Hospital, Irvine, CA

Purpose/Objective(s):

Visualization of metastatic tumors in the liver is important for accurate delineation and tracking during magnetic resonance stereotactic body radiation therapy (MR-SBRT). Contrast agents, in conjunction with MR image-guided online-adaptive radiation therapy (MRgART), can enhance treatment delivery. Herein, we investigated the effect of gadoxetate disodium injection (GDI) on physician-reported imaging metrics during MRgART.

Materials/Methods:

Patients were scanned using a 0.35T MRI onboard the MR-guided LINAC. Pre- and post-contrast TRUFI images were captured up to 30 minutes (5–10-min intervals) following GDI during MRgART planning of liver SBRT to visually identify the optimal contrast-to-noise enhancement of the images. Four radiation oncologists independently scored each tumor pre-contrast and at various timepoints post-contrast on a rubric with five questions on a scale of 1 (worst) to 5 (best). Blinded to the timepoint, each physician scored imaging metrics, such as visualizing the tumor, delineating its borders, and presence of artifact. Responses were stratified into three groups: pre-contrast, “early” post-contrast (1 to 15 minutes), and “late” post-contrast (20 to 30 minutes). Scores are reported as mean and 95% confidence interval (CI). Comparisons between groups were performed using the Mann-Whitney U-test.

Results:

During 2024, 23 patients with 37 liver metastases were treated using MRgART with SBRT (median 50 Gy [range 40-54] in 3-5 fractions). Median age was 66 [IQR 55-74.5] years, 69.6% were female, 47.8% were Non-Hispanic White, 30.4% Hispanic or Latino, and 21.7% Asian. Primary disease sites included hepatobiliary (34.8%), colorectal (21.7%), and breast (17.4%). Physicians scored 31 pre-contrast, 69 early post-contrast (1-15 minutes), and 59 late post-contrast (20-30 minutes) scans. Late post-contrast injection significantly enhanced tumor visualization (mean 4.45 [95% CI: 4.33 to 4.57]) compared to early post-contrast (3.73 [3.57 to 3.89]; p<0.001) and pre-contrast (3.25 [2.98 to 3.52]; p<0.001). Tumor visualization early post-contrast remained superior compared to pre-contrast (p=0.004). Late post-contrast significantly improved tumor delineation (4.4 [4.25 to 4.50]) compared to early post-contrast (3.58 [3.41 to 3.74]; p<0.001) and pre-contrast (3.06 [2.81 to 3.31]; p<0.001). Artifact was similar between late post-contrast (4.82 [4.75 to 4.89]) and early post-contrast (4.74 [4.65 to 4.82]; p=0.154) but significantly reduced compared to pre-contrast (4.52 [4.35 to 4.70]; p=0.002).

Conclusion:

Establishing optimal GDI uptake time can improve treatment planning, tumor tracking, and adaptive re-contouring during daily online MRgART. Effective use of GDI for MRgART liver directed SBRT improves the quality of imaging during treatment planning and delivery, thus optimizing treatment using ablative doses of SBRT.