WE‐G‐18C‐06: Is Diaphragm Motion a Good Surrogate for Liver Tumor Motion?

Abstract

Purpose:To investigate whether diaphragm motion is a good surrogate for liver tumor motion by comparing their motion trajectories obtained from cine‐MRI.Methods:Fourteen patients with hepatocellular carcinoma (10/14) or liver metastases (4/14) undergoing radiation therapy were included in this study. All patients underwent single‐slice 2D cine‐MRI simulations across the center of the tumor in three orthogonal planes. Tumor and diaphragm motion trajectories in the superior‐inferior (SI), anteriorposterior (AP), and medial‐lateral (ML) directions were obtained using the normalized cross‐correlation based tracking technique. Agreement between tumor and diaphragm motions was assessed by calculating the phase difference percentage (PDP), intra‐class correlation coefficient (ICC), Bland‐Altman analysis (Diffs) and paired t‐test. The distance (D) between tumor and tracked diaphragm area was analyzed to understand its impact on the correlation between tumor and diaphragm motions.Results:Of all patients, the means (±standard deviations) of PDP were 7.1 (±1.1)%, 4.5 (±0.5)% and 17.5 (±4.5)% in the SI, AP and ML directions, respectively. The means of ICC were 0.98 (±0.02), 0.97 (±0.02), and 0.08 (±0.06) in the SI, AP and ML directions, respectively. The Diffs were 2.8 (±1.4) mm, 2.4 (±1.1) mm, and 2.2 (±0.5) mm in the SI, AP and ML directions, respectively. The p‐values derived from the paired t‐test were < 0.02 in SI and AP directions, whereas were > 0.58 in ML direction primarily due to the small motion in ML direction. Tumor and diaphragmatic motion had high concordance when the distance between the tumor and tracked diaphragm areas was small.Conclusion:Preliminary results showed that liver tumor motion had good correlations with diaphragm motion in the SI and AP directions, indicating diaphragm motion in the SI and AP directions could potentially be a reliable surrogate for liver tumor motion.NIH (1R21CA165384‐01A1), Golfers Against Cancer (GAC) Foundation, The China Scholarship Council (CSC)