Impact of breath-hold level on positional error aligned by stent/lipiodol in hepatobiliary radiotherapy with breath-hold respiratory control.

Background: Respiratory motion management with breath hold for patients with hepatobiliary cancers remain a challenge in the precise positioning for radiotherapy. We compared different image-guided alignment markers for estimating positional errors, and investigated the factors associated with positional errors under breath-hold control. Methods: Spirometric motion management system (SDX) for breath holds was used in 44 patients with hepatobiliary tumor. Among them, 28 patients had a stent or embolized materials (lipiodol) as alignment markers. Cone-beam computed tomography (CBCT) and kV-orthogonal images were compared for accuracy between different alignment references. Breath-hold level (BHL) was practiced, and BHL variation (ΔBHL) was defined as the standard deviation in differences between actual BHLs and baseline BHL. Mean BHL, ΔBHL, and body-related factors were analyzed for the association with positional errors. Results: Using the reference CBCT, the correlations of positional errors were significantly higher in those with stent/lipiodol than when the vertebral bone was used for alignment in three dimensions. Patients with mean BHL > 1.4 L were significantly taller (167.6 cm vs. 161.6 cm, p = 0.03) and heavier (67.1 kg vs. 57.4 kg, p = 0.02), and had different positional error in the craniocaudal direction (- 0.26 cm [caudally] vs. + 0.09 cm [cranially], p = 0.01) than those with mean BHL < 1.4 L. Positional errors were similar for patients with ΔBHL< 0.03 L and > 0.03 L. Conclusion: Under rigorous breath-hold respiratory control, BHL correlated with body weight and height. With more accurate alignment reference by stent/lipiodol, actual BHL but not breath-hold variation was associated with craniocaudal positional errors. ? 2020 The Author(s).