Abstract
Background : Respiratory motion management with breath hold for patients with hepatobiliary cancers remains 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.
Audio-Visual Biofeedback for Respiratory Motion Management: Comparison of the Reproducibility of Breath-Holding between Visual and Audio Guidance
