Image registration and target volume margins in cone-beam computed tomography-guided intensity-modulated radiotherapy for prostate cancer / 中华放射肿瘤学杂志

ABSTRACT

Objective To analyze the data from intensity-modulated radiotherapy ( IMRT) for prostate cancer guided by kilovoltage cone-beam computed tomography (CBCT), and to provide a clinical basis for selecting the optimal image registration method and reasonable target volume margins.Methods A total of 16 patients with prostate cancer who received radical IMRT were enrolled, and CBCT for online position verification was performed 214 times.The images were obtained after conventional skin marking and laser alignment, and automatic registration, bone registration, soft tissue registration, and manual registration were performed for CBCT images and planned CT images.The differences between these four registration methods were evaluated, and the margins for extending clinical target volume into planning target volume (PTV) were calculated.Results The setup errors in left-right, anterior-posterior, and cranial-caudal directions for automatic registration, bone registration, soft tissue registration, and manual registration were-0.6±2.8 mm/-0.6±4.5 mm/-0.6±3.8 mm,-0.7±2.7 mm/-0.9±4.5 mm/-0.8±4.1 mm,-0.8± 2.6 mm/-0.3±4.4 mm/-1.1±4.0 mm, and-0.6±2.9 mm/-0.7±5.1 mm/-0.9±3.9 mm, respectively. There were no significant differences between the four registration methods.The margins for extension in the left-right, anterior-posterior, and cranial-caudal directions were calculated as 4.7 mm, 5.2 mm, and 6.5 mm, respectively.Conclusions With a comprehensive consideration of various factors, a default setting of automatic registration and manual fine adjustment is appropriate for CBCT-guided radiotherapy for prostate cancer.The margins for extension in the left-right, anterior-posterior, and cranial-caudal directions are 4.7 mm, 5.2 mm, and 6.5 mm, respectively.