Feasibility of integrated IMRT technique for craniospinal irradiation in a supine position

Objective: To explore the feasibility and safety of integrated intensity-modulated radiation therapy (IMRT) technology applied in craniospinal irradiation in a supine position. Methods: The patients were fixed in a supine position using thermoplastic mask and vacuum mat. Three isocenters with a fixed interval of 20-25 cm were adopted according to the height of patients. A total of 13 beams with a length of 2-3 cm in the overlapping region were included in the treatment plan. Fixed jaw technique was employed and overall calculation was performed by the inverse optimization method. The γ-passing rate and absolute point dose verification were performed for three isocenters and two overlapping regions. Cone-beam CT (CBCT) images were scanned for three isocenters before treatment. The setup error of each isocenter in the x, y and z directions of the same coordinate system was recorded and overall analysis was conducted. Results: Among 28 patients, the γ-passing rate (%) of three isocenters and two overlapping regions was 99.36%, 99.60%, 99.75%, 94.77% and 95.09%, whereas the absolute point dose verification error was 1.56%, -1.56%, 0.52%, -0.76% and -1.68%, respectively. Twenty-eight patients received 162 groups of IGRT with 486 setup errors from the CBCT images. The average deviation in the x, y and z direction for three isocenters (neck, chest and abdomen) was 0.17 mm, 0.10 mm, 0.02 mm, 0.06 mm, 0.04 mm, 0.46 mm, 0.19 mm, 0.26 mm and 0.41 mm, respectively. Conclusions: The integrated IMRT techniques for craniospinal irradiation in a supine position is feasible and safe, which is worthy of clinical application. (authors)