A simple approach of three-isocenter IMRT planning for craniospinal irradiation.

Purpose: To develop a new IMRT technique to simplify the process and improve efficiency in radiotherapy treatment planning for craniospinal irradiation (CSI) treatment.

Methods: Image data of 9 patients who received CSI treatment in 2012 were used, the prescription was 36Gy in 20 fractions. Two treatment plans were created for each patient, one was with the new technique called three-isocenter overlap-junction (TIOJ) IMRT and the other was with the three-isocenter jagged-junction (TIJJ) IMRT technique. The comparative study was conducted using the parameters of heterogeneity index (HI), conformity index (CI), and doses to the organs at risk (OARs).

Results: Comparing the TIOJ IMRT plans with the TIJJ IMRT plans, the average homogeneity index is 0.071 ± 0.003 and 0.077 ± 0.002, respectively, and the averaged conformity number is 0.80 ± 0.012 and 0.80 ± 0.009, respectively. There are no significant differences (p > 0.05). Both plans provide satisfactory sparing for the OARs.

Conclusions: The TIOJ IMRT technique for CSI treatment planning can create similar plans as with the TIJJ IMRT technique, but the new technique greatly simplifies the steps required to manually set field widths and boundaries and improved efficiency.