Shielding in whole brain irradiation in the multileaf collimator era: dosimetric evaluation of coverage using SFOP guidelines against in-house guidelines.

AIM Compare the planning target volume (PTV) coverage in three different shielding techniques in cranial irradiation. SETTINGS AND DESIGN Tertiary care center, prospective study. MATERIALS AND METHODS The whole brain and meninges were contoured in ten planning CT scans, and expanded by 5 mm for the PTV. Shielding was designed using the French Society of Pediatric Oncology (SFOP) guidelines (SFOP plan), in-house recommendation (with 1 cm margin from the orbital roof and sphenoid wing) on a igitally Reconstructed Radiograph (DRR) and a third plan was generated using a 3D conformal radiation technique (3DCRT). The coverage of the PTV was noted using the isodose covering 95% of the PTV(D95), minimum dose within the PTV(D min ), and maximum dose within the PTV(D max ). The location of PTV not covered by the 95% isodose curve was noted. The median dose and maximum dose (D max ) to both eyes and maximum dose D max for the lens were noted. STATISTICAL ANALYSIS General linear model method repeated the measure of analysis of variance test (ANOVA). RESULTS PTV coverage was significantly poorer in the SFOP and in-house plans as compared to 3DCRT plan (P=0.04). Median volume of PTV not covered by 95% isodose curve was 4.18 cc, 1.01 cc, and 0 cc in SFOP, in-house, and 3DCRT plan, respectively. CONCLUSIONS In the absence of volumetric planning techniques, SFOP guidelines lead to inadequate coverage and the in-house method is recommended.