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.