Quality assurance of simultaneous treatment of two targets in pelvic region planned with single isocenter using three dimensional conformal radiotherapy (3DCRT) technique

Abstract

Purpose: The purpose of this study was to conduct quality assurance of a three dimensional conformal radiotherapy (3DCRT) of two targets in pelvis region planned with single isocenter technique. Methods: A treatment plan was generated with two identical water phantoms with ionization chamber (IC) sleeves (IC-1 & IC-2), simulated as if targets are in pelvis region, simultaneously irradiated with single isocenter technique with a dose prescription of 300 cGy for point dose verification. A two dimensional ion chamber array detector was used for fluence verification.Results: Calculated minimum, mean and maximum dose (in cGy) for IC-1 & IC-2 were 295, 303 and 307 as per dose volume histogram. The global dose maximum was found to be 307.4 cGy. Measured point doses to both lesions were within ±2.5% of the computed dose. A pass percentage of 97% was obtained with the set of criteria 3 mm distance to agreement and 3% dose difference for fluence verification.Conclusion: Treatment execution of two targets simultaneously with single isocenter can reduce positional errors and delivery time