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.
Highlights
Solid tumours in pelvic region present with bilateral hip Potter et al.[1] have investigated the treatment of multiple bone metastases where critical organs need to be spared while necessitating their simultane- and have found that the single isocentric treatment ous radio therapeutic treatment
A deviation of -1.87% and -1.30% for ionization chamber (IC)-1 and IC-2 target was observed from the calculated value
Treatment planning of two targets in pelvic region simultaneously treated with common isocenter using 3D-CRT technique was studied and the delivery accuracy was checked in terms of point dose and fluence measurements
Summary
Solid tumours in pelvic region present with bilateral hip Potter et al.[1] have investigated the treatment of multiple bone metastases where critical organs (e.g. bladder and rec- brain tumours with 4 bank micro multi leaf collimator tum) need to be spared while necessitating their simultane- (mMLC) and have found that the single isocentric treatment ous radio therapeutic treatment. Such treatments are usually plan was as good as multiple isocentric plan, which can reexecuted using modern radiotherapy techniques such as in- duce considerable amount of time in QA & treatment delivtensity modulated radiotherapy (IMRT), stereotactic body ery. Huang et al.[4] have execution of multiple targets results in prolongation of compared the quality of target coverage and dose conformity treatment time [starting from pre-treatment quality assurance with single isocentric VMAT-SRS plans to dynamic confor-
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