Encrypted login | home

Program Information

Prostate IMRT and VMAT Plan Evaluation Using the PTV Dose-Volume Factor Based On the Guassian Error Function

J Chow

J Chow1*, R Jiang2 , A Kiciak3 , D Markel1 , (1) Princess Margaret Cancer Centre, Toronto, ON, (2) Grand River Regional Cancer Centre, Kitchener, ON, (3) University of Waterloo, Waterloo, ON


SU-I-GPD-T-415 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: This study compared the dose coverage of planning target volume (PTV) in the prostate intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT). The PTV dose-volume factor (PDVF) based on the Gaussian error function model (GEF) was used.

Methods: Dose-volume histogram curves of PTV for 40 prostate IMRT and 50 prostate VMAT patients, treated with the same dose prescription (78 Gy/39 fraction) and dose-volume criteria in inverse planning optimization, were fitted using the GEF. Parameters from the curve fitting were used to calculate the PDVF justifying the merit of the PTV dose coverage. When the PDVF is equal to one, it represents an ideal PTV dose coverage of 100% volume acquired 100% prescribed dose. In reality, the factor is slightly smaller than one due to critical tissue sparing and other dose-volume restrictions in the treatment planning. Prostate tumour control probabilities (TCP) for the IMRT and VMAT plans were also calculated for comparisons.

Results: From the dose-volume histograms of PTV in the prostate IMRT and VMAT plans, the average D99% of the PTV for IMRT and VMAT were 74.15 and 74.45 Gy. The average prostate TCP was calculated as 0.956 and 0.958 for the IMRT and VMAT plans, and the average PDVF were 0.9697 (IMRT) and 0.9830 (VMAT). It is seen that both delivery techniques can achieve high prostate TCP and PDVF, with the dosimetric and radiobiological results of the VMAT slightly better than IMRT.

Conclusion: From the comparisons of PTV dose coverage between the prostate IMRT and VMAT plans, the PDVF based on the GEF was determined. It is concluded that both calculated PDVF for the prostate IMRT and VMAT plans were close to one, and agreed well with other dosimetric and radiobiological parameters such as D99% and prostate TCP.

Contact Email: