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Performance of a hybrid MC dose algorithm for IMRT optimization dose evaluation
Author(s) -
Siebers Jeffrey V.,
Kawrakow Iwan,
Ramakrishnan V.
Publication year - 2007
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2745236
Subject(s) - computer science , deliverable , monte carlo method , algorithm , dosimetry , truebeam , nuclear medicine , mathematics , medicine , beam (structure) , linear particle accelerator , physics , engineering , optics , statistics , systems engineering
This paper presents a hybrid intensity modulated radiation therapy (IMRT) optimization strategy which combines the speed of pencil beam (PB) and the accuracy of Monte Carlo (MC) dose calculations. After an initial deliverable‐based optimization using a PB algorithm, doses are recomputed using the VMC + + MC code to determine dose correction factors, which are then utilized during further PB‐based optimization. The hybrid method is benchmarked with respect to full MC deliverable‐based optimization for ten prostate and ten head‐and‐neck IMRT plans. Final optimized plans are compared in terms of dose‐volume indices used for the plan optimization. Dose prediction errors (DPEs) and optimization convergence errors (OCEs) at intermediate steps of the hybrid sequence are evaluated. The hybrid method is found to produce optimized plans that are clinically equivalent to full MC‐based optimization, yet requires only 40% of the number of MC dose calculations. With the hybrid strategy presented here, MC‐based optimization results are achieved in 35 min or less on a modest computing cluster. While the initial PB‐deliverable‐based optimization is found to have DPEs and OCEs of up to 3 Gy relative to the 65 – 73 Gy prescription doses, application of the first MC correction reduces the average DPEs to less than 0.3 Gy for the prostate plans and less than 0.06 Gy for the head and neck plans. The maximum observed DPE or OCE is 0.7 Gy after 1 MC dose correction, indicating that a single MC dose calculation correction might be sufficient for IMRT optimization.