- •Monte Carlo computed clinical plans for the TomoTherapy system with dynamic jaws.
- •First Monte Carlo evaluation of TomoTherapy TPS with VoLO and TomoEdge.
- •Good agreement between MC and TomoTherapy's TPS (typically 1% for targets).
- •5% difference for small lung tumors, due to dose calculation, not TomoEdge model.
For the TomoTherapy® system, longitudinal conformation can be improved by selecting a smaller field width but at the expense of longer treatment time. Recently, the TomoEdge® feature has been released with the possibility to move dynamically the jaws at the edges of the target volume, improving longitudinal penumbra and enabling faster treatments. Such delivery scheme requires additional modeling of treatment delivery. Using a previously validated Monte Carlo model (TomoPen), we evaluated the accuracy of the implementation of TomoEdge in the new dose engine of TomoTherapy for 15 clinical cases.
TomoPen is based on PENELOPE. Particle tracking in the treatment head is performed almost instantaneously by 1) reading a particle from a phase-space file corresponding to the largest field and 2) correcting the weight of the particle depending on the actual jaw and MLC configurations using Monte Carlo pre-generated data. 15 clinical plans (5 head-and-neck, 5 lung and 5 prostate tumors) planned with TomoEdge and with the last release of the treatment planning system (VoLO®) were re-computed with TomoPen. The resulting dose-volume histograms were compared.
Good agreement was achieved overall, with deviations for the target volumes typically within 2% (D95), excepted for small lung tumors (17 cm3) where a maximum deviation of 4.4% was observed for D95. The results were consistent with previously reported values for static field widths.
For the clinical cases considered in the present study, the introduction of TomoEdge did not impact significantly the accuracy of the computed dose distributions.
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Published online: February 03, 2015
Accepted: January 19, 2015
Received in revised form: January 14, 2015
Received: December 10, 2014
© 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Inc. All rights reserved.