Highlights
- •Shows inconsistency of prescribing to lung PTV volumes for Monte Carlo calculations.
- •Provides data showing that Dose Mass Histograms do not offer a solution either.
- •The suggested solution is to abandon the PTV concept.
Abstract
Purpose
The goal of this study is to show that the PTV concept is inconsistent for prescribing
lung treatments when using type B algorithms, which take into account lateral electron
transport. It is well known that type A dose calculation algorithms are not capable
of calculating dose in lung correctly. Dose calculations should be based on type B
algorithms. However, the combination of a type B algorithm with the PTV concept leads
to prescription inconsistencies.
Methods
A spherical isocentric setup has been simulated, using multiple realistic values for
lung density, tumor density and collimator size. Different prescription methods are
investigated using Dose-Volume-Histograms (DVH), Dose-Mass-Histograms (DMH), generalized
Equivalent Uniform Dose (gEUD) and surrounding isodose percentage.
Results
Isodose percentages on the PTV drop down to 50% for small tumors and low lung density.
When applying the same PTV prescription to different patients with different lung
characteristics, the effective mean dose to the GTV is very different, with factors
up to 1.4. The most consistent prescription method seems to be the (PTV) DMH point, but is also limited to tumors with size over 1 cm.
Conclusions
Even when using the different prescription methods, the prescription to the PTV is
not consistent for type B-algorithm based dose calculations if clinical studies should
produce coherent data. This combination leads to patients’ GTV with low lung density
possibly receiving very high dose compared to patients with higher lung density. The
only solution seems to remove the classical PTV concept for type B dose calculations
in lung.
Abbreviations:
MC (Monte Carlo), PTV (Planning Target Volume), DVH (Dose-Volume Histogram), DMH (Dose-Mass Histogram), gEUD (generalized Equivalent Uniform Dose), FFF (Flattening Filter Free)Keywords
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References
- Accuracy of patient dose calculation for lung IMRT: a comparison of Monte Carlo, convolution/superposition, and pencil beam computations.Med Phys. 2006; 33: 3149-3158https://doi.org/10.1118/1.2241992
- Clinical introduction of Monte Carlo treatment planning for lung stereotactic body radiotherapy.J Appl Clin Med Phys. 2014; 15: 4202
- The effect of different lung densities on the accuracy of various radiotherapy dose calculation methods: implications for tumour coverage.Radiother Oncol. 2009; 91: 405-414https://doi.org/10.1016/j.radonc.2009.01.008
- Clinical introduction of Monte Carlo treatment planning: a different prescription dose for non-small cell lung cancer according to tumor location and size.Radiother Oncol. 2010; 96: 55-60https://doi.org/10.1016/j.radonc.2010.04.009
- Dose calculation algorithm accuracy for small fields in non-homogeneous media: the lung SBRT case.Phys Medica. 2016; https://doi.org/10.1016/j.ejmp.2016.11.104
- The probability of correct target dosage: Dose-population histograms for deriving treatment margins in radiotherapy.Int J Radiat Oncol Biol Phys. 2000; 47: 1121-1135https://doi.org/10.1016/S0360-3016(00)00518-6
- Lung SABR: a large-scale multi-institutional dosimetric and radiobiological planning comparison.Phys Medica. 2016; 32: 29https://doi.org/10.1016/j.ejmp.2016.01.100
- Transition from a simple to a more advanced dose calculation algorithm for radiotherapy of non-small cell lung cancer (NSCLC): implications for clinical implementation in an individualized dose-escalation protocol.Radiother Oncol. 2008; 88: 326-334https://doi.org/10.1016/j.radonc.2008.07.003
- What do radiation oncologists require for future advancements in lung SBRT?.Phys Medica. 2016; : 1-7https://doi.org/10.1016/j.ejmp.2016.11.114
- GTV-based prescription in SBRT for lung lesions using advanced dose calculation algorithms.Radiat Oncol. 2014; 9: 223https://doi.org/10.1186/s13014-014-0223-5
- Reconsidering the definition of a dose–volume histogram.Phys Med Biol. 2005; 50: L17-L19https://doi.org/10.1088/0031-9155/50/11/L01
- Comments on “Reconsidering the definition of a dose-volume histogram”–dose-mass histogram (DMH) versus dose-volume histogram (DVH) for predicting radiation-induced pneumonitis.Phys Med Biol. 2006; 51: L43-L50https://doi.org/10.1088/0031-9155/51/24/L01
- Reporting and analyzing dose distributions: a concept of equivalent uniform dose.Med Phys. 1997; 24: 103-110https://doi.org/10.1118/1.598154
- The Use and QA of Biologically Related Models for Treatment Planning Report of AAPM Task Group 166.2012https://doi.org/10.1118/1.3685447
- EGSnrc C++ class library.(Technical Report PIRS-898)2005
- The EGSnrc code system: Monte Carlo simulation of electron and photon transport.Med Phys. 2013; 34: 2001-2013
- BEAMnrc Users Manual.Source. 2011; 509: 1-260
- Monte Carlo treatment planning for photon and electron beams.Radiat Phys Chem. 2007; 76: 643-686https://doi.org/10.1016/j.radphyschem.2006.05.015
- Use of a liquid ionization chamber for stereotactic radiotherapy dosimetry.Phys Med Biol. 2013; 58: 2445-2459https://doi.org/10.1088/0031-9155/58/8/2445
- Stereotactic body radiation therapy: the report of AAPM Task Group 101.Med Phys. 2010; 37: 4078https://doi.org/10.1118/1.3438081
ICRU. ICRU 83 Prescribing, Recording, and Reporting Photon-Beam Intensity-Modulated Radiation Therapy (IMRT). vol. 10. 2010. doi: https://doi.org/10.1093/jicru/ndq025.
- Dose reconstruction in deforming lung anatomy: dose grid size effects and clinical implications.Med Phys. 2005; 32: 2487-2495https://doi.org/10.1118/1.1949749
- Forcing lateral electron disequilibrium to spare lung tissue: a novel technique for stereotactic body radiation therapy of lung cancer.Phys Med Biol. 2013; 58: 6641-6662https://doi.org/10.1088/0031-9155/58/19/6641
- Is a clinical target volume (CTV) necessary in the treatment of lung cancer in the modern era combining 4-D imaging and image-guided radiotherapy (IGRT)?.Cureus. 2016; 8: 1-15https://doi.org/10.7759/cureus.466
Article Info
Publication History
Published online: March 30, 2017
Accepted:
March 18,
2017
Received in revised form:
March 16,
2017
Received:
December 14,
2016
Identification
Copyright
© 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
