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. 2013 Mar;40(3):031706.
doi: 10.1118/1.4791671.

The effect of flattening filter free delivery on endothelial dose enhancement with gold nanoparticles

Alexandre Detappe  1 , Panagiotis Tsiamas, Wilfred Ngwa, Piotr Zygmanski, Mike Makrigiorgos, Ross Berbeco
Affiliations

The effect of flattening filter free delivery on endothelial dose enhancement with gold nanoparticles

Alexandre Detappe et al. Med Phys. 2013 Mar.

Abstract

Purpose: The aim of this study is to quantify and to compare the dose enhancement factor from gold nanoparticles (AuNP) to tumor endothelial cells for different concentrations of AuNP, and clinical MV beam configurations.

Methods: Tumor endothelial cells are modeled as slabs measuring 10 × 10 × 2 μm. A spherical AuNP is simulated on the surface of the endothelial cell, within the blood vessel. 6 MV photon beams with and without the flattening filter are investigated for different field sizes, depths in material and beam modulation. The incident photon energy spectra for each configuration is generated using EGSnrc. The dose enhancement in the tumor endothelial cell is found using an analytical calculation. The endothelial dose enhancement factor is defined to be the ratio of the dose deposited with and without AuNPs.

Results: It is found that clinical beam parameters may be chosen to maximize the effect of gold nanoparticles during radiotherapy. This effect is further amplified ~20% by the removal of the flattening filter. Modulation of the clinical beam with the multileaf collimator tends to decrease the proportion of low energy photons, therefore providing less enhancement than the corresponding open field.

Conclusions: The results of this work predict a dose enhancement to tumor blood vessel endothelial cells using conventional therapeutic (MV) x-rays and quantify the relative change in enhancement with treatment depth and field size.

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Figures

Figure 1
Figure 1
Representation of the fluence in MeV−1⋅cm−2⋅mGy−1 at the central axis for a 10 × 10 cm2 field size with a semilog scale.
Figure 2
Figure 2
The sphere of interaction represents the range of photoelectrons generated by AuNPs [Berbeco et al. (Ref. 22)].
Figure 3
Figure 3
The total EDEF with 30 mg/ml of gold nanoparticles for 3 different depths: 2, 10, and 20 cm for 5 field sizes: 3 × 3, 5 × 5, 10 × 10, 10 × 1 0 (SW), and 14 × 28 cm2.
See this image and copyright information in PMC

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