title: The effect of flattening filter free delivery on endothelial dose enhancement with gold nanoparticles.
abstract: OBJECTIVE
  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.
authors: Dana-Farber Cancer Institute, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
authors: Alexandre
authors: A
authors: Detappe
authors: Panagiotis
authors: P
authors: Tsiamas
authors: Wilfred
authors: W
authors: Ngwa
authors: Piotr
authors: P
authors: Zygmanski
authors: Mike
authors: M
authors: Makrigiorgos
authors: Ross
authors: R
authors: Berbeco
mesh_terms: D042783:Endothelial Cells / Q000528:radiation effects*; D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles; D009010:Monte Carlo Method; D017785:Photons / Q000627:therapeutic use; D011829:Radiation Dosage; D011878:Radiotherapy / Q000379:methods*; D011879:Radiotherapy Dosage
chemical_list: D006046:Gold