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SU‐GG‐J‐123: Dose Increase in Radiotherapy Evaluated to Biocompatible Levels of Gold Nanoparticle: A Quantitative Analysis by MRI Gel Dosimetry and Monte Carlo Spectrometry
Author(s) -
Marques T,
Schwarcke M,
Garrido C,
Zucolotto V,
Baffa O,
Nicolucci P
Publication year - 2010
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 - 10.1118/1.3468347
Subject(s) - monte carlo method , dosimetry , materials science , colloidal gold , dosimeter , nuclear medicine , absorbed dose , radiochemistry , nanoparticle , chemistry , medicine , nanotechnology , mathematics , statistics
Purpose : Apply gel dosimetry to evaluate the dose‐increase dependency with nanoparticle concentration in a tissue‐simulator dosimeter irradiated with 250kV Radiotherapy beam. Quantify the components of dose contribution by Monte Carlo spectrometry. Material and Methods : Gold nanoparticles (AuNP) were embedded in MAGIC‐ f gel in different biocompatible concentrations: 0.11mM(A), 0.06mM(B) and 0.03mM(C). Dosimetric control measures with gel without AuNP were made in the 250kV x‐ray beam studied. An acrylic box was positioned behind the gel samples to guarantee backscattered conditions similar to clinical situations accessed with the beam studied. A dose of 5Gy was delivered to all samples. Polymer gel readings were proffered in a 3Tesla nuclear‐magnetic‐resonance by relaxometry: 5 echoes; Echo‐time=20ms; Repetition‐time=4000ms; Pixel‐size=250μm; Time‐delay‐to‐reading: 12h. Monte Carlo simulations were performed in PENELOPE code precisely reproducing all experimental conditions. Results : Signal of non‐irradiated gel samples (with and without AuNP) presents no significant variation (<0.5%), evidencing no influences of AuNP in MRI reading. Concentrations A, B and C presents a 106%, 90% and 77% of signal increase, respectively. Comparing with the dose calibration curve of gel, the signal growth represents dose enhancements of 5.3Gy, 4.5Gy and 3.9Gy to concentrations A, B and C respectively. Monte Carlo shows a dose increase of 10.2keV/g, 9.1eV/g and 7.3eV/g, representing 105%, 93% and 75% of perceptual dose growth to concentrations A, B and C respectively. Spectrometry analysis revel a fluorescence dose fraction that contributes to dose increase of 0.98, 0.89 and 0.73 and low‐energy Compton events that contributes to local dose increase in fractions of 0.66, 0.38 and 0.12 to concentrations A, B and C respectively. Conclusions : Dose increase in Radiotherapy due to AuNP presence has a non‐linear dependency with the concentration. The growth of local doses may be high expressed indicating possible clinical benefits of using AuNP added Radiotherapy.