Impact of beam quality on megavoltage radiotherapy treatment techniques utilizing gold nanoparticles for dose enhancement

Abstract

This study determines the optimal clinical scenarios for gold nanoparticle dose enhancement as a function of irradiation conditions and potential biological targets using megavoltage x-ray beams. Four hundred and eighty clinical beams were studied for different potential cellular or sub-cellular targets. Beam quality was determined based on a 6 MV linac with and without a flattening filter for various delivery conditions. Dose enhancement ratios DER = D GNP /D water were calculated for all cases using the GEANT4 Monte Carlo code and the CEPXS/ONEDANT radiation transport deterministic code. Dose enhancement using GEANT4 agreed with CEPXS/ONEDANT. DER for unflattened beams is ∼2 times larger than for flattened beams. The maximum DER values were calculated for split-IMRT fields (∼6) and for out-of-field areas of an unflattened linac (∼17). In-field DER values, at the surface of gold nanoparticles, ranged from 2.2 to 4.2 (flattened beam) and from 3 to 4.7 (unflattened beams). For a GNP cluster with thicknesses of 10 and 100 nm, the DER ranges from 14% to 287%. DER is the greatest for split-IMRT, larger depths, out-of-field areas and/or unflattened linac. Mapping of a GNP location in tumor and normal tissue is essential for efficient and safe delivery of nanoparticle-enhanced radiotherapy.

Nanoscale radiation transport and clinical beam modeling for gold nanoparticle dose enhanced radiotherapy (GNPT) using X-rays

“…For such multiple planar clusters, the simulation geometry (medium and scoring) problem is converted to a 1D problem. [51][52][53] This is so by noting that the average in-plane dose as a function of distance from a planar cluster is similar (though not identical, as explained later) to the dose for multiple thin slabs with uniform equivalent mixtures of gold and water. Using thin slab mixtures of gold and water simplifies the geometry and improves the MC statistics.…”

“…For convenience, we arrange the literature according to the following order: general radiation transport aspects relevant for nanoscale simulations, [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] macroscopic dose enhancement in contrast agents and dose perturbation at high-Z material interfaces, radiation transport for nanoscopic dose enhancement of GNP, [46][47][48][49][50][51][52][53][54][55][56][57][58] radiobiological and clinical aspects of GNPT, [59][60][61][62][63][64][65][66][67] application of Monte Carlo (MC) simulations to cellular environment, [68][69][70] modification of linear accelerator spectra to maximize dose enhancement 71 and GNPT using other than X-ray therapeutic beams (proton, electron). …”

Targeted nanoparticles for tumour radiotherapy enhancement—the long dawn of a golden era?

“…A number of Monte-Carlo simulations of possible clinical scenarios were carried out in the last few years to this purpose [see, for example, (17)(18)(19)(20)(21)(22)]. Such simulations are based on the fact that the transport of ionizing radiation in matter is of random nature and can be described using probabilistic models.…”

Potential application of metal nanoparticles for dosimetric systems: Concepts and perspectives

“…However, bearing in mind that the nano and microcomposites have identical composition (except for particle size), this silveractivation process should also intensify OSL from the microcomposites. Another hypothesis would be that OSL enhancement stems from the increased mass absorption coefficient prompted by the silver nanoparticles 9,42,[49][50] . Nevertheless, the theoretical dose enhancement factor caused by a mass percentage of 0.05% silver in NaCl would be 0.13%.…”