Photon activation therapy: a Monte Carlo study on dose enhancement by various sources and activation media

Abstract

In the present study, a number of brachytherapy sources and activation media were simulated using MCNPX code and the results were analyzed based on the dose enhancement factor values. Furthermore, two new brachytherapy sources (¹³¹Cs and a hypothetical ¹⁷⁰Tm) were evaluated for their application in photon activation therapy (PAT). ¹²⁵I, ¹⁰³Pd, ¹³¹Cs and hypothetical ¹⁷⁰Tm brachytherapy sources were simulated in water and their dose rate constant and the radial dose functions were compared with previously published data. The sources were then simulated in a soft tissue phantom which was composed of Ag, I, Pt or Au as activation media uniformly distributed in the tumour volume. These simulations were performed using the MCNPX code, and dose enhancement factor (DEF) was obtained for 7, 18 and 30 mg/ml concentrations of the activation media. Each source, activation medium and concentration was evaluated separately in a separate simulation. The calculated dose rate constant and radial dose functions were in agreement with the published data for the aforementioned sources. The maximum DEF was found to be 5.58 for a combination of the ¹⁷⁰Tm source with 30 mg/ml concentration of I. The DEFs for ¹³¹Cs and ¹⁷⁰Tm sources for all the four activation media were higher than those for other sources and activation media. From this point of view, these two sources can be more useful in photon activation therapy with photon emitter sources. Furthermore, ¹³¹Cs and ¹⁷⁰Tm brachytherapy sources can be proposed as new options for use in the field of PAT.

A Monte Carlo study on dose enhancement and photon contamination production by various nanoparticles in electron mode of a medical linac

“…In the present study, 2 mm × 2 mm × 2 mm voxels were used in dose calculations. Bakhshabadi et al [24] defined cells with 1 mm thickness as the tally cells in photon activation therapy. In photon activation therapy the dose due to secondary particles (Auger electrons) are the most responsible for the biological effect, in some extent similar to the present study in which the secondary electrons are important.…”

Simulation of dose enhancement in radiotherapy caused by cisplatin

“…In the next stage of dose change simulation, we performed with the presence of cisplatin in the target volume. Cisplatin concentrations were selected on the basis of acceptable doses that were considered in previous works by the authors and higher to evaluate dose changes from cisplatin concentration [12,13,14,15,16], while 0,003 mM is the minimum cisplatin concentration during which there is a visible effect in radiobiological experiments after X-ray irradiation. Cisplatin was injected into the target, which was located at a certain depth of water phantom.…”

“…Cisplatin was injected into the target, which was located at a certain depth of water phantom. Cisplatin concentrations were selected on the basis of acceptable doses that were considered in previous works by the authors and higher to evaluate dose changes from cisplatin concentration [23][24][25][26][27], while 0,003 mM is the minimum cisplatin concentration which produces a visible effect in radiobiological experiments after X-ray irradiation. However, chemotherapists do not exceed the recommended daily dose of cisplatin more than 100 mg/m 2 [28].…”

Nanoparticles as Theranostic Vehicles in Experimental and Clinical Applications—Focus on Prostate and Breast Cancer

“…The photon activation therapy (PAT), sometimes also referred to as photon activated therapy, involving Auger electrons and mentioned for the first time for medical applications over three decades ago, shows a limited amount of publications but is an interesting option for TNPs and therefore discussed here [453,454,455,456,457,458,459,460,461]. The PAT technique is based on the principle of specific tumor localization of a high-Z compound such as platinum (Pt), incorporated in, for example, a CTH drug, after which synchrotron radiation or X-rays directed against the tumor site is used to, via the photoelectric effect, trigger a cascade release of high linear energy transfer (high-LET) Auger electrons.…”