Optimizing dose enhancement with Ta2O5 nanoparticles for synchrotron microbeam activated radiation therapy. Issue 12 (December 2016)

• Record Type: Journal Article
• Authors: Engels, Elette; Corde, Stéphanie; McKinnon, Sally; Incerti, Sébastien; Konstantinov, Konstantin; Rosenfeld, Anatoly; Tehei, Moeava; Lerch, Michael; Guatelli, Susanna
• Is Part Of: Physica medica. Volume 32:Issue 12(2016)
• Page Start: 1852
• Page End: 1861
• Publication Date: 2016-12
• Subjects: Nanoparticle -- Microbeam radiation therapy -- Dose enhancement -- Geant4; Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2016.10.024
• Languages: English
• ISSNs: 1120-1797

Abstract

Highlights: Ta2 O5 nanoparticles (NPs) enhance radiosensitisation in MRT. Dose enhancement with NPs is dependent on the microbeam energy. The nanoparticle distribution plays an important role in MRT dose enhancement. Ta2 O5 NPs reduce PVDR for MRT energies above ∼100 keV. Ta2 O5 NPs provide a more targeted radiosensitisation below ∼70 keV. Abstract: Microbeam Radiation Therapy (MRT) exploits tumour selectivity and normal tissue sparing with spatially fractionated kilovoltage X-ray microbeams through the dose volume effect. Experimental measurements with Ta2 O5 nanoparticles (NPs) in 9L gliosarcoma treated with MRT at the Australian Synchrotron, increased the treatment efficiency. Ta2 O5 NPs were observed to form shells around cell nuclei which may be the reason for their efficiency in MRT. In this article, our experimental observation of NP shell formation is the basis of a Geant4 radiation transport study to characterise dose enhancement by Ta2 O5 NPs in MRT. Our study showed that NP shells enhance the physical dose depending microbeam energy and their location relative to a single microbeam. For monochromatic microbeam energies below ∼70 keV, NP shells show highly localised dose enhancement due to the short range of associated secondary electrons. Low microbeam energies indicate better targeted treatment by allowing higher microbeam doses to be administered to tumours and better exploit the spatial fractionation related selectivity observed with MRT. For microbeam energies above ∼100 keV, NP shells extend the physical dose enhancement due to longer-range secondary electrons. Again, with NPs selectively internalised, the local effectiveness of MRT is expected to increase in the tumour. Dose enhancement produced by the shell aggregate varied more significantly in the cell population, depending on its location, when compared to a homogeneous NP distribution. These combined simulation and experimental data provide first evidence for optimising MRT through the incorporation of newly observed Ta2 O5 NP distributions within 9L cancer cells.