Optical diffusion performance of nanophosphor-based materials for use in medical imaging

Abstract

Recent technologies, such as nanotechnology, provide new opportunities for next generation scintillation devices and instruments. New nanophosphor-based materials seem to be promising for further improvements in optical diffusion studies. In medical imaging, detector technology has found widespread use, offering improved signal capabilities. However, in spite of many spectacular innovations and the significant research in chemical synthesis on the detective material, improvement in signal quality is still an issue requiring further progress. Here, a sophisticated analysis is shown within the framework of Mie scattering theory and Monte Carlo simulation which demonstrates the optimum structural and optical properties of nanophosphors that are significantly promising in manufacture for further signal modulation improvement. A variety of structural and optical properties were examined: (1) phosphors of grain size (1 to 1000 nm), (2) packing density (50% to 99%), (3) light wavelength (400 to 700 nm), and (4) refractive index of nanophosphor (real part: 1.4-2.0, imaginary part: 10(-6)). Results showed that for a specific thickness of nanophosphor layer, the compromise between spatial resolution and sensitivity can be achieved by optimizing the structural (200 nm ≤ grain diameter ≤ 800 nm) and optical properties of the nanophosphor (1.7 ≤ refractive index ≤ 2.0). Finally, high optical modulation was accomplished employing grains of high refractive index and size above 200 nm.

On the response of semitransparent nanoparticulated films of LuPO4:Eu in poly-energetic X-ray imaging applications

“…It has been shown theoretically [5,6] and demonstrated in practice [7] that diminishing scattering losses in polycrystalline layers is possible in phosphor bodies of reduced grain sizes well below the (emitted) radiation wavelength. This problem was in depth theoretically treated [8] and it was showed that for phosphors emitting in red the optimal imaging resolution properties are achieved when the phosphor particles are about 200 nm in diameter. Nevertheless, the luminescence efficiency of the scintillating screen at this case gets reduced.…”

Light wavelength effects in submicrometer phosphor materials using Mie scattering and Monte Carlo simulation

“…One form of luminescent nanomaterials can be found as powder phosphors, i.e., phosphor grains (in submicrometer scale or in nanoscale) embedded within a binding material, which can be successfully applied as radiation to light converters in detectors of medical imaging systems. [8][9][10] The physical and luminescent properties of phosphor materials, used as radiation-to-light converters, affect the optical signal transferred out of the detector and play a critical role in the quality of the image and thus in diagnosis validity. 11,12 Many investigations have previously examined the luminescent properties of phosphor materials by providing experimental measurements, theoretical calculations via analytical models and Monte Carlo simulations.…”

Nanophosphor Coatings: Technology and Applications, Opportunities and Challenges

“…A comprehensive theoretical treatment applying the Mie scattering theory and Monte Carlo simulations showed that the best imaging performance should be expected from scintillator powders with a particle size greater than 200 nm (Liaparinos, 2012). It should be concluded that there is no advantage of utilizing nanophosphor screens for conventional digital radiography with a resolution lower than 20 lp/mm.…”