RESUMO
PURPOSE: Several investigations are being carried since the past decade to use gold nanoparticles' (AuNP) suspensions as contrast agents (CA) for imaging in Computed Tomography. For this, the optimal size of AuNP has received considerable attention, which is addressed here. MATERIAL AND METHODS: In this theoretical study, effective attenuation coefficient for a single spherical shaped AuNP is first calculated from the first principles, as a function of the nanoparticle radius 'r', with µ(E) being the attenuation coefficient of the material for a given energy E. This result is extended to derive a formula for the attenuation coefficient and mass attenuation coefficient of a suspension of AuNP. RESULTS: It is seen that the effective mass attenuation coefficient of the nanoparticles is a decreasing function of α(E) = 2µ(E)r and falls inversely with α(E), for large values of α(E) â« 1, there being very little change for α ≤ 1. CONCLUSION: The paper shows that for nanoparticles, less than 100 nm in diameter the linear attenuation coefficient of the colloidal suspension has no dependence on the nanoparticles' size and depends only on the concentration of nanoparticle material present in the suspension.