Evaluation of the X-Ray Absorption by Gold Nanoparticles Solutions

The increase in the X-ray absorption due to gold nanoparticles was investigated by using aqueous solutions containing gold (Au) nanoparticles. A sample with 15？nm in size nanoparticles and 0.5？mg/mL gold concentration and a distilled water sample were used. Transmitted X-ray beams through the samples were registered with a CdTe detector and with an ionization chamber. Results show an enhancement in the X-ray absorption in the range 20%–6% for beams generated from 20？kV to 120？kV tube voltages, respectively. Results show that the use of gold nanoparticles, even at low concentrations, should result in a significant contrast enhancement for low-energy X-ray beams. 1. Introduction X-ray radiography procedures are one of the most useful tools adopted in the early diagnosis of cancer in both time and cost related to the process of image acquisition [1]. The efficacy of these techniques relies on the image quality which depends on the X-ray absorption by the tissues that are being exposed [1]. In some of these radiological procedures, such as X-ray computed tomography, a contrast agent is injected directly into the blood stream followed by immediate imaging. The contrast agent leads to increased X-ray attenuation by the targeted tissue resulting in an enhanced image contrast [1, 2]. Currently, contrast agents used in clinical routine procedures are mainly based on iodine-containing molecules. However, such iodine-based compounds present a short-imaging time which results from its rapid renal clearance [3, 4]. In this way, biocompatible nanostructured materials are being investigated in order to improve the image contrast and to enhance the image acquisition time [3–7]. Gold nanoparticles (GNPs) have been the subject of numerous theoretical and experimental studies related to its applications as contrast agents in the X-ray imaging field [3, 5, 8]. The use of these particles in computed tomography has attractive properties such as high atomic number (Z = 79) and density ( = 19.3？g/cm3), high X-ray attenuation coefficients, and enhanced time of blood circulation providing imaging contrast for longer time periods [5, 9]. As the radiographic image contrast depends on the radiation absorption by the target materials, the effect of gold nanoparticles in the X-ray image could be evaluated by means of X-ray spectroscopy. In this work we report the spectral changes on X-ray beams transmitted through a gold nanoparticle aqueous solution registered with a X-ray spectrometer. We chose this detector due to its good performance in the diagnostic energy range [10–12].