CT imaging of gold nanoparticles in a human‐sized phantom

Abstract

IntroductionGold nanoparticles (AuNPs) are visualized and quantified in a human‐sized phantom with a clinical MDCT scanner.MethodsExperiments were conducted with AuNPs between 0.00171 and 200 mgAu/mL. CT images were acquired at 80, 100, 120, and 140 kVp in a 33‐cm phantom. Image contrast due to AuNPs was experimentally determined from regions of interest (ROIs) and effective linear attenuation coefficients were calculated from CT x‐ray spectra with consideration of tissue attenuation.ResultsThe typical 12‐bit dynamic range of CT images was exceeded for AuNPs at 150 mgAu/mL. A threshold concentration of 0.3–1.4 mgAu/mL was determined for human visualization in 1‐mm images at a typical diagnostic CTDIvol of 23.6 mGy. Optimal image contrast was also achieved at 120 kVp and verified by calculation.ConclusionsWe have shown that scanners capable of reconstructing images with extended Hounsfield scales are required for distinguishing any contrast differences above 150 mgAu/mL. We have also shown that AuNPs result in optimal image contrast at 120 kVp in a human‐sized phantom due to gold’s 80.7 keV k‐edge and the attenuation of x‐rays by tissue. Typical CT contrast agents, like iodine, require the use of lower kVps for optimal visualization, but lower kVps are more difficult to implement in the clinic because of elevated noise levels, elongated scan times, and/or beam‐hardening artifacts. This indicates another significant advantage of AuNPs over iodine not yet discussed in the literature.

Synthesis and Properties of Ag‐Au Alloy Nanoparticles with Controlled Composition for Computed Tomography Imaging Applications

“…[13] The nano Au has a higher X-ray attenuation than iodine complexes due to its high atomic number (Z = 79) and high electron density. [14] The surface properties of the nano Au may be easily changed by biocompatible ligands, and it is also chemically inert and highly biocompatible. Additionally, synthesis approaches can be used to tailor the size and shape of nano Au-based particles.…”

“…Recent research has produced nanoparticles based on Au as an alternative for iodine complexes as a CT contrast agent [13] . The nano Au has a higher X‐ray attenuation than iodine complexes due to its high atomic number (Z=79) and high electron density [14] . The surface properties of the nano Au may be easily changed by biocompatible ligands, and it is also chemically inert and highly biocompatible.…”

High atomic number nanoparticles to enhance spectral CT imaging aspects

“…Moreover, the use of nanoparticles in conjunction with spectral CT imaging has opened the door for potential translation to non-invasive molecular imaging at the human scale for the early detection of diseased cells. 6–9…”

“…Moreover, the use of nanoparticles in conjunction with spectral CT imaging has opened the door for potential translation to non-invasive molecular imaging at the human scale for the early detection of diseased cells. [6][7][8][9] Spectral CT imaging relies on differentiating energydependent information from the CT X-ray scan in the form of linear absorption/attenuation coefficient of tissue, voxel material and/or other components; and concurrently characterizing the tissue and components. During the last two decades, spectral CT imaging has technologically advanced from dualenergy (dual-source or dual-detector, 1st generation) to multienergy photon-counting (2nd generation).…”

Image contrast assessment of metal-based nanoparticles as applications for image-guided radiation therapy

“…The radiosensitising effects of gold NPs (AuNPs) have been demonstrated in many studies [5][6][7]. In addition to their therapeutic dose enhancement in radiation therapy, diagnostic enhancement in CT images has also been reported in several studies [8][9][10]. Although previous studies have used standard diagnostic CT or small animal CT scanners to assess the image contrast ability of AuNPs, none of them have investigated the contrast enhancement in IGRT imaging modalities using AuNPs and other NPs.…”