SU‐E‐T‐63: A Preliminary Study of Gold Nanoparticles Enhanced Cone Beam Computed Tomography

Abstract

Purpose:Gold nanoparticles (GNPs) have potential of being used as a new‐generation contrast agent to enhance CT imaging of cancer. This feasibility study is to determine the GNP concentration required to provide sufficient image contrast in small animal cone beam CT (CBCT) imaging.Methods:The GNPs used are nanorods with 10nm diameter and 44nm length. A 50µl GNP colloid with an original GNP concentration of 3.6mg/ml was diluted to five different concentrations at 2.4, 2.1, 2.0, 1.9 and 1.8mg/ml, respectively. The GNP colloid was enclosed in a 150µl vial, and the GNP colloid vial was submerged in a water bottle for CBCT. CBCTs were acquired with x‐ray energy of 65kVp and tube current of 1.5mA. In addition, to evaluate the optimal x‐ray energy for GNP detection in CBCT, the GNP colloid of 1.8mg/ml was also imaged at x‐ray energy of 45kVp and 85kVp. Regions of interest were placed in axial CBCT slices contouring the GNP colloid volume and a same volume in the surrounding water to calculate the signal and contrast.Results:For the GNP colloid at concentrations of 3.6, 2.4, 2.1, 2.0, 1.9 and 1.8mg/ml, the image contrasts between GNP colloid and water were 68±4, 33±4, 23±3, 20±3, 13±4, and 10±3 HU, respectively. At 1.8mg/ml concentration level, the image contrasts were 16±3 and 7±4 HU, respectively, when the x‐ray energy was set at 45kVp and 85kVp.Conclusion:The minimal GNP concentration required on our small animal CBCT was estimated to be around 1.8mg/ml due to the fact that the minimum image contrast for adequate differentiation in CT is about 8 HU. CBCT at lower x‐ray energy, i.e. 45kVp, can provide better image contrast than at higher energies, i.e., 65kVp and 85kVp. A study of GNP enhanced CBCT for in vivo small animal imaging is ongoing efforts in our group.