title: Numerical evaluation of the effectiveness of colloidal gold as a contrast agent.
abstract: Monte Carlo numerical simulations were conducted to evaluate the effectiveness of colloidal gold as a contrast agent. The simulations were conducted using a simple configuration, modeling a phantom to maintain the generality of the results, and the effects of the mass percentage of gold accumulated inside the tumor and the energy of the irradiating X-rays were evaluated, as well as other information, such as the energy spectrum of the photons reaching the detector and the change in the energy deposited inside the phantom. The contrast of the X-ray image due to the layer is calculated from the total energy of photons transmitted to the back surface of the phantom. The simulation revealed that colloidal gold with a mass percentage of 1.0% provided an image for which the contrast was almost 70% of that for bone of the same thickness when X-rays from conventional X-ray tubes were considered. Monochromatic X-rays of 44, 66, and 88 keV, which simulated the Compton scattering monochromatic X-ray source being developed, were also evaluated. X-rays at the first two energies did not have a significant advantage over the rays from the X-ray tubes. For colloidal gold with a mass percentage of 1.0%, the 88 keV monochromatic X-ray produced an image contrast that was about 10% higher than the contrast for bone of the same thickness, as suggested by the K-absorption energy of gold. However, the improvement was not large considering the difficulty involved in making such a high-energy monochromatic X-ray source available.
authors.affiliation: Nuclear Professional School, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan. yusa@n.t.u-tokyo.ac.jp
authors.forename: Noritaka
authors.initials: N
authors.lastname: Yusa
authors.forename: Meiling
authors.initials: M
authors.lastname: Jiang
authors.forename: Kazue
authors.initials: K
authors.lastname: Mizuno
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Uesaka
mesh_terms: D003287:Contrast Media; D017979:Gold Colloid; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D017979:Gold Colloid
references.citation: Mol Cancer Ther. 2006 Apr;5(4):1014-20
references.pmid: 16648573
references.citation: Adv Colloid Interface Sci. 2006 Nov 16;123-126:471-85
references.pmid: 16890182
references.citation: Nat Nanotechnol. 2008 Mar;3(3):145-50
references.pmid: 18654486
references.citation: J Control Release. 2006 Sep 12;114(3):343-7
references.pmid: 16876898
references.citation: Br J Radiol. 2006 Mar;79(939):248-53
references.pmid: 16498039
references.citation: Int J Radiat Biol. 2000 Oct;76(10):1357-64
references.pmid: 11057744
references.citation: Invest Radiol. 2007 Dec;42(12):797-806
references.pmid: 18007151
references.citation: Phys Med Biol. 2004 Sep 21;49(18):N309-15
references.pmid: 15509078
references.citation: Acad Radiol. 2003 Dec;10(12):1450-60
references.pmid: 14697013
references.citation: Chem Rev. 2004 Jan;104(1):293-346
references.pmid: 14719978
references.citation: Phys Med Biol. 2005 Aug 7;50(15):N163-73
references.pmid: 16030374
references.citation: Drug Deliv. 2004 May-Jun;11(3):169-83
references.pmid: 15204636
references.citation: Biochim Biophys Acta. 1983 Jul 13;732(1):320-3
references.pmid: 6871199
references.citation: Nano Lett. 2006 Apr;6(4):662-8
references.pmid: 16608261