Preclinical Spectral Computed Tomography of Gold Nano-Particles

Today’s state-of the art clinical computed tomography (CT) scannersexclusively use energy-integrating, scintillation detector technology, despite the fact that a part of the information carried by the transmitted x-ray photons is lost during the detection process. Roomtemperature semiconductors, like CdTe or CZT, operated in energysensitive photon-counting mode provide information about the energy of every single x-ray detection event. This capability allows novel, promising approaches to selectively image abnormal tissue types like cancerous tissue or atherosclerotic plaque with the CT modality. In thisarticle we report on recent dual K-edge imaging results obtained inthe domain of pre-clinical, energy-sensitive photon counting CT. Inthis approach, the tuning of threshold levels in the detector electronics to the K-edge energy in the attenuation of contrast agents (CA) offers highly specific, quantitative imaging of the distributionof the CA on top of the conventional, morphological image information. The combination of the high specificity of the K-edge imaging technique together with the powerful tool of targeting specific diseases in the human body by dedicated contrast materials might enrich theCT modality with capabilities of functional imaging known from thenuclear medicine imaging modalities, e.g., positron-emission-tomography but with the additional advantage of high spatial and temporal resolution. We also discuss briefly the technological difficulties tobe overcome when translating the technique to human CT imaging andpresent the results of simulations indicating the feasibility of theKedge imaging of vulnerable plaque using targeted gold nano-particles as contrast materials. Our experiments in the pre-clinical domainshow that dual-K edge imaging of iodine and gold based CAs is feasible while our simulations for the imaging of gold CAs in the clinical case support the future possibility of translating the technique to human imaging.