K-edge ratio method for identification of multiple nanoparticulate contrast agents by spectral CT imaging.

OBJECTIVE Recently introduced energy-sensitive X-ray CT makes it feasible to discriminate different nanoparticulate contrast materials. The purpose of this work is to present a K-edge ratio method for differentiating multiple simultaneous contrast agents using spectral CT. METHODS The ratio of two images relevant to energy bins straddling the K-edge of the materials is calculated using an analytic CT simulator. In the resulting parametric map, the selected contrast agent regions can be identified using a thresholding algorithm. The K-edge ratio algorithm is applied to spectral images of simulated phantoms to identify and differentiate up to four simultaneous and targeted CT contrast agents. RESULTS We show that different combinations of simultaneous CT contrast agents can be identified by the proposed K-edge ratio method when energy-sensitive CT is used. In the K-edge parametric maps, the pixel values for biological tissues and contrast agents reach a maximum of 0.95, whereas for the selected contrast agents, the pixel values are larger than 1.10. The number of contrast agents that can be discriminated is limited owing to photon starvation. For reliable material discrimination, minimum photon counts corresponding to 140 kVp, 100 mAs and 5-mm slice thickness must be used. CONCLUSION The proposed K-edge ratio method is a straightforward and fast method for identification and discrimination of multiple simultaneous CT contrast agents. ADVANCES IN KNOWLEDGE A new spectral CT-based algorithm is proposed which provides a new concept of molecular CT imaging by non-iteratively identifying multiple contrast agents when they are simultaneously targeting different organs.

[1]  W P Segars,et al.  Realistic CT simulation using the 4D XCAT phantom. , 2008, Medical physics.

[2]  Gerhard Martens,et al.  Preclinical spectral computed tomography of gold nano-particles , 2011 .

[3]  Hyo-Min Cho,et al.  A Monte Carlo simulation study of the effect of energy windows in computed tomography images based on an energy-resolved photon counting detector , 2012, Physics in medicine and biology.

[4]  Cynthia H McCollough,et al.  Estimating effective dose for CT using dose-length product compared with using organ doses: consequences of adopting International Commission on Radiological Protection publication 103 or dual-energy scanning. , 2010, AJR. American journal of roentgenology.

[5]  Yun Sun,et al.  Water-stable NaLuF4-based upconversion nanophosphors with long-term validity for multimodal lymphatic imaging. , 2012, Biomaterials.

[6]  Uwe Oelfke,et al.  Imaging properties of small-pixel spectroscopic x-ray detectors based on cadmium telluride sensors , 2012, Physics in medicine and biology.

[7]  A. Butler,et al.  First CT using Medipix3 and the MARS-CT-3 spectral scanner , 2011 .

[8]  Axel Thran,et al.  An early investigation of ytterbium nanocolloids for selective and quantitative "multicolor" spectral CT imaging. , 2012, ACS nano.

[9]  P. Suetens,et al.  Metal streak artifacts in X-ray computed tomography: a simulation study , 1998, 1998 IEEE Nuclear Science Symposium Conference Record. 1998 IEEE Nuclear Science Symposium and Medical Imaging Conference (Cat. No.98CH36255).

[10]  A. Macovski,et al.  Energy-selective reconstructions in X-ray computerised tomography , 1976, Physics in medicine and biology.

[11]  Paul F FitzGerald,et al.  Biological Performance of a Size-Fractionated Core-Shell Tantalum Oxide Nanoparticle X-Ray Contrast Agent , 2012, Investigative radiology.

[12]  J. Schlomka,et al.  Multienergy photon-counting K-edge imaging: potential for improved luminal depiction in vascular imaging. , 2008, Radiology.

[13]  A. Macovski,et al.  Generalized image combinations in dual KVP digital radiography. , 1981, Medical physics.

[14]  H Zaidi,et al.  Measurement of scattered radiation in a volumetric 64-slice CT scanner using three experimental techniques , 2010, Physics in medicine and biology.

[15]  Ko Kang Ning,et al.  SYNTHESIS AND CHARACTERIZATION OF , 2011 .

[16]  S. Nair,et al.  A molecular receptor targeted, hydroxyapatite nanocrystal based multi-modal contrast agent. , 2010, Biomaterials.

[17]  Lehui Lu,et al.  Nanoparticulate X-ray computed tomography contrast agents: from design validation to in vivo applications. , 2012, Accounts of chemical research.

[18]  Taly Gilat Schmidt,et al.  CT energy weighting in the presence of scatter and limited energy resolution. , 2010, Medical physics.

[19]  J. Hsieh.  Analytical models for multi-slice helical CT performance parameters. , 2003, Medical physics.

[20]  J. Schlomka,et al.  Experimental feasibility of multi-energy photon-counting K-edge imaging in pre-clinical computed tomography , 2008, Physics in medicine and biology.

[21]  S. Procz,et al.  Flatfield Correction Optimization for Energy Selective X-Ray Imaging With Medipix3 , 2011, IEEE Transactions on Nuclear Science.

[22]  O. Zhou,et al.  Zr- and Hf-based nanoscale metal-organic frameworks as contrast agents for computed tomography. , 2012, Journal of materials chemistry.

[23]  Dar-Bin Shieh,et al.  In vitro and in vivo studies of FePt nanoparticles for dual modal CT/MRI molecular imaging. , 2010, Journal of the American Chemical Society.

[24]  Taly Gilat Schmidt,et al.  Region-of-interest material decomposition from truncated energy-resolved CT. , 2011, Medical physics.

[25]  Xiaogang Qu,et al.  Long-circulating Er3+-doped Yb2O3 up-conversion nanoparticle as an in vivo X-Ray CT imaging contrast agent. , 2012, Biomaterials.

[26]  Wenxiang Cong,et al.  Optimization of K-edge imaging with spectral CT. , 2012, Medical physics.

[27]  S. Bartling,et al.  Synthesis and characterization of Bi2O3/HSA core-shell nanoparticles for X-ray imaging applications. , 2013, Journal of biomedical materials research. Part B, Applied biomaterials.

[28]  Sabee Molloi,et al.  Breast composition measurement with a cadmium-zinc-telluride based spectral computed tomography system. , 2012, Medical physics.

[29]  W. Kalender,et al.  Potential of high-Z contrast agents in clinical contrast-enhanced computed tomography. , 2011, Medical physics.

[30]  S. Riederer,et al.  Selective iodine imaging using K-edge energies in computerized x-ray tomography. , 1977, Medical physics.

[31]  E. Roessl,et al.  K-edge imaging in x-ray computed tomography using multi-bin photon counting detectors , 2007, Physics in medicine and biology.

[32]  S. Molloi,et al.  Segmentation and quantification of materials with energy discriminating computed tomography: a phantom study. , 2010, Medical physics.

[33]  Jens Wiegert,et al.  Performance simulation of an x-ray detector for spectral CT with combined Si and Cd[Zn]Te detection layers. , 2010, Physics in medicine and biology.

[34]  L. Gerward,et al.  WinXCom – a program for calculating x-ray attenuation coefficients , 2004 .

[35]  P. Ouvrier-Buffet,et al.  Fast CdTe and CdZnTe Semiconductor Detector Arrays for Spectroscopic X-Ray Imaging , 2013, IEEE Transactions on Nuclear Science.

[36]  A. Popovtzer,et al.  Targeted gold nanoparticles enable molecular CT imaging of cancer: an in vivo study , 2011, International journal of nanomedicine.

[37]  Polad M Shikhaliev,et al.  Projection x-ray imaging with photon energy weighting: experimental evaluation with a prototype detector , 2009, Physics in medicine and biology.

[38]  C. Mistretta,et al.  Noise reduction in spectral CT: reducing dose and breaking the trade-off between image noise and energy bin selection. , 2011, Medical physics.

[39]  Science to practice: can CT be performed for multicolor molecular imaging? , 2010, Radiology.

[40]  Polad M Shikhaliev.  Photon counting spectral CT: improved material decomposition with K-edge-filtered x-rays. , 2012, Physics in medicine and biology.

[41]  Menachem Motiei,et al.  Nanoparticles as computed tomography contrast agents: current status and future perspectives. , 2012, Nanomedicine.

[42]  V. Muzykantov,et al.  Multifunctional Nanoparticles: Cost Versus Benefit of Adding Targeting and Imaging Capabilities , 2012, Science.