Multicolour imaging with spectral photon-counting CT: a phantom study

Abstract

BackgroundTo evaluate the feasibility of multicolour quantitative imaging with spectral photon-counting computed tomography (SPCCT) of different mixed contrast agents.MethodsPhantoms containing eleven tubes with mixtures of varying proportions of two contrast agents (i.e. two selected from gadolinium, iodine or gold nanoparticles) were prepared so that the attenuation of each tube was about 280 HU. Scans were acquired at 120 kVp and 100 mAs using a five-bin preclinical SPCCT prototype, generating conventional, water, iodine, gadolinium and gold images. The correlation between prepared and measured concentrations was assessed using linear regression. The cross-contamination was measured for each material as the root mean square error (RMSE) of its concentration in the other material images, where no signal was expected. The contrast-to-noise ratio (CNR) relative to a phosphate buffered saline tube was calculated for each contrast agent.ResultsThe solutions had similar attenuations (279 ± 10 HU, mean ± standard deviation) and could not be differentiated on conventional images. However, a distinction was observed in the material images within the same samples, and the measured and prepared concentrations were strongly correlated (R2 ≥ 0.97, 0.81 ≤ slope ≤ 0.95, -0.68 ≤ offset ≤ 0.89 mg/mL). Cross-contamination in the iodine images for the mixture of gold and gadolinium contrast agents (RMSE = 0.34 mg/mL) was observed. CNR for 1 mg/mL of contrast agent was better for the mixture of iodine and gadolinium (CNRiodine = 3.20, CNRgadolinium = 2.80) than gold and gadolinium (CNRgadolinium = 1.67, CNRgold = 1.37).ConclusionsSPCCT enables multicolour quantitative imaging. As a result, it should be possible to perform imaging of multiple uptake phases of a given tissue/organ within a single scan by injecting different contrast agents sequentially.

The Effects of Spectral X-Ray Photon Counting Detector Parameters on Detector Performance: Thickness and Pitch

“…By using multiple energy thresholds, an xray photon counting spectral imaging (x-CSI) approach can be used, whereby the spectral overlap between low and high energy bins is greatly reduced, and far more energy bins can be reconstructed (up to 8 in some implementations [5]) compared with the 2 in dual energy set-ups. This allows for a range of benefits, including better material decomposition [6], soft tissue contrast, and lower flux rates to be achieved for a given image quality [7].…”

Feasibility of unconstrained three-material decomposition: imaging an excised human heart using a prototype silicon photon-counting CT detector

“…We have in previous publications shown that decomposition into more than two basis materials is feasible in phantom studies with this detector [20,21]. This has also been demonstrated with other PCDs with phantoms [26][27][28][29][30][31], anatomical specimens [27,28,32], and animal models [33,34]. The purpose of this work is to provide proof of concept that unbiased three-material decomposition with iodine can be achieved in a clinical specimen with human tissue with an experimental photon-counting silicon detector in a bench-top setup.…”

Basic principles and clinical potential of photon-counting detector CT

“…Using a custom-made colon phantom filled with iodine and a gadolinium-filled capsule representing a contrast-enhanced polyp, Muenzel et al [34] demonstrated that differentiation between gadolinium-tagged polyps and iodine-tagged fecal material should be possible. Mixtures of iodine, gadolinium, and gold nanoparticles could be differentiated, as well [49]. The authors concluded that it might be possible to perform the imaging of multiple uptake phases in an organ with a single scan by injecting several contrast agents sequentially.…”