Element-specific spectral imaging of multiple contrast agents: a phantom study

Abstract

This work demonstrates the feasibility of simultaneous discrimination of multiple contrast agents based on their element-specific and energy-dependent X-ray attenuation properties using a pre-clinical photon-counting spectral CT. We used a photon-counting based pre-clinical spectral CT scanner with four energy thresholds to measure the X-ray attenuation properties of various concentrations of iodine (9, 18 and 36 mg/ml), gadolinium (2, 4 and 8 mg/ml) and gold (2, 4 and 8 mg/ml) based contrast agents, calcium chloride (140 and 280 mg/ml) and water. We evaluated the spectral imaging performances of different energy threshold schemes between 25 to 82 keV at 118 kVp, based on K-factor and signal-to-noise ratio and ranked them. K-factor was defined as the X-ray attenuation in the K-edge containing energy range divided by the X-ray attenuation in the preceding energy range, expressed as a percentage. We evaluated the effectiveness of the optimised energy selection to discriminate all three contrast agents in a phantom of 33 mm diameter. A photon-counting spectral CT using four energy thresholds of 27, 33, 49 and 81 keV at 118 kVp simultaneously discriminated three contrast agents based on iodine, gadolinium and gold at various concentrations using their K-edge and energy-dependent X-ray attenuation features in a single scan. A ranking method to evaluate spectral imaging performance enabled energy thresholds to be optimised to discriminate iodine, gadolinium and gold contrast agents in a single spectral CT scan. Simultaneous discrimination of multiple contrast agents in a single scan is likely to open up new possibilities of improving the accuracy of disease diagnosis by simultaneously imaging multiple bio-markers each labelled with a nano-contrast agent.

Assessment of Material Identification Errors, Image Quality, and Radiation Doses Using Small Animal Spectral Photon-Counting CT

“…Bateman et al [4] also reported similar observations. However, we have not encountered similar problem of Perspex being misidentified with other high-Z elements, such as iodine and gold in one of our earlier studies [40]. The other reason could be around the similarities in the elemental composition that is The spatial accuracy obtained in our study was consistent to that of previously reported studies using similar image acquisition and MD methods [12], [16].…”

X-ray computed tomography in life sciences

“…Lab-based spectral imaging systems incorporating photon-counting energy-resolving detectors are now available. These are able to assign photons to a small number of energy thresholds per pixel and can thus distinguish multiple stains simultaneously [72]. The logical extension of this approach is hyperspectral CT using an energy-sensitive detector to record the full X-ray energy profile at each pixel [73].…”

Multifiller nanocomposites containing gadolinium oxide and bismuth nanoparticles with enhanced X‐ray attenuation property

“…The enhancement in X-ray attenuation property of A13 nanocomposite is also attributed to the presence of heavy atoms such as Bi and Gd which exhibit a K-absorption edge or K-edge effect (defined as an increase in photoelectric absorption which occurs when the energy of incoming X-ray photons matches with the binding energy of K-shell electrons in an atom) at 90.5 and 50.2 keV X-ray photon energy, respectively. 70,71 The dual K-edge effect observed in A13 nanocomposite greatly enhances its X-ray attenuation property in the diagnostic range. Figure 10(f) shows the radiograph image of polymer-Bi 2 O 3 -Bi nanocomposite (A7), with less number of pin-holes.…”