Direct quantitative material decomposition employing grating-based X-ray phase-contrast CT

Abstract

Dual-energy CT has opened up a new level of quantitative X-ray imaging for many diagnostic applications. The energy dependence of the X-ray attenuation is the key to quantitative material decomposition of the volume under investigation. This material decomposition allows the calculation of virtual native images in contrast enhanced angiography, virtual monoenergetic images for beam-hardening artifact reduction and quantitative material maps, among others. These visualizations have been proven beneficial for various diagnostic questions. Here, we demonstrate a new method of ‘virtual dual-energy CT’ employing grating-based phase-contrast for quantitative material decomposition. Analogue to the measurement at two different energies, the applied phase-contrast measurement approach yields dual information in form of a phase-shift and an attenuation image. Based on these two image channels, all known dual-energy applications can be demonstrated with our technique. While still in a preclinical state, the method features the important advantages of direct access to the electron density via the phase image, simultaneous availability of the conventional attenuation image at the full energy spectrum and therefore inherently registered image channels. The transfer of this signal extraction approach to phase-contrast data multiplies the diagnostic information gained within a single CT acquisition. The method is demonstrated with a phantom consisting of exemplary solid and fluid materials as well as a chicken heart with an iodine filled tube simulating a vessel. For this first demonstration all measurements have been conducted at a compact laser-undulator synchrotron X-ray source with a tunable X-ray energy and a narrow spectral bandwidth, to validate the quantitativeness of the processing approach.

A compact light source providing high-flux, quasi-monochromatic, tunable X-rays in the laboratory

“…Given the biomedical imaging research focus of the TUM group, a large number of application examples has been generated in this area. 8,[10][11][12][13][14][15][16][17][18][21][22][23][24][25][26][28][29][30][31] While earlier experiments focused on demonstrating different X-ray imaging techniques on the CLS, such as mono-energy X-ray absorption tomography, grating-based multimodal imaging, propagation-based phase contrast and phase contrast tomography, these are now applied to specific biomedical applications and extended to advanced techniques, such as dynamic imaging, K-edge subtraction imaging and others.…”

“…19,20 The MuCLS has been operating with a high degree of uptime since then and has enabled many scientific experiments and publications. [21][22][23][24][25][26][27][28][29][30][31] Generally, most X-ray techniques such as diffraction, imaging, spectroscopy or scattering can be performed with both electron-impact and synchrotron sources. While the details depend on the technique and the specific application needs, generally the following guidelines apply: Longer measurement times Shorter measurement times Lower resolution and sensitivity Higher resolution and sensitivity Suitable where fixed energy or polychromatic beam is acceptable Required where tunability and/or monochromaticity is required Advantageous for large sample sizes (e.g., imaging of large components and low or moderate resolution)…”

Next-Generation Hardware Advances in CT: Cardiac Applications

“…Other applications have leveraged the 10-mm spatial resolution and high soft-tissue contrast. These have included visualizing myocardial fiber orientation (98)(99)(100), identifying the cardiac conduction system (101), visualizing microscopic vascular damage (102), and performing cardiac material decomposition (103). These experimental techniques may enable noninvasive high-resolution imaging of high-risk plaque and identification of subtle myocardial abnormalities in patients with cardiac disease.…”

The versatile X-ray beamline of the Munich Compact Light Source: design, instrumentation and applications

“…Combined with quasi-monochromatic X-rays, GBI allows for quantitative determination of the absorption coefficient as well as the phase shift. The complex refractive index can be reconstructed from this information, which enables quantitative material discrimination (Eggl et al, 2015;Braig et al, 2018). Therefore, this technique can be used for similar purposes as dual-energy imaging, while at the same time providing a reliable differentiation for both low-absorbing material, like soft tissue, as well as strongly absorbing materials, like bone or contrast agents.…”