Phase Contrast Computed Tomography
X-ray Computed Tomography (CT) is a versatile and widely used medical imaging modality that generates three-dimensional images of the linear x-ray attenuation coefficient. Current CT scanners suffer from a poor contrast-to-noise ratio (CNR) in the soft tissue regime, which demands the additional usage of contrast agent and/or rather high x-ray dose for soft-tissue protocols. There are several strategies being pursued currently in the field to mitigate this issue: Noise can be reduced by using single photon counting detectors, eliminating electronic noise in the imaging chain in the first place. Furthermore, modern iterative reconstruction methods provide an improved CNR by properly accounting for the statistics of the measured data and by more accurate modeling of the CT scanner than traditional analytic reconstruction methods.
Yet another opportunity to improve CNR is the usage of x-ray interferometry that measures the x-ray deflection rather than its attenuation. This approach is generally called phase contrast imaging. Since the first demonstration of the feasibility of using a Talbot-Lau interferometer in the x-ray regime by Franz Pfeiffer in 2006, this technology gained tremendous interest in the x-ray imaging community. Compared to other interferometric methods, it has the main advantage that a conventional x-ray tube can be used, which is a pre-requisite for a wide use in medical imaging. A further advantage is that the method detects simultaneously the deflection, the attenuation, and the loss of coherence of the x-ray beam, thus it provides images of three different tissue properties at the same time.
In this Focus Group, Rudolf Diesel Industry Fellow Dr. Thomas Koehler (Philips Research Laboratories) and his hosts Prof. Franz Pfeiffer (Biomedical Physics) and Prof. Ernst Rummeny (Radiology) investigate the full potential of x-ray phase contrast tomography for medical applications, also in comparison with other forthcoming improvements in CT like the use of energy resolved single photon counting detectors.
Dr. Peter Noël (Diagnostic and Interventional Radiology, University Hospital “Rechts der Isar) as well as doctoral candidates Andreas Fehringer, Wolfgang Noichl and Max von Teuffenbach (all Biomedical Physics, TUM) also work in this Focus Group.
TUM-IAS funded doctoral candidate:
Regine Gradl, Biomedical Physics