Phase-sensitive x-ray imaging promises unprecedented soft-tissue contrast and resolution. However, several practical challenges have to be overcome when using the setup in a clinical environment. The system design that is currently closest to clinical use is the grating-based Talbot-Lau interferometer (GBI).1-3
The requirements for patient imaging are low patient dose, fast imaging time, and high image quality. For GBI, these requirements can be met most successfully with a narrow energy width, high- ux spectrum. Additionally, to penetrate a human-sized object, the design energy of the system has to be well above 40 keV. To our knowledge, little research has been done so far to investigate optimal GBI filtration at such high x-ray energies.
In this paper, we study different filtration strategies and their impact on high-energy GBI. Specifically, we compare copper filtration at low peak voltage with equal-absorption, equal-imaging time K-edge filtration of spectra with higher peak voltage under clinically realistic boundary conditions. We specifically focus on a design energy of 59 keV and investigate combinations of tube current, peak voltage, and filtration that lead to equal patient absorption. Theoretical considerations suggest that the K edge of tantalum might provide a transmission pocket at around 59 keV, yielding a well-shaped spectrum. Although one can observe a slight visibility benefit when using tungsten or tantalum filtration, experimental results indicate that visibility benefits most from a low x-ray tube peak voltage.
Recent studies have found correlation between the risk of rupture of saccular aneurysms and their morphological
characteristics, such as volume, surface area, neck length, among others. For reliably exploiting these parameters
in endovascular treatment planning, it is crucial that they are accurately quantified. In this paper, we present
a novel framework to assist physicians in accurately assessing saccular aneurysms and efficiently planning for
endovascular intervention. The approach consists of automatically segmenting the pathological vessel, followed
by the construction of its surface representation. The aneurysm is then separated from the vessel surface
through a graph-cut based algorithm that is driven by local geometry as well as strong prior information. The
corresponding healthy vessel is subsequently reconstructed and measurements representing the patient-specific
geometric parameters of pathological vessel are computed. To better support clinical decisions on stenting and
device type selection, the placement of virtual stent is eventually carried out in conformity with the shape of the
diseased vessel using the patient-specific measurements. We have implemented the proposed methodology as a
fully functional system, and extensively tested it with phantom and real datasets.
Endovascular treatment planning of intracranial aneurysms requires accurate quantification of their geometric
parameters, including the neck length, dome height and maximum diameter. Today, the geometry of intracranial
aneurysms is typically quantified manually based on three-dimensional (3D) Digital Subtraction Angiography
(DSA) images. Since the repeatability of manual measurements is not guaranteed and their accuracy is dependent
on the experience of the treating physician, we propose a semi-automated approach for computer-aided
measurement of these parameters. In particular, a tubular deformable model, initialized based on user-provided
points, is first fit to the surface of the parent artery. An initial estimate of the aneurysmal segment is obtained
based on differences between the two surfaces. A 3D deformable contour model is then used to localize the
aneurysmal neck and to separate its dome surface from the parent artery. Finally, approaches for estimation of
the clinically relevant geometric parameters are applied based on the aneurysmal neck and dome surface. Results
on 19 3D DSA datasets of saccular aneurysms indicate that, for the maximum diameter, the standard deviation
of the difference between the proposed approach and two independent manual sets of measurements obtained by
expert readers is similar to the inter-rater standard deviation. For the neck length and dome height, the results
improve considerably if we exclude datasets with high deviation from the manual measurements.
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