Computed tomographic x-ray velocimetry

Abstract

An x-ray velocimetry technique is described which provides three components of velocity measurement in three dimensional space. Current x-ray velocimetry techniques, which use particle images taken at a single projection angle, are limited to two components of velocity measurement, and are unable to measure in three dimensions without a priori knowledge of the flow field. The proposed method uses multiple projection angles to overcome these limitations. The technique uses a least-squares iterative scheme to tomographically reconstruct the three-dimensional velocity field directly from two-dimensional image pair cross-correlations, without the need to reconstruct three-dimensional particle images. Synchrotron experiments demonstrate the effectiveness of the technique for blood flow measurement in opaque vessels, with applications for the diagnosis and treatment of cardiovascular disease.

Synchrotron-based dynamic computed tomography of tissue motion for regional lung function measurement

“…An alternative approach for tissue displacement measurement may also be used, in which a single CT scan is acquired as a morphological reference, and tissue velocity is measured using the method recently developed by the authors-computed tomographic X-ray velocimetry (CTXV) [35,36]. This approach is capable of providing accurate tissue displacement information from a very low number of projections, with significant reductions in radiation dose imparted to the sample.…”

“…An alternative velocimetry approach, CTXV [35,36] has been recently developed by the authors, which is capable of providing accurate motion measurement from very few projections. The combination of CTXV with future developments in clinical phase-contrast X-ray imaging [24,55] could provide similar measurements to those presented in this paper, with significantly reduced dose levels over current four-dimensional-CT methods.…”

Note: Development of a compact x-ray particle image velocimetry for measuring opaque flows. II. Three-dimensional velocity field reconstruction

“…The same approach was employed in previous studies on 3D velocity field reconstruction. 7,8 The projected velocity vector is calculated at each pixel node of the interrogation region P i , expressed in terms of a weighting matrix W ij as follows:…”

“…Recently, a tomographic x-ray PIV technique was developed using multiple projected cross-correlation functions at several angles to measure the three-dimensional (3D) velocity field information of opaque flows without any constraints. 7,8 In addition, another 3D x-ray velocimetry technique was developed to measure unsteady flows using a Laue crystal as an x-ray beam splitter and reflection mirror. 9 In the present study, an x-ray tomographic PIV technique employing a compact cone-beam type x-ray tube was developed to measure 3D velocity field information on opaque flows from 2D projected velocity fields without reconstructing 3D particle images.…”

Computed Tomographic X-ray Velocimetry

“…The use of multiple projection angles to overcome this limitation has been suggested [12,16,18], however no implementation of this concept has appeared in the literature. We have developed an X-ray PIV technique that uses data obtained from multiple viewing angles for tomographic reconstruction of the 3D flow-field [19]. The technique, computed tomographic X-ray velocimetry (CTXV), combines phase-contrast X-ray imaging with PIV and computed tomography (CT).…”