For certain medical applications resampling of data is required. In magnetic resonance tomography (MRT) or computer tomography (CT), e.g., data may be sampled on nonrectilinear grids in the Fourier domain. For the image reconstruction a convolution-interpolation algorithm, often called gridding, can be applied for resampling of the data onto a rectilinear grid. Resampling of data from a rectilinear onto a nonrectilinear grid are needed, e.g., if projections of a given rectilinear data set are to be obtained. In this paper we introduce the application of the convolution interpolation for resampling of data from one arbitrary grid onto another. The basic algorithm can be split into two steps. First, the data are resampled from the arbitrary input grid onto a rectilinear grid and second, the rectilinear data is resampled onto the arbitrary output grid. Furthermore, we like to introduce a new technique to derive the sampling density function needed for the first step of our algorithm. For fast, sampling-pattern-independent determination of the sampling density function the Voronoi diagram of the sample distribution is calculated. The volume of the Voronoi cell around each sample is used as a measure for the sampling density. It is shown that the introduced resampling technique allows fast resampling of data between arbitrary grids. Furthermore, it is shown that the suggested approach to derive the sampling density function is suitable even for arbitrary sampling patterns. Examples are given in which the proposed technique has been applied for the reconstruction of data acquired along spiral, radial, and arbitrary trajectories and for the fast calculation of projections of a given rectilinearly sampled image.

The purpose of this study was to investigate whether spectral computed tomography (CT) has the potential to improve luminal depiction by differentiating among intravascular gadolinium-based contrast agent, calcified plaque, and stent material by using the characteristic k edge of gadolinium. A preclinical spectral CT scanner with a photon-counting detector and six energy threshold levels was used to scan a phantom vessel. A partially occluded stent was simulated by using a calcified plaque isoattenuated to a surrounding gadolinium chelate solution. The reconstructed images showed an effective isolation of the gadolinium with subsequent clear depiction of the perfused vessel lumen. The calcified plaque and the stent material are suppressed.