Improving resolution of MR angiographic projections by bandlimited interpolation of magnitude images

Image interpolation, with its image magnifying abilities, is an image processing operation of increasing importance in the fields of biology and medicine. In this paper, we present a novel image interpolation technique that utilizes the discrete cosine transform (DCT). The DCT provides for a decrease in border effects, and improves the processing speed. The advantages of this technique over the traditional Fourier-transform-based techniques stem from basic properties of DCT that it is a non-periodic, real (non-complex) transform with excellent energy compaction in the transform domain. In fact, the DCT´s energy compaction property is next only to Karhunen-Loeve transform in the mean squared sense on an ensemble of images (Jain, 1989). In addition, DCT allows interpolation of small volumes (e.g., 8×8×8) which is not easily possible with an FFT-based method. Therefore, the present technique is better suited for applications such as a real-time 3D interactive maximum intensity projection, real-time 2-D image magnifier etc. More importantly, the technique can be used for the bandlimited interpolation of any digitally acquired data to minimize partial voluming artifact