Texture analysis of differently reconstructed PET images.

The insufficient number of projections and the statistics of radioactive decay are supposed to lead to different textures in the images reconstructed by the diverse algorithms used in positron emission tomography (PET). In our study, four reconstruction methods were examined, including the filtered backprojection and three algebraic approaches. Grey-level morphological operators were used to extract the texture. To quantify the observations, we used the texture parameters directionality, fractal dimension, and lacunarity. By increasing the number of iteration steps, each of the algebraic reconstruction methods evolve the texture from coarse to fine granularities, but surprisingly, during the iteration process all methods follow a quite similar 'trail' of possible textures within the active zone. The texture of the termination points of the movement have been compared with the result that the 'hils' and 'valleys' of the activity distribution are located in the same positions. The texture derived from the filtered backprojection is included in the set of textures produced by the algebraic methods. Artefacts are restricted to zones without activity. We found that the texture is independent of the number of counts when more than ten counts are registered in each pixel within the examined region of interest. A high reliability in the reconstructed images is given. All methods allow texture based tissue classification.