A new method is presented for obtaining an analytical solution to the image-reconstruction problem in single-photon-emission computed tomography. The rigorous solution is introduced by applying an analytical continuation process to the two-dimensional Fourier transform of the image, which is derived from the one-dimensional Fourier transforms of projection functions. The calculations can be carried out in a short computation time without involving unstable procedures. Numerical simulations were made to demonstrate the effectiveness of the proposed method.
The relationship between magnetic resonance (MR) relaxation times and muscle fiber composition was investigated in 16 men, and a high positive correlation was found. Higher proportions of fast-twitch fiber were associated with longer relaxation times, indicating that fast-twitch fiber has a longer relaxation time than slow-twitch fiber. Multiple regression analysis, conducted to investigate the suitability of relaxation time as a model of estimating muscle fiber composition, revealed that T1 and T2 were significantly related to muscle fiber composition. These results indicate that MR relaxation time may be used to estimate muscle fiber composition.
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