Determination of tissue attenuation in emission tomography of optically dense media

In emission tomography of optically dense media one is faced with the problem of determining the attenuation distribution which must be taken into account when setting up the equations from which the activity distribution is computed. We describe a method for computing the attenuation distribution from the emission data. We assume that the true attenuation distribution is approximately an affine distortion of a known prototype attenuation distribution.