Accurate attenuation correction in PET without accurate transmission measurements

In this study the authors use the consistency conditions of the Radon transform to aid attenuation correction in PET. The conditions are used both for estimating the boundary of a uniform attenuation distribution (without any transmission measurements) and for correcting for patient motion between the transmission and emission acquisitions. The results show that, for a uniform elliptical attenuation distribution, the image reconstructed with an attenuation distribution estimated using the consistency conditions is almost indistinguishable from an image reconstructed using the true attenuation coefficient map. The method is shown to be fairly tolerant to the effects of photon counting statistics and to small non-uniformities in the attenuation distribution (such as skull attenuation). The results also show that the consistency conditions may be useful in correcting for patient motion. The method is shown to accurately compensate for shifts in two dimensions using both simulated and experimental data.