3D attenuation correction in PET

The performance of attenuation measurements has been investigated, using coincidence detection in fully 3D PET, and has been compared to current attenuation methods. The current methods acquire coincidence data in 2D mode (with septa extended in the field-of-view). While this method reduces the contribution of random and scatter coincidence events to the attenuation scan, it does not make full use of the sensitivity of the scanner. Using low activity rods and a novel rotating point source, attenuation data has been analysed in 2D and 3D. The PROMIS 3D reconstruction algorithm, currently uses 2D attenuation maps, via a back/forward-projection method, to correct 3D emission datasets. The authors describe a fully 3D technique using measured 3D attenuation maps applied directly to the 3D emission datasets. The accuracy and quality of reconstructed images has been examined using both forward-projected 2D and measured 3D attenuation maps. The 3D transmission method was found to reduce reconstruction time with no noticeable loss of image quality.