The watershed algorithm: A method to segment noisy PET transmission images

Attenuation correction is essential to PET imaging but often requires impra ctical acquisition times. Segmentation of short noisier transmission scans has been proposed as a solution. We report that a 3D morphological tool - t he watershed algorithm - is well adapted for segmenting even 2-minute PET t ransmission images. The technique is noniterative, fast, and fully 3-D. It inherently ensures class continuity and eliminates outliers. Pre-filtering the data induced smoother class edges, showing that a multi-resolution appr oach could be used to deal with partial volume effect and excessive noise i n the data. The algorithm was tested on 2-minute scans of a torso phantom a nd on a human study.