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

Attenuation correction is essential to PET imaging but often requires impractical acquisition times. Segmentation of short noisier transmission scans has been proposed as a solution. We report that a 3D morphological tool - the watershed algorithm - is well adapted for segmenting even 2-minute PET transmission 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 approach could be used to deal with partial volume effect and excessive noise in the data. The algorithm was tested on 2-minute scans of a torso phantom and on a human study.