Automated 3-D Segmentation of Respiratory-Gated PET Transmission Images

As a preliminary step toward performing respiration compensated attenuation correction of respiratory-gated cardiac PET data, we acquired and automatically segmented respiratory-gated transmission data for a dog breathing on its own under gas anesthesia. Transmission data were acquired for 20 min on a CTI/Siemens ECAT EXACT HR (47-slice) scanner. Two respiratory gates were obtained using data from a pneumatic bellows placed around the dog’s chest. For each respiratory gate, torso and lung surfaces were segmented automatically using a differential 3-D image edge detection algorithm. Three-dimensional visualizations showed that during inspiration the heart translated about 4 mm transversely and the diaphragm translated about 9 mm inferiorly. The observed respiratory motion of the canine heart and diaphragm suggests that respiration compensated attenuation correction may be necessary for accurate quantitation of high-resolution respiratory-gated human cardiac PET data. Our automated image segmentation results suggest that respiration compensated segmented attenuation correction may be possible using respiratory-gated transmission data obtained with as little as 3 min of acquisition time per gate.