  Positron Emission Mammography (PEM) imaging systems with the ability in
detection of millimeter-sized tumors were developed in recent years. And some
of them have been well used in clinical applications. In consideration of
biopsy application, a double-plane detector configuration is practical for the
convenience of breast immobilization. However, the serious blurring effect in
the double-plane system with changeable spacing for different breast size
should be studied. Methods: We study a high resolution reconstruction method
applicable for a double-plane PET system with a changeable detector spacing.
Geometric and blurring components should be calculated at real time for
different detector distance. Accurate geometric sensitivity is obtained with a
tube area model. Resolution recovery is achieved by estimating blurring effects
derived from simulated single gamma response information. Results: The results
show that the new geometric modeling gives a more finite and smooth sensitivity
weight in double-plane system. The blurring component yields contrast recovery
levels that could not be reached without blurring modeling, as well as better
visual recovery of the smallest spheres and better delineation of the
structures in the reconstructed images. Statistical noise has lower variance at
the voxel level with blurring modeling than without at matched resolution.
Conclusion: In the distance-changeable double-plane PET, the finite resolution
modeling during reconstruction achieves resolution recovery, without noise
amplification.
