Automatic Extraction of Caudate and Putamen in [$^11$C] Raclopride PET Using Deformable Surface Models and Normalized Cuts

Abstract

Manual region-of-interest (ROI) definition is the conventional basis for calculating regional receptor binding potential (BP) values in neuroreceptor PET studies. In this study, we propose a fully automatic method to extract the left and right caudate and putamen in [ $^11$ C]raclopride BP images. The automatic extraction of these brain structures is challenging due to the small size of the structures compared to the imaging resolution and image noise. The automation of the ROI extraction could remedy the problems relating to intra- and inter-observer variability introduced by the manual ROI drawing. We compared our method to the manual ROI drawing. The automatic ROI extraction improved test-retest reproducibility of the calculated BP values compared to the manual ROI drawing. In addition, the method was tested on a Monte Carlo simulated PET image. In this experiment, the automatic method yielded more accurate BP values than those computed based on the anatomical ground-truth and manual ROI extraction. Hence, our method for the automatic ROI extraction is reliable and it can simplify and speed up the analysis of large sets of PET scans e.g., in drug development studies.