Automatic delineation algorithm of reference region for amyloid imaging based on kinetics

This study aims to develop an algorithm named AutoRef to delineate a reference region for quantitative PET amyloid imaging.

AutoRef sets the reference region automatically using a distinguishing feature in the kinetics of reference region. This is reflected in the shapes of the tissue time activity curve. A statistical shape recognition algorithm of the gaussian mixture model is applied with considering spatial and temporal information on a reference region. We evaluate the BP_ND with manually set reference region and AutoRef using 86 cases (43 positive cases, 10 equivocal cases, and 33 negative cases) of dynamically scanned ¹¹C-Pittsburgh Compound-B.

From the Bland-Altman plot, the difference between two BP_ND is 0.099 ± 0.21 as standard deviation, and no significant systematic error is observed between the BP_ND with AutoRef and with manual definition of a reference region. Although a proportional error is detected, it is smaller than the 95% limits of agreement. Therefore, the proportional error is negligibly small.

AutoRef presents the same performance as the manual definition of the reference region. Further, since AutoRef is more algorithmic than the ordinary manual definition of the reference region, there are few operator-oriented uncertainties in AutoRef. We thus conclude that AutoRef can be applied as an automatic delineating algorithm for the reference region in amyloid imaging.