TACR1 and Alzheimer disease: Previous studies, such as longitudinal measurements of amyloid load in Alzheimer’s disease (AD) patients (van Berckel et al., 2013) and neurokinin-1 receptor status after the administration of an agonist (Wolfensberger et al., 2011), have illustrated the difference between measuring tracer uptake semi-quantitatively and measuring a pathophysiologic process quantitatively (Lammertsma, 2017).