Establishing Test–Retest Reliability of an Adapted [18F]Fallypride Imaging Protocol in Older People

Abstract

[ 18 F]fallyprlde is a high-affinity dopamine D2/3 receptor tracer with the ability to reliably quantify D2/3 receptor sites in both striatal and corticolimbic regions. The translational potential of [ 18 F]fallypride imaging is, however, limited by the lengthy scanning sessions (60–80 minutes duration over a total of 3–4 hours) required by current protocols. The aims of our study were to adapt [ 18 F]fallypride imaging for use in clinical populations with neurological and neuropsychiatric disorders, by reducing the duration of individual scanning sessions;and to establish the reproducibility and reliability of our adapted protocol in healthy older people. Eight participants (five male and three female;mean age = 75.87 ± 4.39 years) were scanned twice, 4–6 weeks apart. [ 18 F]fallypride binding potential was determined from image data collected during three sampling times: 0-30;60-90;and 210–240 minutes post injection. High reproducibility and reliability (test-retest variability <8%;intraclass correlation coefficient >0.8) were observed in all but the prefrontal regions, and remained so when sampling times were reduced to 20 minutes (0-20;70-90;220-240 minutes). The adapted protocol is feasible for use across neuropsychiatric disorders in which dopamine has been implicated and is sufficiently sensitive to detect within-subject changes between 2.7% and 5.5% in striatal and limbic regions.