RT Journal Article
SR Electronic
T1 Comparison of two radioligands for PET imaging of translocator protein in human brain: <sup>11</sup>C-PBR28 and <sup>18</sup>F-PBR06
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 554
OP 554
VO 51
IS supplement 2
A1 Leah Dickstein
A1 Sami Zoghbi
A1 Yota Fujimura
A1 Masao Imaizumi
A1 Yi Zhang
A1 Victor Pike
A1 Robert Innis
A1 Masahiro Fujita
YR 2010
UL http://jnm.snmjournals.org/content/51/supplement_2/554.abstract
AB 554 Objectives Translocator protein (TSPO) is over expressed in activated microglia and is, therefore, a marker for neuroinflammation. The purpose of this study was to assess the relative utility of two new PET radioligands developed in our lab, 11C-PBR28 and 18F-PBR06. Methods Eight healthy humans had PET brain scans with both 11C-PBR28 and 18F-PBR06. Using metabolite-corrected arterial input function and an unconstrained two-compartment model, total distribution volume VT was measured in ten regions. Because only free ligand enters the brain, VT was normalized to plasma free fraction, fP. Correlation for VT/fP of 11C-PBR28 and 18F-PBR06 was examined because the slope of the correlation is determined by the in vivo affinities of these ligands. Results VT was well identified for both of these ligands with standard errors &lt; 5%. 11C-PBR28 showed greater VT than 18F-PBR06 (4.2 ± 1.0 vs. 2.1 ± 0.4 cm3/mL, p &lt; .001). However, 11C-PBR28 also showed greater fP (4.4 ± 1.1 vs. 2.2 ± 0.6%, p &lt; .001). After normalizing VT to fP to reflect true binding levels, 11C-PBR28 and 18F-PBR06 showed similar VT/fP. In ten regions, VT/fP values of the two ligands were significantly correlated (r = 0.92, p &lt; .0005), indicating that the binding to TSPO was consistently measured by each ligand. Furthermore, a linear plot of VT/fP in ten regions yielded a slope close to unity, indicating that the two ligands have similar affinities. When VT was calculated with various length of data, both of these ligands showed greater VT values with longer length, which is compatible with the presence of radiometabolites entering the brain. VT of 18F-PBR06 showed smaller dependency on the data length. Conclusions 11C-PBR28 and 18F-PBR06 were comparable in terms of in vivo affinity and identifiability of VT. 18F-PBR06 has advantages because of possibly smaller influence of radiometabolites on the binding measurement and the longer half-life to allow distribution to other PET centers. Research Support project #Z01-MH-002795-07, #Z01-MH-002793-0