Human Dosimetry of the <i>N</i>-Methyl-d-Aspartate Receptor Ligand ¹¹C-GMOM.

Abstract

The methylguanidine derivative ¹¹C-GMOM (¹¹C-labeled <i>N</i>-(2-chloro-3-thiomethylphenyl)-<i>N</i>'-(3-methoxyphenyl)-<i>N</i>'-methylguanidine) has been used successfully to quantify <i>N</i>-methyl-d-aspartate (NMDA) receptor binding in humans. The purpose of the present study was to estimate the ¹¹C-GMOM radiation dose in healthy humans. <b>Methods:</b> After ¹¹C-GMOM injection, 3 female and 2 male subjects underwent 10 consecutive whole-body PET scans in approximately 77 min. Seven source organs were defined manually, scaled to a sex-specific reference, and residence times were calculated for input into OLINDA/EXM software. Accepted tissue-weighting factors were used to calculate the effective dose. <b>Results:</b> The mean absorbed radiation doses in source organs ranged from 7.7 μGy·MBq^-1 in the brain to 12.7 μGy·MBq^-1 in the spleen. The effective dose (±SD) was 4.5 ± 0.5 μSv·MBq^-1<b>Conclusion:</b> The effective dose of ¹¹C-GMOM is at the lower end of the range seen for other ¹¹C-labeled ligands, allowing for serial PET scanning in a single subject.