SPECT of serotonin transporters using 123I-ADAM: optimal imaging time after bolus injection and long-term test-retest in healthy volunteers.
(123)I-ADAM (2-([2-([dimethylamino]methyl)phenyl]thio)-5-(123)I-iodophenylamine) has been recently proposed as a new serotonin transporter (SERT) ligand for SPECT. The objective of this study was to characterize (123)I-ADAM in healthy volunteers. (123)I-ADAM distribution in the normal brain, pseudoequilibrium interval after a single injection, normal specific uptake values, and long-term test-retest variability and reliability were investigated.


METHODS
Ten healthy volunteers underwent 2 SPECT sessions under the same conditions 47.6 +/- 24.0 d apart. Scans were sequentially acquired from the time of (123)I-ADAM intravenous injection up to 12 h after injection. Regions of interest (ROIs) for cerebellum (C), midbrain, thalamus, striatum, mesial temporal region, and cortex were drawn on MR images and pasted to corresponding SPECT slices after coregistration. Specific uptake ratios (SURs) at pseudoequilibrium and the simplified reference tissue model (SRTM) methods were used for quantification. SURs were obtained as ([region - C]/C) at each time point. Test-retest variability and reliability (intraclass correlation coefficient [ICC]) were calculated.


RESULTS
The highest (123)I-ADAM specific uptake was found in the midbrain and thalamus, followed by the striatum and mesial temporal region. Quantification results using SUR and SRTM were correlated with R = 0.93 (test) and R = 0.94 (retest). SURs remained stable in all regions from 4 to 6 h after injection. Using SUR, test-retest variability/ICC were 13% +/- 11%/0.74 in midbrain, 16% +/- 13%/0.63 in thalamus, 19% +/- 18%/0.62 in striatum, and 22% +/- 19%/0.05 in mesial temporal region.


CONCLUSIONS
(123)I-ADAM accumulates in cerebral regions with high known SERT density. The optimal imaging time for (123)I-ADAM SPECT quantification is suggested to be from 4 to 6 h after a single injection. Long-term test-retest variability and reliability found in the midbrain are comparable to that reported with other (123)I-labeled SPECT ligands. These results support the use of (123)I-ADAM SPECT for SERT imaging after a single injection in humans.
Catafau
Ana M
AM
Centre for Imaging in Psychiatry, CRC-Mar, Hospital del Mar, Barcelona, Spain. ana.m.catafau@gsk.com
Pérez
Víctor
V
Penengo
María M
MM
Bullich
Santiago
S
Danús
Mónica
M
Puigdemont
Dolors
D
Pascual
Juan C
JC
Corripio
Iluminada
I
Llop
Jordi
J
Perich
Javier
J
Alvarez
Enric
E
D000328:Adult; D000368:Aged; D001921:Brain / Q000000981:diagnostic imaging* / Q000378:metabolism*; D002928:Cinanserin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007275:Injections, Intravenous; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D019275:Radiopharmaceuticals / Q000008:administration & dosage / Q000493:pharmacokinetics; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D050486:Serotonin Plasma Membrane Transport Proteins; D013997:Time Factors; D014018:Tissue Distribution; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
C413491:2-((2-((dimethylamino)methyl)phenyl)thio)-5-iodophenylamine; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D019275:Radiopharmaceuticals; C493230:SLC6A4 protein, human; D050486:Serotonin Plasma Membrane Transport Proteins; D002928:Cinanserin