title: Test-retest reproducibility of [(11)C]PBR28 binding to TSPO in healthy control subjects.
abstract: OBJECTIVE
  The PET radioligand [(11)C]PBR28 binds to the translocator protein (TSPO), a marker of brain immune activation. We examined the reproducibility of [(11)C]PBR28 binding in healthy subjects with quantification on a regional and voxel-by-voxel basis. In addition, we performed a preliminary analysis of diurnal changes in TSPO availability.
  
  
  METHODS
  Twelve subjects were examined using a high-resolution research tomograph and [(11)C]PBR28, six in the morning and afternoon of the same day, and six in the morning on two separate days. Regional volumes of distribution (V T) were derived using a region-of-interest based two-tissue compartmental analysis (2TCM), as well as a parametric approach. Metabolite-corrected arterial plasma was used as input function.
  
  
  RESULTS
  For the whole sample, the mean absolute variability in V T in the grey matter (GM) was 18.3 ± 12.7 %. Intraclass correlation coefficients in GM regions ranged from 0.90 to 0.94. Reducing the time of analysis from 91 to 63 min yielded a variability of 16.9 ± 14.9 %. There was a strong correlation between the parametric and 2TCM-derived GM values (r = 0.99). A significant increase in GM V T was observed between the morning and afternoon examinations when using secondary methods of quantification (p = 0.028). In the subjects examined at the same time of the day, the absolute variability was 15.9 ± 12.2 % for the 91-min 2TCM data.
  
  
  CONCLUSIONS
  V T of [(11)C]PBR28 binding showed medium reproducibility and high reliability in GM regions. Our findings support the use of parametric approaches for determining [(11)C]PBR28 V T values, and indicate that the acquisition time could be shortened. Diurnal changes in TSPO binding in the brain may be a potential confounder in clinical studies and should be investigated further.
authors: Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet, Stockholm, Sweden. karin.collste@ki.se.
authors: K
authors: K
authors: Collste
authors: Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet, Stockholm, Sweden.
authors: A
authors: A
authors: Forsberg
authors: Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet, Stockholm, Sweden.
authors: A
authors: A
authors: Varrone
authors: Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet, Stockholm, Sweden.
authors: N
authors: N
authors: Amini
authors: Department of Clinical Neuroscience, Neuroimmunology Unit, Karolinska Institutet, Stockholm, Sweden.
authors: S
authors: S
authors: Aeinehband
authors: Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet, Stockholm, Sweden.|Department of Nuclear Medicine and TUM Neuroimaging Center (TUM-NIC), Technische Universität München, Munich, Germany.
authors: I
authors: I
authors: Yakushev
authors: Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet, Stockholm, Sweden.
authors: C
authors: C
authors: Halldin
authors: Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet, Stockholm, Sweden.
authors: L
authors: L
authors: Farde
authors: Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet, Stockholm, Sweden.
authors: S
authors: S
authors: Cervenka
mesh_terms: D002250:Carbon Radioisotopes; D005260:Female; D005838:Genotype; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D011485:Protein Binding; D011743:Pyrimidines / Q000378:metabolism*; D018079:Receptors, GABA / Q000235:genetics / Q000378:metabolism*; D015203:Reproducibility of Results; D055815:Young Adult
chemical_list: C526315:(methyl-(11)C)N-acetyl-N-(2-methoxybenzyl)-2-phenoxy-5-pyridinamine; D002250:Carbon Radioisotopes; D011743:Pyrimidines; D018079:Receptors, GABA; C499229:TSPO protein, human
keywords: 11C; Brain imaging; PBR28; PET; Test–retest