Radiation dosimetry and biodistribution of the beta-amyloid plaque imaging tracer 11C-BTA-1 in humans

• Published in: Nuclear medicine Vol. 46; no. 5; p. 175
• Main Authors: Thees, S, Neumaier, B, Glatting, G, Deisenhofer, S, von Arnim, C A F, Reske, S N, Mottaghy, F M
• Format: Journal Article
• Language: English
• Published: Germany 2007
• Subjects: Adult; Alzheimer Disease - diagnostic imaging; Amyloid beta-Peptides - analysis; Amyloid beta-Peptides - metabolism; Bone Marrow - diagnostic imaging; Brain - diagnostic imaging; Carbon Radioisotopes; Female; Gallbladder - diagnostic imaging; Heart - diagnostic imaging; Humans; Kidney - diagnostic imaging; Liver - diagnostic imaging; Lung - diagnostic imaging; Male; Positron-Emission Tomography; Reference Values; Tissue Distribution; Urinary Bladder - diagnostic imaging
• ISSN: 0029-5566
• DOI: 10.1160/nukmed-0077

[N-methyl-(11)C]2-(4'-(methylaminophenyl)-benzothiazole ((11)C-BTA-1) is a thioflavin-T derivative that has been one of the promising PET tracers for imaging of amyloid plaque distribution in the Alzheimer patients brain in vivo. The biodistribution and dosimetry of this tracer in humans is presented and compared to the results of a previous dosimetry and biodistribution study of another thioflavin-T derivative [N-methyl-(11)C]2-hydroxy-(4'-(methylaminophenyl)-benzothiazole ((11)C-OH-BTA-1) in baboons.
Five subjects underwent 2D dynamic PET imaging. Source organs were segmented using a semiautomatic algorithm based on clustering. Residence times for each source organ were determined by analytical integration of an exponential fit of the time activity curves. Finally organ doses were estimated using the software OLINDA/EXM.
The administration of 286 +/- 93 MBq (11)C-BTA-1 was well tolerated by all subjects. Effective radiation dose was 4.3 microSv/MBq, range 3.6-5.0 microSv/MBq. In four of the five subjects the liver, in one of the subjects the gallbladder was the critical organ.
The radiation burden of a single dose of 300 MBq (11)C-BTA-1 is within the accepted limits for research purpose. In contrast to the previous non-human primate study revealing the gallbladder as the critical organ for (11)C-6-OH-BTA-1, we found the liver as the critical organ in humans using (11)C-BTA-1. Possible explanations may be (1) a reduced bile concentration of (11)C-BTA-1 due to the absent OH-group or (2) a different hepatic metabolism of thioflavin derivatives in human and baboon.