Biodistribution and radiation dosimetry of 11C-harmine in baboons.
OBJECTIVE
Monoamine oxidase A is a mitochondrial enzyme which is responsible for the metabolism of catecholamines such as dopamine, norepinephrine, as well as serotonin. This study describes the biodistribution and dosimetry of 11C-harmine, a tracer designed to specifically bind to monoamine oxidase A for positron emission tomography imaging.


METHODS
Three baboon studies were acquired using a Seimens ECAT camera. Dynamic whole-body emission scans were collected in two-dimensional mode over a 2 h period after 223-255 MBq of 11C-harmine was injected. Regions of interest were drawn on transmission corrected images to encompass the entire activity in visible organs at each time point. Time-activity data were used to obtain residence times and absorbed radiation dose to various organs and to the entire body.


RESULTS
Tracer uptake was greatest in the lungs, followed by kidney, small intestine, liver and brain. The largest absorbed dose based on averaged residence times was found in the lungs (reference adult/female 3.99x10(-2)/5.03x10(-2) mSv x MBq(-1)).


CONCLUSIONS
The lungs are the critical organs for administration of 11C-harmine. For example, in the United States, the absorbed dose to the lungs would limit a single 11C-harmine administration for a research subject with the approval of a Radioactive Drug Research Committee to 1258/999 MBq (34/27 mCi) in the adult male/female. Quantitative measurement of monoamine oxidase A activity in the brain and elsewhere may aid in understanding the pathophysiology of several disease processes including neuroendocrine neoplasms and depression.
Murthy
Rajan
R
Department of Neuroscience, Division of Brain Imaging, New York State Psychiatric Institute, New York 10032, USA. rm907@columbia.edu
Erlandsson
Kjell
K
Kumar
Dileep
D
Van Heertum
Ronald
R
Mann
John
J
Parsey
Ramin
R
D000818:Animals; D002250:Carbon Radioisotopes / Q000737:chemistry*; D005123:Eye / Q000473:pathology; D006247:Harmine / Q000737:chemistry*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008168:Lung / Q000473:pathology; D015233:Models, Statistical; D010215:Papio; D049268:Positron-Emission Tomography / Q000379:methods*; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods*; D013997:Time Factors; D014018:Tissue Distribution
D002250:Carbon Radioisotopes; D006247:Harmine