Document Detail

Validation of a less-invasive method for measurement of serotonin synthesis rate with alpha-[11C]methyl-tryptophan.
MedLine Citation:
PMID:  9778189     Owner:  NLM     Status:  MEDLINE    
We tested in normal human subjects a less invasive method to obtain plasma input function required in the calculation of the brain serotonin synthesis rate measured with positron emission tomography (PET) and alpha-[11C]methyl-tryptophan (alpha-MTrp). The synthesis rates derived with the arterial input function were compared to those derived from venous plasma and venous sinus time-radioactivity curves obtained from dynamic PET images. Dynamic PET images were obtained for the lengths up to 90 minutes after an injection of alpha-MTrp (400 to 800 MBq). Input functions were generated from both artery and vein in three subjects, and from artery only in two subjects. Net unidirectional uptake constants of alpha-MTrp (K*; mL/g/min) were calculated in several brain regions graphically using data between 20 and 60 minutes after injection with different input functions. In the five subjects with arterial sampling, we tested two methods for correcting the input functions from the venous samples: (1) normalization to the mean exposure time at 20 minutes from arterial curve; and (2) the use of the venous sinus curve for the first 20 minutes. Venous curves coincided with the arterial ones after about 20 minutes. When the venous curves were used, there was an underestimation of the area under the curves up to 20 minutes, resulting in a 5% to 30% overestimation of K* values. Combined use of the sinus curve up to 20 minutes and venous curve from 20 to 60 minutes as an input function resulted in the K* (mL/g/min) values larger by 7.1 +/- 3.8% than the K* values estimated with the arterial input function. Normalization of the venous curve to the exposure time at 20 minutes obtained from the arterial plasma curve resulted in a bias in the K* of about -0.34 +/- 3.32%. The bias from the K* values was propagated to the serotonin synthesis rates. The use of a combination of the venous blood samples and venous sinus as the input function resulted in an acceptable bias in the serotonin synthesis rates from the tissue time-radioactivity curves generated by PET.
S Nishizawa; M Leyton; H Okazawa; C Benkelfat; S Mzengeza; M Diksic
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism     Volume:  18     ISSN:  0271-678X     ISO Abbreviation:  J. Cereb. Blood Flow Metab.     Publication Date:  1998 Oct 
Date Detail:
Created Date:  1998-11-09     Completed Date:  1998-11-09     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  8112566     Medline TA:  J Cereb Blood Flow Metab     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1121-9     Citation Subset:  IM    
Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Quebec, Canada.
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MeSH Terms
Brain / metabolism*,  radionuclide imaging*
Carbon Radioisotopes / diagnostic use
Evaluation Studies as Topic
Serotonin / biosynthesis*,  blood
Tomography, Emission-Computed / methods*
Tryptophan / analogs & derivatives*,  diagnostic use
Grant Support
Reg. No./Substance:
0/Carbon Radioisotopes; 13510-08-2/alpha-methyltryptophan; 50-67-9/Serotonin; 73-22-3/Tryptophan

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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