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CURRENT ISSUETHE QUARTERLY JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING

A Journal on Nuclear Medicine and Molecular Imaging


A Journal on Nuclear Medicine and Molecular Imaging
Affiliated to the Society of Radiopharmaceutical Sciences and to the International Research Group of Immunoscintigraphy
Indexed/Abstracted in: Current Contents/Clinical Medicine, EMBASE, PubMed/MEDLINE, Science Citation Index (SciSearch), Scopus
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The Quarterly Journal of Nuclear Medicine 2002 March;46(1):70-85

TECHNOLOGIES AND METHODS IN NUCLEAR MEDICINE
Guest Editors: Todd-Pokropek A., Gilardi M. C. 

Kinetic modeling in positron emission tomography

Schmidt K. C., Turkheimer F. E. *

From the Laboratory of Cere­bral Metabolism National Institute of Mental Health Bethesda, Maryland, USA
* Imaging Research Solutions Limited Hammersmith Hospital London, UK

Most PET kinet­ic mod­el­ing approach­es ­have at ­their ­basis a com­part­men­tal mod­el ­that has ­first-­order, con­stant coef­fi­cients. The ­present arti­cle out­lines the one-, two-, and ­three-com­part­ment mod­els ­used to meas­ure cere­bral ­blood ­flow, cere­bral glu­cose metab­olism, and recep­tor bind­ing, respec­tive­ly. The num­ber of com­part­ments of ­each mod­el is ­based on spe­cif­ic knowl­edge of the phys­io­log­i­cal and/or bio­chem­i­cal com­part­ments ­into ­which the trac­er dis­trib­utes. Additional phys­i­cal and bio­chem­i­cal prop­er­ties of the trac­er dis­tri­bu­tion are con­sid­ered in spec­i­fy­ing the use of ­first-­order ­rate con­stants. For exam­ple, in cere­bral ­blood ­flow and recep­tor bind­ing stud­ies trans­port ­across the ­blood-­brain bar­ri­er by dif­fu­sion can be mod­eled as a ­first-­order pro­cess. A sat­ur­able car­ri­er-medi­at­ed pro­cess or sat­ur­able enyz­me cat­a­lyzed reac­tion, ­when trac­er dos­es of the ­labeled sub­strate are ­used and the nat­u­ral sub­strate is in ­steady-­state, ­also ­results in ­first-­order ­rate con­stants, as in glu­cose metab­olism stud­ies. The ­rate of ­ligand bind­ing, on the oth­er ­hand, ­depends on the con­cen­tra­tions of ­both sub­strate and avail­able recep­tors. In ­order to appro­pri­ate­ly mod­el the reac­tion as pseu­do ­first-­order dur­ing a spec­i­fied experi­men­tal inter­val, pro­to­cols are care­ful­ly ­designed to ­assure ­that the num­ber of avail­able bind­ing ­sites ­remains approx­i­mate­ly con­stant through­out the giv­en inter­val. A ­broad ­array of scan­ning pro­to­cols is ­employed for kinet­ic anal­y­ses. These ­include sin­gle-­scan approach­es, ­which func­tion ­like ­their auto­ra­dio­graph­ic coun­ter­parts in ani­mal stud­ies and are ­often ­called “auto­ra­dio­graph­ic” meth­ods, ­which ­allow esti­ma­tion of a sin­gle param­e­ter. Dynamic scan­ning to ­obtain the ­time ­course of tis­sue activ­ity ­allows simul­ta­ne­ous esti­ma­tion of mul­ti­ple param­e­ters. Scanning may be con­duct­ed dur­ing a peri­od of trac­er ­uptake or ­after attain­ment of ­steady-­state con­di­tions. All quan­ti­ta­tive mod­el­ing approach­es ­share the com­mon require­ment ­that an arte­ri­al ­input func­tion be meas­ured or an appro­pri­ate sur­ro­gate be ­found. A ­vast ­array of meth­ods is avail­able for esti­ma­tion of mod­el param­e­ters, ­both ­micro and mac­ro. In the ­final anal­y­sis, it is the inter­ac­tion ­among all ele­ments of the PET ­study, includ­ing care­ful trac­er selec­tion, mod­el spec­ifi­ca­tion, experi­men­tal pro­to­col ­design, and ­sound param­e­ter esti­ma­tion meth­ods, ­that deter­mines the quan­ti­ta­tive accu­ra­cy of the esti­mates of the phys­io­log­i­cal or bio­chem­i­cal pro­cess ­under ­study.

language: English


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