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Treatment of radioactive decay in pharmacokinetic modeling: Influence on parameter estimation in cardiac 13 N ‐ PET
Author(s) -
Glatting G.,
Reske S. N.
Publication year - 1999
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.598561
Subject(s) - dosimetry , nuclear medicine , cardiac pet , positron emission tomography , medical physics , radiochemistry , medicine , chemistry
Radioactive decay during measurement can be accounted for by either a d _ ecay correction of the measured data b _ eforem _ odeling (DbM) or by direct implementation of d _ ecayi _ nto the pharmacokinetic m _ odel (DiM). The purpose of this study was to quantify the influence of the type of decay correction on the calculated parameters for the example of a three‐compartment model used for the calculation of myocardial perfusion with13 N ammonia and positron emission tomography (PET). For a given input function [ C a ( t ) ∝ t exp ( − kt ) ,k = 1.72 / min ] the tissue uptake for two parameter sets of K 1 ,k 2 ,k 3 , TBV were calculated for 20 frames ( 12 × 10 s ,4 × 30 s ,3 × 120 s ,1 × 300 s ) . These values were mathematically deteriorated by various noise levels according to Poisson statistics and fitted by a Levenberg–Marquardt algorithm. Estimated parameter means and coefficients of variation of the fitted parameters were calculated for the DbM and DiM case. The estimated parameter means for both decay correction methods were of comparable quality. The important measure for a single fit is the relative variability of the fitted parameters. This value is up to a factor 1.15 smaller for K 1obtained with DiM and a reasonable noise level of 10%. Therefore, decay correction should be taken into account during modeling to reduce the variability in the fitted parameters.