A1 Refereed original research article in a scientific journal
Optimal scan time of oxygen-15-labeled gas inhalation autoradiographic method for measurement of cerebral oxygen extraction fraction and cerebral oxygen metabolic rate
Authors: Shidahara M, Watabe H, Kim KM, Kudomi N, Ito H, Iida H
Publisher: SPRINGER
Publication year: 2008
Journal: Annals of Nuclear Medicine
Journal name in source: ANNALS OF NUCLEAR MEDICINE
Journal acronym: ANN NUCL MED
Volume: 22
Issue: 8
First page : 667
Last page: 675
Number of pages: 9
ISSN: 0914-7187
DOI: https://doi.org/10.1007/s12149-008-0157-9
Abstract
Regional cerebral blood flow (CBF), cerebral blood volume, oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO2) can be estimated from C15O, H-2 15O, and 15O(2) tracers and positron emission tomography (PET) using an autoradiographic (ARG) method. Our objective in this study was to optimize the scan time for 15O(2) gas study for accurate estimation of OEF and CMRO2.We evaluated statistical noise in OEF by varying the scan time and error caused by the tissue heterogeneity in estimated OEF and CMRO2 using computer simulations. The characteristics of statistical noise were investigated by signal-to-noise (S/N) ratio from repeated tissue time activity curves with noise, which were generated using measured averaged arterial input function and assuming CBF = 20, 50, and 80 (ml/100 g per minute). Error caused by tissue heterogeneity was also investigated by estimated OEF and CMRO2 from tissue time activity curve with mixture of gray and white matter varying fraction of mixture. In the simulations, three conditions were assumed (i) CBF in gray and white matter (CBFg and CBFw) was 80 and 20, OEF in gray and white matter (E g and E w) was 0.4 and 0.3, (ii) CBFg and CBFw decreased by 50%, and E g and E w increased by 50% when compared with conditions (i) and (iii). CBFg and CBFw decreased by 80%, and E g and E w increased by 50% when compared with condition (i).The longer scan time produced the better S/N ratio of estimated OEF value from three CBF values (20, 50, and 80). Errors of estimated OEF for three conditions owing to tissue heterogeneity decreased, as scan time took longer. Meanwhile in the case of CMRO2, 3 min of scan time was desirable.The optimal scan time of 15O(2) inhalation study with the ARG method was concluded to be 3 min from taking into account for maintaining the S/N ratio and the quantification of accurate OEF and CMRO2.
Regional cerebral blood flow (CBF), cerebral blood volume, oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO2) can be estimated from C15O, H-2 15O, and 15O(2) tracers and positron emission tomography (PET) using an autoradiographic (ARG) method. Our objective in this study was to optimize the scan time for 15O(2) gas study for accurate estimation of OEF and CMRO2.We evaluated statistical noise in OEF by varying the scan time and error caused by the tissue heterogeneity in estimated OEF and CMRO2 using computer simulations. The characteristics of statistical noise were investigated by signal-to-noise (S/N) ratio from repeated tissue time activity curves with noise, which were generated using measured averaged arterial input function and assuming CBF = 20, 50, and 80 (ml/100 g per minute). Error caused by tissue heterogeneity was also investigated by estimated OEF and CMRO2 from tissue time activity curve with mixture of gray and white matter varying fraction of mixture. In the simulations, three conditions were assumed (i) CBF in gray and white matter (CBFg and CBFw) was 80 and 20, OEF in gray and white matter (E g and E w) was 0.4 and 0.3, (ii) CBFg and CBFw decreased by 50%, and E g and E w increased by 50% when compared with conditions (i) and (iii). CBFg and CBFw decreased by 80%, and E g and E w increased by 50% when compared with condition (i).The longer scan time produced the better S/N ratio of estimated OEF value from three CBF values (20, 50, and 80). Errors of estimated OEF for three conditions owing to tissue heterogeneity decreased, as scan time took longer. Meanwhile in the case of CMRO2, 3 min of scan time was desirable.The optimal scan time of 15O(2) inhalation study with the ARG method was concluded to be 3 min from taking into account for maintaining the S/N ratio and the quantification of accurate OEF and CMRO2.
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