Optimal scan time of oxygen-15-labeled gas inhalation autoradiographic method for measurement of cerebral oxygen extraction fraction and cerebral oxygen metabolic rate

• Published in: Annals of nuclear medicine Vol. 22; no. 8; pp. 667 - 675
• Main Authors: Shidahara, Miho, Watabe, Hiroshi, Kim, Kyeong Min, Kudomi, Nobuyuki, Ito, Hiroshi, Iida, Hidehiro
• Format: Journal Article
• Language: English
• Published: Japan Springer Japan 01.10.2008; Springer Nature B.V
• Subjects: Administration, Inhalation; Autoradiographic method; Autoradiography - methods; Brain - diagnostic imaging; Brain - metabolism; Computer Simulation; Humans; Image Enhancement - methods; Imaging; Medicine; Medicine & Public Health; Metabolic Clearance Rate; Models, Neurological; Nuclear Medicine; O-15 oxygen gas; Original Article; Oxygen - metabolism; Oxygen Consumption - physiology; Oxygen Radioisotopes - administration & dosage; Oxygen Radioisotopes - pharmacokinetics; Positron emission tomography; Radiology; Radionuclide Imaging; Radiopharmaceuticals - administration & dosage; Radiopharmaceuticals - pharmacokinetics; Reproducibility of Results; Sensitivity and Specificity; Time Factors; O-15 oxygen gas; Autoradiographic method; Positron emission tomography
• ISSN: 0914-7187; 1864-6433
• DOI: 10.1007/s12149-008-0157-9

Objective Regional cerebral blood flow (CBF), cerebral blood volume, oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO 2 ) can be estimated from C 15 O, H 2 15 O, and 15 O 2 tracers and positron emission tomography (PET) using an autoradiographic (ARG) method. Our objective in this study was to optimize the scan time for 15 O 2 gas study for accurate estimation of OEF and CMRO 2 . Methods We evaluated statistical noise in OEF by varying the scan time and error caused by the tissue heterogeneity in estimated OEF and CMRO 2 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 CMRO 2 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 (CBF g and CBF w ) was 80 and 20, OEF in gray and white matter ( E g and E w ) was 0.4 and 0.3, (ii) CBF g and CBF w decreased by 50%, and E g and E w increased by 50% when compared with conditions (i) and (iii). CBF g and CBF w decreased by 80%, and E g and E w increased by 50% when compared with condition (i). Results 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 CMRO 2 , 3 min of scan time was desirable. Conclusions The optimal scan time of 15 O 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 CMRO 2 .