Simulation Study of Noise Property of CMRO₂ Quantitation Methods with Inhalation of ¹⁵O₂

Measurements of the oxygen consumption in brain have been studied by PET. Autoradiographic method (ARG) was suggested (Mintum et al.) to yield CMRO ₂. This method required separately obtained information about CBF, CBV, thus time of 30-60 min. is required for three separate scans. To decrease the scan time, a new protocol was suggested as a rapid dual table method (ARG-D), in which [¹⁵O]water injection scan and [ ¹⁵O]O₂ inhalation scan are continuously carried out. Another method of weighted integration(WI) method with single 3 min. ¹⁵O₂ inhalation scan was suggested (Ohta et al.). We modified this method by taking into account the water re-circulation(WI-WR). In this study, the statistical noise properties and effects of error propagated from dispersion, delay, and volume of distribution on CMRO₂ image, derived by these methods were evaluated. Tissue time activity curves was generated from typical blood time activity curves. A 80 % of noise at a peak in [¹⁵O] water tissue time acticity curve was added to study the noise propagation and accuracy in CMRO₂ image. Also dispersion, delay, and volume of distribution was varied and evaluated the error propagation. Methods of ARG, WI-WR and ARG-D, reproduce the given CMRO₂ within 2% accuracy, while method WI gives CMRO₂ 5-15 The effect of noise in unit of %SD was 12 % for ARG, 25 % for WI and WI-WR, and 17 % for ARG-D method. On the basis of simulation study suggests that the ARG-D method developed could be used to estimate the CMRO₂ values in clinic.