Evaluation of a commercial PET tomograph-based system for the quantitative assessment of rCBF, rOEF and rCMRO2 by using sequential administration of 15O-labeled compounds

Abstract

The purpose of this study was to develop a reliable and practical strategy that generates quantitative CBF and OEF maps accurately from PET data sets obtained with 15O-tracers. Sequential sinogram data sets were acquired after the administration of 15O-tracers, and combined single-frame images were obtained. The delay time between sampled input function and the brain was estimated from the H2(15)O study with the whole brain and the arterial time-activity curves (TACs). The whole-brain TACs were obtained from the reconstructed images (image-base method) and the sinogram data (sinogram-base method). Six methods were also evaluated for the dead-time and decay correction procedures in the process of generating a single-frame image from the dynamic sinogram. The estimated delay values were similar with both the sinogram-based and image-based methods. A lumped correction factor to a previously added single-frame sinogram caused an underestimation of CBF, OEF and CMRO2 by 16% at maximum, as compared with the correction procedure for a short sinogram. This suggested the need for a dynamic acquisition of a sinogram with a short interval. The proposed strategy provided an accurate quantification of CBF and OEF by PET with 15O-tracers.

Rapid Quantitative Measurement of CMRO2 and CBF by Dual Administration of 15O-Labeled Oxygen and Water During a Single PET Scan—a Validation Study and Error Analysis in Anesthetized Monkeys

“…For example, when the error in the measured delay was 2 secs, errors in DARG were at most 5%, 3%, and 3% in CBF, OEF, and CMRO 2 , respectively. Considering that the error estimation of delay would be up to 2 secs in the present procedure (Kanno et al, 1987;Shidahara et al, 2002), these results indicate that the error sensitivity to delay associated with DARG did not greatly exceed that from three-step ARG.…”

“…The delay was estimated based on a method previously described (Iida et al, 1988). Briefly, three parameters, K 1 , k 2 , and delay (Dt), were determined using whole brain and blood TACs around the period of H 2 15 O injection with an NLF procedure (Iida et al, 1988;Shidahara et al, 2002). The dispersion time constant was fixed at 3 secs .…”

“…It is known that the measured arterial TAC is delayed and more dispersed relative to the true input TAC in the brain because of the time it takes for blood to traverse the peripheral artery and catheter tube before reaching the detector (Iida et al, 1986(Iida et al, , 1988(Iida et al, , 1989(Iida et al, , 2000Lammertsma et al, 1990). Calculation of CBF using ARG PET always uses a fixed partition coefficient throughout the whole brain (ranging 0.8 to 0.9 mL/g) and does not evaluate it regionally (Herscovitch and Raichle, 1985;Iida et al, 1989Iida et al, , 1991Shidahara et al, 2002). An error in CBV measured by the PET scan may also introduce errors in calculating the cerebral oxygen consumption (Mintun et al, 1984;Lammertsma et al, 1987).…”

“…An alternative autoradiographic method (ARG) using only short administration times for each of the three tracers (three-step ARG) has been developed (Mintun et al, 1984) and subsequently simplified and optimized (Iida et al, 1993;Sadato et al, 1993;Hatazawa et al, 1995;Shidahara et al, 2002;Hattori et al, 2004). Cerebral blood flow images can be obtained by an H 2 15 O autoradiographic method, using a PET counts-versus-CBF nomogram, which follows a simple look-up table procedure Herscovitch et al, 1983;Kanno et al, 1987); the quantitative accuracy of these images is improved when input delay and dispersion are corrected (Iida et al, 1986(Iida et al, , 1988.…”

Estimation of Oxygen Metabolism in a Rat Model of Permanent Ischemia Using Positron Emission Tomography with Injectable 15O-O2

“…Then, the OEF value was calculated using the same equation (Eq. 2) as that applied to the bolus inhalation of 15 O-O 2 gas method (Mintun et al, 1984;Shidahara et al, 2002), which could be used with this pharmaceutical as shown previously (Magata et al, 2003) RðtÞ…”