Omission of [15O]CO scan for PET CMRO2 examination using 15O-labelled compounds

Objective

CBF, OEF and CMRO₂ provide us important clinical indices and are used for assessing ischemic degree in cerebrovascular disorders. These quantitative images can be measured by PET using ¹⁵O-labelled tracers such as C¹⁵O, C¹⁵O₂ and ¹⁵O₂. To reduce the time of scan, one possibility is to omit the use of CBV data. The present study investigated the influence of fixing the CBV to OEF and CMRO₂ values on subjects with and without cerebrovascular disorders.

Methods

The study consisted of three groups, namely, GROUP-0 (n = 10), GROUP-1 (n = 9), and GROUP-2 (n = 10), corresponding to—without significant disorder, with elevated CBV, and with reduced CBF and elevated OEF, respectively. All subjects received PET examination and using the PET data OEF and CMRO₂ images were computed by fixing CBV and with CBV data. The computed OEF and CMRO₂ values were compared between the methods.

Results

The OEF and CMRO₂ values obtained by fixing the CBV were around 10% underestimation against that with CBV data. The regression analysis showed that these values were comparable (r = 0.93–0.98, P < 0.001). The simulation showed that fixing of the CBV would not derive significant error in either OEF or CMRO₂ values, when changed from 0 to 0.08 ml/g.

Conclusion

This study shows the feasibility of fixing the CBV value for computing OEF and CMRO₂ values in the PET examination, suggesting the CO scan could be eliminated.