Validation of an integrated, ultra-rapid ¹⁵O-PET system for quantitative assessment of CMRO₂, CBF and OEF

Objectives Use of ¹⁵O₂ and PET can provide essential information to characterize pathophysiological status in patients withCVD, but has limited applicability, due to complexed logistics. A novel system has been developed for ultra-rapid assessment of CMRO₂, CBF and OEF, involving ¹⁵O-dedicated cyclotron, fully-automated radio-synthesis , and a dedicated workstation connected to peripheral devices, allowing easier operation under “on-demand” needs. We intended to evaluate feasibility of this system.

Methods Subjects consisted of 11 healthy volunteers (23.1±1.2 yo, all male) and 20 patients with steno/occlusive ICA, and 8 with Moyamoya diseases. A single dynamic PET scan was initiated over 9 min usingCTPET with continuous monitoring of arterial input function, while sequential inhalation of (¹⁵O₂ and C¹⁵O₂. Functional images of CMRO₂, CBF, OEF, and CBV-equivalent V0’s for oxygen and water were calculated by the recently validated DBFM method (JCBFM, 2013). All subjects were scanned also with C¹⁵O to determine CBV. Results from DBFM were compared with those by DARG (JCBFM, 2005) with a standard CBV compasation. In normal, the short dynamic scan was repeated twice to evaluate reproducibility.

Results CBF, CMRO₂ and OEF values from normal were 39±4.3 mL/min/100g, 3.4±0.30 mL/min/100g and 0.45±0.045, with reproducibility of +5.3±10, -10±9, -16±13% (mean±SD), respectively. Agreement of DBFM involving intrinsic CBV correction with DARG requiring additional CBV was 5.2±4.6, -4.9±6.5, and 0.1±5.7% in normal, corresponding to CBF, CMRO₂ and OEF, respectively, and all <10%. Agreement was worse in patient populations, and was -6.5±8.1, 8.8±12.0, and -1.6±7.7%, respectively. Six cases in Moyamoya and 2 cases with steno-occlusive patients showed disagreement >10%.

Conclusions Results suggest validity of the present ultra-rapid, automated systemwith much improved logistics.

Research Support Grant from the Ministry of Health, Labour and Welfare, Japan (H22NIG002).