Quantification of Cerebral Blood Flow and Oxygen Metabolism with 3-Dimensional PET and 15O: Validation by Comparison with 2-Dimensional PET

(3-step method). The inhaled (or injected) dose for 3D PET was approximately one fourth of that for 2D PET. Results: In the 2D PET study, average gray matter values (mean 6 SD) of CBF, CBV, CMRO2, and OEF were 53 6 12 (mL/100 mL/min), 3.6 6 0.3 (mL/100 mL), 3.5 6 0.5 (mL/100 mL/min), and 0.35 6 0.06, respectively. In the 3D PET study, scatter correction strongly affected the results. Without scatter correction, average values were 44 6 6 (mL/100 mL/min), 5.2 6 0.6 (mL/100 mL), 3.3 6 0.4 (mL/100 mL/min), and 0.39 6 0.05, respectively. With the exception of OEF, values differed between 2D PET and 3D PET. However, average gray matter values of scatter-corrected 3D PET were comparable to those of 2D PET: 55 6 11 (mL/100 mL/min), 3.7 6 0.5 (mL/100 mL), 3.8 6 0.7 (mL/100 mL/min), and 0.36 6 0.06, respectively. Even though the 2 PET scanners with different crystal materials, data acquisition systems, spatial resolution, and attenuation-correction methods were used, the agreement of the results between 2D PET and scatter-corrected 3D PET was excellent. Conclusion: Scatter coincidence is a problem in 3D PET for quantitative 15 O study. The combination of both the present PET/CT device and the HDE scatter correction permits quantitative 3D PET with the same degree of accuracy as 2D PET and with a lower radiation dose. The present scanner is also applicable to conventional steady-state 15 O gas