Quantitative Comparison of the Bolus and Steady-State Methods for Measurement of Cerebral Perfusion and Oxygen Metabolism: Positron Emission Tomography Study Using ¹⁵O-Gas and Water

Abstract

To evaluate a new simplified bolus method for measurement of cerebral perfusion and metabolism, the parametric images with that method were compared with those obtained from the conventional steady-state method with 15O-gas. The new method also provided images of arterial blood volume (V0), which is a different parameter from cerebral blood volume (CBV) obtained using a C15O technique. Seven healthy volunteers and 10 patients with occlusive cerebrovascular diseases underwent positron emission tomography (PET) scans with both methods. Three-weighted integration was applied to calculate regional cerebral blood flow (rCBF) and regional cerebral metabolic rate of oxygen (rCMRO2) in the bolus method. Global and regional CBF and CMRO2 in volunteers were compared between the two methods and used as control data. Regional values in patients also were evaluated to observe differences between the bilateral hemispheres. Both rCBF and rCMRO2 were linearly well correlated between the two methods, although global difference in CMRO2 was significant. The difference in each parametric image except for V0 was significant between the bilateral hemispheres in patients. The bolus method can simplify oxygen metabolism studies and yield parametric images comparable with those with the steady-state method, and can allow for evaluation of V0 simultaneously. Increase in CBV without a change in V0 suggested the increase might mainly be caused by venous dilatation in the ischemic regions.

Shorter Examination Method for the Diagnosis of Misery Perfusion with Count-Based Oxygen Extraction Fraction Elevation in 15O-Gas PET

“…Next, bolus H 2 15 O scans were obtained with a 3-min acquisition starting at the time of bolus injection of the tracer at 740 MBq. Arterial blood was sampled, and radioactivity in the blood samples was immediately measured with a scintillation counter to determine arterial blood activity (13,14). Reconstructions of PET data were performed by use of filtered backprojection with a Hanning filter at a cutoff of 6.0 mm full width at half maximum in the transaxial direction.…”

“…Parametric images of cerebral blood flow, CBV, OEF, and cerebral metabolic rate for oxygen were calculated from PET images and arterial blood data (5,7,14 (Table 2).…”

“…All scans were acquired in the 2-dimensional mode with a whole-body tomography scanner (Advance; GE Healthcare), which permits the simultaneous acquisition of 35 image slices with an interslice spacing of 4.25 mm (14). Performance tests showed the intrinsic resolutions of the scanner to be 4.6-5.7 mm in the transaxial direction and 4.0-5.3 mm in the axial direction.…”

“…15 O-Gas was administered from the tube, and radioactive gas in the expired air was vacuumed from the mask. Subjects inhaled C 15 O 2 as a single dose of 1,000 MBq for CBV measurements (14). PET was started at least 30 s after the tracer count had peaked in the brain and was continued for 3 min.…”

“…Arterial blood was sampled, and radioactivity in the blood samples was immediately measured with a scintillation counter to determine arterial blood activity (13,14). Reconstructions of PET data were performed by use of filtered backprojection with a Hanning filter at a cutoff of 6.0 mm full width at half maximum in the transaxial direction.Parametric images of cerebral blood flow, CBV, OEF, and cerebral metabolic rate for oxygen were calculated from PET images and arterial blood data (5,7,14 (Table 2). …”