FIG 5. CBF maps derived from a rabbit with brain tumor. The CBF values, ranging from low-to-high flow are color-coded from black (0 mL/min/100 g) to blue and green (100 mL/min/100 g) to yellow and red (200 mL/min/100 g). For both PaCO₂ levels, the tumor is clearly delineated by the red and yellow colors.

A, Plain (precontrast) CT Image. The following X-ray CT parameters were used to acquire the image: 80 kVp, 80 mA, 10-cm field of view, and 3-mm slice thickness. Hyperdense areas corresponding to the tumor were observed in the right parietal and temporal regions.

B, Normocapnia CBF map. CBF in the tumor ranged from 66 to 208 mL/min/100 g, whereas CBF in the contralateral normal hemisphere ranged from 14 to 75 mL/min/100 g.

C, Hypocapnia CBF map. The maximum and minimum CBF values in tumor were 56 and 170 mL/min/100 g, whereas the contralateral normal hemisphere showed CBF values ranging from 3 to 43 mL/min/100 g.

D, Subtraction of the hypocapnia CBF map from the normocapnia map. The mean global CBF difference was 18.7 mL/min/100 g. Reduction in CBF upon hyperventilation is shown in both tumor and normal tissues. The green circular areas in the center of the brain are cerebral arteries.