Effect of contrast medium injection rate on cerebral hemodynamics study by using multislice CT perfusion imaging

Objection: To explore a practical injection rate at which the assumption of maximal slope model can be guaranteed and at which quantitative assessment of regional cerebral blood flow (rCBF) is accurate. Methods: Twenty-four healthy adult volunteers matched with sexes and years were averagely divided into three groups. All volunteer's received intravenous administration of 50 ml contrast medium at different injection rates (4.5, 6.0 ml/s and 7.5 ml/s). Dynamic scans were made at the level of the basal ganglia slice and its adjacent slices and started 4 s after the administration of contrast medium, then repeated every 1.0 s for 4 images, and performed for 50 s. These 200-slice dynamic images were processed with the dedicated perfusion software. Firstly, time-concentration curves (TDCs) were constructed from every volunteer's perfusion CT series in pixels of the anterior cerebral artery, in pixels of the sagittal venous sinus, respectively. Secondly, the rCBFs of the gray matter and the white matter(rCBF1, rCBF2)were acquired with a maximal-slope-model-based algorithm. Comparisons of parameters of cerebral hemodynamics [the difference between the point of the venous starting enhancement and the point of arterial peak enhancement (tVO-tAP), rCBF1, rCBF2] were determined between the different groups and then statistically analyzed. Results: The tAP arrived before the tv0 only for 7.5 ml/s. (tVO-tAP) was -3.5 s, -l.5 s, 0.2 s, respectively for 4.5 ml/s, 6.0 ml/s and 7.5 ml/s. The difference of (tVO-tAP) among the three groups was significant (F=18.25, P<0.01). The rCBF1 and rCBF2 had significant differences between 4.5 ml/s, 6.0 ml/s and 7.5 ml/s; they were (52.8±3.1) ml·min-1·100 g-1, (21.9±2.4)ml·min-1· 100 g-1, respectively for 7.5 ml/s. Conclusion: The injection rate of 7.5 ml/s, at which the assumption of maximal slope model can be guaranteed and at which CT-rCBF values are considerably close to those obtained by SPECT, is a practical and promising one. (authors)