Feasibility of reducing X-ray dose in 64-slice CT brain perfusion by increasing interval between scans with an axial scan mode

Objective: To investigate the feasibility of reducing X-ray dose in 64-slice CT brain perfusion by relaxing the temporal resolution with an axial scan mode. Methods: Forty patients who underwent CT perfusion scans for suspicion of stroke but turned out to have normal brain perfusion were selected for the study. Among these patients, 20 were scanned with cine scan mode, which meant continuous scanning for 50 s with scan time of 1 s. And other 20 patients were scanned with axial mode, which was consisted of l s scan time and 2 s interval between scans. The axial coverage was 40 mm for all patients. The regional cerebral blood flow (CBF), regional cerebral blood volume (CBV) and mean transit time (MTT) were analyzed by t-test for three anatomic features: the cortical gray matter (GM), the normal white matter (WU) and the lentiform nucleus (LN). The radiation dose between the two groups was compared. Results: The CBF of GM,WU, LN measured with cine scan mode were (48.8±16.0), (28.3±12.0), (55.4±11.2) ml·100 g-1·min-1. The CBV were (2.2±0.7), (1.5±0.5), (2.3±0.8) mL/100g. The MTT were (3.9±0.8), (5.3±0.9), (2.8±0.4) s. The CBF of GM, WU, LN measured with axial mode were (47.6±9.6), (23.9±6.9), (53.1±5.1) ml·100 g-1·min-1. The CBV were (2.2±0.6), (1.5± 0.4), (2.2±0.7) ml/100 g. The MTF were (6.0±1.7), (6.0±1.7), (3.0±0.3)s. There were no statistically significant differences between the corresponding parameters for the two groups (t=0.244, 1.533,0.832,0.166,0.411,0.537,1.688,1.471,1.638, P>0.05). The radiation dose with the axial mode was 803.04 mGy·cm, which was 66% lower than that with cine scan mode (2361.92 mGy·cm). Conclusion: The use of relaxed temporal resolution with 1 s scan time and 2 s interval in CT brain perfusion can provide accurate perfusion parameters while reducing radiation by 66%. (authors)