Using 80 kVp versus 120 kVp in perfusion CT measurement of regional cerebral blood flow

Perfusion CT studies of regional cerebral blood flow (rCBF), involving sequ ential acquisition of cerebral CT sections during IV contrast material admi nistration, have classically been reported to be achieved at 120 kVp. We hy pothesized that using 80 kVp should result in the same image quality while significantly lowering the patient's radiation dose, and we evaluated this assumption. In five patients undergoing cerebral CT survey, one section level was image d at 120 kVp and 80 kVp, before and after IV administration of iodinated co ntrast material. These four cerebral CT sections obtained in each patient w ere analyzed with special interest to contrast, noise, and radiation dose. Contrast enhancement at 80 kVp is significantly increased (P < .002), as we ll as contrast between gray matter and white matter after contrast enhancem ent (P < .001). Mean noise at 80 kVp is not statistically different (P = .0 42). Finally, performance of perfusion CT studies at 80 kVp, keeping mAs co nstant, lowers the radiation dose by a factor of 2.8. We, thus, conclude that 80 kVp acquisition of perfusion CT studies of rCBF will result in increased contrast enhancement and should improve rCBF analy sis, with a reduced patient's irradiation.