Optimization of three-dimensional time-of-flight magnetic resonance angiography of the intracranial arteries.

The signal-to-noise ratio obtained from arteries in three-dimensional (3D) time-of-flight (TOF) magnetic resonance (MR) angiography is often too low to allow clinical diagnosis because the radiofrequency pulse decreases the magnetization of protons in the blood and suppresses the in-flow effect in the slab. The present study adjusted the position of the head coil to boost arterial signal intensity. Ten healthy volunteers, eight men and two women aged 24-78 years, underwent 3D TOF MR angiography of the intracranial arteries with the same standard GE transmit-receive birdcage head coil using both normal and half position (lower edge of the coil level with the mouth) methods. Our subjects were divided into Group 1 consisted of five relatively young volunteers aged 24-42 years (mean 31.2 years), and Group 2 consisted of five older volunteers aged 70-78 years (mean 73 years). The following four arteries were chosen for analysis: the internal carotid artery (ICA), the proximal middle cerebral artery segment (M1), and the two distal middle cerebral artery segments (M2, M31). The half position method increased the signal-to-noise ratio in the ICA, M1, M2, and M3 by 15%, 25%, 36%, and 44%, respectively. In general, this method resulted in the generation of stronger signals in the M2 and M3 in younger subjects and in all arteries examined in older subjects. The half position method can provide better MR angiograms in certain brain regions of younger people, and in all brain regions in older patients.