Changes in Cerebral Blood Flow Caused by Thermo-Stimulation as Visualized by MRA

Abstract

This study was undertaken to observe changes in cerebral vessel thicknesses and cerebral blood flow caused by thermo-stimulation using magnetic resonance angiography (MRA). Ten healthy males had thermo-pad wrapped around their necks and underwent cerebral blood flow imaging [3D time of flight (TOF), 3D phase contrast (PC)] for 10 min using the MRA imaging technique without thermo-stimulation. Immediately after imaging, subjects were given thermo-stimulation and then re-imaged at 30 min after initiating the thermo-stimulation. The three-dimensional data obtained were processed using the maximum intensity projection technique and compared. Mean left internal carotid artery signal intensities determined by TOF were 175.8 and 172.78 before and during thermo-stimulation, respectively, indicating a -1.7 % change, and mean right internal carotid artery signal intensities were 170.1 and 166.3, indicating a -2.2 % change. Mean basilar artery (BA) intensity changed from 184.5 to 180.8 (-2.0 %), whereas mean Lt. superficial temporal artery (STA) intensity changed from 114.0 to 127.2 (+11.6 %) and mean Rt. STA intensity changed from 113.5 to 126.1 (+11.1 %). Changes in blood vessel thicknesses were not significant for ICAs, MCAs, or BAs, but nevertheless showed decreasing tendencies. On the other hand, mean STA blood vessel thickness increased by 28 % and changes were obvious by visual inspection. Blood flow velocities calculated using PC data showed more than a 45 % increase in occipital arteries and STAs of ECAs. This study provides objective data which demonstrate that thermo-stimulation directly influences cerebral vessel dimensions and cerebral blood flow.