The three-dimensional time-of-flight magnetic resonance angiography (3D-TOF-MRA) method has enabled
in vivo investigation of the human cranial arteries with a relatively high spatial resolution. The 3D-TOF-MRA method is simple to use and requires no intravenous contrast to visualize the arteries[
1]. Thus, it is possible to detect changes of the luminal size of larger and smaller arteries relatively precise. This method has been employed in several headache and migraine studies to measure arterial changes before and after infusion of different vasoactive drugs and during versus outside attacks of migraine headache[
2‐
8]. Most recently, using this method we compared the arterial circumferences on the headache side with the non-headache side and a migraine attack day with a non-headache day in patients with migraine. Surprisingly, we found intracranial but
not extracranial arterial dilatation on the headache-side relative to the non-headache-side[
6]. In a previous MRA study of drug-induced migraine attacks the middle cerebral artery (intracranial) and middle meningeal artery (extracranial) were both dilated on the pain-side versus the non-pain side[
4], while another MRA study of drug-induced migraine attacks reported no side-to-side changes at all[
2]. Although, the differences were ascribed different drug effects, it raised the question about the biological variations in day-to-day and side-to-side arterial circumference in migraine patients. In addition, these variations may also be affected by the observer related variability. Automated analysis of the acquired MRA images may reduce observer related variability and may also ensure better repeatability across different studies. The LKEB-MRA vessel wall analysis software[
9], which has been used in several headache and migraine studies[
2‐
8], provides an automated method to detect the vessel lumen contour accurately. The required user interaction is limited to placing only a proximal and a distal point in the vessel of interest[
9]. In the present study, we therefore initially investigated the intra- and inter-observer variations and then the day-to-day, and side-to-side variations of the MMA and MCA using LKEB-MRA vessel wall analysis software[
9]. We hypothesized that the observer related variability would be less than 5% using automated analysis software and the biological variations, including observer variation, would be less than 10%.