Definition - What does Phased Array Technology mean? Ultrasound beams are used in phased array (PA) ultrasonic equipment, which is considered an advanced method of ultrasonic testing. This technology finds applications in medical science and non-destructive testing. This method is more accurate at finding flaws in manufactured materials such as welds.
A migraine is a medical condition which usually causes a pounding, throbbing headache on one side of the head. The pain may be very bad and hurt so much that a person may have a hard time doing anything. While most people who have migraines get a headache, not everyone does.
Chronic migraine is a distinct and relatively recently defined sub-type of Chronic Daily Headache. The International Headache Society defines chronic migraine as more than fifteen headache days per month over a three month period of which more than eight are migrainous, in the absence of medication over use. Episodic migraine is the other migraine sub-type, which is defined as less than 15 headache days per month.1.