The Circle of Willis encircles the stalk of the pituitary gland and provides important communications between the blood supply of the forebrain and hindbrain and connects two arterial sources together to form the arterial circle, which is responsible for supplying the brain with blood. These can be seen with the help of CT scan which are special X-ray Test that produce cross-sectional images of the body using X-rays and a computer. The higher resolution has assist the doctor in making a diagnosis.