Stroke is a sudden diminution or loss of consciousness, sensation, and voluntary motion due to interrupted blood supply to the brain. Blood supply may be interrupted due to formation of clot in the blood vessel or rupture of these vessels. According to the World Health Organization, 15 million people suffer stroke worldwide each year. Of these, 5 million die and another 5 million are permanently disabled. Technologies used for diagnosis of stroke include CT angiography, transeophageal echocardiography, carotid artery imaging and diffusion-weighted MRI imaging.
Angiography is an important noninvasive diagnostic test for stroke. It utilizes x-rays with catheters computed tomography (CT), magnetic resonance imaging (MRI) and a contrast material to produce pictures of major blood vessels throughout the body.
Special x-ray equipment produces multiple images and a computer aids in providing multidimensional views. CT angiography (CTA) produces detailed images of both blood vessels and tissues.
In transesophageal echocardiography (TEE), a small probe guided into the esophagus is used to closely evaluate the heart and blood vessels within the chest. Studies indicate that many strokes may be caused by a blood clot originating in the heart, so examining the heart may assist in determining the cause and preventing future strokes. In TEE ultrasonic waves produced by transducer (similar to a microphone) are used to assess the structure and function of heart. Transducer is placed on the chest, the ultrasonic sound waves move to the heart tissues and the waves are reflected off from the heart. The reflected waves are picked up by the transducer and are fed into the computer. The computer converts these sound waves into an image of the heart walls and valves.
Types of TEE Echocardiography
· M-mode echocardiography: M-mode echo is useful for measuring heart structures
· Doppler echocardiography: The Doppler technique is used to measure and assess the flow of blood through the heart.
· Color Doppler: Different colors are used to designate the direction of blood flow. This simplifies the interpretation of the Doppler technique.
Ultrasound waves are used to produce pictures of the different organs of the body. Carotid artery imaging is noninvasive diagnostic test in which ultrasound of the body’s two carotid arteries, (that is located on each side of the neck and carries blood from the heart to the brain) provides detailed pictures of these blood vessels and information about the blood flowing through them. Doppler ultrasound is used to evaluate blood velocity as it flows through a blood vessel.
DWI is a widespread and evolving non-invasive diagnostic technique used to evaluate tissue structure and cerebral connectivity. The changes in the sensitivity of signals on diffusion weighted images provide information on the alterations in the tissue structure. The cerebral connectivity is assessed using software approaches designed to interpret the fiber tract orientation information that DWI provides. It is an important tool for understanding the brain pathology and abnormality in patients with stroke.