Computed tomography Computed Tomography (CT) In computed tomography (CT), which used to be called computed axial tomography (CAT), an x-ray source and x-ray detector rotate around a person. In modern scanners, the x-ray detector usually... read more (CT), with or without a radiopaque contrast agent Radiopaque Contrast Agents During imaging tests, contrast agents may be used to distinguish one tissue or structure from its surroundings or to provide greater detail. Contrast agents include Radiopaque contrast agents... read more (which can be seen on x-rays)

To identify structural abnormalities (such as abscesses Diagnosis A brain abscess is a pocket of pus in the brain. An abscess may form in the brain when bacteria from an infection elsewhere in the head or in the bloodstream or from a wound enter the brain... read more , tumors Diagnosis A brain tumor can be a noncancerous (benign) or cancerous (malignant) growth in the brain. It may originate in the brain or have spread (metastasized) to the brain from another part of the body... read more , and hydrocephalus Normal–Pressure Hydrocephalus Normal-pressure hydrocephalus consists of difficulty walking, urinary incontinence, and dementia due to an increase in the fluid that normally surrounds the brain. Usually, the main symptoms... read more ) in the brain

To identify bleeding or evidence of strokes Diagnosis A stroke occurs when an artery to the brain becomes blocked or ruptures, resulting in death of an area of brain tissue due to loss of its blood supply (cerebral infarction) and symptoms that... read more in the brain

To identify ruptured or herniated disks in the spine Herniated Disk A herniated disk occurs when the tough covering of a disk in the spine tears or ruptures. The soft, jelly-like interior of the disk may then bulge out (herniate) through the covering. Aging... read more

To identify spinal fractures Compression Fractures of the Spine In a compression fracture of the spine, the drum-shaped part (body) of one or more back bones (vertebrae) collapses into itself and becomes squashed (compressed) into a wedge shape. Most compression... read more

To monitor the effects of radiation therapy on brain cancer or of antibiotics on a brain abscess

Doppler ultrasonography Doppler ultrasonography Ultrasonography uses high-frequency sound (ultrasound) waves to produce images of internal organs and other tissues. A device called a transducer converts electrical current into sound waves... read more of the carotid arteries and the arteries at the base of the brain (transcranial)

To identify and evaluate narrowing or blockage of arteries in the neck and head and thus assess the risk of stroke

Most often done to evaluate people who have had a transient ischemic attack Transient Ischemic Attacks (TIAs) A transient ischemic attack (TIA) is a disturbance in brain function that typically lasts less than 1 hour and results from a temporary blockage of the brain’s blood supply. The cause and symptoms... read more after the attack and over time

Magnetic resonance angiography Magnetic resonance angiography (MRA) In magnetic resonance imaging (MRI), a strong magnetic field and very high frequency radio waves are used to produce highly detailed images. MRI does not use x-rays and is usually very safe... read more (MRA) with or without a radiopaque contrast agent

To evaluate arteries in people who have had a stroke or a transient ischemic attack or in people who may have an aneurysm or arteriovenous malformation (an abnormal connection between arteries and veins)

Functional magnetic resonance imaging Functional MRI In magnetic resonance imaging (MRI), a strong magnetic field and very high frequency radio waves are used to produce highly detailed images. MRI does not use x-rays and is usually very safe... read more (fMRI)

To identify which areas of the brain are active when a task (such as reading, writing, remembering, calculating, or moving a limb) is done

Diffusion-weighted imaging Diffusion-weighted MRI In magnetic resonance imaging (MRI), a strong magnetic field and very high frequency radio waves are used to produce highly detailed images. MRI does not use x-rays and is usually very safe... read more (DWI) MRI

To identify very early stroke and to help diagnose Creutzfeld-Jacob disease Diagnosis Creutzfeldt-Jakob disease is a prion disease characterized by progressive deterioration of mental function, leading to dementia, involuntary jerking of muscles (myoclonus), and staggering when... read more

Positron emission tomography Positron Emission Tomography (PET) Positron emission tomography (PET) is a type of radionuclide scanning. A radionuclide is a radioactive form of an element, which means it is an unstable atom that becomes more stable by releasing... read more (PET)

To evaluate blood flow and metabolic activity in the brain

To provide information about seizure disorders Diagnosis In seizure disorders, the brain's electrical activity is periodically disturbed, resulting in some degree of temporary brain dysfunction. Many people have unusual sensations just before a seizure... read more

To help identify Alzheimer disease Diagnosis Alzheimer disease is a progressive loss of mental function, characterized by degeneration of brain tissue, including loss of nerve cells, the accumulation of an abnormal protein called beta-amyloid... read more , Parkinson disease Diagnosis Parkinson disease is a slowly progressive degenerative disorder of specific areas of the brain. It is characterized by tremor when muscles are at rest (resting tremor), increased muscle tone... read more , transient ischemic attacks, and strokes

Most often done in research studies