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Imaging Tests


Neuroradiological tests can help doctors visualize damage to the brain. While an abnormal result certainly means that a patient has a moderate to severe TBI, many patients with moderate to severe TBI may have normal results on imaging tests. These imaging tests can include:

CT Scan: The most common imaging test is computerized axial tomography, called a CT or CAT scan. This scan produces a series of images that show cross-sections of the brain. CT scans can detect physical changes in the brain such as hematomas and swelling, which may require immediate treatment.

MRI: Another useful diagnostic test is magnetic resonance imaging, or MRI, which uses a large magnet and radio waves to generate computerized images of the brain without exposing the patient to x-ray radiation. MRIs produce high-resolution images of brain structures and are painless.

X-rays, MRIs, and CT scans can detect fractures, hemorrhages, swelling, and certain kinds of tissue damage, but they do not always detect traumatic brain injury. This is because TBI, especially in its milder forms, often involves subtle trauma to the brain that causes chemical and physical changes to brain tissues rather than structural damage. These changes often cannot be found with standard imaging procedures.

More sophisticated imaging techniques that measure brain cell metabolism, such as single-photon emission computed tomography, called SPECT; positron emission tomography, called PET; or diffusion tensor imaging, called DTI, can help visualize subtle injuries, but rarely change the treatment plan. In other words, these tests can help providers to better understand the location and extent of the injury, but are not likely to change the surgical or non-surgical approach to treatment.

SPECT Scan: Single-photon emission computed tomography, or SPECT, involves the injection of a small amount of short-lived radioactive particles into the blood. A special camera capable of detecting these particles then rotates around the patient and takes pictures from many angles. A computer then uses these pictures to form a cross-sectional image. A SPECT scan is particularly useful in detecting blood flow.

PET Scan: Positron emission tomography, or PET, is a specialized imaging technique that uses short-lived radioactive substances to produce three-dimensional colored images. PET scanning provides information about the body's chemistry not available through other procedures. Unlike other imaging techniques that look at anatomy or body structure, PET studies metabolic activity or body function of substances functioning within the body.

DTI Scan: Diffusion tensor imaging, or DTI, is a specialized type of MRI that measures the movement of water in the brain, detecting areas where the normal flow of water is disrupted. This test is particularly useful to image the white matter fiber tracts, or neurons, of the brain.

Depending on individual circumstances, a variety of other medical diagnostic tools and techniques may be used. These include the following:

Angiogram: An angiogram is a test used to examine blood vessels. When diagnosing a brain injury, the test involves injecting dye into an artery that supplies blood to the brain, usually through a catheter inserted in the groin. The dye highlights the blood vessels on x-ray, and can show any leakage from those vessels.

ICP Monitor: An ICP monitor is a device used to measure intracranial pressure, or pressure within the skull. One of the reasons this pressure can increase is when an injury to the brain causes swelling. The ICP monitor consists of a small tube, placed into or on top of the brain through a small hole in the skull. This tube is connected to a transducer that registers the pressure, which is displayed on a monitor.

EEG: An EEG, or electroencephalogram, is a test to measure brain activity. During an EEG, numerous electrodes in the form of patches are applied to the head. These electrodes detect the electrical activity in the brain, and a graph of that activity is generated.