Medical Health Encyclopedia

Computed Tomography. Computed tomography (CT) uses a sophisticated x-ray machine and a computer to create a detailed picture of the body's tissues and structures. It is not as accurate as an MRI and does not detect about half of low-grade gliomas. It is useful in certain situations, however. Often, doctors will inject the patient with an iodine dye, called contrast material, to make it easier to see abnormal tissues. A CT scan helps locate the tumor and can sometimes help determine its type. It can also help detect swelling, bleeding, and associated conditions. In addition, computed tomography is used to check the effectiveness of treatments and watch for tumor recurrence.

Click the icon to see an image of a CT scan of the brain.

Positron Emission Tomography. Positron emission tomography (PET) provides a picture of the brain’s activity rather than its structure by tracking substances that have been labeled with a radioactive tracer. As with magnetic resonance spectroscopy (MRS), it is also able to distinguish between recurrent tumor cells from dead cells or scar tissue, although MRS is more widely available. PET is not routinely used for diagnosis, but it may supplement MRIs to help determine tumor grade after a diagnosis. Data from PET may also help improve the accuracy of newer radiosurgery techniques.

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Other Imaging Techniques. A number of other advanced imaging techniques may be used for specific purposes, if available or under investigation.

• Single photon emission tomography (SPECT) is similar to PET but is not as effective in distinguishing tumor cells from destroyed tissue after treatments.
• Magnetoencephalography (MEG) scans measure the magnetic fields created by nerve cells as they produce electrical currents.
• Cerebral angiography involves x-rays of blood vessels in the brain. A long, thin tube (catheter) is threaded through blood vessels from a distant site to the brain, and a radiopaque substance (a substance that is impenetrable to x-rays) is injected through it. The role of angiography in glioma is usually limited to planning surgical removal of a tumor suspected of having a large blood supply.
• Radionuclide brain scintigraphy uses a radioactive substance that is administered and absorbed by capillaries in the tumor, which are then viewed using imaging techniques.
• Digital holography, a new technique that provides full three-dimensional mapping, is under investigation.

Lumbar Puncture (Spinal Tap)