What is an Ultrasound, CT, and MRI?


Ultrasound is a test that uses sound waves to look at internal organs and produce images of the human body. The human ear cannot hear the sound waves used in an ultrasound. Ultrasound is: Noninvasive, which means it does not penetrate the skin or body openings. The technical term for ultrasound imaging is sonography. Ultrasound technology was originally developed as sonar to track submarines during World War I. It was first used medically in the 1950s and is considered very safe.

Ultrasound has many uses in neurosurgery. In infants it can be used to look at the brain through the anterior fontanelle or soft spot or sometimes at the spine. It is good for looking for abnormalities that are large or involve the fluid spaces of the brain. In the spine it can unfortunately be inaccurate and miss more subtle problems. We do use ultrasound in surgery frequently to allow us to observe changes in the brain and spine as surgery proceeds. This can be very helpful in preventing complications and avoiding problems.

The advantages  of ultrasound are that it is usually quick, does not require anesthesia, does not involve any radiation or x-ray, and is painless.

The disadvantages are that is can miss more subtle problems and does not show the detail that is often needed for the brain and spine

Common uses: hydrocephalus, shunts, large heads, cysts


CT or Computed Tomography or Computed Axial Tomography (CAT) is a more detailed imaging technique using x-ray images. Multiple images are taken during the CT using a very fast technology and then a computer compiles them into complete images of the body tissues. The CT can show parts of the body that can not be seen on x-ray as well as detail that is not able to be seen on x-ray. CT is very useful in looking at the bones in particular including the skull and bones of the spine. CT scanning technology has improved significantly over the years and is now very fast with limited exposure to x-rays and is generally considered safe

Contrast is a substance that is given through an iv like a “dye” to help highlight abnormal tissues or vessels within the brain or spine. There is a small risk of allergic reaction to the contrast but in general the advantages of the contrast outweigh the risks of side effects. Patients with allergy to seafood or shellfish have a higher risk of reaction and should notify us if they have any concerns.

See more information about the CT scanner at RMHC

The advantages of CT are that it is usually quick, does not require anesthesia, and is painless.

The disadvantages are that it is not as detailed as MRI for soft tissue like brain and it does involve x-ray.

Common uses: Craniosynostosis, trauma, bone lesions, skull bumps or lumps, spinal deformity, and follow up for shunts


Magnetic Resonance Imaging (MRI) uses a magnetic field and pulse of radio wave energy to create images of the body structures and organs. This does not involve any x-ray of radiation. At the time of the MRI the patient is placed in a tube which contains a strong magnet. Patients with metal implants that may be affected by a strong magnet can not have an MRI. The patient must lay still during the test which can be any where from an hour to four hours. Young children or claustrophobic patients may need sedation or anesthesia to complete the scans.

The MRI images are significantly more detailed than any other techniques and good at looking at detailed brain and spinal cord anatomy. Sometimes contrast is used as well called Gadolinium or Gad to help highlight abnormal areas or problems. The risk of allergic reaction is lower than the contrast used for CT and fairly rare.

The advantages of MRI is the detailed pictures that can be obtained making it the preferred imaging in neurosurgery and there is no radiation exposure.

The disadvantages are that it often requires anesthesia and it is not good at looking for bone issues.

Common uses: Tethered cord and spinal cord problems, Brain lesions and tumors, congenital brain malformations or hydrocephalus.