Cranial Ultrasound: Types, Purpose, Procedure, Safety

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Ultrasound (USG) of the head or cranial ultrasound uses sound waves to create images of the brain. The ultrasound machine sends sound waves to the head and the images are recorded on a computer. This black and white image shows the internal structures of the brain, including the ventricles (fluid-filled cavities in the brain) and blood vessels.

Cranial ultrasound is usually done on babies whose skull bones have not fully grown (they still have a soft spot on the crown). The crown provides an opening for sound waves to pass through and reach the brain.

1. Type

There are two types of cranial ultrasound, namely cranial ultrasound and transcranial Doppler.

An ultrasound examination of the head produces images of the brain and cerebrospinal fluid flowing and contained within its ventricles, fluid-filled cavities located inside the brain.

Because ultrasound waves do not pass easily through bone, this examination is most often performed on infants, whose skulls are not yet fully formed. The gaps between the skull bones provide a “window,” which allows ultrasound rays to freely enter and return from the brain. An ultrasound probe and some gel are placed on the outside of the head in one of the boneless areas, as described on the Radiological Society of North America website .

On transcranial Doppler ultrasound, the patient is positioned supine on the examination table or sitting upright in the examination chair. A clear water-based gel is applied to the back of the neck, above and next to the cheekbones, in front of the ears or above the eyelids, as this is where the blood vessels supply the brain. The transducer is gently pressed over one of these areas to measure the direction and speed of blood flowing.

The patient must remain still during the examination, which may take up to 35 minutes. If the patient needs to adjust his position on the examination table, it is usually okay to pause. If an examination is being performed on an infant, a nurse or radiologist can help keep the baby still to ensure the best quality of imaging.

2. Purpose

If the baby is born more than three weeks before the time of birth, the doctor will perform an ultrasound of the head. The test aims to check for brain problems that can occur in premature babies, such as:

Bleeding in the brain, called intraventricular hemorrhage or intraventricular hemorrhage (IVH).

This test can also help doctors diagnose other brain problems, such as:

Infection.
Tumor, cyst, or other mass.

The doctor may also order a head ultrasound for babies with these conditions:

The baby’s head is larger than normal.
A bulge at the weak spot of the head or the crown.
Any symptom of a brain or nerve problem.

Cranial ultrasound can be done in adults to help locate brain masses. Because the test cannot be performed after the skull bones are fused, it is only performed after the skull has been opened during brain surgery.

3. Procedure

Reported by HealthLink BC , there is no special preparation for a cranial ultrasound. If this test is done on an older baby, it may be helpful if the baby is a little hungry. You can feed the baby during the procedure. This can help calm the baby so he or she will remain calm during the test.

This test is performed by a doctor who is an expert in imaging tests (radiologists). It can also be done by an ultrasound technologist (sonographer) in collaboration with a radiologist. For infants, the test may be performed at the infant’s bedside in the neonatal intensive care unit (NICU).

The baby will lie on his back. The transducer is moved across the crown. You may be asked to hold the baby during the procedure. Images of the brain and the deep fluid spaces (ventricles) can be viewed on a video screen.

If adults get an ultrasound of the head during brain surgery, the surgeon will remove part of the skull and use a probe to help find tumors or masses in the brain.

The Doppler procedure also uses an ultrasound wand and machine, but the process is different. The gel is applied to the neck and up to the cheeks to check for blood flow from that angle. This can take up to 35 minutes. The doctor may also place headgear on the patient for continuous monitoring for 30 minutes to look for high-intensity signals.

4. Advantages and disadvantages

Like all ultrasound studies, head ultrasound is highly operator dependent. This is not a true disadvantage, but does require that the radiographer performing the examination is well trained in acquisition techniques, knows how to make use of available ultrasound machines, and has knowledge of intracranial anatomy and pathology so as not to miss any significant findings.

In addition, ultrasound examination is very sensitive to movement, and an active or crying child will slow down the examination process.

Larger patients are more difficult to image with ultrasound because the larger amount of tissue attenuates sound waves as they pass deeper into the body.

Examination results may change due to recent open wounds or surgical incisions near the imaged area, as well as changes in blood flow patterns due to heart disease or irregular heart rhythms.

5. Considerations
Ultrasound cannot penetrate bone, so cranial ultrasound can only be performed on babies whose skull bones (cranial) have not grown together. However, Doppler ultrasound may be done to check blood flow in the brain in both children and adults.