CT scan

What is a CT scanner?

The CT scanner itself is a large machine that looks like a giant doughnut. Your child will lie still on a table that slides into and out of the opening while the machine takes pictures of the part of her body that is being investigated. Even though the machine is large and makes humming noises, it will not touch her during the scan.

How does a CT scanner work?

An x-ray tube on a rotating gantry within the "doughnut" emits controlled, narrow beams of X-ray radiation, which pass through the body and get picked up by an array of electronic detectors on the frame's opposite side. This produces many pictures in thin two-dimensional "slices" of the area under study. The slices are then assembled by a dedicated computer, which can if necessary compile them into detailed 3-dimensional images that can be studied from all angles.

Why might a CT scan be needed?

In children, CT is often used to investigate head injuries or acute neurological symptoms, evaluate chronic sinus symptoms or hearing loss, diagnose appendicitis, evaluate masses, detect fractures or help determine why a child has trouble breathing. Because it provides detailed views of many types of tissues, it's an excellent way to rule out disease and facilitate treatment.

Your child's doctor may have requested a CT scan to obtain specific diagnostic information that is not provided by or is complementary to other imaging technologies such as conventional x-rays, ultrasound, nuclear medicine or magnetic resonance imaging (MRI).

In emergencies, a CT scan can quickly reveal internal injuries and bleeding, providing important information to the medical team that may prove life-saving.

How should I prepare my child for the CT scan?

The most important thing is to tell your child in simple terms why the test is necessary. You can explain that the CT won't hurt her and that the machine does not touch her body. If an IV is needed for the injection of contrast (the "dye" used to provide additional detail for some scans), or to provide sedation, your child may well feel discomfort from the needle. The staff will give specific instructions when your exam is scheduled, but here are some general guidelines for CT scans without sedation:

• Notify the CT staff of any illness your child has, such as cold, cough, fever, diarrhea, or vomiting; we may need to reschedule the test.
• Tell us about all allergies or any previous drug reaction that may keep your child from receiving the contrast safely.
• If you have severe kidney disease or are on kidney dialysis, there is a risk of a condition called "nephrogenic systemic fibrosis" from the dye. You should discuss this risk with your child’s clinician prior to the test.
• Dress your child in comfortable clothing with no metal snaps, belt buckles or zippers. In the case of CT scans of the head, metal hair clips and jewelry must be removed.
• If your child will need an intravenous or oral contrast agent, there are no specific dietary restrictions for most patients.
• If your child is having sedation or anesthesia, please see CT scan with sedation/anesthesia.

What if my child can't lie still for the scan?

Because CT scans are generally quick — often less than 10 seconds — many children can hold still for the procedure. But depending on which part of the body is being scanned, the exam can take longer. Some types of scans are more forgiving of slight movements, while others require your child to be entirely motionless for a greater length of time. Depending on your child's age and other factors, sedation may be necessary.

What should I expect when I bring my child to the hospital?

The day of your child's exam, come to the Radiology suite on the second floor of the main hospital or on the first floor at our Waltham facility and check in at the front desk.

• If your child is having an abdominal scan, you'll need to arrive two hours before the exam because your child will probably have to drink a contrastsolution that will enhance thedetail of the CT images. She may also need an IV-administered contrast, which is given by a technologist just before the exam.
• After you have checked in, a technologist will greet you and explain the test in detail, answering any questions you or your child might have.
• Sometimes, emergencies or urgent cases require us to rearrange our schedule and this causes delays for outpatients. If this happens, the technologist will keep you informed and you are welcome to check with the front desk staff for updates.

What happens during the procedure?

The technologist positions and secures your child on the movable bed that slidesinto and out of the CT scanner. At this point, the technologist may use a smallneedle to place an intravenous line into your child's hand or foot. There will likelybe some brief discomfort when this is done.

The technologist then performs the exam according to the imaging protocol specified by the radiologist. is in direct contact with the radiologist at all times.

Can I stay in the room with my child?

Having a parent in the room during the exam can help reduce any anxiety your child might have. However, you cannot be in the room if you are pregnant. In this situation, please bring the other parent or a trusted caregiver.

How will I learn the results of my child's CT scan?

After the pediatric radiologist or pediatric neuroradiologist interprets the images, he will provide a written report to your child's doctor, who can then tell you the results. Results are typically reported within 24 hours; in urgent cases, our radiologists communicate immediately with the referring physician.

What are the risks of CT scans?

CT scans involve ionizing radiation as is used in conventional x-rays. In certain clinical situations, the benefits of an accurate diagnosis outweigh the risk of exposure to radiation during the exam. We calibrate our x-ray-based equipment and adapt protocols to deliver doses appropriate to children. The narrow beams of radiation used in CT, as well as protective shielding that prevents unnecessary radiation to sensitive tissues, also help limit radiation dose.

Sometimes, it is possible to reach a diagnosis by using imaging technologies that do not involve radiation: ultrasound or magnetic resonance imaging (MRI), for example. When appropriate, our radiologists will advise referring physicians that this is the safest course of action.