There are several non-invasive ways to look inside an premature baby’s body in an effort to determine what may be wrong. Most people are familiar with X-rays and magnetic resonance imaging (MRI) tests. By taking two- or three-dimensional pictures of the inside of the body, these techniques can be used to diagnose problems associated with the heart, lungs, digestive system, and other organs.
Many of these tests require that the premature baby remain still for a period of time. Since this can be difficult for a baby, she may be sedated or gently secured in position for the procedure. The following types of imaging tests are detailed below.
A chest X-ray , also called chest radiography, is a picture of the heart, lungs, and bones of the chest. An X-ray is a type of radiation that passes through the body. The amount of radiation received during the test is small and not harmful. It gives the doctor information on the size, shape, and location of the heart, in order to help diagnose a condition. X-rays can also confirm the proper placement of important tubes, such as the breathing and feeding tubes, catheters or lines for intravenous fluids, and, less commonly, drainage tubes.
How is the X-ray done?
Usually chest X-rays are taken with the body in an elongated position. Generally, a premature baby will be placed on a table and gently held, arms up, by the nurse. The X-ray machine is turned on for a fraction of a second. Beams of X-rays pass through the chest to make a picture on the film. Usually an X-ray is taken from the front and then the side. The procedure is painless and the photographic results should be ready within minutes.
Although chest X-rays are probably the most common type of X-rays for premature babies, the technology can be used on other parts of the body. For example, a baby with a suspected case of necrotizing enterocolitis, which is a problem with the intestines, may have an X-ray of the abdomen.
Additionally, X-rays of the bones in general can detect a condition known as osteopenia of prematurity, historically known as rickets of prematurity. Osteopenia, or weakened bones, is sometimes seen in low birth weight babies with chronic lung disease. Bone X-rays can also identify congenital bone abnormalities and fractures.
Ultrasound machines transmit high frequency sound pulses into the body using a probe. The sound waves travel into the body and bounce back to a detector. On a screen, the waves that are bounced back are assembled, giving a picture of how far away and how dense something is within the body.
Ultrasound has many uses; most parents are familiar with fetal ultrasound. Most commonly for premature babies, a head ultrasound is used to detect possible problems within the brain and an abdominal ultrasound detects problems of the organs in the abdomen such as the kidney, liver, and intestines.
MRI, or magnetic resonance imaging, is a way of taking cross-sectional pictures of the head and body without the use of X-rays. A magnet, radio signals, and a computer are used to create the pictures. An MRI scan is fairly noisy but does not hurt. Ear plugs or some other form of ear protection is standard, even for babies. A number of short scans make up a complete MRI study. Each scan takes from one to 10 minutes. The total time for a complete MRI study is about one to two hours.
Who will do the MRI study?
A team of three or four people will do the MRI study. A medical radiation technologist trained in MRI will do the MRI scans. A nurse will prepare your baby for the scans. She will give your baby the sedation or help the anaesthetist. The anaesthetist is the doctor who gives the general anesthetic. A radiologist will check and interpret each scan to make sure that the study is complete. A radiologist is a doctor who specializes in diagnostic images.
Some MRI scans give the doctor more information when they are done with a special liquid called a contrast medium. This clear, colourless fluid is put into a vein in the hand or arm with a small needle. The liquid is designed to reveal details that would not otherwise be seen and is quite safe. If the radiologist feels that the scan would be better with this liquid, it will be given part of the way through the exam.
As a parent, before you enter the room, you will be questioned or you may have to fill out a screening form. Staff need to make sure that it is safe for you to be near the strong magnet in the MRI scanner. You will have to empty your pockets completely of everything, including coins, keys, pens, wallets, and bank cards. You will also have to take off your watch. Depending on the hospital, you may or may not be allowed in the room during the procedure.
Computerized tomography (CT)
A computerized tomography (CT) scan uses an X-ray and a computer to take cross-sectional pictures of your premature baby. These pictures allow doctors to see the structures inside the body at different levels. A CT scan can be done on any body part.
The length of time for your baby’s CT scan depends on many things. A routine scan may take anywhere from five to 30 minutes, depending on the part of the body being scanned and how still the baby can remain during the scan.
Is there any preparation for a CT scan?
Movement during the scan creates blurry pictures that cannot give the information needed. For this reason, most premature babies need mild sedation to help them sleep so they can lie still for the scan. If needed, the sedation will be given by mouth, or by needle into a vein. The type given depends on the age and size of your baby as well as the kind of CT scan being done.
Who will do the CT scan?
The CT scan will be done by a team of three people. A medical radiation technologist will take the pictures and assist the nurse. The nurse will give your baby sedation if needed. A radiologist, a doctor who specializes in diagnostic images, will check the scan before your baby leaves to make sure it is complete.
Will my premature baby be given any needles for the CT scan?
Some CT scans give the doctor more information when they are done with a special liquid called an X-ray contrast fluid. This is a clear, colourless fluid that is injected into a vein. This fluid makes the blood vessels inside the body show up better on the pictures. The liquid is quite safe. The nurse will look for your baby’s best vein and use a small butterfly needle to put in the contrast liquid. The needle may sting a little when it goes in, but it will be taken out once all the contrast medium has been given.
A premature baby who is having an abdominal CT scan may be given contrast fluid through a feeding tube. This helps make the stomach and intestines easier to see on the pictures.
The technologist will make sure that your baby is lying on the table in the correct position for the CT scan. Either the head or the feet will be closer to the camera, depending on which body part is being scanned. The table will then move up and into the chamber, where the pictures are taken.
After some pictures have been taken, the radiologist may ask for X-ray contrast fluid to be given to your baby.
After the camera has stopped scanning, the radiologist will check the pictures, ask for a few more to be taken, or decide that the CT scan is finished.
In addition to abdominal X-rays and ultrasound, tests called contrast gastrointestinal (GI) studies may be useful in detecting anomalies and diagnosing blockages in the intestines. A contrast fluid is put in the premature baby’s digestive system either through a feeding tube or as an enema through the anus depending on which part of the GI tract is to be examined. A device called a fluoroscope is used to track the contrast fluid through the GI tract.
Upper GI imaging is also used for swallowing studies whereby the swallowing action is monitored, making sure that a premature baby is not inhaling liquid. GI imaging may also be called for to examine gastroesophageal reflux and other feeding problems including those related to a problem with the intestines called necrotizing enterocolitis.