The benefits and risks of medical imaging: What families should know

A boy and his Dad get ready for a CT scan by watching fish swim across the wall. Part of our care at OHSU Doernbecher is to distract children from their circumstances, limiting the need for sedation.

When caring for children, doctors work with the patient and parents to decide upon a course for medical treatment. In making treatment recommendations it is common for the doctor to outline the benefits and risks of medical therapy, and sometimes the risks of NOT receiving that medical therapy.

Just like many other decisions in everyday life, medical decisions are made based on an analysis of the risks and benefits.

In this post, I will provide some perspective about how your child’s doctor, the pediatric radiologist, and you as parent and/or patient can think about the risks and benefits associated with medical imaging.

A short list of questions are provided at the end of this blog post to assist you in conversations with your child’s doctor and decisions about medical imaging.

Talk to the pediatric radiologist
When I became a radiologist my mother-in-law asked if I was really a doctor. She had never actually seen a radiologist and I did not see patients in an office or do surgery, so I did not fit her concept of who a doctor is or what a doctor does.

However, I and other pediatric radiologists at OHSU Doernbecher Children’s Hospital enjoy meeting our patients and their families. We have knowledge of medical physics and image interpretation in children that can help you understand the risks and benefits of an imaging study.

At Doernbecher we are supporters of the Image Gently campaign, a group devoted to responsible use of medical radiation dose in children.


Benefits of medical imaging
There can be enormous benefits to having an imaging study performed. Diagnostic medical imaging provides vital information about your child’s health to their pediatrician, neurologist, emergency room doctor and other physicians.

A pediatric radiologist is another doctor that ‘sees’ children, though often not in person, but by analyzing their radiographic images. By reading medical images of the body, a radiologist can help diagnose illnesses such as appendicitis, pneumonia, the effects of trauma, or if your child might have cancer.

Potential benefits of imaging studies include:

  • Diagnosis of illness, and the severity or benign nature of that process, is made quickly and accurately.
  • Invasive diagnostic procedures such as exploratory surgery or angiography or cardiac catheterization may not be necessary.
  • When a child has a chronic disease or a form of cancer, medical imaging is essential not only at initial diagnosis, but for monitoring how the disease is responding to treatment or if the disease is progressing, and when a treatment plan might be stopped or adjusted.

Risks of medical imaging
Complications associated with medical imaging are rare, but can be serious, potentially leading to injury or causing a secondary illness.

























Restraint and sedation for imaging procedures
During most imaging procedures the patient must remain motionless while pictures are being taken. For an X-ray or ultrasound procedure, a child only needs to remain still for a few seconds at a time, so often we can get away without sedating or restraining an older child for X-rays. However, younger children and those who are scared by being in a strange environment might need to have help lying still, most often by a parent.

There really are not risks of restraining a child for imaging procedures; it is usually more traumatic for the parent than for the patient.

CT and MRI are imaging procedures that require the patient to lie still for a longer period of time, often 10 to15 minutes for CT and up to an hour or more for an MRI. Most children ages 4 to 5 can reliably perform well during CT, but only by about age 9 can a child undergo MRI without sedation.

An MRI is more secluded for the patient because they lie in a long tube (magnet) during the exam. Since an MR exam also takes a longer time and the patient is more isolated, most children younger than 9 require sedation to tolerate the exam

Sedation for imaging, surgery or any other procedure carries risks of aspiration, prolonged drowsiness and inability to sleep the night after the procedure. There have been studies that have shown sedation and general anesthesia are possibly harmful for brain development in children younger than 1.

Let your child’s physician and the pediatric radiologist guide you in making decisions about when sedation is needed.

Ionizing radiation – from X-rays and CT scans
Over the past decade or so, newspaper articles, television reports and medical journal publications alike have reported on the potential harmful effects of medical radiation. Topics highlight how many exams are performed and how often the potential harmful effects of radiation, what we do and do not know about radiation dose, and how lower radiation dose is best, especially in children.

But remember, we are all exposed to ionizing radiation just by virtue of living on planet earth. Sunlight, radon, other natural elements, and even flying in an airplane are sources of radiation in our everyday lives.

Much of the interest and research in limiting medical radiation has been on the part of pediatric radiologists and medical physicists – all over the world – including at OHSU Doernbecher.

Pediatric radiologists strive to use radiation dose in the most responsible manner, adhering to the goal of a dose ‘as low as reasonably achievable’ (ALARA). Prescribing radiation dose for pediatric CT scans at OHSU Doernbecher as low as possible requires noting patient size, age and the reason the exam is being performed. Dose is balanced with the quality of the images. If the radiation dose is reduced by too much the image quality suffers and hinders diagnosis.

Risks of not performing medical imaging
If the diagnosis of disease is delayed because imaging could not be done, the patient might become sicker, or if an injury could not be seen because imaging was not performed the injury could become worse or lead to disability.

The benefit of medical imaging, therefore, is that it allows us to diagnose disease or injury and is also important in monitoring chronic disease processes.

How important is that radiation dose?
Even when medical imaging requires the patient receive a small radiation dose, it can be a good thing … after all, imaging helps to make a diagnosis more quickly and with greater accuracy.

Ionizing radiation, like that used for X-rays, CT and angiography/catheterization, is the kind of radiation that has the ability to knock an electron out of its orbit, which can lead to damage in DNA, and has been linked to cancer induction. Other types of injury that also rarely may occur due to ionizing radiation include reddening of the skin (burns) and even hair loss. [NEJM. Nov 2007; 357:2277-2284.]

In order to better understand the most important of these risks, cancer induction, let me outline a few points:

  • Most of what we know about the effects of ionizing radiation is from studying large populations of people who were exposed to radiation such as atomic bomb survivors, nuclear radiation workers and people who have survived radiation exposure accidents such as at Chernobyl and more recently there may be lessons to be learned from the people of Fukushima.
  • These long-term, low-dose or short-term, large-dose exposures to ionizing radiation do not model the dose or type of exposure given during X-rays or CT. During X-rays and CT exams a patient is exposed to a relatively small dose of ionizing radiation for a very short period of time.

Put radiation dose risk into perspective

Most importantly just how risky is the radiation dose from medical imaging exams?
The dose from CT scans has been studied most often and most thoroughly. In a study performed to evaluate the risk of causing a fatal cancer or death from exposure to radiation from a CT scan, it was estimated that between one in 2,000 and one in 20,000 CT scans will result in development of a fatal malignancy.

This is why it is so important that we strive to reduce dosage in children to lessen the risk. At OHSU Doernbecher, child-size doses are used to image children. It is still interesting to note, however, that the authors of the aforementioned study point out that risk of everyday activities are far greater than the risk of radiation from a CT scan. For instance, it is 238 times more likely to die in a fatal car accident than from the radiation dose from a CT scan in the dose range of a pediatric exam. [Gerber et al. Circulation. 2009; 119: 1056-1065]

What should I ask about medical imaging – before or after the examination?

  • What kind of imaging study is ordered?
  • Does that exam require sedation or involve ionizing radiation?
  • Are there reasonable alternatives to having an imaging procedure that requires sedation or ionizing radiation?
  • Is the CT exam performed with ‘child sized’ techniques?

Thank you to Petra Vajtai, M.D., pediatric radiologist, and David Pettersson, M.D., resident in radiology, for providing information and research data used in this blog posting.

Dianna M. E. Bardo, M.D.
Associate Professor of Diagnostic Radiology, Pediatrics and Cardiovascular Medicine
OHSU Doernbecher Children’s Hospital