Frequently Asked Questions

FAQs - CT

The amount of radiation that people are receiving from medical sources is increasing, and this includes children.  It is difficult to show directly that radiation doses from CT lead to cancer.  However, good data from other sources of exposure show that there are increased cancers in people who have been exposed to radiation at levels that can be encountered by patients undergoing CT scans.  This is particularly important in children, whose tissues are more radiosensitive, who receive a larger effective dose for a given level of radiation, and who have a longer time to develop cancers resulting from radiation exposure.  For any one person, the lifetime risk of death from cancer is about 1 in 5.  While estimates vary, for a child undergoing a single CT of the abdomen and pelvis increases that risk by 1 in 1,000.  The risk is cumulative, however, and each subsequent CT scan will increase the risk accordingly.  While for any one individual the increased risk is very small, given the large number of CT scans performed the risk to the population as a whole is much larger.

Do children really undergo many CT scans?

The population of the United States is second only to Japan in per capita CT exams performed.  There are approximately 7 million CT studies performed in children every year in the United States, and the number is increasing approximately 10% per year.  CT is widely used among all ages of children, with 33% performed in children under 10 years of age.  CT is the largest contributor to medical radiation dose in the United States.

Can the risk from CT be lessened while still obtaining diagnostic quality studies?

Absolutely.  There are many techniques that can be used to dramatically lessen the amount of radiation children are exposed to during CT, while still enabling diagnostic quality images (see also What Can I Do? Section).  These include:
Scan only the area required.  Scanning beyond the body regions where there is clinical concern results in needless exposure.
Reduce tube output (kVp and mAS).  Exposure parameters should be reduced for the smaller patient size.  A number of suggested protocols are available (click here)

  • Perform single phase studies.  Most pediatric conditions are readily diagnosable with single phase CT; more phases unnecessarily increases radiation dose without adding to diagnoses.
  • Use breast shields for girls undergoing chest CT studies.
  • Should I not order CT scans for my pediatric patients?

CT is an extremely useful imaging modality that can provide valuable and even life-saving medical information, and thus can provide more benefit than harm.  Like any test, there should be clear reasons to order a CT scan.  For many indications, a test like ultrasound or magnetic resonance imaging may provide the same information without exposing a child to radiation.  The American College of Radiology (ACR) has imaging appropriateness criteria for a number of pediatric conditions and discusses the utility of various imaging strategies.  Discussing the clinical situation and the medical information desired with the pediatric radiologists providing your imaging services can help determine if an alternative test might be better.  If a CT scan is needed, make sure that your imaging facility uses appropriate radiation reduction protocols and techniques, and that those interpreting these pediatric studies are qualified.

How can I determine if my imaging providers are using appropriate CT techniques?

Without asking, you won’t know.  Some facilities may not alter dose technique for studies on children. This website has published a straightforward method that can be implemented at your site with the help of a medical physicist. It is unique in that it does not depend on the manufacturer, model or age of the scanner. While there may be variability depending upon CT scanner manufacturer and institution, there are also a number of published suggested techniques that facilities can use that provide substantial dose savings. Similarly, most adult protocols call for scanning the same area several times (multiple phases); this is rarely required for pediatric conditions and results in needless additional radiation exposure. 

Ask:

  • if your imaging facility is accredited by the American College of Radiology (ACR)
  • if the CT technologists are credentialed
  • if a board certified radiologist or pediatric radiologist will be interpreting the study
  • Should I talk to parents about the risks involved in getting a CT?

The long-term risks of exposure to medical radiation are small but real.  However, the diagnostic value that a CT can provide in the short-term usually far outweighs the long-term risks.  Most patients are not informed of any potential risks from radiation prior to the exam (Lee CI, et al. Diagnostic  CT scans: assessment of patient, physician and radiologist awareness of radiation dose and possible risk. Radiology 2004;231:393-398), although some institutions are requiring patient informed consent prior to undergoing CT.  While it seems like this would deter patients from getting potentially important exams performed, a recent research study found that parents who were told about the risks and benefits of CT still agreed to go ahead and have the study performed (Larson DB, et al. Informing parents about CT radiation exposure in children: it’s OK to tell them.  AJR 2007;189:271-275).  In short, you should not hesitate to discuss the potential risks of CT radiation with patients and families.

Where can I find guidelines/protocols for pediatric CT?

Return to the “What can I Do?” section of this website for specific suggestions and guidelines for every member of the Imaging team including protocol recommendations.

Is there an increased risk of cancer from medical radiation, especially CT scans?
While no one can point to a single individual and say that their cancer was caused by medical radiation, there is increasingly strong evidence that exposures to radiation levels found during CT scans may slightly increase the risk of future cancer.  The estimated risk for developing cancer is variable, but for every 1000 children undergoing a single CT scan of the abdomen there will be 1 cancer caused by CT (risk of 1 in 1,000).  This needs to be interpreted against the risk of developing cancer over one’s lifetime.  For those same 1,000 children, 200 will eventually develop cancer regardless of exposure to medical radiation (risk of 1 in 5).  So the additional risk is small, but the best available research indicates that there is in fact some risk.

If my doctor orders a CT scan, should I let my child have it?
Like any medical test, the beneficial information gained from the test should outweigh the risk of having the test performed.  CT is a very powerful and valuable imaging technique that can provide important and even life-saving information.  Sometimes, however, imaging tests like ultrasound and magnetic resonance imaging (MRI) can provide the same information as CT but not expose your child to any radiation.  You should ask your doctor and imaging provider whether these alternatives are appropriate for your child’s situation.  If a CT is the best test, then make sure that your imaging provider uses appropriate low dose techniques to minimize radiation exposure during the test.

How can I be sure that my imaging facility is using appropriate reduced radiation techniques?
Some  facilities that perform CT scans on adults do not use radiation dose reduction techniques when scanning children.  You won’t know unless you ask, and it is reasonable and within your rights to do so.  Your imaging provider should be able to provide you with information about what they do to reduce radiation doses during CT (such as reducing CT tube output, performing single phase scans, reducing exposure to areas away from the clinical concern, etc.).  Other things to ask about include whether the facility has American College of Radiology accreditation, whether the CT technologists are credentialled, and if the person interpreting the studies is a board-certified radiologist or pediatric radiologist.

Who should I talk to about my concerns?
Any discussion should start with your child’s physician.  They will know or can inquire if the imaging center to which they refer utilizes appropriate pediatric CT scanning techniques, and if a non-radiation imaging test might be as useful for your child’s situation.  If not, you should ask to speak with the technologist or radiologist at your imaging facility so that your concerns and questions can be answered.  Additional information can also be found elsewhere in this website, and at the links provided.

Last week my 4-year-old son began complaining of headaches after saying he had fallen earlier in the day.  He then began to vomit, and our pediatrician referred us to a local hospital emergency department for evaluation.  Although my son was doing better, the emergency department doctor ordered a brain CT scan to make sure that there was nothing wrong.  He did not discuss with us the risk of radiation before the exam.  Fortunately, the CT scan was normal and my son is fine.  Now, however, I have begun to worry that by letting them do the CT scan, and that we may have needlessly exposed him to radiation that could harm him later in life.  Did we do the right thing?
The decision to perform any imaging test is based on many factors and it is easy to second-guess decisions after the fact, especially when the results are normal.  For the situation you have described, even if the physician had discussed the radiation issues before the test, the CT would still be performed to exclude that there were no serious problems for your son.  The very small risk from radiation exposure from this one exam is much less than the risk of missing a brain injury from his fall.  If similar situations arise in the future, it is always reasonable to ask your physician if there are other methods of getting the same medical information that do not require radiation exposure, and if the facility providing the imaging uses dose reduction techniques wherever possible.

Our daughter was born prematurely and had a prolonged and difficult hospital stay, not coming home until she was four months old.  During that time, she had many x-rays for her chest (she was on a ventilator), some fluoroscopy studies (for placing feeding tubes), and several CT scans of her brain (she had some bleeding problems).  She was left with some mild cerebral palsy, and she has had other x-rays since.  Now that she is 16 years old, I am wondering if she has a higher risk of getting cancer because of all of those x-rays and CT scans that she was exposed to?

Minimizing radiation exposure to the newborn is especially important, since the younger the child, the more sensitive their tissues are to the effects of radiation.  However, in the complex medical scenario that you describe with your daughter, imaging is often vital to proper medical treatment.  In a premature infant, chest radiographs are often necessary to make sure that life saving lines and tubes are in the proper place, and brain imaging is often needed to make sure that there is no brain injury that might need special treatment.  Again, it is a balance between medical need and the very small future risk that most experts think exists for medical radiation.  As far as her individual increased risk of getting cancer as she gets older, it is much smaller than the risks that we take every day, such as driving a car.  There is no need to do special screening tests or take other special measures. 


I was in a car crash as a teenager, and had several CT scans and x-rays while I was in the hospital.  Now that I am 32 years old, I am worried about my risk of cancer.  What cancers should I be looking out for?
The risk to you from the CT scans you had while evaluating your injuries from a car accident is likely very much less than the risks those injuries might have caused you.  There really is no need to undergo any special screening for cancer because you have had CT scans.  Further, there is no specific type of cancer that is more likely to develop as a result of normal diagnostic radiation exposures, and there is no way to tell if any individual cancer was caused by radiation.  You should follow the screening recommendations of your physician as is appropriate for your age and family history, but special screening is not needed.

Our family travels a lot.  We recently had to go through on of those new x-ray screening systems.  I know that they are supposed to be “safe”, but I am concerned about the radiation that my children received, as well as the radiation I will receive when flying for business.  Are these new x-ray scanners really safe?
The whole body x-ray scanners that are being introduced for increased airport security work very differently from the x-ray machines that screen your luggage, and from medical x-ray equipment.  Traditional x-ray images are made when an x-ray beam travels through an object (whether a person or a carry-on bag) and makes an image that depends upon the relative amount of x-rays that pass through the object.  Airport body scanners use an extremely low dose of x-rays and make an image by recording the number of x-rays that are reflected back from the person.  In this way, hidden objects that are harder than normal soft tissue can be detected.  The dose delivered to anyone is equal to only about 15 minutes of daily background radiation.  Most of the x-rays do not even penetrate below the level of the skin.  Other whole body scanners do not use x-rays at all, instead using what are essentially radio waves to image through clothing.  So while people may have many reasons to object to these new scanners, concerns about excessive radiation exposure should not be one of them.

I understand that children are more sensitive to radiation, and that reducing their exposure is important.  However, I have recently had to have several x-ray studies, including two CT scans, and I wonder if anyone is doing anything about radiation exposure in adults?
Since its creation by the four founding member societies, the Alliance for Radiation Safety in Pediatric Imaging has grown to include over 60 societies, including 21 international, who share our concern and support our efforts to responsibly reduce radiation exposure for children.  One of the gratifying results of this effort has been recognition of the need to reduce radiation exposure for all patients undergoing medical imaging.  To that end, the American College of Radiology and other societies have begun a campaign analogous to Image Gently®, called Image Wisely.  Recognizing that radiation reduction is important for all patients, the Image Wisely campaign seeks to achieve the same awareness and change of practice for adults that Image Gently has done for children.

What is The Alliance for Radiation Safety in Pediatric Imaging?
The Alliance is a consortium of professional societies who are concerned radiation exposure children receive when undergoing medical imaging procedures.  As of March 2011, 63 societies representing the fields of radiology, pediatrics, and medical physics and radiation safety are involved.  The Alliance recognizes the often life-saving value of medical imaging..  However, techniques used in pediatric imaging may not be  tailored to children’s smaller bodies, resulting in radiation exposures that are greater than necessary.  This is especially true for CT scans.

Do children really undergo many CT scans
The population of the United States is second only to Japan in per capita CT exams performed.  There are approximately 7 million CT studies performed in children every year in the United States, and the number is increasing approximately 10% per year.  CT is widely used among all ages of children, with 33% performed in children under 10 years of age.  CT is the largest contributor to medical radiation dose in the United States.

Does CT radiation really pose a risk to children?
The amount of radiation that people are receiving from medical sources is increasing, and this includes children.  It is difficult to show directly that radiation doses from CT lead directly to cancer.  However, good data from other sources of exposure show that there are increased cancers in people who have been exposed to radiation at levels now encountered by patients undergoing CT scans.  This is particularly important in children, whose tissues are more radiosensitive, who receive a larger effective dose for a given level of radiation, and who have a longer time to develop cancers resulting from radiation exposure.  For any one person, the risk of death from cancer is about 1 in 5.  While estimates vary, for a child undergoing a single CT of the abdomen and pelvis increases that risk by 1 in 1,000.  The risk is cumulative, however, and each subsequent CT scan will increase the risk accordingly.  While for any one individual the increased risk is very small, given the large number of CT scans performed the risk to the population as a whole is much larger.

Where can I find out more information about The Alliance and these issues?
Links to other useful sites and information sources can be found on this website.  Specific questions or interview requests should be directed through the “Contact Us” section of this website.

Other FAQs

Interventional

Frequently Asked Questions

The topic of interventional radiology radiation exposure and potential future cancer risk raises many different questions among health professionals, families and the community. 

Links to More Information

Further information is available on many of the websites of members of The Alliance.  There is a wealth of information available online; some useful sites are listed below:

  • The Radiation Protection of patients website of the IAEA has wealth of information for children and adults.
  • The American College of Radiology has recently published a broader overview of the issues of radiation dose in medicine. Find the White paper here.  
  • Facilities that are knowledgeable on pediatric imaging have been shown to use lower radiation dose techniques than most general facilities.  A guide to pediatric interventional radiology services near you can be found on the Society for Pediatric Interventional Radiology website www.spirweb.org
  • The Society for Pediatric Radiology provides information about pediatric radiology, including pediatric interventional radiology at www.pedrad.org 
  • The Society for Interventional Radiology provides information about interventional radiology, including pediatric interventional radiology at www.sirweb.org 
  • The website www.RadiologyInfo.org  is a collaboration between the American College of Radiology and the Radiology Society of North America that provides information about many interventional radiology procedures. Pediatric specific updates are in progress. Information about radiation exposure can be found here:  http://www.radiologyinfo.org/en/safety/index.cfm?pg=sfty_xray 
  • The National Cancer Institute provides general information about interventional fluoroscopy. Future pediatric specific updates are being planned. Find the information here http://www.cancer.gov/cancertopics/interventionalfluoroscopy/page1.  
  • The United States Food and Drug Administration has published recommendations for reducing radiation risk. Find it here.  



 

Dental

 

Nuclear Medicine

FAQs - Fluoroscopy

Medical Professionals

Background

Medical sources of radiation to the population are increasing. This is of particular concern in children whose tissues are more radiosensitive, whose organs receive a larger effective dose for a given level of radiation, and who have increased time to develop cancers as a result of radiation exposure. It is difficult to demonstrate that radiation doses from medical imaging lead directly to cancer or to state with certainty the exact risk of cancer related to medical radiation;  however  the committee on the Biological Effects of Ionizing Radiation (BEIR) VII states “… the risk of cancer proceeds in a linear fashion at lower doses without a threshold and … the smallest dose has the potential to cause a small increase in risk to humans.”    Good data from other sources of exposure do show that there is an increased incidence of cancers in people exposed to levels now encountered through medical sources. For any one person, the overall baseline risk of death from cancer is about 1 in 5.  While estimates regarding additional risk from radiation exposure vary, a child undergoing a single CT of the abdomen and pelvis may increase that risk by 1 in 1,000. While for any one individual the potentially increased risk is very small, the risk to the population as a whole is larger. We do know that the risk is cumulative with repeated radiation exposure. Therefore all studies that expose a child to ionizing radiation should be carefully evaluated as to the potential risk versus the likely benefit. 

Fluoroscopic studies entail radiation exposure to not only  the patient but also (to a much lesser extent) the fluroscopist and other assisting .personnel. This is especially true in children in whom several persons are often required to effectively immobilize and position the child .

The amount of radiation resulting from fluoroscopic procedures is highly variable, dependent upon fluoroscopic parameters which in turn depend upon several factors, including patient size and desired image detail.  The type of procedure performed has a great impact upon patient dose, with those procedures which require long fluoroscopy times, such as interventional procedures, providing the largest doses.

Effective radiation dose for a VCUG has been reported as approximately .5 to 3.2 mSv and an upper gastrointestinal series as 1.2 - 6.5mSv. as compared to the average dose of an abdominal CT in a child  of approximately 6mSv.

Do children undergo many fluoroscopic studies?
The availability of endoscopy and CT has resulted in a decline in fluoroscopic procedures; nonetheless fluoroscopy remains an important and frequently used procedure in the pediatric patient, particularly in the US. In a  survey of pediatric radiologists conducted by SCORCH (Society of Chairmen of Radiology in Children’s Hospitals) in 2007  the mean number of annual fluoroscopies reported per surveyed hospital was 4,296.  Approximately 35% of pediatric fluoroscopic studies are voiding cystourethrograms (VCUG), 30% upper gastrointestinal studies( UGI), and 7% contrast enemas, with miscellaneous categories comprising the remainder.  In addition to Diagnostic Imaging, there are several other sources of fluoroscopic radiation, including fluoroscopy for orthopedic procedures, fluoroscopy in the OR for central line placements and other procedures, and fluoroscopy by other services, such as Gastroenterology and Cardiology.

Can the risk from fluoroscopic studies be lessened while still obtaining diagnostic studies?
Absolutely. There are many techniques that can be used that dramatically decrease the amount of radiation children are exposed to while still allowing diagnostic quality images  (See sections on individual studies (UGI, VCUG, Contrast enema, Information for Radiologists, General Principles for Clinical Diagnostic examinations)

These include:

Having a clear understanding of the patient’s problems and goals of the study is important, and providing a detailed history to the radiologist is very important to achieve this goal.   It is also very important to limit fluoroscopic time in general  and use of magnification mode in particular; careful collimation to the area of interest  and appropriate shielding, bringing the x-ray source as close as possible to the image intensifier, matching tube output (kVp and mAs) to the size of the child, utilizing grid- controlled pulsed digital fluoroscopic equipment with adjustable frame speeds and half dose key as well as last image hold and capture capability are also important measures to optimize the examination.

While there may be intrinsic variability dependent upon equipment manufacturer and institution, there are  a number of published suggested techniques that facilities can use that provide substantial dose savings. Work with a physicist is very important in the appropriate set-up of fluoroscopic equipment, particularly its adaptation to optimal pediatric imaging

Should I not request fluoroscopic studies in my pediatric patients?
Fluoroscopic studies are often very useful and can provide valuable and even lifesaving medical information. As with any test, there should be clear reasons to order the study. In some situations ultrasound  or occasionally magnetic resonance imaging could provide similar information without exposing a child to radiation. The American College of Radiology (ACR) publishes appropriateness criteria for pediatric conditions that discuss the utility of various imaging strategies. Discussing the clinical situation and medical information with the pediatric radiologists providing your imaging services can help determine whether an alternative test might be better. If a fluoroscopic study is needed, ensure that your imaging facility uses appropriate fluoroscopic equipment, protocols and techniques for children, and that those performing and interpreting these pediatric studies are qualified and  experienced. 

How can I determine if my imaging providers are using appropriate fluoroscopic imaging techniques?
Without asking, you won’t know. Some facilities may not have fluoroscopic equipment suitable for children or experienced personnel who frequently perform pediatric procedures and may not adequately adjust dose techniques for children or limit the fluoroscopic time and number of spot films or overhead X-rays that are  typically obtained in adults.

Ask:

  • If the facility is accredited by the ACR
  • If the technologists are credentialed
  • How frequently the facility performs the requested fluoroscopic study in children
  • If the equipment is optimized for pediatric patients
  • If a board certified radiologist or pediatric radiologist will be performing and interpreting the study

Should I talk to parents about the radiation risk of a fluoroscopic study?

The diagnostic benefit that the study can provide in the short-term usually outweighs the long-term risks. While it seems that informing parents might deter them from acquiescing with potentially important studies, recent research regarding CT found that parents who were told about the risks and benefits still agreed to have the study performed ( Larson DB, et al. Informing parents about CT radiation exposure in children: it’s OK to tell them.  AJR 2007;189:271-275).. You should not hesitate to discuss the potential radiation risks with patients and families.

Where can I find guidelines/protocols for pediatric fluoroscopic studies?
Return to the “What can I do?” section of this website for specific guidelines and suggestions for every member of  the imaging team including specific recommendations.

Beverly Newman, MD, FACR

Parents