“Child-Size” Radiation Dose

There is no doubt that medical imaging procedures save lives. However, one size does not fit all. Because children are three to five times more sensitive to radiation than adults,1 and cumulative radiation exposure can have adverse effects, it is critical for doctors to lower radiation levels when imaging a child.

That’s why in 2007, the Society for Pediatric Radiology (SPR) initiated the Alliance for Radiation Safety in Pediatric Imaging. Not long after, the American College of Radiology (ACR), the American Society of Radiologic Technologists (ASRT), and the American Association of Physicists in Medicine (AAPM) joined the Alliance. The Image Gently campaign is the Alliance’s initiative to raise awareness for lowering radiation dose used in pediatric imaging. The Alliance is actively working with imaging manufacturers to standardize dose assessment and display for children.
Although disagreements about the accuracy of the risk models or the degree to which the risks of radiation are emphasized are ongoing within the medical community, the message of the Image Gently campaign is clear: Reduce or “child-size” the amount of radiation used when obtaining a CT scan in children. To “child-size” the amount of radiation used, Image Gently encourages doctors to ask their medical physicist to determine the baseline radiation dose for an adult for that site’s equipment and compare that dose with the ACR Standards.2
While these guidelines are clear, it is not certain how widely doctors have implemented these radiation-reducing measures to date. To gage the impact Image Gently on medical imaging practices, Imaging Technology News (ITN) spoke with Marilyn Goske, M.D., chair of the Alliance, and Neil Johnson, M.D., president of the Society for Pediatric Imaging, both practice at Cincinnati Children’s Hospital.

ITN: How serious a risk does radiation imaging pose to children?
Dr. Goske: One of the first things we need to remember is when children have imaging it is being done for an indicated medical condition and for a benefit for that patient. That is really what the Image Gently campaign revolves around. Once a study if medically indicated it behooves all of us in pediatric imaging to promote radiation protection and try to lower the dose and still maintain the quality of the exam so that we get the diagnostic information that we need. We know from studies, particularly from the atomic bomb survivors in Japan, that if children receive radiation from a bomb blast such as that one, they are more sensitive to radiation. Now medical imaging is different as it’s a different form of energy and quite diffrent in how it’s given for the imaging test, but it’s the best we have. The data from that tells us that we need to be overly cautious and conservative, and that if we are going to use this technology, we want to use it in the safest way possible.

ITN: How exactly is the Alliance standardizing dose assessment and display for children?
Dr. Goske: We are working together under the direction of Keith Straus, who is the medical physicist at Boston Children’s Hospital, Mr. Tom Toth, who is the former chief physicist at GE Healthcare, and Stephen Vastaghat the Medical Imaging Technology Alliance (MITA).
The four major CT vendors have signed on to come up with more standardized dose displays so that when we complete a CT scan and we look at the images on task and that we have the information we need to interpret the information more accurately. Under the current system the CT dose that is displayed, which is the CT dye volume and the DLC are based on 32-centimeter adult-size phantoms. So if the patient is on the table and is exactly the same size as the phantom, the dose display is reasonably accurate. But in our patient population where you have an infant who weighs 5 lbs., for example, the younger they are, the smaller they are compared to the size of the phantom, and the more discrepant the dose display is. According Mr. Strauss in a paper that he published,3 the dose display can be off by a factor of three. So we are actually underestimating radiation dose for those small patients. We are working with numbers to get those displays more accurate so that radiologists, radiologic technologists and medical physicists have a better idea of what our smaller patients are really getting in terms of radiation dose during CT scans and other imaging procedures.

Dr. Johnson: It’s a very simplistic but important idea that we give our patients the right dose. We use the analogy of flying. We all fly in a commercial aircrafts, so we take risks. But there is a huge benefit when we minimize the risk. What we are trying to do is minimize the dose of radiation to children. We are not trying to stop these scans when they are needed medically. We are trying to do them with the minimum dose possible to reduce the risk where possible and get the job done at the same time.
A new, free PQI program, Image Gently: Practice Quality Improvement (PQI) in Computed Tomography (CT) Scans in Children, authored by the Chair of the Alliance for Radiation Safety in Pediatric Imaging, Dr. Marilyn Goske, and co-authors at Cincinnati Children’s Hospital, with funding from the SPR Research and Education Foundation, has been qualified by the American Board of Radiology (ABR) to fulfill Part IV, Assessment of Performance in Practice for Maintenance of Certification (MOC) for diagnostic radiologists.

ITN: What are some key benchmarks radiology practices should look to when implementing quality improvements?
Dr. Goske: First of all, Practice Quality Improvement is an implementation that radiologists can use to look at their practice and see areas that they want to improve on.
One of the challenges is that many radiologists don’t have the background in this to do this, even though they want to do the best for their patients. So what the Image Gently: Practice Quality Improvement module is, that is on the Image Gently Web site, walks the radiologist performing CT scans in children through a series of steps, so that when he or she completes the module they can actually promote changes in their department and implement changes that improve the quality of CT scans for children. For example, one of the things that Image Gently promotes is medical literacy for parents. We want parents to know something about the medical test their child is getting and understand the benefits as well as the risk involved. So there is a pamphlet that is downloadable on the Image Gently web site, and in fact, it is translated into nine different languages. The PQI project tries to give the radiologist medical evidence about what are some of the changes they should try to implement and then it also tries to give them those tools to implement those changes.

ITN: Image Gently recently rolled out Step Lightly for interventional radiology. What has been the response from that community?
Dr. Johnson: I am an interventional radiologist, and the pediatric interventional groups took on this challenge with Image Gently and we have just tailored the message for interventional radiologists.
Now interventional radiology really means they are doing image-guided surgical procedures, usually through a very small hole. We make a small incision and we do the same sort of things as a surgeon. So while we are doing that we use two basic technologies to guide us. One is ultrasound, which has no radiation, and the other is X-ray like fluoroscopy and CT scans. So it is the same thing in that while we are doing these medical procedures.
For example, I just did an abscess on a child who had a ruptured kidney. In the past that child might have gone to surgery, and that’s very difficult surgery where there’s a big abscess. So we drained it, so the surgeon could have a very easy operation in a couple of weeks. To do that you use a very small amount of radiation to guide our tubes and that’s necessary to save the patient all sorts of risk and that’s much, much better.
The amount of radiation in most of our procedures is small. But sometimes, when we are doing cardiac tests and angiography, the radiation is quite substantial. Again, we are not trying to stop anyone from using radiation-based procedures. But while we are doing those procedures, we encourage all pediatric radiologists to use as minimum fluoroscopy required to get the job done, to change the technical factors of the machine to reduce the radiation to use the minimum but still getting the job done.
Dr. Goske: One of the things that Dr. Manrita Sidhu, who lead that campaign, did was to develop a number of educational tools. One is the Step Lightly sticker that you put on the fluoroscopy tour as a visual reminder to those performing interventional procedures to try to use lower dose, keep your foot off the pedal, step lightly and only use it when necessary. They also developed a safety checklist that can be used for every patient where the interventional radiologist and their team goes down the safety checklist to make sure that led shielding is present and everyone in the room is wearing goggles; just common sense things that is organized for you provided free on the web site. Another thing her group developed is a power point presentation that anyone in the country can download and give to their interventional radiologists and to the nurses and the radiologic technologists who are working in the room during the procedure.
People want to do the right thing and it gives them the tools to learn and go about practicing in a safer way for our patients.
Dr. Johnson: While interventional radiology is a very small subspecialty, we are working very closely with the major manufacturers of equipment to add features and add the ability to reduce dose appropriate for children on these essentially adult machines as it would be commercially impractical to sell these machines just for children. Whilst we do have to use these normal machines, we do have some very important technical differences.

ITN: What will be the next roll out programs in the coming year?
Dr. Goske: Dr. Steven Don at Washington University is a pediatric radiologist is an expert in CR and DR. In February of 2010 Washington University department of radiology is going to be hosting an Image Gently CR/DR vendor summit. And we are thrilled that we have already been working with the meeting for not only radiologists, technologists and physicists, who are participating in the program but also the major vendors of CR and DR equipment. They will hear why we need this information for our patients and we can have a wonderful discussion to help move forward to enhance radiation protection for children.
The second part of the vendor summit in the afternoon help promote developing educational materials. We are expanding the educational material on the Image Gently web site for CT for CT technologists. We are trying to give CT technologists who perform CT exams on children at least seven modules that will be on the Image Gently web site, and give them the tools that they need to decrease radiation when they are performing CT scans on children. Dr. Don and his group will be developing those tools. We have been working with Greg Morrison at ASRT who has provided the resources to produce the online presentation. So there is an educational component as well as working with the manufacturers.
Dr. Johnson: The interventional program is working with the fluoroscopy business. It is far more common to use fluoroscopy in interventional radiology. So again it’s a programmatic distinction to all the subspecialties, to pediatric radiology and radiology in general the radiology subspecialties.
Dr. Goske: In April, at the Society for Pediatric Radiology annual meeting, Dr. Ted Treves who is an expert in pediatric nuclear medicine is convening a conference to image gently to try to get a national consensus on standardizing dose of administered radiopharmaceuticals for pediatric nuclear medicine studies.
We are really very grateful to the many volunteers that make Image Gently what it really is.

Reference:
1. American College of Radiology Web site. Alliance for Radiation Safety in Pediatric Imaging and Imaging Manufacturers Agree to Collaborate to Standardize Methods to Measure, Report Pediatric Dose from CT Scans. http://www.acr.org/MainMenuCategories/media_room/FeaturedCategories/Pre…
2. American College of Radiology (ACR) Web site. Guidelines and standards. www.acr.org/SecondaryMainMenuCategories/quality_safety/guidelines.aspx. Accessed December 12, 2007.
3. Strauss KJ, Goske MJ, Frush DP, Butler PL, Morrison G. Image gently vendor summit: working together for better estimates of pediatric radiation dose from CT. AJR (2009) 192:1169-1175.