Jana Schlütter | 2015-11-08
Pediatric imaging presents specific challenges that range from reducing X-ray doses as much as possible to creating an anxiety-free environment during imaging procedures. Innovative concepts and new technologies can help address these challenges.
Challenges in Pediatric Imaging
- Pediatric radiologists require additional training so that they can conduct anxiety-free exams and reduce potentially damaging X-ray radiation.
- Ultrasound is the preferred pediatric imaging method. The range of applications is growing.
- MRI1 scans can be stressful because of the noise and duration. Sedation can be avoided if trained therapists playfully educate the child.
- CT is often essential for accuracy and speed (e.g. in emergencies). Modern scanners and data-analysis methods have reduced radiation exposure.
- Conventional X-rays and fluoroscopies use less radiation thanks to new imaging technologies.
- Some open operations, for example on the heart and vascular system, can be avoided with the help of catheter-based treatment with an angiography system.
Ultrasound – the Method of Choice
Acquiring images of children is an art form. Different anatomical – and emotional – considerations must be taken into account, which is why ultrasound is such a popular method. Only the ultrasound transducer makes contact with the body, and there is close interaction between the patient and the sonographer or physician. Therefore, most children are not afraid. "The range of possible applications continues to grow," says Kassa Darge, a radiologist at The Children's Hospital of Philadelphia in the United States. Ultrasound has become the modality of choice for cases of suspected appendicitis.
Darge is conducting an FDA-approved clinical trial on the use of contrast-enhanced ultrasound (CEUS)2 by pediatric radiologists3. The trial focuses on voiding urosonography, which involves administering an ultrasound contrast medium (of gas-filled microbubbles) via a bladder catheter to test the ureter’s closure mechanism in children. If the mechanism is defective, urine can flow back out into the kidneys and cause high-fever infections and kidney damage. Before contrast ultrasound existed, physicians used an X-ray exam to make diagnoses. The method is particularly well-suited to children's body dimensions. Physicians can use high-frequency sound waves to achieve better imaging resolution without penetrating the tissue as deeply.
Low Dose is Crucial
Ultrasound does not expose patients to radiation. "Our first question is whether a diagnosis with ultrasound is possible. In more than 70 percent of abdominal problems, the answer is yes," explains Birgit Zieger, a pediatric radiologist at the Schwarzwald-Baar Klinikum in Villingen-Schwenningen, Germany. According to the ALARA principle, the radiation dose should always be "as low as reasonably achievable." Ionizing radiation can cause DNA strand breaks or other mutations. Since children are still developing and therefore more susceptible to damage from ionizing radiation, they have a statistically higher risk of developing cancer at some point.
However, pediatric radiology is not just characterized by the need to handle ionizing radiation extremely sensitively. "Children are not little adults," Kassa Darge points out. They suffer from different diseases, their immature organs often look very different on X-ray images, and other types of imaging might be more suitable depending on their age. All of this requires very special training, explains Darge. It can take one to three years, depending on local or regional regulations.
Radiation Doses in Pediatric Radiology
- Reducing radiation is key for pediatric radiology. Doses should be "as low as reasonably achievable" according to the ALARA principle, as promoted by the international "Image Gently" campaign.4
- Ionizing radiation can break DNA strands that cannot always be corrected by molecular repair systems. Frequent cell division is common in children and often transfers the genetic mutations to daughter cells. Since children have a long life expectancy, the risk is statistically higher that radiation-related DNA damage can result in cancer at some point.5 In addition, the reproductive cells in ovaries and testes can be damaged by radiation.
- CT scans are one of the major sources of childhood radiation exposure.6
- Radiation-free methods (e.g. MRI7, ultrasound) are often chosen over X-rays.
- Pediatric cardiologists/radiologists must consider if an exam is necessary, and choose the lowest possible dose and imaging quality.
- Modern CT scanners, sensitive X-ray detectors, and special image data analysis algorithms have substantially reduced X-ray radiation.
MRI in an Anxiety-free Environment
Magnetic resonance helps acquire an accurate diagnosis for many childhood diseases without the use of radiation8. However, the sound of the scanner can seem threatening to a child. Also, it is hard for small children to stay still for the time needed to perform an MRI scan. Sedation or general anesthesia is often required to prevent motion artifacts in children under seven years of age, and sometimes in older children.
"Occupational therapists use a model MRI device first," says Debbie Watson, head radiographer at Lady Cilento Children’s Hospital in Brisbane, Australia. "It looks just like an MRI scanner, and the typical sounds are played back." The children can watch their favorite movies in the scanner as a distraction. This approach has been shown to help avoid sedation, lowers costs, and makes it easier to use MRI on children9. Modern MRI scanners can also help to significantly improve the pediatric patient’s experience. Noise reduction, lightweight, high-density coils, or a 70 cm open bore are just some of the developments enabling scans to be increasingly faster and more patient friendly.
Key CT Factors
Speed and precision are the main arguments for computed tomography – in medical emergencies, for example. Surgical planning for congenital heart defects also usually requires a CT, says Dr. Mark Phillips, a pediatric radiologist specializing in pediatric heart patients at Lady Cilento Hospital. High-end equipment and innovative algorithms for image-data analysis mean that the radiation dose can often be reduced compared to older scanners.
"Depending on the clinical question, we also choose an image quality that is just sufficient," says Watson, "and we restrict the imaging range to the region we need." Modern technology also means that conventional X-ray imaging and fluoroscopy use substantially less radiation. These methods are used to display broken bones, locate swallowed objects, and evaluate the functions of the stomach and intestines, for example.
Reimbursement in Pediatric Imaging
Experts worldwide believe medical reimbursement is inadequate for pediatric radiology. "An exam that takes 10 to 20 minutes for adults can take up to 50 minutes with a child," says radiologist Kassa Darge. Pediatric radiologists must spend more time with young patients to get them to cooperate, and must carefully consider the suitable imaging methods beforehand and explain them to parents. However, age does not affect radiology reimbursement in the U.S., Australia, and European countries like Germany and Italy.
This can cause shortages of pediatric subspecialists and affect quality-oriented care.10 The German Radiological Society says there is only one pediatric radiologist per 150,000 children.11
Interventional Pediatric Imaging
Radiological interventions have now also replaced some surgical procedures used on children. For example, cardiac and vascular defects can be corrected using special catheters and devices, and cancer drugs can be targeted into the fine arteries of a liver tumor. In such cases, imaging processes often have to be combined, explains Walter Wohlgemuth, interventional radiologist at the University Medical Center Regensburg, Germany. With the help of ultrasound, physicians can direct a vascular catheter’s guide wire to its target, and only then switch to fluoroscopy. MRI and CT supplement the angiographic images with 3D information.
Pediatric cardiologist Giacomo Pongiglione from the Ospedale Pediatrico Bambino Gesù in Rome, Italy, is thinking a step further. He and his colleagues are working in European consortial projects to simulate a child's heart. The idea is to enter a child's specific MRI or CT data into a generic computer model of the heart and thus personalize the model. "We could then run through on the computer which treatment is beneficial for which child," says Pongiglione. Diagnostic testing, treatment, and prognosis would then blend together even more – and the art of pediatric imaging would be much the richer for it.
About the Author:
Jana Schlütter is an alumna of the Columbia University Graduate School of Journalism in New York. She works as a science editor for the Berlin newspaper Tagesspiegel. Her articles have also appeared in other major German daily and weekly newspapers, as well as in the weekly science journal Nature.
1MR scanning has not been established as safe for imaging fetuses and infants less than two years of age. The responsible physician must evaluate the benefits of the MR examination compared to those of other imaging procedures.
2At the time of publication, the U.S. Food and Drug Administration has cleared ultrasound contrast agents only for use in LVO. Check the current regulation for the country in which you are using this system for contrast agent clearance.
4http://imagegently.org. Accessed 5 July 2015
5DL Miglioretti, E Johnson, A Williams et al. (2013) The Use of Computed Tomography in Pediatrics and the Associated Radiation Exposure and Estimated Cancer Risk. JAMA Pediatr 167:700-7
6D Jackson, K Atkin, F Bettenay et al. (2015) Paediatric CT dose: a multicentre audit of subspecialty practice in Australia and New Zealand. Eur Radiol. 2015 Jun 3. [Epub ahead of print]
7MR scanning has not been established as safe for imaging fetuses and infants less than two years of age. The responsible physician must evaluate the benefits of the MR examination compared to those of other imaging procedures.
8MR scanning has not been established as safe for imaging fetuses and infants less than two years of age. The responsible physician must evaluate the benefits of the MR examination compared to those of other imaging procedures.
9Sze RW et al. (2014) The Economic Value of a Child Life Program for non-sedated MR Imaging. Children’s National Health System, Washington.
10Jewett EA, Anderson MR, Gilchrist GS (2005) The Pediatric Subspecialty Workforce: Public Policy and Forces for Change. Pediatrics 116:1192-1202; Heller RE (2013) The 21st-century radiology department: lessons from the pediatric section. Pediatr Radiol 43:536-8
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