New scanners help cut kids' radiation risks
MILWAUKEE — It resembles a space-age capsule, in which a child stands on a platform while green laser beams capture images of the spine in a matter of seconds.
For scoliosis patients, this new EOS scanner at Children's Hospital of Wisconsin is about more than bells and whistles. It's all about reducing radiation doses in children whenever possible.
Attention has been trained on radiation doses after news reports in the last year of patients in hospitals in California and other states receiving overdoses while undergoing brain CT scans. The California cases prompted passage of a law in the summer that will require medical centers in that state to record radiation doses for each scan.
Dosage monitoring in children is not necessarily new for specialty centers, such as children's hospitals, but it's gained increased focus and awareness among physicians around the country.
"We don't know that the doses used in medical imaging cause cancer, but we need to act cautiously as if it does," said physician Marilyn Goske, a professor of radiology at Cincinnati Children's Hospital Medical Center and chairman of Image Gently, a national campaign that promotes radiation protection in children.
No medical studies have definitively shown what radiation dose is safest over a person's lifetime.
Physicians will consult with radiologists, technicians and medical physicists on which imaging technique is best to help diagnose a patient. It's a balancing act — the imaging technique has to be good enough for a doctor to see what's going on, but the goal is to keep the radiation dose as low as possible. For children, the cumulative radiation doses add up over a lifetime.
The key to deciding on medical imaging is for physicians to ask whether the information gained outweighs any risks, said Jeffrey Kanne, a radiologist who is vice chairman of quality and safety for the department of radiology at the University of Wisconsin School of Medicine and Public Health.
Doctors may first turn to an imaging technique that won't deliver a dose of radiation to a patient. Ultrasound and magnetic resonance imaging, or MRI, are two standbys, but both have their drawbacks as well.
Ultrasound typically is used to diagnose problems in the liver, spleen, gall bladder, kidneys, ovaries and testes.
"We use ultrasound whenever possible," and it will often answer the question, said physician Sheila Moore, medical director of pediatric radiology at Children's Hospital of Wisconsin and a professor at the Medical College of Wisconsin.
However, ultrasound won't produce an image of anything with air, such as lungs, because it can't see through it.
MRI also doesn't use radiation and can produce high-quality images. However, patients must stay still for long periods. The typical MRI takes 25 to 30 minutes, in 3- to 5-minute segments.
The MRI clinic at Children's Hospital of Wisconsin is the busiest imaging area in the hospital, according to Linda Flannery, nurse manager for the clinic. The clinic sees 35 to 40 patients a day. Some children are sedated to minimize movement; many watch movies during the imaging session. For children who have shunts that need monitoring, hospitals now have quick MRIs, in which kids don't have to be sedated for a 3-minute scan. Neurologists can use the imaging to check shunt placement and ventricle size.
CT scans, particularly head and abdominal imaging, are at the higher end on the radiation dosing scale. X-rays deliver the equivalent of one day of background radiation from soil, rocks, air, water and building materials. One CT scan of the head delivers the equivalent of up to eight months of background radiation; a CT scan of the abdomen is equal to up to 20 months of background radiation, according to Image Gently.
The number of CT scans has been increasing in the last decade, partly because many more medical centers and clinics have the scanners. It's estimated that between 4 million and 7 million children have CT scans each year. It's used not only to diagnose a disease or condition, such as examining the lungs, but also to help doctors plan for surgery.
"It's related to defensive medicine," Kanne said. "In emergency rooms, doctors are faced with patients they know little about. It's their job to make sure they aren't missing something life-threatening."
For orthopedic patients, doctors have traditionally relied on X-rays to show spine curvature, discrepancies in leg length or knee problems in children.
In scoliosis patients, the spine curves side to side, when viewed from the back. Many patients will get scans every six months so a physician can monitor their condition and figure out whether a treatment such as a brace or surgery is needed. A child may get 15 to 20 scans, depending on age.
The EOS scanner delivers one-tenth of the normal radiation dose of an X-ray. The clarity of the EOS films also is better than a standard X-ray, said John Thometz, medical director of orthopedic surgery at Children's Hospital and a professor at the Medical College of Wisconsin.
And, unlike an X-ray, the EOS can take a two-dimensional scan and create a three-dimensional image.
"Scoliosis is a 3-D deformity, and we just have these two-dimensional views," Thometz said.
"As the spine shifts over to the side, it rotates — that's where you get rib deformities," he said. "With 3-D, you get the orientation of individual bones in space and you get some quantification of what the rotational deformity is."
The Wisconsin EOS scanner — one of two in the nation — cost $450,000, part of which was donated by Variety-the Children's Charity of Wisconsin. Orthopedic patients aren't charged any differently than for a traditional X-ray or similar scan.
Whether it's an X-ray or CT scan, and depending on what needs imaging, shields are placed over a patient's chest, eyes and reproductive area to reduce radiation doses as much as possible, Moore said.
Clare Heaton, 5, has had a curvature in her spine since she was an infant and has been getting X-rays every four to six months since then, said her mother, Donna Heaton of Brookfield.
Her curvature is related to an extra piece of bone between two vertebrae and very near two growth plates, her mom said, so Thometz has monitored it closely. It's not painful for Clare, and Heaton said she's as active as her older brother.
"If the curvature happens to get worse, we will have to surgically have that (bone) removed," she said. So far it's been stable.
Radiation "certainly is a concern," Heaton said, "but having a healthy, strong spine is a concern as well."
For parents, whatever it takes to diagnose their children's ailments usually will edge out worries about radiation exposure. But for those kids who require frequent scans as part of their monitoring, radiation dosage becomes part of the equation.
"We don't want to be alarmist for parents. What we want them to do is get information so that they're aware that this is one factor in taking care of their child. It shouldn't be the only factor," Goske said. "If the physician that they're working with recommends a CT scan, it is very appropriate for them to say, 'Is this the best test for my child's situation?' "
She and Kanne said parents shouldn't hesitate to ask doctors about the radiation dosing to make sure a scan is using the lowest dose necessary for a pediatric patient. Newer scanners have settings for child patients, and many hospitals and clinics lease their scanners, so they likely will have newer equipment.
"Just because a center has it, though, doesn't mean people know how to use it," Kanne said. "Sometimes the switch isn't turned on."
He said pediatric dosage settings are embedded in the computer systems of the scanners and need to be activated.
But even when the lower settings are in place, that doesn't always tell technicians and doctors how much radiation the patients actually received. The new California law requires documentation of dosage output by a scanner, but, Goske said, it doesn't require reporting how much radiation a patient absorbed.
"It's a start, but, especially for children, it's not as accurate as we would like," she said.
She said doctors can measure skin dose and organ dose from a single scan, for example, but all of those have different meanings in terms of radiation absorption. Adding it all up is not easy.
Image Gently, a campaign by the Alliance for Radiation Safety in Pediatric Imaging, offers several resources for parents and patients: www.imagegently.org