Case study: Pediatric dose reduction takes comprehensive commitment
“Over the last two years, we’ve looked at every part of the practice to reduce dose,” Sheila Moore, MD, medical director of radiology, told Health Imaging News. Dose reduction efforts start with exam orders.
After receiving an order for a CT or x-ray, technologists review the indication for the exam. If the tech suspects another modality might provide comparable or superior information, they call a radiologist, who, in turn, doubles back to the referring physician to review the indication and discuss an alternate modality when possible.
Generally, radiologists consider ultrasound before MRI because MRI is expensive and may require sedation, said Moore. However, in certain clinical scenarios MRI has replaced CT at Children’s Hospital. Take patients with shunts, who previously underwent CT studies every three to six months to measure ventricular size. The new protocol employs fast MRI; the five minute scan, said Moore, represents a huge dose reduction, provides the necessary data at the same costs as CT and usually bypasses sedation.
The radiology department relies on a similar model for repeat studies, checking patients’ imaging histories before completing any study. If a patient underwent a recent study, a radiologist calls the referring physician to remind him of the prior study and determine if a new indication prompted the study, offered Moore.
When only CT will do
“For some indications, CT is best,” affirmed Moore. The children’s hospital uses multiple methods to ensure the lowest possible CT dose, including a fairly new CT scanner. “If a hospital is in the market for a new system, dose reduction should be a primary focus [of the decision-making process], but it also helps to talk to manufacturers about how to lower dose on current scanners,” said Moore.
For example, existing CT systems can be retrofitted with updated reconstruction techniques to lower radiation dose.
Children’s Hospital of Wisconsin also verifies vendors’ dose estimates by putting dosimeters on all patients undergoing imaging studies. The dosimeters serve an additional purpose as they provide a starting point for the hospital’s efforts to track cumulative radiation dose and transmit the data to the patient record.
The hospital also emphasizes training and education for techs and radiologists to ensure that studies provide optimal image quality at the lowest possible dose. Both techs and physicians review radiation dose; techs verify AP and lateral scout images to calculate dose for every scan, and radiologists check dose as studies are transmitted to PACS.
The training efforts have reaped dividends as techs have embraced and developed low-dose strategies. For example, about a year ago, techs asked it if might be possible to cut mAs in half for scoliosis studies. Techs believed the protocol could reduce dose while providing adequate imaging quality. “With scoliosis studies, we’re focused on the curvature of the spine [versus more subtle findings like metastatic lesions,]” explained Moore. After reviewing studies, Moore and colleagues determined that the new protocol sufficed.
Other workflow efforts to reduce dose also center on the scoliosis clinic. “A lot of children with scoliosis don’t need x-rays, but they are ordered anyway. In our scoliosis clinic, nurse practitioners examine the patient before an x-ray is ordered,” explained Moore, who estimated that about 30 percent of the time scoliosis patients don’t require an x-ray. “It’s another way to drop dose.”
“Dose data should be in PACS, so it can be recorded for every patient and become part of the permanent record,” stated Moore. As the hospital plans for an upcoming EMR deployment, Moore has requested that the vendor build a mechanism for dose management into the system. “It will provide [an electronic method] that tracks cumulative dose.”
One of the final, and most recent, efforts in the hospital’s efforts to contain pediatric radiation dose is the installation of a low-dose scanner in its orthopedics clinic. The orthopedics department partnered with radiology to deploy the new system that acquires head-to-toe 2D and 3D images of patients in a standing position at a radiation dose up to 10 times less than x-ray and nearly 90 percent less than spine CT.
Currently, the hospital uses the system for scoliosis and leg-length studies. “These exams don’t require a lot of detail like a chest x-ray for a suspected subtle lesion, and the images are more than adequate for scoliosis,” explained Moore. Because the system images the whole-body in one image, radiologists no longer have to register two separate studies on PACS, a process than occasionally translates into duplicate studies and additional radiation dose if the patient moves between exams. Finally, the 3D datasets aid surgical planning, stated Moore, as scoliosis is a 3D disease and surgeons need to account for both rotation and curvature of the spine.
“The other piece of radiation dose reduction is educating the public about radiation safety,” summed Moore. The atomic bomb survivor data used to estimate cancer risk is “overblown. We can’t forget that CT has saved lives.”