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Cutting Radiation Exposure in Children in Need of Succeeding Brain Scans

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A team of pediatric neurosurgeons and neuroradiologists at the Johns Hopkins Children's Center have developed a technique of reducing harmful radiation exposure in children with a condition that calls for supplemental CT scans of the brain. The team claims to have effectively cut the rate of radiation exposure without compromising diagnostic accuracy of the images or treatment decisions.

Details of the discovery were noted in the Journal of Neurosurgery, where the team decided to use fewer X-ray snapshots or "slices" of the brain taken by CT scanners, only seven as opposed to the standard 32 to 40 slices. During the course of experimentation, the study also discovered reduced radiation exposure by a mean of just about 92 percent per patient in comparison to the standard head CT scans, while still depicting the images diagnostically accurate.

"The traditional thinking has been that fewer slices would, by definition, mean less clarity and less accuracy, rendering a CT scan suboptimal, but our findings show otherwise,” said lead investigator and chief neurosurgery resident at Johns Hopkins., Jonathan Pindrik, M.D.

The research included analysis of patients with disproportionate amounts of fluid in the brain, a condition known as hydrocephalus that calls for occasional fluid-draining surgeries and a head CT prior to each procedure. The team contrasted and compared two standard CT scans with two limited-slice, low-dose CT scans for each one of 50 children, aged 17 and younger, treated for hydrocephalus over the span of five years at Johns Hopkins Children's Center. The standard CT scan images were conducted before the launch of the new radiation-minimizing procedure.

"We have been searching for ways to minimize radiation exposure in kids without sacrificing the diagnostic accuracy of the images and that is no easy feat, but we believe our limited-slice CT scans achieved that balance," said senior study investigator and pediatric neurosurgeon at the Johns Hopkins Children's Center, Edward Ahn, M.D.

For all 50 patients, the radiation-minimizing approach delivered clear and 100 percent accurate images of the brain ventricles, which is the draining system that transports cerebrospinal fluid in and out of the brain. Yet, when documenting changes in the ventricle size, the low-dose approach resulted in a 4 percent error rate: Two of the 50 images were visually unclear, causing confusion among the physicians who reviewed them. There were no false negatives in the low-dose images, but three false positives, the study revealed; which more or less pointed to no cases of physicians falsely perceiving normal ventricular size, but three cases in which physicians perceived a change in ventricular size when there was none. All in all, the radiation-minimizing technique was clearly effective the researchers agree and did not compromise treatment results.Cutting Radiation Exposure in Children in Need of Succeeding Brain Scan

“The radiation-minimizing technique could be especially valuable in pediatric emergency rooms, where the need for quick diagnosis precludes the use of more cumbersome, radiation-free imaging alternatives like MRI. It also can be used for routine evaluation in smaller community hospitals that may lack MRI equipment,” said the Hopkins team.

“CT scans are invaluable imaging tools that have revolutionized the diagnosis and treatment of many conditions by providing fast, reliable and accurate images, but they have driven up levels of radiation exposure in both children and adults. Ionizing radiation, used in X-rays and CT scans, has been long implicated in the development of certain cancers because of its ability to damage DNA. Children are especially vulnerable to the effects of radiation because of their smaller size, growing tissues and rapidly dividing cells, and because of their longer lifespans that allow slow-growing cancers to emerge decades after exposure,” they added.

Hydrocephalus is usually treated by inserting a catheter that drains excess fluid from the brain into the abdomen, a process known as ventriculo-peritoneal shunting. Children with brain shunts require periodic imaging to evaluate and determine catheter position and function. Shunt failure that occurs when a catheter dislodges or infection sets in is a prevelant and hazardous complication. Yet, because shunt failure usually causes non-specific symptoms such as headache, vomiting, and fever a definitive diagnosis requires a brain scan.

As of now, there are over 62 million CT scans performed on an annual basis in the U.S. Four million of them in children. Researchers believe that radiation spawning from medical imaging is the single largest source of radiation exposure in the population, and that up to 2 percent of all cancers stem from exposure to medical radiation.

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