Individuals with hydrocephalus frequently have multiple computerized tomography (CT) scans to evaluate shunt function. A CT scan, also called a CAT scan, is a diagnostic tool that combines a series of x-ray views and computer technology to create an image of the body. CT scans provide more detailed information than standard x-rays and can be a lifesaving tool in diagnosing hydrocephalus and in some cases, identifying shunt failure quickly. However, these scans do not come without risk.
The dose of radiation delivered during a CT scan is 100 to 500 times higher than traditional radiography. CT/CAT scans and MRIs are often used in the diagnosis and follow-ups for patients with hydrocephalus. While MRIs are a way to avoid exposure to radiation, many patients do not have a choice between an MRI and CT scan, either because there is no availability to a MRI machine or the patient cannot have an MRI for various medical reasons. Studies have showed that the use of CT scans has increased in the last two decades, especially for pediatrics. The radiation exposure from CT scans has caused concerns among parents and patients because of potential risk factors. In a study published in JAMA pediatrics in June 2013, researchers at the University of California, Davis evaluated the association of the use of CT scans in pediatrics and subsequent cancer risk, finding a link between the two. The paper also found that the use of CT scans vary widely in clinical practice and suggests that there is an opportunity to reduce the dose of radiation through standardized protocols. It is not uncommon for children with hydrocephalus to undergo numerous CT scans throughout their life, raising the concern about the effects of the radiation exposure for the future. Studies such as the JAMA pediatric paper continue to bring awareness to the need for better understanding and standardized protocols for the utilization of CT scans in children.
In a new study published in the Journal of Neurosurgery, Edward Ahn MD and colleagues at Johns Hopkins wanted to determine if there could be a way to limit the amount of radiation children with hydrocephalus receive during CT scans. This study explored the use of limited-sequence head CT scans for children with hydrocephalus, which limits the radiation exposure by taking seven slices or snapshots instead of the standard 32 to 40 slices. Traditionally, standard CT scans are considered to provide a better picture of the brain while limited sequence scans, which take fewer slices, are considered to provide less clarity and accuracy in determining shunt function and therefore limits the knowledge a clinician needs to make treatment decisions. The study entitled, Analysis of limited-sequence head computed tomography for children with shunted hydrocephalus: potential to reduce diagnostic radiation exposure aimed to determine if limited-sequence CT scans can accurately evaluate children with hydrocephalus with the goal of reducing radiation exposure.
For this study, researchers reviewed standard CT scans and limited-sequence CT scans of 50 children aged zero to 17. The average number of total head CT scans for each patient was 13.4 for the four-year period. Approximately, 42% of the study participants had at least 6 CT scans in one year. A total of 23% of the patients had received 18 head CT scans over the four-year study period. Two pediatric neuroradiologists and one neurosurgeon reviewed the scans. According to Dr. Ahn, they “determine that limited sequence CT was sufficiently accurate at detecting shunt malfunctions and estimated that the limited sequence will reduce radiation doses by an average of 91.8% compared to standard head CTs.” The researchers concluded that the limited-sequence scans were adequate and would not have compromised clinical outcomes. Based on these results, Dr. Ahn is looking to the next step of the research, “we are currently conducting a trial with the limited sequence head CT in the Johns Hopkins Pediatric Emergency Room. We hope to find similar results so that the limited sequence CT can be implemented in other emergency rooms that treat children with shunted hydrocephalus.” It is noted that the limited sequence protocol would not be applicable for initial screenings of suspected hydrocephalus, visualization of lesions or abnormalities outside the ventricular system, trauma or evaluation of intracranial mass or lesion.
Children with hydrocephalus represent a population that is susceptible to frequent imaging. The standard treatment method, a shunt, has high failure and malfunction rates, with approximately 40 to 50% of shunts failing in the first two years after placement. With the multiple imaging, this population has great concerns about the exposure to radiation and the potential future outcomes. The ability to find solutions that will lower a child’s exposure rate while still providing the clinically relevant information is highly sought. This study provides evidence that limited-sequence CT scans could have the potential to provide this needed balance. The question becomes whether hospital and clinicians adopt limited-sequence CT scans in the evaluation of children with hydrocephalus.