Study: New skeletal dosimetry model for newborns based on 3D microCT

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An image-based skeletal dosimetry model for the International Commission on Radiological Protection reference newborn accounts for the unique 3D microstructure of newborn marrow cavities and bone trabeculae as seen under microCT imaging, suggesting that radiation doses to newborn bone marrow have been overestimated by existing clinical skeletal models, according to an article published in the March 5 issue of Physics in Medicine and Biology.

Variations in tissue and bone can affect how much radiation is absorbed by the body and the researchers used 3D microCT imaging to describe cartilage, bone marrow and two types of mineral bone in 20 different skeletal sites from two newborns.

"We're building a rich library of computer simulation tools and 3D patient models that will make dose estimates much more accurate and patient-specific," said Wesley E. Bolch, PhD, professor in the department of nuclear and radiological engineering at the University of Florida, Gainesville.

Bolch and colleagues discovered that children have a greater percentage of total mineral bone in direct contact with sensitive bone marrow than do adults. This has implications for radiation treatments and types of chemotherapy used to treat cancer patients, especially therapies targeting pediatric bone cancers.

In contrast to existing models, the study also found that a large amount of the electron and beta particle energy once believed to stay contained within the bone marrow of children actually escapes to surrounding tissue, said Deanna Pafundi, PhD, a University of Florida researcher and lead author of the paper, who is now a research fellow at the Mayo Clinic in Rochester, Minn. This finding is being used in existing University of Florida research calculating the impact of radiation to the skeletal surrounding tissues, she said.

The University of Florida 's newborn skeletal model suggests that radiation doses to newborn bone marrow have been overestimated by existing clinical skeletal models and seeks to replace these estimates by using three-dimensional imaging and extending the work to the pediatric and prenatal skeleton.

"The current philosophy is that there is a small but perceptible risk of cancer with every radiation exposure. Consequently, you want to maximize the dose delivered to the tumor in radiation therapy, while minimizing the dose and thus additional cancer risk to surrounding healthy tissues," Bolch said.

Children are at particular risk from radiation exposure, Bolch said, as the carcinogenic effects of radiation have more time to develop in children than in adults. In response to these concerns, professionals involved in pediatric imaging have launched a campaign, dubbed Image Gently, to highlight opportunities to lower radiation dosing when imaging children, he added.