Gamma and neutron imaging take a step toward the clinic

 - gamma and neutron imaging at Duke
Simulated 3D dose measurements of the breast show the radiation dose imparted to the whole body. Dose is shown on a red and yellow color map, where yellow represents maximum dose.
Source: Duke Medicine

Researchers have been both intrigued by the potential of gamma and neutron imaging for the early detection of cancer but concerned by the potential radiation dose involved. New research suggests that the safety profile of gamma imaging and neutron imaging may be on par with that of conventional imaging techniques that use ionizing radiation, according to a paper in the June issue of Medical Physics.

Anuj Kapadia, Ph.D., assistant professor of radiology at Duke University School of Medicine and the study’s senior author, and a team of researchers at Duke Medicine have built prototypes of the imaging methods to investigate the ability of neutron-stimulated emission computed tomography (NSECT) and gamma-stimulated emission computed tomography (GSECT) to detect lesions before they are large enough to be detected by conventional medical imaging techniques.

Unlike transmission imaging techniques such as CT, both NSECT and GSECT are emission methods that image the spectroscopic distribution of naturally occurring elements in the body, negating the need for a biopsy or injection of contrast media. Many tumors have been found to have higher concentrations of trace-level elements that occur naturally in the body—such as aluminum and rubidium—at the earliest stages of tumor growth.

Neutrons scatter considerably upon entering the body, potentially putting vital organs at risk of exposure, so early research in this field has focused on how much radiation is absorbed in the targeted organ versus surrounding tissue.

Using Monte Carlo computer simulations, the researchers estimated the radiation dose delivered to the male and female liver and the female breast, finding that most of the radiation was delivered to organs directly within the radiation beam, and a much lower dose was absorbed by tissue outside of the radiation beam.

The findings were most positive in the breast, where dose to the breast accounted for 96% of the neutron scan radiation and 99% of the gamma scan radiation; the heart and lungs received less than 1%.

In the liver, the neutron scan delivered the highest dose to the liver while the gamma scan delivered the greatest dose to the stomach, indicating more work needs be done to better target liver scans.

“Radiation dose to proximal organs was considerably lower than originally perceived,” Kapadia told RadiologyBusiness.com. “These results show us how to customize the neutron and gamma scans to improve their safety profile. We can now tailor the imaging setup to scan only the organ of interest while avoiding unnecessary irradiation of proximal organs. The results will guide the development of our future clinical scanners.”

Kapadia and team are already imaging animal tissue specimens and surgically excised human cancers. “My focus is to build a compact clinical device that could be wheeled into a hospital,” Kapadia said. “We are actively looking for funding to build this device now.”