Common beer ingredient could boost the impact of imaging

A rich nutrient source, barley is often found in a variety of foodstuffs, from soups and stews to cereals and malt beverages. But a new and unexpected use for the popular beer ingredient has recently come to light, with promising utility in diagnostic imaging.

According to the researchers of a recent study published in Biomaterials, roasted barley performs well as a conventional contrast agent and may aid with photoacoustic computed tomography (PACT) of the swallowing and gut processes, which could lead to improved diagnosis of gastrointestinal (GI) tract and swallowing disorders.

More than 15 million Americans are affected by swallowing disorders, or dysphagia, which can be caused by everything from nerve and muscle problems to more serious medical conditions like Alzheimer’s disease and cancer.

Diagnosis of dysphagia often includes physical examination coupled with diagnostic testing and x-rays, traditionally with the use of barium—the thick, chalky liquid used as a contrast agent. Once the patient has either consumed or been injected with barium, the examining clinician will use x-rays, MRIs, or ultrasounds to examine the inside of the patient’s throat. However, each of these modalities have their drawbacks: MRIs are expensive, x-rays result in radiation exposure and are not satisfactory for long-term imaging, and ultrasounds can have trouble differentiating a small amount of swallowed materials from surrounding tissues.

PACT is an emerging alternative imaging tool that is low cost, non-radiative, and sensitive to optical absorption contrast. It integrates acoustic detection and optical excitation, and provides multiscale imaging with either endogenous or exogenous contrasts. The most common endogenous agent is hemoglobin, which provides anatomic, functional, and metabolic data about blood vessels.

Various exogenous agents are capable of enhancing imaging contrast, such as metallic nanoparticles, carbon nanotubes, tetrapyrrole nanoparticles, dyes, and proteins. Unlike endogenous agents, exogenous agents can be designed to enhance photoacoustic detection sensitivity and uncover functional and molecular data, including intestinal motility, glucose uptake, and calcium activity.

However promising, exogenous agents do face challenges. “Unfortunately, with the exception of dyes such as indocyanine green, which are already approved for human use by health regulatory agencies, the majority of these novel contrast agents will not be tested in humans until passing through a lengthy and expensive regulatory process,” wrote the University of Buffalo researchers.

A readily available and safe exogenous contrast that isn’t regulated would provide an immediate way to boost PACT’s clinical impact.

“That’s what led us to search for edible alternatives. Because we’ve been eating or drinking these products, we know they’re safe for most people,” said senior author Jonathan Lovell, PhD, associate professor, Department of Biomedical Engineering, University at Buffalo, State University of New York, Buffalo, NY.

In their search, Dr. Lovell and colleagues tested 200 types of tea, chocolate, herbs, and other foodstuffs for photoacoustic contrast using 1,064 nm pulse laser excitation. After identifying roasted barley as a potentially promising agent, they further screened 20 brands in search of the one with the highest contrast capability. The researchers suggest that roasted barley works because of complex chemical processes that take place during the roasting process.

The investigators found that individual roasted barley particles could be detected through chicken breast tissue that was 3.5 cm thick, as well as through the hands of human volunteers. Moreover, unlike with ultrasound, a single grain of roasted barley could be detected amongst a field of hundreds of particles that were not roasted.

Upon ingestion, roasted barley allowed for PACT visualization of the gut and peristalsis in mouse models, and when given to humans in the form of barley tea—in a manner similar to the traditional barium drink—photoacoustic imaging was capable of visualizing swallowing dynamics.

“Besides human swallowing imaging, roasted barley may potentially be used for clinical imaging to diagnose GI motility disorders such as esophageal achalasia, esophageal spasm, and esophageal reflux, as well as gastric motility disorders. Taken together, research of using roasted barley or other foods as contrast agents should open new avenues for PACT biomedical applications,” concluded Dr. Lovell and coauthors.