Device Sees Bacteria Behind the Eardrum

Photo: Non-invasive middle ear imaging

The device could usher in a new suite of non-invasive, 3-D diagnostic imaging tools for primary-care physicians.

Ear infections are the most common conditions that pediatricians treat. Chronic ear infections can damage hearing and often require surgery to place drainage tubes in the eardrum, and problems can persist into adulthood.

Studies have found that patients who suffer from chronic ear infections may have a film of bacteria or other microorganisms that builds up behind the eardrum, very similar to dental plaque on unbrushed teeth. Finding and monitoring these so-called biofilms are important for successfully identifying and treating chronic ear infections.

"We know that antibiotics do not always work well if you have a biofilm, because the bacteria protect themselves and become resistant," Boppart said. "In the presence of a chronic ear infection that has a biofilm, the bacteria may not respond to the usual antibiotics, and you need to stop them. But without being able to detect the biofilm, we have no idea whether or not it's responding to treatment."

However, middle-ear biofilms are difficult to diagnose. A doctor looking through a standard otoscope sees only the eardrum's surface, not the bacteria-seeded biofilm lurking behind it waiting to bloom into infection. Invasive tests can provide evidence of a biofilm, but are unpleasant for the patient and cannot be used routinely.

The new device is an application of a technique called optical coherence tomography (OCT), a non-invasive imaging system devised by Boppart's group. It uses beams of light to collect high-resolution, three-dimensional tissue images, scanning through the eardrum to the biofilm behind it – much like ultrasound imaging, but using light.

"We send the light into the ear canal, and it scatters and reflects from the tympanic membrane and the biofilm behind it," said graduate student Cac Nguyen, the lead author of the paper. "We measure the reflection, and with the reference light we can get the structure in depth."

The single scan is performed in a fraction of a second – speed is a necessity for treating squirming tots – and images a few millimeters deep behind the eardrum. Thus, doctors can see not only the presence of a biofilm, but also how thick it is and its position against the eardrum.

COMPAMED.de; Source: University of Illinois at Urbana-Champaign