A new technique measures the frequency of sounds emitted by biological structures

Did you know that music and diagnostic imaging have something in common? The sounds have a lower or higher pitch depending on the size of the object that creates them. Tuba and bbad are voluminous and produce serious bbad sounds, while flutes and violins are small and produce high-pitched sounds. Interestingly, the same effect occurs when biological structures such as cells or tissues emit sound – height varies with size.

But what types of sounds do biological structures produce? Moreover, how can we listen to them?

Leveraging the correlation between height and height, a research team led by Ryerson at the Institute of Biomedical Engineering, Science and Technology (iBEST) at St. Michael's Hospital recently developed an imaging mode so innovative that the results of their studies were published in the journal Nature, Physics of communication.

The badessment of this advance begins with the basics of photoacoustic imaging (PA), a modality that is rapidly gaining popularity in biomedical research. Like its Ultrasound cousin (US), PA imaging creates a visual image of biological structures by collecting sound waves.

While American imaging technology involves sending sound waves into a biological structure and listening to echoes as they bounce, PA imaging technology does something completely different.

"With photoacoustic imaging, we project light into structures that will absorb it, such as blood vessels," says Dr. Michael Kolios, a pioneer of sound imaging who has overseen the # 39; study. "The light waves heat the biological structures of a tiny fraction, which triggers an almost imperceptible volume expansion.When this happens, a sound is generated, like thunder after a thunderbolt."

Most existing PA imaging techniques measure loudness, displaying areas that emit louder sounds with brighter pixels. The Ryerson-led team developed a technique to measure the frequency (pitch) of sounds emitted by biological structures.

"Depending on the size of a biological structure, the height of the sound waves emitted will be more or less important," says Dr. Michael Moore, resident in Medical Physics at the Grand River Hospital in Kitchener, which has directed the research team as a PhD student. under the supervision of Kolios. "If we could filter inbound sounds by frequency, we could create images that focus on structures of a particular size, which would help reveal features that might otherwise be hidden or less obvious."

The team developed a technique they call F mode (for frequency), which allowed them to split PA signals into different frequency bands. They then successfully demonstrated the selective enhancement of characteristics of different sizes in samples ranging from biological cells to live zebrafish larvae, all without the use of contrast dyes that would generally be required by other techniques. advanced imaging.

Moore and Kolios quickly pointed out that one of the keys to their success was the opportunity to work for iBEST and with Dr. Xiao-Yan Wen and his team at the zebrafish Drug Research Center. "Without the knowledge and expertise of the Wen Lab team, it would not have been possible to demonstrate that our technique worked," Moore says.

The research team, which includes Ryerson PhD candidates in biomedical physics, Eno Hysi and Muhannad Fadhel, is taking steps to turn F mode into clinical applications, where it will be largely beneficial. For example, the ability to segment and enhance features of different scales has significant potential in areas such as ophthalmology, neurosurgery and the detection of various conditions such as hypertension.