For decades, ultrasound has been associated with diagnostics – a routine scan in a hospital room, a monitor displaying organs, tissues, or the first image of a baby. However, researchers are now looking at ultrasound from an entirely different perspective. New findings from scientists at Kaunas University of Technology (KTU) suggest that ultrasound waves might not only help doctors see inside the body, but low-frequency ultrasound directly influences blood flow – potentially opening new possibilities to support the treatment of cardiovascular diseases, Alzheimer's disease, and diabetes, reducing the need for invasive procedures or medication in the future.
What surprised the researchers most was that ultrasound did not affect blood in just one way. Their study showed that different sound frequencies can produce opposite effects on red blood cells: they can either encourage the cells to cluster together or separate them into single cells.
Non-Invasive Way to Improve Oxygen Exchange
Red blood cells, also called erythrocytes, naturally tend to form reversible clusters known as aggregates. This process affects blood viscosity – a property closely linked to circulation and oxygen transport throughout the body.
"When erythrocytes cluster together under the influence of high-frequency ultrasound, blood viscosity increases, blood pressure and pulse may rise, and oxygen exchange becomes less efficient," explains KTU professor Vytautas Ostaševičius, lead author of the study.
The researchers found that high-frequency ultrasound creates standing acoustic waves that drive erythrocytes toward low-pressure regions, promoting aggregation. Low-frequency ultrasound, however, generates travelling acoustic waves that create shear forces capable of separating aggregated erythrocytes into single cells.
The experiments demonstrated that low-frequency ultrasound can dissociate erythrocyte aggregates into single cells. "To our knowledge, this effect has not previously been demonstrated," says Ostaševičius, director of the KTU Institute of Mechatronics .
When erythrocytes separate, gaps appear between them, which decrease blood viscosity, and the entire surface of the cell can participate in oxygen exchange.
The idea for the research emerged during the COVID-19 pandemic, when scientists searched for non-invasive ways to support patients experiencing severe respiratory complications.
"At the time, there was an urgent need for therapies that could help patients quickly and without medication. We became interested in whether ultrasound could intensify the interaction between haemoglobin and oxygen in the lungs," says Ostaševičius.
To investigate this, the team divided the patients' blood into several hundred samples, which were exposed to ultrasound of varying intensities and revealed the peculiarities of erythrocyte dissociation. While studying ultrasound propagation in biological tissues, the team used digital twins to develop a low-frequency ultrasound transducer capable of sending acoustic signals approximately four times deeper into biological tissues than conventional devices. This technology is now protected by an international patent.
Potential Applications in Alzheimer's Disease and Diabetes Treatment
Although the technology remains at an early research stage, the researchers believe low-frequency ultrasound could eventually be applied in several medical fields where blood circulation and oxygen delivery play an important role.
One of the areas being explored is cancer therapy. Since tumour tissue is often mechanically weaker than surrounding healthy tissue, travelling acoustic waves are being explored as a way that may help selectively affect tumour structures. However, this concept is still at an early research stage.
"Low oxygen levels in tumours remain one of the major challenges in cancer therapy. If oxygen delivery to tissues can be improved locally, it may help increase the effectiveness of certain treatments," says Ostaševičius.
The researchers also see potential in Alzheimer's disease therapy, where the approach is being discussed as a potential future way to temporarily open the blood-brain barrier and, in future, improve targeted drug delivery to brain tissue.
According to Prof. Ostaševičius, the technology could also support the treatment of diabetic foot ulcers, where impaired circulation makes wound healing significantly more difficult. "Using ultrasound, it may be possible to improve blood flow in affected tissues," he says.
Additional future applications may include targeted drug delivery and supportive therapies for cardiovascular and pulmonary diseases.
Although the technology is still experimental, the researchers believe their findings broaden the understanding of ultrasound as more than a diagnostic tool. "Our work shows that ultrasound can mechanically influence blood properties. This opens possibilities for future non-invasive therapies that may one day complement existing medication-based and surgical treatments," says Ostaševičius.
The article "Advances in Ultrasonic Rehabilitation" can be accessed here .
