Resonance-guided vaporization may give better approaches for treating tumors

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• Source: University of Twente


• Date: 04 Feb,2021

Sending tiny droplets to a tumor and having them vaporized using focused ultrasound: it might be a new way of tracing a tumor or send drugs locally.

Researchers of the University of Twente in The Netherlands now demonstrate a new phenomenon triggering droplet vaporization: it occurs at the exact acoustic resonance frequency and causes fast and efficient lowering of the pressure in the droplet, until under the threshold value for vaporization. The findings are in Physical Review Letters.

Micro droplets, stabilized with a thin shell, can be visualized from the blood stream using ultrasound. There is a growing number of medical applications, in imaging and treatment. The droplets, however, are too large to invade a tumor.

By guiding them into the tumor and using them vaporize’on the spot’, the bubbles that are formed may have a therapeutic effect within the tumor. Vaporization may typically look a physical phenomenon of which everything is known already, but the UT researchers demonstrate a new mechanism.

It is based on resonance, just like in the event a crystal glass breaks caused by the noise of that specific singing note. It’s at the resonance frequency that vaporization can be guided and amplified. The research was done using droplets of hydrofluorocarbons (HFCs), with a low boiling point.

In practice, vaporization is tough to control, as nucleation points are required: these are the causes for vaporization. The extreme lowering of pressure happening at resonance – six times lower than in the surrounding fluid – triggers a radically higher vaporization probability. The resonance effect is due to the difference in the speed of sound: inside the fluorocarbon, it’s much lower than in the water or tissue surrounding it.

By sending an acoustic wave into the droplets, the researchers demonstrate how vaporization is triggered. This highly controlled vaporization may introduce new ways of treating tumors. Imagine switching on the vaporization, the minute the droplet has invaded the tumor: this may damage the tumor caused by the violent way vaporization occurs.

In addition, it can be a used for delivering drugs in the tumor locally and exclusively, without unwanted effects in the rest of the body.

The new insight into resonance-guided vaporization can, except for medical applications, be significant in energy storage or combustion processes.