Shock wave clue to improving radiotherapy

Beams of ions – positively charged particles – have been used in radiation treatments for cancer for almost 30 years. And while radiotherapy is recognised as a robust therapy for tackling tumours, no one quite knows what happens when the ions actually enter the target area.

Now, modelling work by Eugene Surdutovich from Oakland University, US, and colleagues has brought understanding one step closer, with findings suggesting that better mapping of the way the ions impact cells will lead to more accurate applications, potentially saving lives.

Surdutovich’s team constructed a model of what happens when an energetic ion enters a droplet of liquid. In a manner broadly similar to an arrow hitting an apple, or a dart passing through an inflated balloon, the ion transfers energy to the droplet, creating a shockwave.

This wave has a powerful effect on the thermomechanical damage the ion inflicts, by propagating particles such as free radicals across a wider area. In effect, if the entering ion smashes into a droplet with an initial radius of between 30 and 1000 nanometres, the result will be multiple smaller droplets.

This means that the number of tumour cells affected by the ion is increased. Understanding how these shock waves behave may lead to more finely tuned approaches to the use of radiation in cancer therapy.

The research is published in The European Physics Journal D.

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