Shock waves burst kidney stones & create thunder
Shock waves are the source of a number of everyday phenomena, such as the rumble of thunder and supersonic bangs. In medicine these waves have come to use for crushing renal calculi, or stones in the kidneys. Doctoral student Veronica Eliasson at KTH has examined the process occurring if such waves are focussed. Her findings have met with international acclaim, earning her a post as researcher at the renowned California Institute of Technology.
A shock wave could be described as a narrow space having its local values of temperature, pressure and speed in front of the impact suddenly ”jump” to other values behind that impact. This generates forces that may be utilised by Man. Veronica Eliasson has just defended her doctoral dissertation concerning research on these shock waves.
– Actually, phenomena consisting of just these shock waves are something we encounter every day, says the new KTH Doctor of Technology. An example of this is the rumble of thunder! This is caused by a shock wave, which is generated by the rise in temperature coming from the flash of lightning. Its energy is then transformed into sound.
The target of her project has been to understand how shock waves behave as they are focussed. It has been known for a long time that a circular shock wave is unstable, i e the same kind of experiment leads to different results each time it is repeated. Dr Eliasson continues:
– We found that triangular or octagonal shock waves are stable; these focus in a predictable manner each time they are created. Now we have learned more about different kinds of waves, and how different obstacles may affect their shape in the course of the focussing process.
This knowledge may come in very handy in for instance "Shock Wave Lithotripsy" (SWL), which is a kind of treatment against renal calculi – thousands of shock waves are sent into the human body and focussed against the kidney stone. This makes the stone burst into a lot of little grains not larger than a grain of sand.
– The body itself could then neutralize these, explains Veronica Eliasson. Our findings may well help to improve this whole technology a lot.
Magnus Myrén