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In response to the shortage of helium for his research, Ray Dolan, a professor at University College London's Wellcome Trust Centre for Neuroimaging, suggests that in the long run it might be possible to synthesise the gas at much greater cost ("Helium shortage not a gas as labs postpone 'optimal' work on grey matter", 19 January).

Chemical synthesis would require a (cheap) helium compound as a starting material but, rather unfortunately, helium, being a noble gas, forms no stable (or cheap) compounds: in fact, it is arguable whether it can form compounds at all.

This only leaves transmutation of some other element to helium: this occurs in the Sun (from hydrogen). Our attempts to generate energy by nuclear fusion are currently only at an early stage, so this route - on Earth, at least - seems unlikely. I suppose there's always alchemy. (Once a chemist, always a chemist...)

Peter B. Baker, London