Development and application of a focused ultrasoft X-ray probe for radiobiological applications
Folkard M., Schettino G., Vojnovic B., Michette AG., David C., Pfauntsch SJ., Prise KM., Michael BD.
Cellular micro-irradiation is now seen as a potent method for understanding how radiations interact with living cells and tissues. The strength of this technique lies in its ability to deliver precise doses of radiation to selected individual cells in vitro, or to pre-selected targets within cells. We have recently developed a focused soft X-ray microprobe for targeting individual cells. The use of focused X-rays for this type of study is unique, and is being applied in a number of novel experiments. One important application is to study the so-called 'bystander effect' where un-irradiated cells are seen to respond to signals from nearby irradiated cells. It is also being used as a sub-cellular probe to compare the effects of nuclear versus cytoplasmic targeting. Our facility uses a 0.4-0.8 mm diameter zone plate to focus soft X-rays to a sub-micron beam. This is then aimed at selected sub-cellular targets using rapid automated cell finding and alignment procedures. The zone plate images characteristic-K X-rays of carbon or aluminium, generated by focusing a beam of 5-10 keV electrons on to the appropriate target. The current arrangement will deliver about 10000 photons/sec to the focus (sufficient to irradiate several tens of cells per minute).