Hi ♫
This question have nothing to do with psychology, since this therapy is used for treat cancers, tumours, ocular melanomas... Anyway you will have some explanations from this website : http://linkinghub.elsevier.com/retrieve/pii/S1278-3218(10)00010-7
I'm sorry, the website seems to have changed ! It can't help you so....
Have a nice day
Catherine