There are a few aspects to your question. The most direct answer to you is that it's not going to depend on isotopes and it's not going to depend on technology; it's going to depend on people and on when people will quit on us, on when the technologists will say that they've had enough of this nonsense and cannot cope any longer.
As I said, we have seen a decrease in enrolment of students and a decrease of physicians in nuclear science, so the effect in the short term is going to be essentially in the middle term and long term. I don't have a crystal ball; I do not know, but what I know for a fact is that's the way I feel and that's the way it is.
Over the past six months we went back in time. We now practise nuclear medicine the way I was practising it in the 1980s. We went from a 21st century type of service to a 20th century type of service.
Thallium is a good isotope. Actually, physiologically it's still the best, although not the ideal isotope. Radiation is definitely increased. We can use it, but not necessarily for the next few years.