How long until we run out of helium?

Could you elaborate on the current state of helium supply and its potential depletion? Given the widespread applications of helium in areas such as medical imaging, cryogenics, and welding, how long do experts estimate we have before the resource becomes scarce? Are there any viable alternatives to helium in its various applications, or are we facing a potential shortage that could significantly impact industries and research? Additionally, what measures are being taken to ensure a sustainable supply of helium for the future?