<prompt> Radiation exposure is the least in the following procedureMicturating cystourethrogramIVPBilateral nephrostomogramSpiral CT for stones  <response>: Amongst the given options micturating cystourethrogram has least radiation exposure with number of chest x-ray equivalent of 60.IVP has chest x-ray equivalent 120, nephrostomogram has x-ray eqiuvalent 170, and CT Plevis has x-ray equivalent 500. 