A cardiac clinic wants a positron-emitting tracer that can be re-injected roughly…
PHYSICS · Multi-part · Fermi University Physics · Nuclear Physics · Biophysics & Medical Physics · Radioactivity and decay modes
The Nucleus Resolved, Ch What it is used for: medicine, dating and analysis
Problem
A cardiac clinic wants a positron-emitting tracer that can be re-injected roughly every ten minutes for repeated rest and stress scans, supplied from an on-site generator with no cyclotron on the premises. The candidate is 82Rb (positron emitter, half-life 76s), milked from a 82Sr parent (half-life 25.5d) reset to zero daughter activity at each elution.
((a)) Using the two-member decay-chain formula for the time at which the daughter activity is greatest, find how long after an elution the 82Rb activity peaks, and use the result to say whether the generator can effectively supply the tracer on demand every ten minutes.
((b)) Later, the same laboratory's cyclotron cooling water is checked by accelerator mass spectrometry for trace tritium (3H, half-life 12.3yr, a β− emitter). Given that tritium decays to a stable isobar of the same mass number, name that isobar, and explain how the negative-ion source stage of accelerator mass spectrometry can suppress it while still transmitting 3H ions, given that this isobar does not form a stable negative ion.