Lesson 16 Nuclear Medicine

What is Nuclear Medicine? Diagnosis and Treatment of Disease using small amounts of radio-nuclides (radiopharmaceuticals) In diagnosis (imaging) emitted radiation is detected by special detectors (cameras) from injected radio-nuclides to give real time 3 D images of the body. In treatment, radio-nuclides are injected into the body, concentrated in the organ of choice and damage the tissue.

Importance of Nuclear Medicine to students Combines nuclear and radiochemistry, pharmacy, medicine, and radiation biology. Nuclear medicine is a major employer of today’s nuclear and radiochemists, with an ever increasing demand for trained people. Six figure starting salaries

Special properties of 99 Tc m keV gamma ray just perfect for imaging 6 hour t 1/2 minimizes radiation dose yet is tractable for hospital procedures 10 million procedures per year in the US

The 99 Mo-> 99 Tc decay is an example of transient equilibrium

Milking

Production of 99 Mo

Details and Problems Currently AECL/MDS Nordion supply 40% of the world’s demand for 99 Mo/ 99 Tc. Chemistry is performed on the irradiated targets by AECL resulting in a 99Mo soln. The soln is shipped to MDS Nordion where it is loaded on the column and distributed. The US demand requires about 34,000-46,000 Ci are produced per week.

What is the Crisis? These old reactors are nearing the end of their lifetime and their operation is not reliable. Recently the Canadian and Dutch reactors underwent prolonged shutdowns US use of 99 Mo was curtailed and rationed. President Obama gave orders to Steven Chu (Sec. of Energy) to “solve the problem.”

Special Problems for the US We have no domestic supply of 99 Mo. US production was stopped in (It was claimed that non-US suppliers were subsidized and we could not compete.) High cost production facilities, risk of reactor operations, low market price The best techniques involve the use of HEU (19.7 % 235 U) which poses a national security problem. The waste from the production is significant.

Positron Emission Tomography (PET) PET imaging provides quantitative information about biochemical and physiological processes, in vivo A tracer containing a positron emitter is injected, it decays emitting positrons and one detects the two MeV photons resulting from the annihilation of the positron-electron interaction.

Special things you can do with PET Real time imaging of brain functions. Effect of drugs, Alzheimer’s disease, psychiatry. 90% of use in oncology Pharmacology

Therapy Oldest aspect of nuclear medicine Idea is to use radiation to kill unhealthy cells Problem is to do this without killing all the healthy cells. A problem is that cancer cells are less oxygenated than normal cells and are more radiation resistant. One trick is physical location, ie, fix the radionuclide in a cancer cell so that the decay will preferentially damage the cancer cell.

Tricks BNCT (Boron neutron cancer therapy) Attach boron compounds to tumor locations. Boron has a very high thermal neutron capture cross section n+ 10 B-> 11 B-> 7 Li + 4 He Re-oxygenation

Bragg Curve Dosimetry

Thanks to