Nuclear Medicine Physics Module PDF

Nuclear Medicine Physics Module Dr Mohammed Saeed Alqahtani Lecture 1: Introduction Welcome Back ☺ 2 Our agreement I wish all students arrived on time, and for those who came late.. PLEASE find your place with minimal disturbance for your fellow students. Do ask questions at anytime.. during the lec...

Nuclear Medicine Physics Module Dr Mohammed Saeed Alqahtani Lecture 1: Introduction Welcome Back ☺ 2 Our agreement I wish all students arrived on time, and for those who came late.. PLEASE find your place with minimal disturbance for your fellow students. Do ask questions at anytime.. during the lectures or the practical sessions Give yourself enough time to read and understand your notes, and let’s discuss any potential problem that you may face ASAP 3 Introduction ▪ The technologies used in nuclear medicine for diagnostic imaging have improved over the last century, starting with Röntgen’s discovery of X rays and Becquerel’s discovery of natural radioactivity. ▪ Each decade has brought innovation in the form of new equipment, techniques, radiopharmaceuticals, advances in radionuclide production and, ultimately, better patient care. ▪ All such technologies have been developed and can only be practised safely with a clear understanding of the behaviour and principles of radiation sources and radiation detection. 4 Radioactivity 5 Stable nuclei ▪ Nearly, all the nuclides extant in the world are stable. ▪Apart from the nucleus of ordinary hydrogen, which consists of a single proton, all the stable lighter nuclei contain nearly equal numbers of protons and neutrons. →For example: Helium atom 6 Isotopes ▪ Isotopes of an element are nuclides that have the same number of protons (atomic number), position in the periodic table, and chemical and metabolic properties, but a different number of neutrons, mass number (protons + neutrons), density and other physical properties. 7 Isotopes For example: (Carbon-12) → stable → 6 neutrons + 6 protons 14C (Carbon-14) → unstable → 8 neutrons + 6 protons (a neutron excess) 11C (Carbon-11) → unstable → 5 neutrons + 6 protons (a neutron deficit) 12C ▪ Both 14C and 11C are artificially produced, unstable and radioactive. 8 Radionuclides ▪ Unstable nuclei are radioactive and decay until they become stable nuclei with the emission of any combination of alpha, beta and gamma radiation. ▪ Naturally occurring radionuclides, such as uranium, radon and radium, contribute to our background radiation exposure, whether external to the body or internal. 9 Production of radionuclides ▪ There are more than 2700 known radionuclides. ▪ Radionuclides used in medical imaging are produced artificially, in the following ways: 10 Production of radionuclides A) If an additional neutron is forced into a stable nucleus → a neutron excess ▪ This process occurs in a nuclear reactor. For example, with Molybdenum: 98Mo +n→ 99Mo ▪ The atomic number of the nucleus remains unchanged, but its mass has been increased by one. 11 Production of radionuclides B) If an additional proton is forced into a stable nucleus, knocking out a neutron → a neutron deficit ▪ This process occurs in a cyclotron, which accelerates positively charged ions (protons, deuterons or alpha particles) on the target material. For example, with oxygen: 18O +p→ 18F +n ▪ The mass number has not been changed, but its atomic number has increased by one to become fluorine. 12 Production of radionuclides ▪ Radionuclides produced in a cyclotron are short-lived (i.e. with half-lives ranging from less than a minute to a couple of hours). → So, it is only possible to use them reasonably close to the cyclotron. ▪ Medical minicyclotrons have been designed specially for the production of short-lived radionuclides such as fluorine-18 (18F) at or near the hospital site. 13 Production of radionuclides Cyclotron 14 15