RADIONUCLIDE.pptx for the radiology residents doing MD in radiology

helpful for radiology PG .Radionucleide

1. RADIONUCLIDE SAMEEKSHA SHETTY 2 nd MSC MIT

2. INTRODUCTION: Radionuclide is an atom that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: Emitted from the nucleus a gamma radiation Transferred to one of its electrons to release it as a conversion electron To create and emit a new particles from the nucleus .

3. Nuclear medicine is a medical specialty involving the application of radioactive substances in the diagnosis and treatment of disease.  Radionuclides are combined with other elements to form chemical compounds, or else combined with existing pharmaceuticals compounds, to form radiopharmaceuticals.

4. Most of the naturally occurring radionuclides are long lived. The radionuclides used in modern nuclear medicine all are of the manufactured or artificial variety. They are made by bombarding nuclei of stable atoms with subnuclear particles so as to cause nuclear reactions that convert a stable nucleus to an unstable one .

5. PRODUCTION OF RADIONUCLIDE

6. METHODS OF PRODUCTION Reactor produced radionuclides Accelerator produced radionuclides Radionuclide generator

7. Reactor produced radionuclides

8. 1. REACTOR PRINCIPLE: The CORE of a nuclear reactor contains a quantity of fissionable material typically natural uranium 235 U and 238 U. Uranium 235 undergoes spontaneous nuclear fission , splitting into two lighter nuclear fragments and emitting into two or three fission neutrons .

9. 235 U+n = 236 U The 236 U nucleus is highly unstable and undergoes nuclear fission Releasing additional fission neutrons

10. Instead of this uncontrolled reaction, in nuclear reactor establishes a controlled nuclear reaction.

11. Fuel cells- containing fissionable material are surrounded by a moderate material. Moderator- to slow down the rather energetic fission materials Moderator- heavy water, D 2 0 (containing deuterium and graphite. Control rods- to either expose or shield the fuel cells from one another- strong neutron absorbers, donot undergo nuclear fission.(CADMIUM OR BORON)

12. The fuel cells and the control rods are positioned for a controlled chain reaction. Incorrect positioning leads a runaway reaction and to a possible melt down of the reactor core. Insertion of additional control rods results in excess absorption of neutrons and terminates the chain reaction , usually done to shut down the reactor.

13. Each nuclear event results in release of substantial amount of energy, as thermal energy. This energy can be used as thermal power source in reactors.

14. FISSION FRAGMENTS Used to produce useful quantities of medically important radionuclides such as 99 Mo Fission products always have an excess of neutrons, because N/Z is higher for 235 U . Fission products may be carrier free (no stable isotope of the element of interests produced).

15. NEUTRON ACTIVATION Neutron carry no net charge ,neither attracted nor repelled by atomic nuclei. When neutrons strike a target, some of the neutrons are captured by nuclei of the target atom. Target nucleus may be converted into a radioactive product . Such an event is called NEUTRON ACTIVATION.

16. Neutrons produced by the fission of uranium in a nuclear reactor can be used to create radionuclides by bombarding stable target material placed in the reactor Process involves capture of neutrons by stable nuclei Almost all radionuclides produced by neutron activation decay by beta-minus particle emission

17. ACCELERATOR - PRODUCED RADIONUCLIDES

18. CYCLOTRONS

19. 2. Cyclotrons Cyclotrons produce radionuclides by bombarding stable nuclei with high-energy charged proton particles. Consists of a pair of hollow semicircular metal electrodes – DEES Positioned b/n the poles of a large electromagnet Dees are separated from one another by a narrow gap, center of the dees is an ion source ‘S’- used to generate the charged particles. All these are in a vacuum tank at 10 -3 Pascals

20. The particles are accelerated across the gap gaining about 30kev of energy They continue a circular path within the opposite dee . Each time particles across the gap gain energy Orbital radius continuously increase and the particles follow an spiraling path. When the particle has no more space to grow in radius, it comes out of the cyclotron through the opening and strike the target.

21. 1.5 tesla 10 -3 pascals .

22. DEES TARGET

23. The energy of the particle accelerated in a cyclotron can be calculated by: E( Mev )= 4.8×10 -3 (H×R×Z) 2 /A Where H -magnetic field strength in T R - radius of particle orbit in cm Z – atomic no of the accelerated particle A - mass no of the accelerated particle

24. Specialized hospital-based cyclotrons have been developed to produce positron-emitting radionuclides for positron emission tomography (PET) Usually located near the PET imager because of short half-lives of the radionuclides produced

25. GENERATOR - PRODUCED RADIONUCLIDES

26. 3.RADIONUCLIDE GENERATORS A system for holding the parent in such a way that the daughter can be easily separated for clinical use is called a radionuclide generator Consists of a parent daughter radionuclide pair contained in a container Permits separation and extraction of the daughter from the parent. Technetium-99m has been the most important radionuclide used in nuclear medicine.

27. CHARACTERISTICS Technetium-99m emits γ rays, favorable for use with a gamma camera. Reasonable half life-6hrs Low radiation dose per emitted γ ray Can be used to label a wide variety of imaging agents.

28. The parent 99 Mo in the form of molybdate ion MoO 2- is bound to an alumina column The daughter 99m Tco 4 (pertechnetate) is not as strongly bound to alumina This can be eluted from the column with 5 to 25ml of normal saline. 75% to 85% of the available 99m Tc activity is extracted in a single elution. 4

29. Thank you