radiopharmaceuticals.pptxFHRGLSAG/HHEIDHHRFG

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1. Radiopharmaceuticals

2. Radiopharmaceutical refers to any medicinal or pharmaceutical product, which when ready for use contains one or more radionuclides (radioactive isotopes) intended for human use either for diagnosis or therapy Nuclide is an elemental species characterized by its mass number ‘A’, (the sum of the number of protons and neutrons in its nucleus), its atomic number ‘Z’ (number of protons which is also same as number of electrons in a neutral atom) Isotopes of an element are nuclides with the same atomic number ‘Z’ but different mass numbers ‘A’. They occupy the same place in the periodic table and have similar chemical properties

3. Radionuclide: Nuclides containing an unstable arrangement of protons and neutrons that transform spontaneously to either a stable or another unstable combination of protons and neutrons with a constant statistical probability by emission of radiation These are said to be radioactive and are called radionuclides . The initial unstable nuclide is referred to as the ‘parent radionuclide’ and the nuclide after transformation as the ‘daughter nuclide’. Such a transformation is also known as ‘Radioactive transmutation’ or ‘radioactive disintegration’ or ‘radioactive decay’

4. The phenomenon of emission of radiation owing to the spontaneous transformation or disintegration of the radionuclide is known as ‘Radioactivity’. It is also used to express the physical quantity (activity or strength) of this phenomenon In the International System (SI), the unit of radioactivity is one nuclear transmutation per second and is expressed in Becquerel ( Bq ), named after the scientist Henri Bequerel . The old unit of radioactivity was Curie ( Ci ), named after the scientists Madame Marie Curie and Pierre Curie, the pioneers who studied the phenomenon of radioactivity.

5. Half-Life Period: The time in which a given quantity of a radionuclide decays to half its initial value is termed as half-life (T1/2) Radionuclidic purity: The ratio, expressed as a percentage, of the radioactivity of the radionuclide of interest to the total radioactivity of the radioactive preparation is referred to as the ‘ Radionuclidic Purity’ is an important quality parameter and it is mandatory that the radionuclidic impurities to be within the stipulated limits radionuclidic impurities, arise during the radionuclide production, dependent on the production method

6. Phenomenon of Radioactive decay & the Radiations The radioactive decay or transformation involves transformation of the unstable radioactive nucleus to attain a more stable configuration transformations involve reactions of protons and neutrons, sub-atomic particles Because stability of the nucleus predominantly depends on the total number of nucleons (protons and neutrons) as well the ratio of the protons (p) to the neutrons (n) Generally, a proton rich (or neutron deficient) nuclide would transform to reduce the proton content while a neutron rich nuclide would transform vice versa.

7. Modes of Radioactive Decay Alpha decay (α) Radioactive nuclei having too many nucleons (n and p) often undergo alpha decay, in order to achieve nuclear stability. Alpha particle has a mass of 4 units and a charge of +2 units therefore, equivalent to helium+2 ion. Alpha particles from radionuclides have energy ranging from 1.8 to 11.7 MeV But, artificially, rays (He ions) can be accelerated to energies reaching several GeV .

8. Negatron decay (β-): Radioactive nuclei having neutrons in excess than what is needed for a stable configuration mostly undergo negatron or β- decay, in order to achieve nuclear stability Negatrons have the same mass and electrical charge of orbital electrons, but they originate from nucleus at the very instant of decay, when a neutron transforms to a proton. Such a transformation results in increase in atomic number by 1, while the mass does not change significantly. The β- decay phenomenon could be expressed as the following nuclear reaction:

9. Positron decay (β+) Radioactive nuclei having neutrons lesser than what is needed for a stable configuration undergo positron β+ decay in order to achieve stability if adequate energy is available from the nucleus for transformation of a proton to a neutron. results in decrease in atomic number by 1 , while the mass does not change significantly. The β+ decay phenomenon could be expressed as the following nuclear reaction:

10. Electron Capture (EC): Radioactive nuclei having neutrons lesser than what is needed for a stable configuration and which do not have adequate energy available to undergo positron β+ decay , decay by another mode named “ Electron Capture’ , in order to achieve stability In this mode of decay, an orbital electron is captured in the nucleus thus facilitating conversion of a proton to a neutron resulting in a nuclide with decrease in atomic number by 1 . An electron capture reaction can be written as

11. Gamma decay (γ): Gamma rays are electromagnetic rays coming out of nucleus as a result of the difference in nuclear energy levels of the excited and the ground states of the daughter nuclide when a nuclear transmutation takes place. Most radioactive decays are accompanied by γ rays, although it is not essential. Since γ rays carry the energy arising out of the difference in nuclear energy levels, these are often highly energetic , with energy greater than those of X-rays.

12. The penetrating power of each radiation varies considerably according to its nature and its energy. Alpha particles can be stopped within a thickness of a few micrometers to few tens of micrometers of matter, Beta particles require several millimeters to several centimeters of matter for complete attenuation. Gamma rays are the most penetrating and are attenuated in an exponential manner in matter. High density materials such as lead are used to stop the gamma rays a tenfold reduction of energetic gamma rays may require several centimeters of lead

13. Isomeric Transition (IT): When an excited nucleus de-excites by emission of a delayed gamma ray, the daughter nucleus is a nuclear isomer of the parent nuclide and the process is called isomeric transition γ ray emissions are very quick and happen within nanoseconds However, transitions become slow, the excited state of the nuclide is referred to as ‘ metastable ’ state, indicated by the symbol ‘m’ after the atomic number (e.g. 99mTc). Nuclear isomers have same number of protons and same number of neutrons, only that they are arranged in a more stable configuration in the daughter nucleus

14. Application of radiopharmaceuticals Its Application is divided into two major areas diagnostic In imaging, γ-rays emitted from the radioactive isotopes allow the radiopharmaceutical to be traced or their distribution in target tissue imaged non-invasively thus providing functional information of the target tissue or organ therapeutic. the β-ray energy from the radioisotope is delivered to the target tissue partially or completely to destroy the diseased tissue. The diagnostic side is well established, while the therapeutic side of nuclear medicine is evolving

15. Production of Radionuclides The practical method of production of radionuclides for use in, or as radiopharmaceutical preparations are by neutron bombardment of target materials (generally in nuclear reactors); charged particles bombardment of target materials (in accelerators such as cyclotrons); nuclear fission of heavy nuclides of target materials (generally after neutron or particle bombardment); and from a radionuclide generator

16. Labelling Apart from the general labeling requirements, the label on the direct container should state notification that the product is radioactive in nature the name of the preparation and/or its reference the name of the manufacturer an identification number for liquid and gaseous preparations: the total radioactivity in the container, or the radioactive concentration per milliliter at a stated date and stated time, and the volume of liquid in the container for solid preparations (such as freeze-dried preparations): the total radioactivity at a stated date and stated time. for capsules: the radioactivity per capsule at a stated date and time and the number of capsules in the container, and route of administration.

17. The labeling can be adapted in certain cases (e.g. radiopharmaceutical preparations containing short-lived radionuclides ). The label on the outer package states, in addition to those on the direct container: the route of administration the validty period or the expiry date the name and concentration of any added antimicrobial preservative and where applicable, any special storage conditions

18. Storage Store in an airtight container in a place that is sufficiently shielded to protect personnel from expoure to primary or secondary emissions Containers may darken due to irradiation. Such darkening does not necessarily involve deterioration of the preparations. Radiopharmaceutical preparations are intended for use within a short time and the end of the period of validity must be clearly stated. Radiopharmaceuticals intended for parentral use should be stored in such a manner so that pharmaceutical purity of the product is maintained.