introduction to radiopharmaceuticals

4. What is Radiopharmaceuticals?
A radiopharmaceutical is a
radioactive compound used for the
diagnosis and therapeutic
treatment of human diseases.
A radiopharmaceutical has two
components:
a radionuclide and a
pharmaceutical.

5. Introduction
In designing a radiopharmaceutical, a
pharmaceutical is first chosen on the basis
of its preferential localization in a given
organ or its participation in the physiologic
function of the organ.
Then a suitable radionuclide is tagged onto
the chosen pharmaceutical such that after
administration of the radiopharmaceutical,
radiations emitted from it are detected by a
radiation detector.

6. Introduction
Isotopes of an atom have the same
number of protons, but a different
number of neutrons.
Radioisotopes & Radionuclides:
unstable isotopes which are
distinguishable by radioactive
transformation.

7. Radioactivity: the process in which an
unstable isotope undergoes changes
until a stable state is reached . When
the atomic nucleus undergoes
spontaneous transformation, called
radioactive decay, radiation is emitted
.(alpha particles, beta particles and
gamma rays).

8. Introduction
Radiation refers to particles or waves
coming from the nucleus of the atom
(radioisotope or radionuclide) through
which the atom attempts to attain a
more stable configuration.

9. Important parameters
+ Radioactive decay is the process in which
an unstable atomic nucleus spontaneously
loses energy by emitting ionizing particles
and radiation.
+Physical half-life is the period of time
required to reduce the radioactivity level of
a substance to exactly one half its original
value due solely to radioactive decay.
biological half-life the time required for a
living organism to eliminate one-half of a
radioactive substance which has been
introduced into it.

10. Effective half life
The time required for a radioactive
element in an animal body to be
diminished by 50% as a result of
radioactive decay and biologic
elimination.
Te = ( Tp X Tb) ( Tp + Tb )isotope T(ph) T(b) T(e)
3H 4500 12 12
99mTc 0.25 1 0.2
235U 26000000000
0
15 15
226Ra 580000 16000 15000

11. Ideal radiopharmaceutical
properties
 Short half-life isotope(Ideally 1.5 times the
duration of the diagnostic procedure.)
 Energy of Gamma Rays: (Ideal: 100-250
keV)
 Pure gamma emitter
 Target to Non target Ratio
 Localization only in tissue desired
 Easy preparation
 Economy price

12. radioactive decay types:
When an unstable nucleus decays, It may
give out:
1- Alpha particle decay
2- Beta particle decay
3- Gamma ray

13. Penetrating power
Alpha particles may be
completely stopped by
a sheet of paper, beta
particles by aluminum
shielding. Gamma rays
can only be reduced by
much more substantial
mass, such as a very
thick layer of lead.

14. 1- Alpha particle decay
Alpha particles are made of 2 protons and 2
neutrons.
This means that when a nucleus emits an
alpha particle, its atomic number decreases
by 2 and its atomic mass decreases by 4.
Alpha particles are relatively slow and
heavy and have a low penetrating power .
Because they have a large charge, alpha
particles ionize other atoms strongly.

15. 2- Beta particle decay
Beta particles have a charge of minus 1.
This means that beta particles are the same
as an electron.
This means the atomic mass is unchanged
the atomic number increases or decreases
by 1.
They are fast, and light.
Beta particles have a medium penetrating
power.
Beta particles ionize atoms that they pass,
but not as strongly as alpha particles do.

16. 3- Gamma ray
Gamma rays are waves, not particles.
This means that they have no mass and no
charge.
Gamma rays have a high penetrating power
Gamma rays do not directly ionize other
atoms, although they may cause atoms to
emit other particles which will then cause
ionization.

17. Radioactive materials
1- Natural radioactivity:
Nuclear reactions occur spontaneously
2- Artificial radioactivity:
The property of radioactivity produced
by particle bombardment or
electromagnetic irradiation. All
radionuclides commonly administered
to patients in nuclear medicine are
artificially produced

18. Types of artificial
radioactivation:
A- Charged-particle reactions(cyclotron)
B- Photon-induced reactions(nuclear
reactor)
C- Neutron-induced reactions(radionuclide
generator)

19. Neutron-induced reactions
It is the bombardment of a
nonradioactive target nucleus with a
source of thermal neutrons in a device
called a Radionuclide Generator.

20. Radionuclide Generator
 Radionuclide generators contain a
parent radionuclide that decays to
produce a radioactive daughter. The
parent is usually produced in
specialized nuclear reactor’s.

22. Example:
technetium-99m, obtained from a
generator constructed of molybdenum-99
absorbed to an alumina column.
Parent: 99Mo as molybdate
Half-life: 66 hr.
daughter:
half-life:6hr

23. Application of
radiopharmaceuticals
1- Treatment of disease:
They are radiolabeled molecules designed to
deliver therapeutic doses of ionizing
radiation to specific diseased sites.
2- As an aid in the diagnosis of disease:
The radiopharmaceutical accumulated in an
organ of interest emit gamma radiation
which are used for imaging of the organs
with the help of an external imaging device

24. Good
luck!