Radio-Pharmaceuticals
Contents
• Radioactivity
• Alpha radiation
• Beta rays
• Gamma rays
• Geiger-Muller counter method
• Scintillation counter method
• Biological Effects of Radiation
• Storage of Radio Active Material
• Handling Radio Active Materials
• Application of Radiopharmaceuticals
Learning
Objectives
At the end of this
lecture, student will be able to
• Explain the basic concept of radio activity
• Differentiate alpha,beta and gamma rays
• Describe the instruments used to measure radio activity
• Explain the principle involved in the working of
instruments used to measure radio activity
• Choose a method for handling and storing radioactive
material
• Indicate the clinical application of radiopharmaceuticals
Radioactivity
• The spontaneous emission of radiations by atomic nuclei
resulting in their integration is called natural radioactivity
Types
• Alpha rays
• Beta rays
• Gamma rays
Properties
of Radiations
|
Alpha Rays |
Beta Rays |
Gamma Rays |
|
Helium atoms with a mass of four a.m.u. and with two positive charge |
Highly energetic electrons |
Neutral |
|
Penetrating power is less |
100 times more than alpha rays |
Penetrating power is immensely high |
|
Highest ionizing power |
100 time less than alpha rays |
No ionizing power |
Key Words
• Z = The Atomic Number.
• It’s the Number of Protons in the nucleus of an Atom.
• Nucleus: It’s where the Protons and Neutrons are located
in an Atom.
• Protons: Positively Charged Particles in the Nucleus of
the atom. Mass = (approx) 1 AMU
• Neutrons: Neutrally charged particles in the nucleus of an
atom Mass = (approx) 1 AMU
• Mass Number of an atom: Number of Protons + Number of Neutrons
in the nucleus of an atom
Sources of
Radioactivity
• Naturally Occurring
Sources:
– Radon from the decay of Uranium and Thorium
– Potassium -40 – found in minerals and in plants
– Carbon 14 – Found in Plants and Animal tissue
• Manmade Sources:
– Medical use of Radioactive Isotopes
– Certain Consumer products –(eg Smoke detectors)
– Fallout from nuclear testing
– Emissions from Nuclear Power plants
Stable
Isotopes
• The nucleus of each atom contains protons and neutrons.
• While the number of protons defines the element (e.g.,
hydrogen, carbon, etc.)
• The sum of the protons and neutrons gives the atomic mass,
the number of neutrons defines the isotope of that element.
• For example, most carbon (≈ 99 %) has 6 protons and 6
neutrons and is written as 12C to reflect its atomic mass.
• However, about 1 % of the carbon in the Earth’s biosphere
has 6 protons and 7 neutrons (13C) forming the heavy stable isotope
of this important element.
• Stable isotopes do not decay into other elements. In
contrast, radioactive isotopes (e.g., 14C) are unstable and will
decay into other elements
Radioactive
Decay
• Process by which an unstable atomic nucleus loses energy
by emitting radiation
Alpha particle
Beta particle
Gamma particle
Half Life
• The time it takes for half the R.A. nuclei to decay is
called the half life
• The time taken for the radioactivity to half is the same.
• Different R.A. substances have different half-lives.
Example:
Units of
Radioactivity
• Physical Units
• Roentgen (R)
• Curie (Ci)
• Biological units
• Gray (Gy)
• Rad (rad)
• Relative Biological Effectiveness (RBE)
Detection
and Measurement of Radio Activity
• Geiger-Muller counter method
• Scintillation counter method
• Ionization chamber method
• Cloud chamber method
Geiger-Muller
Counter Method
Argon gas is filled in the tube at reduced pressure of 0.1
atmospheres.
A potential difference of about 1000 volts is applied across
the two electrodes.
• Argon gas is ionised wherever any alpha or beta particles
enters in the tube through the mica window
• The positively charged argon ions are attracted to the
cathode
• The negatively charged electrons to the anode
• Thus an electrical impulse flows between the electrodes
whenever one alpha or beta particle enters the tube
• The electrical pulses are counted in an automatic counter
• The intensity of the radioactivity of any radioactive
material can be found out by finding the number of pulses per minute
Scintillation
Counter Method
• Scintillation means a flash of light
• Phosphor, photomultiplier tube
• In conjunction with a high voltage supply, an amplifier, a
pulse height discriminator and a scalar
• Charged particles or gamma radiations from radioactive
source cause phosphor to emit scintillations (flashes of light)
• Which are made to fall on light sensitive photomultiplier
tube which detects and amplifies and converts it into electrical impulses
• This impulse recorded directly by means of scalar
Scintillators
• Inorganic scintillators
• Alkali halide (NaI, CsIetc)
• Organic scintillators
• Anthracene
Biological
Effects of Radiation
Delayed
Effects of Radiation
• The hair greys quickly
• Premature ageing
• Cancer of skin, lung cancer, leukaemia
• Sterility
• Chromosomal damage
• Mutations
Storage of
Radio Active Material
• Stored in an area not frequently visited by people
• Thick glass provides sufficient shielding
• Protect from gamma radiations, lead shielding has to be
used
• The storage area must be regularly checked for the
radioactivity
• Radioactive materials have to be stored in suitable
labelled containers, shielded by lead bricks and preferably in a remote corner
Handling
Radio Active Materials
• Carried in trays having absorbent tissue paper
• Rubber gloves have to be used
• Pipettes operated by mouth should never be employed
• One should not touch radioactive emitter with hand
• It should be handled by means of forceps or suitable
instruments
• Smoking, eating and drinking activities should not be done
• Sufficient protective clothing or shielding
• Areas should be monitored (tested for radioactivity
regularly)
Pharmaceutical
application of radioisotopes
• Radioisotopes in therapeutics
• Radio isotopes in Diagnosis
• Research
• Sterilization
Radiopharmaceuticals
• These are pharmaceutical preparations having a radioactive
isotope
• Used internally
• These are prepared by Scientists at the Bhabha atomic
research Centre (BARC)
• Supplied to approved hospitals and approved laboratories
• E.g.. Sodium radio iodide injection
• sodium iodide-I131capsules
• I P does not include any radioactive pharmaceutical
preparation
Application
of Radiopharmaceuticals
Treatment of disease
• They are radio labeled molecules designed to deliver therapeutic
dose so ionizing radiation to specific diseased sites
As an aid in the
diagnosis of disease
• The radio pharmaceutical accumulated in an organ of inter estimate
gamma radiation which are used for imaging of the organs with the help of a next
Ernal imaging device called gamma camera
Clinical
Application
• Calcium (Ca-44 and Ca-45)-used to study bone structure and
in the treatment of carcinoma of bone
• Cyanocobalamine (Co-57)-in the diagnosis of pernicious
anaemia
• Gold (Au-198) solution –neoplasticsuppressant, used for
the estimation of reticuloendothelial activity
• Hydrogen (H-2 an H-3) –determine total body water
• Iron (Fe-59) –investigation of iron metabolism and to
measure red cell life span
• Sodium (Na-22 and Na-24) –used in the estimation of extra
cellular fluid
• Iodine (I-131) –used in the study of functioning of
thyroid gland
Opaque
Contrast Media
• Radio opaque substances are chemical compounds
• Contains elements of high atomic number
• Will stop the passage of X-rays hence appear opaque on
X-ray examination
• Such compounds and their preparations are known as X-ray contrast
media
• Diagnostic aids in radiology
Barium
sulphate suspension
• Barium meal or shadow meal
• Dry mixture of barium sulphate having suitable colouring flavouring,
preservatives and suspending or dispersing agents
• Composition:
Barium sulphate1000g
Saccharin sodium0.25g
Vanillin0.10g
• Preparation: It is prepared by mixing saccharin and
vanillin with barium sulphate and is given to the patient immediately
• Use: Diagnostic aid
Summary
• The spontaneous emission of radiations by atomic nuclei
resulting in their integration is called natural radioactivity
• Alpha rays, beta rays and gamma radiations are the
radiations
• Alpha radiations are nuclei of helium atoms with a mass of
four a.m.u. and with two positive charges
• Their penetrating power is less and has got highest
ionising power
• In G M counter Argon gas is ionised wherever any alpha or
beta particles enters in the tube through the mica window
• Cationsand anions are attracted to the respective
electrodes
• Electrical pulses are counted in an automatic counter
• Scintillation counter consists of phosphor,
photomultiplier tube, high voltage supply, an amplifier, a pulse height
discriminator and a scalar
• Charged particles or gamma radiations from radioactive
source cause phosphor to emit scintillations
• Radioactive materials are stored in an area not frequently
visited by people
• Lead shielding has to be used to protect from gamma
radiations
• One should not touch radioactive emitter with hand
• Sufficient protective clothing or shielding are required
• Radio pharmaceuticals are pharmaceutical preparations
having a radioactive isotope
• E.g.. Sodium radio iodide injection, sodium
iodide-I131capsules etc
• Radio pharmaceuticals are used in the treatment of diseases,
as an aid in the in the diagnosis of disease