Radio-Pharmaceuticals
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
Radio-pharmaceuticals
• 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 of Radio-Pharmaceuticals
• 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
FAQs
1. Are radio-pharmaceuticals safe for patients?
Radio-pharmaceuticals are generally safe when administered in controlled medical settings. The benefits of diagnosis and treatment often outweigh the minimal radiation exposure.
2. How are radio-pharmaceuticals produced?
Radio-pharmaceuticals are typically produced by incorporating radioisotopes into pharmaceutical compounds in specialized facilities, ensuring stringent quality control.
3. Are there any side effects associated with radio-pharmaceuticals?
Side effects are typically mild and transient. They may include minor allergic reactions or temporary discomfort at the injection site. The benefits of accurate diagnosis and targeted therapy generally outweigh these potential side effects.
4. Which medical conditions can be treated with radio-pharmaceuticals?
Radio-pharmaceuticals are used to treat various conditions, with a primary focus on cancer. However, their applications continue to expand, encompassing other diseases like hyperthyroidism.
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