Radiation can be defined as any collection of elementary particles that have sufficient energy to interact with and transfer some of their energy to objects or materials that intercept their path.
The
process of removing an orbital electron from an atom is called ionization.
Radioactivity
generates radiation by emitting particles. Radioactive materials outside the
body are called external emitters,
and radioactive materials located within the body are called internal emitters.
Types of Ionizing Radiations:
Radioactive
nuclei can emit several kinds of particles, but there are three primary types: alpha particles (α), beta particles (β),
and photons that are either x rays or gamma rays (γ). Several properties
distinguish those particles from one another. One is an electric charge; alpha
particles are emitted with a positive charge of 2, beta particles are emitted
with either 1 negative charge (electron) or 1 positive charge (positron), and x
rays and gamma rays have no charge and are thus neutral.
Another important property is the penetration of the particles through matter. Alpha
particles lose energy rapidly and stop in a very short distance. Most travel no
more than 3-5 centimetres in air and only about 30-50 microns in water or
tissue. They cannot penetrate clothes or skin. Alpha particles must be emitted
very close to biologic targets to produce an effect. External alpha emitters, therefore, are generally not considered to pose a health hazard. However,
radioactive materials can enter the body through inhalation, ingestion, or
transfer through cuts and wounds. Some of this radioactive material passes
through the body and is eliminated, and some remains in tissues that might
contain radiosensitive cells. The distribution of the radioactive material in
the body depends on the chemistry of the radioactive element. For example,
radium has chemical properties similar to those of calcium, and the
alpha-particle emitter radium-226 (226Ra) will accumulate with calcium in bone.
Beta
particles are electrons that lose energy rather slowly when passing through
materials. A high-energy beta particle can travel several centimetres through
water and tissue. Lower-energy beta particles travel some fraction of that
distance. External emission of low-energy beta particles, as in the decay of
tritium, which is an isotope of hydrogen (3H), or carbon-14 (14C) is not
considered a health hazard, whereas external emission of high-energy beta
particles from strontium-90 (90Sr) reach some regions of the body that are
sensitive to radiation. As in the case of alpha-emitters, the distribution of
internal beta-emitters depends on the chemistry of the radioactive element.
Strontium has chemistry similar to that of calcium, and 90Sr will accumulate in the bone. Most of the iodine in the body that is not excreted will accumulate in
the thyroid. Beta particles from 131I can originate in the thyroid and deposit
most of their energy there.
Photons
can be very penetrating. High-energy x rays and gamma rays travel many meters
in the air and through many centimetres of concrete, iron, and tissue. Thus,
external gamma rays can penetrate and deposit energy throughout the body. The
distribution of internal gamma-emitters depends on the chemistry of the
radioactive element. Internally emitted gamma rays can deposit energy in the tissue
of residence or neighbouring tissues. For example, caesium-137 (137Cs) deposited
in soft tissues, and the entire body is exposed uniformly to gamma rays.
Radiation Biology:
When
people are exposed to ionizing radiation from sources outside or inside the body,
the radiation may interact with molecules in cells in their path. Some ionizing
radiation can travel through a few or several layers of cells (beta-particle
radiation) or through many cell layers into and through tissues deep within the
body (x and gamma radiation), whereas alpha-particle radiation has short paths
or tracks.
The rate at which radiation loses energy along its tracks is referred to as linear
energy transfer (LET) and depends on its track length. Thus, beta-particle
radiation and the electrons associated with x and gamma rays, which are
sparsely ionizing, are described as low-LET radiation, and alpha-particle
radiation, which is densely ionizing, as high-LET radiation.
This
can cause some side effects, such as:
- sore, red skin
- feeling tired most of the time
- hair loss in the area being treated
- feeling sick
- losing your appetite
- a sore mouth
- diarrhoea
Radiotherapy:
Radiation is one of the most common treatments for cancer. Other names for radiation treatment are radiation therapy, radiotherapy, irradiation, and x-ray therapy.
Radiation therapy uses high-energy particles or
waves, such as x-rays, gamma rays, electron beams, or protons, to destroy or
damage cancer cells.
Cells normally grow and divide to form new
cells. But cancer cells grow and divide faster than most normal cells. Radiation
works by making small breaks in the DNA inside cells. These breaks keep cancer
cells from growing and dividing and cause them to die. Nearby
normal cells can also be affected by radiation, but most recover and go back to
working the way they should.
While chemotherapy and
other treatments that are taken by mouth or injection usually expose the whole
body to cancer-fighting drugs, radiation therapy is usually a local treatment.
This means it’s usually aimed at and affects only the part of the body needing
treatment. Radiation treatments are planned so that they damage cancer cells
with as little harm as possible to nearby healthy cells.
Radiotherapy
can be suggested for two different purposes:-
- Palliative care as care that affords relief, but not cures.
- Curative care, on the other hand, is defined as care that tends to overcome disease, and promote recovery.
Goals of radiation therapy:
- To cure or shrink early-stage cancer
- To stop cancer from coming back (recurring) somewhere else
- To treat symptoms caused by advanced cancer
- To treat cancer that has returned (recurred)
Radiation
therapy can be given in 3 ways:
External radiation (or external beam radiation):
a beam of radiation is directed into the body.
This may also be called x-ray therapy, 3D conformal radiation, intensity-modulated radiation therapy (IMRT), cobalt, photon, or proton therapy. External beam radiation therapy is usually
conducted using a Linear Accelerator
— a machine that directs high-energy beams of radiation into your body.
Internal radiation:
a
source of radioactivity is placed inside the body, near the tumour. This is
called brachytherapy or implant therapy.
Systemic radiation:
Radioactive drugs given by mouth or put into a
vein are used to treat certain types of cancer. These drugs then travel
throughout the body.
The units of absorbed dose are measured in gray (Gy) in the SI Units.
Dosimetry:
Dosimetry
is the process of determining the effective dose received by persons exposed to
ionizing radiation. The most accurate way to determine dose to an individual is
to make measurements with a dosimeter assigned to each person. That is required
today for radiation workers that might be exposed during routine occupational
activities. Area monitors measure external radiation or radioactivity suspended
in the air at specific locations. No dosimeter can directly measure the dose to
the lung from the inhalation of radioactive materials, so area monitors are the
principal instruments used for measuring and controlling internal exposure in
underground mines.
👉 Please Watch Our Radiotherapy Videos (Part 1 & Part 2) from Our YouTube Channel Below:-
Website References:
- https://www.cancer.org/treatment/treatments-and-side-effects/treatment types/radiation/basics.html
- https://www.oncolink.org/cancer-treatment/radiation/introduction-to-radiation-therapy/radiation-therapy-the-basics
- https://emedicine.medscape.com/article/846797-overview
- https://www.cancer.net/navigating-cancer-care/how-cancer-treated/radiation-therapy/understanding-radiation-therapy
- https://www.cancer.gov/about-cancer/treatment/types/radiation-therapy
- https://www.nap.edu/read/11279/chapter/5#54
YouTube Reference:
- https://www.youtube.com/watch?v=ZgAi4wQLqZ0
- https://www.youtube.com/watch?v=Zw0pHT47AAU
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