A presentation that briefly explains the physics behind radiotherapy as a medical technology.

1. Ashley Raiteri

2. What energy does
radiotherapy use?
Radiation therapy (US and Canada) is also known as radiation
oncology, irradiation or radiotherapy (UK and Australia).
Radiation therapy uses
electromagnetic radiation, such as x-
rays, gamma rays, electron beams or
protons to kill or damage cancer cells
to stop/slow them from growing or
multiplying.
• Radiotherapy can take place
before, during or after
treatment and in conjunction
with other treatments such as
chemotherapy or surgery.
• About 50% of all cancer
patients receive some form of
radiation therapy during the
course of their treatment.
PET-CT scan used
to pinpoint area of
cancerous tissue in
the brain

3. How is the radiation
generated?
• Radiotherapy is completed internally
(brachytherapy) or externally
Brachytherapy
• Brachytherapy can be employed alone
or with external radiotherapy as well
• The radiation is received through a
source placed next to/in the treatment
area or a small radioactive rod, a
“seed”, is inserted into the treatment
area
NOTE: As much as a complex geometric
localisation program is used to only target
cancerous tissue, healthy tissue is still often
damaged as well: however, due to the
cancer cells being weaker to radiation,
healthy tissue can usually recover from the
prescribed dose.
External Radiotherapy
• External radiotherapy is the most
common form of radiotherapy
• The beam (either photons or
charged particles) that generates
ionization (and through that
irradiation) is generated by a
linear particle accelerator(LINAC
for short)
• The LINAC both generate electrons
and accelerate them to generate a
high-energy beam
• The high-energy beam penetrates
the tissue of the patient to ionize
the cancer cells and damage them
“Seeds”

4. How does the energy
interact with the tissue?
• When the energy reaches the
tissue, the interaction that
occurs is ionization
(acquirement of positive or
negative charge)
• This ionization happens
either directly to the cancer
DNA or indirectly by the
ionization of water (the
ionized water produces free
radicals, which then damage
the DNA)

5. How does the tissue
receive the energy?
• The cancerous tissue receives
the energy in the form of
radiation, where it damages
the DNA of the cancer cells.
• The radiation is able to
primarily destroy the
cancerous tissue over healthy
tissue because the single-
stranded DNA of cancer is
vulnerable to radiation,
whereas the double-stranded
DNA of healthy tissue is
usually able to recover from
irradiation.

6. Advantages of radiotherapy
1. The localisation of
radiation allows for the
significant lessening of
damage to healthy tissue
2. Radiotherapy is useful
during before and after as
well as during treatment
because it can effectively
stop cancer and tumours
3. Patients claim that the
daily treatment does not
impede significantly on
their daily schedule
4. Radiotherapy can still be
given when surgery is
considered unsuitable or
unfit
5. The radiotherapy itself is
relatively painless

7. Possible side affects of
radiotherapy
• Side effects of radiotherapy can be
acute or chronic, which means that
they will occur during the
treatment or some time (as long as
years) after the treatment,
respectively
• Side effects depend on the specific
area that is being treated, dosage,
general medical condition and
other treatments that are being
received at the time
Acute Side Effects
• Skin irritation
• Damage at regions exposed to
radiation (eg. Hair loss)
• Fatigue
• Nausea
Chronic Side Effects
• Fibrosis (restricted movement at
affected area)
• Bowel damage -> diarrhoea and
bleeding
• Memory loss
• Infertility
• Rarely, a second cancer caused by the
radiation exposure
Other disadvantages:
• Radiotherapy machines take up large
amounts of space and are not mobile –
large distances may have to be
travelled to receive treatment
• Radiotherapy machines must be set up
in rooms that contain radiation
• When used alone, radiotherapy cannot
do much to help cancer that has
already metastasized (spread
throughout the body)

8. Hair loss is common when
radiotherapy treatment is
made on the head or neck
Vein irritation 3 years after
radiotherapy

9. http://www.youtube.com/watch?v=QsfQLyuAbLg
LINAC demonstration

10. http://www.youtube.com/watch?v=S-WIQhM43ng 1/5
http://www.youtube.com/watch?v=lZ9cGVaxOes 2/5
Radiotherapy Interview