Laser Light in Cancer Therapy

1. Laser Light in Cancer Therapy
Prof Amin E Amin
Dean of the Higher Institute of Optics Technology
&
Prof of Medical Physics
Radiation Oncology Department
Faculty of Medicine, Ain Shams University

2. Introduction
This is a preliminary presentation to let us know what is
laser light and what are its uses in cancer therapy.

3. L ight
A mplification by
S timulated
E mission of
R adiation
The Word LASER Is An Acronym For

4. Laser Therapy
❖ Laser light is nonionizing radiation.
❖ Hence, laser therapy is not considered as radiotherapy.

5. • Laser light has the following properties;
• Monochromatic
• Directional
• Coherent
Properties Of Laser

6. Ordinary Vs Laser Light
1. Many wavelengths
2. Multidirectional
3. Incoherent
1. Monochromatic
2. Directional
3. Coherent
Laser light is different from regular light (The light from
the sun or from a light bulb)

7. 7
Monochromatic Light
▪ The light emitted from a laser
is monochromatic, that is, it
is of one color/wavelength
(frequency).
▪ In contrast, ordinary white
light is a combination of many
colors (or wavelengths) of
light.

8. 8
Directional Light
▪ Lasers emit light that is highly directional, that is, laser light is
emitted as a relatively narrow beam in a specific direction.
▪ Ordinary light, such as from a light bulb, is emitted in many
directions away from the source.

9. 9
Coherent Light
▪ The light from a laser is said to be coherent, which means
that the wavelengths of the laser light are in phase in
space and time.
▪ Ordinary light can be a mixture of many wavelengths.

10. 10
Laser Fundamentals
• These three properties of laser light are what can make it
more effective and hazardous than ordinary light.
• Laser light can deposit a lot of energy within a small area.

11. Basic Concepts For A Laser
• Absorption
• Spontaneous Emission
• Stimulated Emission
• Population inversion

12. Absorption
Energy is absorbed by
an atom, the electrons
are excited into vacant
energy shells.
E2
E1

13. Spontaneous Emission
• The atom decays from level 2
to level 1 through the
emission of a photon with the
energy hv = E2-E1.
• It is a completely random
process.
E2
E1

14. Stimulated Emission
Atoms in an upper
energy level can be
triggered or stimulated
in phase by an incoming
photon of a specific
energy.
E2
E1

15. Inverted Population
➢ When a sizable population of electrons resides in upper levels,
this condition is called a "population inversion“.
➢ In order to obtain the coherent light from stimulated emission,
two conditions must be satisfied:
1. The atoms must be excited to the higher state. That is, an inverted
population is needed, one in which more atoms are in the
upper state than in the lower one, so that emission of
photons will dominate over absorption.
Unexcited system
E1
E2
E3
Excited system
E1
E2
E3

16. Metastable State
Metastable state
Photon of energyE2 − E1
E1
Metastable system
E2 E2
2. The higher state must be a metastable state – a state in which the
electrons remain longer than usual so that the transition to the
lower state occurs by stimulated emission rather than
spontaneously.
Stimulated emission
Incident photon
E1Emitted photo
E3 E3

17. Stimulated Emission
❖The stimulated photons have unique properties:
➢In phase with the incident photon
➢Same wavelength as the incident photon
➢Travel in same direction as incident photon

18. Laser Therapy for Cancer Treatment
• Laser light is concentrated so that it makes a very
powerful and precise tool.
• Laser therapy uses light to treat cancer cells.

19. Laser Therapy for Cancer Treatment
• Lasers can cut a very tiny area, less than the width of the finest
thread. They can remove very small cancers without harming
nearby tissue.
• Lasers are used to put heat on tumors to shrink them.
• Lasers are sometimes used with medicines that are activated by
laser light to kill cancer cells.
• Laser beams can be bent by going through tubes for hard-to-reach
places.
• Lasers can be used with microscopes to let healthcare providers
see the site being treated.

20. How Are Lasers Used During Cancer
Surgery?
• Laser surgery is a type of surgery that uses laser beams instead
of tools such as scalpels.
• There are several types of lasers. Each is used to do certain
things during surgery.
• Laser light can be delivered either continuously or as pulses.
• It can be used with fiber optics to treat areas of the body that are
often hard to reach.
• These are some of the lasers used for cancer treatment:

21. Carbon Dioxide (CO2) Lasers
• CO2 lasers can remove a very thin layer of tissue from the
surface of the skin without removing deeper layers.
• The CO2 laser may be used to remove skin cancers and some
precancerous cells.

22. Neodymium:Yttrium-Aluminum-Garnet
(Nd:yag) Lasers
• Nd:YAG lasers can get deeper into tissue.
• They can cause blood to clot quickly.
• The laser light can be carried through optical fibers to reach
internal parts of the body.
• For example, the Nd:YAG laser can be used to treat throat
cancer.

23. Laser-Induced Interstitial Thermotherapy
(LITT)
• LITT uses lasers to heat certain parts of the body.
• The lasers are directed to areas within body tissues that are
near a tumor.
• The heat from the laser raises the temperature of the tumor.
• That shrinks, damages, or kills the cancer cells.

24. Argon Lasers
• Argon lasers pass only through outer layers of tissue such as
skin.
• Argon lasers can be used to treat skin problems or in eye
surgery.
• Photodynamic therapy (PDT) uses argon laser light to
activate chemicals in the cancer cells.

25. What Is Photodynamic Therapy?
• PDT can destroy just cancer cells and leave most healthy cells alone.
• It is used to treat certain cancer tumors.
• PDT is also called photoradiation therapy or photochemotherapy.
• It uses a combination of a light source and a photosensitizing
medicine activated by light.
• The medicine is often injected into the blood. It collects more in
cancer cells than in normal cells.
• When the laser's light is focused directly on the tumor, the cancer
cells absorb the light.
• A chemical reaction occurs that kills the cancer cells.

26. What Is Photodynamic Therapy?
• The FDA has approved the use of PDT for certain types of
cancer that are found just under the skin or in the lining of
certain organs.
• This is because PDT can only pass through a limited tissue
depth.
• Cancer types that may be treated with PDT are cancer of the
esophagus, non-small cell lung cancer, and a precancerous skin
lesion (actinic keratosis).
• PDT may have fewer side effects than other treatments. It can
also be used again and again at the same site if needed.

27. What Is Photodynamic Therapy?
• Major side effects of PDT are sensitivity to light and swelling at
the treatment site.
• Both the eyes and skin are affected by light sensitivity.
• This may last up to 3 months after treatment.
• Swelling can cause pain.
• The swelling also may make it hard to swallow or breathe,
depending on the location of treatment.

28. What Is Photodynamic Therapy?
• Other side effects may occur.
• They depend on the area being treated.
• A small amount of damage may also occur in healthy tissue.
• As each person's health profile and diagnosis are different, so is his
or her reaction to treatment.
• Side effects may be severe, mild, or absent.

29. What Cancers May Be Treated With
Laser Therapy?
• Lasers are used in surgery for certain types of cancer because these
often have a special requirement that only lasers can meet. For
instance, the laser can reach a hard to treat area, apply heat, or cut
only a very small area: They may be used for:
• Vocal cords, Esophagus, Cervix, Skin, Lung, Vagina, Vulva

30. What Cancers May Be Treated With
Laser Therapy?
• Laser surgery is also used for palliative surgery in people with
cancer.
• Palliative surgery can help the person feel better and more
comfortable or function better even though the surgery may not
treat the cancer.
• An example of this type of surgery may involve removing a growth
that is making it hard for a person to eat.

31. Positive Aspects Of Laser Treatment
• Lasers are more precise and exact than blades (scalpels). For
instance, the tissue near a laser cut (incision) is not affected
since there is little contact with skin or other tissue.
• The heat produced by lasers helps clean (sterilize) the edges
of the body tissue that it’s cutting, reducing the risk of
infection.
• Since laser heat seals blood vessels, there is less bleeding,
swelling, pain, or scarring.

32. Positive Aspects Of Laser Treatment
• Operating time may be shorter.
• Laser surgery may mean less cutting and damage to healthy
tissues (it can be less invasive). For example, with fiber
optics, laser light can be directed to parts of the body through
very small cuts (incisions) without having to make a large
incision.
• More procedures may be done in outpatient settings.
• Healing time is often shorter.

33. Limitations Of Laser Treatment
• Not many doctors and nurses are trained to use lasers.
• Laser equipment costs a lot of money and is bulky compared with the
usual surgical tools used. But advances in technology are slowly
helping reduce their cost and size.
• Strict safety precautions must be followed in the operating room when
lasers are used. For example, the entire surgical team and the patient
must wear eye protection.
• The effects of some laser treatments may not last long, so they might
need to be repeated. And sometimes the laser cannot remove all of the
tumor in one treatment, so treatments may need to be repeated.