principle,mechanism,treatments,advantages&limitations,results :)

1. PHOTO DYNAMIC THERAPY
-LALITHA KAVYA

2. INTRODUCTION
 It form of phototherapy using nontoxic light-sensitive
compounds that are exposed selectively to light,
whereupon they become toxic to targeted malignant
and other diseased cells.
 PDT has proven ability to kill microbial cells including
bacteria, fungi and viruses.
 In PDT, the usage of the right wavelength of the
light,the correct light-sensitive compounds which are
at the same time highly effective to treat the
targetted tissue is an important step that needs to be
followed.

3. INTRODUCTION-WHY PDT?
• It is the best alternative for extensive surgery.
• It does not take long time.
• It is minimally invasive therefore it saves recovery
time .(minimal recovery period).
• It is minimally toxic.
• Less scarring (when compared to the extensive
surgery)
• Patient suffering due to pain post PDT is very
minimal.
• Preparation time is also minimal.

4. KEY COMPONENTS
• PDT has three essential components:-
1. LIGHT SOURCE
2. PHOTO SENSITIZER
3. MOLECULAR OXYGEN
• The obvious requirement for the action of PDT is a
TARGET TISSUE.

5. KEY COMPONENTS
• PHOTO SENSITISER is a substance which absorbs the
wave length of the light focussed on it and inhibits photo
reaction to other normal cells surrounding the tissue.
• Use of visible and near infra red light with a photo
sensitiser to treat the diseased tissue.
• The wavelength of the light source needs to be
appropriate for exciting the photosensitizer to produce
REACTIVE OXYGEN SPECIES. combination of these three
components leads to the chemical destruction of any
tissues that have been exposed to this light.

6. PRINCIPLE
A photo sensitiser is administered to the
Targetted tissue (for example a tumor).Light is
then allowed to concentrate on this targetted
tissue which is absorbed by the photo sensitiser
and this causes the generation of reactive
oxygen species.
• Example of photo sensitisers:-
• PORFIMER SODIUM,AMINOLEVULINIC ACID

7. PDT-LASER

8. MECHANISM OF ACTION
• The photosensitizer is excited from a ground singlet state
to an excited singlet state. It then undergoes intersystem
crossing to a longer-lived excited triplet state.
• One of the few chemical species present with a ground
triplet state is “MOLECULAR OXYGEN”. When the
photosensitizer and an oxygen molecule are in proximity,
an energy transfer can take place that allows the
photosensitizer to relax to its ground singlet state, and
create an excited singlet state oxygen molecule.
• Singlet oxygen is a very aggressive chemical species and
will very rapidly react with any nearby biomolecules.

9. MECHANISM
• Ultimately, these destructive reactions will kill
cells through apoptosis or necrosis.
• PDT can be considered a form of
targeted ’singlet oxygen chemotherapy’where
the targeting is achieved with the combination
of the photosensitizer and intense light.

10. MECHANISM
• Photosensitizer(p.s) Oxygen
Ground triplet state
Ground singlet state EXCITED SINGLET STATE
Excited singlet state
Excited triplet state
GROUND SINGLET STATE

11. INCIDENT LIGHT
Oxygen (excited
singlet state)
P.S
( ground singlet
state)

12. TREATMENT-PORFIMER SODIUM
• First, the porfimer sodium(photo sensitiser) is
administered intravenously into the cancer patient.
• It travels through the bloodstream and is absorbed by
every cell in the body (both the normal and the
cancerous cells).
• The normal cells get rid of porfimer sodium in a couple of
days.But a lot of the drug stays in the cancer and normal
skin cells.
• Porfimer sodium is activated or turned on by light
(visible/infra red) after 2-3 days of administering it into
the body.
• This gives normal cells to get rid of the drug.

13. TREATMENT-PORFIMER SODIUM
• The doctor directs a laser light at the area of cancer
cells through a thin fiber optic glass strand.
• LASER used is a low power light so it does not burn.It
gives minimal or no pain.
• Depending on the size of the tumor,the light is given
from 5-40 minutes.
• Any dead tissue left in the treated are is removed
after 4-5 days.
• The treatment can be repeated.

14. TREATMENT-AMINOLEVULINIC ACID
• Aminolevulinic acid is a topical drug applied directly
on skin to treat actinic keratosis (a pre malignant
condition).
• It is a solution that is applied directly on face or scalp
(unlike porfimer sodium,this does not reach other
body parts).
• After 14-15 hours of application of the drug,doctor
passes BLUE LIGHT onto the area for 15 minutes.
• The area may become red,scaly and crusty for almost
4 weeks before healing.
• If the lesion does not go away completely,it can be
treated again after 8 weeks.

15. ACTINIC KERATOSIS

16. PDT-ADVANTAGES AND LIMITATIONS
• PDT is considered to be both minimally invasive and
minimally toxic, these advantages alone make PDT
an attractive alternative.
• Compared to radiotherapy, chemotherapy and
surgical operation for the treatment of cancers, PDT
is in almost all cases a much cheaper alternative.
• Furthermore, post-operative recovery after PDT is
typically hours or days rather than weeks.

17. PDT-ADVANTAGES AND LIMITATIONS
• It cannot be used to treat all types of cancers.
• The photosensitisers in some cases,might be
harmful as the normal cells feed up on it and
the patient’s eyes and skin might become very photo
sensitive for about 30 days.
• The skin might burn or blister or swell if exposed to
direct sunlight.
• The availability of PDT is scanty as research is still
going on about its applications and suitability in
various geographical areas.

18. PDT-ITS RESULTS

19. PDT-ITS RESULTS

20. CONCLUSION
• Photodynamic therapy is one of the best
techniques to cure many ailments which normal
clinical techniques are inefficient in solving .
• In a few years its popularity and also availability
to the common man is foreseen.
• It comes across as a very safe and potential way
to solve cases of cancer, skin ailments etc.
• The awareness of photodynamic therapy is
increasing rapidly and soon it will attain a
position where it will be considered a “BOON” to
the medical and scientific fields…

21. THANK YOU FOR YOUR TIME AND
PATIENCE… 